Effects of ICRF power on SOL density profiles and LH coupling during simultaneous LH and ICRF operation on Alcator C-Mod

NASA Astrophysics Data System (ADS)

Lau, C.; Lin, Y.; Wallace, G.; Wukitch, S. J.; Hanson, G. R.; Labombard, B.; Ochoukov, R.; Shiraiwa, S.; Terry, J.

2013-09-01

A dedicated experiment during simultaneous lower hybrid (LH) and ion cyclotron range-of-frequencies (ICRF) operations is carried out to evaluate and understand the effects of ICRF power on the scrape-off-layer (SOL) density profiles and on the resultant LH coupling for a wide range of plasma parameters on Alcator C-Mod. Operation of the LH launcher with the adjacent ICRF antenna significantly degrades LH coupling while operation with the ICRF antenna that is not magnetically connected to the LH launcher minimally affects LH coupling. An X-mode reflectometer system at three poloidal locations adjacent to the LH launcher and a visible video camera imaging the LH launcher are used to measure local SOL density profile and emissivity modifications with the application of LH and LH + ICRF power. These measurements confirm that the density in front of the LH launcher depends strongly on the magnetic field line mapping of the active ICRF antenna. Reflectometer measurements also observe both ICRF-driven and LH-driven poloidal density profile asymmetries, especially a strong density depletion at certain poloidal locations in front of the LH launcher during operation with a magnetically connected ICRF antenna. The results indicate that understanding both LH-driven flows and ICRF sheath driven flows may be necessary to understand the observed density profile modifications and LH coupling results during simultaneous LH + ICRF operation.

Theory and Practice in ICRF Antennas for Long Pulse Operation

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

Colas, L.; Bremond, S.; Mitteau, R.

2005-09-26

Long plasma discharges on the Tore Supra (TS) tokamak were extended in 2004 towards higher powers and plasma densities by combined Lower Hybrid (LH) and Ion Cyclotron Range of Frequencies (ICRF) waves. RF pulses of 20sx8MW and 60sx4MW were produced. TS is equipped with 3 ICRF antennas, whose front faces are ready for CW operation. This paper reports on their behaviour over high power long pulses, as observed with infrared (IR) thermography and calorimetric measurements. Edge parasitic losses, although modest, are concentrated on a small surface and can raise surface temperatures close to operational limits. A complex hot spot patternmore » was revealed with at least 3 physical processes involved : convected power, electron acceleration in the LH near field, and a RF-specific phenomenon compatible with RF sheaths. LH coupling was also perturbed in the antenna shadow. This was attributed to RF-induced DC ExB0 convection. This motivated sheath modelling in two directions. First, the 2D topology of RF potentials was investigated in relation with the RF current distribution over the antenna, via a Green's function formalism and full-wave calculation using the ICANT code. In front of phased arrays of straps, convective cells were interpreted using the RF current profiles of strip line theory. Another class of convective cells, specific to antenna box corners, was evidenced for the first time. Within 1D sheath models assuming independent flux tubes, RF and rectified DC potentials are proportional. 2D fluid models couple nearby flux tubes via transverse polarisation currents. Unexpectedly this does not necessarily smooth RF potential maps. Peak DC potentials can even be enhanced. The experience gained on TS and the numerical tools are valuable for designing steady state high power antennas for next step devices. General rules to reduce RF potentials as well as concrete design options are discussed.« less

A folded waveguide ICRF antenna for PBX-M and TFTR

NASA Astrophysics Data System (ADS)

Bigelow, T. S.; Carter, M. D.; Fogelman, C. H.; Yugo, J. J.; Baity, F. W.; Bell, G. L.; Gardner, W. L.; Goulding, R. H.; Hoffman, D. J.; Ryan, P. M.; Swain, D. W.; Taylor, D. J.; Wilson, R.; Bernabei, S.; Kugel, H.; Ono, M.

1996-02-01

The folded waveguide (FWG) antenna is an advanced ICRF launcher under development at ORNL that offers many significant advantages over current-strap type antennas. These features are particularly beneficial for reactor-relevant applications such as ITER and TPX. Previous tests of a development folded waveguide with a low density plasma load have shown a factor of 5 increase in power capability over loop antennas into similar plasma conditions. The performance and reliability of a FWG with an actual tokamak plasma load must now be verified for further acceptance of this concept. A 58 MHz, 4 MW folded waveguide is being designed and built for the PBX-M and TFTR tokamaks at Princeton Plasma Physics Laboratory. This design has a square cross-section that can be installed as either a fast wave (FW) or ion-Bernstein wave (IBW) launcher by 90° rotation. Two new features of the design are: a shorter quarter-wavelength resonator configuration and a rear-feed input power coupling loop. Loading calculations with a standard shorting plate indicate that a launched power level of 4 MW is possible on either machine. Mechanical and disruption force analysis indicates that bolted construction will withstand the disruption loads. An experimental program is planned to characterize the plasma loading, heating effectiveness, power capability, impurity generation and other factors for both FW and IBW cases. High power tests of the new configuration are being performed with a development FWG unit on RFTF at ORNL.

