Phase-locked loops. [in analog and digital circuits communication system

NASA Technical Reports Server (NTRS)

Gupta, S. C.

1975-01-01

An attempt to systematically outline the work done in the area of phase-locked loops which are now used in modern communication system design is presented. The analog phase-locked loops are well documented in several books but discrete, analog-digital, and digital phase-locked loop work is scattered. Apart from discussing the various analysis, design, and application aspects of phase-locked loops, a number of references are given in the bibliography.

Asymmetric dual-loop feedback to suppress spurious tones and reduce timing jitter in self-mode-locked quantum-dash lasers emitting at 155 μm

NASA Astrophysics Data System (ADS)

Asghar, Haroon; McInerney, John G.

2017-09-01

We demonstrate an asymmetric dual-loop feedback scheme to suppress external cavity side-modes induced in self-mode-locked quantum-dash lasers with conventional single and dual-loop feedback. In this letter, we achieved optimal suppression of spurious tones by optimizing the length of second delay time. We observed that asymmetric dual-loop feedback, with large (~8x) disparity in cavity lengths, eliminates all external-cavity side-modes and produces flat RF spectra close to the main peak with low timing jitter compared to single-loop feedback. Significant reduction in RF linewidth and reduced timing jitter was also observed as a function of increased second feedback delay time. The experimental results based on this feedback configuration validate predictions of recently published numerical simulations. This interesting asymmetric dual-loop feedback scheme provides simplest, efficient and cost effective stabilization of side-band free optoelectronic oscillators based on mode-locked lasers.

Phase-locked Optical Signal Recovery

DTIC Science & Technology

2009-01-01

detection . However, implementing an optical phase lock loop ( OPLL ) to generate the synchronised carrier for the homodyne technique requires... Loop (OIPLL) in which a narrow bandwidth optical phase lock loop ( OPLL ) is used to control the free -running frequency of an optically injection...receiver uses an Optical Injection Phase Lock Loop (OIPLL) for carrier recovery,

Phase-locked Optical Signal Recovery

DTIC Science & Technology

2009-01-01

detection . However, implementing an optical phase lock loop ( OPLL ) to generate the synchronised carrier for the homodyne technique requires... Loop (OIPLL) in which a narrow bandwidth optical phase lock loop ( OPLL ) is used to control the free -running frequency of an optically injection...The receiver uses an Optical Injection Phase Lock Loop (OIPLL) for carrier

Phase-locked loops. [analog, hybrid, discrete and digital systems

NASA Technical Reports Server (NTRS)

Gupta, S. C.

1974-01-01

The basic analysis and design procedures are described for the realization of analog phase-locked loops (APLL), hybrid phase-locked loops (HPLL), discrete phase-locked loops, and digital phase-locked loops (DPLL). Basic configurations are diagrammed, and performance curves are given. A discrete communications model is derived and developed. The use of the APLL as an optimum angle demodulator and the Kalman-Bucy approach to APLL design are discussed. The literature in the area of phase-locked loops is reviewed, and an extensive bibliography is given. Although the design of APLLs is fairly well documented, work on discrete, hybrid, and digital PLLs is scattered, and more will have to be done in the future to pinpoint the formal design of DPLLs.

Design of Digital Phase-Locked Loops For Advanced Digital Transponders

NASA Technical Reports Server (NTRS)

Nguyen, Tien M.

1994-01-01

For advanced digital space transponders, the Digital Phased-Locked Loops (DPLLs) can be designed using the available analog loops. DPLLs considered in this paper are derived from the Analog Phase-Locked Loop (APLL) using S-domain mapping techniques.

Binary phase locked loops for Omega receivers

NASA Technical Reports Server (NTRS)

Chamberlin, K.

1974-01-01

An all-digital phase lock loop (PLL) is considered because of a number of problems inherent in an employment of analog PLL. The digital PLL design presented solves these problems. A single loop measures all eight Omega time slots. Memory-aiding leads to the name of this design, the memory-aided phase lock loop (MAPLL). Basic operating principles are discussed and the superiority of MAPLL over the conventional digital phase lock loop with regard to the operational efficiency for Omega applications is demonstrated.

Frequency multiplexed flux locked loop architecture providing an array of DC SQUIDS having both shared and unshared components

DOEpatents

Ganther, Jr., Kenneth R.; Snapp, Lowell D.

2002-01-01

Architecture for frequency multiplexing multiple flux locked loops in a system comprising an array of DC SQUID sensors. The architecture involves dividing the traditional flux locked loop into multiple unshared components and a single shared component which, in operation, form a complete flux locked loop relative to each DC SQUID sensor. Each unshared flux locked loop component operates on a different flux modulation frequency. The architecture of the present invention allows a reduction from 2N to N+1 in the number of connections between the cryogenic DC SQUID sensors and their associated room temperature flux locked loops. Furthermore, the 1.times.N architecture of the present invention can be paralleled to form an M.times.N array architecture without increasing the required number of flux modulation frequencies.

Parallel Digital Phase-Locked Loops

NASA Technical Reports Server (NTRS)

Sadr, Ramin; Shah, Biren N.; Hinedi, Sami M.

1995-01-01

Wide-band microwave receivers of proposed type include digital phase-locked loops in which band-pass filtering and down-conversion of input signals implemented by banks of multirate digital filters operating in parallel. Called "parallel digital phase-locked loops" to distinguish them from other digital phase-locked loops. Systems conceived as cost-effective solution to problem of filtering signals at high sampling rates needed to accommodate wide input frequency bands. Each of M filters process 1/M of spectrum of signal.

A second-order frequency-aided digital phase-locked loop for Doppler rate tracking

NASA Astrophysics Data System (ADS)

Chie, C. M.

1980-08-01

A second-order digital phase-locked loop (DPLL) has a finite lock range which is a function of the frequency of the incoming signal to be tracked. For this reason, it is not capable of tracking an input with Doppler rate for an indefinite period of time. In this correspondence, an analytical expression for the hold-in time is derived. In addition, an all-digital scheme to alleviate this problem is proposed based on the information obtained from estimating the input signal frequency.

A class of all digital phase locked loops - Modeling and analysis

NASA Technical Reports Server (NTRS)

Reddy, C. P.; Gupta, S. C.

1973-01-01

An all digital phase locked loop which tracks the phase of the incoming signal once per carrier cycle is proposed. The different elements and their functions, and the phase lock operation are explained in detail. The general digital loop operation is governed by a nonlinear difference equation from which a suitable model is developed. The lock range for the general model is derived. The performance of the digital loop for phase step and frequency step inputs for different levels of quantization without loop filter are studied. The analytical results are checked by simulating the actual system on the digital computer.

Optimization of A 2-Micron Laser Frequency Stabilization System for a Double-Pulse CO2 Differential Absorption Lidar

NASA Technical Reports Server (NTRS)

Chen, Songsheng; Yu, Jirong; Bai, Yingsin; Koch, Grady; Petros, Mulugeta; Trieu, Bo; Petzar, Paul; Singh, Upendra N.; Kavaya, Michael J.; Beyon, Jeffrey

2010-01-01

A carbon dioxide (CO2) Differential Absorption Lidar (DIAL) for accurate CO2 concentration measurement requires a frequency locking system to achieve high frequency locking precision and stability. We describe the frequency locking system utilizing Frequency Modulation (FM), Phase Sensitive Detection (PSD), and Proportional Integration Derivative (PID) feedback servo loop, and report the optimization of the sensitivity of the system for the feed back loop based on the characteristics of a variable path-length CO2 gas cell. The CO2 gas cell is characterized with HITRAN database (2004). The method can be applied for any other frequency locking systems referring to gas absorption line.

An improved fast acquisition phase frequency detector for high speed phase-locked loops

NASA Astrophysics Data System (ADS)

Zhang, Lei; Wang, Zongmin; Zhang, Tieliang; Peng, Xinmang

2018-04-01

Phase-locked loops (PLL) have been widely applied in many high-speed designs, such as microprocessors or communication systems. In this paper, an improved fast acquisition phase frequency detector for high speed phase-locked loops is proposed. An improved structure based on dynamic latch is used to eliminate the non-ideal effect such as dead zone and blind zone. And frequency dividers are utilized to vastly extend the phase difference detection range and enhance the operation frequency of the PLL. Proposed PFD has been implemented in 65nm CMOS technology, which occupies an area of 0.0016mm2 and consumes 1.5mW only. Simulation results demonstrate that maximum operation frequency can be up to 5GHz. In addition, the acquisition time of PLL using proposed PFD is 1.0us which is 2.6 times faster than that of the PLL using latch-based PFD without divider.

A Digital Phase Lock Loop for an External Cavity Diode Laser

NASA Astrophysics Data System (ADS)

Wang, Xiao-Long; Tao, Tian-Jiong; Cheng, Bing; Wu, Bin; Xu, Yun-Fei; Wang, Zhao-Ying; Lin, Qiang

2011-08-01

A digital optical phase lock loop (OPLL) is implemented to synchronize the frequency and phase between two external cavity diode lasers (ECDL), generating Raman pulses for atom interferometry. The setup involves all-digital phase detection and a programmable digital proportional-integral-derivative (PID) loop in locking. The lock generates a narrow beat-note linewidth below 1 Hz and low phase-noise of 0.03rad2 between the master and slave ECDLs. The lock proves to be stable and robust, and all the locking parameters can be set and optimized on a computer interface with convenience, making the lock adaptable to various setups of laser systems.

Optical injection phase-lock loops

NASA Astrophysics Data System (ADS)

Bordonalli, Aldario Chrestani

Locking techniques have been widely applied for frequency synchronisation of semiconductor lasers used in coherent communication and microwave signal generation systems. Two main locking techniques, the optical phase-lock loop (OPLL) and optical injection locking (OIL) are analysed in this thesis. The principal limitations on OPLL performance result from the loop propagation delay, which makes difficult the implementation of high gain and wide bandwidth loops, leading to poor phase noise suppression performance and requiring the linewidths of the semiconductor laser sources to be less than a few megahertz for practical values of loop delay. The OIL phase noise suppression is controlled by the injected power. The principal limitations of the OIL implementation are the finite phase error under locked conditions and the narrow stable locking range the system provides at injected power levels required to reduce the phase noise output of semiconductor lasers significantly. This thesis demonstrates theoretically and experimentally that it is possible to overcome the limitations of OPLL and OIL systems by combining them, to form an optical injection phase-lock loop (OIPLL). The modelling of an OIPLL system is presented and compared with the equivalent OPLL and OIL results. Optical and electrical design of an homodyne OIPLL is detailed. Experimental results are given which verify the theoretical prediction that the OIPLL would keep the phase noise suppression as high as that of the OIL system over a much wider stable locking range, even with wide linewidth lasers and long loop delays. The experimental results for lasers with summed linewidth of 36 MHz and a loop delay of 15 ns showed measured phase error variances as low as 0.006 rad2 (500 MHz bandwidth) for locking bandwidths greater than 26 GHz, compared with the equivalent OPLL phase error variance of around 1 rad2 (500 MHz bandwidth) and the equivalent OIL locking bandwidth of less than 1.2 GHz.

A class of all digital phase locked loops - Modelling and analysis.

NASA Technical Reports Server (NTRS)

Reddy, C. P.; Gupta, S. C.

1972-01-01

An all digital phase locked loop which tracks the phase of the incoming signal once per carrier cycle is proposed. The different elements and their functions, and the phase lock operation are explained in detail. The general digital loop operation is governed by a non-linear difference equation from which a suitable model is developed. The lock range for the general model is derived. The performance of the digital loop for phase step, and frequency step inputs for different levels of quantization without loop filter, are studied. The analytical results are checked by simulating the actual system on the digital computer.

Analysis of first and second order binary quantized digital phase-locked loops for ideal and white Gaussian noise inputs

NASA Technical Reports Server (NTRS)

Blasche, P. R.

1980-01-01

Specific configurations of first and second order all digital phase locked loops are analyzed for both ideal and additive white gaussian noise inputs. In addition, a design for a hardware digital phase locked loop capable of either first or second order operation is presented along with appropriate experimental data obtained from testing of the hardware loop. All parameters chosen for the analysis and the design of the digital phase locked loop are consistent with an application to an Omega navigation receiver although neither the analysis nor the design are limited to this application.

Digital second-order phase-locked loop

NASA Technical Reports Server (NTRS)

Holmes, J. K.; Carl, C. C.; Tagnelia, C. R.

1975-01-01

Actual tests with second-order digital phase-locked loop at simulated relative Doppler shift of 1x0.0001 produced phase lock with timing error of 6.5 deg and no appreciable Doppler bias. Loop thus appears to achieve subcarrier synchronization and to remove bias due to Doppler shift in range of interest.

Phase-lock-loop application for fiber optic receiver

NASA Astrophysics Data System (ADS)

Ruggles, Stephen L.; Wills, Robert W.

1991-02-01

Phase-locked loop circuits are frequently employed in communication systems. In recent years, digital phase-locked loop circuits were utilized in optical communications systems. In an optical transceiver system, the digital phase-locked loop circuit is connected to the output of the receiver to extract a clock signal from the received coded data (NRZ, Bi-Phase, or Manchester). The clock signal is then used to reconstruct or recover the original data from the coded data. A theoretical approach to the design of a digital phase-locked loop circuit operation at 1 and 50 MHz is described. Hardware implementation of a breadboard design to function at 1 MHz and a printed-circuit board designed to function at 50 MHz were assembled using emitter coupled logic (ECL) to verify experimentally the theoretical design.

Phase-lock-loop application for fiber optic receiver

NASA Technical Reports Server (NTRS)

Ruggles, Stephen L.; Wills, Robert W.

1991-01-01

Phase-locked loop circuits are frequently employed in communication systems. In recent years, digital phase-locked loop circuits were utilized in optical communications systems. In an optical transceiver system, the digital phase-locked loop circuit is connected to the output of the receiver to extract a clock signal from the received coded data (NRZ, Bi-Phase, or Manchester). The clock signal is then used to reconstruct or recover the original data from the coded data. A theoretical approach to the design of a digital phase-locked loop circuit operation at 1 and 50 MHz is described. Hardware implementation of a breadboard design to function at 1 MHz and a printed-circuit board designed to function at 50 MHz were assembled using emitter coupled logic (ECL) to verify experimentally the theoretical design.

Optimum design of hybrid phase locked loops

NASA Technical Reports Server (NTRS)

Lee, P.; Yan, T.

1981-01-01

The design procedure of phase locked loops is described in which the analog loop filter is replaced by a digital computer. Specific design curves are given for the step and ramp input changes in phase. It is shown that the designed digital filter depends explicitly on the product of the sampling time and the noise bandwidth of the phase locked loop. This technique of optimization can be applied to the design of digital analog loops for other applications.

All-digital phase-lock loops for noise-free signals

NASA Technical Reports Server (NTRS)

Anderson, T. O.

1973-01-01

Bit-synchronizers utilize all-digital phase-lock loops that are referenced to a high frequency digital clock. Phase-lock loop of first design acquires frequency within nominal range and tracks phase; second design is modified for random binary data by addition of simple transition detector; and third design acquires frequency over wide dynamic range.

Long-term stable coherent beam combination of independent femtosecond Yb-fiber lasers.

PubMed

Tian, Haochen; Song, Youjian; Meng, Fei; Fang, Zhanjun; Hu, Minglie; Wang, Chingyue

2016-11-15

We demonstrate coherent beam combination between independent femtosecond Yb-fiber lasers by using the active phase locking of relative pulse timing and the carrier envelope phase based on a balanced optical cross-correlator and extracavity acoustic optical frequency shifter, respectively. The broadband quantum noise of femtosecond fiber lasers is suppressed via precise cavity dispersion control, instead of complicated high-bandwidth phase-locked loop design. Because of reduced quantum noise and a simplified phase-locked loop, stable phase locking that lasts for 1 hour has been obtained, as verified via both spectral interferometry and far-field beam interferometry. The approach can be applied to coherent pulse synthesis, as well as to remote frequency comb connection, allowing a practical all-fiber configuration.

Analysis and optimisation of the convergence behaviour of the single channel digital tanlock loop

NASA Astrophysics Data System (ADS)

Al-Kharji Al-Ali, Omar; Anani, Nader; Al-Araji, Saleh; Al-Qutayri, Mahmoud

2013-09-01

The mathematical analysis of the convergence behaviour of the first-order single channel digital tanlock loop (SC-DTL) is presented. This article also describes a novel technique that allows controlling the convergence speed of the loop, i.e. the time taken by the phase-error to reach its steady-state value, by using a specialised controller unit. The controller is used to adjust the convergence speed so as to selectively optimise a given performance parameter of the loop. For instance, the controller may be used to speed up the convergence in order to increase the lock range and improve the acquisition speed. However, since increasing the lock range can degrade the noise immunity of the system, in a noisy environment the controller can slow down the convergence speed until locking is achieved. Once the system is in lock, the convergence speed can be increased to improve the acquisition speed. The performance of the SC-DTL system was assessed against similar arctan-based loops and the results demonstrate the success of the controller in optimising the performance of the SC-DTL loop. The results of the system testing using MATLAB/Simulink simulation are presented. A prototype of the proposed system was implemented using a field programmable gate array module and the practical results are in good agreement with those obtained by simulation.

On the false lock behavior of polarity-type Costas loops with Manchester coded input. [for Space Shuttle Orbiter communication

NASA Technical Reports Server (NTRS)

Simon, M. K.

1977-01-01

A modification of a Costas loop is described, and the false lock behavior of this system is studied. The modified Costas loop hard limits the output of the in-phase channel, replaces the analog multiplier with a chopper-type device, and is equipped with single-pole arm filters in the loop. The false lock behavior associated with the use of Manchester coded data is investigated; the results can be applied to the assessment of the false lock margin on the Ku-band uplink to the Space Shuttle Orbiter through the TURSS.

Filter for third order phase locked loops

NASA Technical Reports Server (NTRS)

Crow, R. B.; Tausworthe, R. C. (Inventor)

1973-01-01

Filters for third-order phase-locked loops are used in receivers to acquire and track carrier signals, particularly signals subject to high doppler-rate changes in frequency. A loop filter with an open-loop transfer function and set of loop constants, setting the damping factor equal to unity are provided.

Behaviour of fractional loop delay zero crossing digital phase locked loop (FR-ZCDPLL)

NASA Astrophysics Data System (ADS)

Nasir, Qassim

2018-01-01

This article analyses the performance of the first-order zero crossing digital phase locked loops (FR-ZCDPLL) when fractional loop delay is added to loop. The non-linear dynamics of the loop is presented, analysed and examined through bifurcation behaviour. Numerical simulation of the loop is conducted to proof the mathematical analysis of the loop operation. The results of the loop simulation show that the proposed FR-ZCDPLL has enhanced the performance compared to the conventional zero crossing DPLL in terms of wider lock range, captured range and stable operation region. In addition, extensive experimental simulation was conducted to find the optimum loop parameters for different loop environmental conditions. The addition of the fractional loop delay network in the conventional loop also reduces the phase jitter and its variance especially when the signal-to-noise ratio is low.

Interferometric Phase-Locking of Two Electronic Oscillators Based on a Cascade Electro-Optic Modulator

NASA Astrophysics Data System (ADS)

Chien, Pie-Yau; Chao, Chen-Hsing

1993-03-01

An optical phase-locked loop system based on a triangular phase-modulated cascade Mach-Zehnder modulator is demonstrated. A reference oscillator of 10 MHz is multiplied such that it can be used to lock a target oscillator of 120 MHz. The phase error of \\varDeltaθe≤2.0× 10-4 rad/Hz1/2 has been implemented in this system.

Circuit breaker lock out assembly

DOEpatents

Gordy, W.T.

1983-05-18

A lock out assembly for a circuit breaker which consists of a generally step-shaped unitary base with an aperture in the small portion of the step-shaped base and a roughly S shaped retaining pin which loops through the large portion of the step-shaped base. The lock out assembly is adapted to fit over a circuit breaker with the handle switch projecting through the aperture, and the retaining pin projecting into an opening of the handle switch, preventing removal.

Circuit breaker lock out assembly

DOEpatents

Gordy, Wade T.

1984-01-01

A lock out assembly for a circuit breaker which consists of a generally step-shaped unitary base with an aperture in the small portion of the step-shaped base and a roughly "S" shaped retaining pin which loops through the large portion of the step-shaped base. The lock out assembly is adapted to fit over a circuit breaker with the handle switch projecting through the aperture, and the retaining pin projecting into an opening of the handle switch, preventing removal.

Phase-locked loop based on nanoelectromechanical resonant-body field effect transistor

NASA Astrophysics Data System (ADS)

Bartsch, S. T.; Rusu, A.; Ionescu, A. M.

2012-10-01

We demonstrate the room-temperature operation of a silicon nanoelectromechanical resonant-body field effect transistor (RB-FET) embedded into phase-locked loop (PLL). The very-high frequency resonator uses on-chip electrostatic actuation and transistor-based displacement detection. The heterodyne frequency down-conversion based on resistive FET mixing provides a loop feedback signal with high signal-to-noise ratio. We identify key parameters for PLL operation, and analyze the performance of the RB-FET at the system level. Used as resonant mass detector, the experimental frequency stability in the ppm-range translates into sub atto-gram (10-18 g) sensitivity in high vacuum. The feedback and control system are generic and may be extended to other mechanical resonators with transistor properties, such as graphene membranes and carbon nanotubes.

Analysis of a first order phase locked loop in the presence of Gaussian noise

NASA Technical Reports Server (NTRS)

Blasche, P. R.

1977-01-01

A first-order digital phase locked loop is analyzed by application of a Markov chain model. Steady state loop error probabilities, phase standard deviation, and mean loop transient times are determined for various input signal to noise ratios. Results for direct loop simulation are presented for comparison.

High frequency optoelectronic oscillators based on the optical feedback of semiconductor mode-locked laser diodes.

PubMed

Haji, Mohsin; Hou, Lianping; Kelly, Anthony E; Akbar, Jehan; Marsh, John H; Arnold, John M; Ironside, Charles N

2012-01-30

Optical self seeding feedback techniques can be used to improve the noise characteristics of passively mode-locked laser diodes. External cavities such as fiber optic cables can increase the memory of the phase and subsequently improve the timing jitter. In this work, an improved optical feedback architecture is proposed using an optical fiber loop delay as a cavity extension of the mode-locked laser. We investigate the effect of the noise reduction as a function of the loop length and feedback power. The well known composite cavity technique is also implemented for suppressing supermode noise artifacts presented due to harmonic mode locking effects. Using this method, we achieve a record low radio frequency linewidth of 192 Hz for any high frequency (>1 GHz) passively mode-locked laser to date (to the best of the authors' knowledge), making it promising for the development of high frequency optoelectronic oscillators.

Multifrequency zero-jitter delay-locked loop

NASA Astrophysics Data System (ADS)

Efendovich, Avner; Afek, Yachin; Sella, Coby; Bikowsky, Zeev

1994-01-01

The approach of an all-digital phase locked loop is used in this delay-locked loop circuit. This design is designated to a system with two processing units, a master CPU and a slave system chip, that share the same bus. It allows maximum utilization of the bus, as the minimal skew between the clocks of the two components significantly reduces idle periods, and also set-up and hold times. Changes in the operating frequency are possible, without falling out of synchronization. Due to the special lead-lag phase detector, the jitter of the clock is zero, when the loop is locked, under any working conditions.

2.4-3.2 GHz robust self-injecting injection-locked phase-locked loop

NASA Astrophysics Data System (ADS)

Yang, Jincheng; Zhang, Zhao; Qi, Nan; Liu, Liyuan; Liu, Jian; Wu, Nanjian

2018-04-01

In this paper, we propose a robust self-injecting injection-locked phase-locked loop (SI-ILPLL). It adopts a phase alignment loop (PAL) based on a subsampling phase frequency detector to align the phase between the injected pulse and the voltage-controlled oscillator (VCO) output. With the proposed phase frequency detector, the PAL performs phase alignment and the pulse generator can self-inject pulses into the VCO for injection locking. The subsampling phase detection and self-injection locking techniques can suppress the phase noise of the SI-ILPLL. The SI-ILPLL shows excellent robustness to environmental interference. The SI-ILPLL is implemented in 65 nm CMOS technology. It occupies an active area of 0.7 mm2. The measured root-mean-square (RMS) jitters at 3.2 GHz output without and with injection locking are 216 and 131 fs, respectively. When the supply voltage varies from 1.17 to 1.23 V and the temperature varies from 0 to 80 °C, the maximum jitter variation of all the output frequencies is less than 50 fs. The measured results demonstrate that even when a large interference appears at the supply voltage and unlocks the SI-ILPLL, the SI-ILPLL can self-recover its injection-locked state rapidly after the disturbance disappears, whereas the conventional ILPLL cannot self-recover its locked state after losing it. The power consumption of the SI-ILPLL is 7.4 mW under a 1.2 V supply voltage. The SI-ILPLL achieves a figure of merit (FOM) of -249 dB.

Investigation of air transportation technology at Ohio University, 1980. [general aviation aircraft and navigation aids

NASA Technical Reports Server (NTRS)

Mcfarland, R. H.

1981-01-01

Specific configurations of first and second order all digital phase locked loops were analyzed for both ideal and additive gaussian noise inputs. In addition, a design for a hardware digital phase locked loop capable of either first or second order operation was evaluated along with appropriate experimental data obtained from testing of the hardware loop. All parameters chosen for the analysis and the design of the digital phase locked loop were consistent with an application to an Omega navigation receiver although neither the analysis nor the design are limited to this application. For all cases tested, the experimental data showed close agreement with the analytical results indicating that the Markov chain model for first and second order digital phase locked loops are valid.

Closed-Loop Control of Vortex Formation in Separated Flows

NASA Technical Reports Server (NTRS)

Colonius, Tim; Joe, Won Tae; MacMynowski, Doug; Rowley, Clancy; Taira, Sam; Ahuja, Sunil

2010-01-01

In order to phase lock the flow at the desired shedding cycle, particularly at Phi,best, We designed a feedback compensator. (Even though the open-loop forcing at Wf below Wn can lead to phase-locked limit cycles with a high average lift,) This feedback controller resulted in the phase-locked limit cycles that the open-loop control could not achieve for alpha=30 and 40 Particularly for alpha=40, the feedback was able to stabilize the limit cycle that was not stable with any of the open-loop periodic forcing. This results in stable phase-locked limit cycles for a larger range of forcing frequencies than the open-loop control. Also, it was shown that the feedback achieved the high-lift unsteady flow states that open-loop control could not sustain even after the states have been achieved for a long period of time.

Efficient laser noise reduction method via actively stabilized optical delay line.

PubMed

Li, Dawei; Qian, Cheng; Li, Ye; Zhao, Jianye

2017-04-17

We report a fiber laser noise reduction method by locking it to an actively stabilized optical delay line, specifically a fiber-based Mach-Zehnder interferometer with a 10 km optical fiber spool. The fiber spool is used to achieve large arm imbalance. The heterodyne signal of the two arms converts the laser noise from the optical domain to several megahertz, and it is used in laser noise reduction by a phase-locked loop. An additional phase-locked loop is induced in the system to compensate the phase noise due to environmentally induced length fluctuations of the optical fiber spool. A major advantage of this structure is the efficient reduction of out-of-loop frequency noise, particularly at low Fourier frequency. The frequency noise reaches -30 dBc/Hz at 1 Hz, which is reduced by more than 90 dB compared with that of the laser in its free-running state.

Advanced Optical Fiber Communications Systems

DTIC Science & Technology

1994-08-31

phase locking . The PZT port has a tuning coefficient of 3.4 MHz/V. The time constants of the optical phase - locked loop ( OPLL ) filter’s pole and zero are... with the PSK receiver optical phase -I-ocked loop ( OPLL ). As we increased nz in our experiments, the larger signal fluctuations made it increasingly... lasers , since a phase - locked loop is 114 I not required for the DPSK receiver (unlike

On the performance of digital phase locked loops in the threshold region

NASA Technical Reports Server (NTRS)

Hurst, G. T.; Gupta, S. C.

1974-01-01

Extended Kalman filter algorithms are used to obtain a digital phase lock loop structure for demodulation of angle modulated signals. It is shown that the error variance equations obtained directly from this structure enable one to predict threshold if one retains higher frequency terms. This is in sharp contrast to the similar analysis of the analog phase lock loop, where the higher frequency terms are filtered out because of the low pass filter in the loop. Results are compared to actual simulation results and threshold region results obtained previously.

Simplified formula for mean cycle-slip time of phase-locked loops with steady-state phase error.

NASA Technical Reports Server (NTRS)

Tausworthe, R. C.

1972-01-01

Previous work shows that the mean time from lock to a slipped cycle of a phase-locked loop is given by a certain double integral. Accurate numerical evaluation of this formula for the second-order loop is extremely vexing because the difference between exponentially large quantities is involved. The presented article demonstrates a method in which a much-reduced precision program can be used to obtain the mean first-cycle slip time for a loop of arbitrary degree tracking at a specified SNR and steady-state phase error. It also presents a simple approximate formula that is asymptotically tight at higher loop SNR.

Design of a delay-locked-loop-based time-to-digital converter

NASA Astrophysics Data System (ADS)

Zhaoxin, Ma; Xuefei, Bai; Lu, Huang

2013-09-01

A time-to-digital converter (TDC) based on a reset-free and anti-harmonic delay-locked loop (DLL) circuit for wireless positioning systems is discussed and described. The DLL that generates 32-phase clocks and a cycle period detector is employed to avoid “false locking". Driven by multiphase clocks, an encoder detects pulses and outputs the phase of the clock when the pulse arrives. The proposed TDC was implemented in SMIC 0.18 μm CMOS technology, and its core area occupies 0.7 × 0.55 mm2. The reference frequency ranges from 20 to 150 MHz. An LSB resolution of 521 ps can be achieved by using a reference clock of 60 MHz and the DNL is less than ±0.75 LSB. It dissipates 31.5 mW at 1.8 V supply voltage.

Costas loop lock detection in the advanced receiver

NASA Technical Reports Server (NTRS)

Mileant, A.; Hinedi, S.

1989-01-01

The advanced receiver currently being developed uses a Costas digital loop to demodulate the subcarrier. Previous analyses of lock detector algorithms for Costas loops have ignored the effects of the inherent correlation between the samples of the phase-error process. Accounting for this correlation is necessary to achieve the desired lock-detection probability for a given false-alarm rate. Both analysis and simulations are used to quantify the effects of phase correlation on lock detection for the square-law and the absolute-value type detectors. Results are obtained which depict the lock-detection probability as a function of loop signal-to-noise ratio for a given false-alarm rate. The mathematical model and computer simulation show that the square-law detector experiences less degradation due to phase jitter than the absolute-value detector and that the degradation in detector signal-to-noise ratio is more pronounced for square-wave than for sine-wave signals.

High-accuracy resolver-to-digital conversion via phase locked loop based on PID controller

NASA Astrophysics Data System (ADS)

Li, Yaoling; Wu, Zhong

2018-03-01

The problem of resolver-to-digital conversion (RDC) is transformed into the problem of angle tracking control, and a phase locked loop (PLL) method based on PID controller is proposed in this paper. This controller comprises a typical PI controller plus an incomplete differential which can avoid the amplification of higher-frequency noise components by filtering the phase detection error with a low-pass filter. Compared with conventional ones, the proposed PLL method makes the converter a system of type III and thus the conversion accuracy can be improved. Experimental results demonstrate the effectiveness of the proposed method.

Phase-locking and coherent power combining of broadband linearly chirped optical waves.

PubMed

Satyan, Naresh; Vasilyev, Arseny; Rakuljic, George; White, Jeffrey O; Yariv, Amnon

2012-11-05

We propose, analyze and demonstrate the optoelectronic phase-locking of optical waves whose frequencies are chirped continuously and rapidly with time. The optical waves are derived from a common optoelectronic swept-frequency laser based on a semiconductor laser in a negative feedback loop, with a precisely linear frequency chirp of 400 GHz in 2 ms. In contrast to monochromatic waves, a differential delay between two linearly chirped optical waves results in a mutual frequency difference, and an acoustooptic frequency shifter is therefore used to phase-lock the two waves. We demonstrate and characterize homodyne and heterodyne optical phase-locked loops with rapidly chirped waves, and show the ability to precisely control the phase of the chirped optical waveform using a digital electronic oscillator. A loop bandwidth of ~ 60 kHz, and a residual phase error variance of < 0.01 rad(2) between the chirped waves is obtained. Further, we demonstrate the simultaneous phase-locking of two optical paths to a common master waveform, and the ability to electronically control the resultant two-element optical phased array. The results of this work enable coherent power combining of high-power fiber amplifiers-where a rapidly chirping seed laser reduces stimulated Brillouin scattering-and electronic beam steering of chirped optical waves.

A low jitter all - digital phase - locked loop in 180 nm CMOS technology

NASA Astrophysics Data System (ADS)

Shumkin, O. V.; Butuzov, V. A.; Normanov, D. D.; Ivanov, P. Yu

2016-02-01

An all-digital phase locked loop (ADPLL) was implemented in 180 nm CMOS technology. The proposed ADPLL uses a digitally controlled oscillator to achieve 3 ps resolution. The pure digital phase locked loop is attractive because it is less sensitive to noise and operating conditions than its analog counterpart. The proposed ADPLL can be easily applied to different process as a soft IP block, making it very suitable for system-on-chip applications.

High-speed clock recovery with phase-locked-loop-based on LiNbO3 modulators

NASA Astrophysics Data System (ADS)

Zhu, Guanghao; Chen, Hongmin; Wang, Qiang; Dutta, Niloy K.

2003-08-01

In this paper, we present a scheme for recovering 10 GHz clock from 40 Gb/s and 80 Gb/s time division multiplexed (TDM) return to zero (RZ) data stream. The proposed clock recovery is successfully demonstrated using an electrical phase locked loop (PLL). The jitter of the recovered clock is estimated to be around 50 fs. The key part in the proposed clock recovery circuit is a LiNbO3 Mach-Zehnder modulator which is shown to be highly effective in optical to electrical down conversion.

Interferometric phase locking of two electronic oscillators with a cascade electro-optic modulator

NASA Astrophysics Data System (ADS)

Chao, C. H.; Chien, P. Y.; Chang, L. W.; Juang, F. Y.; Hsia, C. H.; Chang, C. C.

1993-01-01

An optical-type electrical phase-locked-loop system based on a cascade electro-optic modulator has been demonstrated. By using this technique, a set of optical-type phase detectors, operating at any harmonic frequencies of two applied phase-modulation signals, has been implemented.

The performance of a sampled data delay lock loop implemented with a Kalman loop filter

NASA Astrophysics Data System (ADS)

Eilts, H. S.

1980-01-01

The purpose of this study is to evaluate the steady-state and transient (lock-up) performance of a tracking loop implemented with a Kalman filter. Steady-state performance criteria are errors due to measurement noise (jitter) and Doppler errors due to motion of the tracking loop. Trade-offs exist between the two criteria such that increasing performance with respect to either one will cause performance decrease with respect to the other. It is shown that by carefully selecting filter parameters reasonable performance can be obtained for both criteria simultaneously. It is also shown that lock-up performance for the loop is acceptable when these parameters are used.

Target-in-the-loop high-power adaptive phase-locked fiber laser array using single-frequency dithering technique

NASA Astrophysics Data System (ADS)

Tao, R.; Ma, Y.; Si, L.; Dong, X.; Zhou, P.; Liu, Z.

2011-11-01

We present a theoretical and experimental study of a target-in-the-loop (TIL) high-power adaptive phase-locked fiber laser array. The system configuration of the TIL adaptive phase-locked fiber laser array is introduced, and the fundamental theory for TIL based on the single-dithering technique is deduced for the first time. Two 10-W-level high-power fiber amplifiers are set up and adaptive phase locking of the two fiber amplifiers is accomplished successfully by implementing a single-dithering algorithm on a signal processor. The experimental results demonstrate that the optical phase noise for each beam channel can be effectively compensated by the TIL adaptive optics system under high-power applications and the fringe contrast on a remotely located extended target is advanced from 12% to 74% for the two 10-W-level fiber amplifiers.

Mid-infrared multiheterodyne spectroscopy with phase-locked quantum cascade lasers

NASA Astrophysics Data System (ADS)

Westberg, J.; Sterczewski, L. A.; Wysocki, G.

2017-04-01

Fabry-Pérot (FP) quantum cascade lasers (QCLs) provide purely electronically controlled monolithic sources for broadband mid-infrared (mid-IR) multiheterodyne spectroscopy (MHS), which benefits from the large gain bandwidth of the QCLs without sacrificing the narrowband properties commonly associated with the single mode distributed feedback variant. We demonstrate a FP-QCL based multiheterodyne spectrometer with a short-term noise-equivalent absorption of ˜3 × 10-4/ √{ H z } , a mid-IR spectral coverage of 25 cm-1, and very short acquisition time (10 μs) capability. The broadband potential is demonstrated by measuring the absorption spectra of ammonia and isobutane under atmospheric pressure conditions. The stability of the system is enhanced by a two-stage active frequency inter-locking procedure, where the two QCLs are pre-locked with a slow feedback loop based on an analog frequency discriminator, followed by a high bandwidth optical phase-locked loop. The locking system provides a relative frequency stability in the sub kHz range over seconds of integration time. The strength of the technique lies in the ability to acquire spectral information from all optical modes simultaneously and individually, which bodes for a versatile and cost effective spectrometer for mid-IR chemical gas sensing.

Loran digital phase-locked loop and RF front-end system error analysis

NASA Technical Reports Server (NTRS)

Mccall, D. L.

1979-01-01

An analysis of the system performance of the digital phase locked loops (DPLL) and RF front end that are implemented in the MINI-L4 Loran receiver is presented. Three of the four experiments deal with the performance of the digital phase locked loops. The other experiment deals with the RF front end and DPLL system error which arise in the front end due to poor signal to noise ratios. The ability of the DPLLs to track the offsets is studied.

Two AFC Loops For Low CNR And High Dynamics

NASA Technical Reports Server (NTRS)

Hinedi, Sami M.; Aguirre, Sergio

1992-01-01

Two alternative digital automatic-frequency-control (AFC) loops proposed to acquire (or reacquire) and track frequency of received carrier radio signal. Intended for use where carrier-to-noise ratios (CNR's) low and carrier frequency characterized by high Doppler shift and Doppler rate because of high relative speed and acceleration, respectively, between transmitter and receiver. Either AFC loops used in place of phase-locked loop. New loop concepts integrate ideas from classical spectrum-estimation, digital-phase-locked-loop, and Kalman-Filter theories.

Ultra-low noise optical phase-locked loop

NASA Astrophysics Data System (ADS)

Ayotte, Simon; Babin, André; Costin, François

2014-03-01

The relative phase between two fiber lasers is controlled via a high performance optical phase-locked loop (OPLL). Two parameters are of particular importance for the design: the intrinsic phase noise of the laser (i.e. its linewidth) and a high-gain, low-noise electronic locking loop. In this work, one of the lowest phase noise fiber lasers commercially available was selected (i.e. NP Photonics Rock fiber laser module), with sub-kHz linewidth at 1550.12 nm. However, the fast tuning mechanism of such lasers is through stretching its cavity length with a piezoelectric transducer which has a few 10s kHz bandwidth. To further increase the locking loop bandwidth to several MHz, a second tuning mechanism is used by adding a Lithium Niobate phase modulator in the laser signal path. The OPLL is thus divided into two locking loops, a slow loop acting on the laser piezoelectric transducer and a fast loop acting on the phase modulator. The beat signal between the two phase-locked lasers yields a highly pure sine wave with an integrated phase error of 0.0012 rad. This is orders of magnitude lower than similar existing systems such as the Laser Synthesizer used for distribution of photonic local oscillator (LO) for the Atacama Large Millimeter Array radio telescope in Chile. Other applications for ultra-low noise OPLL include coherent power combining, Brillouin sensing, light detection and ranging (LIDAR), fiber optic gyroscopes, phased array antenna and beam steering, generation of LOs for next generation coherent communication systems, coherent analog optical links, terahertz generation and coherent spectroscopy.

A closed-loop system for frequency tracking of piezoresistive cantilever sensors

NASA Astrophysics Data System (ADS)

Wasisto, Hutomo Suryo; Zhang, Qing; Merzsch, Stephan; Waag, Andreas; Peiner, Erwin

2013-05-01

A closed loop circuit capable of tracking resonant frequencies for MEMS-based piezoresistive cantilever resonators is developed in this work. The proposed closed-loop system is mainly based on a phase locked loop (PLL) circuit. In order to lock onto the resonant frequency of the resonator, an actuation signal generated from a voltage-controlled oscillator (VCO) is locked to the phase of the input reference signal of the cantilever sensor. In addition to the PLL component, an instrumentation amplifier and an active low pass filter (LPF) are connected to the system for gaining the amplitude and reducing the noise of the cantilever output signals. The LPF can transform a rectangular signal into a sinusoidal signal with voltage amplitudes ranging from 5 to 10 V which are sufficient for a piezoactuator input (i.e., maintaining a large output signal of the cantilever sensor). To demonstrate the functionality of the system, a self-sensing silicon cantilever resonator with a built-in piezoresistive Wheatstone bridge is fabricated and integrated with the circuit. A piezoactuator is utilized for actuating the cantilever into resonance. Implementation of this closed loop system is used to track the resonant frequency of a silicon cantilever-based sensor resonating at 9.4 kHz under a cross-sensitivity test of ambient temperature. The changes of the resonant frequency are interpreted using a frequency counter connected to the system. From the experimental results, the temperature sensitivity and coefficient of the employed sensor are 0.3 Hz/°C and 32.8 ppm/°C, respectively. The frequency stability of the system can reach up to 0.08 Hz. The development of this system will enable real-time nanoparticle monitoring systems and provide a miniaturization of the instrumentation modules for cantilever-based nanoparticle detectors.

Optically phase-locked electronic speckle pattern interferometer

NASA Astrophysics Data System (ADS)

Moran, Steven E.; Law, Robert; Craig, Peter N.; Goldberg, Warren M.

1987-02-01

The design, theory, operation, and characteristics of an optically phase-locked electronic speckle pattern interferometer (OPL-ESPI) are described. The OPL-ESPI system couples an optical phase-locked loop with an ESPI system to generate real-time equal Doppler speckle contours of moving objects from unstable sensor platforms. In addition, the optical phase-locked loop provides the basis for a new ESPI video signal processing technique which incorporates local oscillator phase shifting coupled with video sequential frame subtraction.

Note: Low phase noise programmable phase-locked loop with high temperature stability.

PubMed

Michálek, Vojtěch; Procházka, Ivan

2017-03-01

The design and construction of low jitter programmable phase-locked loop with low temperature coefficient of phase are presented. It has been designed for demanding high precision timing applications, especially as a clock source for event timer with subpicosecond precision. The phase-locked loop itself has a jitter of few hundreds of femtoseconds. It produces square wave with programmable output frequency from 100 MHz to 500 MHz and programmable amplitude of 0.25 V to 1.2 V peak-to-peak, which is locked to 5 MHz or 10 MHz reference frequency common for disciplined oscillators and highly stable clocks such as hydrogen maser. Moreover, it comprises an on-board temperature compensated crystal oscillator for stand-alone usage. The device provides temperature coefficient of the phase lock of 0.9 ps/K near room temperature.

Near optimum digital phase locked loops.

NASA Technical Reports Server (NTRS)

Polk, D. R.; Gupta, S. C.

1972-01-01

Near optimum digital phase locked loops are derived utilizing nonlinear estimation theory. Nonlinear approximations are employed to yield realizable loop structures. Baseband equivalent loop gains are derived which under high signal to noise ratio conditions may be calculated off-line. Additional simplifications are made which permit the application of the Kalman filter algorithms to determine the optimum loop filter. Performance is evaluated by a theoretical analysis and by simulation. Theoretical and simulated results are discussed and a comparison to analog results is made.

Phase-locked loops and their application

NASA Technical Reports Server (NTRS)

Lindsey, W. C. (Editor); Simon, M. K.

1978-01-01

A collection of papers is presented on the characteristics and capabilities of phase-locked loops (PLLs), along with some applications of interest. The discussion covers basic theory (linear and nonlinear); acquisition; threshold; stability; frequency demodulation and detection; tracking; cycle slipping and loss of lock; phase-locked oscillators; operation and performance in the presence of noise; AGC, AFC, and APC circuits and systems; digital PLL; and applications and miscellaneous. With the rapid development of IC technology, PLLs are expected to be used widely in consumer electronics.

A digital optical phase-locked loop for diode lasers based on field programmable gate array.

PubMed

Xu, Zhouxiang; Zhang, Xian; Huang, Kaikai; Lu, Xuanhui

2012-09-01

We have designed and implemented a highly digital optical phase-locked loop (OPLL) for diode lasers in atom interferometry. The three parts of controlling circuit in this OPLL, including phase and frequency detector (PFD), loop filter and proportional integral derivative (PID) controller, are implemented in a single field programmable gate array chip. A structure type compatible with the model MAX9382∕MCH12140 is chosen for PFD and pipeline and parallelism technology have been adapted in PID controller. Especially, high speed clock and twisted ring counter have been integrated in the most crucial part, the loop filter. This OPLL has the narrow beat note line width below 1 Hz, residual mean-square phase error of 0.14 rad(2) and transition time of 100 μs under 10 MHz frequency step. A main innovation of this design is the completely digitalization of the whole controlling circuit in OPLL for diode lasers.

A digital optical phase-locked loop for diode lasers based on field programmable gate array

NASA Astrophysics Data System (ADS)

Xu, Zhouxiang; Zhang, Xian; Huang, Kaikai; Lu, Xuanhui

2012-09-01

We have designed and implemented a highly digital optical phase-locked loop (OPLL) for diode lasers in atom interferometry. The three parts of controlling circuit in this OPLL, including phase and frequency detector (PFD), loop filter and proportional integral derivative (PID) controller, are implemented in a single field programmable gate array chip. A structure type compatible with the model MAX9382/MCH12140 is chosen for PFD and pipeline and parallelism technology have been adapted in PID controller. Especially, high speed clock and twisted ring counter have been integrated in the most crucial part, the loop filter. This OPLL has the narrow beat note line width below 1 Hz, residual mean-square phase error of 0.14 rad2 and transition time of 100 μs under 10 MHz frequency step. A main innovation of this design is the completely digitalization of the whole controlling circuit in OPLL for diode lasers.

Field-programmable gate array-controlled sweep velocity-locked laser pulse generator

NASA Astrophysics Data System (ADS)

Chen, Zhen; Hefferman, Gerald; Wei, Tao

2017-05-01

A field-programmable gate array (FPGA)-controlled sweep velocity-locked laser pulse generator (SV-LLPG) design based on an all-digital phase-locked loop (ADPLL) is proposed. A distributed feedback laser with modulated injection current was used as a swept-frequency laser source. An open-loop predistortion modulation waveform was calibrated using a feedback iteration method to initially improve frequency sweep linearity. An ADPLL control system was then implemented using an FPGA to lock the output of a Mach-Zehnder interferometer that was directly proportional to laser sweep velocity to an on-board system clock. Using this system, linearly chirped laser pulses with a sweep bandwidth of 111.16 GHz were demonstrated. Further testing evaluating the sensing utility of the system was conducted. In this test, the SV-LLPG served as the swept laser source of an optical frequency-domain reflectometry system used to interrogate a subterahertz range fiber structure (sub-THz-FS) array. A static strain test was then conducted and linear sensor results were observed.

Controlled-Root Approach To Digital Phase-Locked Loops

NASA Technical Reports Server (NTRS)

Stephens, Scott A.; Thomas, J. Brooks

1995-01-01

Performance tailored more flexibly and directly to satisfy design requirements. Controlled-root approach improved method for analysis and design of digital phase-locked loops (DPLLs). Developed rigorously from first principles for fully digital loops, making DPLL theory and design simpler and more straightforward (particularly for third- or fourth-order DPLL) and controlling performance more accurately in case of high gain.

Performance evaluation of digital phase-locked loops for advanced deep space transponders

NASA Technical Reports Server (NTRS)

Nguyen, T. M.; Hinedi, S. M.; Yeh, H.-G.; Kyriacou, C.

1994-01-01

The performances of the digital phase-locked loops (DPLL's) for the advanced deep-space transponders (ADT's) are investigated. DPLL's considered in this article are derived from the analog phase-locked loop, which is currently employed by the NASA standard deep space transponder, using S-domain to Z-domain mapping techniques. Three mappings are used to develop digital approximations of the standard deep space analog phase-locked loop, namely the bilinear transformation (BT), impulse invariant transformation (IIT), and step invariant transformation (SIT) techniques. The performance in terms of the closed loop phase and magnitude responses, carrier tracking jitter, and response of the loop to the phase offset (the difference between in incoming phase and reference phase) is evaluated for each digital approximation. Theoretical results of the carrier tracking jitter for command-on and command-off cases are then validated by computer simulation. Both theoretical and computer simulation results show that at high sampling frequency, the DPLL's approximated by all three transformations have the same tracking jitter. However, at low sampling frequency, the digital approximation using BT outperforms the others. The minimum sampling frequency for adequate tracking performance is determined for each digital approximation of the analog loop. In addition, computer simulation shows that the DPLL developed by BT provides faster response to the phase offset than IIT and SIT.

A simple second-order digital phase-locked loop.

NASA Technical Reports Server (NTRS)

Tegnelia, C. R.

1972-01-01

A simple second-order digital phase-locked loop has been designed for the Viking Orbiter 1975 command system. Excluding analog-to-digital conversion, implementation of the loop requires only an adder/subtractor, two registers, and a correctable counter with control logic. The loop considers only the polarity of phase error and corrects system clocks according to a filtered sequence of this polarity. The loop is insensitive to input gain variation, and therefore offers the advantage of stable performance over long life. Predictable performance is guaranteed by extreme reliability of acquisition, yet in the steady state the loop produces only a slight degradation with respect to analog loop performance.

Compact silicon photonics-based multi laser module for sensing

NASA Astrophysics Data System (ADS)

Ayotte, S.; Costin, F.; Babin, A.; Paré-Olivier, G.; Morin, M.; Filion, B.; Bédard, K.; Chrétien, P.; Bilodeau, G.; Girard-Deschênes, E.; Perron, L.-P.; Davidson, C.-A.; D'Amato, D.; Laplante, M.; Blanchet-Létourneau, J.

2018-02-01

A compact three-laser source for optical sensing is presented. It is based on a low-noise implementation of the Pound Drever-Hall method and comprises high-bandwidth optical phase-locked loops. The outputs from three semiconductor distributed feedback lasers, mounted on thermo-electric coolers (TEC), are coupled with micro-lenses into a silicon photonics (SiP) chip that performs beat note detection and several other functions. The chip comprises phase modulators, variable optical attenuators, multi-mode-interference couplers, variable ratio tap couplers, integrated photodiodes and optical fiber butt-couplers. Electrical connections between a metallized ceramic and the TECs, lasers and SiP chip are achieved by wirebonds. All these components stand within a 35 mm by 35 mm package which is interfaced with 90 electrical pins and two fiber pigtails. One pigtail carries the signals from a master and slave lasers, while another carries that from a second slave laser. The pins are soldered to a printed circuit board featuring a micro-processor that controls and monitors the system to ensure stable operation over fluctuating environmental conditions. This highly adaptable multi-laser source can address various sensing applications requiring the tracking of up to three narrow spectral features with a high bandwidth. It is used to sense a fiber-based ring resonator emulating a resonant fiber optics gyroscope. The master laser is locked to the resonator with a loop bandwidth greater than 1 MHz. The slave lasers are offset frequency locked to the master laser with loop bandwidths greater than 100 MHz. This high performance source is compact, automated, robust, and remains locked for days.

Binary phase lock loops for simplified OMEGA receivers

NASA Technical Reports Server (NTRS)

Burhans, R. W.

1974-01-01

A sampled binary phase lock loop is proposed for periodically correcting OMEGA receiver internal clocks. The circuit is particularly simple to implement and provides a means of generating long range 3.4 KHz difference frequency lanes from simultaneous pair measurements.

Frequency set on systems

NASA Astrophysics Data System (ADS)

Wilby, W. A.; Brett, A. R. H.

Frequency set on techniques used in ECM applications include repeater jammers, frequency memory loops (RF and optical), coherent digital RF memories, and closed loop VCO set on systems. Closed loop frequency set on systems using analog phase and frequency locking are considered to have a number of cost and performance advantages. Their performance is discussed in terms of frequency accuracy, bandwidth, locking time, stability, and simultaneous signals. Some experimental results are presented which show typical locking performance. Future ECM systems might require a response to very short pulses. Acoustooptic and fiber-optic pulse stretching techniques can be used to meet such requirements.

Digital phase-lock loop

NASA Technical Reports Server (NTRS)

Thomas, Jr., Jess B. (Inventor)

1991-01-01

An improved digital phase lock loop incorporates several distinctive features that attain better performance at high loop gain and better phase accuracy. These features include: phase feedback to a number-controlled oscillator in addition to phase rate; analytical tracking of phase (both integer and fractional cycles); an amplitude-insensitive phase extractor; a more accurate method for extracting measured phase; a method for changing loop gain during a track without loss of lock; and a method for avoiding loss of sampled data during computation delay, while maintaining excellent tracking performance. The advantages of using phase and phase-rate feedback are demonstrated by comparing performance with that of rate-only feedback. Extraction of phase by the method of modeling provides accurate phase measurements even when the number-controlled oscillator phase is discontinuously updated.

All-digital phase-locked loop with 50-cycle lock time suitable for high-performance microprocessors

NASA Astrophysics Data System (ADS)

Dunning, Jim; Garcia, Gerald; Lundberg, Jim; Nuckolls, Ed

1995-04-01

A frequency-synthesizing, all-digital phase-locked loop (ADPLL) is fully integrated with a 0.5 micron CMOS microprocessor. The ADPLL has a 50-cycle phase lock, has a gain mechanism independent of process, voltage, and temperature, and is immune to input jitter. A digitally-controlled oscillator (DCO) forms the core of the ADPLL and operates from 50 to 550 MHz, running at 4x the reference clock frequency. The DCO has 16 b of binarily weighted control and achieves LSB resolution under 500 fs.

Medial Meniscal Root Avulsion: A Biomechanical Comparison of 4 Different Repair Constructs.