Characterization and Mitigation of ICRF Antenna - Plasma Edge Interaction

NASA Astrophysics Data System (ADS)

Hong, Rongjie; Tynan, George; Wukitch, Steve; Lin, Yijun; Terry, Jim; Chilenski, M.; Golfinopoulos, T.; Hubbard, A.; Mumgaard, R. T.; Perkins, R.; Reinke, M. L.; Alcator C-Mod Team

2017-10-01

Recent experiments reveal that RF-induced potentials (VRF) in the SOL and impurity source at the antenna can be reduced to background levels via optimizing the power ratio between the inner and outer current straps, Pcent /Pout . Experiments indicate the antenna impurity source reduction for the field aligned antenna is due to geometrical alignment rather than electrical symmetry. Additional experiments performed without an optimized Pcent /Pout showed that VRF and the associated convection cells do not influence the impurity penetration or core impurity confinement. These results suggest the core impurity contamination associated with ICRF heating is dominated by an increased impurity source rather than a change in impurity transport. Further, the convective cell strength was expected to scale inversely with B-field. The observed poloidal velocity (measure of convective cell strength), however, decreased less than expected. In addition, the measured maximum VRF increased and penetrated farther into the SOL at higher B-field and plasma current. Results also suggest VRF is strongly influenced by the SOL plasma parameters rather than by RF parameters. Work supported by the U.S. DoE, Office of Science, Office of Fusion Energy Sciences, User Facility Alcator C-Mod under DE-FC02-99ER54512 and DE-SC 0010720.

Recent ICRF coupling experiments on EAST

NASA Astrophysics Data System (ADS)

Yuqing, YANG; Xinjun, ZHANG; Yanping, ZHAO; Chengming, QIN; Yan, CHENG; Yuzhou, MAO; Hua, YANG; Jianhua, WANG; Shuai, YUAN; Lei, WANG; Songqing, JU; Gen, CHEN; Xu, DENG; Kai, ZHANG; Baonian, WAN; Jiangang, LI; Yuntao, SONG; Xianzu, GONG; Jinping, QIAN; Tao, ZHANG

2018-04-01

Recent ion cyclotron resonance frequency (ICRF) coupling experiments for optimizing ICRF heating in high power discharge were performed on EAST. The coupling experiments were focus on antenna phasing and gas puffing, which were performed separately on two ports of the ion cyclotron resonance heating (ICRH) system of EAST. The antenna phasing was performed on the I-port antenna, which consists of four toroidally spaced radiating straps operating in multiple phasing cases; the coupling performance was better under low wave number | {k}\\parallel | (ranging from 4.5 to 6.5). By fuelling the plasma from gas injectors, placed as uniformly spaced array from top to bottom at each side limiter of the B-port antenna, which works in dipole phasing, the coupling resistance of the B-port antenna increased obviously. Furthermore, the coupling resistance of the I-port antenna was insensitive to a smaller rate of gas puffing but when the gas injection rate was more than a certain value (>1021s‑1), a sharp increase in the coupling resistance of the I-port antenna occurred, which was mainly caused by the toroidal asymmetric boundary density arising from gas puffing. A more specific analysis is given in the paper.

Initial operation of high power ICRF system for long pulse in EAST

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

Qin, C. M., E-mail: chmq@ipp.ac.cn; Zhao, Y. P.; Zhang, X. J.

2015-12-10

The ICRF heating system on EAST upgraded by active cooling aims for long pulse operation. In this paper, the main technical features of the ICRF system are described. One of a major challenges for long pulse operation is RF-edge interactions induced impurity production and heat loading. In EAST, ICRF antenna protections and Faraday screen bars damaged due to LH electron beam are found. Preliminary results for the analysis of the interaction between LHCD and ICRF antenna are discussed. Increase of metal impurities in the plasma during RF pulse and in a larger core radiation are also shown. These RF-edge interactionsmore » at EAST and some preliminary results for the optimizing RF performance will be presented.« less

Measurement of ICRF wave propagation using a microwave reflectometer with fast antenna switching on GAMMA 10

NASA Astrophysics Data System (ADS)

Ikezoe, R.; Ichimura, M.; Itagaki, J.; Hirata, M.; Sumida, S.; Jang, S.; Izumi, K.; Tanaka, A.; Sekine, R.; Kubota, Y.; Shima, Y.; Kohagura, J.; Yoshikawa, M.; Sakamoto, M.; Nakashima, Y.

2017-12-01

Slow Alfvén wave in ion cyclotron range of frequency (ICRF) is a powerful tool to heat ions confined in a mirror field. In spite of its efficient heating effect that has been attained in the central cell of GAMMA 10, there are still unknown characteristics concerning boundary condition, transient variation of heating effect, exact picture of cyclotron damping, and so on. To study these characteristics in detail, a multi-point measurement of the waves inside the hot plasma has been recently developed by using a microwave reflectometer. In addition to a radial profile measurement that is available by a usual reflectometer, an axial measurement has been achieved by arraying transmitting and receiving horn antennas in the axial direction, which are repeatedly switched in time during a discharge with PIN diode switches. Another transmitting and receiving horn antenna pair was newly added to the system and probing at five cross sections was achieved in a single discharge with time resolution of about 1 ms at each antenna pair position. With the upgraded reflectometer system, axial and radial distributions of wave-induced fluctuations and those temporal behavior were clearly observed, offering valuable data on wave physics in a hot mirror plasma.

ICRF-Induced Changes in Floating Potential and Ion Saturation Current in the EAST Divertor

NASA Astrophysics Data System (ADS)

Perkins, Rory; Hosea, Joel; Taylor, Gary; Bertelli, Nicola; Kramer, Gerrit; Qin, Chengming; Wang, Liang; Yang, Jichan; Zhang, Xinjun

2017-10-01

Injection of waves in the ion cyclotron range of frequencies (ICRF) into a tokamak can potentially raise the plasma potential via RF rectification. Probes are affected both by changes in plasma potential and also by RF-averaging of the probe characteristic, with the latter tending to drop the floating potential. We present the effect of ICRF heating on divertor Langmuir probes in the EAST experiment. Over a scan of the outer gap, probes connected to the antennas have increases in floating potential with ICRF, but probes in between the outer-vessel strike point and flux surface tangent to the antenna have decreased floating potential. This behaviour is investigated using field-line mapping. Preliminary results show that mdiplane gas puffing can suppress the strong influence of ICRF on the probes' floating potential.

High-power and steady-state operation of ICRF heating in the large helical device

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

Mutoh, T., E-mail: mutoh@nifs.ac.jp; Seki, T.; Saito, K.

2015-12-10

Recent progress in an ion cyclotron range of frequencies (ICRF) heating system and experiment results in a Large Helical Device (LHD) are reported. Three kinds of ICRF antenna pairs were installed in the LHD, and the operation power regimes were extended up to 4.5 MW; also, the steady-state operation was extended for more than 45 min in LHD at a MW power level. We studied ICRF heating physics in heliotron configuration using a Hand Shake type (HAS) antenna, Field Aligned Impedance Transforming (FAIT) antenna, and Poloidal Array (PA) antenna, and established the optimum minority-ion heating scenario in an LHD. The FAITmore » antenna having a novel impedance transformer inside the vacuum chamber could reduce the VSWR and successfully injected a higher power to plasma. We tested the PA antennas completely removing the Faraday-shield pipes to avoid breakdown and to increase the plasma coupling. The heating performance was almost the same as other antennas; however, the heating efficiency was degraded when the gap between the antenna and plasma surface was large. Using these three kinds of antennas, ICRF heating could contribute to raising the plasma beta with the second- and third-harmonic cyclotron heating mode, and also to raising the ion temperature as discharge cleaning tools. In 2014, steady-state operation plasma with a line-averaged electron density of 1.2 × 10{sup 19} m{sup −3}, ion and electron temperature of 2 keV, and plasma sustainment time of 48 min was achieved with ICH and ECH heating power of 1.2 MW for majority helium with minority hydrogen. In 2015, the higher-power steady-state operation with a heating power of up to 3 MW was tested with higher density of 3 × 10{sup 19} m{sup −3}.« less

Interaction of ICRF Fields with the Plasma Boundary in AUG and JET and Guidelines for Antenna Optimization

NASA Astrophysics Data System (ADS)

Bobkov, V.; Bilato, R.; Braun, F.; Colas, L.; Dux, R.; Van Eester, D.; Giannone, L.; Goniche, M.; Herrmann, A.; Jacquet, P.; Kallenbach, A.; Krivska, A.; Lerche, E.; Mayoral, M.-L.; Milanesio, D.; Monakhov, I.; Müller, H. W.; Neu, R.; Noterdaeme, J.-M.; Pütterich, Th.; Rohde, V.

2009-11-01

W sputtering during ICRF on ASDEX Upgrade (AUG) and temperature rise on JET A2 antenna septa are considered in connection with plasma conditions at the antenna plasma facing components and E‖ near-fields. Large antenna-plasma clearance, high gas puff and low light impurity content are favorable to reduce W sputtering in AUG. The spatial distribution of spectroscopically measured effective W sputtering yields clearly points to the existence of strong E‖ fields at the antenna box ("feeder fields") which dominate over the fields in front of the antenna straps. The picture of E‖ fields, obtained by HFSS code, corroborates the dominant role of E‖ at the antenna box on the formation of sheath-driving RF voltages for AUG. Large antenna-plasma clearance and low gas puff are favorable to reduce septum temperature of JET A2 antennas. Assuming a linear relation between the septum temperature and the sheath driving RF voltage calculated by HFSS, the changes of the temperature with dipole phasing (00ππ, 0ππ0 or 0π0π) are well described by the related changes of the RF voltages. Similarly to the AUG antenna, the strongest E‖ are found at the limiters of the JET A2 antenna for all used dipole phasings and at the septum for the phasings different from 0π0π. A simple general rule can be used to minimize E‖ at the antenna: image currents can be allowed only at the surfaces which do not intersect magnetic field lines at large angles of incidence. Possible antenna modifications generally rely either on a reduction of the image currents, on their short-circuiting by introducing additional conducting surfaces or on imposing the E‖ = 0 boundary condition. On the example of AUG antenna, possible options to minimize the sheath driving voltages are presented.

ORNL diagnostic and modeling development for LAPD ICRF experiments

NASA Astrophysics Data System (ADS)

Isler, R. C.; Caughman, J. B. O.; Lau, C.; Martin, E. H.; Perkins, R. J.; Compernolle, B. Van; Vincena, S.; Tripathi, S. K. P.; Gekelman, W.

2017-10-01

PPPL, UCLA, and ORNL scientists have recently collaborated on a three week ICRF campaign at the upgraded LAPD device to study near field-plasma interactions associated with a single strap antenna driven at 2.38 MHz with 100 kW of RF power. This poster highlights ORNL involvement through implementation of the following diagnostics: an optical emission probe to measure neutral density, a retarding field energy analyzer to measure fast ions, phase locked imaging to measure line integrated RF-driven optical emission fluctuations, and an RF compensated triple Langmuir probe to measure density and temperature. To interpret the results of the experimental campaign a 3D cold plasma finite element model with realistic antenna and vacuum vessel geometry was developed in COMSOL. A summary of these results will be discussed. Highlights include a proof of principle localized and spatially resolved measurement of the neutral density, a strong increase in RF-driven optical emission fluctuations directly in front of the RF antenna strap, a shift in fast ion energies near the plasma edge, and qualitative agreement between the COMSOL cold plasma model with the various diagnostics. Funded by the DOE OFES (DE-AC05-00OR22725, DE-AC02-09CH11466, and DE-FC02-07ER54918) and the Univ. of California (12-LR-237124).