PubMed

Mitchell, Richard; Pitts, Ryan; Kim, Young-Mo; Matava, Matthew J

2016-01-01

To evaluate the time-zero load-to-failure strength of 4 different constructs used to repair medial meniscal root avulsions. Sixty fresh-frozen cadaveric knees with a mean age of 74 years were used for this study. Each knee was dissected to isolate the attachment of the posterior root of the medial meniscus to the tibial plateau. An Instron machine (Instron, Norwood, MA) with a custom-designed clamp was used to avulse the intact posterior meniscal root in 12 control specimens. An additional 48 specimens were tested after transection of the native meniscal root to evaluate the pullout strength of 4 different repair constructs using No. 0 FiberWire suture (Arthrex, Naples, FL): a single suture (n = 12), a double suture (n = 12), a loop stitch (n = 12), and a locking loop stitch (n = 12). Analysis of variance was used to compare load to failure and stiffness of all 4 groups; pair-wise, between-group differences were also assessed. Repair failure occurred most commonly by suture pullout in 94% of the specimens in the repair groups. For the controls, failure occurred most commonly at the meniscus-clamp interface. Failure load was highest for the control group (mean, 359.5 ± 168 N), followed in descending order by the locking loop stitch (191.4 ± 45.1 N), loop stitch (119.6 ± 55.0 N), double suture (96.2 ± 51.4 N), and single suture (58.2 ± 29.6 N). The control group was significantly stronger than 3 of the experimental groups (single suture [95% CI, 3.8 to 11.3], double suture [95% CI, 2.1 to 6.4], and loop stitch [95% CI, 2.0 to 4.5]; P < .0001) but not the locking loop stitch (P = .003; 95% CI, 1.2 to 3.2). The locking loop stitch was significantly stronger than the single suture (P < .0001; 95% CI, 2.0 to 5.4) and double suture (P = .003; 95% CI, 1.2 to 2.9). The locking loop stitch was significantly stiffer than the single suture (P < .0001; 95% CI, 3.8 to 20.3), double suture (P < .0001; 95% CI, 2.0 to 9.8), and loop stitch (P = .03; 95% CI, 1.1 to 5.5) but not significantly different from the control group (P = .93; 95% CI, 0.3 to 1.9). Age and gender had no effect on pullout strength. The results of this study show that the locking loop stitch provided time-zero load-to-failure strength that most closely approximated the strength of the native meniscal root in addition to being significantly stronger and stiffer than 3 other commonly used repair methods. The true strength of the native meniscal root is unknown based on limitations with our testing methodology. The locking loop stitch exhibited the highest load to failure and stiffness of the 4 fixation methods tested, despite the fact that none of the fixation methods replicated the strength of the intact meniscal root. It is currently unknown what strength of fixation is required for healing of meniscal root repairs. Copyright © 2016 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

Heart-Rate and Breath-Rate Monitor

NASA Technical Reports Server (NTRS)

Cooper, T. G.

1983-01-01

Circuit requiring only four integrated circuits (IC's) measures both heart rate and breath rate. Phase-locked loops lock on heart-rate and respiration-rate input signals. Each loop IC contains two phase comparators. Positive-edge-triggered circuit used in making monitors insensitive to dutycycle variations.

Optical frequency locked loop for long-term stabilization of broad-line DFB laser frequency difference

NASA Astrophysics Data System (ADS)

Lipka, Michał; Parniak, Michał; Wasilewski, Wojciech

2017-09-01

We present an experimental realization of the optical frequency locked loop applied to long-term frequency difference stabilization of broad-line DFB lasers along with a new independent method to characterize relative phase fluctuations of two lasers. The presented design is based on a fast photodiode matched with an integrated phase-frequency detector chip. The locking setup is digitally tunable in real time, insensitive to environmental perturbations and compatible with commercially available laser current control modules. We present a simple model and a quick method to optimize the loop for a given hardware relying exclusively on simple measurements in time domain. Step response of the system as well as phase characteristics closely agree with the theoretical model. Finally, frequency stabilization for offsets within 4-15 GHz working range achieving <0.1 Hz long-term stability of the beat note frequency for 500 s averaging time period is demonstrated. For these measurements we employ an I/Q mixer that allows us to precisely and independently measure the full phase trace of the beat note signal.

Designing Estimator/Predictor Digital Phase-Locked Loops

NASA Technical Reports Server (NTRS)

Statman, J. I.; Hurd, W. J.

1988-01-01

Signal delays in equipment compensated automatically. New approach to design of digital phase-locked loop (DPLL) incorporates concepts from estimation theory and involves decomposition of closed-loop transfer function into estimator and predictor. Estimator provides recursive estimates of phase, frequency, and higher order derivatives of phase with respect to time, while predictor compensates for delay, called "transport lag," caused by PLL equipment and by DPLL computations.

Digital Phase-Locked Loop With Phase And Frequency Feedback

NASA Technical Reports Server (NTRS)

Thomas, J. Brooks

1991-01-01

Advanced design for digital phase-lock loop (DPLL) allows loop gains higher than those used in other designs. Divided into two major components: counterrotation processor and tracking processor. Notable features include use of both phase and rate-of-change-of-phase feedback instead of frequency feedback alone, normalized sine phase extractor, improved method for extracting measured phase, and improved method for "compressing" output rate.

Novel All Digital Ring Cavity Locking Servo

NASA Astrophysics Data System (ADS)

Baker, J.; Gallant, D.; Lucero, A.; Miller, H.; Stohs, J.

We plan to use this servo in the new 50W 589-nm sodium guidestar laser to be installed in the AMOS facility in July 2010. Though the basic design is unchanged from the successful Hillman/Denman design, numerous improvements are being implemented in order to bring the device even further out of the lab and into the field. The basic building block of the Hillman/Denman design are two low noise master oscillators that are injected into higher power slave oscillators that are locked to the frequencies of the master oscillator cavities. In the previous system a traditional analog Pound-Drever-Hall (PDH) loop was employed to provide the frequency locking. Analog servos work well, in general, but robust locking for a complex set of multiply-interconnected PDH servos in the guidestar source challenges existing analog approaches. One of the significant changes demonstrated thus far is the implementation of an all-digital servo using only COTS components and a fast CISC processing architecture for orchestrating the basic PDH loops active within system. Compared to the traditionally used analog servo loops, an all-digital servo is a not only an orders-of-magnitude simpler servo loop to implement but the control loop can be modified by merely changing the computer code. Field conditions are often different from laboratory conditions, requiring subtle algorithm changes, and physical accessibility in the field is generally limited and difficult. Remotely implemented, trimmer-less and solderless servo upgrades are a much welcomed improvement in the field installed guidestar system. Also, OEM replacement of usual benchtop components saves considerable space and weight as well in the locking system. We will report on the details of the servo system and recent experimental results locking a master-slave laser oscillator system using the all-digital Pound-Drever-Hall loop.

Method of Implementing Digital Phase-Locked Loops

NASA Technical Reports Server (NTRS)

Stephens, Scott A. (Inventor); Thomas, J. Brooks (Inventor)

1997-01-01

In a new formulation for digital phase-locked loops, loop-filter constants are determined from loop roots that can each be selectively placed in the s-plane on the basis of a new set of parameters, each with simple and direct physical meaning in terms of loop noise bandwidth, root-specific decay rate, and root-specific damping. Loops of first to fourth order are treated in the continuous-update approximation (B(sub L)T approaches 0) and in a discrete-update formulation with arbitrary B(sub L)T. Deficiencies of the continuous-update approximation in large-B(sub L)T applications are avoided in the new discrete-update formulation.

An all digital phase locked loop for synchronization of a sinusoidal signal embedded in white Gaussian noise

NASA Technical Reports Server (NTRS)

Reddy, C. P.; Gupta, S. C.

1973-01-01

An all digital phase locked loop which tracks the phase of the incoming sinusoidal signal once per carrier cycle is proposed. The different elements and their functions and the phase lock operation are explained in detail. The nonlinear difference equations which govern the operation of the digital loop when the incoming signal is embedded in white Gaussian noise are derived, and a suitable model is specified. The performance of the digital loop is considered for the synchronization of a sinusoidal signal. For this, the noise term is suitably modelled which allows specification of the output probabilities for the two level quantizer in the loop at any given phase error. The loop filter considered increases the probability of proper phase correction. The phase error states in modulo two-pi forms a finite state Markov chain which enables the calculation of steady state probabilities, RMS phase error, transient response and mean time for cycle skipping.

A GPS Phase-Locked Loop Performance Metric Based on the Phase Discriminator Output

PubMed Central

Stevanovic, Stefan; Pervan, Boris

2018-01-01

We propose a novel GPS phase-lock loop (PLL) performance metric based on the standard deviation of tracking error (defined as the discriminator’s estimate of the true phase error), and explain its advantages over the popular phase jitter metric using theory, numerical simulation, and experimental results. We derive an augmented GPS phase-lock loop (PLL) linear model, which includes the effect of coherent averaging, to be used in conjunction with this proposed metric. The augmented linear model allows more accurate calculation of tracking error standard deviation in the presence of additive white Gaussian noise (AWGN) as compared to traditional linear models. The standard deviation of tracking error, with a threshold corresponding to half of the arctangent discriminator pull-in region, is shown to be a more reliable/robust measure of PLL performance under interference conditions than the phase jitter metric. In addition, the augmented linear model is shown to be valid up until this threshold, which facilitates efficient performance prediction, so that time-consuming direct simulations and costly experimental testing can be reserved for PLL designs that are much more likely to be successful. The effect of varying receiver reference oscillator quality on the tracking error metric is also considered. PMID:29351250

Optically stabilized Erbium fiber frequency comb with hybrid mode-locking and a broad tunable range of repetition rate.

PubMed

Yang, Honglei; Wu, Xuejian; Zhang, Hongyuan; Zhao, Shijie; Yang, Lijun; Wei, Haoyun; Li, Yan

2016-12-01

We present an optically stabilized Erbium fiber frequency comb with a broad repetition rate tuning range based on a hybrid mode-locked oscillator. We lock two comb modes to narrow-linewidth reference lasers in turn to investigate the best performance of control loops. The control bandwidth of fast and slow piezoelectric transducers reaches 70 kHz, while that of pump current modulation with phase-lead compensation is extended to 32 kHz, exceeding laser intrinsic response. Eventually, simultaneous lock of both loops is realized to totally phase-stabilize the comb, which will facilitate precision dual-comb spectroscopy, laser ranging, and timing distribution. In addition, a 1.8-MHz span of the repetition rate is achieved by an automatic optical delay line that is helpful in manufacturing a secondary comb with a similar repetition rate. The oscillator is housed in a homemade temperature-controlled box with an accuracy of ±0.02  K, which not only keeps high signal-to-noise ratio of the beat notes with reference lasers, but also guarantees self-starting at the same mode-locking every time.

DC superconducting quantum interference device usable in nuclear quadrupole resonance and zero field nuclear magnetic spectrometers

DOEpatents

Fan, N.Q.; Clarke, J.

1993-10-19

A spectrometer for measuring the nuclear quadrupole resonance spectra or the zero-field nuclear magnetic resonance spectra generated by a sample is disclosed. The spectrometer uses an amplifier having a dc SQUID operating in a flux-locked loop for generating an amplified output as a function of the intensity of the signal generated by the sample. The flux-locked loop circuit includes an integrator. The amplifier also includes means for preventing the integrator from being driven into saturation. As a result, the time for the flux-locked loop to recover from the excitation pulses generated by the spectrometer is reduced. 7 figures.

DC superconducting quantum interference device usable in nuclear quadrupole resonance and zero field nuclear magnetic spectrometers

DOEpatents

Fan, Non Q.; Clarke, John

1993-01-01

A spectrometer for measuring the nuclear quadrupole resonance spectra or the zero-field nuclear magnetic resonance spectra generated by a sample is disclosed. The spectrometer uses an amplifier having a dc SQUID operating in a flux-locked loop for generating an amplified output as a function of the intensity of the signal generated by the sample. The flux-locked loop circuit includes an integrator. The amplifier also includes means for preventing the integrator from being driven into saturation. As a result, the time for the flux-locked loop to recover from the excitation pulses generated by the spectrometer is reduced.

NASA GSFC Report on CCSDS Recommendations 2.1.8A B Minimum Earth Station Transmitter Frequency Resolution for Spacecraft Receiver Acquisition

NASA Technical Reports Server (NTRS)

Fong, Wai; Lee, Wing

2017-01-01

In Fall 2016, ESA presented paper SLS-RFM 16-10 documenting a possible issue with the frequency lock-in range specification in Recommendation 2.1.8A of typically 267 to 1067 Hz in considerings (b) from considerings (a) for loop bandwidths [2B(sub LO)] in the range of 200 to 800 Hz with a recommendation of 100 Hz step size for frequency sweeping. The paper calculated the lock-in range to be (+/-)266 to (+/-)1064 rad/s or (+/-)42 to (+/-)168 Hz. Also, Recommendation 2.1.8B has the same issue for considering (a) and (b), i.e. for 2B(sub LO) =10 Hz, a lock-in range of 13 Hz was specified and a recommendation of 5 Hz step size for frequency sweeping. ESA also provided test results from the Rosetta and Exomars transponders. The results were somewhat inconsistent since the tests to verify lock-in and pull-in range did not include acquisition time, which is vital to the definition of these performance measures. This paper will address these test results below. However, we first examine the rationale for Recommendation 2.1.8A/B and its consistency with the theory of 2nd order phase lock loop operations. Our approach is to design a digital phase locked loop (DPLL) from phase locked loop (PLL) requirements. All analysis will be performed with a DPLL.

Method of implementing digital phase-locked loops

NASA Technical Reports Server (NTRS)

Stephens, Scott A. (Inventor); Thomas, Jess Brooks, Jr. (Inventor)

1993-01-01

In a new formulation for digital phase-locked loops, loop-filter constants are determined from loop roots that can each be selectively placed in the s-plane on the basis of a new set of parameters, each with simple and direct physical meaning in terms of loop noise bandwidth, root-specific decay rate, or root-specific damping. Loops of first to fourth order are treated in the continuous-update approximation (BLT yields 0) and in a discrete-update formulation with arbitrary BLT. Deficiencies of the continuous-update approximation in large-BLT applications are avoided in the new discrete-update formulation. A new method for direct, transient-free acquisition with third- and fourth-order loops can improve the versatility and reliability of acquisition with such loops.

Phase-locked tracking loops for LORAN-C

NASA Technical Reports Server (NTRS)

Burhans, R. W.

1978-01-01

Portable battery operated LORAN-C receivers were fabricated to evaluate simple envelope detector methods with hybrid analog to digital phase locked loop sensor processors. The receivers are used to evaluate LORAN-C in general aviation applications. Complete circuit details are given for the experimental sensor and readout system.

Foundry fabricated photonic integrated circuit optical phase lock loop.

PubMed

Bałakier, Katarzyna; Fice, Martyn J; Ponnampalam, Lalitha; Graham, Chris S; Wonfor, Adrian; Seeds, Alwyn J; Renaud, Cyril C

2017-07-24

This paper describes the first foundry-based InP photonic integrated circuit (PIC) designed to work within a heterodyne optical phase locked loop (OPLL). The PIC and an external electronic circuit were used to phase-lock a single-line semiconductor laser diode to an incoming reference laser, with tuneable frequency offset from 4 GHz to 12 GHz. The PIC contains 33 active and passive components monolithically integrated on a single chip, fully demonstrating the capability of a generic foundry PIC fabrication model. The electronic part of the OPLL consists of commercially available RF components. This semi-packaged system stabilizes the phase and frequency of the integrated laser so that an absolute frequency, high-purity heterodyne signal can be generated when the OPLL is in operation, with phase noise lower than -100 dBc/Hz at 10 kHz offset from the carrier. This is the lowest phase noise level ever demonstrated by monolithically integrated OPLLs.

Vortex spin-torque oscillator stabilized by phase locked loop using integrated circuits

NASA Astrophysics Data System (ADS)

Kreissig, Martin; Lebrun, R.; Protze, F.; Merazzo-Jaimes, K.; Hem, J.; Vila, L.; Ferreira, R.; Cyrille, M.-C.; Ellinger, F.; Cros, V.; Ebels, U.; Bortolotti, P.

2017-05-01

Spin-torque nano-oscillators (STO) are candidates for the next technological implementation of spintronic devices in commercial electronic systems. For use in microwave applications, improving the noise figures by efficient control of their phase dynamics is a mandatory requirement. In order to achieve this, we developed a compact phase locked loop (PLL) based on custom integrated circuits (ICs) and demonstrate that it represents an efficient way to reduce the phase noise level of a vortex based STO. The advantage of our approach to phase stabilize STOs is that our compact system is highly reconfigurable e.g. in terms of the frequency divider ratio N, RF gain and loop gain. This makes it robust against device to device variations and at the same time compatible with a large range of STOs. Moreover, by taking advantage of the natural highly non-isochronous nature of the STO, the STO frequency can be easily controlled by e.g. changing the divider ratio N.

Quartz tuning fork-based frequency modulation atomic force spectroscopy and microscopy with all digital phase-locked loop

NASA Astrophysics Data System (ADS)

An, Sangmin; Hong, Mun-heon; Kim, Jongwoo; Kwon, Soyoung; Lee, Kunyoung; Lee, Manhee; Jhe, Wonho

2012-11-01

We present a platform for the quartz tuning fork (QTF)-based, frequency modulation atomic force microscopy (FM-AFM) system for quantitative study of the mechanical or topographical properties of nanoscale materials, such as the nano-sized water bridge formed between the quartz tip (˜100 nm curvature) and the mica substrate. A thermally stable, all digital phase-locked loop is used to detect the small frequency shift of the QTF signal resulting from the nanomaterial-mediated interactions. The proposed and demonstrated novel FM-AFM technique provides high experimental sensitivity in the measurement of the viscoelastic forces associated with the confined nano-water meniscus, short response time, and insensitivity to amplitude noise, which are essential for precision dynamic force spectroscopy and microscopy.

Quartz tuning fork-based frequency modulation atomic force spectroscopy and microscopy with all digital phase-locked loop.

PubMed

An, Sangmin; Hong, Mun-heon; Kim, Jongwoo; Kwon, Soyoung; Lee, Kunyoung; Lee, Manhee; Jhe, Wonho

2012-11-01

We present a platform for the quartz tuning fork (QTF)-based, frequency modulation atomic force microscopy (FM-AFM) system for quantitative study of the mechanical or topographical properties of nanoscale materials, such as the nano-sized water bridge formed between the quartz tip (~100 nm curvature) and the mica substrate. A thermally stable, all digital phase-locked loop is used to detect the small frequency shift of the QTF signal resulting from the nanomaterial-mediated interactions. The proposed and demonstrated novel FM-AFM technique provides high experimental sensitivity in the measurement of the viscoelastic forces associated with the confined nano-water meniscus, short response time, and insensitivity to amplitude noise, which are essential for precision dynamic force spectroscopy and microscopy.

A digital optical phase-locked loop for diode lasers based on field programmable gate array

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu Zhouxiang; Zhang Xian; Huang Kaikai

2012-09-15

We have designed and implemented a highly digital optical phase-locked loop (OPLL) for diode lasers in atom interferometry. The three parts of controlling circuit in this OPLL, including phase and frequency detector (PFD), loop filter and proportional integral derivative (PID) controller, are implemented in a single field programmable gate array chip. A structure type compatible with the model MAX9382/MCH12140 is chosen for PFD and pipeline and parallelism technology have been adapted in PID controller. Especially, high speed clock and twisted ring counter have been integrated in the most crucial part, the loop filter. This OPLL has the narrow beat notemore » line width below 1 Hz, residual mean-square phase error of 0.14 rad{sup 2} and transition time of 100 {mu}s under 10 MHz frequency step. A main innovation of this design is the completely digitalization of the whole controlling circuit in OPLL for diode lasers.« less

Frequency control circuit for all-digital phase-lock loops

NASA Technical Reports Server (NTRS)

Anderson, T. O.

1973-01-01

Phase-lock loop references all its operations to fixed high-frequency service clock operating at highest speed which digital circuits permit. Wide-range control circuit provides linear control of frequency of reference signal. It requires only two counters in combination with control circuit consisting only of flip-flop and gate.

Digital phase-locked loop

NASA Technical Reports Server (NTRS)

Cliff, R. A. (Inventor)

1975-01-01

An digital phase-locked loop is provided for deriving a loop output signal from an accumulator output terminal. A phase detecting exclusive OR gate is fed by the loop digital input and output signals. The output of the phase detector is a bi-level digital signal having a duty cycle indicative of the relative phase of the input and output signals. The accumulator is incremented at a first rate in response to a first output level of the phase detector and at a second rate in response to a second output level of the phase detector.

A class of optimum digital phase locked loops

NASA Technical Reports Server (NTRS)

Kumar, R.; Hurd, W. J.

1986-01-01

This paper presents a class of optimum digital filters for digital phase locked loops, for the important case in which the maximum update rate of the loop filter and numerically controlled oscillator (NCO) is limited. This case is typical when the loop filter is implemented in a microprocessor. In these situations, pure delay is encountered in the loop transfer function and thus the stability and gain margin of the loop are of crucial interest. The optimum filters designed for such situations are evaluated in terms of their gain margin for stability, dynamic error, and steady-state error performance. For situations involving considerably high phase dynamics an adaptive and programmable implementation is also proposed to obtain an overall optimum strategy.

Digital Phase Meter for a Laser Heterodyne Interferometer

NASA Technical Reports Server (NTRS)

Loya, Frank

2008-01-01

The Digital Phase Meter is based on a modified phase-locked loop. When phase alignment between the reference input and the phase-shifted metrological input is achieved, the loop locks and the phase shift of the digital phase shifter equals the phase difference that one seeks to measure. This digital phase meter is being developed for incorporation into a laser heterodyne interferometer in a metrological apparatus, but could also be adapted to other uses. Relative to prior phase meters of similar capability, including digital ones, this digital phase meter is smaller, less complex, and less expensive. The phase meter has been constructed and tested in the form of a field-programmable gate array (FPGA).

Highly integrated optical heterodyne phase-locked loop with phase/frequency detection.

PubMed

Lu, Mingzhi; Park, Hyunchul; Bloch, Eli; Sivananthan, Abirami; Bhardwaj, Ashish; Griffith, Zach; Johansson, Leif A; Rodwell, Mark J; Coldren, Larry A

2012-04-23

A highly-integrated optical phase-locked loop with a phase/frequency detector and a single-sideband mixer (SSBM) has been proposed and demonstrated for the first time. A photonic integrated circuit (PIC) has been designed, fabricated and tested, together with an electronic IC (EIC). The PIC integrates a widely-tunable sampled-grating distributed-Bragg-reflector laser, an optical 90 degree hybrid and four high-speed photodetectors on the InGaAsP/InP platform. The EIC adds a single-sideband mixer, and a digital phase/frequency detector, to provide single-sideband heterodyne locking from -9 GHz to 7.5 GHz. The loop bandwith is 400 MHz. © 2012 Optical Society of America

Digital Filters for Digital Phase-locked Loops

NASA Technical Reports Server (NTRS)

Simon, M.; Mileant, A.

1985-01-01

An s/z hybrid model for a general phase locked loop is proposed. The impact of the loop filter on the stability, gain margin, noise equivalent bandwidth, steady state error and time response is investigated. A specific digital filter is selected which maximizes the overall gain margin of the loop. This filter can have any desired number of integrators. Three integrators are sufficient in order to track a phase jerk with zero steady state error at loop update instants. This filter has one zero near z = 1.0 for each integrator. The total number of poles of the filter is equal to the number of integrators plus two.

Temperature feedback control for long-term carrier-envelope phase locking.

PubMed

Yun, Chenxia; Chen, Shouyuan; Wang, He; Chini, Michael; Chang, Zenghu

2009-09-20

We report a double feedback loop for the improvement of the carrier-envelope phase stabilization of a chirped mirror based femtosecond laser oscillator. By combining the control of the Ti:sapphire crystal temperature and the modulation of the pump power, the carrier envelope offset frequency, fCEO, was locked for close to 20 h, which is much longer than the typical phase stabilization time with only pump power modulation.

Domain Hierarchy and closed Loops (DHcL): a server for exploring hierarchy of protein domain structure

PubMed Central

Koczyk, Grzegorz; Berezovsky, Igor N.

2008-01-01

Domain hierarchy and closed loops (DHcL) (http://sitron.bccs.uib.no/dhcl/) is a web server that delineates energy hierarchy of protein domain structure and detects domains at different levels of this hierarchy. The server also identifies closed loops and van der Waals locks, which constitute a structural basis for the protein domain hierarchy. The DHcL can be a useful tool for an express analysis of protein structures and their alternative domain decompositions. The user submits a PDB identifier(s) or uploads a 3D protein structure in a PDB format. The results of the analysis are the location of domains at different levels of hierarchy, closed loops, van der Waals locks and their interactive visualization. The server maintains a regularly updated database of domains, closed loop and van der Waals locks for all X-ray structures in PDB. DHcL server is available at: http://sitron.bccs.uib.no/dhcl. PMID:18502776

Noncoherent pseudonoise code tracking performance of spread spectrum receivers

NASA Technical Reports Server (NTRS)

Simon, M. K.

1977-01-01

The optimum design and performance of two noncoherent PN tracking loop configurations, namely, the delay-locked loop and tau-dither loop, are described. In particular, the bandlimiting effects of the bandpass arm filters are considered by demonstrating that for a fixed data rate and data signal-to-noise ratio, there exists an optimum filter bandwidth in the sense of minimizing the loop's tracking jitter. Both the linear and nonlinear loop analyses are presented, and the region of validity of the former relative to the latter is indicated. In addition, numerical results are given for several filter types. For example, assuming ideal bandpass arm filters, it is shown that the tau-dither loop requires approximately 1 dB more signal-to-noise ratio than the delay-locked loop for equal rms tracking jitters.

Design and implementation of a hybrid digital phase-locked loop with a TMS320C25: An application to a transponder receiver breadboard

NASA Technical Reports Server (NTRS)

Yeh, H.-G.; Nguyen, T. M.

1994-01-01

Design, modeling, analysis, and simulation of a phase-locked loop (PLL) with a digital loop filter are presented in this article. A TMS320C25 digital signal processor (DSP) is used to implement this digital loop filter. In order to keep the compatibility, the main design goal was to replace the analog PLL (APLL) of the Deep-Space Transponder (DST) receiver breadboard's loop filter with a digital loop filter without changing anything else. This replacement results in a hybrid digital PLL (HDPLL). Both the original APLL and the designed HDPLL are Type I second-order systems. The real-time performance of the HDPLL and the receiver is provided and evaluated.

Phase locked loop synchronization for direct detection optical PPM communication systems

NASA Technical Reports Server (NTRS)

Chen, C. C.; Gardner, C. S.

1985-01-01

Receiver timing synchronization of an optical pulse position modulation (PPM) communication system can be achieved using a phase locked loop (PLL) if the photodetector output is properly processed. The synchronization performance is shown to improve with increasing signal power and decreasing loop bandwidth. Bit error rate (BER) of the PLL synchronized PPM system is analyzed and compared to that for the perfectly synchronized system. It is shown that the increase in signal power needed to compensate for the imperfect synchronization is small (less than 0.1 dB) for loop bandwidths less than 0.1% of the slot frequency.

Optical phase locked loop for transparent inter-satellite communications.

PubMed

Herzog, F; Kudielka, K; Erni, D; Bächtold, W

2005-05-16

A novel type of optical phase locked loop (OPLL), optimized for homodyne inter-satellite communication, is presented. The loop employs a conventional 180? 3 dB optical hybrid and an AC-coupled balanced front end. No residual carrier transmission is required for phase locking. The loop accepts analog as well as digital data and various modulation formats. The only requirement to the transmitted user signal is a constant envelope. Phase error extraction occurs through applying a small sinusoidal local oscillator (LO) phase disturbance, while measuring its impact on the power of the baseband output signal. First experimental results indicate a receiver sensitivity of 36 photons/bit (-55.7 dBm) for a BER of 10 ;-9, when transmitting a PRBS-31 signal at a data rate of 400 Mbit/s. The system setup employs diode-pumped Nd:YAG lasers at a wavelength of 1.06 mum.

Optical phase locked loop for transparent inter-satellite communications

NASA Astrophysics Data System (ADS)

Herzog, F.; Kudielka, K.; Erni, D.; Bächtold, W.

2005-05-01

A novel type of optical phase locked loop (OPLL), optimized for homodyne inter-satellite communication, is presented. The loop employs a conventional 180◦ 3 dB optical hybrid and an AC-coupled balanced front end. No residual carrier transmission is required for phase locking. The loop accepts analog as well as digital data and various modulation formats. The only requirement to the transmitted user signal is a constant envelope. Phase error extraction occurs through applying a small sinusoidal local oscillator (LO) phase disturbance, while measuring its impact on the power of the baseband output signal. First experimental results indicate a receiver sensitivity of 36 photons/bit (-55.7 dBm) for a BER of 10 ^-9, when transmitting a PRBS-31 signal at a data rate of 400 Mbit/s. The system setup employs diode-pumped Nd:YAG lasers at a wavelength of 1.06 μm.

Digital-only PLL with adaptive search step

NASA Astrophysics Data System (ADS)

Lin, Ming-Lang; Huang, Shu-Chuan; Liu, Jie-Cherng

2014-06-01

In this paper, an all-digital phase-locked loop (PLL) with adaptively controlled up/down counter serves as the loop filter is presented, and it is implemented on a field-programmable gate array. The detailed circuit of the adaptive up/down counter implementing the adaptive search algorithm is also given, in which the search step for frequency acquisition is adaptively scaled down in half until it is reduced to zero. The phase jitter of the proposed PLL can be lowered, yet keeping with fast lock-in time. Thus, the dilemma between the low phase jitter and fast lock-in time of the traditional PLL can be resolved. Simulation results and circuit implementation show that the locked count, phase jitter and lock-in time of the proposed PLL are consistent with the theoretical predictions.

RFI in hybrid loops - Simulation and experimental results.

NASA Technical Reports Server (NTRS)

Ziemer, R. E.; Nelson, D. R.; Raghavan, H. R.

1972-01-01

A digital simulation of an imperfect second-order hybrid phase-locked loop (HPLL) operating in radio frequency interference (RFI) is described. Its performance is characterized in terms of phase error variance and phase error probability density function (PDF). Monte-Carlo simulation is used to show that the HPLL can be superior to the conventional phase-locked loops in RFI backgrounds when minimum phase error variance is the goodness criterion. Similar experimentally obtained data are given in support of the simulation data.

The Performance of A Sampled Data Delay Lock Loop Implemented with a Kalman Loop Filter.

DTIC Science & Technology

1980-01-01

que for analysis is computer simulation. Other techniques include state variable techniques and z-transform methods. Since the Kalman filter is linear...LOGIC NOT SHOWN Figure 2. Block diagram of the sampled data delay lock loop (SDDLL) Es A/ A 3/A/ Figure 3. Sampled error voltage ( Es ) as a function of...from a sum of two components. The first component is the previous filtered es - timate advanced one step forward by the state transition matrix. The 8

The digital phase-locked loop as a near-optimum FM demodulator.

NASA Technical Reports Server (NTRS)

Kelly, C. N.; Gupta, S. C.

1972-01-01

This paper presents an approach to the optimum digital demodulation of a continuous-time FM signal using stochastic estimation theory. The primary result is a digital phase-locked loop realization possessing performance characteristics that approach those of the analog counterpart. Some practical considerations are presented and simulation results for a first-order message model are presented.

Modified nonlinear amplifying loop mirror for mode-locked fibre oscillators with record-high energy and high-average-power pulsed output

NASA Astrophysics Data System (ADS)

Kobtsev, Sergey; Ivanenko, Alexey; Smirnov, Sergey; Kokhanovsky, Alexey

2018-02-01

The present work proposes and studies approaches for development of new modified non-linear amplifying loop mirror (NALM) allowing flexible and dynamic control of their non-linear properties within a relatively broad range of radiation powers. Using two independently pumped active media in the loop reflector constitutes one of the most promising approaches to development of better NALM with nonlinear properties controllable independently of the intra-cavity radiation power. This work reports on experimental and theoretical studies of the proposed redesigned NALM allowing both a higher level of energy parameters of output generated by mode-locked fibre oscillators and new possibilities of switching among different mode-locked regimes.

Strain Insensitive Optical Phase Locked Loop

NASA Technical Reports Server (NTRS)

Egalon, Claudio Oliviera (Inventor); Rogowski, Robert S. (Inventor)

1996-01-01

An apparatus is provided to allow for quasi distributed sensing of strain within a test object. Strain insensitive fiber is used to deliver a light signal to a strain sensitive fiber in an optical phase locked loop sensor configuration. The use of strain insensitive delivery fiber allows for non-integrated measurements of strain without the use of expensive electronics such as those employed in ODTR techniques. The novelty of the present invention lies in the use of strain insensitive multimode fiber. The inventors had previously developed a similar sensor with strain insensitive fiber, however it was restricted to the use of single or few mode fibers. The use of an optical phase locked loop arrangement allows for the use of multimode strain insensitive fiber.

A fast-locking all-digital delay-locked loop for phase/delay generation in an FPGA

NASA Astrophysics Data System (ADS)

Zhujia, Chen; Haigang, Yang; Fei, Liu; Yu, Wang

2011-10-01

A fast-locking all-digital delay-locked loop (ADDLL) is proposed for the DDR SDRAM controller interface in a field programmable gate array (FPGA). The ADDLL performs a 90° phase-shift so that the data strobe (DQS) can enlarge the data valid window in order to minimize skew. In order to further reduce the locking time and to prevent the harmonic locking problem, a time-to-digital converter (TDC) is proposed. A duty cycle corrector (DCC) is also designed in the ADDLL to adjust the output duty cycle to 50%. The ADDLL, implemented in a commercial 0.13 μm CMOS process, occupies a total of 0.017 mm2 of active area. Measurement results show that the ADDLL has an operating frequency range of 75 to 350 MHz and a total delay resolution of 15 ps. The time interval error (TIE) of the proposed circuit is 60.7 ps.

A single chip 2 Gbit/s clock recovery subsystem for digital communications

NASA Astrophysics Data System (ADS)

Hickling, Ronald M.

A self-contained clock recovery/data resynchronizer phase locked loop (PLL) for use in microwave and fiber optic digital communications has been fabricated using GaAs integrated circuit technology. The IC contains the analog and digital components for the PLL: an edge-triggered phase detector based on a 1.2 GHz phase/frequency comparator, an op amp for creating the loop filter, and a VCO based on a differential source-coupled pair amplifier.

Phase noise reduction by optical phase-locked loop for a coherent bichromatic laser based on the injection-locking technique.

PubMed

Wu, C F; Yan, X S; Huang, J Q; Zhang, J W; Wang, L J

2018-01-01

We present a coherent bichromatic laser system with low phase noise. An optical injection process is used to generate coherent laser beams with a frequency difference of 9.192 631 77 GHz using an electro-optical modulator. An optical phase-locked loop is then applied to reduce the phase noise. The phase noise of the beat note is -41, -81, -98, -83, and -95 dBrad 2 /Hz at the offset frequencies of 1 Hz, 100 Hz, 1 kHz, 10 kHz, and 1 MHz, respectively. Compared to a system that uses optical injection alone, the phase noise is reduced by up to 20-30 dB in the low-frequency range, and the intermodulation effect on the continuous atomic clock is reduced by an order of magnitude. This configuration can adjust the intensities and polarizations of the laser beams independently and reduce the phase noise caused by environmental disturbances and optical injection, which may be useful for application to atomic coherence experiments.

Phase noise reduction by optical phase-locked loop for a coherent bichromatic laser based on the injection-locking technique

NASA Astrophysics Data System (ADS)

Wu, C. F.; Yan, X. S.; Huang, J. Q.; Zhang, J. W.; Wang, L. J.

2018-01-01

We present a coherent bichromatic laser system with low phase noise. An optical injection process is used to generate coherent laser beams with a frequency difference of 9.192 631 77 GHz using an electro-optical modulator. An optical phase-locked loop is then applied to reduce the phase noise. The phase noise of the beat note is -41, -81, -98, -83, and -95 dBrad2/Hz at the offset frequencies of 1 Hz, 100 Hz, 1 kHz, 10 kHz, and 1 MHz, respectively. Compared to a system that uses optical injection alone, the phase noise is reduced by up to 20-30 dB in the low-frequency range, and the intermodulation effect on the continuous atomic clock is reduced by an order of magnitude. This configuration can adjust the intensities and polarizations of the laser beams independently and reduce the phase noise caused by environmental disturbances and optical injection, which may be useful for application to atomic coherence experiments.

Response of an all digital phase-locked loop

NASA Technical Reports Server (NTRS)

Garodnick, J.; Greco, J.; Schilling, D. L.

1974-01-01

An all digital phase-locked loop (DPLL) is designed, analyzed, and tested. Three specific configurations are considered, generating first, second, and third order DPLL's; and it is found, using a computer simulation of a noise spike, and verified experimentally, that of these configurations the second-order system is optimum from the standpoint of threshold extension. This substantiates results obtained for analog PLL's.

Weak and Dynamic GNSS Signal Tracking Strategies for Flight Missions in the Space Service Volume

PubMed Central

Jing, Shuai; Zhan, Xingqun; Liu, Baoyu; Chen, Maolin

2016-01-01

Weak-signal and high-dynamics are of two primary concerns of space navigation using GNSS (Global Navigation Satellite System) in the space service volume (SSV). The paper firstly defines a reference assumption third-order phase-locked loop (PLL) as the baseline of an onboard GNSS receiver, and proves the incompetence of this conventional architecture. Then an adaptive four-state Kalman filter (KF)-based algorithm is introduced to realize the optimization of loop noise bandwidth, which can adaptively regulate its filter gain according to the received signal power and line-of-sight (LOS) dynamics. To overcome the matter of losing lock in weak-signal and high-dynamic environments, an open loop tracking strategy aided by an inertial navigation system (INS) is recommended, and the traditional maximum likelihood estimation (MLE) method is modified in a non-coherent way by reconstructing the likelihood cost function. Furthermore, a typical mission with combined orbital maneuvering and non-maneuvering arcs is taken as a destination object to test the two proposed strategies. Finally, the experiment based on computer simulation identifies the effectiveness of an adaptive four-state KF-based strategy under non-maneuvering conditions and the virtue of INS-assisted methods under maneuvering conditions. PMID:27598164

Weak and Dynamic GNSS Signal Tracking Strategies for Flight Missions in the Space Service Volume.

PubMed

Jing, Shuai; Zhan, Xingqun; Liu, Baoyu; Chen, Maolin

2016-09-02

Weak-signal and high-dynamics are of two primary concerns of space navigation using GNSS (Global Navigation Satellite System) in the space service volume (SSV). The paper firstly defines a reference assumption third-order phase-locked loop (PLL) as the baseline of an onboard GNSS receiver, and proves the incompetence of this conventional architecture. Then an adaptive four-state Kalman filter (KF)-based algorithm is introduced to realize the optimization of loop noise bandwidth, which can adaptively regulate its filter gain according to the received signal power and line-of-sight (LOS) dynamics. To overcome the matter of losing lock in weak-signal and high-dynamic environments, an open loop tracking strategy aided by an inertial navigation system (INS) is recommended, and the traditional maximum likelihood estimation (MLE) method is modified in a non-coherent way by reconstructing the likelihood cost function. Furthermore, a typical mission with combined orbital maneuvering and non-maneuvering arcs is taken as a destination object to test the two proposed strategies. Finally, the experiment based on computer simulation identifies the effectiveness of an adaptive four-state KF-based strategy under non-maneuvering conditions and the virtue of INS-assisted methods under maneuvering conditions.

Phase-locked-loop-based delay-line-free picosecond electro-optic sampling system

NASA Astrophysics Data System (ADS)

Lin, Gong-Ru; Chang, Yung-Cheng

2003-04-01

A delay-line-free, high-speed electro-optic sampling (EOS) system is proposed by employing a delay-time-controlled ultrafast laser diode as the optical probe. Versatile optoelectronic delay-time controllers (ODTCs) based on modified voltage-controlled phase-locked-loop phase-shifting technologies are designed for the laser. The integration of the ODTC circuit and the pulsed laser diode has replaced the traditional optomechanical delay-line module used in the conventional EOS system. This design essentially prevents sampling distortion from misalignment of the probe beam, and overcomes the difficulty in sampling free-running high-speed transients. The maximum tuning range, error, scanning speed, tuning responsivity, and resolution of the ODTC are 3.9π (700°), <5% deviation, 25-2405 ns/s, 0.557 ps/mV, and ˜1 ps, respectively. Free-running wave forms from the analog, digital, and pulsed microwave signals are sampled and compared with those measured by the commercial apparatus.

Real-time fringe pattern demodulation with a second-order digital phase-locked loop.

PubMed

Gdeisat, M A; Burton, D R; Lalor, M J

2000-10-10

The use of a second-order digital phase-locked loop (DPLL) to demodulate fringe patterns is presented. The second-order DPLL has better tracking ability and more noise immunity than the first-order loop. Consequently, the second-order DPLL is capable of demodulating a wider range of fringe patterns than the first-order DPLL. A basic analysis of the first- and the second-order loops is given, and a performance comparison between the first- and the second-order DPLL's in analyzing fringe patterns is presented. The implementation of the second-order loop in real time on a commercial parallel image processing system is described. Fringe patterns are grabbed and processed, and the resultant phase maps are displayed concurrently.

A digitally implemented phase-locked loop detection scheme for analysis of the phase and power stability of a calibration tone

NASA Technical Reports Server (NTRS)

Densmore, A. C.

1988-01-01

A digital phase-locked loop (PLL) scheme is described which detects the phase and power of a high SNR calibration tone. The digital PLL is implemented in software directly from the given description. It was used to evaluate the stability of the Goldstone Deep Space Station open loop receivers for Radio Science. Included is a derivative of the Allan variance sensitivity of the PLL imposed by additive white Gaussian noise; a lower limit is placed on the carrier frequency.

Analysis and design of a second-order digital phase-locked loop

NASA Technical Reports Server (NTRS)

Blasche, P. R.

1979-01-01

A specific second-order digital phase-locked loop (DPLL) was modeled as a first-order Markov chain with alternatives. From the matrix of transition probabilities of the Markov chain, the steady-state phase error of the DPLL was determined. In a similar manner the loop's response was calculated for a fading input. Additionally, a hardware DPLL was constructed and tested to provide a comparison to the results obtained from the Markov chain model. In all cases tested, good agreement was found between the theoretical predictions and the experimental data.

Receiver concepts for data transmission at 10 microns

NASA Astrophysics Data System (ADS)

Scholtz, A. L.; Philipp, H. K.; Leeb, W. R.

1984-05-01

Receivers for digitally modulated CO2 laser signals are compared. Incoherent heterodyne receivers and coherent homodyne setups, including the linear phase locked loop (PLL) receiver, the low intermediate frequency translation loop, and the Costas loop receiver were studied. Experiments covered the homodyne systems, emphasizing the linear PLL receiver. Reliable phase lock of the receiver is achieved at carrier levels as low as 3 nW. Reception of signals phase shift keyed with a data rate of up to 150 Mbit/sec is demonstrated at subnanowatt sideband power levels.

Demonstration of a low bandwidth 1.06-micron optical phase-locked loop for coherent homodyne communication

NASA Technical Reports Server (NTRS)

Day, T.; Farinas, A. D.; Byer, R. L.

1990-01-01

A type II 1.06-micron optical phase-locked loop (OPLL) for use in a coherent homodyne receiver is discussed. Diode-laser-pumped solid-state lasers are used for both the local oscillator and transmitter, because their phase noise is significantly lower than that of diode lasers. Closed-loop RMS phase noise of less than 12 mrad (0.69 deg) is achieved, and modulation-demodulation in bulk modulators at rates from 20 kHz to 20 MHz with less than 19 deg of modulation depth is demonstrated.

Torque control for electric motors

NASA Technical Reports Server (NTRS)

Bernard, C. A.

1980-01-01

Method for adjusting electric-motor torque output to accomodate various loads utilizes phase-lock loop to control relay connected to starting circuit. As load is imposed, motor slows down, and phase lock is lost. Phase-lock signal triggers relay to power starting coil and generate additional torque. Once phase lock is recoverd, relay restores starting circuit to its normal operating mode.

An all digital phase locked loop for FM demodulation.

NASA Technical Reports Server (NTRS)

Greco, J.; Garodnick, J.; Schilling, D. L.

1972-01-01

A phase-locked loop designed with all-digital circuitry which avoids certain problems, and a digital voltage controlled oscillator algorithm are described. The system operates synchronously and performs all required digital calculations within one sampling period, thereby performing as a real-time special-purpose computer. The SNR ratio is computed for frequency offsets and sinusoidal modulation, and experimental results verify the theoretical calculations.

On the effects of phase jitter on QPSK lock detection

NASA Technical Reports Server (NTRS)

Mileant, A.; Hinedi, S.

1993-01-01

The performance of a QPSK (quadrature phase-shift keying) lock detector is described, taking into account the degradation due to carrier phase jitter. Such an analysis is necessary for accurate performance prediction purposes in scenarios where both the loop SNR is low and the estimation period is short. The derived formulas are applicable to several QPSK loops and are verified using computer simulations.

Complementary frequency shifter based on polarization modulator used for generation of a high-quality frequency-locked multicarrier.

PubMed

Li, Jianping; Yu, Changyuan; Li, Zhaohui

2014-03-15

A novel polarization-modulator-based complementary frequency shifter (PCFS) has been proposed and then used to implement the generation of a frequency-locked multicarrier with single- and dual-recirculating frequency shifting loops, respectively. The transfer functions and output properties of PCFS and PCFS-based multicarrier generator have been studied theoretically. Based on our simulation results through VPItransmissionMaker software, 100 stable carriers have been obtained with acceptable flatness while no DC bias control is required. The results show that the proposed PCFS has the potential to become a commercial product and then used in various scenarios.

A Phase-Locked Loop Model of the Response of the Postural Control System to Periodic Platform Motion

PubMed Central

Schilling, Robert J.; Robinson, Charles J.

2010-01-01

A phase-locked loop (PLL) model of the response of the postural control system to periodic platform motion is proposed. The PLL model is based on the hypothesis that quiet standing (QS) postural sway can be characterized as a weak sinusoidal oscillation corrupted with noise. Because the signal to noise ratio is quite low, the characteristics of the QS oscillator are not measured directly from the QS sway, instead they are inferred from the response of the oscillator to periodic motion of the platform. When a sinusoidal stimulus is applied, the QS oscillator changes speed as needed until its frequency matches that of the platform, thus achieving phase lock in a manner consistent with a PLL control mechanism. The PLL model is highly effective in representing the frequency, amplitude, and phase shift of the sinusoidal component of the phase-locked response over a range of platform frequencies and amplitudes. Qualitative analysis of the PLL control mechanism indicates that there is a finite range of frequencies over which phase lock is possible, and that the size of this capture range decreases with decreasing platform amplitude. The PLL model was tested experimentally using nine healthy subjects and the results reveal good agreement with a mean phase shift error of 13.7° and a mean amplitude error of 0.8 mm. PMID:20378479

Fringe pattern demodulation with a two-frame digital phase-locked loop algorithm.

PubMed

Gdeisat, Munther A; Burton, David R; Lalor, Michael J

2002-09-10

A novel technique called a two-frame digital phase-locked loop for fringe pattern demodulation is presented. In this scheme, two fringe patterns with different spatial carrier frequencies are grabbed for an object. A digital phase-locked loop algorithm tracks and demodulates the phase difference between both fringe patterns by employing the wrapped phase components of one of the fringe patterns as a reference to demodulate the second fringe pattern. The desired phase information can be extracted from the demodulated phase difference. We tested the algorithm experimentally using real fringe patterns. The technique is shown to be suitable for noncontact measurement of objects with rapid surface variations, and it outperforms the Fourier fringe analysis technique in this aspect. Phase maps produced withthis algorithm are noisy in comparison with phase maps generated with the Fourier fringe analysis technique.

Low-cost, digital lock-in module with external reference for coating glass transmission/reflection spectrophotometer

NASA Astrophysics Data System (ADS)

Alonso, R.; Villuendas, F.; Borja, J.; Barragán, L. A.; Salinas, I.

2003-05-01

A versatile, low-cost, digital signal processor (DSP) based lock-in module with external reference is described. This module is used to implement an industrial spectrophotometer for measuring spectral transmission and reflection of automotive and architectonic coating glasses over the ultraviolet, visible and near-infrared wavelength range. The light beams are modulated with an optical chopper. A digital phase-locked loop (DPLL) is used to lock the lock-in to the chop frequency. The lock-in rejects the ambient radiation and permits the spectrophotometer to work in the presence of ambient light. The algorithm that implements the dual lock-in and the DPLL in the DSP56002 evaluation module from Motorola is described. The use of a DSP allows implementation of the lock-in and DPLL by software, which gives flexibility and programmability to the system. Lock-in module cost, under 300 euro, is an important parameter taking into account that two modules are used in the system. Besides, the algorithms implemented in this DSP can be directly implemented in the latest DSP generations. The DPLL performance and the spectrophotometer are characterized. Capture and lock DPLL ranges have been measured and checked to be greater than the chop frequency drifts. The lock-in measured frequency response shows that the lock-in performs as theoretically predicted.

Solid State Research

DTIC Science & Technology

1985-08-15

Hz. The high-speed performance is consis- tent with the low stage delay observed in the ring-oscillator measurements , and the low - frequency ...Phase-Locked Loop 41 5-10 Phase-Locked-Loop Output Spectrum . Note that a 10-kHz Measure - ment Bandwidth Is Used. 42 5-11 Phase Error Response to an...the niobium. Reflections of bulk acoustic waves from optically generated holograms in Fe-doped LiNb03 have been observed and measured . Holographic

Sensing and Timekeeping Using A Light Trapping

DTIC Science & Technology

2017-06-01

bioassays, condensed matter physics, mate- rial science, biothermometry, bulk magnetometry for surveying, and hyper -polarized media for NMR. 1.3.2...obtained under continuous-wave (CW) microwave field excitation when a 3 mm diameter loop of 200 µm-diameter wire is placed 5 mm above the LTDW. An...frequency-locking technique was also developed to monitor both resonances simultaneously. A closed- loop system that locks to the center frequency of

Performance Analysis of a De-correlated Modified Code Tracking Loop for Synchronous DS-CDMA System under Multiuser Environment

NASA Astrophysics Data System (ADS)

Wu, Ya-Ting; Wong, Wai-Ki; Leung, Shu-Hung; Zhu, Yue-Sheng

This paper presents the performance analysis of a De-correlated Modified Code Tracking Loop (D-MCTL) for synchronous direct-sequence code-division multiple-access (DS-CDMA) systems under multiuser environment. Previous studies have shown that the imbalance of multiple access interference (MAI) in the time lead and time lag portions of the signal causes tracking bias or instability problem in the traditional correlating tracking loop like delay lock loop (DLL) or modified code tracking loop (MCTL). In this paper, we exploit the de-correlating technique to combat the MAI at the on-time code position of the MCTL. Unlike applying the same technique to DLL which requires an extensive search algorithm to compensate the noise imbalance which may introduce small tracking bias under low signal-to-noise ratio (SNR), the proposed D-MCTL has much lower computational complexity and exhibits zero tracking bias for the whole range of SNR, regardless of the number of interfering users. Furthermore, performance analysis and simulations based on Gold codes show that the proposed scheme has better mean square tracking error, mean-time-to-lose-lock and near-far resistance than the other tracking schemes, including traditional DLL (T-DLL), traditional MCTL (T-MCTL) and modified de-correlated DLL (MD-DLL).

2 µm high-power dissipative soliton resonance in a compact σ-shaped Tm-doped double-clad fiber laser

NASA Astrophysics Data System (ADS)

Du, Tuanjie; Li, Weiwei; Ruan, Qiujun; Wang, Kaijie; Chen, Nan; Luo, Zhengqian

2018-05-01

We report direct generation of a high-power, large-energy dissipative soliton resonance (DSR) in a 2 µm Tm-doped double-clad fiber laser. A compact σ-shaped cavity is formed by a fiber Bragg grating and a 10/90 fiber loop mirror (FLM). The 10/90 FLM is not only used as an output mirror, but also acts as a nonlinear optical loop mirror for initiating mode locking. The mode-locked laser can deliver high-power, nanosecond DSR pulses at 2005.9 nm. We further perform a comparison study of the effect of the FLM’s loop length on the mode-locking threshold, peak power, pulse energy, and optical spectrum of the DSR pulses. We achieve a maximum average output power as high as 1.4 W, a maximum pulse energy of 353 nJ, and a maximum peak power of 84 W. This is, to the best of our knowledge, the highest power for 2 µm DSR pulses obtained in a mode-locked fiber laser.

Digital approach to stabilizing optical frequency combs and beat notes of CW lasers

NASA Astrophysics Data System (ADS)

Čížek, Martin; Číp, Ondřej; Å míd, Radek; Hrabina, Jan; Mikel, Břetislav; Lazar, Josef

2013-10-01

In cases when it is necessary to lock optical frequencies generated by an optical frequency comb to a precise radio frequency (RF) standard (GPS-disciplined oscillator, H-maser, etc.) the usual practice is to implement phase and frequency-locked loops. Such system takes the signal generated by the RF standard (usually 10 MHz or 100 MHz) as a reference and stabilizes the repetition and offset frequencies of the comb contained in the RF output of the f-2f interferometer. These control loops are usually built around analog electronic circuits processing the output signals from photo detectors. This results in transferring the stability of the standard from RF to optical frequency domain. The presented work describes a different approach based on digital signal processing and software-defined radio algorithms used for processing the f-2f and beat-note signals. Several applications of digital phase and frequency locks to a RF standard are demonstrated: the repetition (frep) and offset frequency (fceo) of the comb, and the frequency of the beat note between a CW laser source and a single component of the optical frequency comb spectrum.

Short Range 10 Gb/s THz Communications. Proof of Concept Phase 2

DTIC Science & Technology

2011-12-01

heterodyned are phase locked to spectral lines selected from the optical frequency comb generator (OFCG) using optical phase locked loops ( OPLLs ) or by...systems by optical heterodyne generation (OHG), in which the outputs of two phase - locked lasers are combined, and detection in a fast photodiode, such... Heterodyning of two CW optical signals, each phase locked to lines in an

A second-order all-digital phase-locked loop

NASA Technical Reports Server (NTRS)

Holmes, J. K.; Tegnelia, C. R.

1974-01-01

A simple second-order digital phase-locked loop has been designed to synchronize itself to a square-wave subcarrier. Analysis and experimental performance are given for both acquisition behavior and steady-state phase error performance. In addition, the damping factor and the noise bandwidth are derived analytically. Although all the data are given for the square-wave subcarrier case, the results are applicable to arbitrary subcarriers that are odd symmetric about their transition region.

Direct generation of 128-fs Gaussian pulses from a compensation-free fiber laser using dual mode-locking mechanisms

NASA Astrophysics Data System (ADS)

Peng, Junsong; Zhan, Li; Gu, Zhaochang; Qian, Kai; Luo, Shouyu; Shen, Qishun

2012-03-01

We have experimentally demonstrated the direct generation of 128-fs pulses in an all-anomalous-dispersion all-fiber mode-locked laser. The laser is free of dispersion compensation in the cavity based on standard single mode fiber (SMF). The time-bandwidth product is 0.536. The laser is achieved by using two mode-lockers, one is nonlinear polarization rotation (NPR), and the other is nonlinear amplifying loop mirror. The coexistence of dual mode-locking mechanisms can decrease the cavity length to 12-m, and also results in producing high-quality pulses with a Gaussian shape both on the pulse profile and spectrum, but without Kelly sidebands.

Design and Measurement of a Digital Phase Locked BWO for Accurately Extracting the Quality Factors in a Biconcave Resonator System

NASA Astrophysics Data System (ADS)

Gao, Yuanci; Charles, Jones R.; Yu, Guofen; Jyotsna, Dutta M.

2012-03-01

A long loop phase locked backward-wave oscillator (BWO) for a high quality factor resonator system operating at D-band frequencies (130-170GHz) was described, the phase noise of the phased locked BWO was analyzed and measured at typical frequencies. When it used with a high quality factor open resonator for measuring the quality factor of simple harmonic resonators based on the magnitude transfer characteristic, this system has proven to be capable of accurate measuring the quality factor as high as 0.8 million with an uncertainty of less than 1.3% (Lorentzian fitting) at typical frequencies in the range of 130GHz-170GHz.

Space Shuttle program communication and tracking systems interface analysis

NASA Technical Reports Server (NTRS)

Dodds, J. G.; Holmes, J. K.; Huth, G. K.; Iwasaki, R. S.; Nilsen, P. W.; Polydoros, A.; Sampaio, D. R.; Udalov, S.