Excitation of slow waves in front of an ICRF antenna in a basic plasma experiment

NASA Astrophysics Data System (ADS)

Soni, Kunal; van Compernolle, Bart; Crombe, Kristel; van Eester, Dirk

2017-10-01

Recent results of ICRF experiments at the Large Plasma Device (LAPD) indicate parasitic coupling to the slow wave by the fast wave antenna. Plasma parameters in LAPD are similar to the scrape-off layer of current fusion devices. The machine has a 17 m long, 60 cm diameter magnetized plasma column with typical plasma parameters ne 1012 -1013 cm-3, Te 1 - 10 eV and B0 1000 G. It was found that coupling to the slow mode occurs when the plasma density in front of the antenna is low enough such that the lower hybrid resonance is present in the plasma. The radial density profile is tailored to allow for fast mode propagation in the high density core and slow mode propagation in the low density edge region. Measurements of the wave fields clearly show two distinct modes, one long wavelength m=1 fast wave mode in the core and a short wavelength backward propagating mode in the edge. Perpendicular wave numbers compare favorably to the predicted values. The experiment was done for varying frequencies, ω /Ωi = 25 , 6 and 1.5. Future experiments will investigate the dependence on antenna tilt angle with respect to the magnetic field, with and without Faraday screen. This work is performed at the Basic Plasma Science Facility, sponsored jointly by DOE and NSF.

ICRF Mode Conversion Flow Drive Experiments on Alcator C-Mod

NASA Astrophysics Data System (ADS)

Lin, Y.; Reinke, M. L.; Rice, J. E.; Wukitch, S. J.; Granetz, R.; Greenwald, M.; Hubbard, A. E.; Marmar, E. S.; Podpaly, Y. A.; Porkolab, M.; Tsujii, N.; Wolfe, S.

2011-12-01

We have carried out a detailed study of the dependence of ICRF mode conversion flow drive (MCFD) on plasma and RF parameters. The flow drive efficiency is found to depend strongly on the 3He concentration in D(3He) plasmas, a key parameter separating the ICRF minority heating regime and mode conversion regime. At +90 ° antenna phasing (waves in the co-Ip direction) and dipole phasing, the driven flow is in the co-Ip direction, and the change of the rotation velocity increases with both PRF and Ip, and scales unfavorably vs. plasma density and antenna frequency. When MCFD is applied to I-mode plasmas, the plasma rotation increases until the onset of MHD modes triggered by large sawtooth crashes. Very high performance I-mode plasmas with HITER98,y2˜1.4 and Te0˜8 keV have been obtained in these experiments.

Modelling of combined ICRF and NBI heating in JET hybrid plasmas

NASA Astrophysics Data System (ADS)

Gallart, Dani; Mantsinen, Mervi; Challis, Clive; Frigione, Domenico; Graves, Jonathan; Hobirk, Joerg; Belonohy, Eva; Czarnecka, Agata; Eriksson, Jacob; Goniche, Marc; Hellesen, Carl; Jacquet, Philippe; Joffrin, Emmanuel; Krawczyk, Natalia; King, Damian; Lennholm, Morten; Lerche, Ernesto; Pawelec, Ewa; Sips, George; Solano, Emilia; Tsalas, Maximos; Valisa, Marco

2017-10-01

During the 2015-2016 JET campaigns many efforts have been devoted to the exploration of high performance plasma scenarios envisaged for ITER operation. In this paper we model the combined ICRF+NBI heating in selected key hybrid discharges using PION. The antenna frequency was tuned to match the cyclotron frequency of minority hydrogen (H) at the center of the tokamak coinciding with the second harmonic cyclotron resonance of deuterium. The modelling takes into account the synergy between ICRF and NBI heating through the second harmonic cyclotron resonance of deuterium beam ions which allows us to assess its impact on the neutron rate RNT. We evaluate the influence of H concentration which was varied in different discharges in order to test their role in the heating performance. According to our modelling, the ICRF enhancement of RNT increases by decreasing the H concentration which increases the ICRF power absorbed by deuterons. We find that in the recent hybrid discharges this ICRF enhancement was in the range of 10-25%. Finally, we extrapolate the results to D-T and find that the best performing hybrid discharges correspond to an equivalent fusion power of ˜7.0 MW in D-T.

Recent progress on improving ICRF coupling and reducing RF-specific impurities in ASDEX Upgrade

NASA Astrophysics Data System (ADS)

Zhang, Wei; Bobkov, Volodymyr; Noterdaeme, Jean-Marie; Tierens, Wouter; Aguiam, Diogo; Bilato, Roberto; Coster, David; Colas, Laurent; Crombé, Kristel; Fuenfgelder, Helmut; Faugel, Helmut; Feng, Yuhe; Jacquot, Jonathan; Jacquet, Philippe; Kallenbach, Arne; Kostic, Ana; Lunt, Tilmann; Maggiora, Riccardo; Ochoukov, Roman; Silva, Antonio; Suárez, Guillermo; Tuccilo, Angelo A.; Tudisco, Onofrio; Usoltceva, Mariia; Van Eester, Dirk; Wang, Yongsheng; Yang, Qingxi

2017-10-01

The recent scientific research on ASDEX Upgrade (AUG) has greatly advanced solutions to two issues of Radio Frequency (RF) heating in the Ion Cyclotron Range of Frequencies (ICRF): (a) the coupling of ICRF power to the plasma is significantly improved by density tailoring with local gas puffing; (b) the release of RF-specific impurities is significantly reduced by minimizing the RF near field with 3-strap antennas. This paper summarizes the applied methods and reviews the associated achievements.