1984-01-01

The Space Shuttle Program Communications and Tracking Systems Interface Analysis began April 18, 1983. During this time, the shuttle communication and tracking systems began flight testing. Two areas of analysis documented were a result of observations made during flight tests. These analyses involved the Ku-band communication system. First, there was a detailed analysis of the interface between the solar max data format and the Ku-band communication system including the TDRSS ground station. The second analysis involving the Ku-band communication system was an analysis of the frequency lock loop of the Gunn oscillator used to generate the transmit frequency. The stability of the frequency lock loop was investigated and changes to the design were reviewed to alleviate the potential loss of data due the loop losing lock and entering the reacquisition mode. Other areas of investigation were the S-band antenna analysis and RF coverage analysis.

A method for reducing sampling jitter in digital control systems

NASA Technical Reports Server (NTRS)

Anderson, T. O.; HURBD W. J.; Hurd, W. J.

1969-01-01

Digital phase lock loop system is designed by smoothing the proportional control with a low pass filter. This method does not significantly affect the loop dynamics when the smoothing filter bandwidth is wide compared to loop bandwidth.

Constant frequency pulsed phase-locked-loop instrument for measurement of ultrasonic velocity

NASA Technical Reports Server (NTRS)

Yost, William T.; Cantrell, John H.; Kushnick, Peter W.

1991-01-01

A new instrument based on a constant-frequency pulsed phase-locked-loop (CFPPLL) concept has been developed to accurately measure the ultrasonic wave velocity in liquids and changes in ultrasonic wave velocity in solids and liquids. An analysis of the system shows that it is immune to many of the frequency-dependent effects that plague other techniques. Measurements of the sound velocity in ultrapure water are used to confirm the analysis. The results are in excellent agreement with values from the literature, and establish that the CFPPLL provides a reliable, accurate way to measure velocities, as well as for monitoring small changes in velocity without the sensitivity to frequency-dependent phase shifts common to other measurement systems. The estimated sensitivity to phase changes is better than a few parts in 10 to the 7th.

Generation of “gigantic” ultra-short microwave pulses based on passive mode-locking effect in electron oscillators with saturable absorber in the feedback loop

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ginzburg, N. S., E-mail: ginzburg@appl.sci-nnov.ru; Denisov, G. G.; Vilkov, M. N.

2016-05-15

A periodic train of powerful ultrashort microwave pulses can be generated in electron oscillators with a non-linear saturable absorber installed in the feedback loop. This method of pulse formation resembles the passive mode-locking widely used in laser physics. Nevertheless, there is a specific feature in the mechanism of pulse amplification when consecutive energy extraction from different fractions of a stationary electron beam takes place due to pulse slippage over the beam caused by the difference between the wave group velocity and the electron axial velocity. As a result, the peak power of generated “gigantic” pulses can exceed not only themore » level of steady-state generation but also, in the optimal case, the power of the driving electron beam.« less

Improved performance of a digital phase-locked loop combined with a frequency/frequency-rate estimator

NASA Technical Reports Server (NTRS)

Mileant, A.; Simon, M.

1986-01-01

When a digital phase-locked loop with a long loop update time tracks a signal with high Doppler, the demodualtion losses due to frequency mismatch can become very significant. One way of reducing these Doppler-related losses is to compensate for the Doppler effect using some kind of frequency-rate estimator. The performance of the fixed-window least-squares estimator and the Kalman filter is investigated; several Doppler compensating techniques are proposed. It is shown that the variance of the frequency estimator can be made as small as desired, and with this, the Doppler effect can be effectively compensated. The remaining demodulation losses due to phase jitter in the loop can be less than 0.1 dB.

Discriminator aided phase lock acquisition for suppressed carrier signals

NASA Technical Reports Server (NTRS)

Carson, L. M.; Krasin, F. E. (Inventor)

1982-01-01

A discriminator aided technique for acquisition of phase lock to a suppressed carrier signal utilizes a Costas loop which is initially operated open loop and control voltage for its VCXO is derived from a phase detector that compares the VCXO to a reference frequency thus establishing coarse frequency resolution with the received signal. Then the Costas loop is closed with the low-pass filter of the channel having a bandwidth much greater (by a factor of about 10) than in the I channel so that a frequency discriminator effect results to aid carrier resolution. Finally, after carrier acquisition, the Q-channel filter of the Costas loop is switched to a bandwidth substantially equal to that of the I-channel for carrier tracking.

Ultrahigh-speed phaselocked-loop type clock recovery circuit using a travelling-wave laser diode amplifier as a 50 GHz phase detector

NASA Astrophysics Data System (ADS)

Kawanishi, S.; Takara, H.; Saruwatari, M.; Kitoh, T.

1993-09-01

Successful operation of a phase-locked loop is demonstrated using a traveling-wave laser-diode amplifier as a 50 GHz phase detector. Optical gain modulation in the laser diode amplifier and an all-optical clock multiplication technique using a silica-based guided-wave optical circuit are used to achieve the extremely high-speed operation. Also discussed is the possibility of more than 100 GHz operation.

Evolution of the Generic Lock System at Jefferson Lab

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brian Bevins; Yves Roblin

2003-10-13

The Generic Lock system is a software framework that allows highly flexible feedback control of large distributed systems. It allows system operators to implement new feedback loops between arbitrary process variables quickly and with no disturbance to the underlying control system. Several different types of feedback loops are provided and more are being added. This paper describes the further evolution of the system since it was first presented at ICALEPCS 2001 and reports on two years of successful use in accelerator operations. The framework has been enhanced in several key ways. Multiple-input, multiple-output (MIMO) lock types have been added formore » accelerator orbit and energy stabilization. The general purpose Proportional-Integral-Derivative (PID) locks can now be tuned automatically. The generic lock server now makes use of the Proxy IOC (PIOC) developed at Jefferson Lab to allow the locks to be monitored from any EPICS Channel Access aware client. (Previously clients had to be Cdev aware.) The dependency on the Qt XML parser has been replaced with the freely available Xerces DOM parser from the Apache project.« less

Photonic generation of phase-stable and wideband chirped microwave signals based on phase-locked dual optical frequency combs.

PubMed

Tong, Yitian; Zhou, Qian; Han, Daming; Li, Baiyu; Xie, Weilin; Liu, Zhangweiyi; Qin, Jie; Wang, Xiaocheng; Dong, Yi; Hu, Weisheng

2016-08-15

A photonics-based scheme is presented for generating wideband and phase-stable chirped microwave signals based on two phase-locked combs with fixed and agile repetition rates. By tuning the difference of the two combs' repetition rates and extracting different order comb tones, a wideband linearly frequency-chirped microwave signal with flexible carrier frequency and chirped range is obtained. Owing to the scheme of dual-heterodyne phase transfer and phase-locked loop, extrinsic phase drift and noise induced by the separated optical paths is detected and suppressed efficiently. Linearly frequency-chirped microwave signals from 5 to 15 GHz and 237 to 247 GHz with 30 ms duration are achieved, respectively, contributing to the time-bandwidth product of 3×10⁸. And less than 1.3×10^-5 linearity errors (RMS) are also obtained.

False lock performance in polarity-type Costas receivers in the presence of periodic data patterns

NASA Technical Reports Server (NTRS)

Wang, James June-Ming; Lai, Dennis Teng-Tsun; Heng, Veronica Siang-Gek; Godfrey, Robert D.

1987-01-01

The authors address the false-lock performance of receivers which use polarity-type Costas loops for the carrier recovery of unbalanced quadrature phase-shift keyed (QPSK), asynchronous QPSK or binary PSK (BPSK) signals in the presence of periodic data patterns. The potential false-lock frequencies are first identified. Expressions for both true-lock and false-lock components are also derived, thereby allowing numerical evaluation of various key parameters for cases of practical interest.

Detection of digital FSK using a phase-locked loop

NASA Technical Reports Server (NTRS)

Lindsey, W. C.; Simon, M. K.

1975-01-01

A theory is presented for the design of a digital FSK receiver which employs a phase-locked loop to set up the desired matched filter as the arriving signal frequency switches. The developed mathematical model makes it possible to establish the error probability performance of systems which employ a class of digital FM modulations. The noise mechanism which accounts for decision errors is modeled on the basis of the Meyr distribution and renewal Markov process theory.

An adaptive narrow band frequency modulation voice communication system

NASA Technical Reports Server (NTRS)

Wishna, S.

1972-01-01

A narrow band frequency modulation communication system is described which provides for the reception of good quality voice at low carrier-to-noise ratios. The high level of performance is obtained by designing a limiter and phase lock loop combination as a demodulator, so that the bandwidth of the phase lock loop decreases as the carrier level decreases. The system was built for the position location and aircraft communication equipment experiment of the ATS 6 program.

Performance of the all-digital data-transition tracking loop in the advanced receiver

NASA Astrophysics Data System (ADS)

Cheng, U.; Hinedi, S.

1989-11-01

The performance of the all-digital data-transition tracking loop (DTTL) with coherent or noncoherent sampling is described. The effects of few samples per symbol and of noncommensurate sampling rates and symbol rates are addressed and analyzed. Their impacts on the loop phase-error variance and the mean time to lose lock (MTLL) are quantified through computer simulations. The analysis and preliminary simulations indicate that with three to four samples per symbol, the DTTL can track with negligible jitter because of the presence of earth Doppler rate. Furthermore, the MTLL is also expected to be large engough to maintain lock over a Deep Space Network track.

Phase noise mitigation of QPSK signal utilizing phase-locked multiplexing of signal harmonics and amplitude saturation.

PubMed

Mohajerin-Ariaei, Amirhossein; Ziyadi, Morteza; Chitgarha, Mohammad Reza; Almaiman, Ahmed; Cao, Yinwen; Shamee, Bishara; Yang, Jeng-Yuan; Akasaka, Youichi; Sekiya, Motoyoshi; Takasaka, Shigehiro; Sugizaki, Ryuichi; Touch, Joseph D; Tur, Moshe; Langrock, Carsten; Fejer, Martin M; Willner, Alan E

2015-07-15

We demonstrate an all-optical phase noise mitigation scheme based on the generation, delay, and coherent summation of higher order signal harmonics. The signal, its third-order harmonic, and their corresponding delayed variant conjugates create a staircase phase-transfer function that quantizes the phase of quadrature-phase-shift-keying (QPSK) signal to mitigate phase noise. The signal and the harmonics are automatically phase-locked multiplexed, avoiding the need for phase-based feedback loop and injection locking to maintain coherency. The residual phase noise converts to amplitude noise in the quantizer stage, which is suppressed by parametric amplification in the saturation regime. Phase noise reduction of ∼40% and OSNR-gain of ∼3  dB at BER 10(-3) are experimentally demonstrated for 20- and 30-Gbaud QPSK input signals.

Modeling Plasticity of Ni3Al-Based L12 Intermetallic Single Crystals-I. Anomalous Temperature Dependence of the Flow Behavior (Preprint)

DTIC Science & Technology

2006-07-01

dislocation-loop expansion . The new model was used to simulate the thermally reversible flow behaviour for C-S type two-step deformation, and the results are...implemented into the finite element software ABAQUS through a User MATerial subroutine (UMAT). A tangent modulus method [48] was used for the time...locking under a dislocation loop- expansion configuration. This approach was motivated by modern understanding of dislocation mechanisms for Ni3Al

Steady-state phase error for a phase-locked loop subjected to periodic Doppler inputs

NASA Technical Reports Server (NTRS)

Chen, C.-C.; Win, M. Z.

1991-01-01

The performance of a carrier phase locked loop (PLL) driven by a periodic Doppler input is studied. By expanding the Doppler input into a Fourier series and applying the linearized PLL approximations, it is easy to show that, for periodic frequency disturbances, the resulting steady state phase error is also periodic. Compared to the method of expanding frequency excursion into a power series, the Fourier expansion method can be used to predict the maximum phase error excursion for a periodic Doppler input. For systems with a large Doppler rate fluctuation, such as an optical transponder aboard an Earth orbiting spacecraft, the method can be applied to test whether a lower order tracking loop can provide satisfactory tracking and thereby save the effect of a higher order loop design.

Optical Injection Locking of a VCSEL in an OEO

NASA Technical Reports Server (NTRS)

Strekalov, Dmitry; Matsko, Andrey; Savchenkov, Anatoliy; Yu, Nan; Maleki, Lute

2009-01-01

Optical injection locking has been demonstrated to be effective as a means of stabilizing the wavelength of light emitted by a vertical-cavity surface- emitting laser (VCSEL) that is an active element in the frequency-control loop of an opto-electronic oscillator (OEO) designed to implement an atomic clock based on an electromagnetically- induced-transparency resonance. This particular optical-injection- locking scheme is expected to enable the development of small, low-power, high-stability atomic clocks that would be suitable for use in applications involving precise navigation and/or communication. In one essential aspect of operation of an OEO of the type described above, a microwave modulation signal is coupled into the VCSEL. Heretofore, it has been well known that the wavelength of light emitted by a VCSEL depends on its temperature and drive current, necessitating thorough stabilization of these operational parameters. Recently, it was discovered that the wavelength also depends on the microwave power coupled into the VCSEL. Inasmuch as the microwave power circulating in the frequency-control loop is a dynamic frequency-control variable (and, hence, cannot be stabilized), there arises a need for another means of stabilizing the wavelength. The present optical-injection-locking scheme satisfies the need for a means to stabilize the wavelength against microwave- power fluctuations. It is also expected to afford stabilization against temperature and current fluctuations. In an experiment performed to demonstrate this scheme, wavelength locking was observed when about 200 W of the output power of a commercial tunable diode laser was injected into a commercial VCSEL, designed to operate in the wavelength range of 795+/-3 nm, that was generating about 200 microW of optical power. (The use of relatively high injection power levels is a usual practice in injection locking of VCSELs.)

Stabilization of self-mode-locked quantum dash lasers by symmetric dual-loop optical feedback

NASA Astrophysics Data System (ADS)

Asghar, Haroon; Wei, Wei; Kumar, Pramod; Sooudi, Ehsan; McInerney, John. G.

2018-02-01

We report experimental studies of the influence of symmetric dual-loop optical feedback on the RF linewidth and timing jitter of self-mode-locked two-section quantum dash lasers emitting at 1550 nm. Various feedback schemes were investigated and optimum levels determined for narrowest RF linewidth and low timing jitter, for single-loop and symmetric dual-loop feedback. Two symmetric dual-loop configurations, with balanced and unbalanced feedback ratios, were studied. We demonstrate that unbalanced symmetric dual loop feedback, with the inner cavity resonant and fine delay tuning of the outer loop, gives narrowest RF linewidth and reduced timing jitter over a wide range of delay, unlike single and balanced symmetric dual-loop configurations. This configuration with feedback lengths 80 and 140 m narrows the RF linewidth by 4-67x and 10-100x, respectively, across the widest delay range, compared to free-running. For symmetric dual-loop feedback, the influence of different power split ratios through the feedback loops was determined. Our results show that symmetric dual-loop feedback is markedly more effective than single-loop feedback in reducing RF linewidth and timing jitter, and is much less sensitive to delay phase, making this technique ideal for applications where robustness and alignment tolerance are essential.

Digital phase-locked-loop speed sensor for accuracy improvement in analog speed controls. [feedback control and integrated circuits

NASA Technical Reports Server (NTRS)

Birchenough, A. G.

1975-01-01

A digital speed control that can be combined with a proportional analog controller is described. The stability and transient response of the analog controller were retained and combined with the long-term accuracy of a crystal-controlled integral controller. A relatively simple circuit was developed by using phase-locked-loop techniques and total error storage. The integral digital controller will maintain speed control accuracy equal to that of the crystal reference oscillator.

System having unmodulated flux locked loop for measuring magnetic fields

DOEpatents

Ganther, Jr., Kenneth R.; Snapp, Lowell D [Blue Springs, MO

2006-08-15

A system (10) for measuring magnetic fields, wherein the system (10) comprises an unmodulated or direct-feedback flux locked loop (12) connected by first and second unbalanced RF coaxial transmission lines (16a, 16b) to a superconducting quantum interference device (14). The FLL (12) operates for the most part in a room-temperature or non-cryogenic environment, while the SQUID (14) operates in a cryogenic environment, with the first and second lines (16a, 16b) extending between these two operating environments.

Frequency-Domain Channel Estimation and Equalization for Single Carrier Underwater Acoustic Communications

DTIC Science & Technology

2007-01-01

synchronization ; vm(k) white Gaussian noise with average power σ2. If the Doppler shift f m,k is significant, then it causes the received signal ym(k) to be time ...intersymbol interference (ISI) to extend over 20-300 symbols at a data rate of 2-10 kilosymbols per second. Another obstacle is the time -varying Doppler... synchronization that employs a phase-locked loop (PLL) or delay-locked loop (DLL). However, the DFE and PLL/DLL have to interact in a nonlinear fashion

Digital phase-locked loop speed control for a brushless dc motor

NASA Astrophysics Data System (ADS)

Wise, M. G.

1985-06-01

Speed control of d.c. motors by phase-locked loops (PLL) is becoming increasingly popular. Primary interest has been in employing PLL for constant speed control. This thesis investigates the theory and techniques of digital PLL to speed control of a brushless d.c. motor with a variable speed of operation. Addition of logic controlled count enable/disable to a synchronous up/down counter, used as a phase-frequency detector, is shown to improve the performance of previously proposed PLL control schemes.

Frequency Stabilization of DFB Laser Diodes at 1572 nm for Spaceborne Lidar Measurements of CO2

NASA Technical Reports Server (NTRS)

Numata, Kenji; Chen, Jeffrey R.; Wu, Stewart T.; Abshire, James B.; Krainak, Michael A.

2010-01-01

We report a fiber-based, pulsed laser seeder system that rapidly switches among 6 wavelengths across atmospheric carbon dioxide (CO2) absorption line near 1572.3 nm for measurements of global CO2 mixing ratios to 1-ppmv precision. One master DFB laser diode has been frequency-locked to the CO2 line center using a frequency modulation technique, suppressing its peak-to-peak frequency drifts to 0.3 MHz at 0.8 sec averaging time over 72 hours. Four online DFB laser diodes have been offset-locked to the master laser using phase locked loops, with virtually the same sub-MHz absolute accuracy. The 6 lasers were externally modulated and then combined to produce the measurement pulse train.

Optical injection locking-based amplification in phase-coherent transfer of optical frequencies.

PubMed

Kim, Joonyoung; Schnatz, Harald; Wu, David S; Marra, Giuseppe; Richardson, David J; Slavík, Radan

2015-09-15

We demonstrate the use of an optical injection phase locked loop (OIPLL) as a regenerative amplifier for optical frequency transfer applications. The optical injection locking provides high gain within a narrow bandwidth (<100  MHz) and is capable of preserving the fractional frequency stability of the incoming carrier to better than 10(-18) at 1000 s. The OIPLL was tested in the field as a mid-span amplifier for the transfer of an ultrastable optical carrier, stabilized to an optical frequency standard, over a 292 km long installed dark fiber link. The transferred frequency at the remote end reached a fractional frequency instability of less than 1×10(-19) at averaging time of 3200 s.

Efficient carrier-envelope offset frequency stabilization through gain modulation via stimulated emission.

PubMed

Karlen, Lauriane; Buchs, Gilles; Portuondo-Campa, Erwin; Lecomte, Steve

2016-01-15

A novel scheme for intracavity control of the carrier-envelope offset (CEO) frequency of a 100 MHz mode-locked Er:Yb:glass diode-pumped solid-state laser (DPSSL) based on the modulation of the laser gain via stimulated emission of the excited Er(3+) ions is demonstrated. This method allows us to bypass the ytterbium system few-kHz low-pass filter in the f(CEO) stabilization loop and thus to push the phase lock bandwidth up to a limit close to the relaxation oscillations frequency of the erbium system. A phase lock bandwidth above 70 kHz has been achieved with the fully stabilized laser, leading to an integrated phase noise [1 Hz-1 MHz] of 120 mrad.

Methods and apparatus for broadband frequency comb stabilization

DOEpatents

Cox, Jonathan A; Kaertner, Franz X

2015-03-17

Feedback loops can be used to shift and stabilize the carrier-envelope phase of a frequency comb from a mode-locked fibers laser or other optical source. Compared to other frequency shifting and stabilization techniques, feedback-based techniques provide a wideband closed-loop servo bandwidth without optical filtering, beam pointing errors, or group velocity dispersion. It also enables phase locking to a stable reference, such as a Ti:Sapphire laser, continuous-wave microwave or optical source, or self-referencing interferometer, e.g., to within 200 mrad rms from DC to 5 MHz. In addition, stabilized frequency combs can be coherently combined with other stable signals, including other stabilized frequency combs, to synthesize optical pulse trains with pulse durations of as little as a single optical cycle. Such a coherent combination can be achieved via orthogonal control, using balanced optical cross-correlation for timing stabilization and balanced homodyne detection for phase stabilization.

Free-space laser communication technologies IV; Proceedings of the 4th Conference, Los Angeles, CA, Jan. 23, 24, 1992

NASA Technical Reports Server (NTRS)

Begley, David L. (Editor); Seery, Bernard D. (Editor)

1992-01-01

Papers included in this volume are grouped under topics of receivers; laser transmitters; components; system analysis, performance, and applications; and beam control (pointing, acquisition, and tracking). Papers are presented on an experimental determination of power penalty contributions in an optical Costas-type phase-locked loop receiver, a resonant laser receiver for free-space laser communications, a simple low-loss technique for frequency-locking lasers, direct phase modulation of laser diodes, and a silex beacon. Particular attention is given to experimental results on an optical array antenna for nonmechanical beam steering, a potassium Faraday anomalous dispersion optical filter, a 100-Mbps resonant cavity phase modulator for coherent optical communications, a numerical simulation of a 325-Mbit/s QPPM optical communication system, design options for an optical multiple-access data relay terminal, CCD-based optical tracking loop design trades, and an analysis of a spatial-tracking subsystem for optical communications.

An estimator-predictor approach to PLL loop filter design

NASA Technical Reports Server (NTRS)

Statman, Joseph I.; Hurd, William J.

1990-01-01

The design of digital phase locked loops (DPLL) using estimation theory concepts in the selection of a loop filter is presented. The key concept, that the DPLL closed-loop transfer function is decomposed into an estimator and a predictor, is discussed. The estimator provides recursive estimates of phase, frequency, and higher-order derivatives, and the predictor compensates for the transport lag inherent in the loop.

Precise and long-term stabilization of the carrier-envelope phase of femtosecond laser pulses using an enhanced direct locking technique.

PubMed

Yu, Tae Jun; Hong, Kyung-Han; Choi, Hyun-Gyug; Sung, Jae Hee; Choi, Il Woo; Ko, Do-Kyeong; Lee, Jongmin; Kim, Junwon; Kim, Dong Eon; Nam, Chang Hee

2007-06-25

We demonstrate a long-term operation with reduced phase noise in the carrier-envelope-phase (CEP) stabilization process by employing a double feedback loop and an improved signal detection in the direct locking technique [Opt. Express 13, 2969 (2005)]. A homodyne balanced detection method is employed for efficiently suppressing the dc noise in the f-2f beat signal, which is converted into the CEP noise in the direct locking loop working at around zero carrier-envelope offset frequency (f(ceo)). In order to enhance the long-term stability, we have used the double feedback scheme that modulates both the oscillator pump power for a fast control and the intracavity-prism insertion depth for a slow and high-dynamic-range control. As a result, the in-loop phase jitter is reduced from 50 mrad of the previous result to 29 mrad, corresponding to 13 as in time scale, and the long-term stable operation is achieved for more than 12 hours.

LOCSET Phase Locking: Operation, Diagnostics, and Applications

NASA Astrophysics Data System (ADS)

Pulford, Benjamin N.

The aim of this dissertation is to discuss the theoretical and experimental work recently done with the Locking of Optical Coherence via Single-detector Electronic-frequency Tagging (LOCSET) phase locking technique developed and employed here are AFRL. The primary objectives of this effort are to detail the fundamental operation of the LOCSET phase locking technique, recognize the conditions in which the LOCSET control electronics optimally operate, demonstrate LOCSET phase locking with higher channel counts than ever before, and extend the LOCSET technique to correct for low order, atmospherically induced, phase aberrations introduced to the output of a tiled array of coherently combinable beams. The experimental work performed for this effort resulted in the coherent combination of 32 low power optical beams operating with unprecedented LOCSET phase error performance of lambda/71 RMS in a local loop beam combination configuration. The LOCSET phase locking technique was also successfully extended, for the first time, into an Object In the Loop (OIL) configuration by utilizing light scattered off of a remote object as the optical return signal for the LOCSET phase control electronics. Said LOCSET-OIL technique is capable of correcting for low order phase aberrations caused by atmospheric turbulence disturbances applied across a tiled array output.

Multiplexing Readout of TES Microcalorimeters Based on Analog Baseband Feedback

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takei, Y.; Yamasaki, N.Y; Mitsuda, K.

2009-12-16

A TES microcalorimeter array is a promising spectrometer with excellent energy resolution and a moderate imaging capability. To realize a large format array in space, multiplexing the TES signals at the low tempersture stage is mandatory. We are developing frequency division multiplexing (FDM) based on baseband feedback technique. In FDM, each TES is AC-biased with a different carrier frequency. Signals from several pixels are summed and then read out by one SQUID. The maximum number of multiplexed pixels are limited by the frequency band in which the SQUID can be operated in a flux-locked loop, which is {approx}1 MHz withmore » standard flux-locked loop circuit. In the baseband feedback, the signal ({approx}10 kHz band) from the TES is once demodulated. Then a reconstructed copy of the modulated signal with an appropriate phase is fed back to the SQUID input coil to maintain an approximately constant magnetic flux. This can be implemented even for large cable delays and automatically suppresses the carrier. We developed a prototype electronics for the baseband feedback based on an analog phase sensitive detector (PSD) and a multiplier. Combined with Seiko 80-SSA SQUID amp, open-loop gain of 8 has been obtained for 10 kHz baseband signal at 5 MHz carrier frequency, with a moderate noise contribution of 27pA/{radical}(Hz) at input.« less

Digital phase shifter synchronizes local oscillators

NASA Technical Reports Server (NTRS)

Ali, S. M.

1978-01-01

Digital phase-shifting network is used as synchronous frequency multiplier for applications such as phase-locking two signals that may differ in frequency. Circuit has various phase-shift capability. Possible applications include data-communication systems and hybrid digital/analog phase-locked loops.

Digital simulation of hybrid loop operation in RFI backgrounds.

NASA Technical Reports Server (NTRS)

Ziemer, R. E.; Nelson, D. R.

1972-01-01

A digital computer model for Monte-Carlo simulation of an imperfect second-order hybrid phase-locked loop (PLL) operating in radio-frequency interference (RFI) and Gaussian noise backgrounds has been developed. Characterization of hybrid loop performance in terms of cycle slipping statistics and phase error variance, through computer simulation, indicates that the hybrid loop has desirable performance characteristics in RFI backgrounds over the conventional PLL or the costas loop.

On higher order discrete phase-locked loops.

NASA Technical Reports Server (NTRS)

Gill, G. S.; Gupta, S. C.

1972-01-01

An exact mathematical model is developed for a discrete loop of a general order particularly suitable for digital computation. The deterministic response of the loop to the phase step and the frequency step is investigated. The design of the digital filter for the second-order loop is considered. Use is made of the incremental phase plane to study the phase error behavior of the loop. The model of the noisy loop is derived and the optimization of the loop filter for minimum mean-square error is considered.

Optically Phase-Locked Electronic Speckle Pattern Interferometer (OPL-ESPI)

NASA Astrophysics Data System (ADS)

Moran, Steven E.; Law, Robert L.; Craig, Peter N.; Goldberg, Warren M.

1986-10-01

This report describes the design, theory, operation, and characteristics of the OPL-ESPI, which generates real time equal Doppler speckle contours of vibrating objects from unstable sensor platforms with a Doppler resolution of 30 Hz and a maximum tracking range of + or - 5 HMz. The optical phase locked loop compensates for the deleterious effects of ambient background vibration and provides the bases for a new ESPI video signal processing technique, which produces high contrast speckle contours. The OPL-ESPI system has local oscillator phase modulation capability, offering the potential for detection of vibrations with the amplitudes less than lambda/100.

Open-loop digital frequency multiplier

NASA Technical Reports Server (NTRS)

Moore, R. C.

1977-01-01

Monostable multivibrator is implemented by using digital integrated circuits where multiplier constant is too large for conventional phase-locked-loop integrated circuit. A 400 Hz clock is generated by divide-by-N counter from 1 Hz timing reference.

Performance improvement of a binary quantized all-digital phase-locked loop with a new aided-acquisition technique

NASA Astrophysics Data System (ADS)

Sandoz, J.-P.; Steenaart, W.

1984-12-01

The nonuniform sampling digital phase-locked loop (DPLL) with sequential loop filter, in which the correction sizes are controlled by the accumulated differences of two additional phase comparators, is graphically analyzed. In the absence of noise and frequency drift, the analysis gives some physical insight into the acquisition and tracking behavior. Taking noise into account, a mathematical model is derived and a random walk technique is applied to evaluate the rms phase error and the mean acquisition time. Experimental results confirm the appropriate simplifying hypotheses used in the numerical analysis. Two related performance measures defined in terms of the rms phase error and the acquisition time for a given SNR are used. These measures provide a common basis for comparing different digital loops and, to a limited extent, also with a first-order linear loop. Finally, the behavior of a modified DPLL under frequency deviation in the presence of Gaussian noise is tested experimentally and by computer simulation.

High resolution angular sensor. [reducing ring laser gyro output quantization using phase locked loops

NASA Technical Reports Server (NTRS)

Gneses, M. I.; Berg, D. S.

1981-01-01

Specifications for the pointing stabilization system of the large space telescope were used in an investigation of the feasibility of reducing ring laser gyro output quantization to the sub-arc-second level by the use of phase locked loops and associated electronics. Systems analysis procedures are discussed and a multioscillator laser gyro model is presented along with data on the oscillator noise. It is shown that a second order closed loop can meet the measurement noise requirements when the loop gain and time constant of the loop filter are appropriately chosen. The preliminary electrical design is discussed from the standpoint of circuit tradeoff considerations. Analog, digital, and hybrid designs are given and their applicability to the high resolution sensor is examined. the electrical design choice of a system configuration is detailed. The design and operation of the various modules is considered and system block diagrams are included. Phase 1 and 2 test results using the multioscillator laser gyro are included.

An injection-locked OEO based frequency doubler independent of electrical doubler phase noise deteriorating rule

NASA Astrophysics Data System (ADS)

Xie, Zhengyang; Zheng, Xiaoping; Li, Shangyuan; Yan, Haozhe; Xiao, Xuedi; Xue, Xiaoxiao

2018-06-01

We propose an injection-locked optoelectronic oscillator (OEO) based wide-band frequency doubler, which is free from phase noise deterioration in electrical doubler, by using a dual-parallel Mach-Zehnder modulator (DPMZM). Through adjusting the optical phase shifts in different arms of the DPMZM, the doubling signal oscillates in the OEO loop while the fundamental signal takes on phase modulation over the light and vanishes at photo-detector (PD) output. By controlling power of fundamental signal the restriction of phase-noise deterioration rule in electrical doubler is totally canceled. Experimental results show that the doubler output has a better phase noise value of, for example, -117 dBc/Hz @ 10 kHz at 6 GHz with an improvement more than 17 dB and 23 dB compared with that of fundamental input and electrical doubler, respectively. Besides, the stability of this doubler output can reach to 1 . 5 × 10-14 at 1000 s averaging time. The frequency range of doubling signal is limited by the bandwidth of electrical amplifier in OEO loop.

Laser Metrology Heterodyne Phase-Locked Loop

NASA Technical Reports Server (NTRS)

Loya, Frank; Halverson, Peter

2009-01-01

A method reduces sensitivity to noise in a signal from a laser heterodyne interferometer. The phase-locked loop (PLL) removes glitches that occur in a zero-crossing detector s output [that can happen if the signal-to-noise ratio (SNR) of the heterodyne signal is low] by the use of an internal oscillator that produces a square-wave signal at a frequency that is inherently close to the heterodyne frequency. It also contains phase-locking circuits that lock the phase of the oscillator to the output of the zero-crossing detector. Because the PLL output is an oscillator signal, it is glitch-free. This enables the ability to make accurate phase measurements in spite of low SNR, creates an immunity to phase error caused by shifts in the heterodyne frequency (i.e. if the target moves causing Doppler shift), and maintains a valid phase even when the signal drops out for brief periods of time, such as when the laser is blocked by a stray object.

CW injection locking for long-term stability of frequency combs

NASA Astrophysics Data System (ADS)

Williams, Charles; Quinlan, Franklyn; Delfyett, Peter J.

2009-05-01

Harmonically mode-locked semiconductor lasers with external ring cavities offer high repetition rate pulse trains while maintaining low optical linewidth via long cavity storage times. Continuous wave (CW) injection locking further reduces linewidth and stabilizes the optical frequencies. The output can be stabilized long-term with the help of a modified Pound-Drever-Hall feedback loop. Optical sidemode suppression of 36 dB has been shown, as well as RF supermode noise suppression of 14 dB for longer than 1 hour. In addition to the injection locking of harmonically mode-locked lasers requiring an external frequency source, recent work shows the viability of the injection locking technique for regeneratively mode-locked lasers, or Coupled Opto-Electronic Oscillators (COEO).

Analog circuit for the measurement of phase difference between two noisy sine-wave signals

NASA Technical Reports Server (NTRS)

Shakkottai, P.; Kwack, E. Y.; Back, L. H.

1989-01-01

A simple circuit was designed to measure the phase difference between two noisy sine waves. It locks over a wide range of frequencies and produces an output proportional to the phase difference of rapidly varying signals. A square wave locked in frequency and phase to the first signal is produced by a phase-locked loop and is amplified by an operational amplifier.

Arm-Locking with the GRACE Follow-On Laser Ranging Instrument

NASA Technical Reports Server (NTRS)

Thorpe, James Ira; Mckenzie, Kirk

2016-01-01

Arm-locking is a technique for stabilizing the frequency of a laser in an inter-spacecraft interferometer by using the spacecraft separation as the frequency reference. A candidate technique for future space-based gravitational wave detectors such as the Laser Interferometer Space Antenna (LISA), arm-locking has been extensive studied in this context through analytic models, time-domain simulations, and hardware-in-the-loop laboratory demonstrations. In this paper we show the Laser Ranging Instrument flying aboard the upcoming Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission provides an appropriate platform for an on-orbit demonstration of the arm-locking technique. We describe an arm-locking controller design for the GRACE-FO system and a series of time-domain simulations that demonstrate its feasibility. We conclude that it is possible to achieve laser frequency noise suppression of roughly two orders of magnitude around a Fourier frequency of 1Hz with conservative margins on the system's stability. We further demonstrate that `pulling' of the master laser frequency due to fluctuating Doppler shifts and lock acquisition transients is less than 100MHz over several GRACE-FO orbits. These findings motivate further study of the implementation of such a demonstration.

Arm locking with the GRACE follow-on laser ranging interferometer

NASA Astrophysics Data System (ADS)

Thorpe, James Ira; McKenzie, Kirk

2016-02-01

Arm locking is a technique for stabilizing the frequency of a laser in an interspacecraft interferometer by using the spacecraft separation as the frequency reference. A candidate technique for future space-based gravitational wave detectors such as the Laser Interferometer Space Antenna, arm locking has been extensive studied in this context through analytic models, time-domain simulations, and hardware-in-the-loop laboratory demonstrations. In this paper we show the laser ranging interferometer instrument flying aboard the upcoming Gravity Recovery and Climate Experiment follow-on (GRACE-FO) mission provides an appropriate platform for an on-orbit demonstration of the arm-locking technique. We describe an arm-locking controller design for the GRACE-FO system and a series of time-domain simulations that demonstrate its feasibility. We conclude that it is possible to achieve laser frequency noise suppression of roughly 2 orders of magnitude around a Fourier frequency of 1 Hz with conservative margins on the system's stability. We further demonstrate that "pulling" of the master laser frequency due to fluctuating Doppler shifts and lock acquisition transients is less than 100 MHz over several GRACE-FO orbits. These findings motivate further study of the implementation of such a demonstration.

Initiator-catalyzed self-assembly of duplex-looped DNA hairpin motif based on strand displacement reaction for logic operations and amplified biosensing.

PubMed

Bi, Sai; Yue, Shuzhen; Wu, Qiang; Ye, Jiayan

2016-09-15

Here we program an initiator-catalyzed self-assembly of duplex-looped DNA hairpin motif based on strand displacement reaction. Due to the recycling of initiator and performance in a cascade manner, this system is versatilely extended to logic operations, including the construction of concatenated logic circuits with a feedback function and a biocomputing keypad-lock security system. Compared with previously reported molecular security systems, the prominent feature of our keypad lock is that it can be spontaneously reset and recycled with no need of any external stimulus and human intervention. Moreover, through integrating with an isothermal amplification technique of rolling circle amplification (RCA), this programming catalytic DNA self-assembly strategy readily achieves sensitive and selective biosensing of initiator. Importantly, a magnetic graphene oxide (MGO) is introduced to remarkably reduced background, which plays an important role in enhancing the signal-to-noise ratio and improving the detection sensitivity. Therefore, the proposed sophisticated DNA strand displacement-based methodology with engineering dynamic functions may find broad applications in the construction of programming DNA nanostructures, amplification biosensing platform, and large-scale DNA circuits. Copyright © 2016 Elsevier B.V. All rights reserved.

Ring-shaped active mode-locked tunable laser using quantum-dot semiconductor optical amplifier

NASA Astrophysics Data System (ADS)

Zhang, Mingxiao; Wang, Yongjun; Liu, Xinyu

2018-03-01

In this paper, a lot of simulations has been done for ring-shaped active mode-locked lasers with quantum-dot semiconductor optical amplifier (QD-SOA). Based on the simulation model of QD-SOA, we discussed about the influence towards mode-locked waveform frequency and pulse caused by QD-SOA maximum mode peak gain, active layer loss coefficient, bias current, incident light pulse, fiber nonlinear coefficient. In the meantime, we also take the tunable performance of the laser into consideration. Results showed QD-SOA a better performance than original semiconductor optical amplifier (SOA) in recovery time, line width, and nonlinear coefficients, which makes it possible to output a locked-mode impulse that has a higher impulse power, narrower impulse width as well as the phase is more easily controlled. After a lot of simulations, this laser can realize a 20GHz better locked-mode output pulse after 200 loops, where the power is above 17.5mW, impulse width is less than 2.7ps, moreover, the tunable wavelength range is between 1540nm-1580nm.

A digitalized silicon microgyroscope based on embedded FPGA.

PubMed

Xia, Dunzhu; Yu, Cheng; Wang, Yuliang

2012-09-27

This paper presents a novel digital miniaturization method for a prototype silicon micro-gyroscope (SMG) with the symmetrical and decoupled structure. The schematic blocks of the overall system consist of high precision analog front-end interface, high-speed 18-bit analog to digital convertor, a high-performance core Field Programmable Gate Array (FPGA) chip and other peripherals such as high-speed serial ports for transmitting data. In drive mode, the closed-loop drive circuit are implemented by automatic gain control (AGC) loop and software phase-locked loop (SPLL) based on the Coordinated Rotation Digital Computer (CORDIC) algorithm. Meanwhile, the sense demodulation module based on varying step least mean square demodulation (LMSD) are addressed in detail. All kinds of algorithms are simulated by Simulink and DSPbuilder tools, which is in good agreement with the theoretical design. The experimental results have fully demonstrated the stability and flexibility of the system.

A Digitalized Silicon Microgyroscope Based on Embedded FPGA

PubMed Central

Xia, Dunzhu; Yu, Cheng; Wang, Yuliang

2012-01-01

This paper presents a novel digital miniaturization method for a prototype silicon micro-gyroscope (SMG) with the symmetrical and decoupled structure. The schematic blocks of the overall system consist of high precision analog front-end interface, high-speed 18-bit analog to digital convertor, a high-performance core Field Programmable Gate Array (FPGA) chip and other peripherals such as high-speed serial ports for transmitting data. In drive mode, the closed-loop drive circuit are implemented by automatic gain control (AGC) loop and software phase-locked loop (SPLL) based on the Coordinated Rotation Digital Computer (CORDIC) algorithm. Meanwhile, the sense demodulation module based on varying step least mean square demodulation (LMSD) are addressed in detail. All kinds of algorithms are simulated by Simulink and DSPbuilder tools, which is in good agreement with the theoretical design. The experimental results have fully demonstrated the stability and flexibility of the system. PMID:23201990

A study of FM threshold extension techniques

NASA Technical Reports Server (NTRS)

Arndt, G. D.; Loch, F. J.

1972-01-01

The characteristics of three postdetection threshold extension techniques are evaluated with respect to the ability of such techniques to improve the performance of a phase lock loop demodulator. These techniques include impulse-noise elimination, signal correlation for the detection of impulse noise, and delta modulation signal processing. Experimental results from signal to noise ratio data and bit error rate data indicate that a 2- to 3-decibel threshold extension is readily achievable by using the various techniques. This threshold improvement is in addition to the threshold extension that is usually achieved through the use of a phase lock loop demodulator.

Optimal space communications techniques. [using digital and phase locked systems for signal processing

NASA Technical Reports Server (NTRS)

Schilling, D. L.

1974-01-01

Digital multiplication of two waveforms using delta modulation (DM) is discussed. It is shown that while conventional multiplication of two N bit words requires N2 complexity, multiplication using DM requires complexity which increases linearly with N. Bounds on the signal-to-quantization noise ratio (SNR) resulting from this multiplication are determined and compared with the SNR obtained using standard multiplication techniques. The phase locked loop (PLL) system, consisting of a phase detector, voltage controlled oscillator, and a linear loop filter, is discussed in terms of its design and system advantages. Areas requiring further research are identified.

Compact all-fiber figure-9 dissipative soliton resonance mode-locked double-clad Er:Yb laser.

PubMed

Krzempek, Karol; Sotor, Jaroslaw; Abramski, Krzysztof

2016-11-01

The first demonstration of a compact all-fiber figure-9 double-clad erbium-ytterbium laser working in the dissipative soliton resonance (DSR) regime is presented. Mode-locking was achieved using a nonlinear amplifying loop (NALM) resonator configuration. The laser was assembled with an additional 475 m long spool of SMF28 fiber in the NALM loop in order to obtain large net-anomalous cavity dispersion (-10.4  ps²), and therefore ensure that DSR would be the dominant mode-locking mechanism. At maximum pump power (4.78 W) the laser generated rectangular-shaped pulses with 455 ns duration and an average power of 950 mW, which at a repetition frequency of 412 kHz corresponds to a record energy of 2.3 μJ per pulse.

Spectral Narrowing of a Varactor-Integrated Resonant-Tunneling-Diode Terahertz Oscillator by Phase-Locked Loop

NASA Astrophysics Data System (ADS)

Ogino, Kota; Suzuki, Safumi; Asada, Masahiro

2017-12-01

Spectral narrowing of a resonant-tunneling-diode (RTD) terahertz oscillator, which is useful for various applications of terahertz frequency range, such as an accurate gas spectroscopy, a frequency reference in various communication systems, etc., was achieved with a phase-locked loop system. The oscillator is composed of an RTD, a slot antenna, and a varactor diode for electrical frequency tuning. The output of the RTD oscillating at 610 GHz was down-converted to 400 MHz by a heterodyne detection. The phase noise was transformed to amplitude noise by a balanced mixer and fed back into the varactor diode. The loop filter for a stable operation is discussed. The spectral linewidth of 18.6 MHz in free-running operation was reduced to less than 1 Hz by the feedback.

Clock recovery for high-speed optical communication

NASA Astrophysics Data System (ADS)

Pedrotti, Kenneth D.

1996-01-01

This paper reviews recent results for clock recovery circuits operating at speeds in excess of 1 Gbit/sec or realized as multichannel arrays. The emphasis is on synchronous optical network (SONET) type systems, their requirements, and the effect of the clock recovery circuits on system performance. Clock recovery approaches include filter based, phase-locked-loops, and all-optical methods.

A method for simulating a flux-locked DC SQUID

NASA Technical Reports Server (NTRS)

Gutt, G. M.; Kasdin, N. J.; Condron, M. R., II; Muhlfelder, B.; Lockhart, J. M.; Cromar, M. W.

1993-01-01

The authors describe a computationally efficient and accurate method for simulating a dc SQUID's V-Phi (voltage-flux) and I-V characteristics which has proven valuable in evaluating and improving various SQUID readout methods. The simulation of the SQUID is based on fitting of previously acquired data from either a real or a modeled device using the Fourier transform of the V-Phi curve. This method does not predict SQUID behavior, but rather is a way of replicating a known behavior efficiently with portability into various simulation programs such as SPICE. The authors discuss the methods used to simulate the SQUID and the flux-locking control electronics, and present specific examples of this approach. Results include an estimate of the slew rate and linearity of a simple flux-locked loop using a characterized dc SQUID.

Wide tracking range, auto ranging, low jitter phase lock loop for swept and fixed frequency systems

DOEpatents

Kerner, Thomas M.

2001-01-01

The present invention provides a wide tracking range phase locked loop (PLL) circuit that achieves minimal jitter in a recovered clock signal, regardless of the source of the jitter (i.e. whether it is in the source or the transmission media). The present invention PLL has automatic harmonic lockout detection circuitry via a novel lock and seek control logic in electrical communication with a programmable frequency discriminator and a code balance detector. (The frequency discriminator enables preset of a frequency window of upper and lower frequency limits to derive a programmable range within which signal acquisition is effected. The discriminator works in combination with the code balance detector circuit to minimize the sensitivity of the PLL circuit to random data in the data stream). In addition, the combination of a differential loop integrator with the lock and seek control logic obviates a code preamble and guarantees signal acquisition without harmonic lockup. An adaptive cable equalizer is desirably used in combination with the present invention PLL to recover encoded transmissions containing a clock and/or data. The equalizer automatically adapts to equalize short haul cable lengths of coaxial and twisted pair cables or wires and provides superior jitter performance itself. The combination of the equalizer with the present invention PLL is desirable in that such combination permits the use of short haul wires without significant jitter.

Dynamic Self-Locking of an OEO Containing a VCSEL

NASA Technical Reports Server (NTRS)

Strekalov, Dmitry; Matsko, Andrey; Yu, Nan; Savchenkov, Anatoliy; Maleki, Lute

2009-01-01

A method of dynamic self-locking has been demonstrated to be effective as a means of stabilizing the wavelength of light emitted by a vertical-cavity surface-emitting laser (VCSEL) that is an active element in the frequency-control loop of an optoelectronic oscillator (OEO) designed to implement an atomic clock based on an electromagnetically- induced-transparency (EIT) resonance. This scheme can be considered an alternative to the one described in Optical Injection Locking of a VCSEL in an OEO (NPO-43454), NASA Tech Briefs, Vol. 33, No. 7 (July 2009), page 33. Both schemes are expected to enable the development of small, low-power, high-stability atomic clocks that would be suitable for use in applications involving precise navigation and/or communication. To recapitulate from the cited prior article: In one essential aspect of operation of an OEO of the type described above, a microwave modulation signal is coupled into the VCSEL. Heretofore, it has been well known that the wavelength of light emitted by a VCSEL depends on its temperature and drive current, necessitating thorough stabilization of these operational parameters. Recently, it was discovered that the wavelength also depends on the microwave power coupled into the VCSEL. This concludes the background information. From the perspective that led to the conception of the optical injection-locking scheme described in the cited prior article, the variation of the VCSEL wavelength with the microwave power circulating in the frequency-control loop is regarded as a disadvantage and optical injection locking is a solution of the problem of stabilizing the wavelength in the presence of uncontrolled fluctuations in the microwave power. The present scheme for dynamic self-locking emerges from a different perspective, in which the dependence of VCSEL wavelength on microwave power is regarded as an advantageous phenomenon that can be exploited as a means of controlling the wavelength. The figure schematically depicts an atomic-clock OEO of the type in question, wherein (1) the light from the VCSEL is used to excite an EIT resonance in selected atoms in a gas cell (e.g., 87Rb atoms in a low-pressure mixture of Ar and Ne) and (2) the power supplied to the VCSEL is modulated by a microwave signal that includes components at beat frequencies among the VCSEL wavelength and modulation sidebands. As the VCSEL wavelength changes, it moves closer to or farther from a nearby absorption spectral line, and the optical power transmitted through the cell (and thus the loop gain) changes accordingly. A change in the loop gain causes a change in the microwave power and, thus, in the VCSEL wavelength. It is possible to choose a set of design and operational parameters (most importantly, the electronic part of the loop gain) such that the OEO stabilizes itself in the sense that an increase in circulating microwave power causes the VCSEL wavelength to change in a direction that results in an increase in optical absorption and thus a decrease in circulating microwave power. Typically, such an appropriate choice of operational parameters involves setting the nominal VCSEL wavelength to a point on the shorter-wavelength wing of an absorption spectral line.

Synthesis and evaluation of phase detectors for active bit synchronizers

NASA Technical Reports Server (NTRS)

Mcbride, A. L.

1974-01-01

Self-synchronizing digital data communication systems usually use active or phase-locked loop (PLL) bit synchronizers. The three main elements of PLL synchronizers are the phase detector, loop filter, and the voltage controlled oscillator. Of these three elements, phase detector synthesis is the main source of difficulty, particularly when the received signals are demodulated square-wave signals. A phase detector synthesis technique is reviewed that provides a physically realizable design for bit synchronizer phase detectors. The development is based upon nonlinear recursive estimation methods. The phase detector portion of the algorithm is isolated and analyzed.

Digital accumulators in phase and frequency tracking loops

NASA Technical Reports Server (NTRS)

Hinedi, Sami; Statman, Joseph I.

1990-01-01

Results on the effects of digital accumulators in phase and frequency tracking loops are presented. Digital accumulators or summers are used extensively in digital signal processing to perform averaging or to reduce processing rates to acceptable levels. For tracking the Doppler of high-dynamic targets at low carrier-to-noise ratios, it is shown through simulation and experiment that digital accumulators can contribute an additional loss in operating threshold. This loss was not considered in any previous study and needs to be accounted for in performance prediction analysis. Simulation and measurement results are used to characterize the loss due to the digital summers for three different tracking loops: a digital phase-locked loop, a cross-product automatic frequency tracking loop, and an extended Kalman filter. The tracking algorithms are compared with respect to their frequency error performance and their ability to maintain lock during severe maneuvers at various carrier-to-noise ratios. It is shown that failure to account for the effect of accumulators can result in an inaccurate performance prediction, the extent of which depends highly on the algorithm used.

Enhancement of the transversal magnetic optic Kerr effect: Lock-in vs. hysteresis method.

PubMed

Hayek, Jorge Nicolás; Herreño-Fierro, César A; Patiño, Edgar J

2016-10-01

The lock-in amplifier is often used to study the enhancement of the magneto-optical Kerr effect (MOKE) in the presence of plasmon resonances. In the present work we show that it is possible to investigate such effect replacing the lock-in amplifier by a compensator, filter, and differential amplifier. This allows us to extract the full hysteresis loop in and out of the resonance without the need of a lock-in amplifier. Our results demonstrate these two setups are equivalent to study the enhancement of the transversal MOKE (T-MOKE) in magnetoplasmonic systems.

Receiver design and performance characteristics

NASA Technical Reports Server (NTRS)

Simon, M. K.; Yuen, J. H.

1982-01-01

The basic design, principles of operation, and characteristics of deep space communications receivers are examined. In particular, the basic fundamentals of phase-locked loop and Costas loop receivers used for synchronization, tracking, and demodulation of phase-coherent signals in residual carrier and suppressed carrier systems are addressed.

A Computer Model of a Phase Lock Loop

NASA Technical Reports Server (NTRS)

Shelton, Ralph Paul

1973-01-01

A computer model is reported of a PLL (phase-lock loop), preceded by a bandpass filter, which is valid when the bandwidth of the bandpass filter is of the same order of magnitude as the natural frequency of the PLL. New results for the PLL natural frequency equal to the bandpass filter bandwidth are presented for a second order PLL operating with carrier plus noise as the input. However, it is shown that extensions to higher order loops, and to the case of a modulated carrier are straightforward. The new results presented give the cycle skipping rate of the PLL as a function of the input carrier to noise ratio when the PLL natural frequency is equal to the bandpass filter bandwidth. Preliminary results showing the variation of the output noise power and cycle skipping rates of the PLL as a function of the loop damping ratio for the PLL natural frequency equal to the bandpass filter bandwidth are also included.

Extremely Coherent Microwave Emission from Spin Torque Oscillator Stabilized by Phase Locked Loop

PubMed Central

Tamaru, Shingo; Kubota, Hitoshi; Yakushiji, Kay; Yuasa, Shinji; Fukushima, Akio

2015-01-01

Spin torque oscillator (STO) has been attracting a great deal of attention as a candidate for the next generation microwave signal sources for various modern electronics systems since its advent. However, the phase noise of STOs under free running oscillation is still too large to be used in practical microwave applications, thus an industrially viable means to stabilize its oscillation has been strongly sought. Here we demonstrate implementation of a phase locked loop using a STO as a voltage controlled oscillator (VCO) that generates a 7.344 GHz microwave signal stabilized by a 153 MHz reference signal. Spectrum measurement showed successful phase locking of the microwave signal to the reference signal, characterized by an extremely narrow oscillation peak with a linewidth of less than the measurement limit of 1 Hz. This demonstration should be a major breakthrough toward various practical applications of STOs. PMID:26658880

A 2',2'-disulfide-bridged dinucleotide conformationally locks RNA hairpins.

PubMed

Gauthier, Florian; Beltran, Frédéric; Biscans, Annabelle; Debart, Françoise; Dupouy, Christelle; Vasseur, Jean-Jacques

2018-05-02

The synthesis and the impact of a disulfide bridge between 2'-O-positions of two adjacent nucleotides in an RNA duplex and in the loop of RNA hairpins are reported. The incorporation of this 2',2'-disulfide (S-S) bridge enabled thermal and enzymatic stabilization of the hairpin depending on its position in the loop. The influence of the disulfide bridge on RNA folding was studied at the HIV Dimerization Initiation Site (DIS) as an RNA sequence model. We have shown that this S-S bridge locked the hairpin form, whereas the extended duplex form was generated after the reduction of the disulfide bond in the presence of tris(2-carboxyethyl)phosphine or glutathione. Thus, the S-S bridge can be useful for understanding RNA folding; an RNA molecular beacon locked by an S-S bridge was also investigated as a sensor for the detection of glutathione.

A class of optimum digital phase locked loops for the DSN advanced receiver

NASA Technical Reports Server (NTRS)

Hurd, W. J.; Kumar, R.

1985-01-01

A class of optimum digital filters for digital phase locked loop of the deep space network advanced receiver is discussed. The filter minimizes a weighted combination of the variance of the random component of the phase error and the sum square of the deterministic dynamic component of phase error at the output of the numerically controlled oscillator (NCO). By varying the weighting coefficient over a suitable range of values, a wide set of filters are obtained such that, for any specified value of the equivalent loop-noise bandwidth, there corresponds a unique filter in this class. This filter thus has the property of having the best transient response over all possible filters of the same bandwidth and type. The optimum filters are also evaluated in terms of their gain margin for stability and their steady-state error performance.

Computer program CORDET. [computerized simulation of digital phase-lock loop for Omega navigation receiver

NASA Technical Reports Server (NTRS)

Palkovic, R. A.