High-Performance Computational Modeling of ICRF Physics and Plasma-Surface Interactions in Alcator C-Mod

NASA Astrophysics Data System (ADS)

Jenkins, Thomas; Smithe, David

2016-10-01

Inefficiencies and detrimental physical effects may arise in conjunction with ICRF heating of tokamak plasmas. Large wall potential drops, associated with sheath formation near plasma-facing antenna hardware, give rise to high-Z impurity sputtering from plasma-facing components and subsequent radiative cooling. Linear and nonlinear wave excitations in the plasma edge/SOL also dissipate injected RF power and reduce overall antenna efficiency. Recent advances in finite-difference time-domain (FDTD) modeling techniques allow the physics of localized sheath potentials, and associated sputtering events, to be modeled concurrently with the physics of antenna near- and far-field behavior and RF power flow. The new methods enable time-domain modeling of plasma-surface interactions and ICRF physics in realistic experimental configurations at unprecedented spatial resolution. We present results/animations from high-performance (10k-100k core) FDTD/PIC simulations spanning half of Alcator C-Mod at mm-scale resolution, exploring impurity production due to localized sputtering (in response to self-consistent sheath potentials at antenna surfaces) and the physics of parasitic slow wave excitation near the antenna hardware and SOL. Supported by US DoE (Award DE-SC0009501) and the ALCC program.

Characterization and performance of a field aligned ion cyclotron range of frequency antenna in Alcator C-Mod

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

Wukitch, S. J.; Garrett, M. L.; Ochoukov, R.

Ion cyclotron range of frequency (ICRF) heating is expected to provide auxiliary heating for ITER and future fusion reactors where high Z metallic plasma facing components (PFCs) are being considered. Impurity contamination linked to ICRF antenna operation remains a major challenge particularly for devices with high Z metallic PFCs. Here, we report on an experimental investigation to test whether a field aligned (FA) antenna can reduce impurity contamination and impurity sources. We compare the modification of the scrape of layer (SOL) plasma potential of the FA antenna to a conventional, toroidally aligned (TA) antenna, in order to explore the underlyingmore » physics governing impurity contamination linked to ICRF heating. The FA antenna is a 4-strap ICRF antenna where the current straps and antenna enclosure sides are perpendicular to the total magnetic field while the Faraday screen rods are parallel to the total magnetic field. In principle, alignment with respect to the total magnetic field minimizes integrated E|| (electric field along a magnetic field line) via symmetry. A finite element method RF antenna model coupled to a cold plasma model verifies that the integrated E|| should be reduced for all antenna phases. Monopole phasing in particular is expected to have the lowest integrated E||. Consistent with expectations, we observed that the impurity contamination and impurity source at the FA antenna are reduced compared to the TA antenna. In both L and H-mode discharges, the radiated power is 20%–30% lower for a FA-antenna heated discharge than a discharge heated with the TA-antennas. However, inconsistent with expectations, we observe RF induced plasma potentials (via gas-puff imaging and emissive probes to be nearly identical for FA and TA antennas when operated in dipole phasing). Moreover, the highest levels of RF-induced plasma potentials are observed using monopole phasing with the FA antenna. Thus, while impurity contamination and sources are

3D Modeling of Antenna Driven Slow Waves Excited by Antennas Near the Plasma Edge

NASA Astrophysics Data System (ADS)

Smithe, David; Jenkins, Thomas

2016-10-01

Prior work with the 3D finite-difference time-domain (FDTD) plasma and sheath model used to model ICRF antennas in fusion plasmas has highlighted the possibility of slow wave excitation at the very low end of the SOL density range, and thus the prudent need for a slow-time evolution model to treat SOL density modifications due to the RF itself. At higher frequency, the DIII-D helicon antenna has much easier access to a parasitic slow wave excitation, and in this case the Faraday screen provides the dominant means of controlling the content of the launched mode, with antenna end-effects remaining a concern. In both cases, the danger is the same, with the slow-wave propagating into a lower-hybrid resonance layer a short distance ( cm) away from the antenna, which would parasitically absorb power, transferring energy to the SOL edge plasma, primarily through electron-neutral collisions. We will present 3D modeling of antennas at both ICRF and helicon frequencies. We've added a slow-time evolution capability for the SOL plasma density to include ponderomotive force driven rarefaction from the strong fields in the vicinity of the antenna, and show initial application to NSTX antenna geometry and plasma configurations. The model is based on a Scalar Ponderomotive Potential method, using self-consistently computed local field amplitudes from the 3D simulation.

High-performance finite-difference time-domain simulations of C-Mod and ITER RF antennas

NASA Astrophysics Data System (ADS)

Jenkins, Thomas G.; Smithe, David N.

2015-12-01

Finite-difference time-domain methods have, in recent years, developed powerful capabilities for modeling realistic ICRF behavior in fusion plasmas [1, 2, 3, 4]. When coupled with the power of modern high-performance computing platforms, such techniques allow the behavior of antenna near and far fields, and the flow of RF power, to be studied in realistic experimental scenarios at previously inaccessible levels of resolution. In this talk, we present results and 3D animations from high-performance FDTD simulations on the Titan Cray XK7 supercomputer, modeling both Alcator C-Mod's field-aligned ICRF antenna and the ITER antenna module. Much of this work focuses on scans over edge density, and tailored edge density profiles, to study dispersion and the physics of slow wave excitation in the immediate vicinity of the antenna hardware and SOL. An understanding of the role of the lower-hybrid resonance in low-density scenarios is emerging, and possible implications of this for the NSTX launcher and power balance are also discussed. In addition, we discuss ongoing work centered on using these simulations to estimate sputtering and impurity production, as driven by the self-consistent sheath potentials at antenna surfaces.