1974-01-01

A FORTRAN 4 computer program provides convenient simulation of an all-digital phase-lock loop (DPLL). The DPLL forms the heart of the Omega navigation receiver prototype. Through the DPLL, the phase of the 10.2 KHz Omega signal is estimated when the true signal phase is contaminated with noise. This investigation has provided a convenient means of evaluating loop performance in a variety of noise environments, and has proved to be a useful tool for evaluating design changes. The goals of the simulation are to: (1) analyze the circuit on a bit-by-bit level in order to evaluate the overall design; (2) see easily the effects of proposed design changes prior to actual breadboarding; and (3) determine the optimum integration time for the DPLL in an environment typical of general aviation conditions.

Instantaneous power control of a high speed permanent magnet synchronous generator based on a sliding mode observer and a phase locked loop

NASA Astrophysics Data System (ADS)

Duan, Jiandong; Fan, Shaogui; Wu, Fengjiang; Sun, Li; Wang, Guanglin

2018-06-01

This paper proposes an instantaneous power control method for high speed permanent magnet synchronous generators (PMSG), to realize the decoupled control of active power and reactive power, through vector control based on a sliding mode observer (SMO), and a phase locked loop (PLL). Consequently, the high speed PMSG has a high internal power factor, to ensure efficient operation. Vector control and accurate estimation of the instantaneous power require an accurate estimate of the rotor position. The SMO is able to estimate the back electromotive force (EMF). The rotor position and speed can be obtained using a combination of the PLL technique and the phase compensation method. This method has the advantages of robust operation, and being resistant to noise when estimating the position of the rotor. Using instantaneous power theory, the relationship between the output active power, reactive power, and stator current of the PMSG is deduced, and the power constraint condition is analysed for operation at the unit internal power factor. Finally, the accuracy of the rotor position detection, the instantaneous power detection, and the control methods are verified using simulations and experiments.

A dynamically reconfigurable multi-functional PLL for SRAM-based FPGA in 65nm CMOS technology

NASA Astrophysics Data System (ADS)

Yang, Mingqian; Chen, Lei; Li, Xuewu; Zhang, Yanlong

2018-04-01

Phase-locked loops (PLL) have been widely utilized in FPGA as an important module for clock management. PLL with dynamic reconfiguration capability is always welcomed in FPGA design as it is able to decrease power consumption and simultaneously improve flexibility. In this paper, a multi-functional PLL with dynamic reconfiguration capability for 65nm SRAM-based FPGA is proposed. Firstly, configurable charge pump and loop filter are utilized to optimize the loop bandwidth. Secondly, the PLL incorporates a VCO with dual control voltages to accelerate the adjustment of oscillation frequency. Thirdly, three configurable dividers are presented for flexible frequency synthesis. Lastly, a configuration block with dynamic reconfiguration function is proposed. Simulation results demonstrate that the proposed multi-functional PLL can output clocks with configurable division ratio, phase shift and duty cycle. The PLL can also be dynamically reconfigured without affecting other parts' running or halting the FPGA device.

An approach to the analysis of performance of quasi-optimum digital phase-locked loops.

NASA Technical Reports Server (NTRS)

Polk, D. R.; Gupta, S. C.

1973-01-01

An approach to the analysis of performance of quasi-optimum digital phase-locked loops (DPLL's) is presented. An expression for the characteristic function of the prior error in the state estimate is derived, and from this expression an infinite dimensional equation for the prior error variance is obtained. The prior error-variance equation is a function of the communication system model and the DPLL gain and is independent of the method used to derive the DPLL gain. Two approximations are discussed for reducing the prior error-variance equation to finite dimension. The effectiveness of one approximation in analyzing DPLL performance is studied.

Ring magnet firing angle control

DOEpatents

Knott, M.J.; Lewis, L.G.; Rabe, H.H.

1975-10-21

A device is provided for controlling the firing angles of thyratrons (rectifiers) in a ring magnet power supply. A phase lock loop develops a smooth ac signal of frequency equal to and in phase with the frequency of the voltage wave developed by the main generator of the power supply. A counter that counts from zero to a particular number each cycle of the main generator voltage wave is synchronized with the smooth AC signal of the phase lock loop. Gates compare the number in the counter with predetermined desired firing angles for each thyratron and with coincidence the proper thyratron is fired at the predetermined firing angle.

Electronic Circuit Experiments and SPICE Simulation of Double Covering Bifurcation of 2-Torus Quasi-Periodic Flow in Phase-Locked Loop Circuit

NASA Astrophysics Data System (ADS)

Kamiyama, Kyohei; Endo, Tetsuro; Imai, Isao; Komuro, Motomasa

2016-06-01

Double covering (DC) bifurcation of a 2-torus quasi-periodic flow in a phase-locked loop circuit was experimentally investigated using an electronic circuit and via SPICE simulation; in the circuit, the input radio-frequency signal was frequency modulated by the sum of two asynchronous sinusoidal baseband signals. We observed both DC and period-doubling bifurcations of a discrete map on two Poincaré sections, which were realized by changing the sample timing from one baseband sinusoidal signal to the other. The results confirm the DC bifurcation of the original flow.

Open-loop control of quasiperiodic thermoacoustic oscillations

NASA Astrophysics Data System (ADS)

Guan, Yu; Gupta, Vikrant; Kashinath, Karthik; Li, Larry K. B.

2017-11-01

The open-loop application of periodic acoustic forcing has been shown to be a potentially effective strategy for controlling periodic thermoacoustic oscillations, but its effectiveness on aperiodic thermoacoustic oscillations is less clear. In this experimental study, we apply periodic acoustic forcing to a ducted premixed flame oscillating quasiperiodically at two incommensurate natural frequencies, f1 and f2. We find that (i) above a critical forcing amplitude, the system locks into the forcing by oscillating only at the forcing frequency ff, producing a closed periodic orbit in phase space with no evidence of the original T2 torus attractor; (ii) the critical forcing amplitude required for lock-in decreases as ff approaches either f1 or f2, resulting in characteristic ∨-shaped lock-in boundaries around the two natural modes; and (iii) for a wide range of forcing frequencies, the system's oscillation amplitude can be reduced to less than 20% of that of the unforced system. These findings show that the open-loop application of periodic acoustic forcing can be an effective strategy for controlling aperiodic thermoacoustic oscillations. This work was supported by the Research Grants Council of Hong Kong (Project No. 16235716 and 26202815).

Vector nature of multi-soliton patterns in a passively mode-locked figure-eight fiber laser.

PubMed

Ning, Qiu-Yi; Liu, Hao; Zheng, Xu-Wu; Yu, Wei; Luo, Ai-Ping; Huang, Xu-Guang; Luo, Zhi-Chao; Xu, Wen-Cheng; Xu, Shan-Hui; Yang, Zhong-Min

2014-05-19

The vector nature of multi-soliton dynamic patterns was investigated in a passively mode-locked figure-eight fiber laser based on the nonlinear amplifying loop mirror (NALM). By properly adjusting the cavity parameters such as the pump power level and intra-cavity polarization controllers (PCs), in addition to the fundamental vector soliton, various vector multi-soliton regimes were observed, such as the random static distribution of vector multiple solitons, vector soliton cluster, vector soliton flow, and the state of vector multiple solitons occupying the whole cavity. Both the polarization-locked vector solitons (PLVSs) and the polarization-rotating vector solitons (PRVSs) were observed for fundamental soliton and each type of multi-soliton patterns. The obtained results further reveal the fundamental physics of multi-soliton patterns and demonstrate that the figure-eight fiber lasers are indeed a good platform for investigating the vector nature of different soliton types.

Apparatus and Method to Enable Precision and Fast Laser Frequency Tuning

NASA Technical Reports Server (NTRS)

Chen, Jeffrey R. (Inventor); Numata, Kenji (Inventor); Wu, Stewart T. (Inventor); Yang, Guangning (Inventor)

2015-01-01

An apparatus and method is provided to enable precision and fast laser frequency tuning. For instance, a fast tunable slave laser may be dynamically offset-locked to a reference laser line using an optical phase-locked loop. The slave laser is heterodyned against a reference laser line to generate a beatnote that is subsequently frequency divided. The phase difference between the divided beatnote and a reference signal may be detected to generate an error signal proportional to the phase difference. The error signal is converted into appropriate feedback signals to phase lock the divided beatnote to the reference signal. The slave laser frequency target may be rapidly changed based on a combination of a dynamically changing frequency of the reference signal, the frequency dividing factor, and an effective polarity of the error signal. Feed-forward signals may be generated to accelerate the slave laser frequency switching through laser tuning ports.

Characterization of a FBG sensor interrogation system based on a mode-locked laser scheme.

PubMed

Madrigal, Javier; Fraile-Peláez, Francisco Javier; Zheng, Di; Barrera, David; Sales, Salvador

2017-10-02

This paper is focused on the characterization of a fiber Bragg grating (FBG) sensor interrogation system based on a fiber ring laser with a semiconductor optical amplifier as the gain medium, and an in-loop electro-optical modulator. This system operates as a switchable active (pulsed) mode-locked laser. The operation principle of the system is explained theoretically and validated experimentally. The ability of the system to interrogate an array of different FBGs in wavelength and spatial domain is demonstrated. Simultaneously, the influence of several important parameters on the performance of the interrogation technique has been investigated. Specifically, the effects of the bandwidth and the reflectivity of the FBGs, the SOA gain, and the depth of the intensity modulation have been addressed.

Power Scaling and Frequency Stabilization of an Injection-Locked Laser

DTIC Science & Technology

2000-05-01

In Chapter 4,1 alter the well -documented theory of locking a laser to a Fabry- Perot by performing the PDH error signal derivation in a new manner...the well -documented modulation transfer scheme to lock the frequency-doubled NPRO to a hyperfine component of an electronic transition in I2. 33 I...generally true at very low noise frequencies, well within the feedback loop bandwidth. However, when G0L(V„) « 1 and thus GCL(vn) « 1, Equation 3.9

A digital, constant-frequency pulsed phase-locked-loop instrument for real-time, absolute ultrasonic phase measurements

NASA Astrophysics Data System (ADS)

Haldren, H. A.; Perey, D. F.; Yost, W. T.; Cramer, K. E.; Gupta, M. C.

2018-05-01

A digitally controlled instrument for conducting single-frequency and swept-frequency ultrasonic phase measurements has been developed based on a constant-frequency pulsed phase-locked-loop (CFPPLL) design. This instrument uses a pair of direct digital synthesizers to generate an ultrasonically transceived tone-burst and an internal reference wave for phase comparison. Real-time, constant-frequency phase tracking in an interrogated specimen is possible with a resolution of 0.000 38 rad (0.022°), and swept-frequency phase measurements can be obtained. Using phase measurements, an absolute thickness in borosilicate glass is presented to show the instrument's efficacy, and these results are compared to conventional ultrasonic pulse-echo time-of-flight (ToF) measurements. The newly developed instrument predicted the thickness with a mean error of -0.04 μm and a standard deviation of error of 1.35 μm. Additionally, the CFPPLL instrument shows a lower measured phase error in the absence of changing temperature and couplant thickness than high-resolution cross-correlation ToF measurements at a similar signal-to-noise ratio. By showing higher accuracy and precision than conventional pulse-echo ToF measurements and lower phase errors than cross-correlation ToF measurements, the new digitally controlled CFPPLL instrument provides high-resolution absolute ultrasonic velocity or path-length measurements in solids or liquids, as well as tracking of material property changes with high sensitivity. The ability to obtain absolute phase measurements allows for many new applications than possible with previous ultrasonic pulsed phase-locked loop instruments. In addition to improved resolution, swept-frequency phase measurements add useful capability in measuring properties of layered structures, such as bonded joints, or materials which exhibit non-linear frequency-dependent behavior, such as dispersive media.

Dual Optical Comb LWIR Source and Sensor

DTIC Science & Technology

2017-10-12

Figure 39. Locking loop only controls one parameter, whereas there are two free- running parameters to control...optical frequency, along with a 12 point running average (black) equivalent to a 4 cm -1 resolution. .............................. 52 Figure 65...and processed on a single epitaxial substrate. Each OFC will be electrically driven and free- running (requiring no optical locking mechanisms). This

Phase-locking dynamics in optoelectronic oscillator

NASA Astrophysics Data System (ADS)

Banerjee, Abhijit; Sarkar, Jayjeet; Das, NikhilRanjan; Biswas, Baidyanath

2018-05-01

This paper analyzes the phase-locking phenomenon in single-loop optoelectronic microwave oscillators considering weak and strong radio frequency (RF) signal injection. The analyses are made in terms of the lock-range, beat frequency and the spectral components of the unlocked-driven oscillator. The influence of RF injection signal on the frequency pulling of the unlocked-driven optoelectronic oscillator (OEO) is also studied. An approximate expression for the amplitude perturbation of the oscillator is derived and the influence of amplitude perturbation on the phase-locking dynamics is studied. It is shown that the analysis clearly reveals the phase-locking phenomenon and the associated frequency pulling mechanism starting from the fast-beat state through the quasi-locked state to the locked state of the pulled OEO. It is found that the unlocked-driven OEO output signal has a very non-symmetrical sideband distribution about the carrier. The simulation results are also given in partial support to the conclusions of the analysis.

A 4 GHz phase locked loop design in 65 nm CMOS for the Jiangmen Underground Neutrino Observatory detector

NASA Astrophysics Data System (ADS)

Parkalian, N.; Robens, M.; Grewing, C.; Christ, V.; Kruth, A.; Liebau, D.; Muralidharan, P.; Nielinger, D.; Roth, C.; Yegin, U.; Zambanini, A.; van Waasen, S.

2018-02-01

This paper presents a 4 GHz phase locked loop (PLL), which is implemented in a 65 nm standard CMOS process to provide low noise and high frequency sampling clocks for readout electronics to be used in the Jiangmen Underground Neutrino Observatory (JUNO) experiment. Based on the application requirements the target of the design is to find the best compromise between power consumption, area and phase noise for a highly reliable topology. The design implements a novel method for the charge pump that suppresses current mismatch when the PLL is locked. This reduces static phase offset at the inputs of the phase-frequency detector (PFD) that otherwise would introduce spurs at the PLL output. In addition, a technique of amplitude regulation for the voltage controlled oscillator (VCO) is presented to provide low noise and reliable operation. The combination of thin and thick oxide varactor transistors ensures optimum tuning range and linearity over process as well as temperature changes for the VCO without additional calibration steps. The current mismatch at the output of the charge pump for the control voltage at about half the 1 V supply voltage is below 0.3% and static phase offset down to 0.25% is reached. The total PLL consumes 18.5 mW power at 1.8 V supply for the VCO and 1 V supply for the other parts.

A novel architecture of recovered data comparison for high speed clock and data recovery

NASA Astrophysics Data System (ADS)

Gao, Susan; Li, Fei; Wang, Zhigong; Cui, Hongliang

2005-05-01

A clock and data recovery (CDR) circuit is one of the crucial blocks in high-speed serial link communication systems. The data received in these systems are asynchronous and noisy, requiring that a clock be extracted to allow synchronous operations. Furthermore, the data must be "retimed" so that the jitter accumulated during transmission is removed. This paper presents a novel architecture of CDR, which is very tolerant to long sequences of serial ones or zeros and also robust to occasional long absence of transitions. The design is based on the fact that a basic clock recovery having a clock recovery circuit (CRC) and a data decision circuit separately would generate a high jitter clock when the received non-return-to-zero (NRZ) data with long sequences of ones or zeros. To eliminate this drawback, the proposed architecture incorporates a data circuit decision circuit within the phase-locked loop (PLL) CRC. Other than this, a new phase detector (PD) is also proposed, which was easy to accomplish and robust at high speed. This PD is functional with a random input and automatically turns to disable during both the locked state and long absence of transitions. The voltage-controlled oscillator (VCO) is also designed delicately to suppress the jitter. Due to the high stability, the jitter is highly reduced when the loop is locked. The simulation results of such CDR working at 1.25Gb/s particularly for 1000BASE-X Gigabit Ethernet by using TSMC 0.25μm technology are presented to prove the feasibility of this architecture. One more CDR based on edge detection architecture is also built in the circuit for performance comparisons.

Precision and Fast Wavelength Tuning of a Dynamically Phase-Locked Widely-Tunable Laser

NASA Technical Reports Server (NTRS)

Numata, Kenji; Chen, Jeffrey R.; Wu, Stewart T.

2012-01-01

We report a precision and fast wavelength tuning technique demonstrated for a digital-supermode distributed Bragg reflector laser. The laser was dynamically offset-locked to a frequency-stabilized master laser using an optical phase-locked loop, enabling precision fast tuning to and from any frequencies within a 40-GHz tuning range. The offset frequency noise was suppressed to the statically offset-locked level in less than 40 s upon each frequency switch, allowing the laser to retain the absolute frequency stability of the master laser. This technique satisfies stringent requirements for gas sensing lidars and enables other applications that require such well-controlled precision fast tuning.

The chula knot: a new sliding locking knot with a special property.

PubMed

Kuptniratsaikul, Somsak; Promsang, Trai; Kongrukgreatiyos, Kitiphong

2014-08-01

There are many types of sliding locking knots used in arthroscopic surgery. Each type has its advantages and disadvantages. This technical note describes a new sliding locking knot, the Chula knot. This knot has been used for arthroscopic shoulder surgery in more than 500 cases at our hospital. The Chula knot has a special property in that it can be unfastened and retightened in case of premature locking and unintended loop loosening. This retensioning ability cannot be found in other configurations of arthroscopic knots. The Chula knot also has other benefits: It has high ultimate tensile strength and is easy to tie.

Critique of a Hughes shuttle Ku-band data sampler/bit synchronizer

NASA Technical Reports Server (NTRS)

Holmes, J. K.

1980-01-01

An alternative bit synchronizer proposed for shuttle was analyzed in a noise-free environment by considering the basic operation of the loop via timing diagrams and by linearizing the bit synchronizer as an equivalent, continuous, phased-lock loop (PLL). The loop is composed of a high-frequency phase-frequency detector which is capable of detecting both phase and frequency errors and is used to track the clock, and a bit transition detector which attempts to track the transitions of the data bits. It was determined that the basic approach was a good design which, with proper implementation of the accumulator, up/down counter and logic should provide accurate mid-bit sampling with symmetric bits. However, when bit asymmetry occurs, the bit synchronizer can lock up with a large timing error, yet be quasi-stable (timing will not change unless the clock and bit sequence drift). This will result in incorrectly detecting some bits.

The Statistical Loop Analyzer (SLA)

NASA Technical Reports Server (NTRS)

Lindsey, W. C.

1985-01-01

The statistical loop analyzer (SLA) is designed to automatically measure the acquisition, tracking and frequency stability performance characteristics of symbol synchronizers, code synchronizers, carrier tracking loops, and coherent transponders. Automated phase lock and system level tests can also be made using the SLA. Standard baseband, carrier and spread spectrum modulation techniques can be accomodated. Through the SLA's phase error jitter and cycle slip measurements the acquisition and tracking thresholds of the unit under test are determined; any false phase and frequency lock events are statistically analyzed and reported in the SLA output in probabilistic terms. Automated signal drop out tests can be performed in order to trouble shoot algorithms and evaluate the reacquisition statistics of the unit under test. Cycle slip rates and cycle slip probabilities can be measured using the SLA. These measurements, combined with bit error probability measurements, are all that are needed to fully characterize the acquisition and tracking performance of a digital communication system.

Binary processing and display concepts for low-cost Omega receivers. [airborne systems simulation

NASA Technical Reports Server (NTRS)

Lilley, R. W.

1974-01-01

A description is given of concepts related to plans for developing a low-cost, all-digital Omega receiver capable of offering to the small-aircraft pilot a reliable and accurate navigation aid. The receiver base considered includes a receiver front-end module, a receiver control module, a memory-aided phase-locked loop module, a housekeeping timer module, and a synthesizer module.

Homodyne Phase-Shift-Keying Systems: Past Challenges and Future Opportunities

NASA Astrophysics Data System (ADS)

Kazovsky, Leonid G.; Kalogerakis, Georgios; Shaw, Wei-Tao

2006-12-01

Homodyne phase-shift-keying systems can achieve the best receiver sensitivity and the longest transmission distance among all optical communication systems. This paper reviews recent research efforts in the field and examines future possibilities that might lead toward potential practical use of these systems. Additionally, phase estimation techniques based on feed-forward phase recovery and digital delay-lock loop approaches are examined, simulated, and compared.

PLL jitter reduction by utilizing a ferroelectric capacitor as a VCO timing element.

PubMed

Pauls, Greg; Kalkur, Thottam S

2007-06-01

Ferroelectric capacitors have steadily been integrated into semiconductor processes due to their potential as storage elements within memory devices. Polarization reversal within ferroelectric capacitors creates a high nonlinear dielectric constant along with a hysteresis profile. Due to these attributes, a phase-locked loop (PLL), when based on a ferroelectric capacitor, has the advantage of reduced cycle-to-cycle jitter. PLLs based on ferroelectric capacitors represent a new research area for reduction of oscillator jitter.

Application of multirate digital filter banks to wideband all-digital phase-locked loops design

NASA Technical Reports Server (NTRS)

Sadr, Ramin; Shah, Biren; Hinedi, Sami

1993-01-01

A new class of architecture for all-digital phase-locked loops (DPLL's) is presented in this article. These architectures, referred to as parallel DPLL (PDPLL), employ multirate digital filter banks (DFB's) to track signals with a lower processing rate than the Nyquist rate, without reducing the input (Nyquist) bandwidth. The PDPLL basically trades complexity for hardware-processing speed by introducing parallel processing in the receiver. It is demonstrated here that the DPLL performance is identical to that of a PDPLL for both steady-state and transient behavior. A test signal with a time-varying Doppler characteristic is used to compare the performance of both the DPLL and the PDPLL.

Radiation-hardened-by-design clocking circuits in 0.13-μm CMOS technology

NASA Astrophysics Data System (ADS)

You, Y.; Huang, D.; Chen, J.; Gong, D.; Liu, T.; Ye, J.

2014-01-01

We present a single-event-hardened phase-locked loop for frequency generation applications and a digital delay-locked loop for DDR2 memory interface applications. The PLL covers a 12.5 MHz to 500 MHz frequency range with an RMS Jitter (RJ) of 4.70-pS. The DLL operates at 267 MHz and has a phase resolution of 60-pS. Designed in 0.13-μm CMOS technology, the PLL and the DLL are hardened against SEE for charge injection of 250 fC. The PLL and the DLL consume 17 mW and 22 mW of power under a 1.5 V power supply, respectively.

Application of multirate digital filter banks to wideband all-digital phase-locked loops design

NASA Astrophysics Data System (ADS)

Sadr, Ramin; Shah, Biren; Hinedi, Sami

1993-06-01

A new class of architecture for all-digital phase-locked loops (DPLL's) is presented in this article. These architectures, referred to as parallel DPLL (PDPLL), employ multirate digital filter banks (DFB's) to track signals with a lower processing rate than the Nyquist rate, without reducing the input (Nyquist) bandwidth. The PDPLL basically trades complexity for hardware-processing speed by introducing parallel processing in the receiver. It is demonstrated here that the DPLL performance is identical to that of a PDPLL for both steady-state and transient behavior. A test signal with a time-varying Doppler characteristic is used to compare the performance of both the DPLL and the PDPLL.

Application of multirate digital filter banks to wideband all-digital phase-locked loops design

NASA Astrophysics Data System (ADS)

Sadr, R.; Shah, B.; Hinedi, S.

1992-11-01

A new class of architecture for all-digital phase-locked loops (DPLL's) is presented in this article. These architectures, referred to as parallel DPLL (PDPLL), employ multirate digital filter banks (DFB's) to track signals with a lower processing rate than the Nyquist rate, without reducing the input (Nyquist) bandwidth. The PDPLL basically trades complexity for hardware-processing speed by introducing parallel processing in the receiver. It is demonstrated here that the DPLL performance is identical to that of a PDPLL for both steady-state and transient behavior. A test signal with a time-varying Doppler characteristic is used to compare the performance of both the DPLL and the PDPLL.

Application of multirate digital filter banks to wideband all-digital phase-locked loops design

NASA Technical Reports Server (NTRS)

Sadr, R.; Shah, B.; Hinedi, S.

1992-01-01

A new class of architecture for all-digital phase-locked loops (DPLL's) is presented in this article. These architectures, referred to as parallel DPLL (PDPLL), employ multirate digital filter banks (DFB's) to track signals with a lower processing rate than the Nyquist rate, without reducing the input (Nyquist) bandwidth. The PDPLL basically trades complexity for hardware-processing speed by introducing parallel processing in the receiver. It is demonstrated here that the DPLL performance is identical to that of a PDPLL for both steady-state and transient behavior. A test signal with a time-varying Doppler characteristic is used to compare the performance of both the DPLL and the PDPLL.

A New Built-in Self Test Scheme for Phase-Locked Loops Using Internal Digital Signals

NASA Astrophysics Data System (ADS)

Kim, Youbean; Kim, Kicheol; Kim, Incheol; Kang, Sungho

Testing PLLs (phase-locked loops) is becoming an important issue that affects both time-to-market and production cost of electronic systems. Though a PLL is the most common mixed-signal building block, it is very difficult to test due to internal analog blocks and signals. In this paper, we propose a new PLL BIST (built-in self test) using the distorted frequency detector that uses only internal digital signals. The proposed BIST does not need to load any analog nodes of the PLL. Therefore, it provides an efficient defect-oriented structural test scheme, reduced area overhead, and improved test quality compared with previous approaches.

Diversified pulse generation from frequency shifted feedback Tm-doped fibre lasers.

PubMed

Chen, He; Chen, Sheng-Ping; Jiang, Zong-Fu; Hou, Jing

2016-05-19

Pulsed fibre lasers operating in the eye-safe 2 μm spectral region have numerous potential applications in areas such as remote sensing, medicine, mid-infrared frequency conversion, and free-space communication. Here, for the first time, we demonstrate versatile 2 μm ps-ns pulses generation from Tm-based fibre lasers based on frequency shifted feedback and provide a comprehensive report of their special behaviors. The lasers are featured with elegant construction and the unparalleled capacity of generating versatile pulses. The self-starting mode-locking is initiated by an intra-cavity acousto-optical frequency shifter. Diversified mode-locked pulse dynamics were observed by altering the pump power, intra-cavity polarization state and cavity structure, including as short as 8 ps single pulse sequence, pulse bundle state and up to 12 nJ, 3 ns nanosecond rectangular pulse. A reflective nonlinear optical loop mirror was introduced to successfully shorten the pulses from 24 ps to 8 ps. Beside the mode-locking operation, flexible Q-switching and Q-switched mode-locking operation can also be readily achieved in the same cavity. Up to 78 μJ high energy nanosecond pulse can be generated in this regime. Several intriguing pulse dynamics are characterized and discussed.

Heterodyne optical phase-locking of extended-cavity semiconductor lasers at 9 GHz

NASA Astrophysics Data System (ADS)

Santarelli, G.; Clairon, A.; Lea, S. N.; Tino, G. M.

1994-01-01

In order to stimulate atomic velocity-selective Raman transitions on the 852 nm caesium D 2 line in an atomic fountain clock, two extended-cavity diode lasers have been optically phase-locked at a frequency offset of 9.192 GHz. The measured linewidth (fwhm) of the free-running lasers is 50 kHz. The phase-locked loop bandwidth, evaluated by observing the frequency noise spectrum, is 3.7 MHz and the phase error variance is found to be no more than 4 × 10 -3 rad 2.

Analysis and experimental demonstration of conformal adaptive phase-locked fiber array for laser communications and beam projection applications

NASA Astrophysics Data System (ADS)

Liu, Ling

The primary goal of this research is the analysis, development, and experimental demonstration of an adaptive phase-locked fiber array system for free-space optical communications and laser beam projection applications. To our knowledge, the developed adaptive phase-locked system composed of three fiber collimators (subapertures) with tip-tilt wavefront phase control at each subaperture represents the first reported fiber array system that implements both phase-locking control and adaptive wavefront tip-tilt control capabilities. This research has also resulted in the following innovations: (a) The first experimental demonstration of a phase-locked fiber array with tip-tilt wave-front aberration compensation at each fiber collimator; (b) Development and demonstration of the fastest currently reported stochastic parallel gradient descent (SPGD) system capable of operation at 180,000 iterations per second; (c) The first experimental demonstration of a laser communication link based on a phase-locked fiber array; (d) The first successful experimental demonstration of turbulence and jitter-induced phase distortion compensation in a phase-locked fiber array optical system; (e) The first demonstration of laser beam projection onto an extended target with a randomly rough surface using a conformal adaptive fiber array system. Fiber array optical systems, the subject of this study, can overcome some of the draw-backs of conventional monolithic large-aperture transmitter/receiver optical systems that are usually heavy, bulky, and expensive. The primary experimental challenges in the development of the adaptive phased-locked fiber-array included precise (<5 microrad) alignment of the fiber collimators and development of fast (100kHz-class) phase-locking and wavefront tip-tilt control systems. The precise alignment of the fiber collimator array is achieved through a specially developed initial coarse alignment tool based on high precision piezoelectric picomotors and a dynamic fine alignment mechanism implemented with specially designed and manufactured piezoelectric fiber positioners. Phase-locking of the fiber collimators is performed by controlling the phases of the output beams (beamlets) using integrated polarization-maintaining (PM) fiber-coupled LiNbO3 phase shifters. The developed phase-locking controllers are based on either the SPGD algorithm or the multi-dithering technique. Subaperture wavefront phase tip-tilt control is realized using piezoelectric fiber positioners that are controlled using a computer-based SPGD controller. Both coherent (phase-locked) and incoherent beam combining in the fiber array system are analyzed theoretically and experimentally. Two special fiber-based beam-combining testbeds have been built to demonstrate the technical feasibility of phase-locking compensation prior to free-space operation. In addition, the reciprocity of counter-propagating beams in a phase-locked fiber array system has been investigated. Coherent beam combining in a phase-locking system with wavefront phase tip-tilt compensation at each subaperture is successfully demonstrated when laboratory-simulated turbulence and wavefront jitters are present in the propagation path of the beamlets. In addition, coherent beam combining with a non-cooperative extended target in the control loop is successfully demonstrated.

Loop-locked coherent population trapping magnetometer based on a fiber electro-optic modulator.

PubMed

Hu, Yong; Feng, Y Y; Xu, Chi; Xue, H B; Sun, Li

2014-04-01

We have set up a coherent population trapping (CPT)-based magnetometer prototype with the D1 line of ⁸⁷Rb atoms. The dichromatic light field is derived from a fiber electro-optic modulator (FEOM) connected to an external cavity laser diode. A CPT resonance signal with a 516 Hz linewidth is observed. By feeding back the derivative of the resonance curve to the FEOM with a proportional integral controller, of which the voltage output is directly converted to the measured magnetic field intensity, the resonance peak is locked to the environmental magnetic field. The measurement data we have achieved are well matched with the data measured by a commercial fluxgate magnetometer within 2 nT, and the sensitivity is better than 8 pT/√Hz in a parallel B field.

Generation of a CW local oscillator signal using a stabilized injection locked semiconductor laser

NASA Astrophysics Data System (ADS)

Pezeshki, Jonah Massih

In high speed-communications, it is desirable to be able to detect small signals while maintaining a low bit-error rate. Conventional receivers for high-speed fiber optic networks are Amplified Direct Detectors (ADDs) that use erbium-doped fiber amplifiers (EDFAs) before the detector to achieve a suitable sensitivity. In principle, a better method for obtaining the maximum possible signal to noise ratio is through the use of homodyne detection. The major difficulty in implementing a homodyne detection system is the generation of a suitable local oscillator signal. This local oscillator signal must be at the same frequency as the received data signal, as well as be phase coherent with it. To accomplish this, a variety of synchronization techniques have been explored, including Optical Phase-Lock Loops (OPLL), Optical Injection Locking (OIL) with both Fabry-Perot and DFB lasers, and an Optical Injection Phase-Lock Loop (OIPLL). For this project I have implemented a method for regenerating a local oscillator from a portion of the received optical signal. This regenerated local oscillator is at the same frequency, and is phase coherent with, the received optical signal. In addition, we show that the injection locking process can be electronically stabilized by using the modulation transfer ratio of the slave laser as a monitor, given either a DFB or Fabry-Perot slave laser. We show that this stabilization technique maintains injection lock (given a locking range of ˜1GHz) for laser drift much greater than what is expected in a typical transmission system. In addition, we explore the quality of the output of the slave laser, and analyze its suitability as a local oscillator signal for a homodyne receiver.

Wideband and high-gain frequency stabilization of a 100-W injection-locked Nd:YAG laser for second-generation gravitational wave detectors.

PubMed

Ohmae, Noriaki; Moriwaki, Shigenori; Mio, Norikatsu

2010-07-01

Second-generation gravitational wave detectors require a highly stable laser with an output power greater than 100 W to attain their target sensitivity. We have developed a frequency stabilization system for a 100-W injection-locked Nd:YAG (yttrium aluminum garnet) laser. By placing an external wideband electro-optic modulator used as a fast-frequency actuator in the optical path of the slave output, we can circumvent a phase delay in the frequency control loop originating from the pole of an injection-locked slave cavity. Thus, we have developed an electro-optic modulator made of a MgO-doped stoichiometric LiNbO(3) crystal. Using this modulator, we achieve a frequency control bandwidth of 800 kHz and a control gain of 180 dB at 1 kHz. These values satisfy the requirement for a laser frequency control loop in second-generation gravitational wave detectors.

Precision and fast wavelength tuning of a dynamically phase-locked widely-tunable laser.

PubMed

Numata, Kenji; Chen, Jeffrey R; Wu, Stewart T

2012-06-18

We report a precision and fast wavelength tuning technique demonstrated for a digital-supermode distributed Bragg reflector laser. The laser was dynamically offset-locked to a frequency-stabilized master laser using an optical phase-locked loop, enabling precision fast tuning to and from any frequencies within a ~40-GHz tuning range. The offset frequency noise was suppressed to the statically offset-locked level in less than ~40 μs upon each frequency switch, allowing the laser to retain the absolute frequency stability of the master laser. This technique satisfies stringent requirements for gas sensing lidars and enables other applications that require such well-controlled precision fast tuning.

Phase locking of a 2.7 THz quantum cascade laser to a microwave reference.

PubMed

Khosropanah, P; Baryshev, A; Zhang, W; Jellema, W; Hovenier, J N; Gao, J R; Klapwijk, T M; Paveliev, D G; Williams, B S; Kumar, S; Hu, Q; Reno, J L; Klein, B; Hesler, J L

2009-10-01

We demonstrate the phase locking of a 2.7 THz metal-metal waveguide quantum cascade laser (QCL) to an external microwave signal. The reference is the 15th harmonic, generated by a semiconductor superlattice nonlinear device, of a signal at 182 GHz, which itself is generated by a multiplier chain (x12) from a microwave synthesizer at approximately 15 GHz. Both laser and reference radiations are coupled into a bolometer mixer, resulting in a beat signal, which is fed into a phase-lock loop. The spectral analysis of the beat signal confirms that the QCL is phase locked. This result opens the possibility to extend heterodyne interferometers into the far-infrared range.

Common mode frequency instability in internally phase-locked terahertz quantum cascade lasers.

PubMed

Wanke, M C; Grine, A D; Fuller, C T; Nordquist, C D; Cich, M J; Reno, J L; Lee, Mark

2011-11-21

Feedback from a diode mixer integrated into a 2.8 THz quantum cascade laser (QCL) was used to phase lock the difference frequencies (DFs) among the Fabry-Perot (F-P) longitudinal modes of a QCL. Approximately 40% of the DF power was phase locked, consistent with feedback loop bandwidth of 10 kHz and phase noise bandwidth ~0.5 MHz. While the locked DF signal has ≤ 1 Hz linewidth and negligible drift over ~30 min, mixing measurements between two QCLs and between a QCL and molecular gas laser show that the common mode frequency stability is no better than a free-running QCL. © 2011 Optical Society of America

Phase Locking of a 2.7 THz Quantum Cascade Laser to a Microwave Reference

NASA Technical Reports Server (NTRS)

Khosropanah, P.; Baryshev, A.; Zhang, W.; Jellema, W.; Hovenier, J. N.; Gao, J. R.; Klapwijk, T. M.; Paveliev, D. G.; Williams, B. S.; Hu, Q.;

Dual-pulses and harmonic patterns of a square-wave soliton in passively mode-locked fiber laser

NASA Astrophysics Data System (ADS)

Ma, Wanzhuo; Wang, Tianshu; Su, Qingchao; Zhang, Jing; Jia, Qingsong; Jiang, Huilin

2018-06-01

We demonstrate a square-wave soliton pulse passively mode-locked fiber laser. The mode-locked pulses are achieved by using a nonlinear amplifying loop mirror. Single-pulse operation at a fundamental repetition rate of 3.2 MHz is obtained. The optical spectrum presents the soliton feature of several sidebands. The pulse duration expands with increasing pump power, but the amplitude hardly varies. Pulse breaking occurs and a stable dual-pulse is obtained with a fixed interval of 48 ns. Harmonic mode-locked states can be achieved when the total pump power is higher than 740 mW. The harmonic pulses can also operate in both single-pulse and dual-pulse states.

A microprocessor based portable bolt tension monitor

NASA Technical Reports Server (NTRS)

Perey, D. F.

1991-01-01

A bolt tension monitor (BTM) which uses ultrasonics and a pulsed phase locked loop circuit to measure load-induced acoustic phase shifts which are independent of friction is described. The BTM makes it possible to measure the load in a bolt that was tightened at some time in the past. This capability to recertify a load after-the-fact will help to insure the integrity of a bolted joint.

A bibliography of the theory and application of the phase-lock principle

NASA Technical Reports Server (NTRS)

Lindsey, W. C.; Tausworthe, R. C.

1973-01-01

A literature search was conducted in an effort to collect and compile as many references on the phase-locked loop as possible. Although not all inclusive, a comprehensive listing of approximately 800 references covering the past two decades of work reported throughout the world are presented. The compilation is given in two parts: first by categories, and then alphabetically by authors.

Fringe pattern demodulation with a two-dimensional digital phase-locked loop algorithm.

PubMed

Gdeisat, Munther A; Burton, David R; Lalor, Michael J

2002-09-10

A novel technique called a two-dimensional digital phase-locked loop (DPLL) for fringe pattern demodulation is presented. This algorithm is more suitable for demodulation of fringe patterns with varying phase in two directions than the existing DPLL techniques that assume that the phase of the fringe patterns varies only in one direction. The two-dimensional DPLL technique assumes that the phase of a fringe pattern is continuous in both directions and takes advantage of the phase continuity; consequently, the algorithm has better noise performance than the existing DPLL schemes. The two-dimensional DPLL algorithm is also suitable for demodulation of fringe patterns with low sampling rates, and it outperforms the Fourier fringe analysis technique in this aspect.

Digital second-order phase-locked loop

NASA Technical Reports Server (NTRS)

Holes, J. K.; Carl, C.; Tegnelia, C. R. (Inventor)

1973-01-01

A digital second-order phase-locked loop is disclosed in which a counter driven by a stable clock pulse source is used to generate a reference waveform of the same frequency as an incoming waveform, and to sample the incoming waveform at zero-crossover points. The samples are converted to digital form and accumulated over M cycles, reversing the sign of every second sample. After every M cycles, the accumulated value of samples is hard limited to a value SGN = + or - 1 and multiplied by a value delta sub 1 equal to a number of n sub 1 of fractions of a cycle. An error signal is used to advance or retard the counter according to the sign of the sum by an amount equal to the sum.

Quantizing and sampling considerations in digital phased-locked loops

NASA Technical Reports Server (NTRS)

Hurst, G. T.; Gupta, S. C.

1974-01-01

The quantizer problem is first considered. The conditions under which the uniform white sequence model for the quantizer error is valid are established independent of the sampling rate. An equivalent spectral density is defined for the quantizer error resulting in an effective SNR value. This effective SNR may be used to determine quantized performance from infinitely fine quantized results. Attention is given to sampling rate considerations. Sampling rate characteristics of the digital phase-locked loop (DPLL) structure are investigated for the infinitely fine quantized system. The predicted phase error variance equation is examined as a function of the sampling rate. Simulation results are presented and a method is described which enables the minimum required sampling rate to be determined from the predicted phase error variance equations.

One way Doppler Extractor. Volume 2: Digital VCO technique

NASA Technical Reports Server (NTRS)

Nossen, E. J.; Starner, E. R.

1974-01-01

A feasibility analysis and trade-offs for a one-way Doppler extractor using digital VCO techniques is presented. The method of Doppler measurement involves the use of a digital phase lock loop; once this loop is locked to the incoming signal, the precise frequency and hence the Doppler component can be determined directly from the contents of the digital control register. The only serious error source is due to internally generated noise. Techniques are presented for minimizing this error source and achieving an accuracy of 0.01 Hz in a one second averaging period. A number of digitally controlled oscillators were analyzed from a performance and complexity point of view. The most promising technique uses an arithmetic synthesizer as a digital waveform generator.

Radiation Tolerant, Low Noise Phase Locked Loops in 65 nm CMOS Technology

NASA Astrophysics Data System (ADS)

Prinzie, Jeffrey; Christiansen, Jorgen; Moreira, Paulo; Steyaert, Michiel; Leroux, Paul

2018-04-01

This work presents an introduction to radiation hardened Phase Locked Loops (PLLs) for nuclear and high-energy physics application. An experimental circuit has been fabricated and irradiated with Xrays up to 600 Mrad. Heavy ions with an LET between 3.2 and 69.2 MeV.cm2/mg were used to verify the SEU cross section of the devices. A Two-photon Absorption (TPA) laser facility has been used to provide detailed results on the SEU sensitivity. The presented circuit employs TMR in the digital logic and an asynchronous phase-frequency detector (PFD) is presented. The PLL has a ringand LC-oscillator to be compared experimentally. The circuit has been fabricated in a 65 nm CMOS technology.

New spatial diversity equalizer based on PLL

NASA Astrophysics Data System (ADS)

Rao, Wei

2011-10-01

A new Spatial Diversity Equalizer (SDE) based on phase-locked loop (PLL) is proposed to overcome the inter-symbol interference (ISI) and phase rotations simultaneously in the digital communication system. The proposed SDE consists of equal gain combining technique based on a famous blind equalization algorithm constant modulus algorithm (CMA) and a PLL. Compared with conventional SDE, the proposed SDE has not only faster convergence rate and lower residual error but also the ability to recover carrier phase rotation. The efficiency of the method is proved by computer simulation.

Direct phase-locking of a 8.6-μm quantum cascade laser to a mid-IR optical frequency comb: application to precision spectroscopy of N2O.

PubMed

Gambetta, Alessio; Cassinerio, Marco; Coluccelli, Nicola; Fasci, Eugenio; Castrillo, Antonio; Gianfrani, Livio; Gatti, Davide; Marangoni, Marco; Laporta, Paolo; Galzerano, Gianluca

2015-02-01

We developed a high-precision spectroscopic system at 8.6 μm based on direct heterodyne detection and phase-locking of a room-temperature quantum-cascade-laser against an harmonic, 250-MHz mid-IR frequency comb obtained by difference-frequency generation. The ∼30  dB signal-to-noise ratio of the detected beat-note together with the achieved closed-loop locking bandwidth of ∼500  kHz allows for a residual integrated phase noise of 0.78 rad (1 Hz-5 MHz), for an ultimate resolution of ∼21  kHz, limited by the measured linewidth of the mid-IR comb. The system was used to perform absolute measurement of line-center frequencies for the rotational components of the ν2 vibrational band of N2O, with a relative precision of 3×10(-10).

Chip Scale Atomic Resonator Frequency Stabilization System With Ultra-Low Power Consumption for Optoelectronic Oscillators.

PubMed

Zhao, Jianye; Zhang, Yaolin; Lu, Haoyuan; Hou, Dong; Zhang, Shuangyou; Wang, Zhong

2016-07-01

We present a long-term chip scale stabilization scheme for optoelectronic oscillators (OEOs) based on a rubidium coherent population trapping (CPT) atomic resonator. By locking a single mode of an OEO to the (85)Rb 3.035-GHz CPT resonance utilizing an improved phase-locked loop (PLL) with a PID regulator, we achieved a chip scale frequency stabilization system for the OEO. The fractional frequency stability of the stabilized OEO by overlapping Allan deviation reaches 6.2 ×10(-11) (1 s) and  ∼ 1.45 ×10 (-11) (1000 s). This scheme avoids a decrease in the extra phase noise performance induced by the electronic connection between the OEO and the microwave reference in common injection locking schemes. The total physical package of the stabilization system is [Formula: see text] and the total power consumption is 400 mW, which provides a chip scale and portable frequency stabilization approach with ultra-low power consumption for OEOs.

Modeling of mode-locked fiber lasers

NASA Astrophysics Data System (ADS)

Shaulov, Gary

This thesis presents the results of analytical and numerical simulations of mode-locked fiber lasers and their components: multiple quantum well saturable absorbers and nonlinear optical loop mirrors. Due to the growing interest in fiber lasers as a compact source of ultrashort pulses there is a need to develop a full understanding of the advantages and limitations of the different mode-locked techniques. The mode-locked fiber laser study performed in this thesis can be used to optimize the design and performance of mode-locked fiber laser systems. A group at Air Force Research Laboratory reported a fiber laser mode-locked by multiple quantum well (MQW) saturable absorber with stable pulses generated as short as 2 ps [21]. The laser cavity incorporates a chirped fiber Bragg grating as a dispersion element; our analysis showed that the laser operates in the soliton regime. Soliton perturbation theory was applied and conditions for stable pulse operation were investigated. Properties of MQW saturable absorbers and their effect on cavity dynamics were studied and the cases of fast and slow saturable absorbers were considered. Analytical and numerical results are in a good agreement with experimental data. In the case of the laser cavity with a regular fiber Bragg grating, the properties of MQW saturable absorbers dominate the cavity dynamics. It was shown that despite the lack of a soliton shaping mechanism, there is a regime in parameter space where stable or quasi-stable solitary waves solutions can exist. Further a novel technique of fiber laser mode-locking by nonlinear polarization rotation was proposed. Polarization rotation of vector solitons was simulated in a birefringent nonlinear optical loop mirror (NOLM) and the switching characteristics of this device was studied. It was shown that saturable absorber-like action of NOLM allows mode-locked operation of the two fiber laser designs. Laser cavity designs were proposed: figure-eight-type and sigma-type cavity.

A recursive solution for a fading memory filter derived from Kalman filter theory

NASA Technical Reports Server (NTRS)

Statman, J. I.

1986-01-01

A simple recursive solution for a class of fading memory tracking filters is presented. A fading memory filter provides estimates of filter states based on past measurements, similar to a traditional Kalman filter. Unlike a Kalman filter, an exponentially decaying weight is applied to older measurements, discounting their effect on present state estimates. It is shown that Kalman filters and fading memory filters are closely related solutions to a general least squares estimator problem. Closed form filter transfer functions are derived for a time invariant, steady state, fading memory filter. These can be applied in loop filter implementation of the Deep Space Network (DSN) Advanced Receiver carrier phase locked loop (PLL).

Proceedings of the International Symposium on the Structure and Properties of Dislocations in Semiconductors (6th) held in Oxford (England) 5-8 April 1989: Structure and Properties of Dislocations in Semiconductors 1989

DTIC Science & Technology

1989-04-08

now good experimental data on the effects of impurities, including locking by non-electrical xii Preface impurities, and the effect of electrically... locks which result from the interaction of the gliding dislocations. As a matter of fact, these dislocation configurations look similar to those...loop on the go° partial. Structure of grain boundaries and dislocations 3 2.2. Lomer-Cottrell lock : a/2>. Two 60’ dislocations can react and give

High-speed electronic beam steering using injection locking of a laser-diode array

NASA Astrophysics Data System (ADS)

Swanson, E. A.; Abbas, G. L.; Yang, S.; Chan, V. W. S.; Fujimoto, J. G.

1987-01-01

High-speed electronic steering of the output beam of a 10-stripe laser-diode array is reported. The array was injection locked to a single-frequency laser diode. High-speed steering of the locked 0.5-deg-wide far-field lobe is demonstrated either by modulating the injection current of the array or by modulating the frequency of the master laser. Closed-loop tracking bandwidths of 70 kHz and 3 MHz, respectively, were obtained. The beam-steering bandwidths are limited by the FM responses of the modulated devices for both techniques.

Self-Nulling Lock-in Detection Electronics for Capacitance Probe Electrometer

NASA Technical Reports Server (NTRS)

Blaes, Brent R.; Schaefer, Rembrandt T.

2012-01-01

A multi-channel electrometer voltmeter that employs self-nulling lock-in detection electronics in conjunction with a mechanical resonator with noncontact voltage sensing electrodes has been developed for space-based measurement of an Internal Electrostatic Discharge Monitor (IESDM). The IESDM is new sensor technology targeted for integration into a Space Environmental Monitor (SEM) subsystem used for the characterization and monitoring of deep dielectric charging on spacecraft. Use of an AC-coupled lock-in amplifier with closed-loop sense-signal nulling via generation of an active guard-driving feedback voltage provides the resolution, accuracy, linearity and stability needed for long-term space-based measurement of the IESDM. This implementation relies on adjusting the feedback voltage to drive the sense current received from the resonator s variable-capacitance-probe voltage transducer to approximately zero, as limited by the signal-to-noise performance of the loop electronics. The magnitude of the sense current is proportional to the difference between the input voltage being measured and the feedback voltage, which matches the input voltage when the sense current is zero. High signal-to-noise-ratio (SNR) is achieved by synchronous detection of the sense signal using the correlated reference signal derived from the oscillator circuit that drives the mechanical resonator. The magnitude of the feedback voltage, while the loop is in a settled state with essentially zero sense current, is an accurate estimate of the input voltage being measured. This technique has many beneficial attributes including immunity to drift, high linearity, high SNR from synchronous detection of a single-frequency carrier selected to avoid potentially noisy 1/f low-frequency spectrum of the signal-chain electronics, and high accuracy provided through the benefits of a driven shield encasing the capacitance- probe transducer and guarded input triaxial lead-in. Measurements obtained from a 2- channel prototype electrometer have demonstrated good accuracy (|error| < 0.2 V) and high stability. Twenty-four-hour tests have been performed with virtually no drift. Additionally, 5,500 repeated one-second measurements of 100 V input were shown to be approximately normally distributed with a standard deviation of 140 mV.

Wireless Strain Measurement with a Micromachined Magnetoelastic Resonator Using Ringdown Frequency Locking

PubMed Central

Green, Scott R.; Gianchandani, Yogesh B.

2017-01-01

Resonant magnetoelastic devices are widely used as anti-theft tags and are also being investigated for a range of sensing applications. The vast majority of magnetoelastic devices are operated at resonance, and rely upon an external interface to wirelessly detect the resonant frequency, and other characteristics. For micromachined devices, this detection method must accommodate diminished signal strength and elevated resonant frequencies. Feedthrough of the interrogating stimulus to the detector also presents a significant challenge. This paper describes a method of interrogating wireless magnetoelastic strain sensors using a new frequency-lock approach. Following a brief excitation pulse, the sensor ring-down is analyzed and a feedback loop is used to match the excitation frequency and the resonant frequency. Data acquisition hardware is used in conjunction with custom software to implement the frequency-lock loop. Advantages of the method include temporal isolation of interrogating stimulus from the sensor response and near real-time tracking of resonant frequencies. The method was investigated using a family of wireless strain sensors with resonant frequencies ranging from 120 to 240 kHz. Strain levels extending to 3.5 mstrain and sensitivities up to 14300 ppm/mstrain were measured with response times faster than 0.5 s. The standard deviation of the locked frequency did not exceed 0.1%. PMID:28713873

Narrow linewidth comb realized with a mode-locked fiber laser using an intra-cavity waveguide electro-optic modulator for high-speed control.

PubMed

Iwakuni, Kana; Inaba, Hajime; Nakajima, Yoshiaki; Kobayashi, Takumi; Hosaka, Kazumoto; Onae, Atsushi; Hong, Feng-Lei

2012-06-18

We have developed an optical frequency comb using a mode-locked fiber ring laser with an intra-cavity waveguide electro-optic modulator controlling the optical length in the laser cavity. The mode-locking is achieved with a simple ring configuration and a nonlinear polarization rotation mechanism. The beat note between the laser and a reference laser and the carrier envelope offset frequency of the comb were simultaneously phase locked with servo bandwidths of 1.3 MHz and 900 kHz, respectively. We observed an out-of-loop beat between two identical combs, and obtained a coherent δ-function peak with a signal to noise ratio of 70 dB/Hz.

Phase-locking of a 2.7-THz Quantum Cascade Laser to a Microwave Reference

NASA Astrophysics Data System (ADS)

Baryshev, A. M.; Khosropanah, P.; Zhang, W.; Jellema, W.; Hovenier, J. N.; Gao, J. R.; Klapwijk, T. M.; Paveliev, D. G.; William, B. S.; Kumar, S.; Hu, Q.; Reno, J. L.; Klein, B.; Hesler, J. L.

2009-04-01

We demonstrate phase-locking of a 2.7-THz metal-metal waveguide quantum cascade laser (QCL) to an external microwave signal. The reference is the 15th harmonic, generated by a semiconductor superlattice nonlinear device, of a signal at 182 GHz, which itself is generated by a multiplier-chain (x2x3x2) from a microwave synthesizer at 15 GHz. Both laser and reference radiations are coupled into a hot electron bolometer mixer, resulting in a beat signal, which is fed into a phase-lock loop. Spectral analysis of the beat signal (see fig. 1) confirms that the QCL is phase locked. This result opens the possibility to extend heterodyne interferometers into the far-infrared range.

Reconfigurable firmware-defined radios synthesized from standard digital logic cells

NASA Astrophysics Data System (ADS)

Faisal, Muhammad; Park, Youngmin; Wentzloff, David D.

2011-06-01

This paper presents recent work on reconfigurable all-digital radio architectures. We leverage the flexibility and scalability of synthesized digital cells to construct reconfigurable radio architectures that consume significantly less power than a software defined radio implementing similar architectures. We present two prototypes of such architectures that can receive and demodulate FM and FRS band signals. Moreover, a radio architecture based on a reconfigurable alldigital phase-locked loop for coherent demodulation is presented.

Improved frequency/voltage converters for fast quartz crystal microbalance applications.

PubMed

Torres, R; García, J V; Arnau, A; Perrot, H; Kim, L To Thi; Gabrielli, C

2008-04-01

The monitoring of frequency changes in fast quartz crystal microbalance (QCM) applications is a real challenge in today's instrumentation. In these applications, such as ac electrogravimetry, small frequency shifts, in the order of tens of hertz, around the resonance of the sensor can occur up to a frequency modulation of 1 kHz. These frequency changes have to be monitored very accurately both in magnitude and phase. Phase-locked loop techniques can be used for obtaining a high performance frequency/voltage converter which can provide reliable measurements. Sensitivity higher than 10 mVHz, for a frequency shift resolution of 0.1 Hz, with very low distortion in tracking both the magnitude and phase of the frequency variations around the resonance frequency of the sensor are required specifications. Moreover, the resonance frequency can vary in a broad frequency range from 5 to 10 MHz in typical QCM sensors, which introduces an additional difficulty. A new frequency-voltage conversion system based on a double tuning analog-digital phase-locked loop is proposed. The reported electronic characterization and experimental results obtained with conducting polymers prove its reliability for ac-electrogravimetry measurements and, in general, for fast QCM applications.

Phase-Locked Loop for Precisely Timed Acoustic Stimulation during Sleep

PubMed Central

Santostasi, Giovanni; Malkani, Roneil; Riedner, Brady; Bellesi, Michele; Tononi, Giulio; Paller, Ken A.; Zee, Phyllis C.

2016-01-01

Background A Brain-Computer Interface could potentially enhance the various benefits of sleep. New Method We describe a strategy for enhancing slow-wave sleep (SWS) by stimulating the sleeping brain with periodic acoustic stimuli that produce resonance in the form of enhanced slow-wave activity in the electroencephalogram (EEG). The system delivers each acoustic stimulus at a particular phase of an electrophysiological rhythm using a Phase-Locked Loop (PLL). Results The PLL is computationally economical and well suited to follow and predict the temporal behavior of the EEG during slow-wave sleep. Comparison with Existing Methods Acoustic stimulation methods may be able to enhance SWS without the risks inherent in electrical stimulation or pharmacological methods. The PLL method differs from other acoustic stimulation methods that are based on detecting a single slow wave rather than modeling slow-wave activity over an extended period of time. Conclusions By providing real-time estimates of the phase of ongoing EEG oscillations, the PLL can rapidly adjust to physiological changes, thus opening up new possibilities to study brain dynamics during sleep. Future application of these methods hold promise for enhancing sleep quality and associated daytime behavior and improving physiologic function. PMID:26617321

Fractional-N phase-locked loop for split and direct automatic frequency control in A-GPS

NASA Astrophysics Data System (ADS)

Park, Chester Sungchung; Park, Sungkyung

2018-07-01

A low-power mixed-signal phase-locked loop (PLL) is modelled and designed for the DigRF interface between the RF chip and the modem chip. An assisted-GPS or A-GPS multi-standard system includes the DigRF interface and uses the split automatic frequency control (AFC) technique. The PLL circuitry uses the direct AFC technique and is based on the fractional-N architecture using a digital delta-sigma modulator along with a digital counter, fulfilling simple ultra-high-resolution AFC with robust digital circuitry and its timing. Relative to the output frequency, the measured AFC resolution or accuracy is <5 parts per billion (ppb) or on the order of a Hertz. The cycle-to-cycle rms jitter is <6 ps and the typical settling time is <30 μs. A spur reduction technique is adopted and implemented as well, demonstrating spur reduction without employing dithering. The proposed PLL includes a low-leakage phase-frequency detector, a low-drop-out regulator, power-on-reset circuitry and precharge circuitry. The PLL is implemented in a 90-nm CMOS process technology with 1.2 V single supply. The overall PLL draws about 1.1 mA from the supply.

Improved frequency/voltage converters for fast quartz crystal microbalance applications

NASA Astrophysics Data System (ADS)

Torres, R.; García, J. V.; Arnau, A.; Perrot, H.; Kim, L. To Thi; Gabrielli, C.

2008-04-01

The monitoring of frequency changes in fast quartz crystal microbalance (QCM) applications is a real challenge in today's instrumentation. In these applications, such as ac electrogravimetry, small frequency shifts, in the order of tens of hertz, around the resonance of the sensor can occur up to a frequency modulation of 1kHz. These frequency changes have to be monitored very accurately both in magnitude and phase. Phase-locked loop techniques can be used for obtaining a high performance frequency/voltage converter which can provide reliable measurements. Sensitivity higher than 10mV/Hz, for a frequency shift resolution of 0.1Hz, with very low distortion in tracking both the magnitude and phase of the frequency variations around the resonance frequency of the sensor are required specifications. Moreover, the resonance frequency can vary in a broad frequency range from 5to10MHz in typical QCM sensors, which introduces an additional difficulty. A new frequency-voltage conversion system based on a double tuning analog-digital phase-locked loop is proposed. The reported electronic characterization and experimental results obtained with conducting polymers prove its reliability for ac-electrogravimetry measurements and, in general, for fast QCM applications.

The Ionospheric Scintillation Effects on the BeiDou Signal Receiver

PubMed Central

He, Zhijun; Zhao, Hongbo; Feng, Wenquan

2016-01-01

Irregularities in the Earth’s ionosphere can make the amplitude and phase of radio signals fluctuate rapidly, which is known as ionospheric scintillation. Severe ionospheric scintillation could affect the performance of the Global Navigation Satellite System (GNSS). Currently, the Multiple Phase Screen (MPS) technique is widely used in solving problems caused by weak and strong scintillations. Considering that Southern China is mainly located in the area where moderate and intense scintillation occur frequently, this paper built a model based on the MPS technique and discussed the scintillation impacts on China’s BeiDou navigation system. By using the BeiDou B1I signal, this paper analyzed the scintillation effects on the receiver, which includes the acquisition and tracking process. For acquisition process, this paper focused on the correlation peak and acquisition probability. For the tracking process, this paper focused on the carrier tracking loop and the code tracking loop. Simulation results show that under high scintillation intensity, the phase fluctuation could be −1.13 ± 0.087 rad to 1.40 ± 0.087 rad and the relative amplitude fluctuation could be −10 dB to 8 dB. As the scintillation intensity increased, the average correlation peak would decrease more than 8%, which could thus degrade acquisition performance. On the other hand, when the signal-to-noise ratio (SNR) is comparatively lower, the influence of strong scintillation on the phase locked loop (PLL) is much higher than that of weak scintillation. As the scintillation becomes more intense, PLL variance could consequently results in an error of more than 2.02 cm in carrier-phase based ranging. In addition, the delay locked loop (DLL) simulation results indicated that the pseudo-range error caused by strong scintillation could be more than 4 m and the consequent impact on positioning accuracy could be more than 6 m. PMID:27834867

Electronic circuits

NASA Technical Reports Server (NTRS)

1976-01-01

Twenty-nine circuits and circuit techniques developed for communications and instrumentation technology are described. Topics include pulse-code modulation, phase-locked loops, data coding, data recording, detection circuits, logic circuits, oscillators, and amplifiers.

Enhancement of vehicle dynamics via an innovative magnetorheological fluid limited slip differential

NASA Astrophysics Data System (ADS)

Russo, Riccardo; Strano, Salvatore; Terzo, Mario

2016-03-01

A new automotive controllable differential is proposed and tested, firstly in software environment and, successively, following a hardware in the loop procedure based on the employment of the physical prototype. The device is based on the employment of magnetorheological fluid, whose magnetization allows to generate the locking torque and, consequently, the corrective yaw moment. A vehicle model has been derived and adopted for the design of a yaw moment controller based on the sliding mode approach. Some feedbacks requested by the controller have been estimated by means of an extended Kalman filter. The obtained results show the effectiveness of the device in terms of vehicle dynamics improvement. Indeed, the results reached by the vehicle in presence of the new differential confirm the improved performances for both steady and unsteady state manoeuvres. Moreover, the hardware in the loop testing allows to overcome the limits due to the modelling of the differential, fully validating the physical prototype.

A Field-Sweep/Field-Lock System for Superconducting Magnets-Application to High-Field EPR

PubMed Central

Maly, Thorsten; Bryant, Jeff; Ruben, David; Griffin, Robert G.

2007-01-01

We describe a field-lock/field-sweep system for the use in superconducting magnets. The system is based on a commercially available field mapping unit and a custom designed broad-band 1H-NMR probe. The NMR signal of a small water sample is used in a feedback loop to set and control the magnetic field to high accuracy. The current instrumental configuration allows field sweeps of ± 0.4 T and a resolution of up to 10-5 T (0.1 G) and the performance of the system is demonstrated in a high-field electron paramagnetic resonance (EPR) application. The system should also be of utility in other experiments requiring precise and reproducible sweeps of the magnetic field such as DNP, ENDOR or PELDOR. PMID:17027306

A field-sweep/field-lock system for superconducting magnets--Application to high-field EPR.

PubMed

Maly, Thorsten; Bryant, Jeff; Ruben, David; Griffin, Robert G

2006-12-01

We describe a field-lock/field-sweep system for the use in superconducting magnets. The system is based on a commercially available field mapping unit and a custom designed broad-band 1H NMR probe. The NMR signal of a small water sample is used in a feedback loop to set and control the magnetic field to high accuracy. The current instrumental configuration allows field sweeps of +/-0.4 T and a resolution of up to 10(-5) T (0.1 G) and the performance of the system is demonstrated in a high-field electron paramagnetic resonance (EPR) application. The system should also be of utility in other experiments requiring precise and reproducible sweeps of the magnetic field such as DNP, ENDOR or PELDOR.

Portable atomic frequency standard based on coherent population trapping

NASA Astrophysics Data System (ADS)

Shi, Fan; Yang, Renfu; Nian, Feng; Zhang, Zhenwei; Cui, Yongshun; Zhao, Huan; Wang, Nuanrang; Feng, Keming

2015-05-01

In this work, a portable atomic frequency standard based on coherent population trapping is designed and demonstrated. To achieve a portable prototype, in the system, a single transverse mode 795nm VCSEL modulated by a 3.4GHz RF source is used as a pump laser which generates coherent light fields. The pump beams pass through a vapor cell containing atom gas and buffer gas. This vapor cell is surrounded by a magnetic shield and placed inside a solenoid which applies a longitudinal magnetic field to lift the Zeeman energy levels' degeneracy and to separate the resonance signal, which has no first-order magnetic field dependence, from the field-dependent resonances. The electrical control system comprises two control loops. The first one locks the laser wavelength to the minimum of the absorption spectrum; the second one locks the modulation frequency and output standard frequency. Furthermore, we designed the micro physical package and realized the locking of a coherent population trapping atomic frequency standard portable prototype successfully. The short-term frequency stability of the whole system is measured to be 6×10-11 for averaging times of 1s, and reaches 5×10-12 at an averaging time of 1000s.

Digital correlation detector for low-cost Omega navigation

NASA Technical Reports Server (NTRS)

Chamberlin, K. A.

1976-01-01

Techniques to lower the cost of using the Omega global navigation network with phase-locked loops (PLL) were developed. The technique that was accepted as being "optimal" is called the memory-aided phase-locked loop (MAPLL) since it allows operation on all eight Omega time slots with one PLL through the implementation of a random access memory. The receiver front-end and the signals that it transmits to the PLL were first described. A brief statistical analysis of these signals was then made to allow a rough comparison between the front-end presented in this work and a commercially available front-end to be made. The hardware and theory of application of the MAPLL were described, ending with an analysis of data taken with the MAPLL. Some conclusions and recommendations were also given.

Phase error statistics of a phase-locked loop synchronized direct detection optical PPM communication system

NASA Technical Reports Server (NTRS)

Natarajan, Suresh; Gardner, C. S.

1987-01-01

Receiver timing synchronization of an optical Pulse-Position Modulation (PPM) communication system can be achieved using a phased-locked loop (PLL), provided the photodetector output is suitably processed. The magnitude of the PLL phase error is a good indicator of the timing error at the receiver decoder. The statistics of the phase error are investigated while varying several key system parameters such as PPM order, signal and background strengths, and PPL bandwidth. A practical optical communication system utilizing a laser diode transmitter and an avalanche photodiode in the receiver is described, and the sampled phase error data are presented. A linear regression analysis is applied to the data to obtain estimates of the relational constants involving the phase error variance and incident signal power.

Passive mode locking and formation of dissipative solitons in electron oscillators with a bleaching absorber in the feedback loop

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ginzburg, N. S., E-mail: ginzburg@appl.sci-nnov.ru; Kocharovskaya, E. R.; Vilkov, M. N.

The mechanisms of passive mode locking and formation of ultrashort pulses in microwave electron oscillators with a bleaching absorber in the feedback loop have been analyzed. It is shown that in the group synchronism regime in which the translational velocity of particles coincides with the group velocity of the electromagnetic wave, the pulse formation can be described by the equations known in the theory of dissipative solitons. At the same time, the regimes in which the translational velocity of electrons differs from the group velocity and the soliton being formed and moving along the electron beam consecutively (cumulatively) receives energymore » from various electron fractions are optimal for generating pulses with the maximal peak amplitudes.« less

NASA Pioneer: Venus reverse playback telemetry program TR 78-2

NASA Technical Reports Server (NTRS)

Modestino, J. W.; Daut, D. G.; Vickers, A. L.; Matis, K. R.

1978-01-01

During the entry of the Pioneer Venus Atmospheric Probes into the Venus atmosphere, there were several events (RF blackout and data rate changes) which caused the ground receiving equipment to lose lock on the signal. This caused periods of data loss immediately following each one of these disturbing events which lasted until all the ground receiving units (receiver, subcarrier demodulator, symbol synchronizer, and sequential decoder) acquired lock once more. A scheme to recover these data by off-line data processing was implemented. This scheme consisted of receiving the S band signals from the probes with an open loop reciever (requiring no lock up on the signal) in parallel with the closed loop receivers of the real time receiving equipment, down converting the signals to baseband, and recording them on an analog recorder. The off-line processing consisted of playing the analog recording in the reverse direction (starting with the end of the tape) up, converting the signal to S-band, feeding the signal into the "real time" receiving system and recording on digital tape, the soft decisions from the symbol synchronizer.

A novel photonic oscillator

NASA Technical Reports Server (NTRS)

Yao, X. S.; Maleki, L.

1995-01-01

We report a novel oscillator for photonic RF systems. This oscillator is capable of generating high-frequency signals up to 70 GHz in both electrical and optical domains and is a special voltage-controlled oscillator with an optical output port. It can be used to make a phase-locked loop (PLL) and perform all functions that a PLL is capable of for photonic systems. It can be synchronized to a reference source by means of optical injection locking, electrical injection locking, and PLL. It can also be self-phase locked and self-injection locked to generate a high-stability photonic RF reference. Its applications include high-frequency reference regeneration and distribution, high-gain frequency multiplication, comb-frequecy and square-wave generation, carrier recovery, and clock recovery. We anticipate that such photonic voltage-controlled oscillators (VCOs) will be as important to photonic RF systems as electrical VCOs are to electrical RF systems.

Geodetic Secor Satellite

DTIC Science & Technology

1974-06-01

retrans- minied modulation signals. A phase-lock loop was used to provide correlation detection, allowing automatic acquisition and phase tracking at...steel strips, 0.5-inch-wide by 0.009-inch-thick, and formed to a 0.75-inch radius. Each antenne -was plated with silver to imprive con- dutivity...Telemetry Requirements k. Phase Detector Output Requirements 1. Primary Power Requirements m. AM Suppression Requirements n. Data Feedback Loop Gain

Experimental Evaluation of an Invasive Medical Instrument Based on a Displacement Measurement System.

PubMed

Fotiadis, Dimitris A; Astaras, Alexandros; Bamidis, Panagiotis D; Papathanasiou, Kostas; Kalfas, Anestis

2015-09-01

This paper presents a novel method for tracking the position of a medical instrument's tip. The system is based on phase locking a high frequency signal transmitted from the medical instrument's tip to a reference signal. Displacement measurement is established having the loop open, in order to get a low frequency voltage representing the medical instrument's movement; therefore, positioning is established by means of conventional measuring techniques. The voltage-controlled oscillator stage of the phase-locked loop (PLL), combined to an appropriate antenna, comprises the associated transmitter located inside the medical instrument tip. All the other low frequency PLL components, low noise amplifier and mixer, are located outside the human body, forming the receiver part of the system. The operating details of the proposed system were coded in Verilog-AMS. Simulation results indicate robust medical instrument tracking in 1-D. Experimental evaluation of the proposed position tracking system is also presented. The experiments described in this paper are based on a transmitter moving opposite a stationary receiver performing either constant velocity or uniformly accelerated movement, and also together with two stationary receivers performing constant velocity movement again. This latter setup is implemented in order to demonstrate the prototype's accuracy for planar (2-D) motion measurements. Error analysis and time-domain analysis are presented for system performance characterization. Furthermore, preliminary experimental assessment using a saline solution container to more closely approximate the human body as a radio frequency wave transmission medium has proved the system's capability of operating underneath the skin.

A 2-to-48-MHz Phase-Locked Loop

NASA Technical Reports Server (NTRS)

Koudelka, Robert D.

2004-01-01

A 2-to-48-MHz phase-locked loop (PLL), developed for the U.S. space program, meets or exceeds all space shuttle clock electrical interface requirements by taking as its reference a 2-to-48-MHz clock signal and outputting a phaselocked clock signal set at the same frequency as the reference clock with transistor- transistor logic (TTL) voltage levels. Because it is more adaptable than other PLLs, the new PLL can be used in industries that employ signaling devices and as a tool in future space missions. A conventional PLL consists of a phase/frequency detector, loop filter, and voltage-controlled oscillator in which each component exists individually and is integrated into a single device. PLL components phase-lock to a single frequency or to a narrow bandwidth of frequencies. It is this design, however, that prohibits them from maintaining phase lock to a dynamically changing reference clock when a large bandwidth is required a deficiency the new PLL overcomes. Since most PLL components require their voltage-controlled oscillators to operate at greater than 2-MHz frequencies, conventional PLLs often cannot achieve the low-frequency phase lock allowed by the new PLL. The 2-to-48-MHz PLL is built on a wire-wrap board with pins wired to three position jumpers; this makes changing configurations easy. It responds to variations in voltage-controlled oscillator (VCO) ranges, duty cycle, signal-to-noise ratio (SNR), amplitude, and jitter, exceeding design specifications. A consensus state machine, implemented in a VCO range detector which assures the PLL continues to operate in the correct range, is the primary control state machine for the 2-to-48-MHz PLL circuit. By using seven overlapping frequency ranges with hysteresis, the PLL output sets the resulting phase-locked clock signal at a frequency that agrees with the reference clock with TTL voltage levels. As a space-shuttle tool, the new PLL circuit takes the noisy, degraded reference clock signals as input and outputs phase-locked clock signals of the same frequency but with a corrected wave shape. Since its configuration circuit can be easily changed, the new PLL can do the following: readily respond to variations in VCO ranges, duty cycle, SNR, amplitude, and jitter; continuously operate in the correct VCO range because of its consensus state machine; and use its range detector implements to overlap seven frequency ranges with hysteresis, thus giving the current design a flexibility that exceeds anything available at the time of this development. These features will benefit any industry in which safe and timely clock signals are vital to operation.

Phase-Locked Optical Generation of mmW/THz Signals

DTIC Science & Technology

2009-11-01

22 6.2. TIA (Trans-Impedance Amplifier ...24 6.3. Variable gain Amplifier ...loop architectures. Generate models including detector impulse response, feedback amplifier impulse response and laser current tuning response

Control System Damps Vibrations

NASA Technical Reports Server (NTRS)

Kopf, E. H., Jr.; Brown, T. K.; Marsh, E. L.

1983-01-01

New control system damps vibrations in rotating equipment with help of phase-locked-loop techniques. Vibrational modes are controlled by applying suitable currents to drive motor. Control signals are derived from sensors mounted on equipment.

An estimator-predictor approach to PLL loop filter design

NASA Technical Reports Server (NTRS)

Statman, J. I.; Hurd, W. J.

1986-01-01

An approach to the design of digital phase locked loops (DPLLs), using estimation theory concepts in the selection of a loop filter, is presented. The key concept is that the DPLL closed-loop transfer function is decomposed into an estimator and a predictor. The estimator provides recursive estimates of phase, frequency, and higher order derivatives, while the predictor compensates for the transport lag inherent in the loop. This decomposition results in a straightforward loop filter design procedure, enabling use of techniques from optimal and sub-optimal estimation theory. A design example for a particular choice of estimator is presented, followed by analysis of the associated bandwidth, gain margin, and steady state errors caused by unmodeled dynamics. This approach is under consideration for the design of the Deep Space Network (DSN) Advanced Receiver Carrier DPLL.

Design of a Sub-Picosecond Jitter with Adjustable-Range CMOS Delay-Locked Loop for High-Speed and Low-Power Applications

PubMed Central

Abdulrazzaq, Bilal I.; Ibrahim, Omar J.; Kawahito, Shoji; Sidek, Roslina M.; Shafie, Suhaidi; Yunus, Nurul Amziah Md.; Lee, Lini; Halin, Izhal Abdul

2016-01-01

A Delay-Locked Loop (DLL) with a modified charge pump circuit is proposed for generating high-resolution linear delay steps with sub-picosecond jitter performance and adjustable delay range. The small-signal model of the modified charge pump circuit is analyzed to bring forth the relationship between the DLL’s internal control voltage and output time delay. Circuit post-layout simulation shows that a 0.97 ps delay step within a 69 ps delay range with 0.26 ps Root-Mean Square (RMS) jitter performance is achievable using a standard 0.13 µm Complementary Metal-Oxide Semiconductor (CMOS) process. The post-layout simulation results show that the power consumption of the proposed DLL architecture’s circuit is 0.1 mW when the DLL is operated at 2 GHz. PMID:27690040

Timing performance of phased-locked loops in optical pulse position modulation communication systems

NASA Technical Reports Server (NTRS)

Lafaw, D. A.; Gardner, C. S.

1984-01-01

An optical digital communication system requires that an accurate clock signal be available at the receiver for proper synchronization with the transmitted signal. Phase synchronization is especially critical in M-ary pulse position modulation (PPM) systems where the optimum decision scheme is an energy detector which compares the energy in each of M time slots to decide which of M possible words was sent. Timing errors cause energy spillover into adjacent time slots (a form of intersymbol interference) so that only a portion of the signal energy may be attributed to the correct time slot. This effect decreases the effective signal, increases the effective noise, and increases the probability of error. A timing subsystem for a satellite-to-satellite optical PPM communication link is simulated. The receiver employs direct photodetection, preprocessing of the detected signal, and a phase-locked loop for timing synchronization. The variance of the relative phase error is examined under varying signal strength conditions as an indication of loop performance, and simulation results are compared to theoretical calculations.

Timing performance of phased-locked loops in optical pulse position modulation communication systems

NASA Astrophysics Data System (ADS)

Lafaw, D. A.; Gardner, C. S.

1984-08-01

An optical digital communication system requires that an accurate clock signal be available at the receiver for proper synchronization with the transmitted signal. Phase synchronization is especially critical in M-ary pulse position modulation (PPM) systems where the optimum decision scheme is an energy detector which compares the energy in each of M time slots to decide which of M possible words was sent. Timing errors cause energy spillover into adjacent time slots (a form of intersymbol interference) so that only a portion of the signal energy may be attributed to the correct time slot. This effect decreases the effective signal, increases the effective noise, and increases the probability of error. A timing subsystem for a satellite-to-satellite optical PPM communication link is simulated. The receiver employs direct photodetection, preprocessing of the detected signal, and a phase-locked loop for timing synchronization. The variance of the relative phase error is examined under varying signal strength conditions as an indication of loop performance, and simulation results are compared to theoretical calculations.

Scanning SQUID sampler with 40-ps time resolution

NASA Astrophysics Data System (ADS)

Cui, Zheng; Kirtley, John R.; Wang, Yihua; Kratz, Philip A.; Rosenberg, Aaron J.; Watson, Christopher A.; Gibson, Gerald W.; Ketchen, Mark B.; Moler, Kathryn. A.

2017-08-01

Scanning Superconducting QUantum Interference Device (SQUID) microscopy provides valuable information about magnetic properties of materials and devices. The magnetic flux response of the SQUID is often linearized with a flux-locked feedback loop, which limits the response time to microseconds or longer. In this work, we present the design, fabrication, and characterization of a novel scanning SQUID sampler with a 40-ps time resolution and linearized response to periodically triggered signals. Other design features include a micron-scale pickup loop for the detection of local magnetic flux, a field coil to apply a local magnetic field to the sample, and a modulation coil to operate the SQUID sampler in a flux-locked loop to linearize the flux response. The entire sampler device is fabricated on a 2 mm × 2 mm chip and can be scanned over macroscopic planar samples. The flux noise at 4.2 K with 100 kHz repetition rate and 1 s of averaging is of order 1 mΦ0. This SQUID sampler will be useful for imaging dynamics in magnetic and superconducting materials and devices.

Scanning SQUID sampler with 40-ps time resolution.

PubMed

Cui, Zheng; Kirtley, John R; Wang, Yihua; Kratz, Philip A; Rosenberg, Aaron J; Watson, Christopher A; Gibson, Gerald W; Ketchen, Mark B; Moler, Kathryn A

2017-08-01

Scanning Superconducting QUantum Interference Device (SQUID) microscopy provides valuable information about magnetic properties of materials and devices. The magnetic flux response of the SQUID is often linearized with a flux-locked feedback loop, which limits the response time to microseconds or longer. In this work, we present the design, fabrication, and characterization of a novel scanning SQUID sampler with a 40-ps time resolution and linearized response to periodically triggered signals. Other design features include a micron-scale pickup loop for the detection of local magnetic flux, a field coil to apply a local magnetic field to the sample, and a modulation coil to operate the SQUID sampler in a flux-locked loop to linearize the flux response. The entire sampler device is fabricated on a 2 mm × 2 mm chip and can be scanned over macroscopic planar samples. The flux noise at 4.2 K with 100 kHz repetition rate and 1 s of averaging is of order 1 mΦ 0 . This SQUID sampler will be useful for imaging dynamics in magnetic and superconducting materials and devices.

Remotely manageable system for stabilizing femtosecond lasers

NASA Astrophysics Data System (ADS)

Cizek, Martin; Hucl, Vaclav; Smid, Radek; Mikel, Bretislav; Lazar, Josef; Cip, Ondrej

2014-05-01

In the field of precise measurement of optical frequencies, laser spectroscopy and interferometric distance surveying the optical frequency synthesizers (femtosecond combs) are used as optical frequency references. They generate thousands of narrow-linewidth coherent optical frequencies at the same time. The spacing of generated components equals to the repetition frequency of femtosecond pulses of the laser. The position of the comb spectrum has a frequency offset that is derived from carrier to envelope frequency difference. The repetition frequency and mentioned frequency offset belong to main controlled parameters of the optical frequency comb. If these frequencies are electronically locked an ultrastable frequency standard (i.e. H-maser, Cs- or Rb- clock), its relative stability is transferred to the optical frequency domain. We present a complete digitally controlled signal processing chain for phase-locked loop (PLL) control of the offset frequency. The setup is able to overcome some dropouts caused by the femtosecond laser non-stabilities (temperature drifts, ripple noise and electricity spikes). It is designed as a two-stage control loop, where controlled offset frequency is permanently monitored by digital signal processing. In case of dropouts of PLL, the frequency-locked loop keeps the controlled frequency in the required limits. The presented work gives the possibility of long-time operation of femtosecond combs which is necessary when the optical frequency stability measurement of ultra-stable lasers is required. The detailed description of the modern solution of the PLL with remote management is presented.

Engineering evaluations and studies. Report for IUS studies

NASA Technical Reports Server (NTRS)

1981-01-01

The reviews, investigations, and analyses of the Inertial Upper Stage (IUS) Spacecraft Tracking and Data Network (STDN) transponder are reviewed. Carrier lock detector performance for Tracking and Data Relay Satellite System (TDRSS) dual-mode operation is discussed, as is the problem of predicting instantaneous frequency error in the carrier loop. Coastal loop performance analysis is critiqued and the static tracking phase error induced by thermal noise biases is discussed.

Programmable Oscillator

NASA Technical Reports Server (NTRS)

Quirk, Kevin J.; Patawaran, Ferze D.; Nguyen, Danh H.; Lee, Clement G.; Nguyen, Huy

2011-01-01

A programmable oscillator is a frequency synthesizer with an output phase that tracks an arbitrary function. An offset, phase-locked loop circuit is used in combination with an error control feedback loop to precisely control the output phase of the oscillator. To down-convert the received signal, several stages of mixing may be employed with the compensation for the time-base distortion of the carrier occurring at any one of those stages. In the Goldstone Solar System Radar (GSSR), the compensation occurs in the mixing from an intermediate frequency (IF), whose value is dependent on the station and band, to a common IF used in the final stage of down-conversion to baseband. The programmable oscillator (PO) is used in the final stage of down-conversion to generate the IF, along with a time-varying phase component that matches the time-base distortion of the carrier, thus removing it from the final down-converted signal.

Digital PCM bit synchronizer and detector

NASA Astrophysics Data System (ADS)

Moghazy, A. E.; Maral, G.; Blanchard, A.

1980-08-01

A theoretical analysis of a digital self-bit synchronizer and detector is presented and supported by the implementation of an experimental model that utilizes standard TTL logic circuits. This synchronizer is based on the generation of spectral line components by nonlinear filtering of the received bit stream, and extracting the line by a digital phase-locked loop (DPLL). The extracted reference signal instructs a digital matched filter (DMF) data detector. This realization features a short acquisition time and an all-digital structure.

A high-sensitivity push-pull magnetometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Breschi, E.; Grujić, Z. D.; Knowles, P.

2014-01-13

We describe our approach to atomic magnetometry based on the push-pull optical pumping technique. Cesium vapor is pumped and probed by a resonant laser beam whose circular polarization is modulated synchronously with the spin evolution dynamics induced by a static magnetic field. The magnetometer is operated in a phase-locked loop, and it has an intrinsic sensitivity below 20fT/√(Hz), using a room temperature paraffin-coated cell. We use the magnetometer to monitor magnetic field fluctuations with a sensitivity of 300fT/√(Hz)

Vector solitons with polarization instability and locked polarization in a fiber laser

NASA Astrophysics Data System (ADS)

Tang, Dingkang; Zhang, Jian-Guo; Liu, Yuanshan

2012-07-01

We investigate the characteristics of vector solitons with and without locked phase velocities of orthogonal polarization components in a specially-designed laser cavity which is formed by a bidirectional fiber loop together with a semiconductor saturable absorber mirror. The characteristics of the two states are compared in the temporal and spectrum domain, respectively. Both of the two states exhibit the characteristic of mode locking while the two orthogonal polarization components are not resolved. However, for the vector soliton with unlocked phase velocities, identical intensity varies after passing through a polarization beam splitter (PBS) outside the laser cavity. Contrary to the polarization rotation locked vector soliton, the intensity does not change periodically. For the polarization-locked vector soliton (PLVS), the identical pulse intensity is still obtained after passing through the PBS and can be observed on the oscilloscope screen after photodetection. A coupler instead of a circulator is integrated in the laser cavity and strong interaction on the polarization resolved spectra of the PLVS is observed. By comparing the two states, we conclude that interaction between the two orthogonal components contributes to the locked phase velocities.

1.9 μm square-wave passively Q-witched mode-locked fiber laser.

PubMed

Ma, Wanzhuo; Wang, Tianshu; Su, Qingchao; Wang, Furen; Zhang, Jing; Wang, Chengbo; Jiang, Huilin

2018-05-14

We propose and demonstrate the operation of Q-switched mode-locked square-wave pulses in a thulium-holmium co-doped fiber laser. By using a nonlinear amplifying loop mirror, continuous square-wave dissipative soliton resonance pulse is obtained with 4.4 MHz repetition rate. With the increasing pump power, square-wave pulse duration can be broadened from 1.7 ns to 3.2 ns. On such basis Q-switched mode-locked operation is achieved by properly setting the pump power and the polarization controllers. The internal mode-locked pulses in Q-switched envelope still keep square-wave type. The Q-switched repetition rate can be varied from 41.6 kHz to 74 kHz by increasing pump power. The corresponding average single-pulse energy increases from 2.67 nJ to 5.2 nJ. The average peak power is also improved from 0.6 W to 1.1 W when continuous square-wave operation is changed into Q-switched mode-locked operation. It indicates that Q-switched mode-locked operation is an effective method to increase the square-wave pulse energy and peak power.

Modeling and Development of INS-Aided PLLs in a GNSS/INS Deeply-Coupled Hardware Prototype for Dynamic Applications

PubMed Central

Zhang, Tisheng; Niu, Xiaoji; Ban, Yalong; Zhang, Hongping; Shi, Chuang; Liu, Jingnan

2015-01-01

A GNSS/INS deeply-coupled system can improve the satellite signals tracking performance by INS aiding tracking loops under dynamics. However, there was no literature available on the complete modeling of the INS branch in the INS-aided tracking loop, which caused the lack of a theoretical tool to guide the selections of inertial sensors, parameter optimization and quantitative analysis of INS-aided PLLs. This paper makes an effort on the INS branch in modeling and parameter optimization of phase-locked loops (PLLs) based on the scalar-based GNSS/INS deeply-coupled system. It establishes the transfer function between all known error sources and the PLL tracking error, which can be used to quantitatively evaluate the candidate inertial measurement unit (IMU) affecting the carrier phase tracking error. Based on that, a steady-state error model is proposed to design INS-aided PLLs and to analyze their tracking performance. Based on the modeling and error analysis, an integrated deeply-coupled hardware prototype is developed, with the optimization of the aiding information. Finally, the performance of the INS-aided PLLs designed based on the proposed steady-state error model is evaluated through the simulation and road tests of the hardware prototype. PMID:25569751

Wide-band doubler and sine wave quadrature generator

NASA Technical Reports Server (NTRS)

Crow, R. B.

1969-01-01

Phase-locked loop with photoresistive control, which provides both sine and cosine outputs for subcarrier demodulation, serves as a telemetry demodulator signal conditioner with a second harmonic signal for synchronization with the locally generated code.

Spatiotemporal dynamics of a digital phase-locked loop based coupled map lattice system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Banerjee, Tanmoy, E-mail: tbanerjee@phys.buruniv.ac.in; Paul, Bishwajit; Sarkar, B. C.

2014-03-15

We explore the spatiotemporal dynamics of a coupled map lattice (CML) system, which is realized with a one dimensional array of locally coupled digital phase-locked loops (DPLLs). DPLL is a nonlinear feedback-controlled system widely used as an important building block of electronic communication systems. We derive the phase-error equation of the spatially extended system of coupled DPLLs, which resembles a form of the equation of a CML system. We carry out stability analysis for the synchronized homogeneous solutions using the circulant matrix formalism. It is shown through extensive numerical simulations that with the variation of nonlinearity parameter and coupling strengthmore » the system shows transitions among several generic features of spatiotemporal dynamics, viz., synchronized fixed point solution, frozen random pattern, pattern selection, spatiotemporal intermittency, and fully developed spatiotemporal chaos. We quantify the spatiotemporal dynamics using quantitative measures like average quadratic deviation and spatial correlation function. We emphasize that instead of using an idealized model of CML, which is usually employed to observe the spatiotemporal behaviors, we consider a real world physical system and establish the existence of spatiotemporal chaos and other patterns in this system. We also discuss the importance of the present study in engineering application like removal of clock-skew in parallel processors.« less

Spatiotemporal dynamics of a digital phase-locked loop based coupled map lattice system.

PubMed

Banerjee, Tanmoy; Paul, Bishwajit; Sarkar, B C

2014-03-01

We explore the spatiotemporal dynamics of a coupled map lattice (CML) system, which is realized with a one dimensional array of locally coupled digital phase-locked loops (DPLLs). DPLL is a nonlinear feedback-controlled system widely used as an important building block of electronic communication systems. We derive the phase-error equation of the spatially extended system of coupled DPLLs, which resembles a form of the equation of a CML system. We carry out stability analysis for the synchronized homogeneous solutions using the circulant matrix formalism. It is shown through extensive numerical simulations that with the variation of nonlinearity parameter and coupling strength the system shows transitions among several generic features of spatiotemporal dynamics, viz., synchronized fixed point solution, frozen random pattern, pattern selection, spatiotemporal intermittency, and fully developed spatiotemporal chaos. We quantify the spatiotemporal dynamics using quantitative measures like average quadratic deviation and spatial correlation function. We emphasize that instead of using an idealized model of CML, which is usually employed to observe the spatiotemporal behaviors, we consider a real world physical system and establish the existence of spatiotemporal chaos and other patterns in this system. We also discuss the importance of the present study in engineering application like removal of clock-skew in parallel processors.

Spatiotemporal dynamics of a digital phase-locked loop based coupled map lattice system

NASA Astrophysics Data System (ADS)

Banerjee, Tanmoy; Paul, Bishwajit; Sarkar, B. C.

2014-03-01

We explore the spatiotemporal dynamics of a coupled map lattice (CML) system, which is realized with a one dimensional array of locally coupled digital phase-locked loops (DPLLs). DPLL is a nonlinear feedback-controlled system widely used as an important building block of electronic communication systems. We derive the phase-error equation of the spatially extended system of coupled DPLLs, which resembles a form of the equation of a CML system. We carry out stability analysis for the synchronized homogeneous solutions using the circulant matrix formalism. It is shown through extensive numerical simulations that with the variation of nonlinearity parameter and coupling strength the system shows transitions among several generic features of spatiotemporal dynamics, viz., synchronized fixed point solution, frozen random pattern, pattern selection, spatiotemporal intermittency, and fully developed spatiotemporal chaos. We quantify the spatiotemporal dynamics using quantitative measures like average quadratic deviation and spatial correlation function. We emphasize that instead of using an idealized model of CML, which is usually employed to observe the spatiotemporal behaviors, we consider a real world physical system and establish the existence of spatiotemporal chaos and other patterns in this system. We also discuss the importance of the present study in engineering application like removal of clock-skew in parallel processors.

Optoelectronic frequency discriminated phase tuning technology and its applications

NASA Astrophysics Data System (ADS)

Lin, Gong-Ru; Chang, Yung-Cheng

2000-07-01

By using a phase-tunable optoelectronic phase-locked loop, we are able to continuously change the phase as well as the delay-time of optically distributed microwave clock signals or optical pulse train. The advantages of the proposed technique include such as wide-band operation up to 20GHz, wide-range tuning up to 640 degrees, high tuning resolution of <6x10-2 degree/mV, ultra-low short-term phase fluctuation and drive of 4.7x10-2 degree and 3.4x10- 3 degree/min, good linearity with acceptable deviations, and frequency-independent transferred function with slope of nearly 90 degrees/volt, etc. The novel optoelectronic phase shifter is performed by using a DC-voltage controlled, optoelectronic-mixer-based, frequency-down-converted digital phase-locked-loop. The maximum delay-time is continuously tunable up to 3.9 ns for optical pulses repeated at 500 MHz from a gain-switched laser diode. This corresponds to a delay responsivity of about 0.54 ps/mV. The using of the OEPS as being an optoelectronic delay-time controller for optical pulses is demonstrated with temporal resolution of <0.2 ps. Electro-optic sampling of high-frequency microwave signals by using the in-situ delay-time-tunable pulsed laser as a novel optical probe is primarily reported.

A 65nm CMOS low-power MedRadio-band integer-N cascaded phase-locked loop for implantable medical systems.

PubMed

Wang, Yi-Xiao; Chen, Wei-Ming; Wu, Chung-Yu

2014-01-01

This paper presents a low-power MedRadio-band integer-N phase-locked Loop (PLL) system which is composed of two charge-pump PLLs cascade connected. The PLL provides the operation clock and local carrier signals for an implantable medical electronic system. In addition, to avoid the off-chip crystal oscillator, the 13.56 MHz Industrial, Scientific and Medical (ISM) band signal from the wireless power transmission system is adopted as the input reference signal for the PLL. Ring-based voltage controlled oscillators (VCOs) with current control units are adopted to reduce chip area and power dissipation. The proposed cascaded PLL system is designed and implemented in TSMC 65-nm CMOS technology. The measured jitter for 216.96 MHz signal is 12.23 ps and the phase noise is -65.9 dBc/Hz at 100 kHz frequency offset under 402.926 MHz carrier frequency. The measured power dissipations are 66 μW in the first PLL and 195 μW in the whole system under 1-V supply voltage. The chip area is 0.1088 mm(2) and no off-chip component is required which is suitable for the integration of the implantable medical electronic system.

A low jitter PLL clock used for phase change memory

NASA Astrophysics Data System (ADS)

Xiao, Hong; Houpeng, Chen; Zhitang, Song; Daolin, Cai; Xi, Li

2013-02-01

A fully integrated low-jitter, precise frequency CMOS phase-locked loop (PLL) clock for the phase change memory (PCM) drive circuit is presented. The design consists of a dynamic dual-reset phase frequency detector (PFD) with high frequency acquisition, a novel low jitter charge pump, a CMOS ring oscillator based voltage-controlled oscillator (VCO), a 2nd order passive loop filter, and a digital frequency divider. The design is fabricated in 0.35 μm CMOS technology and consumes 20 mW from a supply voltage of 5 V. In terms of the PCM's program operation requirement, the output frequency range is from 1 to 140 MHz. For the 140 MHz output frequency, the circuit features a cycle-to-cycle jitter of 28 ps RMS and 250 ps peak-to-peak.

LISA phasemeter development

NASA Astrophysics Data System (ADS)

Kullmann, Joachim; Bykov, Iouri; Heinzel, Gerhard; Danzmann, Karsten

The phasemeter is an essentiel component in the measuring chain of the spaceborne gravita-tional wave detector LISA. √ Our goal is to achieve a phasemeter sensitivity of 1 pm/ Hz below 1 Hz with respect to optical signals within a beatnote frequency range of 2 -20 MHz. To get there, several noise sources have to be eliminated. By choosing appropriate filters and adjusting loop gains digital operations of the FPGA-based phase lock loop do not limit the phasemeter sensitivity. One of the main front-end noise sources, the so called ADC time-jitter, is already successfully suppressed by correcting the signal of in-terest by means of a 48 MHz calibration tone. Noise hunting with respect to the analog front-end, currently the most demanding task, is on-going. Recent results will be presented.

The Block V Receiver fast acquisition algorithm for the Galileo S-band mission

NASA Technical Reports Server (NTRS)

Aung, M.; Hurd, W. J.; Buu, C. M.; Berner, J. B.; Stephens, S. A.; Gevargiz, J. M.

1994-01-01

A fast acquisition algorithm for the Galileo suppressed carrier, subcarrier, and data symbol signals under low data rate, signal-to-noise ratio (SNR) and high carrier phase-noise conditions has been developed. The algorithm employs a two-arm fast Fourier transform (FFT) method utilizing both the in-phase and quadrature-phase channels of the carrier. The use of both channels results in an improved SNR in the FFT acquisition, enabling the use of a shorter FFT period over which the carrier instability is expected to be less significant. The use of a two-arm FFT also enables subcarrier and symbol acquisition before carrier acquisition. With the subcarrier and symbol loops locked first, the carrier can be acquired from an even shorter FFT period. Two-arm tracking loops are employed to lock the subcarrier and symbol loops parameter modification to achieve the final (high) loop SNR in the shortest time possible. The fast acquisition algorithm is implemented in the Block V Receiver (BVR). This article describes the complete algorithm design, the extensive computer simulation work done for verification of the design and the analysis, implementation issues in the BVR, and the acquisition times of the algorithm. In the expected case of the Galileo spacecraft at Jupiter orbit insertion PD/No equals 14.6 dB-Hz, R(sym) equals 16 symbols per sec, and the predicted acquisition time of the algorithm (to attain a 0.2-dB degradation from each loop to the output symbol SNR) is 38 sec.

Flight Test Result for the Ground-Based Radio Navigation System Sensor with an Unmanned Air Vehicle

PubMed Central

Jang, Jaegyu; Ahn, Woo-Guen; Seo, Seungwoo; Lee, Jang Yong; Park, Jun-Pyo

2015-01-01

The Ground-based Radio Navigation System (GRNS) is an alternative/backup navigation system based on time synchronized pseudolites. It has been studied for some years due to the potential vulnerability issue of satellite navigation systems (e.g., GPS or Galileo). In the framework of our study, a periodic pulsed sequence was used instead of the randomized pulse sequence recommended as the RTCM (radio technical commission for maritime services) SC (special committee)-104 pseudolite signal, as a randomized pulse sequence with a long dwell time is not suitable for applications requiring high dynamics. This paper introduces a mathematical model of the post-correlation output in a navigation sensor, showing that the aliasing caused by the additional frequency term of a periodic pulsed signal leads to a false lock (i.e., Doppler frequency bias) during the signal acquisition process or in the carrier tracking loop of the navigation sensor. We suggest algorithms to resolve the frequency false lock issue in this paper, relying on the use of a multi-correlator. A flight test with an unmanned helicopter was conducted to verify the implemented navigation sensor. The results of this analysis show that there were no false locks during the flight test and that outliers stem from bad dilution of precision (DOP) or fluctuations in the received signal quality. PMID:26569251

Effect of GNSS receiver carrier phase tracking loops on earthquake monitoring performance

NASA Astrophysics Data System (ADS)

Clare, Adam; Lin, Tao; Lachapelle, Gérard

2017-06-01

This research focuses on the performance of GNSS receiver carrier phase tracking loops for early earthquake monitoring systems. An earthquake was simulated using a hardware simulator and position, velocity and acceleration displacements were obtained to recreate the dynamics of the 2011 Tohoku earthquake. Using a software defined receiver, GSNRx, tracking bandwidths of 5, 10, 15, 20, 30, 40 and 50 Hz along with integration times of 1, 5 and 10 ms were tested. Using the phase lock indicator, an adaptive tracking loop was designed and tested to maximize performance for this application.

Voltage-Controlled Oscillator

NASA Technical Reports Server (NTRS)

1995-01-01

Integrated Component Systems, Inc. incorporated information from a NASA Tech Briefs article into a voltage-controlled oscillator it designed for a customer. The company then applied the technology to its series of phase-locked loop synthesizers, which offer superior phase noise performance.

A New Interferometer for Monitoring Atmospheric Phase Fluctuations

NASA Technical Reports Server (NTRS)

Lay, Oliver

2000-01-01

Water vapor in the Earth's troposphere introduces an extra electrical path in the propagation of radio signals through the atmosphere. The distribution of water vapor is irregular and distorts the wavefronts of incoming radio waves, limiting the angular resolution that can be achieved with ground-based telescopes. The level of fluctuations depends both on the location of the site ,and on the prevailing atmospheric conditions. The ability to measure the fluctuations is therefore important when choosing a site for a new instrument, and for scheduling observations of existing telescopes. Existing phase monitors are radio interferometers that monitor monochromatic beacon tones from geostationary communications satellites at a frequency of about 12 GHz. They have a classical heterodyne design based on two satellite receiving antennas; each has a front-end for amplifying and down-converting the incoming signals using a local oscillator that is phase-locked to a common reference frequency. In addition to multiple phase-locked loops these instruments require expensive phase-stable cabling to reduce the effects of thermal drift. The new system uses two consumer 18" digital satellite TV dishes to monitor satellite TV broadcast signals over a bandwidth of 500 MHz (12.2 to 12.7 GHz). The novel design eliminates the need for phase-locked loops and thermally stable components, and uses a pair of Gilbert Cell multipliers to perform the broadband correlation. A phase monitor has been been built and deployed at the site of the Berkeley-Illinois-Maryland Association Millimeter Array in Northern California, and has been operating successfully since June 1998, measuring the difference in electrical path length for parallel lines of sight to the satellite separated by a baseline of 100 m. With a hardware cost of approximately $4000, it is much cheaper than previous instruments, and the low power requirements and high reliability make the system suitable for site testing in remote locations.

All-digital GPS receiver mechanization

NASA Astrophysics Data System (ADS)

Ould, P. C.; van Wechel, R. J.

The paper describes the all-digital baseband correlation processing of GPS signals, which is characterized by (1) a potential for improved antijamming performance, (2) fast acquisition by a digital matched filter, (3) reduction of adjustment, (4) increased system reliability, and (5) provision of a basis for the realization of a high degree of VLSI potential for the development of small economical GPS sets. The basic technical approach consists of a broadband fix-tuned RF converter followed by a digitizer; digital-matched-filter acquisition section; phase- and delay-lock tracking via baseband digital correlation; software acquisition logic and loop filter implementation; and all-digital implementation of the feedback numerical controlled oscillators and code generator. Broadband in-phase and quadrature tracking is performed by an arctangent angle detector followed by a phase-unwrapping algorithm that eliminates false locks induced by sampling and data bit transitions, and yields a wide pull-in frequency range approaching one-fourth of the loop iteration frequency.

Introduction of a new opto-electrical phase-locked loop in CMOS technology: the PMD-PLL

NASA Astrophysics Data System (ADS)

Ringbeck, Thorsten; Schwarte, Rudolf; Buxbaum, Bernd

1999-12-01

The huge and increasing need of information in the industrial world demands an enormous potential of bandwidth in telecommunication systems. Optical communication provides all participants with the whole spectrum of digital services like videophone, cable TV, video conferencing and online services. Especially fast and low cost opto-electrical receivers are badly needed in order to expand fiber networks to every home (FTTH--fiber to the home or FTTD--fiber to the desk, respectively). This paper proposes a new receiver structure which is designed to receiver optical data which are encoded by code division multiple access techniques (CDMA). For data recovery in such CDMA networks phase locked loops (PLL) are needed, which synchronize the local oscillator with the incoming clock. In optical code division multiple access networks these PLLs could be realized either with an electrical PLL after opto-electrical converting or directly in the optical path with a pure optical PLL.

FPGA implementation of self organizing map with digital phase locked loops.

PubMed

Hikawa, Hiroomi

2005-01-01

The self-organizing map (SOM) has found applicability in a wide range of application areas. Recently new SOM hardware with phase modulated pulse signal and digital phase-locked loops (DPLLs) has been proposed (Hikawa, 2005). The system uses the DPLL as a computing element since the operation of the DPLL is very similar to that of SOM's computation. The system also uses square waveform phase to hold the value of the each input vector element. This paper discuss the hardware implementation of the DPLL SOM architecture. For effective hardware implementation, some components are redesigned to reduce the circuit size. The proposed SOM architecture is described in VHDL and implemented on field programmable gate array (FPGA). Its feasibility is verified by experiments. Results show that the proposed SOM implemented on the FPGA has a good quantization capability, and its circuit size very small.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chien, Ellen Y.T.; Liu, Wei; Zhao, Qiang

Dopamine modulates movement, cognition, and emotion through activation of dopamine G protein-coupled receptors in the brain. The crystal structure of the human dopamine D3 receptor (D3R) in complex with the small molecule D2R/D3R-specific antagonist eticlopride reveals important features of the ligand binding pocket and extracellular loops. On the intracellular side of the receptor, a locked conformation of the ionic lock and two distinctly different conformations of intracellular loop 2 are observed. Docking of R-22, a D3R-selective antagonist, reveals an extracellular extension of the eticlopride binding site that comprises a second binding pocket for the aryl amide of R-22, which differsmore » between the highly homologous D2R and D3R. This difference provides direction to the design of D3R-selective agents for treating drug abuse and other neuropsychiatric indications.« less

Hopf bifurcation and chaos in a third-order phase-locked loop

NASA Astrophysics Data System (ADS)

Piqueira, José Roberto C.

2017-01-01

Phase-locked loops (PLLs) are devices able to recover time signals in several engineering applications. The literature regarding their dynamical behavior is vast, specifically considering that the process of synchronization between the input signal, coming from a remote source, and the PLL local oscillation is robust. For high-frequency applications it is usual to increase the PLL order by increasing the order of the internal filter, for guarantying good transient responses; however local parameter variations imply structural instability, thus provoking a Hopf bifurcation and a route to chaos for the phase error. Here, one usual architecture for a third-order PLL is studied and a range of permitted parameters is derived, providing a rule of thumb for designers. Out of this range, a Hopf bifurcation appears and, by increasing parameters, the periodic solution originated by the Hopf bifurcation degenerates into a chaotic attractor, therefore, preventing synchronization.

Pulsed phase locked loop strain monitor

NASA Technical Reports Server (NTRS)

Froggatt, Mark E. (Inventor)

1995-01-01

A pulse phase locked loop system according to the present invention is described. A frequency generator such as a voltage controlled oscillator (VCO) generates an output signal and a reference signal having a frequency equal to that of the output signal. A transmitting gate gates the output frequency signal and this gated signal drives a transmitting transducer which transmits an acoustic wave through a material. A sample/hold samples a signal indicative of the transmitted wave which is received by a receiving transducer. Divide-by-n counters control these gating and sampling functions in response to the reference signal of the frequency generator. Specifically, the output signal is gated at a rate of F/h, wherein F is the frequency of the output signal and h is an integer; and the received signal is sampled at a delay of F/n wherein n is an integer.

Injection Locking Techniques for Spectrum Analysis

NASA Astrophysics Data System (ADS)

Gathma, Timothy D.; Buckwalter, James F.

2011-04-01

Wideband spectrum analysis supports future communication systems that reconfigure and adapt to the capacity of the spectral environment. While test equipment manufacturers offer wideband spectrum analyzers with excellent sensitivity and resolution, these spectrum analyzers typically cannot offer acceptable size, weight, and power (SWAP). CMOS integrated circuits offer the potential to fully integrate spectrum analysis capability with analog front-end circuitry and digital signal processing on a single chip. Unfortunately, CMOS lacks high-Q passives and wideband resonator tunability that is necessary for heterodyne implementations of spectrum analyzers. As an alternative to the heterodyne receiver architectures, two nonlinear methods for performing wideband, low-power spectrum analysis are presented. The first method involves injecting the spectrum of interest into an array of injection-locked oscillators. The second method employs the closed loop dynamics of both injection locking and phase locking to independently estimate the injected frequency and power.

Fully stabilized mid-infrared frequency comb for high-precision molecular spectroscopy.

PubMed

Vainio, Markku; Karhu, Juho

2017-02-20

A fully stabilized mid-infrared optical frequency comb spanning from 2.9 to 3.4 µm is described in this article. The comb is based on half-harmonic generation in a femtosecond optical parametric oscillator, which transfers the high phase coherence of a fully stabilized near-infrared Er-doped fiber laser comb to the mid-infrared region. The method is simple, as no phase-locked loops or reference lasers are needed. Precise locking of optical frequencies of the mid-infrared comb to the pump comb is experimentally verified at sub-20 mHz level, which corresponds to a fractional statistical uncertainty of 2 × 10^-16 at the center frequency of the mid-infrared comb. The fully stabilized mid-infrared comb is an ideal tool for high-precision molecular spectroscopy, as well as for optical frequency metrology in the mid-infrared region, which is difficult to access with other stabilized frequency comb techniques.

SEU/SET Tolerant Phase-Locked Loops

NASA Technical Reports Server (NTRS)

Shuler, Robert L., Jr.

2010-01-01

The phase-locked loop (PLL) is an old and widely used circuit for frequency and phase demodulation, carrier and clock recovery, and frequency synthesis [1]. Its implementations range from discrete components to fully integrated circuits and even to firmware or software. Often the PLL is a highly critical component of a system, as for example when it is used to derive the on-chip clock, but as of this writing no definitive single-event upset (SET)/single-event transient (SET) tolerant PLL circuit has been described. This chapter hopes to rectify that situation, at least in regard to PLLs that are used to generate clocks. Older literature on fault-tolerant PLLs deals with detection of a hard failure, which is recovered by replacement, repair, or manual restart of discrete component systems. Several patents exist along these lines (6349391, 6272647, and 7089442). A newer approach is to harden the parts of a PLL system, to one degree or another, such as by using a voltage-based charge pump or a triple modular redundant (TMR) voted voltage-controlled oscillator (VCO). A more comprehensive approach is to harden by triplication and voting (TMR) all the digital pieces (primarily the divider) of a frequency synthesis PLL, but this still leaves room for errors in the VCO and the loop filter. Instead of hardening or voting pieces of a system, such as a frequency synthesis system (i.e., clock multiplier), we will show how the entire system can be voted. There are two main ways of doing this, each with advantages and drawbacks. We will show how each has advantages in certain areas, depending on the lock acquisition and tracking characteristics of the PLL. Because of this dependency on PLL characteristics, we will briefly revisit the theory of PLLs. But first we will describe the characteristics of voters and their correct application, as some literature does not follow the voting procedure that guarantees elimination of errors. Additionally, we will find that voting clocks is a bit trickier than voting data where an infallible clock is assumed. It is our job here to produce (or recover) that assumed infallible clock!

Radio-Frequency and Wideband Modulation Arraying

NASA Technical Reports Server (NTRS)

Brockman, M. H.