Experimental pathways to understand and avoid high-Z impurity contamination from ICRF heating in tokamaks

NASA Astrophysics Data System (ADS)

Reinke, Matthew

2016-10-01

Recent results from Alcator C-Mod and JET demonstrate progress in understanding and mitigating core high-Z impurity contamination linked to ICRF heating in tokamaks with high-Z PFCs. Theory has identified two likely mechanisms: impurity sources due to sputtering enhanced by RF-rectified sheaths and greater cross-field SOL transport due to ExB convective cells. New experiments on Alcator C-Mod and JET demonstrate convective cell transport is likely a sub-dominant effect, despite directly observing ExB flows from rectified RF fields on C-Mod. Trace N2 introduced in the far SOL on field lines connected to and well away from an active ICRF antenna result in similar levels of core nitrogen, indicating local RF-driven transport is weak. This suggests the core high-Z density, nZ,core, is determined by sheath-induced sputtering and RF-independent SOL transport, allowing further reductions through antenna design. ICRF heating on C-Mod uses a unique, field aligned (FAA) and a pair of conventional, toroidally aligned (TAA) antennas. The FAA is designed to reduce rectified voltages relative to the TAA, and the impact of sheath-induced sputtering is explored by observing nZ,core while varying the TAA/FAA heating mix. A reduction of approximately 50% in core high-Z content is seen in L-modes when using the FAA and high-Z sources at the antenna limiter are effectively eliminated, indicating the remaining RF-driven source is away from the limiter. A drop in nZ,core may also be realized by locating the RF antenna on the inboard side where SOL transport aids impurity screening. New C-Mod experiments demonstrate up to a factor of 5 reduction in core nitrogen when N2 is injected on the high-field side as compared to low-field side impurity fueling. Varying the magnetic topology helps to elucidate the SOL transport physics responsible, laying a physics basis for inboard RF antenna placement. This work is supported by U.S. DOE Award DE-FC02-99ER54512, using Alcator C-Mod and carried out

High-performance finite-difference time-domain simulations of C-Mod and ITER RF antennas

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

Jenkins, Thomas G., E-mail: tgjenkins@txcorp.com; Smithe, David N., E-mail: smithe@txcorp.com

Finite-difference time-domain methods have, in recent years, developed powerful capabilities for modeling realistic ICRF behavior in fusion plasmas [1, 2, 3, 4]. When coupled with the power of modern high-performance computing platforms, such techniques allow the behavior of antenna near and far fields, and the flow of RF power, to be studied in realistic experimental scenarios at previously inaccessible levels of resolution. In this talk, we present results and 3D animations from high-performance FDTD simulations on the Titan Cray XK7 supercomputer, modeling both Alcator C-Mod’s field-aligned ICRF antenna and the ITER antenna module. Much of this work focuses on scansmore » over edge density, and tailored edge density profiles, to study dispersion and the physics of slow wave excitation in the immediate vicinity of the antenna hardware and SOL. An understanding of the role of the lower-hybrid resonance in low-density scenarios is emerging, and possible implications of this for the NSTX launcher and power balance are also discussed. In addition, we discuss ongoing work centered on using these simulations to estimate sputtering and impurity production, as driven by the self-consistent sheath potentials at antenna surfaces.« less

Plasma-Surface Interactions and RF Antennas

NASA Astrophysics Data System (ADS)

Jenkins, Thomas; Smithe, D. N.; Beckwith, K.; Davidson, B. D.; Kruger, S. E.; Pankin, A. Y.; Roark, C. M.

2015-11-01

Implementation of recently developed finite-difference time-domain (FDTD) modeling techniques on high-performance computing platforms allows RF power flow, and antenna near- and far-field behavior, to be studied in realistic experimental ion-cyclotron resonance heating scenarios at previously inaccessible levels of resolution. We present results and 3D animations of high-performance (10k-100k core) FDTD simulations of Alcator C-Mod's field-aligned ICRF antenna on the Titan supercomputer, considering (a) the physics of slow wave excitation in the immediate vicinity of the antenna hardware and in the scrape-off layer for various edge densities, and (b) sputtering and impurity production, as driven by self-consistent sheath potentials at antenna surfaces. Related research efforts in low-temperature plasma modeling, including the use of proper orthogonal decomposition methods for PIC/fluid modeling and the development of plasma chemistry tools (e.g. a robust and flexible reaction database, principal path reduction analysis capabilities, and improved visualization options), will also be summarized. Supported by U.S. DoE SBIR Phase I/II Award DE-SC0009501 and ALCC/OLCF.

Refinement of the ICRF

NASA Technical Reports Server (NTRS)

Ma, Chopo

2004-01-01

Since the ICRF was generated in 1995, VLBI modeling and estimation, data quality: source position stability analysis, and supporting observational programs have improved markedly. There are developing and potential applications in the areas of space navigation Earth orientation monitoring and optical astrometry from space that would benefit from a refined ICRF with enhanced accuracy, stability and spatial distribution. The convergence of analysis, focused observations, and astrometric needs should drive the production of a new realization in the next few years.

ICRF heating in a straight, helically symmetric stellarator

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

Jaeger, E.F.; Weitzner, H.; Batchelor, D.B.

1987-07-01

Experimental observations of direct ion cyclotron resonant frequency (ICRF) heating at fundamental ion cyclotron resonance on the L-2 stellarator have stimulated interest in the theoretical basis for such heating. In this paper, global solutions for the ICRF wave fields in a helically symmetric, straight stellarator are calculated in the cold plasma limit. The component of the wave electric field parallel to B-vector is assumed zero. Helical symmetry allows Fourier decomposition in the longitudinal (z) direction. The two remaining partial differential equations in tau and phi identical to THETA - hz (h is the helical pitch) are solved by finite differencing.more » Energy absorption and antenna impedance are calculated from an ad hoc collision model. Results for parameters typical of the L-2 and Advanced Toroidal Facility (ATF) stellarators show that direct resonant absorption of the fundamental ion cyclotron resonance occurs mainly near the plasma edge. The magnitude of the absorption is about half that for minority heating at the two-ion hybrid resonance.« less

2D modeling of DC potential structures induced by RF sheaths with transverse currents in front of ICRF antenna

NASA Astrophysics Data System (ADS)

Faudot, E.; Heuraux, S.; Colas, L.

2005-09-01

Understanding DC potential generation in front of ICRF antennas is crucial for long pulse high RF power systems. DC potentials are produced by sheath rectification of these RF potentials. To reach this goal, near RF parallel electric fields have to be computed in 3D and integrated along open magnetic field lines to yield a 2D RF potential map in a transverse plane. DC potentials are produced by sheath rectification of these RF potentials. As RF potentials are spatially inhomogeneous, transverse polarization currents are created, modifying RF and DC maps. Such modifications are quantified on a `test map' having initially a Gaussian shape and assuming that the map remains Gaussian near its summit,the time behavior of the peak can be estimated analytically in presence of polarization current as a function of its width r0 and amplitude φ0 (normalized to a characteristic length for transverse transport and to the local temperature). A `peaking factor' is built from the DC peak potential normalized to φ0, and validated with a 2D fluid code and a 2D PIC code (XOOPIC). In an unexpected way transverse currents can increase this factor. Realistic situations of a Tore Supra antenna are also studied, with self-consistent near fields provided by ICANT code. Basic processes will be detailed and an evaluation of the `peaking factor' for ITER will be presented for a given configuration.

2D modeling of DC potential structures induced by RF sheaths with transverse currents in front of ICRF antenna

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

Faudot, E.; Heuraux, S.; Colas, L.

2005-09-26

Understanding DC potential generation in front of ICRF antennas is crucial for long pulse high RF power systems. DC potentials are produced by sheath rectification of these RF potentials. To reach this goal, near RF parallel electric fields have to be computed in 3D and integrated along open magnetic field lines to yield a 2D RF potential map in a transverse plane. DC potentials are produced by sheath rectification of these RF potentials. As RF potentials are spatially inhomogeneous, transverse polarization currents are created, modifying RF and DC maps. Such modifications are quantified on a 'test map' having initially amore » Gaussian shape and assuming that the map remains Gaussian near its summit,the time behavior of the peak can be estimated analytically in presence of polarization current as a function of its width r0 and amplitude {phi}0 (normalized to a characteristic length for transverse transport and to the local temperature). A 'peaking factor' is built from the DC peak potential normalized to {phi}0, and validated with a 2D fluid code and a 2D PIC code (XOOPIC). In an unexpected way transverse currents can increase this factor. Realistic situations of a Tore Supra antenna are also studied, with self-consistent near fields provided by ICANT code. Basic processes will be detailed and an evaluation of the 'peaking factor' for ITER will be presented for a given configuration.« less

Time-Domain Modeling of RF Antennas and Plasma-Surface Interactions

NASA Astrophysics Data System (ADS)

Jenkins, Thomas G.; Smithe, David N.

2017-10-01

Recent advances in finite-difference time-domain (FDTD) modeling techniques allow plasma-surface interactions such as sheath formation and sputtering to be modeled concurrently with the physics of antenna near- and far-field behavior and ICRF power flow. Although typical sheath length scales (micrometers) are much smaller than the wavelengths of fast (tens of cm) and slow (millimeter) waves excited by the antenna, sheath behavior near plasma-facing antenna components can be represented by a sub-grid kinetic sheath boundary condition, from which RF-rectified sheath potential variation over the surface is computed as a function of current flow and local plasma parameters near the wall. These local time-varying sheath potentials can then be used, in tandem with particle-in-cell (PIC) models of the edge plasma, to study sputtering effects. Particle strike energies at the wall can be computed more accurately, consistent with their passage through the known potential of the sheath, such that correspondingly increased accuracy of sputtering yields and heat/particle fluxes to antenna surfaces is obtained. The new simulation capabilities enable time-domain modeling of plasma-surface interactions and ICRF physics in realistic experimental configurations at unprecedented spatial resolution. We will present results/animations from high-performance (10k-100k core) FDTD/PIC simulations of Alcator C-Mod antenna operation.

Study of the effects of corrugated wall structures due to blanket modules around ICRH antennas

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

Dumortier, Pierre; Louche, Fabrice; Messiaen, André

2014-02-12

In future fusion reactors, and in ITER, the first wall will be covered by blanket modules. These blanket modules, whose dimensions are of the order of the ICRF wavelengths, together with the clearance gaps between them will constitute a corrugated structure which will interact with the electromagnetic waves launched by ICRF antennas. The conditions in which the grooves constituted by the clearance gaps between the blanket modules can become resonant are studied. Simple analytical models and numerical simulations show that mushroom type structures (with larger gaps at the back than at the front) can bring down the resonance frequencies, whichmore » could lead to large voltages in the gaps between the blanket modules and perturb the RF properties of the antenna if they are in the ICRF operating range. The effect on the wave propagation along the wall structure, which is acting as a spatially periodic (toroidally and poloidally) corrugated structure, and hence constitutes a slow wave structure modifying the wall boundary condition, is examined.« less

Design, performance, and grounding aspects of the International Thermonuclear Experimental Reactor ion cyclotron range of frequencies antenna

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

Durodié, F., E-mail: frederic.durodie@rma.ac.be; Dumortier, P.; Vrancken, M.