1984-01-01

Summing network receives coherent signals from all receivers in array. Method sums narrow-band radio-frequency (RF) carrier powers and wide-band spectrum powers of array of separate antenna/receiver systems designed for phase-locked-loop or suppressed-carrier operation.

CUA Annual Meeting Abstracts addition.

PubMed

2012-08-01

: Foley catheters are assumed to drain the bladder to completion. We have previously shown that dependent loops along the drainage tubing create air-locks, which obstruct antegrade urine flow and result in un-drained residual bladder urine. We hypothesized that drainage characteristics of Foley catheters remain poorly understood by urologists and general surgeons. We conducted a nationwide survey of general surgery and urology training program faculty and residents, to assess perceptions of Foley catheter drainage. We designed a novel catheter drainage tube/bag that eliminates air-locks. : An anonymous illustrated questionnaire assessing Foley catheter use patterns and perception was sent to general surgery and urology residency programs (N=108) nationwide. A modified catheter drainage tube/bag unit was designed and tested. An ex vivo catheterized bladder model was designed to measure and compare urine drainage rates with the standard drainage system, versus with our novel design. : A total of 307 responses were collected from residents (55%) and faculty (45%); responses were similar among both groups (p<0.05). The majority reported that at their centers Foley catheter drainage tubes are generally positioned with a dependent loop (94.1%), and, that positioning with a dependent loop, versus without (78.1%) promoted optimal drainage. Antegrade drainage does not occur with a traditional drainage system when a >5.5 inch dependent loop in place. With our proposed design, which eliminates dependent loops, the bladder model emptied to completion consistently. : Traditional Foley catheter drainage systems, as commonly used, evacuate the bladder sub- optimally. More reliable and complete bladder drainage may decrease the incidence of catheter related UTI. The novel modified Foley catheter drainage tube/bag design presented here eliminates dependent loops, to optimize antegrade drainage.

Autopilot for frequency-modulation atomic force microscopy.

PubMed

Kuchuk, Kfir; Schlesinger, Itai; Sivan, Uri

2015-10-01

One of the most challenging aspects of operating an atomic force microscope (AFM) is finding optimal feedback parameters. This statement applies particularly to frequency-modulation AFM (FM-AFM), which utilizes three feedback loops to control the cantilever excitation amplitude, cantilever excitation frequency, and z-piezo extension. These loops are regulated by a set of feedback parameters, tuned by the user to optimize stability, sensitivity, and noise in the imaging process. Optimization of these parameters is difficult due to the coupling between the frequency and z-piezo feedback loops by the non-linear tip-sample interaction. Four proportional-integral (PI) parameters and two lock-in parameters regulating these loops require simultaneous optimization in the presence of a varying unknown tip-sample coupling. Presently, this optimization is done manually in a tedious process of trial and error. Here, we report on the development and implementation of an algorithm that computes the control parameters automatically. The algorithm reads the unperturbed cantilever resonance frequency, its quality factor, and the z-piezo driving signal power spectral density. It analyzes the poles and zeros of the total closed loop transfer function, extracts the unknown tip-sample transfer function, and finds four PI parameters and two lock-in parameters for the frequency and z-piezo control loops that optimize the bandwidth and step response of the total system. Implementation of the algorithm in a home-built AFM shows that the calculated parameters are consistently excellent and rarely require further tweaking by the user. The new algorithm saves the precious time of experienced users, facilitates utilization of FM-AFM by casual users, and removes the main hurdle on the way to fully automated FM-AFM.

Autopilot for frequency-modulation atomic force microscopy

NASA Astrophysics Data System (ADS)

Kuchuk, Kfir; Schlesinger, Itai; Sivan, Uri

2015-10-01

One of the most challenging aspects of operating an atomic force microscope (AFM) is finding optimal feedback parameters. This statement applies particularly to frequency-modulation AFM (FM-AFM), which utilizes three feedback loops to control the cantilever excitation amplitude, cantilever excitation frequency, and z-piezo extension. These loops are regulated by a set of feedback parameters, tuned by the user to optimize stability, sensitivity, and noise in the imaging process. Optimization of these parameters is difficult due to the coupling between the frequency and z-piezo feedback loops by the non-linear tip-sample interaction. Four proportional-integral (PI) parameters and two lock-in parameters regulating these loops require simultaneous optimization in the presence of a varying unknown tip-sample coupling. Presently, this optimization is done manually in a tedious process of trial and error. Here, we report on the development and implementation of an algorithm that computes the control parameters automatically. The algorithm reads the unperturbed cantilever resonance frequency, its quality factor, and the z-piezo driving signal power spectral density. It analyzes the poles and zeros of the total closed loop transfer function, extracts the unknown tip-sample transfer function, and finds four PI parameters and two lock-in parameters for the frequency and z-piezo control loops that optimize the bandwidth and step response of the total system. Implementation of the algorithm in a home-built AFM shows that the calculated parameters are consistently excellent and rarely require further tweaking by the user. The new algorithm saves the precious time of experienced users, facilitates utilization of FM-AFM by casual users, and removes the main hurdle on the way to fully automated FM-AFM.

Modeling gene regulatory network motifs using statecharts

PubMed Central

2012-01-01

Background Gene regulatory networks are widely used by biologists to describe the interactions among genes, proteins and other components at the intra-cellular level. Recently, a great effort has been devoted to give gene regulatory networks a formal semantics based on existing computational frameworks. For this purpose, we consider Statecharts, which are a modular, hierarchical and executable formal model widely used to represent software systems. We use Statecharts for modeling small and recurring patterns of interactions in gene regulatory networks, called motifs. Results We present an improved method for modeling gene regulatory network motifs using Statecharts and we describe the successful modeling of several motifs, including those which could not be modeled or whose models could not be distinguished using the method of a previous proposal. We model motifs in an easy and intuitive way by taking advantage of the visual features of Statecharts. Our modeling approach is able to simulate some interesting temporal properties of gene regulatory network motifs: the delay in the activation and the deactivation of the "output" gene in the coherent type-1 feedforward loop, the pulse in the incoherent type-1 feedforward loop, the bistability nature of double positive and double negative feedback loops, the oscillatory behavior of the negative feedback loop, and the "lock-in" effect of positive autoregulation. Conclusions We present a Statecharts-based approach for the modeling of gene regulatory network motifs in biological systems. The basic motifs used to build more complex networks (that is, simple regulation, reciprocal regulation, feedback loop, feedforward loop, and autoregulation) can be faithfully described and their temporal dynamics can be analyzed. PMID:22536967

Steady-state probability density function of the phase error for a DPLL with an integrate-and-dump device

NASA Technical Reports Server (NTRS)

Simon, M.; Mileant, A.

1986-01-01

The steady-state behavior of a particular type of digital phase-locked loop (DPLL) with an integrate-and-dump circuit following the phase detector is characterized in terms of the probability density function (pdf) of the phase error in the loop. Although the loop is entirely digital from an implementation standpoint, it operates at two extremely different sampling rates. In particular, the combination of a phase detector and an integrate-and-dump circuit operates at a very high rate whereas the loop update rate is very slow by comparison. Because of this dichotomy, the loop can be analyzed by hybrid analog/digital (s/z domain) techniques. The loop is modeled in such a general fashion that previous analyses of the Real-Time Combiner (RTC), Subcarrier Demodulator Assembly (SDA), and Symbol Synchronization Assembly (SSA) fall out as special cases.

Timing performance of phase-locked loops in optical pulse position modulation communication systems

NASA Astrophysics Data System (ADS)

Lafaw, D. A.

In an optical digital communication system, an accurate clock signal must be available at the receiver to provide proper synchronization with the transmitted signal. Phase synchronization is especially critical in M-ary pulse position modulation (PPM) systems where the optimum decision scheme is an energy detector which compares the energy in each of M time slots to decide which of M possible words was sent. A timing error causes energy spillover into adjacent time slots (a form of intersymbol interference) so that only a portion of the signal energy may be attributed to the correct time slot. This effect decreases the effective signal, increases the effective noise, and increases the probability of error. This report simulates a timing subsystem for a satellite-to-satellite optical PPM communication link. The receiver employs direct photodetection, preprocessing of the optical signal, and a phase-locked loop for timing synchronization. The photodetector output is modeled as a filtered, doubly stochastic Poisson shot noise process. The variance of the relative phase error is examined under varying signal strength conditions as an indication of loop performance, and simulation results are compared to theoretical relations.

Designing neuro-fuzzy controller for electromagnetic anti-lock braking system (ABS) on electric vehicle

NASA Astrophysics Data System (ADS)

Pramudijanto, Josaphat; Ashfahani, Andri; Lukito, Rian

2018-03-01

Anti-lock braking system (ABS) is used on vehicles to keep the wheels unlocked in sudden break (inside braking) and minimalize the stop distance of the vehicle. The problem of it when sudden break is the wheels locked so the vehicle steering couldn’t be controlled. The designed ABS system will be applied on ABS simulator using the electromagnetic braking. In normal condition or in condition without braking, longitudinal velocity of the vehicle will be equal with the velocity of wheel rotation, so the slip ratio will be 0 (0%) and if the velocity of wheel rotation is 0 (in locked condition) then the wheels will be slip 1 (100%). ABS system will keep the value of slip ratio so it will be 0.2 (20%). In this final assignment, the method that is used is Neuro-Fuzzy method to control the slip value on the wheels. The input is the expectable slip and the output is slip from plant. The learning algorithm which is used is Backpropagation that will work by feedforward to get actual output and work by feedback to get error value with target output. The network that was made based on fuzzy mechanism which are fuzzification, inference and defuzzification, Neuro-fuzzy controller can reduce overshoot plant respond to 43.2% compared to plant respond without controller by open loop.

Frequency stabilization of an Er-doped fiber laser with a collinear 2f-to-3f self-referencing interferometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hitachi, K., E-mail: hitachi.kenichi@lab.ntt.co.jp; Ishizawa, A.; Mashiko, H.

2015-06-08

We report the stabilization of the carrier-envelope offset (CEO) frequency of an Er-doped fiber laser with a collinear 2f-to-3f self-referencing interferometer. The interferometer is implemented by a dual-pitch periodically poled lithium niobate ridge waveguide with two different quasi-phase matching pitch sizes. We obtain a 52-dB signal-to-noise ratio in the 100-kHz resolution bandwidth of a heterodyne beat signal, which is sufficient for frequency stabilization. We also demonstrate that the collinear geometry is robust against environmental perturbation by comparing in-loop and out-of-loop Allan deviations when the in-loop CEO frequency is stabilized with a phase-locked loop circuit.

Passively mode-locked tunable fiber laser in a soliton regime

NASA Astrophysics Data System (ADS)

Endo, Michiyuki; Ghosh, Gorachand

1999-04-01

A stable, passively mode-locked erbium-doped fiber resonator is developed to generate tunable optical pulses with durations of 270 - 325 fs in the soliton regime. The lasing wavelength is tuned continuously over a wavelength range of 60 nm by rotating a bulk band-pass filter inserted in the resonator with a repetition frequency of 45.4 MHz. We reduced the timing jitter by minimizing the intensity fluctuation of the pump source using a feedback loop and by controlling the influence of airflow and temperature fluctuation of the resonator in a sealed box.

Remote distribution of a mode-locked pulse train with sub 40-as jitter

NASA Astrophysics Data System (ADS)

Chen, Yi-Fei; Jiang, Jie; Jones, David J.

2006-12-01

Remote transfer of an ultralow-jitter microwave frequency reference signal is demonstrated using the pulse trains generated by a mode-locked fiber laser. The timing jitter in a ~ 30-m fiber link is reduced to 38 attoseconds (as) integrated over a bandwidth from 1 Hz to 10 MHz via active stabilization which represents a significant improvement over previously reported jitter performance. Our approach uses an all-optical generation of the synchronization error signal and an accompanying out-of-loop optical detection technique to verify the jitter performance.

Frequency-tunable Pre-stabilized Lasers for LISA via Sideband-locking

NASA Technical Reports Server (NTRS)

Livas, Jeffrey C.; Thorpe, James I.; Numata, Kenji; Mitryk, Shawn; Mueller, Guido; Wand, Vinzenz

2008-01-01

Laser frequency noise mitigation is one of the most challenging aspects of the LISA interferometric measurement system. The unstabilized frequency fluctuations must be suppressed by roughly twelve orders of magnitude in order to achieve stability sufficient for gravitational wave detection. This enormous suppression will be achieved through a combination of stabilization and common-mode rejection. The stabilization component will itself be achieved in two stages: pre-stabilization to a local optical cavity followed by arm-locking to some combination of the inter-spacecraft distances. In order for these two stabilization stages to work simultaneously, the lock-point of the pre-stabilization loop must be frequency tunable. The current baseline stabilization technique, locking to an optical cavity, does not provide tunability between cavity resonances, which are typically spaced by 100s of MHz. Here we present a modification to the traditional Pound-Drever-Hall cavity locking technique that allows the laser to be locked to a cavity resonance with an adjustable frequency offset. This technique requires no modifications to the optical cavity itself, thus preserving the stability of the frequency reference. We present measurements of the system performance and demonstrate that we can meet implement the first two stages of stabilization.

New kind of injection-locked oscillator and its corresponding long-term stability control.

PubMed

Hong, Jun; Liu, An; Wang, Xiao-hu; Yao, Sheng-xing; Li, Zu-ling

2015-09-20

A new type of opto-electronic hybrid oscillator is proposed for the first time, to the best of our knowledge, and verified by experiments in this paper. Typical electronic oscillator-dielectric resonator oscillator as the first injection source is used to injection lock the first long-fiber loop-based opto-electronic oscillator (OEO); then its output is used to injection lock the second long-fiber opto-electronic oscillator. Using this method, low-phase noise output signal can be obtained. Experiments show that single side-band (SSB) phase noise of a 9.5 GHz oscillation signal at 10 kHz offset frequency decreases from -123 to -135  dBc/Hz after the first injection, then, through the second injection, the SSB phase noise drops down to -146  dBc/Hz. In order to solve the long-term stability problem of the above oscillator, a new stability-control circuit also is designed and verified by experiments. Experiments show that the Allan deviation decreases from 9.0×10(-11) to 2.2×10(-12) during 1 s after the long-term stability-control circuit being used.

Novel multireceiver communication systems configurations based on optimal estimation theory

NASA Technical Reports Server (NTRS)

Kumar, Rajendra

1992-01-01

A novel multireceiver configuration for carrier arraying and/or signal arraying is presented. The proposed configuration is obtained by formulating the carrier and/or signal arraying problem as an optimal estimation problem, and it consists of two stages. The first stage optimally estimates various phase processes received at different receivers with coupled phase-locked loops wherein the individual loops acquire and track their respective receivers' phase processes but are aided by each other in an optimal manner via LF error signals. The proposed configuration results in the minimization of the the effective radio loss at the combiner output, and thus maximization of energy per bit to noise power spectral density ratio is achieved. A novel adaptive algorithm for the estimator of the signal model parameters when these are not known a priori is also presented.

Design of c-band telecontrol transmitter local oscillator for UAV data link

NASA Astrophysics Data System (ADS)

Cao, Hui; Qu, Yu; Song, Zuxun

2018-01-01

A C-band local oscillator of an Unmanned Aerial Vehicle (UAV) data link radio frequency (RF) transmitter unit with high-stability, high-precision and lightweight was designed in this paper. Based on the highly integrated broadband phase-locked loop (PLL) chip HMC834LP6GE, the system performed fractional-N control by internal modules programming to achieve low phase noise and small frequency resolution. The simulation and testing methods were combined to optimize and select the loop filter parameters to ensure the high precision and stability of the frequency synthesis output. The theoretical analysis and engineering prototype measurement results showed that the local oscillator had stable output frequency, accurate frequency step, high spurious suppression and low phase noise, and met the design requirements. The proposed design idea and research method have theoretical guiding significance for engineering practice.

A fuzzy control design case: The fuzzy PLL

NASA Technical Reports Server (NTRS)

Teodorescu, H. N.; Bogdan, I.

1992-01-01

The aim of this paper is to present a typical fuzzy control design case. The analyzed controlled systems are the phase-locked loops (PLL's)--classic systems realized in both analogic and digital technology. The crisp PLL devices are well known.

Quadrature demultiplexing using a degenerate vector parametric amplifier.

PubMed

Lorences-Riesgo, Abel; Liu, Lan; Olsson, Samuel L I; Malik, Rohit; Kumpera, Aleš; Lundström, Carl; Radic, Stojan; Karlsson, Magnus; Andrekson, Peter A

2014-12-01

We report on quadrature demultiplexing of a quadrature phase-shift keying (QPSK) signal into two cross-polarized binary phase-shift keying (BPSK) signals with negligible penalty at bit-error rate (BER) equal to 10(-9). The all-optical quadrature demultiplexing is achieved using a degenerate vector parametric amplifier operating in phase-insensitive mode. We also propose and demonstrate the use of a novel and simple phase-locked loop (PLL) scheme based on detecting the envelope of one of the signals after demultiplexing in order to achieve stable quadrature decomposition.

Cyclic biomechanical testing of biocomposite lateral row knotless anchors in a human cadaveric model.

PubMed

Barber, F Alan; Bava, Eric D; Spenciner, David B; Piccirillo, Justin

2013-06-01

The purpose of this study was to assess the mechanical performance of biocomposite knotless lateral row anchors based on both anchor design and the direction of pull. Two lateral row greater tuberosity insertion sites (anterior and posterior) were identified in matched pairs of fresh-frozen human cadaveric shoulders DEXA (dual energy X-ray absorptiometry) scanned to verify comparability. The humeri were stripped of all soft tissue and 3 different biocomposite knotless lateral row anchors: HEALIX Knotless BR (DePuy Mitek, Raynham MA), BioComposite PushLock (Arthrex, Naples, FL), and Bio-SwiveLock (Arthrex). Fifty-two anchors were distributed among the insertion locations and tested them with either an anatomic or axial pull. A fixed-gauge loop (15 mm) of 2 high-strength sutures from each anchor was created. After a 10-Nm preload, anchors were cycled from 10 to 45 Nm at 0.5 Hz for 200 cycles and tested to failure at 4.23 mm/second. The load to reach 3 mm and 5 mm displacement, ultimate failure load, displacement at ultimate failure, and failure mode were recorded. Threaded anchors (Bio-SwiveLock, P = .03; HEALIX Knotless, P = .014) showed less displacement with anatomic testing than did the nonthreaded anchor (BioComposite PushLock), and the HEALIX Knotless showed less overall displacement than did the other 2 anchors. The Bio-SwiveLock exhibited greater failure loads than did the other 2 anchors (P < .05). Comparison of axial and anatomic loading showed no maximum load differences for all anchors as a whole (P = .1084). Yet, anatomic pulling produced higher failure loads than did axial pulling for the Bio-SwiveLock but not for the BioComposite PushLock or the HEALIX Knotless. The nonthreaded anchor (BioComposite PushLock) displayed lower failure loads than did both threaded anchors with axial pulling. Threaded biocomposite anchors (HEALIX Knotless BR and Bio-SwiveLock) show less anatomic loading displacement and higher axial failure loads than do the nonthreaded (BioComposite PushLock) anchor. The HEALIX Knotless BR anchor showed less displacement than did the BioComposite PushLock and Bio-SwiveLock anchors. Neither axial nor anatomic loading had an effect on overall anchor displacement. Because of the strength profiles exhibited, this study supports the use of biocomposite anchors, which have definite advantages over polyetheretherketone (PEEK) and metal products. However, the nonthreaded BioComposite PushLock anchor cannot be recommended. Copyright © 2013 Arthroscopy Association of North America. All rights reserved.

Locking the Active Conformation of c-Src Kinase through the Phosphorylation of the Activation Loop

PubMed Central

Meng, Yilin; Roux, Benoît

2013-01-01

Molecular dynamics umbrella sampling simulations are used to compare the relative stability of the active conformation of the catalytic domain of c-Src kinase while the tyrosine 416 in the activation loop (A-loop) is either unphosphorylated or phosphorylated. When the A-loop is unphosphorylated, there is considerable flexiblity of the kinase. While the active conformation of the kinase is not forbidden and can be visited transiently, it is not the predominant state. This is consistent with the view that c-Src displays some catalytic activity even when the A-loop is unphosphorylated. In contrast, phosphorylation of the A-loop contributes to stabilize several structural features that are critical for catalysis, such as the hydrophobic regulatory spine, the HRD motif, and the electrostatic switch. In summary, the free energy landscape calculations demonstrate that phosphorylation of tyrosine 416 in the A-loop essentially “locks” the kinase into its catalytically competent conformation. PMID:24103328

Low noise erbium fiber fs frequency comb based on a tapered-fiber carbon nanotube design.

PubMed

Wu, Tsung-Han; Kieu, K; Peyghambarian, N; Jones, R J

2011-03-14

We report on a low noise all-fiber erbium fs frequency comb based on a simple and robust tapered-fiber carbon nanotube (tf-CNT) design. We mitigate dominant noise sources to show that the free-running linewidth of the carrier-envelope offset frequency (fceo) can be comparable to the best reported performance to date for fiber-based frequency combs. A free-running fceo linewidth of ~20 kHz is demonstrated, corresponding to an improvement of ~30 times over previous work based on a CNT mode-locked fiber laser [Opt. Express 18, 1667 (2010)]. We also demonstrate the use of an acousto-optic modulator external to the laser cavity to stabilize fceo, enabling a 300 kHz feedback control bandwidth. The offset frequency is phase-locked with an in-loop integrated phase noise of ~0.8 rad from 10Hz to 400kHz. We show a resolution-limited linewidth of ~1 Hz, demonstrating over 90% of the carrier power within the coherent fceo signal. The results demonstrate that the relatively simple tf-CNT fiber laser design can provide a compact, robust and high-performance fs frequency comb.

Spectral estimation of received phase in the presence of amplitude scintillation

NASA Technical Reports Server (NTRS)

Vilnrotter, V. A.; Brown, D. H.; Hurd, W. J.

1988-01-01

A technique is demonstrated for obtaining the spectral parameters of the received carrier phase in the presence of carrier amplitude scintillation, by means of a digital phased locked loop. Since the random amplitude fluctuations generate time-varying loop characteristics, straightforward processing of the phase detector output does not provide accurate results. The method developed here performs a time-varying inverse filtering operation on the corrupted observables, thus recovering the original phase process and enabling accurate estimation of its underlying parameters.

The use of interleaving for reducing radio loss in trellis-coded modulation systems

NASA Technical Reports Server (NTRS)

Divsalar, D.; Simon, M. K.

1989-01-01

It is demonstrated how the use of interleaving/deinterleaving in trellis-coded modulation (TCM) systems can reduce the signal-to-noise ratio loss due to imperfect carrier demodulation references. Both the discrete carrier (phase-locked loop) and suppressed carrier (Costas loop) cases are considered and the differences between the two are clearly demonstrated by numerical results. These results are of great importance for future communication links to the Deep Space Network (DSN), especially from high Earth orbiters, which may be bandwidth limited.

Robust GPS carrier tracking under ionospheric scintillation

NASA Astrophysics Data System (ADS)

Susi, M.; Andreotti, M.; Aquino, M. H.; Dodson, A.

2013-12-01

Small scale irregularities present in the ionosphere can induce fast and unpredictable fluctuations of Radio Frequency (RF) signal phase and amplitude. This phenomenon, known as scintillation, can degrade the performance of a GPS receiver leading to cycle slips, increasing the tracking error and also producing a complete loss of lock. In the most severe scenarios, if the tracking of multiple satellites links is prevented, outages in the GPS service can also occur. In order to render a GPS receiver more robust under scintillation, particular attention should be dedicated to the design of the carrier tracking stage, that is the receiver's part most sensitive to these types of phenomenon. This paper exploits the reconfigurability and flexibility of a GPS software receiver to develop a tracking algorithm that is more robust under ionospheric scintillation. For this purpose, first of all, the scintillation level is monitored in real time. Indeed the carrier phase and the post correlation terms obtained by the PLL (Phase Locked Loop) are used to estimate phi60 and S4 [1], the scintillation indices traditionally used to quantify the level of phase and amplitude scintillations, as well as p and T, the spectral parameters of the fluctuations PSD. The effectiveness of the scintillation parameter computation is confirmed by comparing the values obtained by the software receiver and the ones provided by a commercial scintillation monitoring, i.e. the Septentrio PolarxS receiver [2]. Then the above scintillation parameters and the signal carrier to noise density are exploited to tune the carrier tracking algorithm. In case of very weak signals the FLL (Frequency Locked Loop) scheme is selected in order to maintain the signal lock. Otherwise an adaptive bandwidth Phase Locked Loop (PLL) scheme is adopted. The optimum bandwidth for the specific scintillation scenario is evaluated in real time by exploiting the Conker formula [1] for the tracking jitter estimation. The performance of the proposed tracking scheme is assessed by using both simulated and real data. Real data have been collected in Vietnam by using a USRP (Universal Software Radio Peripheral) N210 front end connected to a rubidium oscillator. Selected events are exploited in order to challenge the algorithm with strong phase and amplitude variations. Moreover, simulated data have been collected by using the prototype of a digital front end developed by Novatel, namely the 'Firehose'. Since the latter includes a TCXO oscillator, the proposed tracking scheme is also opportunely modified to take in account the clock error contribution. References 1. R.S., Conker, M. B. El-Arini, C. J. Hegarty, and T. Hsiao, Modelling the effects of ionospheric scintillation on GPS/satellite-based augmentation system availability. Radio Sci., 38, 1, 1001, doi: 10.1029/2000RS002604, 2003. 2. B. Bougard et al, 'CIGALA: Challenging the Solar Maximum in Brazil with PolaRxS,' ION GNSS, Portland, Sept. 2011.

Illumination-based synchronization of high-speed vision sensors.

PubMed

Hou, Lei; Kagami, Shingo; Hashimoto, Koichi

2010-01-01

To acquire images of dynamic scenes from multiple points of view simultaneously, the acquisition time of vision sensors should be synchronized. This paper describes an illumination-based synchronization method derived from the phase-locked loop (PLL) algorithm. Incident light to a vision sensor from an intensity-modulated illumination source serves as the reference signal for synchronization. Analog and digital computation within the vision sensor forms a PLL to regulate the output signal, which corresponds to the vision frame timing, to be synchronized with the reference. Simulated and experimental results show that a 1,000 Hz frame rate vision sensor was successfully synchronized with 32 μs jitters.

Gigahertz frequency comb from a diode-pumped solid-state laser.

PubMed

Klenner, Alexander; Schilt, Stéphane; Südmeyer, Thomas; Keller, Ursula

2014-12-15

We present the first stabilization of the frequency comb offset from a diode-pumped gigahertz solid-state laser oscillator. No additional external amplification and/or compression of the output pulses is required. The laser is reliably modelocked using a SESAM and is based on a diode-pumped Yb:CALGO gain crystal. It generates 1.7-W average output power and pulse durations as short as 64 fs at a pulse repetition rate of 1 GHz. We generate an octave-spanning supercontinuum in a highly nonlinear fiber and use the standard f-to-2f carrier-envelope offset (CEO) frequency f_CEO detection method. As a pump source, we use a reliable and cost-efficient commercial diode laser. Its multi-spatial-mode beam profile leads to a relatively broad frequency comb offset beat signal, which nevertheless can be phase-locked by feedback to its current. Using improved electronics, we reached a feedback-loop-bandwidth of up to 300 kHz. A combination of digital and analog electronics is used to achieve a tight phase-lock of f_CEO to an external microwave reference with a low in-loop residual integrated phase-noise of 744 mrad in an integration bandwidth of [1 Hz, 5 MHz]. An analysis of the laser noise and response functions is presented which gives detailed insights into the CEO stabilization of this frequency comb.

Wideband digital frequency detector with subtraction-based phase comparator for frequency modulation atomic force microscopy.

PubMed

Mitani, Yuji; Kubo, Mamoru; Muramoto, Ken-ichiro; Fukuma, Takeshi

2009-08-01

We have developed a wideband digital frequency detector for high-speed frequency modulation atomic force microscopy (FM-AFM). We used a subtraction-based phase comparator (PC) in a phase-locked loop circuit instead of a commonly used multiplication-based PC, which has enhanced the detection bandwidth to 100 kHz. The quantitative analysis of the noise performance revealed that the internal noise from the developed detector is small enough to provide the theoretically limited noise performance in FM-AFM experiments in liquid. FM-AFM imaging of mica in liquid was performed with the developed detector, showing its stability and applicability to true atomic-resolution imaging in liquid.

Phase-locked loop with controlled phase slippage

DOEpatents

Mestha, Lingappa K.

1994-01-01

A system for synchronizing a first subsystem controlled by a changing frequency sweeping from a first frequency to a second frequency, with a second subsystem operating at a steady state second frequency. Trip plan parameters are calculated in advance to determine the phase relationship between the frequencies of the first subsystem and second subsystem in order to obtain synchronism at the end of the frequency sweep of the first subsystem. During the time in which the frequency of the first subsystem is sweeping from the first frequency to the second frequency, the phase locked system compares the actual phase difference with the trip plan phase difference and incrementally changes the sweep frequency in a manner so that phase lock is achieved when the first subsystem reaches a frequency substantially identical to that of the second subsystem.

High-pulse energy-stabilized passively mode-locked external cavity inverse bow-tie 980nm laser diode for space applications

NASA Astrophysics Data System (ADS)

Krakowski, M.; Resneau, P.; Garcia, M.; Vinet, E.; Robert, Y.; Lecomte, M.; Parillaud, O.; Gerard, B.; Kundermann, S.; Torcheboeuf, N.; Boiko, D. L.

2018-02-01

We report on multi-section inverse bow-tie laser producing mode-locked pulses of 90 pJ energy and 6.5 ps width (895 fs after compression) at 1.3 GHz pulse repetition frequency (PRF) and consuming 2.9 W of electric power. The laser operates in an 80 mm long external cavity. By translation of the output coupling mirror, the PRF was continuously tuned over 37 MHz range without additional adjustments. Active stabilization with a phase lock loop actuating on the driving current has allowed us to reach the PRF relative stability at a 2·10-10 level on 10 s intervals, as required by the European Space Agency (ESA) for inter-satellite long distance measurements.

Investigation of homodyne demodulation of RZ-BPSK signal based on an optical Costas loop

NASA Astrophysics Data System (ADS)

Zhou, Haijun; Zhu, Zunzhen; Xie, Weilin; Dong, Yi

2018-01-01

We demonstrate the coherent detection of 10 Gb/s return-to-zero (RZ) binary phase-shift keying (BPSK) signal based on a homodyne Costas optical phase-locked loop (OPLL). It demonstrates time misalignment tolerance of +/- 10% of the transmitted RZ-BPSK signal, i.e. -20 to +20 ps between the pulse carver and the phase modulator for 5 Gb/s RZ-BPSK signal, -10 to +10 ps or 10 Gb/s RZ-BPSK signal. Besides, the Costas coherent receiver shows a 2.5 dB sensitivity improvement over conventional 5 Gb/s NRZ-BPSK and a 1.4 dB over 10 Gb/s NRZ-BPSK only at the cost of slightly higher residual phase error. Those merits of sufficient tolerance to misalignment, higher receiver sensitivity, and low residual phase error of RZ-BPSK modulation are beneficial to be applied in free space optical (FSO) communication to achieve higher link budget, longer transmission distance.

Coherent beam combining of collimated fiber array based on target-in-the-loop technique

NASA Astrophysics Data System (ADS)

Li, Xinyang; Geng, Chao; Zhang, Xiaojun; Rao, Changhui

2011-11-01

Coherent beam combining (CBC) of fiber array is a promising way to generate high power and high quality laser beams. Target-in-the-loop (TIL) technique might be an effective way to ensure atmosphere propagation compensation without wavefront sensors. In this paper, we present very recent research work about CBC of collimated fiber array using TIL technique at the Key Lab on Adaptive Optics (KLAO), CAS. A novel Adaptive Fiber Optics Collimator (AFOC) composed of phase-locking module and tip/tilt control module was developed. CBC experimental setup of three-element fiber array was established. Feedback control is realized using stochastic parallel gradient descent (SPGD) algorithm. The CBC based on TIL with piston and tip/tilt correction simultaneously is demonstrated. And the beam pointing to locate or sweep position of combined spot on target was achieved through TIL technique too. The goal of our work is achieve multi-element CBC for long-distance transmission in atmosphere.

A 0.8-4.2 GHz monolithic all-digital PLL based frequency synthesizer for wireless communications

NASA Astrophysics Data System (ADS)

Yuanxin, Zhao; Yuanpei, Gao; Wei, Li; Ning, Li; Junyan, Ren

2015-01-01

A 0.8-4.2 GHz monolithic all-digital PLL based frequency synthesizer for wireless communications is successfully realized by the 130 nm CMOS process. A series of novel methods are proposed in this paper. Two band DCOs with high frequency resolution are utilized to cover the frequency band of interest, which is as wide as 2.5 to 5 GHz. An overflow counter is proposed to prevent the “pulse-swallowing” phenomenon so as to significantly reduce the locking time. A NTW-clamp digital module is also proposed to prevent the overflow of the loop control word. A modified programmable divider is presented to prevent the failure operation at the boundary. The measurement results show that the output frequency range of this frequency synthesizer is 0.8-4.2 GHz. The locking time achieves a reduction of 84% at 2.68 GHz. The best in-band and out-band phase noise performances have reached -100 dBc/Hz, and -125 dBc/Hz respectively. The lowest reference spur is -58 dBc.

Optical phase-locked loop (OPLL) for free-space laser communications with heterodyne detection

NASA Technical Reports Server (NTRS)

Win, Moe Z.; Chen, Chien-Chung; Scholtz, Robert A.

1991-01-01

Several advantages of coherent free-space optical communications are outlined. Theoretical analysis is formulated for an OPLL disturbed by shot noise, modulation noise, and frequency noise consisting of a white component, a 1/f component, and a 1/f-squared component. Each of the noise components is characterized by its associated power spectral density. It is shown that the effect of modulation depends only on the ratio of loop bandwidth and data rate, and is negligible for an OPLL with loop bandwidth smaller than one fourth the data rate. Total phase error variance as a function of loop bandwidth is displayed for several values of carrier signal to noise ratio. Optimal loop bandwidth is also calculated as a function of carrier signal to noise ratio. An OPLL experiment is performed, where it is shown that the measured phase error variance closely matches the theoretical predictions.

A Phase-Locked Loop Epilepsy Network Emulator.

PubMed

Watson, P D; Horecka, K M; Cohen, N J; Ratnam, R

2016-10-15

Most seizure forecasting employs statistical learning techniques that lack a representation of the network interactions that give rise to seizures. We present an epilepsy network emulator (ENE) that uses a network of interconnected phase-locked loops (PLLs) to model synchronous, circuit-level oscillations between electrocorticography (ECoG) electrodes. Using ECoG data from a canine-epilepsy model (Davis et al. 2011) and a physiological entropy measure (approximate entropy or ApEn, Pincus 1995), we demonstrate the entropy of the emulator phases increases dramatically during ictal periods across all ECoG recording sites and across all animals in the sample. Further, this increase precedes the observable voltage spikes that characterize seizure activity in the ECoG data. These results suggest that the ENE is sensitive to phase-domain information in the neural circuits measured by ECoG and that an increase in the entropy of this measure coincides with increasing likelihood of seizure activity. Understanding this unpredictable phase-domain electrical activity present in ECoG recordings may provide a target for seizure detection and feedback control.

Phase-locked-loop interferometry applied to aspheric testing with a computer-stored compensator.

PubMed

Servin, M; Malacara, D; Rodriguez-Vera, R

1994-05-01

A recently developed technique for continuous-phase determination of interferograms with a digital phase-locked loop (PLL) is applied to the null testing of aspheres. Although this PLL demodulating scheme is also a synchronous or direct interferometric technique, the separate unwrapping process is not explicitly required. The unwrapping and the phase-detection processes are achieved simultaneously within the PLL. The proposed method uses a computer-generated holographic compensator. The holographic compensator does not need to be printed out by any means; it is calculated and used from the computer. This computer-stored compensator is used as the reference signal to phase demodulate a sample interferogram obtained from the asphere being tested. Consequently the demodulated phase contains information about the wave-front departures from the ideal computer-stored aspheric interferogram. Wave-front differences of ~ 1 λ are handled easily by the proposed PLL scheme. The maximum recorded frequency in the template's interferogram as well as in the sampled interferogram are assumed to be below the Nyquist frequency.

Pulsed Phase Lock Loop Device for Monitoring Intracranial Pressure During Space Flight

NASA Technical Reports Server (NTRS)

Ueno, Toshiaki; Macias, Brandon R.; Yost, William T.; Hargens, Alan R.

2003-01-01

We have developed an ultrasonic device to monitor ICP waveforms non-invasively from cranial diameter oscillations using a NASA-developed pulsed phase lock loop (PPLL) technique. The purpose of this study was to attempt to validate the PPLL device for reliable recordings of ICP waveforms and analysis of ICP dynamics in vivo. METHODS: PPLL outputs were recorded in patients during invasive ICP monitoring at UCSD Medical Center (n=10). RESULTS: An averaged linear regression coefficient between ICP and PPLL waveform data during one cardiac cycle in all patients is 0.88 +/- 0.02 (mean +/- SE). Coherence function analysis indicated that ICP and PPLL waveforms have high correlation in the lst, 2nd, and 3rd harmonic waves associated with a cardiac cycle. CONCLUSIONS: PPLL outputs represent ICP waveforms in both frequency and time domains. PPLL technology enables in vivo evaluation of ICP dynamics non-invasively, and can acquire continuous ICP waveforms during spaceflight because of compactness and non-invasive nature.

Nondestructive ultrasonic measurement of bolt preload using the pulsed-phase locked-loop interferometer

NASA Technical Reports Server (NTRS)

Allison, S. G.; Heyman, J. S.

1985-01-01

Achieving accurate preload in threaded fasteners is an important and often critical problem which is encountered in nearly all sectors of government and industry. Conventional tensioning methods which rely on torque carry with them the disadvantage of requiring constant friction in the fastener in order to accurately correlate torque to preload. Since most of the applied torque typically overcomes friction rather than tensioning the fastener, small variations in friction can cause large variations in preload. An instrument called a pulsed phase locked loop interferometer, which was recently developed at NASA Langley, has found widespread use for measurement of stress as well as material properties. When used to measure bolt preload, this system detects changes in the fastener length and sound velocity which are independent of friction. The system is therefore capable of accurately establishing the correct change in bolt tension. This high resolution instrument has been used for precision measurement of preload in critical fasteners for numerous applications such as the space shuttle landing gear and helicopter main rotors.

Optimal space communications techniques. [all digital phase locked loop for FM demodulation

NASA Technical Reports Server (NTRS)

Schilling, D. L.

1973-01-01

The design, development, and analysis are reported of a digital phase-locked loop (DPLL) for FM demodulation and threshold extension. One of the features of the developed DPLL is its synchronous, real time operation. The sampling frequency is constant and all the required arithmetic and logic operations are performed within one sampling period, generating an output sequence which is converted to analog form and filtered. An equation relating the sampling frequency to the carrier frequency must be satisfied to guarantee proper DPLL operation. The synchronous operation enables a time-shared operation of one DPLL to demodulate several FM signals simultaneously. In order to obtain information about the DPLL performance at low input signal-to-noise ratios, a model of an input noise spike was introduced, and the DPLL equation was solved using a digital computer. The spike model was successful in finding a second order DPLL which yielded a five db threshold extension beyond that of a first order DPLL.

Fiber-based coherent polarization beam combining with cascaded phase-locking and polarization-transforming controls

NASA Astrophysics Data System (ADS)

Yang, Yan; Geng, Chao; Li, Feng; Huang, Guan; Li, Xinyang

2018-05-01

In this paper, the fiber-based coherent polarization beam combining (CPBC) with cascaded phase-locking (PL) and polarization-transforming (PT) controls was proposed to combine imbalanced input beams where the number of the input beams is not binary, in which the PL control was performed using the piezoelectric-ring fiber-optic phase compensator, and the PT control was realized by the dynamic polarization controller, simultaneously. The principle of the proposed CPBC was introduced. The performance of the proposed CPBC was analyzed in comparison with the CPBC based on PL control and the CPBC based on PT control. The basic experiment of CPBC of three laser beams was carried out to validate the feasibility of the proposed CPBC, where cascaded controls of PL and PT were implemented based on stochastic parallel gradient descent algorithm. Simulation and experimental results show that the proposed CPBC incorporates the advantages of the two previous CPBC schemes and performs well in the closed loop. Moreover, the expansibility and the application of the proposed CPBC were validated by scaling the CPBC to combine seven laser beams. We believe that the proposed fiber-based CPBC with cascaded PL and PT controls has great potential in free space optical communications employing the multi-aperture receiver with asymmetric structure.

Closed-loop separation control over a sharp edge ramp using genetic programming

NASA Astrophysics Data System (ADS)

Debien, Antoine; von Krbek, Kai A. F. F.; Mazellier, Nicolas; Duriez, Thomas; Cordier, Laurent; Noack, Bernd R.; Abel, Markus W.; Kourta, Azeddine

2016-03-01

We experimentally perform open and closed-loop control of a separating turbulent boundary layer downstream from a sharp edge ramp. The turbulent boundary layer just above the separation point has a Reynolds number Re_{θ }≈ 3500 based on momentum thickness. The goal of the control is to mitigate separation and early re-attachment. The forcing employs a spanwise array of active vortex generators. The flow state is monitored with skin-friction sensors downstream of the actuators. The feedback control law is obtained using model-free genetic programming control (GPC) (Gautier et al. in J Fluid Mech 770:442-457, 2015). The resulting flow is assessed using the momentum coefficient, pressure distribution and skin friction over the ramp and stereo PIV. The PIV yields vector field statistics, e.g. shear layer growth, the back-flow area and vortex region. GPC is benchmarked against the best periodic forcing. While open-loop control achieves separation reduction by locking-on the shedding mode, GPC gives rise to similar benefits by accelerating the shear layer growth. Moreover, GPC uses less actuation energy.

Commutated automatic gain control system

NASA Technical Reports Server (NTRS)

Yost, S. R.

1982-01-01

A commutated automatic gain control (AGC) system was designed and built for a prototype Loran C receiver. The receiver uses a microcomputer to control a memory aided phase-locked loop (MAPLL). The microcomputer also controls the input/output, latitude/longitude conversion, and the recently added AGC system. The circuit designed for the AGC is described, and bench and flight test results are presented. The AGC circuit described actually samples starting at a point 40 microseconds after a zero crossing determined by the software lock pulse ultimately generated by a 30 microsecond delay and add network in the receiver front end envelope detector.

Model verifies design of mobile data modem

NASA Technical Reports Server (NTRS)

Davarian, F.; Sumida, J.

1986-01-01

It has been proposed to use differential minimum shift keying (DMSK) modems in spacecraft-based mobile communications systems. For an employment of these modems, it is necessary that the transmitted carrier frequency be known prior to signal detection. In addition, the time needed by the receiver to lock onto the carrier frequency must be minimized. The present article is concerned with a DMSK modem developed for the Mobile Satellite Service. This device demonstrated fast acquisition time and good performance in the presence of fading. However, certain problems arose in initial attempts to study the acquisition behavior of the AFC loop through breadboard techniques. The development of a software model of the AFC loop is discussed, taking into account two cases which were plotted using the model. Attention is given to a demonstration of the viability of the modem by an approach involving modeling and analysis of the frequency synchronizer.

Frequency stabilization for multilocation optical FDM networks

NASA Astrophysics Data System (ADS)

Jiang, Quan; Kavehrad, Mohsen

1993-04-01

In a multi-location optical FDM network, the frequency of each user's transmitter can be offset-locked, through a Fabry-Perot, to an absolute frequency standard which is distributed to the users. To lock the local Fabry-Perot to the frequency standard, the standard has to be frequency-dithered by a sinusoidal signal and the sinusoidal reference has to be transmitted to the user location since the lock-in amplifier in the stabilization system requires the reference for synchronous detection. We proposed two solutions to avoid transmitting the reference. One uses an extraction circuit to obtain the sinusoidal signal from the incoming signal. A nonlinear circuit following the photodiode produces a strong second-order harmonic of the sinusoidal signal and a phase-locked loop is locked to it. The sinusoidal reference is obtained by a divide- by-2 circuit. The phase ambiguity (0 degree(s) or 180 degree(s)) is resolved by using a selection- circuit and an initial scan. The other method uses a pseudo-random sequence instead of a sinusoidal signal to dither the frequency standard and a surface-acoustic-wave (SAW) matched-filter instead of a lock-in amplifier to obtain the frequency error. The matched-filter serves as a correlator and does not require the dither reference.

Digital processing of RF signals from optical frequency combs

NASA Astrophysics Data System (ADS)

Cizek, Martin; Smid, Radek; Buchta, Zdeněk.; Mikel, Břetislav; Lazar, Josef; Cip, Ondřej

2013-01-01

The presented work is focused on digital processing of beat note signals from a femtosecond optical frequency comb. The levels of mixing products of single spectral components of the comb with CW laser sources are usually very low compared to products of mixing all the comb components together. RF counters are more likely to measure the frequency of the strongest spectral component rather than a weak beat note. Proposed experimental digital signal processing system solves this problem by analyzing the whole spectrum of the output RF signal and using software defined radio (SDR) algorithms. Our efforts concentrate in two main areas: Firstly, using digital servo-loop techniques for locking free running continuous laser sources on single components of the fs comb spectrum. Secondly, we are experimenting with digital signal processing of the RF beat note spectrum produced by f-2f 1 technique used for assessing the offset and repetition frequencies of the comb, resulting in digital servo-loop stabilization of the fs comb. Software capable of computing and analyzing the beat-note RF spectrums using FFT and peak detection was developed. A SDR algorithm performing phase demodulation on the f- 2f signal is used as a regulation error signal source for a digital phase-locked loop stabilizing the offset frequency of the fs comb.

Digital processing of signals from femtosecond combs

NASA Astrophysics Data System (ADS)

Čížek, Martin; Šmíd, Radek; Buchta, Zdeněk.; Mikel, Břetislav; Lazar, Josef; Číp, Ondrej

2012-01-01

The presented work is focused on digital processing of beat note signals from a femtosecond optical frequency comb. The levels of mixing products of single spectral components of the comb with CW laser sources are usually very low compared to products of mixing all the comb components together. RF counters are more likely to measure the frequency of the strongest spectral component rather than a weak beat note. Proposed experimental digital signal processing system solves this problem by analyzing the whole spectrum of the output RF signal and using software defined radio (SDR) algorithms. Our efforts concentrate in two main areas: Firstly, we are experimenting with digital signal processing of the RF beat note spectrum produced by f-2f 1 technique and with fully digital servo-loop stabilization of the fs comb. Secondly, we are using digital servo-loop techniques for locking free running continuous laser sources on single components of the fs comb spectrum. Software capable of computing and analyzing the beat-note RF spectrums using FFT and peak detection was developed. A SDR algorithm performing phase demodulation on the f- 2f signal is used as a regulation error signal source for a digital phase-locked loop stabilizing the offset and repetition frequencies of the fs comb.

Reduction of Urease Activity by Interaction with the Flap Covering the Active Site

PubMed Central

Macomber, Lee; Minkara, Mona S.; Hausinger, Robert P.; Merz, Kenneth M.

2015-01-01

With the increasing appreciation for the human microbiome coupled with the global rise of antibiotic resistant organisms, it is imperative that new methods be developed to specifically target pathogens. To that end, a novel computational approach was devised to identify compounds that reduce the activity of urease, a medically important enzyme of Helicobacter pylori, Proteus mirabilis, and many other microorganisms. Urease contains a flexible loop that covers its active site; Glide was used to identify small molecules predicted to lock this loop in an open conformation. These compounds were screened against the model urease from Klebsiella aerogenes and the natural products epigallocatechin and quercetin were shown to inhibit at low and high micromolar concentrations, respectively. These molecules exhibit a strong time-dependent inactivation of urease that was not due to their oxygen sensitivity. Rather, these compounds appear to inactivate urease by reacting with a specific Cys residue located on the flexible loop. Substitution of this cysteine by alanine in the C319A variant increased the urease resistance to both epigallocatechin and quercetin, as predicted by the computational studies. Protein dynamics are integral to the function of many enzymes; thus, identification of compounds that lock an enzyme into a single conformation presents a useful approach to define potential inhibitors. PMID:25594724

A monolithic K-band phase-locked loop for microwave radar application

NASA Astrophysics Data System (ADS)

Zhou, Guangyao; Ma, Shunli; Li, Ning; Ye, Fan; Ren, Junyan

2017-02-01

A monolithic K-band phase-locked loop (PLL) for microwave radar application is proposed and implemented in this paper. By eliminating the tail transistor and using optimized high-Q LC-tank, the proposed voltage-controlled oscillator (VCO) achieves a tuning range of 18.4 to 23.3 GHz and reduced phase noise. Two cascaded current-mode logic (CML) divide-by-two frequency prescalers are implemented to bridge the frequency gap, in which inductor peaking technique is used in the first stage to further boost allowable input frequency. Six-stage TSPC divider chain is used to provide programmable division ratio from 64 to 127, and a second-order passive loop filter with 825 kHz bandwidth is also integrated on-chip to minimize required external components. The proposed PLL needs only approximately 18.2 μs settling time, and achieves a wide tuning range from 18.4 to 23.3 GHz, with a typical output power of ‑0.84 dBm and phase noise of ‑91.92 dBc/Hz @ 1 MHz. The chip is implemented in TSMC 65 nm CMOS process, and occupies an area of 0.56 mm2 without pads under a 1.2 V single voltage supply. Project supported by the National High-Tech Research and Development Program of China (No. 2013AA014101).

A high-speed, tunable silicon photonic ring modulator integrated with ultra-efficient active wavelength control.

PubMed

Zheng, Xuezhe; Chang, Eric; Amberg, Philip; Shubin, Ivan; Lexau, Jon; Liu, Frankie; Thacker, Hiren; Djordjevic, Stevan S; Lin, Shiyun; Luo, Ying; Yao, Jin; Lee, Jin-Hyoung; Raj, Kannan; Ho, Ron; Cunningham, John E; Krishnamoorthy, Ashok V

2014-05-19

We report the first complete 10G silicon photonic ring modulator with integrated ultra-efficient CMOS driver and closed-loop wavelength control. A selective substrate removal technique was used to improve the ring tuning efficiency. Limited by the thermal tuner driver output power, a maximum open-loop tuning range of about 4.5nm was measured with about 14mW of total tuning power including the heater driver circuit power consumption. Stable wavelength locking was achieved with a low-power mixed-signal closed-loop wavelength controller. An active wavelength tracking range of > 500GHz was demonstrated with controller energy cost of only 20fJ/bit.

Development and preclinical testing of a new tension-band device for the spine: the Loop system.

PubMed

Garner, Matthew D; Wolfe, Steven J; Kuslich, Stephen D

2002-10-01

Wire sutures, cerclage constructs, and tension bands have been used for many years in orthopedic surgery. Spinous process and sublaminar wires and other strands or cables are used in the spine to re-establish stability of the posterior spinal ligament complex. Rigid monofilament wires often fail due to weakening created during twisting or wrapping. Stronger metal cables do not conform well to bony surfaces. Polyethylene cables have higher fatigue strength than metal cables. The Loop cable is a pliable, radiolucent, polyethylene braid. Creep of the Loop/locking clip construct is similar to metal cable constructs using crimps. Both systems have less creep than knotted polyethylene cable constructs.

Autopilot for frequency-modulation atomic force microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuchuk, Kfir; Schlesinger, Itai; Sivan, Uri, E-mail: phsivan@tx.technion.ac.il

2015-10-15

One of the most challenging aspects of operating an atomic force microscope (AFM) is finding optimal feedback parameters. This statement applies particularly to frequency-modulation AFM (FM-AFM), which utilizes three feedback loops to control the cantilever excitation amplitude, cantilever excitation frequency, and z-piezo extension. These loops are regulated by a set of feedback parameters, tuned by the user to optimize stability, sensitivity, and noise in the imaging process. Optimization of these parameters is difficult due to the coupling between the frequency and z-piezo feedback loops by the non-linear tip-sample interaction. Four proportional-integral (PI) parameters and two lock-in parameters regulating these loopsmore » require simultaneous optimization in the presence of a varying unknown tip-sample coupling. Presently, this optimization is done manually in a tedious process of trial and error. Here, we report on the development and implementation of an algorithm that computes the control parameters automatically. The algorithm reads the unperturbed cantilever resonance frequency, its quality factor, and the z-piezo driving signal power spectral density. It analyzes the poles and zeros of the total closed loop transfer function, extracts the unknown tip-sample transfer function, and finds four PI parameters and two lock-in parameters for the frequency and z-piezo control loops that optimize the bandwidth and step response of the total system. Implementation of the algorithm in a home-built AFM shows that the calculated parameters are consistently excellent and rarely require further tweaking by the user. The new algorithm saves the precious time of experienced users, facilitates utilization of FM-AFM by casual users, and removes the main hurdle on the way to fully automated FM-AFM.« less

Performance Analysis of Digital Tracking Loops for Telemetry Ranging Applications

NASA Astrophysics Data System (ADS)

Vilnrotter, V.; Hamkins, J.; Xie, H.; Ashrafi, S.

2015-08-01

In this article, we analyze mathematical models of digital loops used to track the phase and timing of communications and navigation signals. The limits on the accuracy of phase and timing estimates play a critical role in the accuracy achievable in telemetry ranging applications. We describe in detail a practical algorithm to compute the loop parameters for discrete update (DU) and continuous update (CU) loop formulations, and we show that a simple power-series approximation to the DU model is valid over a large range of time-bandwidth product . Several numerical examples compare the estimation error variance of the DU and CU models to each other and to Cramer-Rao lower bounds. Finally, the results are applied to the problem of ranging, by evaluating the performance of a phase-locked loop designed to track a typical ambiguity-resolving pseudonoise (PN) code received and demodulated at the spacecraft on the uplink part of the two-way ranging link, and a data transition tracking loop (DTTL) on the downlink part.

A comparison of methods for DPLL loop filter design

NASA Technical Reports Server (NTRS)

Aguirre, S.; Hurd, W. J.; Kumar, R.; Statman, J.

1986-01-01

Four design methodologies for loop filters for a class of digital phase-locked loops (DPLLs) are presented. The first design maps an optimum analog filter into the digital domain; the second approach designs a filter that minimizes in discrete time weighted combination of the variance of the phase error due to noise and the sum square of the deterministic phase error component; the third method uses Kalman filter estimation theory to design a filter composed of a least squares fading memory estimator and a predictor. The last design relies on classical theory, including rules for the design of compensators. Linear analysis is used throughout the article to compare different designs, and includes stability, steady state performance and transient behavior of the loops. Design methodology is not critical when the loop update rate can be made high relative to loop bandwidth, as the performance approaches that of continuous time. For low update rates, however, the miminization method is significantly superior to the other methods.

All-digital signal-processing open-loop fiber-optic gyroscope with enlarged dynamic range.

PubMed

Wang, Qin; Yang, Chuanchuan; Wang, Xinyue; Wang, Ziyu

2013-12-15

We propose and realize a new open-loop fiber-optic gyroscope (FOG) with an all-digital signal-processing (DSP) system where an all-digital phase-locked loop is employed for digital demodulation to eliminate the variation of the source intensity and suppress the bias drift. A Sagnac phase-shift tracking method is proposed to enlarge the dynamic range, and, with its aid, a new open-loop FOG, which can achieve a large dynamic range and high sensitivity at the same time, is realized. The experimental results show that compared with the conventional open-loop FOG with the same fiber coil and optical devices, the proposed FOG reduces the bias instability from 0.259 to 0.018 deg/h, and the angle random walk from 0.031 to 0.006 deg/h(1/2), moreover, enlarges the dynamic range to ±360 deg/s, exceeding the maximum dynamic range ±63 deg/s of the conventional open-loop FOG.

GPS/IGS Design Analysis Report. Volume 1

DTIC Science & Technology

1982-11-15

PLL Phase Lock Loop FMPCB Parts, Hateriala, and Processes Control Board PPPL Program Preferred Parts List P14 Pseudo-Rando* Noise PSI Peculiar Support...program preferred ?arts list ( PPPL ). Where ?PPL parts were not obtainable, screening, burn-in, and other tes. were imposed on those parts to assure

Phase-locked loop with controlled phase slippage

DOEpatents

Mestha, L.K.

1994-03-29

A system for synchronizing a first subsystem controlled by a changing frequency sweeping from a first frequency to a second frequency, with a second subsystem operating at a steady state second frequency is described. Trip plan parameters are calculated in advance to determine the phase relationship between the frequencies of the first subsystem and second subsystem in order to obtain synchronism at the end of the frequency sweep of the first subsystem. During the time in which the frequency of the first subsystem is sweeping from the first frequency to the second frequency, the phase locked system compares the actual phase difference with the trip plan phase difference and incrementally changes the sweep frequency in a manner so that phase lock is achieved when the first subsystem reaches a frequency substantially identical to that of the second subsystem. 10 figures.

A tunable, double-wavelength heterodyne detection interferometer with frequency-locked diode-pumped Nd:YAG sources for absolute measurements

NASA Astrophysics Data System (ADS)

Gelmini, E.; Minoni, U.; Docchio, F.

1995-08-01

A double heterodyne interferometric instrument using a tunable synthetic wavelength for the absolute measurements of distance and position is presented. The optical synthetic wavelength is generated by a pair of PZT-tunable diode-pumped Nd:YAG lasers operating at 1.064 μm. Based on a closed-loop scheme, a suitable electronic circuit has been developed to implement the frequency locking of the two lasers. A digital frequency comparator provides an error signal, used to control the slave laser, by comparing the laser beat frequency to a reference oscillator. Demodulation of the superheterodyne signals is obtained by a rf detector followed by low-pass filtering. Distance measurements are obtained by a digital phase meter gauging the phase difference between the demodulated signals from a measuring interferometer and from a reference interferometer. The paper presents the optical and the electronic layouts of the instrument as well as experimental results from a laboratory prototype.

Laser interrogation techniques for high-sensitivity strain sensing by fiber-Bragg-grating structures

NASA Astrophysics Data System (ADS)

Gagliardi, G.; Salza, M.; Ferraro, P.; De Natale, P.

2017-11-01

Novel interrogation methods for static and dynamic measurements of mechanical deformations by fiber Bragg-gratings (FBGs) structures are presented. The sensor-reflected radiation gives information on suffered strain, with a sensitivity dependent on the interrogation setup. Different approaches have been carried out, based on laser-frequency modulation techniques and near-IR lasers, to measure strain in single-FBG and in resonant high-reflectivity FBG arrays. In particular, for the fiber resonator, the laser frequency is actively locked to the cavity resonances by the Pound-Drever-Hall technique, thus tracking any frequency change due to deformations. The loop error and correction signals fed back to the laser are used as strain monitor. Sensitivity limits vary between 200 nɛ/√Hz in the quasi-static domain (0.5÷2 Hz), and between 1 and 4 nɛ/√Hz in the 0.4-1 kHz range for the single-FBG scheme, while strain down to 50 pɛ can be detected by using the laser-cavity-locked method.

Beat note stabilization of a 10-60 GHz dual-polarization microlaser through optical down conversion.

PubMed

Rolland, A; Brunel, M; Loas, G; Frein, L; Vallet, M; Alouini, M

2011-02-28

Down-conversion of a high-frequency beat note to an intermediate frequency is realized by a Mach-Zehnder intensity modulator. Optically-carried microwave signals in the 10-60 GHz range are synthesized by using a two-frequency solid-state microchip laser as a voltage-controlled oscillator inside a digital phase-locked loop. We report an in-loop relative frequency stability better than 2.5×10⁻¹¹. The principle is applicable to beat notes in the millimeter-wave range.

Long range dynamic effects of point-mutations trap a response regulator in an active conformation

PubMed Central

Bobay, Benjamin G.; Thompson, Richele J.; Hoch, James A.; Cavanagh, John

2010-01-01

When a point-mutation in a protein elicits a functional change, it is most common to assign this change to local structural perturbations. Here we show that point-mutations, distant from an essential highly dynamic kinase recognition loop in the response regulator Spo0F, lock this loop in an active conformation. This ‘conformational trapping’ results in functionally hyperactive Spo0F. Consequently, point-mutations are seen to affect functionally critical motions both close to and far from the mutational site. PMID:20828564

Improvements in deep-space tracking by use of third-order loops.

NASA Technical Reports Server (NTRS)

Tausworth, R. C.; Crow, R. B.

1972-01-01

Third-order phase-locked receivers have not yet found wide application in deep-space communications systems because the second-order systems now used have performed adequately on past spacecraft missions. However, a survey of the doppler profiles for future missions shows that an unaided second-order loop may be unable to perform within reasonable error bounds. This article discusses the characteristics of a simple third-order extension to present second-order systems that not only extends doppler-tracking capability, but widens the pull-in range and decreases pull-in time as well.

Performance Improvement of Receivers Based on Ultra-Tight Integration in GNSS-Challenged Environments

PubMed Central

Qin, Feng; Zhan, Xingqun; Du, Gang

2013-01-01

Ultra-tight integration was first proposed by Abbott in 2003 with the purpose of integrating a global navigation satellite system (GNSS) and an inertial navigation system (INS). This technology can improve the tracking performances of a receiver by reconfiguring the tracking loops in GNSS-challenged environments. In this paper, the models of all error sources known to date in the phase lock loops (PLLs) of a standard receiver and an ultra-tightly integrated GNSS/INS receiver are built, respectively. Based on these models, the tracking performances of the two receivers are compared to verify the improvement due to the ultra-tight integration. Meanwhile, the PLL error distributions of the two receivers are also depicted to analyze the error changes of the tracking loops. These results show that the tracking error is significantly reduced in the ultra-tightly integrated GNSS/INS receiver since the receiver's dynamics are estimated and compensated by an INS. Moreover, the mathematical relationship between the tracking performances of the ultra-tightly integrated GNSS/INS receiver and the quality of the selected inertial measurement unit (IMU) is derived from the error models and proved by the error comparisons of four ultra-tightly integrated GNSS/INS receivers aided by different grade IMUs.

Doppler extraction with a digital VCO

NASA Technical Reports Server (NTRS)

Starner, E. R.; Nossen, E. J.

1977-01-01

Digitally controlled oscillator in phased-locked loop may be useful for data communications systems, or may be modified to serve as information extraction component of microwave or optical system for collision avoidance or automatic braking. Instrument is frequency-synthesizing device with output specified precisely by digital number programmed into frequency register.

Modeling and simulation of continuous wave velocity radar based on third-order DPLL

NASA Astrophysics Data System (ADS)

Di, Yan; Zhu, Chen; Hong, Ma

2015-02-01

Second-order digital phase-locked-loop (DPLL) is widely used in traditional Continuous wave (CW) velocity radar with poor performance in high dynamic conditions. Using the third-order DPLL can improve the performance. Firstly, the echo signal model of CW radar is given. Secondly, theoretical derivations of the tracking performance in different velocity conditions are given. Finally, simulation model of CW radar is established based on Simulink tool. Tracking performance of the two kinds of DPLL in different acceleration and jerk conditions is studied by this model. The results show that third-order PLL has better performance in high dynamic conditions. This model provides a platform for further research of CW radar.

An ABS control logic based on wheel force measurement

NASA Astrophysics Data System (ADS)

Capra, D.; Galvagno, E.; Ondrak, V.; van Leeuwen, B.; Vigliani, A.

2012-12-01

The paper presents an anti-lock braking system (ABS) control logic based on the measurement of the longitudinal forces at the hub bearings. The availability of force information allows to design a logic that does not rely on the estimation of the tyre-road friction coefficient, since it continuously tries to exploit the maximum longitudinal tyre force. The logic is designed by means of computer simulation and then tested on a specific hardware in the loop test bench: the experimental results confirm that measured wheel force can lead to a significant improvement of the ABS performances in terms of stopping distance also in the presence of road with variable friction coefficient.

Entrainment and Control of Bacterial Populations: An in Silico Study over a Spatially Extended Agent Based Model.

PubMed

Mina, Petros; Tsaneva-Atanasova, Krasimira; Bernardo, Mario di

2016-07-15

We extend a spatially explicit agent based model (ABM) developed previously to investigate entrainment and control of the emergent behavior of a population of synchronized oscillating cells in a microfluidic chamber. Unlike most of the work in models of control of cellular systems which focus on temporal changes, we model individual cells with spatial dependencies which may contribute to certain behavioral responses. We use the model to investigate the response of both open loop and closed loop strategies, such as proportional control (P-control), proportional-integral control (PI-control) and proportional-integral-derivative control (PID-control), to heterogeinities and growth in the cell population, variations of the control parameters and spatial effects such as diffusion in the spatially explicit setting of a microfluidic chamber setup. We show that, as expected from the theory of phase locking in dynamical systems, open loop control can only entrain the cell population in a subset of forcing periods, with a wide variety of dynamical behaviors obtained outside these regions of entrainment. Closed-loop control is shown instead to guarantee entrainment in a much wider region of control parameter space although presenting limitations when the population size increases over a certain threshold. In silico tracking experiments are also performed to validate the ability of classical control approaches to achieve other reference behaviors such as a desired constant output or a linearly varying one. All simulations are carried out in BSim, an advanced agent-based simulator of microbial population which is here extended ad hoc to include the effects of control strategies acting onto the population.

Two-stage system based on a software-defined radio for stabilizing of optical frequency combs in long-term experiments.

PubMed

Cížek, Martin; Hucl, Václav; Hrabina, Jan; Smíd, Radek; Mikel, Břetislav; Lazar, Josef; Cíp, Ondřej

2014-01-20

A passive optical resonator is a special sensor used for measurement of lengths on the nanometer and sub-nanometer scale. A stabilized optical frequency comb can provide an ultimate reference for measuring the wavelength of a tunable laser locked to the optical resonator. If we lock the repetition and offset frequencies of the comb to a high-grade radiofrequency (RF) oscillator its relative frequency stability is transferred from the RF to the optical frequency domain. Experiments in the field of precise length metrology of low-expansion materials are usually of long-term nature so it is required that the optical frequency comb stay in operation for an extended period of time. The optoelectronic closed-loop systems used for stabilization of combs are usually based on traditional analog electronic circuits processing signals from photodetectors. From an experimental point of view, these setups are very complicated and sensitive to ambient conditions, especially in the optical part, therefore maintaining long-time operation is not easy. The research presented in this paper deals with a novel approach based on digital signal processing and a software-defined radio. We describe digital signal processing algorithms intended for keeping the femtosecond optical comb in a long-time stable operation. This need arose during specialized experiments involving measurements of optical frequencies of tunable continuous-wave lasers. The resulting system is capable of keeping the comb in lock for an extensive period of time (8 days or more) with the relative stability better than 1.6 × 10(-11).

Two-Stage System Based on a Software-Defined Radio for Stabilizing of Optical Frequency Combs in Long-Term Experiments

PubMed Central

Čížek, Martin; Hucl, Václav; Hrabina, Jan; Šmíd, Radek; Mikel, Břetislav; Lazar, Josef; Číp, Ondřej

2014-01-01

A passive optical resonator is a special sensor used for measurement of lengths on the nanometer and sub-nanometer scale. Astabilized optical frequency comb can provide an ultimate reference for measuring the wavelength of a tunable laser locked to the optical resonator. If we lock the repetition and offset frequencies of the comb to a high-grade radiofrequency (RF) oscillator its relative frequency stability is transferred from the RF to the optical frequency domain. Experiments in the field of precise length metrology of low-expansion materials are usually of long-term nature so it is required that the optical frequency comb stay in operation for an extended period of time. The optoelectronic closed-loop systems used for stabilization of combs are usually based on traditional analog electronic circuits processing signals from photodetectors. From an experimental point of view, these setups are very complicated and sensitive to ambient conditions, especially in the optical part, therefore maintaining long-time operation is not easy. The research presented in this paper deals with a novel approach based on digital signal processing and a software-defined radio. We describe digital signal processing algorithms intended for keeping the femtosecond optical comb in a long-time stable operation. This need arose during specialized experiments involving measurements of optical frequencies of tunable continuous-wave lasers. The resulting system is capable of keeping the comb in lock for an extensive period of time (8 days or more) with the relative stability better than 1.6 × 10−11. PMID:24448169

Development of high precision digital driver of acoustic-optical frequency shifter for ROG

NASA Astrophysics Data System (ADS)

Zhang, Rong; Kong, Mei; Xu, Yameng

2016-10-01

We develop a high precision digital driver of the acoustic-optical frequency shifter (AOFS) based on the parallel direct digital synthesizer (DDS) technology. We use an atomic clock as the phase-locked loop (PLL) reference clock, and the PLL is realized by a dual digital phase-locked loop. A DDS sampling clock up to 320 MHz with a frequency stability as low as 10-12 Hz is obtained. By constructing the RF signal measurement system, it is measured that the frequency output range of the AOFS-driver is 52-58 MHz, the center frequency of the band-pass filter is 55 MHz, the ripple in the band is less than 1 dB@3MHz, the single channel output power is up to 0.3 W, the frequency stability is 1 ppb (1 hour duration), and the frequency-shift precision is 0.1 Hz. The obtained frequency stability has two orders of improvement compared to that of the analog AOFS-drivers. For the designed binary frequency shift keying (2-FSK) and binary phase shift keying (2-PSK) modulation system, the demodulating frequency of the input TTL synchronous level signal is up to 10 kHz. The designed digital-bus coding/decoding system is compatible with many conventional digital bus protocols. It can interface with the ROG signal detecting software through the integrated drive electronics (IDE) and exchange data with the two DDS frequency-shift channels through the signal detecting software.

Excitation power quantities in phase resonance testing of nonlinear systems with phase-locked-loop excitation

NASA Astrophysics Data System (ADS)

Peter, Simon; Leine, Remco I.

2017-11-01

Phase resonance testing is one method for the experimental extraction of nonlinear normal modes. This paper proposes a novel method for nonlinear phase resonance testing. Firstly, the issue of appropriate excitation is approached on the basis of excitation power considerations. Therefore, power quantities known from nonlinear systems theory in electrical engineering are transferred to nonlinear structural dynamics applications. A new power-based nonlinear mode indicator function is derived, which is generally applicable, reliable and easy to implement in experiments. Secondly, the tuning of the excitation phase is automated by the use of a Phase-Locked-Loop controller. This method provides a very user-friendly and fast way for obtaining the backbone curve. Furthermore, the method allows to exploit specific advantages of phase control such as the robustness for lightly damped systems and the stabilization of unstable branches of the frequency response. The reduced tuning time for the excitation makes the commonly used free-decay measurements for the extraction of backbone curves unnecessary. Instead, steady-state measurements for every point of the curve are obtained. In conjunction with the new mode indicator function, the correlation of every measured point with the associated nonlinear normal mode of the underlying conservative system can be evaluated. Moreover, it is shown that the analysis of the excitation power helps to locate sources of inaccuracies in the force appropriation process. The method is illustrated by a numerical example and its functionality in experiments is demonstrated on a benchmark beam structure.

Stabilizing Microwave Frequency of a Photonic Oscillator

NASA Technical Reports Server (NTRS)

Maleki, Lute; Yu, Nan; Tu, Meirong

2006-01-01

A scheme for stabilizing the frequency of a microwave signal is proposed that exploits the operational characteristics of a coupled optoelectronic oscillator (COEO) and related optoelectronic equipment. An essential element in the scheme is a fiber mode-locked laser (MLL), the optical frequency of which is locked to an atomic transition. In this scheme, the optical frequency stability of the mode-locked laser is transferred to that of the microwave in the same device. Relative to prior schemes for using wideband optical frequency comb to stabilize microwave signals, this scheme is simpler and lends itself more readily to implementation in relatively compact, rugged equipment. The anticipated development of small, low-power, lightweight, highly stable microwave oscillators based on this scheme would afford great benefits in communication, navigation, metrology, and fundamental sciences. COEOs of various designs, at various stages of development, in some cases called by different names, have been described in a number of prior NASA Tech Briefs articles. A COEO is an optoelectronic apparatus that generates both short (picosecond) optical pulses and a steady microwave signal having an ultrahigh degree of spectral purity. The term "coupled optoelectronic" in the full name of such an apparatus signifies that its optical and electronic oscillations are coupled to each other in a single device. The present frequency-stabilization scheme is best described indirectly by describing the laboratory apparatus used to demonstrate it. The apparatus (see figure) includes a COEO that generates a comb-like optical spectrum, the various frequency components of which interfere, producing short optical pulses. This spectrum is centered at a nominal wavelength of 1,560 nm. The spectrum separation of this comb is about 10 GHz, as determined primarily by the length of an optical loop and the bandpass filter in the microwave feedback loop. The optical loop serves as microwave resonator having a very high value of the resonance quality factor (Q). The optical frequency of MLL is then stabilized by locking it to an atomic transition as described below. The COEO contains a tunable 1-nm band-pass optical filter and a piezoelectric-transducer (PZT) drum over which a stretch of fiber is wound. The 1-nm-wide pass band of the filter provides coarse tuning to overlap the frequency comb with the atomic transition frequency. Controlled stretching of the fiber by means of the PZT drum can be used in conjunction with temperature control for locking the laser frequency. To reference to an atomic resonance at 780 nm in this demonstration setup, the optical output of the COEO at 1,560 nm is fed through an erbium-doped-fiber amplifier (EDFA) to a frequency doubler in the form of a periodically poled lithium niobate (PPLN) crystal. The frequency-doubled output is combined with the output of a separate frequency-stabilized diode laser at a photodetector. As described thus far, the two 780-nm laser subsystems are nominally independent of each other and can, therefore, operate at different frequencies. Hence, at the photodetector, the two laser beams interfere, so that the output of the photodetector includes a beat note (a component at the difference between the two laser frequencies).

Concerted Interconversion between Ionic Lock Substates of the β2 Adrenergic Receptor Revealed by Microsecond Timescale Molecular Dynamics

PubMed Central

Romo, Tod D.; Grossfield, Alan; Pitman, Michael C.

2010-01-01

Abstract The recently solved crystallographic structures for the A2A adenosine receptor and the β1 and β2 adrenergic receptors have shown important differences between members of the class-A G-protein-coupled receptors and their archetypal model, rhodopsin, such as the apparent breaking of the ionic lock that stabilizes the inactive structure. Here, we characterize a 1.02 μs all-atom simulation of an apo-β2 adrenergic receptor that is missing the third intracellular loop to better understand the inactive structure. Although we find that the structure is remarkably rigid, there is a rapid influx of water into the core of the protein, as well as a slight expansion of the molecule relative to the crystal structure. In contrast to the x-ray crystal structures, the ionic lock rapidly reforms, although we see an activation-precursor-like event wherein the ionic lock opens for ∼200 ns, accompanied by movements in the transmembrane helices associated with activation. When the lock reforms, we see the structure return to its inactive conformation. We also find that the ionic lock exists in three states: closed (or locked), semi-open with a bridging water molecule, and open. The interconversion of these states involves the concerted motion of the entire protein. We characterize these states and the concerted motion underlying their interconversion. These findings may help elucidate the connection between key local events and the associated global structural changes during activation. PMID:20074514

Adaptive gain, equalization, and wavelength stabilization techniques for silicon photonic microring resonator-based optical receivers

NASA Astrophysics Data System (ADS)

Palermo, Samuel; Chiang, Patrick; Yu, Kunzhi; Bai, Rui; Li, Cheng; Chen, Chin-Hui; Fiorentino, Marco; Beausoleil, Ray; Li, Hao; Shafik, Ayman; Titriku, Alex

2016-03-01

Interconnect architectures based on high-Q silicon photonic microring resonator devices offer a promising solution to address the dramatic increase in datacenter I/O bandwidth demands due to their ability to realize wavelength-division multiplexing (WDM) in a compact and energy efficient manner. However, challenges exist in realizing efficient receivers for these systems due to varying per-channel link budgets, sensitivity requirements, and ring resonance wavelength shifts. This paper reports on adaptive optical receiver design techniques which address these issues and have been demonstrated in two hybrid-integrated prototypes based on microring drop filters and waveguide photodetectors implemented in a 130nm SOI process and high-speed optical front-ends designed in 65nm CMOS. A 10Gb/s powerscalable architecture employs supply voltage scaling of a three inverter-stage transimpedance amplifier (TIA) that is adapted with an eye-monitor control loop to yield the necessary sensitivity for a given channel. As reduction of TIA input-referred noise is more critical at higher data rates, a 25Gb/s design utilizes a large input-stage feedback resistor TIA cascaded with a continuous-time linear equalizer (CTLE) that compensates for the increased input pole. When tested with a waveguide Ge PD with 0.45A/W responsivity, this topology achieves 25Gb/s operation with -8.2dBm sensitivity at a BER=10-12. In order to address microring drop filters sensitivity to fabrication tolerances and thermal variations, efficient wavelength-stabilization control loops are necessary. A peak-power-based monitoring loop which locks the drop filter to the input wavelength, while achieving compatibility with the high-speed TIA offset-correction feedback loop is implemented with a 0.7nm tuning range at 43μW/GHz efficiency.

An automatic frequency control loop using overlapping DFTs (Discrete Fourier Transforms)

NASA Technical Reports Server (NTRS)

Aguirre, S.

1988-01-01

An automatic frequency control (AFC) loop is introduced and analyzed in detail. The new scheme is a generalization of the well known Cross Product AFC loop that uses running overlapping discrete Fourier transforms (DFTs) to create a discriminator curve. Linear analysis is included and supported with computer simulations. The algorithm is tested in a low carrier to noise ratio (CNR) dynamic environment, and the probability of loss of lock is estimated via computer simulations. The algorithm discussed is a suboptimum tracking scheme with a larger frequency error variance compared to an optimum strategy, but offers simplicity of implementation and a very low operating threshold CNR. This technique can be applied during the carrier acquisition and re-acquisition process in the Advanced Receiver.

Wide bandwidth phase-locked loop circuit

NASA Technical Reports Server (NTRS)

Koudelka, Robert David (Inventor)

2005-01-01

A PLL circuit uses a multiple frequency range PLL in order to phase lock input signals having a wide range of frequencies. The PLL includes a VCO capable of operating in multiple different frequency ranges and a divider bank independently configurable to divide the output of the VCO. A frequency detector detects a frequency of the input signal and a frequency selector selects an appropriate frequency range for the PLL. The frequency selector automatically switches the PLL to a different frequency range as needed in response to a change in the input signal frequency. Frequency range hysteresis is implemented to avoid operating the PLL near a frequency range boundary.

Shot-noise-limited monitoring and phase locking of the motion of a single trapped ion.

PubMed

Bushev, P; Hétet, G; Slodička, L; Rotter, D; Wilson, M A; Schmidt-Kaler, F; Eschner, J; Blatt, R

2013-03-29

We perform a high-resolution real-time readout of the motion of a single trapped and laser-cooled Ba+ ion. By using an interferometric setup, we demonstrate a shot-noise-limited measurement of thermal oscillations with a resolution of 4 times the standard quantum limit. We apply the real-time monitoring for phase control of the ion motion through a feedback loop, suppressing the photon recoil-induced phase diffusion. Because of the spectral narrowing in the phase-locked mode, the coherent ion oscillation is measured with a resolution of about 0.3 times the standard quantum limit.

Electronically tunable phase locked loop oscillator

NASA Astrophysics Data System (ADS)

Balasis, M.; Davis, M. R.; Jackson, C. R.

1982-02-01

This report describes the design and development of a low noise, high power, variable oscillator incorporating a high 'Q' electronically tunable resonator as the frequency determining element. The VCO provides improved EMC performance in phase locked synthesizers which are a part of communications equipments. The oscillator combines a low noise VMOS transistor with the selectivity and out-of-band attenuation of a coaxial resonator to provide superior EMC performance. Several oscillator designs were examined and the basis for the final configuration is presented. Oscillator noise is discussed and models for analysis are explained. A brass board model was constructed and tested and the technical results are presented.

Imaging the developing heart: synchronized time-lapse microscopy during developmental changes

NASA Astrophysics Data System (ADS)

Nelson, Carl J.; Buckley, Charlotte; Mullins, John J.; Denvir, Martin A.; Taylor, Jonathan

2018-02-01

How do you use imaging to analyse the development of the heart, which not only changes shape but also undergoes constant, high-speed, quasi-periodic changes? We have integrated ideas from prospective and retrospective optical gating to capture long-term, phase-locked developmental time-lapse videos. In this paper we demonstrate the success of this approach over a key developmental time period: heart looping, where large changes in heart shape prevent previous prospective gating approaches from capturing phase- locked videos. We use the comparison with other approaches to in vivo heart imaging to highlight the importance of collecting the most appropriate data for the biological question.

Ultrastable laser array at 633 nm for real-time dimensional metrology

NASA Astrophysics Data System (ADS)

Lawall, John; Pedulla, J. Marc; Le Coq, Yann

2001-07-01

We describe a laser system for very-high-accuracy dimensional metrology. A sealed-cavity helium-neon laser is offset locked to an iodine-stabilized laser in order to realize a secondary standard with higher power and less phase noise. Synchronous averaging is employed to remove the effect of the frequency modulation present on the iodine-stabilized laser. Additional lasers are offset locked to the secondary standard for use in interferometry. All servo loops are implemented digitally. The offset-locked lasers have intrinsic linewidths of the order of 2.5 kHz and exhibit a rms deviation from the iodine-stabilized laser below 18 kHz. The amplitude noise is at the shot-noise limit for frequencies above 700 kHz. We describe and evaluate the system in detail, and include a discussion of the noise associated with various types of power supplies.

An efficient magnetron transmitter for superconducting accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kazakevich, G.; Lebedev, V.; Yakovlev, V.

A concept of a highly-efficient high-power magnetron transmitter allowing wide-band phase and the mid-frequency power control at the frequency of the locking signal is proposed. The proposal is aimed for powering Superconducting RF (SRF) cavities of intensity-frontier accelerators. The transmitter is intended to operate with phase and amplitude control feedback loops allowing suppression of microphonics and beam loading in the SRF cavities. The concept utilizes injectionlocked magnetrons controlled in phase by the locking signal supplied by a feedback system. The injection-locking signal pre-excites the magnetron and allows its operation below the critical voltage. This realizes control of the magnetron powermore » in a wide range by control of the magnetron current. Pre-excitation of the magnetron by the locking signal provides an output power range up to 10 dB. Experimental studies were carried out with 2.45 GHz, 1 kW, CW magnetrons. They demonstrated stable operation of the magnetrons and power control at a low noise level. In conclusion, an analysis of the kinetics of the drifting charge in the drift approximation substantiates the concept and the experimental results.« less

Optical Frequency Stabilization and Optical Phase Locked Loops: Golden Threads of Precision Measurement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taubman, Matthew S.

Stabilization of lasers through locking to optical cavities, atomic transitions, and molecular transitions has enabled the field of precision optical measurement since shortly after the invention of the laser. Recent advances in the field have produced an optical clock that is orders of magnitude more stable than those of just a few years prior. Phase locking of one laser to another, or to a frequency offset from another, formed the basis for linking stable lasers across the optical spectrum, such frequency chains exhibiting progressively finer precision through the years. Phase locking between the modes within a femtosecond pulsed laser hasmore » yielded the optical frequency comb, one of the most beautiful and useful instruments of our time. This talk gives an overview of these topics, from early work through to the latest 1E-16 thermal noise-limited precision recently attained for a stable laser, and the ongoing quest for ever finer precision and accuracy. The issues of understanding and measuring line widths and shapes are also studied in some depth, highlighting implications for servo design for sub-Hz line widths.« less

An efficient magnetron transmitter for superconducting accelerators

DOE PAGES

Kazakevich, G.; Lebedev, V.; Yakovlev, V.; ...

2016-09-22

A concept of a highly-efficient high-power magnetron transmitter allowing wide-band phase and the mid-frequency power control at the frequency of the locking signal is proposed. The proposal is aimed for powering Superconducting RF (SRF) cavities of intensity-frontier accelerators. The transmitter is intended to operate with phase and amplitude control feedback loops allowing suppression of microphonics and beam loading in the SRF cavities. The concept utilizes injectionlocked magnetrons controlled in phase by the locking signal supplied by a feedback system. The injection-locking signal pre-excites the magnetron and allows its operation below the critical voltage. This realizes control of the magnetron powermore » in a wide range by control of the magnetron current. Pre-excitation of the magnetron by the locking signal provides an output power range up to 10 dB. Experimental studies were carried out with 2.45 GHz, 1 kW, CW magnetrons. They demonstrated stable operation of the magnetrons and power control at a low noise level. In conclusion, an analysis of the kinetics of the drifting charge in the drift approximation substantiates the concept and the experimental results.« less

Electrical crosstalk-coupling measurement and analysis for digital closed loop fibre optic gyro

NASA Astrophysics Data System (ADS)

Jin, Jing; Tian, Hai-Ting; Pan, Xiong; Song, Ning-Fang

2010-03-01

The phase modulation and the closed-loop controller can generate electrical crosstalk-coupling in digital closed-loop fibre optic gyro. Four electrical cross-coupling paths are verified by the open-loop testing approach. It is found the variation of ramp amplitude will lead to the alternation of gyro bias. The amplitude and the phase parameters of the electrical crosstalk signal are measured by lock-in amplifier, and the variation of gyro bias is confirmed to be caused by the alternation of phase according to the amplitude of the ramp. A digital closed-loop fibre optic gyro electrical crosstalk-coupling model is built by approximating the electrical cross-coupling paths as a proportion and integration segment. The results of simulation and experiment show that the modulation signal electrical crosstalk-coupling can cause the dead zone of the gyro when a small angular velocity is inputted, and it could also lead to a periodic vibration of the bias error of the gyro when a large angular velocity is inputted.

All optical coherent receiver for self-homodyne detection of digitally phase modulated optical signals

NASA Astrophysics Data System (ADS)

Kiasaleh, Kamran

1994-02-01

A novel optical phase-locked loop (OPLL) system for the self-homodyne detection of digitally phase modulated optical signals is introduced. A Mach-Zehnder type interferometer is used to self-homodyne binary phase-modulated optical signals with an external phase modulator inserted in the control arm of the interferometer.

Improved PLL For FM Demodulator

NASA Technical Reports Server (NTRS)

Kirkham, Harold; Jackson, Shannon P.

1992-01-01

Phase-locked loop (PLL) for frequency demodulator contains improved frequency-to-voltage converter producing less ripple than conventional phase detector. In improved PLL, phase detector replaced by state estimator, implemented by ramp/sample-and-hold circuit. Intended to reduce noise in receiver of frequency-modulated (FM) telemetry link without sacrificing bandwidth. Also applicable to processing received FM signals.

Modeling and Simulation of a DG-Integrated Intelligent Microgrid

DTIC Science & Technology

2010-02-01

17. The I-V curve from the manufacturer for BP-4175 175W PV module...........................32   Fig. 18. Wind turbine model...33   Fig. 19. Electrical outputs of wind turbine... PMSG : Permanent Magnet Synchronous Generator PLL : Phase Lock Loop PV : Photovoltaic PWM : Pulse Width Modulation TOU : Time of Use VTES

Design of a hybrid receiver for the OLYMPUS spacecraft beacons

NASA Technical Reports Server (NTRS)

Sweeney, D. G.; Mckeeman, J. C.

1990-01-01

The theory and design of a hybrid analogue/digital receiver which acquires and monitors the OLYMPUS satellite beacons is presented. The analogue portion of this receiver uses a frequency locked loop for signal tracking. A digital sampling detector operating at IF is used to obtain the I and Q outputs.

A hybrid analog-digital phase-locked loop for frequency mode non-contact scanning probe microscopy.

PubMed

Mehta, M M; Chandrasekhar, V

2014-01-01

Non-contact scanning probe microscopy (SPM) has developed into a powerful technique to image many different properties of samples. The conventional method involves monitoring the amplitude, phase, or frequency of a cantilever oscillating at or near its resonant frequency as it is scanned across the surface of a sample. For high Q factor cantilevers, monitoring the resonant frequency is the preferred method in order to obtain reasonable scan times. This can be done by using a phase-locked-loop (PLL). PLLs can be obtained as commercial integrated circuits, but these do not have the frequency resolution required for SPM. To increase the resolution, all-digital PLLs requiring sophisticated digital signal processors or field programmable gate arrays have also been implemented. We describe here a hybrid analog/digital PLL where most of the components are implemented using discrete analog integrated circuits, but the frequency resolution is provided by a direct digital synthesis chip controlled by a simple peripheral interface controller (PIC) microcontroller. The PLL has excellent frequency resolution and noise, and can be controlled and read by a computer via a universal serial bus connection.

A hybrid analog-digital phase-locked loop for frequency mode non-contact scanning probe microscopy

NASA Astrophysics Data System (ADS)

Mehta, M. M.; Chandrasekhar, V.

2014-01-01

Non-contact scanning probe microscopy (SPM) has developed into a powerful technique to image many different properties of samples. The conventional method involves monitoring the amplitude, phase, or frequency of a cantilever oscillating at or near its resonant frequency as it is scanned across the surface of a sample. For high Q factor cantilevers, monitoring the resonant frequency is the preferred method in order to obtain reasonable scan times. This can be done by using a phase-locked-loop (PLL). PLLs can be obtained as commercial integrated circuits, but these do not have the frequency resolution required for SPM. To increase the resolution, all-digital PLLs requiring sophisticated digital signal processors or field programmable gate arrays have also been implemented. We describe here a hybrid analog/digital PLL where most of the components are implemented using discrete analog integrated circuits, but the frequency resolution is provided by a direct digital synthesis chip controlled by a simple peripheral interface controller (PIC) microcontroller. The PLL has excellent frequency resolution and noise, and can be controlled and read by a computer via a universal serial bus connection.

A Phase-Locked Loop Epilepsy Network Emulator

PubMed Central

Watson, P.D.; Horecka, K. M.; Cohen, N.J.; Ratnam, R.

2015-01-01

Most seizure forecasting employs statistical learning techniques that lack a representation of the network interactions that give rise to seizures. We present an epilepsy network emulator (ENE) that uses a network of interconnected phase-locked loops (PLLs) to model synchronous, circuit-level oscillations between electrocorticography (ECoG) electrodes. Using ECoG data from a canine-epilepsy model (Davis et al. 2011) and a physiological entropy measure (approximate entropy or ApEn, Pincus 1995), we demonstrate the entropy of the emulator phases increases dramatically during ictal periods across all ECoG recording sites and across all animals in the sample. Further, this increase precedes the observable voltage spikes that characterize seizure activity in the ECoG data. These results suggest that the ENE is sensitive to phase-domain information in the neural circuits measured by ECoG and that an increase in the entropy of this measure coincides with increasing likelihood of seizure activity. Understanding this unpredictable phase-domain electrical activity present in ECoG recordings may provide a target for seizure detection and feedback control. PMID:26664133

Phase-locked loop design with fast-digital-calibration charge pump

NASA Astrophysics Data System (ADS)

Wang, San-Fu; Hwang, Tsuen-Shiau; Wang, Jhen-Ji

2016-02-01

A fast-digital-calibration technique is proposed for reducing current mismatch in the charge pump (CP) of a phase-locked loop (PLL). The current mismatch in the CP generates fluctuations, which is transferred to the input of voltage-controlled oscillator (VCO). Therefore, the current mismatch increases the reference spur in the PLL. Improving current match of CP will reduce the reference spur and decrease the static phase offset of PLLs. Moreover, the settling time, ripple and power consumption of the PLL are also improved by the proposed technique. This study evaluated a 2.27-2.88 GHz frequency synthesiser fabricated in TSMC 0.18 μm CMOS 1.8 V process. The tuning range of proposed VCO is about 26%. By using the fast-digital-calibration technique, current mismatch is reduced to lower than 0.97%, and the operation range of the proposed CP is between 0.2 and 1.6 V. The proposed PLL has a total power consumption of 22.57 mW and a settling time of 10 μs or less.

Study of Interpolated Timing Recovery Phase-Locked Loop with Linearly Constrained Adaptive Prefilter for Higher-Density Optical Disc

NASA Astrophysics Data System (ADS)

Kajiwara, Yoshiyuki; Shiraishi, Junya; Kobayashi, Shoei; Yamagami, Tamotsu

2009-03-01

A digital phase-locked loop (PLL) with a linearly constrained adaptive filter (LCAF) has been studied for higher-linear-density optical discs. LCAF has been implemented before an interpolated timing recovery (ITR) PLL unit in order to improve the quality of phase error calculation by using an adaptively equalized partial response (PR) signal. Coefficient update of an asynchronous sampled adaptive FIR filter with a least-mean-square (LMS) algorithm has been constrained by a projection matrix in order to suppress the phase shift of the tap coefficients of the adaptive filter. We have developed projection matrices that are suitable for Blu-ray disc (BD) drive systems by numerical simulation. Results have shown the properties of the projection matrices. Then, we have designed the read channel system of the ITR PLL with an LCAF model on the FPGA board for experiments. Results have shown that the LCAF improves the tilt margins of 30 gigabytes (GB) recordable BD (BD-R) and 33 GB BD read-only memory (BD-ROM) with a sufficient LMS adaptation stability.

A closed-loop phase-locked interferometer for wide bandwidth position sensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fleming, Andrew J., E-mail: Andrew.Fleming@Newcastle.edu.au; Routley, Ben S., E-mail: Ben.Routley@Newcastle.edu.au

This article describes a position sensitive interferometer with closed-loop control of the reference mirror. A calibrated nanopositioner is used to lock the interferometer phase to the most sensitive point in the interferogram. In this configuration, large low-frequency movements of the sensor mirror can be detected from the control signal applied to the nanopositioner and high-frequency short-range signals can be measured directly from the photodiode. It is demonstrated that these two signals are complementary and can be summed to find the total displacement. The resulting interferometer has a number of desirable characteristics: it is optically simple, does not require polarization ormore » modulation to detect the direction of motion, does not require fringe-counting or interpolation electronics, and has a bandwidth equal to that of the photodiode. Experimental results demonstrate the frequency response analysis of a high-speed positioning stage. The proposed instrument is ideal for measuring the frequency response of nanopositioners, electro-optical components, MEMs devices, ultrasonic devices, and sensors such as surface acoustic wave detectors.« less

Self-Tuning Adaptive-Controller Using Online Frequency Identification

NASA Technical Reports Server (NTRS)

Chiang, W. W.; Cannon, R. H., Jr.

1985-01-01

A real time adaptive controller was designed and tested successfully on a fourth order laboratory dynamic system which features very low structural damping and a noncolocated actuator sensor pair. The controller, implemented in a digital minicomputer, consists of a state estimator, a set of state feedback gains, and a frequency locked loop (FLL) for real time parameter identification. The FLL can detect the closed loop natural frequency of the system being controlled, calculate the mismatch between a plant parameter and its counterpart in the state estimator, and correct the estimator parameter in real time. The adaptation algorithm can correct the controller error and stabilize the system for more than 50% variation in the plant natural frequency, compared with a 10% stability margin in frequency variation for a fixed gain controller having the same performance at the nominal plant condition. After it has locked to the correct plant frequency, the adaptive controller works as well as the fixed gain controller does when there is no parameter mismatch. The very rapid convergence of this adaptive system is demonstrated experimentally, and can also be proven with simple root locus methods.

A new modem for microwave time synchronisation via geosynchronous telecommunication satellites

NASA Astrophysics Data System (ADS)

Dienert, Michael

1992-06-01

A study illustrating the two way time transfer technique and describing the use of this technique with the MITREX (Microwave Time and Range Experiment) SATRE (Satellite Time and Range Experiment) modems is presented. The two way time transfer technique via geosynchronous telecom satellites is one of the most accurate methods for synchronization and comparison of remote clocks. Most of the unknown propagation delays can be eliminated by the two way principle. The use of a coherent spread spectrum technique with a truncated pseudonoise code offers a resolution better than 30 ps of the measured time interval. The receiver is built around a Delay Locked Loop (DLL), which correlates the received signal with the known PN sequence to derive the control signal of the loop. In the locked state both PN sequences are synchronous and tracking errors of less than 30 ps are possible. Results showing the accuracy of the modem depending on signal to noise ratio and variation of total input power levels are presented and show that the expected improvement of the jitter of the internal delay by an increase of the chip rate is possible.

Word timing recovery in direct detection optical PPM communication systems with avalanche photodiodes using a phase lock loop

NASA Technical Reports Server (NTRS)

Sun, Xiaoli; Davidson, Frederic M.

1990-01-01

A technique for word timing recovery in a direct-detection optical PPM communication system is described. It tracks on back-to-back pulse pairs in the received random PPM data sequences with the use of a phase locked loop. The experimental system consisted of an 833-nm AlGaAs laser diode transmitter and a silicon avalanche photodiode photodetector, and it used Q = 4 PPM signaling at source data rate 25 Mb/s. The mathematical model developed to describe system performance is shown to be in good agreement with the experimental measurements. Use of this recovered PPM word clock with a slot clock recovery system caused no measurable penalty in receiver sensitivity. The completely self-synchronized receiver was capable of acquiring and maintaining both slot and word synchronizations for input optical signal levels as low as 20 average detected photons per information bit. The receiver achieved a bit error probability of 10 to the -6th at less than 60 average detected photons per information bit.

Noise performance of frequency modulation Kelvin force microscopy

PubMed Central

Deresmes, Dominique; Mélin, Thierry

2014-01-01

Summary Noise performance of a phase-locked loop (PLL) based frequency modulation Kelvin force microscope (FM-KFM) is assessed. Noise propagation is modeled step by step throughout the setup using both exact closed loop noise gains and an approximation known as “noise gain” from operational amplifier (OpAmp) design that offers the advantage of decoupling the noise performance study from considerations of stability and ideal loop response. The bandwidth can be chosen depending on how much noise is acceptable and it is shown that stability is not an issue up to a limit that will be discussed. With thermal and detector noise as the only sources, both approaches yield PLL frequency noise expressions equal to the theoretical value for self-oscillating circuits and in agreement with measurement, demonstrating that the PLL components neither modify nor contribute noise. Kelvin output noise is then investigated by modeling the surrounding bias feedback loop. A design rule is proposed that allows choosing the AC modulation frequency for optimized sharing of the PLL bandwidth between Kelvin and topography loops. A crossover criterion determines as a function of bandwidth, temperature and probe parameters whether thermal or detector noise is the dominating noise source. Probe merit factors for both cases are then established, suggesting how to tackle noise performance by probe design. Typical merit factors of common probe types are compared. This comprehensive study is an encouraging step toward a more integral performance assessment and a remedy against focusing on single aspects and optimizing around randomly chosen key values. PMID:24455457

Structural dynamics of the lac repressor-DNA complex revealed by a multiscale simulation.

PubMed

Villa, Elizabeth; Balaeff, Alexander; Schulten, Klaus

2005-05-10

A multiscale simulation of a complex between the lac repressor protein (LacI) and a 107-bp-long DNA segment is reported. The complex between the repressor and two operator DNA segments is described by all-atom molecular dynamics; the size of the simulated system comprises either 226,000 or 314,000 atoms. The DNA loop connecting the operators is modeled as a continuous elastic ribbon, described mathematically by the nonlinear Kirchhoff differential equations with boundary conditions obtained from the coordinates of the terminal base pairs of each operator. The forces stemming from the looped DNA are included in the molecular dynamics simulations; the loop structure and the forces are continuously recomputed because the protein motions during the simulations shift the operators and the presumed termini of the loop. The simulations reveal the structural dynamics of the LacI-DNA complex in unprecedented detail. The multiple domains of LacI exhibit remarkable structural stability during the simulation, moving much like rigid bodies. LacI is shown to absorb the strain from the looped DNA mainly through its mobile DNA-binding head groups. Even with large fluctuating forces applied, the head groups tilt strongly and keep their grip on the operator DNA, while the remainder of the protein retains its V-shaped structure. A simulated opening of the cleft of LacI by 500-pN forces revealed the interactions responsible for locking LacI in the V-conformation.

Digital receiver study and implementation

NASA Technical Reports Server (NTRS)

Fogle, D. A.; Lee, G. M.; Massey, J. C.

1972-01-01

Computer software was developed which makes it possible to use any general purpose computer with A/D conversion capability as a PSK receiver for low data rate telemetry processing. Carrier tracking, bit synchronization, and matched filter detection are all performed digitally. To aid in the implementation of optimum computer processors, a study of general digital processing techniques was performed which emphasized various techniques for digitizing general analog systems. In particular, the phase-locked loop was extensively analyzed as a typical non-linear communication element. Bayesian estimation techniques for PSK demodulation were studied. A hardware implementation of the digital Costas loop was developed.

Method to suppress DDFS spurious signals in a frequency-hopping synthesizer with DDFS-driven PLL architecture.

PubMed

Kwon, Kun-Sup; Yoon, Won-Sang

2010-01-01

In this paper we propose a method of removing from synthesizer output spurious signals due to quasi-amplitude modulation and superposition effect in a frequency-hopping synthesizer with direct digital frequency synthesizer (DDFS)-driven phase-locked loop (PLL) architecture, which has the advantages of high frequency resolution, fast transition time, and small size. There are spurious signals that depend on normalized frequency of DDFS. They can be dominant if they occur within the PLL loop bandwidth. We suggest that such signals can be eliminated by purposefully creating frequency errors in the developed synthesizer.

Performance Analysis of Digital Los Link, Manila Embassy - Santa Rita, Philippines.

DTIC Science & Technology

1981-12-01

Rate = 26 Mbs 17 17 • I, 102 99 PEETANT. HEIGHT AT SNART 505 103 99.99 RECEIVE EN ANTENN HEIGHT AT NL MAS MLMTR w I ,H IHT9 .9 the ratio of the...PF3DB COSGAM 0003031 loop 4O ?SP’ = ’,2 4.?D3F = ’,E12., 000001 C 000001 Dl = Dl /29;) . 0 01 D-7 = 𔃼 52q0.00000 ?STC OSIC* 18. ?1000001 FEE FEE_...and Level II, QPR, transmission and receiving can be accomplished with this model. Design parameters for filters, data rates, phase lock loops (PPL

Receiver performance of laser ranging measurements between the Lunar Observer and a subsatellite for lunar gravity studies

NASA Technical Reports Server (NTRS)

Davidson, Frederic M.; Sun, Xiaoli

1992-01-01

The optimal receiver for a direct detection laser ranging system for slow Doppler frequency shift measurement is shown to consist of a phase tracking loop which can be implemented approximately as a phase lock loop with a 2nd or 3rd order loop filter. The laser transmitter consists of an AlGaAs laser diode at a wavelength of about 800 nm and is intensity modulated by a sinewave. The receiver performance is shown to be limited mainly by the preamplifier thermal noise when a silicon avalanche photodiode is used. A high speed microchannel plate photomultiplier tube is shown to outperform a silicon APD despite its relatively low quantum efficiency at wavelengths near 800 nm. The maximum range between the Lunar Observer and the subsatellite for lunar gravity studies is shown to be about 620 km when using a state-of-the-art silicon APD and about 1000 km when using a microchannel plate photomultiplier tube in order to achieve a relative velocity measurement accuracy of 1 millimeter per second. Other parameters such as the receiver time base jitter and drift also limit performance and have to be considered in the design of an actual system.

A frequency standard via spectrum analysis and direct digital synthesis

NASA Astrophysics Data System (ADS)

Li, Dawei; Shi, Daiting; Hu, Ermeng; Wang, Yigen; Tian, Lu; Zhao, Jianye; Wang, Zhong

2014-11-01

We demonstrated a frequency standard based on a detuned coherent population beating phenomenon. In this phenomenon, the beat frequency of the radio frequency for laser modulation and the hyperfine splitting can be obtained by digital signal processing technology. After analyzing the spectrum of the beat frequency, the fluctuation information is obtained and applied to compensate for the frequency shift to generate the standard frequency by the digital synthesis method. Frequency instability of 2.6 × 1012 at 1000 s is observed in our preliminary experiment. By eliminating the phase-locking loop, the method will enable us to achieve a full-digital frequency standard with remarkable stability.

Power Quality Improvement by Unified Power Quality Conditioner Based on CSC Topology Using Synchronous Reference Frame Theory

PubMed Central

Dharmalingam, Rajasekaran; Dash, Subhransu Sekhar; Senthilnathan, Karthikrajan; Mayilvaganan, Arun Bhaskar; Chinnamuthu, Subramani

2014-01-01

This paper deals with the performance of unified power quality conditioner (UPQC) based on current source converter (CSC) topology. UPQC is used to mitigate the power quality problems like harmonics and sag. The shunt and series active filter performs the simultaneous elimination of current and voltage problems. The power fed is linked through common DC link and maintains constant real power exchange. The DC link is connected through the reactor. The real power supply is given by the photovoltaic system for the compensation of power quality problems. The reference current and voltage generation for shunt and series converter is based on phase locked loop and synchronous reference frame theory. The proposed UPQC-CSC design has superior performance for mitigating the power quality problems. PMID:25013854

Power quality improvement by unified power quality conditioner based on CSC topology using synchronous reference frame theory.

PubMed

Dharmalingam, Rajasekaran; Dash, Subhransu Sekhar; Senthilnathan, Karthikrajan; Mayilvaganan, Arun Bhaskar; Chinnamuthu, Subramani

2014-01-01

This paper deals with the performance of unified power quality conditioner (UPQC) based on current source converter (CSC) topology. UPQC is used to mitigate the power quality problems like harmonics and sag. The shunt and series active filter performs the simultaneous elimination of current and voltage problems. The power fed is linked through common DC link and maintains constant real power exchange. The DC link is connected through the reactor. The real power supply is given by the photovoltaic system for the compensation of power quality problems. The reference current and voltage generation for shunt and series converter is based on phase locked loop and synchronous reference frame theory. The proposed UPQC-CSC design has superior performance for mitigating the power quality problems.

Femtosecond fibre laser stabilisation to an optical frequency standard using a KTP electro-optic crystal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nyushkov, B N; Pivtsov, V S; Koliada, N A

2015-05-31

A miniature intracavity KTP-based electro-optic phase modulator has been developed which can be used for effective stabilisation of an optical frequency comb of a femtosecond erbiumdoped fibre laser to an optical frequency standard. The use of such an electro-optic modulator (EOM) has made it possible to extend the working frequency band of a phase-locked loop system for laser stabilisation to several hundred kilohertz. We demonstrate that the KTP-based EOM is sufficiently sensitive even at a small optical length, which allows it to be readily integrated into cavities of femtosecond fibre lasers with high mode frequency spacings (over 100 MHz). (extrememore » light fields and their applications)« less

Digital data detection and synchronization

NASA Technical Reports Server (NTRS)

Noack, T. L.; Morris, J. F.

1973-01-01

The primary accomplishments have been in the analysis and simulation of receivers and bit synchronizers. It has been discovered that tracking rate effects play, a rather fundamental role in both receiver and synchronizer performance, but that data relating to recorder time-base-error, for the proper characterization of this phenomenon, is in rather short supply. It is possible to obtain operationally useful tape recorder time-base-error data from high signal-to-noise ratio tapes using synchronizers with relatively wideband tracking loops. Low signal-to-noise ratio tapes examined in the same way would not be synchronizable. Additional areas of interest covered are receiver false lock, cycle slipping, and other unusual phenomena, which have been described to some extent in this and earlier reports and simulated during the study.

Double closed-loop control of integrated optical resonance gyroscope with mean-square exponential stability.

PubMed

Li, Hui; Liu, Liying; Lin, Zhili; Wang, Qiwei; Wang, Xiao; Feng, Lishuang

2018-01-22

A new double closed-loop control system with mean-square exponential stability is firstly proposed to optimize the detection accuracy and dynamic response characteristic of the integrated optical resonance gyroscope (IORG). The influence mechanism of optical nonlinear effects on system detection sensitivity is investigated to optimize the demodulation gain, the maximum sensitivity and the linear work region of a gyro system. Especially, we analyze the effect of optical parameter fluctuation on the parameter uncertainty of system, and investigate the influence principle of laser locking-frequency noise on the closed-loop detection accuracy of angular velocity. The stochastic disturbance model of double closed-loop IORG is established that takes the unfavorable factors such as optical effect nonlinearity, disturbed disturbance, optical parameter fluctuation and unavoidable system noise into consideration. A robust control algorithm is also designed to guarantee the mean-square exponential stability of system with a prescribed H ∞ performance in order to improve the detection accuracy and dynamic performance of IORG. The conducted experiment results demonstrate that the IORG has a dynamic response time less than 76us, a long-term bias stability 7.04°/h with an integration time of 10s over one-hour test, and the corresponding bias stability 1.841°/h based on Allan deviation, which validate the effectiveness and usefulness of the proposed detection scheme.

A low noise synthesizer for autotuning and performance testing of hydrogen masers

NASA Technical Reports Server (NTRS)

Cloeren, J. M.; Ingold, J. S.

1984-01-01

A low noise synthesizer has been developed for use in hydrogen maser autotuning and performance evaluation. This synthesizer replaces the frequency offset maser normally used for this purpose and allows the user to maintain all masers in the ensemble at the same frequency. The synthesizer design utilizes a quartz oscillator with a BVA resonator. The oscillator has a frequency offset of 5 X 10 to the minus 8 power. The BVA oscillator is phase-locked to a hydrogen maser by means of a high gain, high stability phase-locked loop, employing low noise multipliers as phase error amplifiers. A functional block diagram of the synthesizer and performance data will be presented.

An automatic tracking system for phase-noise measurement.

PubMed

Yuen, Chung Ming; Tsang, Kim Fung

2005-05-01

A low cost, automatic tracking system for phase noise measurement has been implemented successfully. The tracking system is accomplished by applying a charge pump phase-locked loop as an external reference source to a digital spectrum analyzer. Measurement of a 2.5 GHz, free-running, voltage-controlled oscillator demonstrated the tracking accuracy, thus verifying the feasibility of the system.

Read-out electronics for DC squid magnetic measurements

DOEpatents

Ganther, Jr., Kenneth R.; Snapp, Lowell D.

2002-01-01

Read-out electronics for DC SQUID sensor systems, the read-out electronics incorporating low Johnson noise radio-frequency flux-locked loop circuitry and digital signal processing algorithms in order to improve upon the prior art by a factor of at least ten, thereby alleviating problems caused by magnetic interference when operating DC SQUID sensor systems in magnetically unshielded environments.

Constant frequency pulsed phase-locked loop measuring device

NASA Technical Reports Server (NTRS)

Yost, William T. (Inventor); Kushnick, Peter W. (Inventor); Cantrell, John H. (Inventor)

1993-01-01

A measuring apparatus is presented that uses a fixed frequency oscillator to measure small changes in the phase velocity ultrasonic sound when a sample is exposed to environmental changes such as changes in pressure, temperature, etc. The invention automatically balances electrical phase shifts against the acoustical phase shifts in order to obtain an accurate measurement of electrical phase shifts.

Coherent Optical Adaptive Techniques (COAT)

DTIC Science & Technology

1975-01-01

8217 neceeemry and Identity by block number) Laser Phased Array Adaptive Optics Atmospheric-Turbulence and Thermal Blooming Compensation 20...characteristics of an experimental, visible wavelength, eighteen-element, self-adaptive optical phased array. Measurements on a well-characterized...V LOCAL PHASING ■ LOOP OPTICAL DETECTOR’ LOCAL LOCK / ROOF TOP "^/PROPAGATION’ ^ GLINT ■lm FOCAL LENGTH LENS DETECTOR DMWI rh

Coherent receiver design based on digital signal processing in optical high-speed intersatellite links with M-phase-shift keying

NASA Astrophysics Data System (ADS)

Schaefer, Semjon; Gregory, Mark; Rosenkranz, Werner

2016-11-01

We present simulative and experimental investigations of different coherent receiver designs for high-speed optical intersatellite links. We focus on frequency offset (FO) compensation in homodyne and intradyne detection systems. The considered laser communication terminal uses an optical phase-locked loop (OPLL), which ensures stable homodyne detection. However, the hardware complexity increases with the modulation order. Therefore, we show that software-based intradyne detection is an attractive alternative for OPLL-based homodyne systems. Our approach is based on digital FO and phase noise compensation, in order to achieve a more flexible coherent detection scheme. Analytic results will further show the theoretical impact of the different detection schemes on the receiver sensitivity. Finally, we compare the schemes in terms of bit error ratio measurements and optimal receiver design.

Improvements to a five-phase ABS algorithm for experimental validation

NASA Astrophysics Data System (ADS)

Gerard, Mathieu; Pasillas-Lépine, William; de Vries, Edwin; Verhaegen, Michel

2012-10-01

The anti-lock braking system (ABS) is the most important active safety system for passenger cars. Unfortunately, the literature is not really precise about its description, stability and performance. This research improves a five-phase hybrid ABS control algorithm based on wheel deceleration [W. Pasillas-Lépine, Hybrid modeling and limit cycle analysis for a class of five-phase anti-lock brake algorithms, Veh. Syst. Dyn. 44 (2006), pp. 173-188] and validates it on a tyre-in-the-loop laboratory facility. Five relevant effects are modelled so that the simulation matches the reality: oscillations in measurements, wheel acceleration reconstruction, brake pressure dynamics, brake efficiency changes and tyre relaxation. The time delays in measurement and actuation have been identified as the main difficulty for the initial algorithm to work in practice. Three methods are proposed in order to deal with these delays. It is verified that the ABS limit cycles encircle the optimal braking point, without assuming any tyre parameter being a priori known. The ABS algorithm is compared with the commercial algorithm developed by Bosch.

Mucin-mediated nanocarrier disassembly for triggered uptake of oligonucleotides as a delivery strategy for the potential treatment of mucosal tumours

NASA Astrophysics Data System (ADS)

Martirosyan, A.; Olesen, M. J.; Fenton, R. A.; Kjems, J.; Howard, K. A.

2016-06-01

This work demonstrates gastric mucin-triggered nanocarrier disassembly for release of antisense oligonucleotides and consequent unassisted cellular entry as a novel oral delivery strategy. A fluorescence activation-based reporter system was used to investigate the interaction and mucin-mediated disassembly of chitosan-based nanocarriers containing a 13-mer DNA oligonucleotide with a flanked locked RNA nucleic acid gapmer design. Gastric mucins were shown to trigger gapmer release from nanocarriers that was dependent on the interaction time, mucin concentration and N : P ratio with a maximal release at N : P 10. In contrast to siRNA, naked gapmers exhibited uptake into mucus producing HT-MTX mono-cultures and HT-MTX co-cultured with the carcinoma epithelial cell line Caco-2. Importantly, in vivo gapmer uptake was observed in epithelial tissue 30 min post-injection in murine intestinal loops. The findings present a mucosal design-based system tailored for local delivery of oligonucleotides that may maximize the effectiveness of gene silencing therapeutics within tumours at mucosal sites.This work demonstrates gastric mucin-triggered nanocarrier disassembly for release of antisense oligonucleotides and consequent unassisted cellular entry as a novel oral delivery strategy. A fluorescence activation-based reporter system was used to investigate the interaction and mucin-mediated disassembly of chitosan-based nanocarriers containing a 13-mer DNA oligonucleotide with a flanked locked RNA nucleic acid gapmer design. Gastric mucins were shown to trigger gapmer release from nanocarriers that was dependent on the interaction time, mucin concentration and N : P ratio with a maximal release at N : P 10. In contrast to siRNA, naked gapmers exhibited uptake into mucus producing HT-MTX mono-cultures and HT-MTX co-cultured with the carcinoma epithelial cell line Caco-2. Importantly, in vivo gapmer uptake was observed in epithelial tissue 30 min post-injection in murine intestinal loops. The findings present a mucosal design-based system tailored for local delivery of oligonucleotides that may maximize the effectiveness of gene silencing therapeutics within tumours at mucosal sites. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07206a

Reduction of Phase Ambiguity in an Offset-QPSK Receiver

NASA Technical Reports Server (NTRS)

Berner, Jeff; Kinman, Peter

2004-01-01

Proposed modifications of an offset-quadri-phase-shift keying (offset-QPSK) transmitter and receiver would reduce the amount of signal processing that must be done in the receiver to resolve the QPSK fourfold phase ambiguity. Resolution of the phase ambiguity is necessary in order to synchronize, with the received carrier signal, the signal generated by a local oscillator in a carrier-tracking loop in the receiver. Without resolution of the fourfold phase ambiguity, the loop could lock to any of four possible phase points, only one of which has the proper phase relationship with the carrier. The proposal applies, more specifically, to an offset-QPSK receiver that contains a carrier-tracking loop like that shown in Figure 1. This carrier-tracking loop does not resolve or reduce the phase ambiguity. A carrier-tracking loop of a different design optimized for the reception of offset QPSK could reduce the phase ambiguity from fourfold to twofold, but would be more complex. Alternatively, one could resolve the fourfold phase ambiguity by use of differential coding in the transmitter, at a cost of reduced power efficiency. The proposed modifications would make it possible to reduce the fourfold phase ambiguity to twofold, with no loss in power efficiency and only relatively simple additional signal-processing steps in the transmitter and receiver. The twofold phase ambiguity would then be resolved by use of a unique synchronization word, as is commonly done in binary phase-shift keying (BPSK). Although the mathematical and signal-processing principles underlying the modifications are too complex to explain in detail here, the modifications themselves would be relatively simple and are best described with the help of simple block diagrams (see Figure 2). In the transmitter, one would add a unit that would periodically invert bits going into the QPSK modulator; in the receiver, one would add a unit that would effect different but corresponding inversions of bits coming out of the QPSK demodulator. The net effect of all the inversions would be that depending on which lock point the carrier-tracking loop had selected, all the output bits would be either inverted or non-inverted together; hence, the ambiguity would be reduced from fourfold to twofold, as desired.

Tracking performance and cycle slipping in the all-digital symbol synchronizer loop of the block 5 receiver

NASA Astrophysics Data System (ADS)

Aung, M.

1992-11-01

Computer simulated noise performance of the symbol synchronizer loop (SSL) in the Block 5 receiver is compared with the theoretical noise performance. Good agreement is seen at the higher loop SNR's (SNR(sub L)'s), with gradual degradation as the SNR(sub L) is decreased. For the different cases simulated, cycle slipping is observed (within the simulation time of 10(exp 4) seconds) at SNR(sub L)'s below different thresholds, ranging from 6 to 8.5 dB, comparable to that of a classical phase-locked loop. An important point, however, is that to achieve the desired loop SNR above the seemingly low threshold to avoid cycle slipping, a large data-to-loop-noise power ratio, P(sub D)/(N(sub 0)B(sub L)), is necessary (at least 13 dB larger than the desired SNR(sub L) in the optimum case and larger otherwise). This is due to the large squaring loss (greater than or equal to 13 dB) inherent in the SSL. For the special case of symbol rates approximately equaling the loop update rate, a more accurate equivalent model accounting for an extra loop update period delay (characteristic of the SSL phase detector design) is derived. This model results in a more accurate estimation of the noise-equivalent bandwidth of the loop.

Tracking performance and cycle slipping in the all-digital symbol synchronizer loop of the block 5 receiver

NASA Technical Reports Server (NTRS)

Aung, M.

1992-01-01

Computer simulated noise performance of the symbol synchronizer loop (SSL) in the Block 5 receiver is compared with the theoretical noise performance. Good agreement is seen at the higher loop SNR's (SNR(sub L)'s), with gradual degradation as the SNR(sub L) is decreased. For the different cases simulated, cycle slipping is observed (within the simulation time of 10(exp 4) seconds) at SNR(sub L)'s below different thresholds, ranging from 6 to 8.5 dB, comparable to that of a classical phase-locked loop. An important point, however, is that to achieve the desired loop SNR above the seemingly low threshold to avoid cycle slipping, a large data-to-loop-noise power ratio, P(sub D)/(N(sub 0)B(sub L)), is necessary (at least 13 dB larger than the desired SNR(sub L) in the optimum case and larger otherwise). This is due to the large squaring loss (greater than or equal to 13 dB) inherent in the SSL. For the special case of symbol rates approximately equaling the loop update rate, a more accurate equivalent model accounting for an extra loop update period delay (characteristic of the SSL phase detector design) is derived. This model results in a more accurate estimation of the noise-equivalent bandwidth of the loop.

978-nm square-wave in an all-fiber single-mode ytterbium-doped fiber laser

NASA Astrophysics Data System (ADS)

Li, Shujie; Xu, Lixin; Gu, Chun

2018-01-01

A 978 nm single mode passively mode-locked all-fiber laser delivering square-wave pulses was demonstrated using a figure-8 cavity and a 75 cm commercial double-clad ytterbium-doped fiber. We found the three-level system near 978 nm was able to operate efficiently under clad pumping, simultaneously oscillation around 1030 nm well inhibited. The optimized nonlinear amplifying loop mirror made the mode locking stable and performed the square-pulses shaping. To the best of our knowledge, it is the first time to report the square-wave pulse fiber laser operating at 980 nm. The spectral width of the 978 mode-locked square pulses was about 4 nm, far greater than that of the mode-locked square pulses around 1060 nm reported before, which would be helpful to deeply understand the various square-wave pulses' natures and forming mechanisms. Compared with modulated single-mode or multimode 980 nm LDs, this kind of 980 nm square-wave sources having higher brightness, more steeper rising and falling edge and shorter pulse width, might have potential applications in pumping nanosecond ytterbium or erbium fiber lasers and amplifiers.

Residual and suppressed-carrier arraying techniques for deep-space communications

NASA Technical Reports Server (NTRS)

Shihabi, M.; Shah, B.; Hinedi, S.; Million, S.

1995-01-01

Three techniques that use carrier information from multiple antennas to enhance carrier acquisition and tracking are presented. These techniques in combination with baseband combining are analyzed and simulated for residual and suppressed-carrier modulation. It is shown that the carrier arraying using a single carrier loop technique can acquire and track the carrier even when any single antenna in the array cannot do so by itself. The carrier aiding and carrier arraying using multiple carrier loop techniques, on the other hand, are shown to lock on the carrier only when one of the array elements has sufficient margin to acquire the carrier on its own.

Flexible stator control on the Galileo spacecraft

NASA Technical Reports Server (NTRS)

Kopf, E. H.; Brown, T. K.; Marsh, E. L.

1979-01-01

Galileo is a dual-spin spacecraft designed to deliver a probe to Jupiter and then orbit the planet. The stator, or despun section, contains four flexible modes below 10 Hz and the despun actuator is separated from the inertial sensors by this flexibility. Control loop separation by bandwidth proved unacceptable due to performance requirements. To obtain the desired performance, a control scheme was devised which consists of three parts. First, flexibility damping and control notch filtering are accomplished by phase locked loop techniques. Second, slewing maneuvers are produced by torque profiles which are nonexcitatory to the structure. Finally, a low bandwidth perturbation controller is supplied to remove spacecraft disturbances.

Video-signal improvement using comb filtering techniques.

NASA Technical Reports Server (NTRS)

Arndt, G. D.; Stuber, F. M.; Panneton, R. J.

1973-01-01

Significant improvement in the signal-to-noise performance of television signals has been obtained through the application of comb filtering techniques. This improvement is achieved by removing the inherent redundancy in the television signal through linear prediction and by utilizing the unique noise-rejection characteristics of the receiver comb filter. Theoretical and experimental results describe the signal-to-noise ratio and picture-quality improvement obtained through the use of baseband comb filters and the implementation of a comb network as the loop filter in a phase-lock-loop demodulator. Attention is given to the fact that noise becomes correlated when processed by the receiver comb filter.

Frequency domain phase noise analysis of dual injection-locked optoelectronic oscillators.

PubMed

Jahanbakht, Sajad

2016-10-01

Dual injection-locked optoelectronic oscillators (DIL-OEOs) have been introduced as a means to achieve very low-noise microwave oscillations while avoiding the large spurious peaks that occur in the phase noise of the conventional single-loop OEOs. In these systems, two OEOs are inter-injection locked to each other. The OEO with the longer optical fiber delay line is called the master OEO, and the other is called the slave OEO. Here, a frequency domain approach for simulating the phase noise spectrum of each of the OEOs in a DIL-OEO system and based on the conversion matrix approach is presented. The validity of the new approach is verified by comparing its results with previously published data in the literature. In the new approach, first, in each of the master or slave OEOs, the power spectral densities (PSDs) of two white and 1/f noise sources are optimized such that the resulting simulated phase noise of any of the master or slave OEOs in the free-running state matches the measured phase noise of that OEO. After that, the proposed approach is able to simulate the phase noise PSD of both OEOs at the injection-locked state. Because of the short run-time requirements, especially compared to previously proposed time domain approaches, the new approach is suitable for optimizing the power injection ratios (PIRs), and potentially other circuit parameters, in order to achieve good performance regarding the phase noise in each of the OEOs. Through various numerical simulations, the optimum PIRs for achieving good phase noise performance are presented and discussed; they are in agreement with the previously published results. This further verifies the applicability of the new approach. Moreover, some other interesting results regarding the spur levels are also presented.

Analysis of the PLL phase error in presence of simulated ionospheric scintillation events

NASA Astrophysics Data System (ADS)

Forte, B.

2012-01-01

The functioning of standard phase locked loops (PLL), including those used to track radio signals from Global Navigation Satellite Systems (GNSS), is based on a linear approximation which holds in presence of small phase errors. Such an approximation represents a reasonable assumption in most of the propagation channels. However, in presence of a fading channel the phase error may become large, making the linear approximation no longer valid. The PLL is then expected to operate in a non-linear regime. As PLLs are generally designed and expected to operate in their linear regime, whenever the non-linear regime comes into play, they will experience a serious limitation in their capability to track the corresponding signals. The phase error and the performance of a typical PLL embedded into a commercial multiconstellation GNSS receiver were analyzed in presence of simulated ionospheric scintillation. Large phase errors occurred during scintillation-induced signal fluctuations although cycle slips only occurred during the signal re-acquisition after a loss of lock. Losses of lock occurred whenever the signal faded below the minimumC/N0threshold allowed for tracking. The simulations were performed for different signals (GPS L1C/A, GPS L2C, GPS L5 and Galileo L1). L5 and L2C proved to be weaker than L1. It appeared evident that the conditions driving the PLL phase error in the specific case of GPS receivers in presence of scintillation-induced signal perturbations need to be evaluated in terms of the combination of the minimumC/N0 tracking threshold, lock detector thresholds, possible cycle slips in the tracking PLL and accuracy of the observables (i.e. the error propagation onto the observables stage).

Analytic Determination of Interference Thresholds for Microwave Landing System Equipment and TACAN/DME Equipment

DTIC Science & Technology

1980-08-01

terminals for the PD channel, in dB, at function level tD /U]lL pea^,, desired-to-average undesired signal power at the phase-locked loop for successful...listed belows MS Receiver Reparation Distance (nmI) estimated Altitude Uetwen Desired & Undesired MS (Kilo feet) Grcnd Nquipment 2.1 42 10 142 20) 1q3

9 CFR 75.4 - Interstate movement of equine infectious anemia reactors and approval of laboratories, diagnostic...

Code of Federal Regulations, 2010 CFR

2010-01-01

...: (1) The description, including age, breed, color, sex, and distinctive markings when present (such as... self-locking device on one end and a slot on the other end, which forms a loop when the ends are..., including name, age, sex, breed, color, and markings. Reactor. Any horse, ass, mule, pony or zebra which is...

Characterization of the Nonlinear Elastic Properties of Graphite/Epoxy Composites Using Ultrasound

NASA Technical Reports Server (NTRS)

Prosser, William H.; Green, Robert E., Jr.

1990-01-01

The normalized change in ultrasonic "natural" velocity as a function of stress and temperature was measured in a unidirectional laminate of T300/5208 graphite/epoxy composite using a pulsed phase locked loop ultrasonic interferometer. These measurements were used together with the linear (second order) elastic moduli to calculate some of the nonlinear (third order) moduli of this material.

An Intelligent Hierarchical Decision Architecture for Operational Test and Evaluation

DTIC Science & Technology

1996-05-01

Results .......................................... 60 3.4 CONTRIBUTION...FCM Fuzzy Cognitive Map FMEA Failure Modes and Effects Analysis HWIL Hardware-in-the-Loop IBL Increase in Break Locks xiv IDA Institute for Defense... 60 .5 .40 3 .25 0.21 0.26 Figure 8 PROD-ALL COMMFFY Compositional Method .65 . 7 5 . 60 M 0.67 Figure 9 PROD-MAX COMMFFY Compositional Method 49

Deciphering the structural framework of glycine receptor anchoring by gephyrin

PubMed Central

Kim, Eun Young; Schrader, Nils; Smolinsky, Birthe; Bedet, Cécile; Vannier, Christian; Schwarz, Günter; Schindelin, Hermann

2006-01-01

Glycine is the major inhibitory neurotransmitter in the spinal cord and brain stem. Gephyrin is required to achieve a high concentration of glycine receptors (GlyRs) in the postsynaptic membrane, which is crucial for efficient glycinergic signal transduction. The interaction between gephyrin and the GlyR involves the E-domain of gephyrin and a cytoplasmic loop located between transmembrane segments three and four of the GlyR β subunit. Here, we present crystal structures of the gephyrin E-domain with and without the GlyR β-loop at 2.4 and 2.7 Å resolutions, respectively. The GlyR β-loop is bound in a symmetric ‘key and lock' fashion to each E-domain monomer in a pocket adjacent to the dimer interface. Structure-guided mutagenesis followed by in vitro binding and in vivo colocalization assays demonstrate that a hydrophobic interaction formed by Phe 330 of gephyrin and Phe 398 and Ile 400 of the GlyR β-loop is crucial for binding. PMID:16511563

Self-organized synchronization of digital phase-locked loops with delayed coupling in theory and experiment

PubMed Central

Wetzel, Lucas; Jörg, David J.; Pollakis, Alexandros; Rave, Wolfgang; Fettweis, Gerhard; Jülicher, Frank

2017-01-01

Self-organized synchronization occurs in a variety of natural and technical systems but has so far only attracted limited attention as an engineering principle. In distributed electronic systems, such as antenna arrays and multi-core processors, a common time reference is key to coordinate signal transmission and processing. Here we show how the self-organized synchronization of mutually coupled digital phase-locked loops (DPLLs) can provide robust clocking in large-scale systems. We develop a nonlinear phase description of individual and coupled DPLLs that takes into account filter impulse responses and delayed signal transmission. Our phase model permits analytical expressions for the collective frequencies of synchronized states, the analysis of stability properties and the time scale of synchronization. In particular, we find that signal filtering introduces stability transitions that are not found in systems without filtering. To test our theoretical predictions, we designed and carried out experiments using networks of off-the-shelf DPLL integrated circuitry. We show that the phase model can quantitatively predict the existence, frequency, and stability of synchronized states. Our results demonstrate that mutually delay-coupled DPLLs can provide robust and self-organized synchronous clocking in electronic systems. PMID:28207779

Identification of nonlinear modes using phase-locked-loop experimental continuation and normal form

NASA Astrophysics Data System (ADS)

Denis, V.; Jossic, M.; Giraud-Audine, C.; Chomette, B.; Renault, A.; Thomas, O.

2018-06-01

In this article, we address the model identification of nonlinear vibratory systems, with a specific focus on systems modeled with distributed nonlinearities, such as geometrically nonlinear mechanical structures. The proposed strategy theoretically relies on the concept of nonlinear modes of the underlying conservative unforced system and the use of normal forms. Within this framework, it is shown that without internal resonance, a valid reduced order model for a nonlinear mode is a single Duffing oscillator. We then propose an efficient experimental strategy to measure the backbone curve of a particular nonlinear mode and we use it to identify the free parameters of the reduced order model. The experimental part relies on a Phase-Locked Loop (PLL) and enables a robust and automatic measurement of backbone curves as well as forced responses. It is theoretically and experimentally shown that the PLL is able to stabilize the unstable part of Duffing-like frequency responses, thus enabling its robust experimental measurement. Finally, the whole procedure is tested on three experimental systems: a circular plate, a chinese gong and a piezoelectric cantilever beam. It enable to validate the procedure by comparison to available theoretical models as well as to other experimental identification methods.

Phasemeter core for intersatellite laser heterodyne interferometry: modelling, simulations and experiments

NASA Astrophysics Data System (ADS)

Gerberding, Oliver; Sheard, Benjamin; Bykov, Iouri; Kullmann, Joachim; Esteban Delgado, Juan Jose; Danzmann, Karsten; Heinzel, Gerhard

2013-12-01

Intersatellite laser interferometry is a central component of future space-borne gravity instruments like Laser Interferometer Space Antenna (LISA), evolved LISA, NGO and future geodesy missions. The inherently small laser wavelength allows us to measure distance variations with extremely high precision by interfering a reference beam with a measurement beam. The readout of such interferometers is often based on tracking phasemeters, which are able to measure the phase of an incoming beatnote with high precision over a wide range of frequencies. The implementation of such phasemeters is based on all digital phase-locked loops (ADPLL), hosted in FPGAs. Here, we present a precise model of an ADPLL that allows us to design such a readout algorithm and we support our analysis by numerical performance measurements and experiments with analogue signals.

Method for digital measurement of phase-frequency characteristics for a fixed-length ultrasonic spectrometer

NASA Astrophysics Data System (ADS)

Astashev, M. E.; Belosludtsev, K. N.; Kharakoz, D. P.

2014-05-01

One of the most accurate methods for measuring the compressibility of liquids is resonance measurement of sound velocity in a fixed-length interferometer. This method combines high sensitivity, accuracy, and small sample volume of the test liquid. The measuring principle is to study the resonance properties of a composite resonator that contains a test liquid sample. Ealier, the phase-locked loop (PLL) scheme was used for this. In this paper, we propose an alternative measurement scheme based on digital analysis of harmonic signals, describe the implementation of this scheme using commercially available data acquisition modules, and give examples of test measurements with accuracy evaluations of the results.

A scheme for synchronizing clocks connected by a packet communication network

NASA Astrophysics Data System (ADS)

dos Santos, R. V.; Monteiro, L. H. A.

2012-07-01

Consider a communication system in which a transmitter equipment sends fixed-size packets of data at a uniform rate to a receiver equipment. Consider also that these equipments are connected by a packet-switched network, which introduces a random delay to each packet. Here we propose an adaptive clock recovery scheme able of synchronizing the frequencies and the phases of these devices, within specified limits of precision. This scheme for achieving frequency and phase synchronization is based on measurements of the packet arrival times at the receiver, which are used to control the dynamics of a digital phase-locked loop. The scheme performance is evaluated via numerical simulations performed by using realistic parameter values.

A Single-Photon Avalanche Diode Array for Fluorescence Lifetime Imaging Microscopy.

PubMed

Schwartz, David Eric; Charbon, Edoardo; Shepard, Kenneth L

2008-11-21

We describe the design, characterization, and demonstration of a fully integrated single-photon avalanche diode (SPAD) imager for use in time-resolved fluorescence imaging. The imager consists of a 64-by-64 array of active SPAD pixels and an on-chip time-to-digital converter (TDC) based on a delay-locked loop (DLL) and calibrated interpolators. The imager can perform both standard time-correlated single-photon counting (TCSPC) and an alternative gated-window detection useful for avoiding pulse pile-up when measuring bright signal levels. To illustrate the use of the imager, we present measurements of the decay lifetimes of fluorescent dyes of several types with a timing resolution of 350 ps.

Effect of various features on the life cycle cost of the timing/synchronization subsystem of the DCS digital communications network

NASA Technical Reports Server (NTRS)

Kimsey, D. B.

1978-01-01

The effect on the life cycle cost of the timing subsystem was examined, when these optional features were included in various combinations. The features included mutual control, directed control, double-ended reference links, independence of clock error measurement and correction, phase reference combining, self-organization, smoothing for link and nodal dropouts, unequal reference weightings, and a master in a mutual control network. An overall design of a microprocessor-based timing subsystem was formulated. The microprocessor (8080) implements the digital filter portion of a digital phase locked loop, as well as other control functions such as organization of the network through communication with processors at neighboring nodes.

A Single-Photon Avalanche Diode Array for Fluorescence Lifetime Imaging Microscopy

PubMed Central

Schwartz, David Eric; Charbon, Edoardo; Shepard, Kenneth L.

2013-01-01

We describe the design, characterization, and demonstration of a fully integrated single-photon avalanche diode (SPAD) imager for use in time-resolved fluorescence imaging. The imager consists of a 64-by-64 array of active SPAD pixels and an on-chip time-to-digital converter (TDC) based on a delay-locked loop (DLL) and calibrated interpolators. The imager can perform both standard time-correlated single-photon counting (TCSPC) and an alternative gated-window detection useful for avoiding pulse pile-up when measuring bright signal levels. To illustrate the use of the imager, we present measurements of the decay lifetimes of fluorescent dyes of several types with a timing resolution of 350 ps. PMID:23976789

Piezoelectric MEMS resonators for monitoring grape must fermentation

NASA Astrophysics Data System (ADS)

Toledo, J.; Jiménez-Márquez, F.; Úbeda, J.; Ruiz-Díez, V.; Pfusterschmied, G.; Schmid, U.; Sánchez-Rojas, J. L.

2016-10-01

The traditional procedure followed by winemakers for monitoring grape must fermentation is not automated, has not enough accuracy or has only been tested in discrete must samples. In order to contribute to the automation and improvement of the wine fermentation process, we have designed an AlN-based piezoelectric microresonator, serving as a density sensor and being excited in the 4th-order roof tile-shaped vibration mode. Furthermore, conditioning circuits were designed to convert the one-port impedance of the resonator into a resonant two-port transfer function. This allowed us to design a Phase Locked Loop-based oscillator circuit, implemented with a commercial lock-in amplifier with an oscillation frequency determined by the vibrating mode. We were capable of measuring the fermentation kinetics by both tracking the resonance frequency and by determining the quality factor measurements of the microresonator. Moreover, the resonator was calibrated with an artificial model solution of grape must and then applied for the monitoring of real grape must fermentation. Our results demonstrate the high potential of MEMS resonators to detect the decrease in sugar and the increase in ethanol concentrations during the grape must fermentation with a resolution of 100 μg/ml and a sensitivity of 0.16 Hz/μg/ml as upper limits.

Noise in NC-AFM measurements with significant tip–sample interaction

PubMed Central

Lübbe, Jannis; Temmen, Matthias

2016-01-01

The frequency shift noise in non-contact atomic force microscopy (NC-AFM) imaging and spectroscopy consists of thermal noise and detection system noise with an additional contribution from amplitude noise if there are significant tip–sample interactions. The total noise power spectral density D Δ f(f m) is, however, not just the sum of these noise contributions. Instead its magnitude and spectral characteristics are determined by the strongly non-linear tip–sample interaction, by the coupling between the amplitude and tip–sample distance control loops of the NC-AFM system as well as by the characteristics of the phase locked loop (PLL) detector used for frequency demodulation. Here, we measure D Δ f(f m) for various NC-AFM parameter settings representing realistic measurement conditions and compare experimental data to simulations based on a model of the NC-AFM system that includes the tip–sample interaction. The good agreement between predicted and measured noise spectra confirms that the model covers the relevant noise contributions and interactions. Results yield a general understanding of noise generation and propagation in the NC-AFM and provide a quantitative prediction of noise for given experimental parameters. We derive strategies for noise-optimised imaging and spectroscopy and outline a full optimisation procedure for the instrumentation and control loops. PMID:28144538

Noise in NC-AFM measurements with significant tip-sample interaction.

PubMed

Lübbe, Jannis; Temmen, Matthias; Rahe, Philipp; Reichling, Michael

2016-01-01

The frequency shift noise in non-contact atomic force microscopy (NC-AFM) imaging and spectroscopy consists of thermal noise and detection system noise with an additional contribution from amplitude noise if there are significant tip-sample interactions. The total noise power spectral density D Δ f ( f m ) is, however, not just the sum of these noise contributions. Instead its magnitude and spectral characteristics are determined by the strongly non-linear tip-sample interaction, by the coupling between the amplitude and tip-sample distance control loops of the NC-AFM system as well as by the characteristics of the phase locked loop (PLL) detector used for frequency demodulation. Here, we measure D Δ f ( f m ) for various NC-AFM parameter settings representing realistic measurement conditions and compare experimental data to simulations based on a model of the NC-AFM system that includes the tip-sample interaction. The good agreement between predicted and measured noise spectra confirms that the model covers the relevant noise contributions and interactions. Results yield a general understanding of noise generation and propagation in the NC-AFM and provide a quantitative prediction of noise for given experimental parameters. We derive strategies for noise-optimised imaging and spectroscopy and outline a full optimisation procedure for the instrumentation and control loops.

Design and implementation of a micromechanical silicon resonant accelerometer.

PubMed

Huang, Libin; Yang, Hui; Gao, Yang; Zhao, Liye; Liang, Jinxing

2013-11-19

The micromechanical silicon resonant accelerometer has attracted considerable attention in the research and development of high-precision MEMS accelerometers because of its output of quasi-digital signals, high sensitivity, high resolution, wide dynamic range, anti-interference capacity and good stability. Because of the mismatching thermal expansion coefficients of silicon and glass, the micromechanical silicon resonant accelerometer based on the Silicon on Glass (SOG) technique is deeply affected by the temperature during the fabrication, packaging and use processes. The thermal stress caused by temperature changes directly affects the frequency output of the accelerometer. Based on the working principle of the micromechanical resonant accelerometer, a special accelerometer structure that reduces the temperature influence on the accelerometer is designed. The accelerometer can greatly reduce the thermal stress caused by high temperatures in the process of fabrication and packaging. Currently, the closed-loop drive circuit is devised based on a phase-locked loop. The unloaded resonant frequencies of the prototype of the micromechanical silicon resonant accelerometer are approximately 31.4 kHz and 31.5 kHz. The scale factor is 66.24003 Hz/g. The scale factor stability is 14.886 ppm, the scale factor repeatability is 23 ppm, the bias stability is 23 μg, the bias repeatability is 170 μg, and the bias temperature coefficient is 0.0734 Hz/°C.

Dissecting the hybridization of oligonucleotides to structured complementary sequences.

PubMed

Peracchi, Alessio

2016-06-01

When oligonucleotides hybridize to long target molecules, the process is slowed by the secondary structure in the targets. The phenomenon has been analyzed in several previous studies, but many details remain poorly understood. I used a spectrofluorometric strategy, focusing on the formation/breaking of individual base pairs, to study the kinetics of association between a DNA hairpin and >20 complementary oligonucleotides ('antisenses'). Hybridization rates differed by over three orders of magnitude. Association was toehold-mediated, both for antisenses binding to the target's ends and for those designed to interact with the loop. Binding of these latter, besides being consistently slower, was affected to variable, non-uniform extents by the asymmetric loop structure. Divalent metal ions accelerated hybridization, more pronouncedly when nucleation occurred at the loop. Incorporation of locked nucleic acid (LNA) residues in the antisenses substantially improved the kinetics only when LNAs participated to the earliest hybridization steps. The effects of individual LNAs placed along the antisense indicated that the reaction transition state occurred after invading at least the first base pair of the stem. The experimental approach helps dissect hybridization reactions involving structured nucleic acids. Toehold-dependent, nucleation-invasion models appear fully appropriate for describing such reactions. Estimating the stability of nucleation complexes formed at internal toeholds is the major hurdle for the quantitative prediction of hybridization rates. While analyzing the mechanisms of a fundamental biochemical process (hybridization), this work also provides suggestions for the improvement of technologies that rely on such process. Copyright © 2016 Elsevier B.V. All rights reserved.

Optical frequency stabilization in infrared region using improved dual feed-back loop

NASA Astrophysics Data System (ADS)

Ružička, B.; Číp, O.; Lazar, J.

2007-03-01

Modern technologies such as DWDM (Dense Wavelength Division Multiplex) need precise stability of laser frequencies. According to this fact, requirements of new etalons of optical frequencies in the telecommunication band is rapidly growing. Lasers working in near infrared telecommunication band (1500-1600 nm) can be stabilized to 12C IIH II or 13C IIH II (acetylene) gas absorption lines. The acetylene gas absorption has been widely studied and accepted by international bodies of standardization as a primary wavelength reference in the near infrared band around 1550 nm. Our aim was to design and develop a compact fibre optics laser system generating coherent light in near-IR band with high frequency stability (at least 1.10 -8). This system should become a base for realization of a primary frequency standard for optical communications in the Czech Republic. Such an etalon will be needed for calibration of wavelengthmeters and spectral analysers for DWDM communication systems. We are co-operating with CMI (Czech Metrology Institute) on this project. We present stabilized laser system based on a single frequency DFB (Distributed Feedback) laser diode with a narrow spectral profile. The laser is pre-stabilized by means of the FM-spectroscopy on a passive resonator. Thanks to a fast feed-back loop we are able to improve spectral characteristics of the laser. The laser frequency is locked by a relatively slow second feed-back loop on an absorption line of acetylene vapour which is sealed in a cell under the optimised pressure.

[Study on a wireless energy transmission system for the noninvasive examination micro system inside alimentary tracts].

PubMed

He, Xiu; Yan, Guo-Zheng; Wang, Fu-Min

2008-01-01

A wireless energy transmission system for the MEMS system inside alimentary tracts is reported here in the paper. It consists of an automatic frequency tracking circuit of phase lock loop and phase shift PWM control circuit. Experimental results show that the energy transmission system is capable of automatic frequency-tracking and transmission power-adjusting and has stable received energy.

Initial flight test of a Loran-C receiver/data collection system

NASA Technical Reports Server (NTRS)

Fischer, J. P.; Nickum, J. D.

1978-01-01

Development of a low cost Loran C receiver for general aviation use is discussed. The preparation and procedure of a flight test conducted with a receiver design which utilizes a phase locked loop oscillator to track the Loran C signals is described. It is indicated that such a receiver is a viable alternative for future work in developing a low cost Loran-C navigator.

Ultra-Stable Oscillators for Probe Radio Science Investigations

NASA Technical Reports Server (NTRS)

Asmar, Sami

2012-01-01

An Ultra-Stable Oscillator (USO) is: A frequency reference, and A clock It is stable, small, and sensitive. It is a science and an art form. It is flown on spacecraft/probes. It]is utilized at ground stations alone or as a cleanup loop. It eliminates lock-up time on uplink for occultation egress & effect of media on uplink signal. It has enabled significant planetary science investigations.

Learning the Art of Electronics

NASA Astrophysics Data System (ADS)

Hayes, Thomas C.; Horowitz, Paul

2016-03-01

1. DC circuits; 2. RC circuits; 3. Diode circuits; 4. Transistors I; 5. Transistors II; 6. Operational amplifiers I; 7. Operational amplifiers II: nice positive feedback; 8. Operational amplifiers III; 9. Operational amplifiers IV: nasty positive feedback; 10. Operational amplifiers V: PID motor control loop; 11. Voltage regulators; 12. MOSFET switches; 13. Group audio project; 14. Logic gates; 15. Logic compilers, sequential circuits, flip-flops; 16. Counters; 17. Memory: state machines; 18. Analog to digital: phase-locked loop; 19. Microcontrollers and microprocessors I: processor/controller; 20. I/O, first assembly language; 21. Bit operations; 22. Interrupt: ADC and DAC; 23. Moving pointers, serial buses; 24. Dallas Standalone Micro, SiLabs SPI RAM; 25. Toys in the attic; Appendices; Index.

Rapid algorithm prototyping and implementation for power quality measurement

NASA Astrophysics Data System (ADS)

Kołek, Krzysztof; Piątek, Krzysztof

2015-12-01

This article presents a Model-Based Design (MBD) approach to rapidly implement power quality (PQ) metering algorithms. Power supply quality is a very important aspect of modern power systems and will become even more important in future smart grids. In this case, maintaining the PQ parameters at the desired level will require efficient implementation methods of the metering algorithms. Currently, the development of new, advanced PQ metering algorithms requires new hardware with adequate computational capability and time intensive, cost-ineffective manual implementations. An alternative, considered here, is an MBD approach. The MBD approach focuses on the modelling and validation of the model by simulation, which is well-supported by a Computer-Aided Engineering (CAE) packages. This paper presents two algorithms utilized in modern PQ meters: a phase-locked loop based on an Enhanced Phase Locked Loop (EPLL), and the flicker measurement according to the IEC 61000-4-15 standard. The algorithms were chosen because of their complexity and non-trivial development. They were first modelled in the MATLAB/Simulink package, then tested and validated in a simulation environment. The models, in the form of Simulink diagrams, were next used to automatically generate C code. The code was compiled and executed in real-time on the Zynq Xilinx platform that combines a reconfigurable Field Programmable Gate Array (FPGA) with a dual-core processor. The MBD development of PQ algorithms, automatic code generation, and compilation form a rapid algorithm prototyping and implementation path for PQ measurements. The main advantage of this approach is the ability to focus on the design, validation, and testing stages while skipping over implementation issues. The code generation process renders production-ready code that can be easily used on the target hardware. This is especially important when standards for PQ measurement are in constant development, and the PQ issues in emerging smart grids will require tools for rapid development and implementation of such algorithms.

A miniaturized digital telemetry system for physiological data transmission

NASA Technical Reports Server (NTRS)

Portnoy, W. M.; Stotts, L. J.

1978-01-01

A physiological date telemetry system, consisting basically of a portable unit and a ground base station was designed, built, and tested. The portable unit to be worn by the subject is composed of a single crystal controlled transmitter with AM transmission of digital data and narrowband FM transmission of voice; a crystal controlled FM receiver; thirteen input channels follwed by a PCM encoder (three of these channels are designed for ECG data); a calibration unit; and a transponder control system. The ground base station consists of a standard telemetry reciever, a decoder, and an FM transmitter for transmission of voice and transponder signals to the portable unit. The ground base station has complete control of power to all subsystems in the portable unit. The phase-locked loop circuit which is used to decode the data, remains in operation even when the signal from the portable unit is interrupted.

Proline Restricts Loop I Conformation of the High Affinity WW Domain from Human Nedd4-1 to a Ligand Binding-Competent Type I β-Turn.

PubMed

Schulte, Marianne; Panwalkar, Vineet; Freischem, Stefan; Willbold, Dieter; Dingley, Andrew J

2018-04-19

Sequence alignment of the four WW domains from human Nedd4-1 (neuronal precursor cell expressed developmentally down-regulated gene 4-1) reveals that the highest sequence diversity exists in loop I. Three residues in this type I β-turn interact with the PPxY motif of the human epithelial Na + channel (hENaC) subunits, indicating that peptide affinity is defined by the loop I sequence. The third WW domain (WW3*) has the highest ligand affinity and unlike the other three hNedd4-1 WW domains or other WW domains studied contains the highly statistically preferred proline at the ( i + 1) position found in β-turns. In this report, molecular dynamics simulations and experimental data were combined to characterize loop I stability and dynamics. Exchange of the proline to the equivalent residue in WW4 (Thr) results in the presence of a predominantly open seven residue Ω loop rather than the type I β-turn conformation for the wild-type apo-WW3*. In the presence of the ligand, the structure of the mutated loop I is locked into a type I β-turn. Thus, proline in loop I ensures a stable peptide binding-competent β-turn conformation, indicating that amino acid sequence modulates local flexibility to tune binding preferences and stability of dynamic interaction motifs.

Small-Signal Dynamic Analysis of LCC-HVDC with STATCOM at the Inverter Busbar

NASA Astrophysics Data System (ADS)

Liu, Dong; Jiang, Wen; Guo, Chunyi; Rehman, Atiq Ur; Zhao, Chengyong

2018-01-01

This paper develops a linearized small-signal dynamic model of a Line-Commutated-Converter based HVDC (LCC-HVDC) system with STATCOM at the inverter busbar, and validates its accuracy by comparing time-domain responses from small-signal model and PSCAD-based simulation results. Considering the potential impact of Phase-Locked-Loop (PLL) parameters on the study system and the close connection of STATCOM and LCC inverter station at AC busbar, this paper investigates the impact of PLL gains and AC voltage control parameters of STATCOM on the system small-signal stability. The studies show that (i) the PLL gain has highly impact on the study system and smaller PLL gains are preferable; (ii) larger values of both the proportional gain and the integral gain of AC voltage controller of STATCOM could result in oscillation/instability of the system.

Digitally controlled chirped pulse laser for sub-terahertz-range fiber structure interrogation.

PubMed

Chen, Zhen; Hefferman, Gerald; Wei, Tao

2017-03-01

This Letter reports a sweep velocity-locked laser pulse generator controlled using a digital phase-locked loop (DPLL) circuit. This design is used for the interrogation of sub-terahertz-range fiber structures for sensing applications that require real-time data collection with millimeter-level spatial resolution. A distributed feedback laser was employed to generate chirped laser pulses via injection current modulation. A DPLL circuit was developed to lock the optical frequency sweep velocity. A high-quality linearly chirped laser pulse with a frequency excursion of 117.69 GHz at an optical communication band was demonstrated. The system was further adopted to interrogate a continuously distributed sub-terahertz-range fiber structure (sub-THz-fs) for sensing applications. A strain test was conducted in which the sub-THz-fs showed a linear response to longitudinal strain change with predicted sensitivity. Additionally, temperature testing was conducted in which a heat source was used to generate a temperature distribution along the fiber structure to demonstrate its distributed sensing capability. A Gaussian temperature profile was measured using the described system and tracked in real time, as the heat source was moved.

Allosteric mechanism controls traffic in the chaperone/usher pathway.

PubMed

Di Yu, Xiao; Dubnovitsky, Anatoly; Pudney, Alex F; Macintyre, Sheila; Knight, Stefan D; Zavialov, Anton V

2012-11-07

Many virulence organelles of Gram-negative bacterial pathogens are assembled via the chaperone/usher pathway. The chaperone transports organelle subunits across the periplasm to the outer membrane usher, where they are released and incorporated into growing fibers. Here, we elucidate the mechanism of the usher-targeting step in assembly of the Yersinia pestis F1 capsule at the atomic level. The usher interacts almost exclusively with the chaperone in the chaperone:subunit complex. In free chaperone, a pair of conserved proline residues at the beginning of the subunit-binding loop form a "proline lock" that occludes the usher-binding surface and blocks usher binding. Binding of the subunit to the chaperone rotates the proline lock away from the usher-binding surface, allowing the chaperone-subunit complex to bind to the usher. We show that the proline lock exists in other chaperone/usher systems and represents a general allosteric mechanism for selective targeting of chaperone:subunit complexes to the usher and for release and recycling of the free chaperone. Copyright © 2012 Elsevier Ltd. All rights reserved.

Grid Integration of Single Stage Solar PV System using Three-level Voltage Source Converter

NASA Astrophysics Data System (ADS)

Hussain, Ikhlaq; Kandpal, Maulik; Singh, Bhim

2016-08-01

This paper presents a single stage solar PV (photovoltaic) grid integrated power generating system using a three level voltage source converter (VSC) operating at low switching frequency of 900 Hz with robust synchronizing phase locked loop (RS-PLL) based control algorithm. To track the maximum power from solar PV array, an incremental conductance algorithm is used and this maximum power is fed to the grid via three-level VSC. The use of single stage system with three level VSC offers the advantage of low switching losses and the operation at high voltages and high power which results in enhancement of power quality in the proposed system. Simulated results validate the design and control algorithm under steady state and dynamic conditions.

Coordinated design of coding and modulation systems

NASA Technical Reports Server (NTRS)

Massey, J. L.

1976-01-01

Work on partial unit memory codes continued; it was shown that for a given virtual state complexity, the maximum free distance over the class of all convolutional codes is achieved within the class of unit memory codes. The effect of phase-lock loop (PLL) tracking error on coding system performance was studied by using the channel cut-off rate as the measure of quality of a modulation system. Optimum modulation signal sets for a non-white Gaussian channel considered an heuristic selection rule based on a water-filling argument. The use of error correcting codes to perform data compression by the technique of syndrome source coding was researched and a weight-and-error-locations scheme was developed that is closely related to LDSC coding.

Performance analysis of an all-digital BPSK direct sequence spread-spectrum IF receiver architecture

NASA Astrophysics Data System (ADS)

Chung, Bong-Young; Chien, Charles; Samueli, Henry; Jain, Rajeev

1993-09-01

A VLSI architecture for an all-digital binary phase shift keyed (BPSK) direct-sequence (DS) spread spectrum (SS) IF receiver is presented, and an in-depth performance analysis is given. The all-digital architecture incorporates a Costar loop for carrier recovery and a delay-locked loop for clock recovery. For the PN acquisition block, a robust energy detection scheme is proposed to reduce false PN locks over a broad range of signal-to-noise ratios. The proposed architecture is intended for use in the 902-928 MHz unlicensed spread spectrum radio band. A 100 kbs information rate and a 12.7 Mchips/second PN code rate are assumed. The IF center frequency is 12.7 MHz and the IF sampling rate is 50.8 Msamples/ second, which is the Nyquist rate for the 25.4 MHz bandwidth signal. Finite wordlength effects have been simulated to optimize the architecture, thereby minimizing the chip area, and results of the finite wordlength simulations demonstrate that the chip architecture achieves a bit error rate performance within 1 dB of theory in an additive white Gaussian noise channel. The probability of PN acquisition within 5 ms is approximately 56% at -17 dB IF input SNR and 82% at -11 dB IF input SNR.

Modular high-voltage bias generator powered by dual-looped self-adaptive wireless power transmission.

PubMed

Xie, Kai; Huang, An-Feng; Li, Xiao-Ping; Guo, Shi-Zhong; Zhang, Han-Lu

2015-04-01

We proposed a modular high-voltage (HV) bias generator powered by a novel transmitter-sharing inductive coupled wireless power transmission technology, aimed to extend the generator's flexibility and configurability. To solve the problems caused through an uncertain number of modules, a dual-looped self-adaptive control method is proposed that is capable of tracking resonance frequency while maintaining a relatively stable induction voltage for each HV module. The method combines a phase-locked loop and a current feedback loop, which ensures an accurate resonance state and a relatively constant boost ratio for each module, simplifying the architecture of the boost stage and improving the total efficiency. The prototype was built and tested. The input voltage drop of each module is less than 14% if the module number varies from 3 to 10; resonance tracking is completed within 60 ms. The efficiency of the coupling structure reaches up to 95%, whereas the total efficiency approaches 73% for a rated output. Furthermore, this technology can be used in various multi-load wireless power supply applications.

Passive Optical Locking Techniques for Diode Lasers

NASA Astrophysics Data System (ADS)

Zhang, Quan

1995-01-01

Most current diode-based nonlinear frequency converters utilize electronic frequency locking techniques. However, this type of locking technique typically involves very complex electronics, and suffers the 'power-drop' problem. This dissertation is devoted to the development of an all-optical passive locking technique that locks the diode laser frequency to the external cavity resonance stably without using any kind of electronic servo. The amplitude noise problem associated with the strong optical locking has been studied. Single-mode operation of a passively locked single-stripe diode with an amplitude stability better than 1% has been achieved. This passive optical locking technique applies to broad-area diodes as well as single-stripe diodes, and can be easily used to generate blue light. A schematic of a milliwatt level blue laser based on the single-stripe diode locking technique has been proposed. A 120 mW 467 nm blue laser has been built using the tapered amplifier locking technique. In addition to diode-based blue lasers, this passive locking technique has applications in nonlinear frequency conversions, resonant spectroscopy, particle counter devices, telecommunications, and medical devices.

A Fabry-Pérot electro-optic sensing system using a drive-current-tuned wavelength laser diode.

PubMed

Kuo, Wen-Kai; Wu, Pei-Yu; Lee, Chang-Ching

2010-05-01

A Fabry-Pérot enhanced electro-optic sensing system that utilizes a drive-current-tuned wavelength laser diode is presented. An electro-optic prober made of LiNbO(3) crystal with an asymmetric Fabry-Pérot cavity is used in this system. To lock the wavelength of the laser diode at resonant condition, a closed-loop power control scheme is proposed. Experiment results show that the system can keep the electro-optic prober at high sensitivity for a long working time when the closed-loop control function is on. If this function is off, the sensitivity may be fluctuated and only one-third of the best level in the worst case.

A compact ADPLL based on symmetrical binary frequency searching with the same circuit

NASA Astrophysics Data System (ADS)

Li, Hangbiao; Zhang, Bo; Luo, Ping; Liao, Pengfei; Liu, Junjie; Li, Zhaoji

2015-03-01

A compact all-digital phase-locked loop (C-ADPLL) based on symmetrical binary frequency searching (BFS) with the same circuit is presented in this paper. The minimising relative frequency variation error Δη (MFE) rule is derived as guidance of design and is used to weigh the accuracy of the digitally controlled oscillator (DCO) clock frequency. The symmetrical BFS is used in the coarse-tuning process and the fine-tuning process of DCO clock frequency to achieve the minimum Δη of the locked DCO clock, which simplifies the circuit architecture and saves the die area. The C-ADPLL is implemented in a 0.13 μm one-poly-eight-metal (1P8M) CMOS process and the on-chip area is only 0.043 mm2, which is much smaller. The measurement results show that the peak-to-peak (Pk-Pk) jitter and the root-mean-square jitter of the DCO clock frequency are 270 ps at 72.3 MHz and 42 ps at 79.4 MHz, respectively, while the power consumption of the proposed ADPLL is only 2.7 mW (at 115.8 MHz) with a 1.2 V power supply. The measured Δη is not more than 1.14%. Compared with other ADPLLs, the proposed C-ADPLL has simpler architecture, smaller size and lower Pk-Pk jitter.

42.8 Gb/s ASK homodyne receiver using standard DFB lasers

NASA Astrophysics Data System (ADS)

Becker, D.; Mohr, D.; Datta, S.; Wree, C.; Bhandare, S.; Joshi, A.

2009-05-01

Optical synchronous coherent detection is attracting greater attention within the defense and security community because it allows linear recovery both of the amplitude and phase of optical signals. Fiber-based transmission impairments such as chromatic dispersion and polarization mode dispersion can be compensated in the electrical domain. Additionally, synchronous detection offers the potential of improved receiver sensitivity and extended reach versus direct or interferometric detection schemes. 28 Gbaud/112 Gb/s and 42.8 Gbaud transmissions are now being considered in fiber networks worldwide. Due to the lack of broadband high frequency components centered at IF values of 56 GHz and 86 GHz, respectively, the coherent heterodyne approach is not viable for these baud rates. The homodyne approach remains one of the choices available to fully exploit the advantages of synchronous coherent detection at these transmission data rates. In order to implement the homodyne receiver, optical phase locking between the signal and local oscillator laser (LO) is required. Digital approaches for this task rely upon very complex, fast, and high power-consumption chips. A homodyne receiver using an analog approach for phase locking would allow for increased system simplicity at a lower cost. Use of commercial-off-the-shelf (COTS) DFB lasers embedded within the receiver would also increase system feasibility for defense applications. We demonstrate synchronous demodulation of a 42.8 Gbaud signal using an analog optical phase-locked loop. The homodyne system was optimized to use COTS DFB lasers having an aggregate linewidth of ~2 MHz. We also analyze the impact of uncompensated phase noise on receiver performance.

Atomic clocks based on extened-cavity diode laser in multimode operation

NASA Astrophysics Data System (ADS)

Yim, Sin; Cho, D.

2011-05-01

We demonstrated the possibilities to develope an atomic clock based on coherent population trapping (CPT) without using a local oscillator and a modulator. Instead of using a modulator, we use two modes from a single extended-cavity diode laser in multimode operation. Two different types of feedback system are applied to stabilize a difference frequency between the two modes and eliminate the need for an extra frequency modulation. In the first type, we employ an electronic feedback using dispersion of the CPT resonance as an error signal. The two modes are phase locked with reference to a dispersion signal from a CPT resonance of 85Rb at 3.036 GHz ground hyperfine splitting. We use D1 transition at 794.8 nm with lin ⊥lin polarizations to obtain large-contrast CPT signal. Allan deviation of the beat frequency between the two modes is 1 ×10-10 at 200-s integration time. In the second type, we employ optoelectronic feedback to construct an opto-electronic oscillator (OEO). In an OEO, the beating signal between two modes is recovered by a fast photodiode, and its output is amplified and fed back to the laser diode by using a direct modulation of an injection current. When the OEO loop is closed, oscillation frequency depends on variations of the loop length. In order to stabilize an OEO loop length and thereby its oscillation frequency, CPT cell is inserted to play a role of microwave band pass filter. Allan deviation of the CPT-stabilized OEO is 2 ×10-10 at 100-s integration time.

Method of recertifying a loaded bearing member

NASA Technical Reports Server (NTRS)

Allison, Sidney G. (Inventor)

1992-01-01

A method is described of recertifying a loaded bearing member using ultrasound testing to compensate for different equipment configurations and temperature conditions. The standard frequency F1 of a reference block is determined via an ultrasonic tone burst generated by a first pulsed phased locked loop (P2L2) equipment configuration. Once a lock point number S is determined for F1, the reference frequency F1a of the reference block is determined at this lock point number via a second P2L2 equipment configuration to permit an equipment offset compensation factor Fo1=((F1-F1a)/F1)(1000000) to be determined. Next, a reference frequency F2 of the unloaded bearing member is determined using a second P2L2 equipment configuration and is then compensated for equipment offset errors via the relationship F2+F2(Fo1)/1000000. A lock point number b is also determined for F2. A resonant frequency F3 is determined for the reference block using a third P2L2 equipment configuration to determine a second offset compensation factor F02=((F1-F3)/F1) 1000000. Next the resonant frequency F4 of the loaded bearing member is measured at lock point number b via the third P2L2 equipment configuration and the bolt load determined by the relationship (-1000000)CI(((F2-F4)/F2)-Fo2), wherein CI is a factor correlating measured frequency shift to the applied load. Temperature compensation is also performed at each point in the process.

Frequency offset locking of AlGaAs semiconductor lasers

NASA Astrophysics Data System (ADS)

Kuboki, Katsuhiko; Ohtsu, Motoichi

1987-04-01

Frequency offset locking is proposed as a technique for tracking and sweeping of a semiconductor laser frequency to improve temporal coherence in semiconductor lasers. Experiments were carried out in which a frequency stabilized laser (of residual frequency fluctuation value of 140 Hz at the integration time between 100 ms and 100 s) was used as a master laser, using a digital phase comparator of a large dynamic range (2 pi x 10 to the 11th rad) in the feedback loop to reduce the phase fluctuations of the beat signal between the master laser and the slave laser. As a result, residual frequency fluctuations of the beat signal were as low as 11 Hz at the integration time of 100 s (i.e., the residual frequency fluctuations of the slave laser were almost equal to those of the master laser).