2014-06-15

ITER's Ion Cyclotron Range of Frequencies (ICRF) system [Lamalle et al., Fusion Eng. Des. 88, 517–520 (2013)] comprises two antenna launchers designed by CYCLE (a consortium of European associations listed in the author affiliations above) on behalf of ITER Organisation (IO), each inserted as a Port Plug (PP) into one of ITER's Vacuum Vessel (VV) ports. Each launcher is an array of 4 toroidal by 6 poloidal RF current straps specified to couple up to 20 MW in total to the plasma in the frequency range of 40 to 55 MHz but limited to a maximum system voltage of 45 kV andmore » limits on RF electric fields depending on their location and direction with respect to, respectively, the torus vacuum and the toroidal magnetic field. A crucial aspect of coupling ICRF power to plasmas is the knowledge of the plasma density profiles in the Scrape-Off Layer (SOL) and the location of the RF current straps with respect to the SOL. The launcher layout and details were optimized and its performance estimated for a worst case SOL provided by the IO. The paper summarizes the estimated performance obtained within the operational parameter space specified by IO. Aspects of the RF grounding of the whole antenna PP to the VV port and the effect of the voids between the PP and the Blanket Shielding Modules (BSM) surrounding the antenna front are discussed. These blanket modules, whose dimensions are of the order of the ICRF wavelengths, together with the clearance gaps between them will constitute a corrugated structure which will interact with the electromagnetic waves launched by ICRF antennas. The conditions in which the grooves constituted by the clearance gaps between the blanket modules can become resonant are studied. Simple analytical models and numerical simulations show that mushroom type structures (with larger gaps at the back than at the front) can bring down the resonance frequencies, which could lead to large voltages in the gaps between the blanket modules and

Aspects of ICRF-3

NASA Astrophysics Data System (ADS)

Ma, Chopo; MacMillan, Daniel; Le Bail, Karine; Gordon, David

2016-12-01

The Second Realization of the International Celestial Reference Frame (ICRF2) used dual-frequency VLBI data acquired for geodetic and astrometric purposes from 1979-2009 by organizations coordinated by the IVS and various precursor networks. Since 2009 the data set has been significantly broadened, especially by observations in the southern hemisphere. While the new southern data have ameliorated the north/south imbalance of observations, they appear to produce a systematic zonal declination change in the catalog positions. Over the 35 years of the ICRF data set the effect of galactic aberration may be significant. Geophysical and tropospheric models also may affect the source positions. All these effects need to be addressed in preparation for ICRF-3.

Considerations for ICRF-3

NASA Astrophysics Data System (ADS)

Ma, Chopo; MacMillan, Daniel; Gordon, David

2015-08-01

The Second Realization of the International Celestial Reference Frame (ICRF) used dual-frequency VLBI data acquired for geodetic and astrometric purposes from 1979-2009 by organizations now coordinated by the International VLBI Service for Geodesy and Astrometry (IVS) and analyzed according to the Conventions of the International Earth Rotation and Reference Systems Service (IERS). Since 2009 the data set has been significantly broadened, especially by observations in the Southern Hemisphere, and modeling of astronomical, geophysical and tropospheric effects has progressed. The new southern data appear to cause a systematic zonal declination change in the catalog positions. Over the three decades of the ICRF data set the effect of galactic aberration may be significant. Geophysical and tropospheric models also may affect the source positions. All these effects need to be addressed in preparation for ICRF-3.

Towards a Future ICRF Realization

NASA Technical Reports Server (NTRS)

Ma, Chopo; Gordon, D.; MacMillan, D.; Petrov, L.; Smith, David E. (Technical Monitor)

2001-01-01

The data and analysis for the ICRF were completed in 1995 to define a frame to which the Hipparcos optical catalog could be fixed. Additional observations on most of the 608 sources in the overall ICRF catalog have been acquired using a small portion of geodetic observing time as well as astrometric sessions concentrating on the southern hemisphere. Positions of new sources have been determined, including approx.1200 from a VLBA phase calibrator survey. A future ICRF realization will require improved geophysical modeling, sophisticated treatment of position variations and/or source structure, optimized data selection and weighting, and reidentification of defining sources. The motivation for the next realization could be significant improvement in accuracy and density or preparation for optical extragalactic catalogs with microarcsecond precision.

Towards a Future ICRF Realization

NASA Technical Reports Server (NTRS)

Ma, Chopo; Gordon, David; MacMillan, Daniel; Petrov, Leonid

2002-01-01

The data and analysis for the ICRF were completed in 1995 to define a frame to which the Hipparcos optical catalog could be fixed. Additional observations on most of the 608 sources in the overall ICRF catalog have been acquired using a small portion of geodetic observing time as well as astrometric sessions concentrating on the Southern Hemisphere. Positions of new sources have been determined, including approximately 1200 from a VLBA phase calibrator survey. A future ICRF realization will require improved geophysical modeling, sophisticated treatment of position variations and/or source structure, optimized data selection and weighting, and re-identification of defining sources. The motivation for the next realization could be significant improvement in accuracy and density or preparation for optical extragalactic catalogs with microarcsecond precision.

ICRF-187 in clinical oncology.

PubMed

Poster, D S; Penta, J S; Bruno, S; Macdonald, J S

1981-01-01

Although the mechanism of action of ICRF-159 and 187 has not been clearly defined, it is evident from both preclinical and early clinical studies that these compounds are of interest. There are three distinct characteristics of these ICRF compounds that deserve careful clinical evaluation. First, these drugs are apparently alkylating agents with modest, predictable and noncumulative bone marrow toxicity that makes them good potential candidates for combination chemotherapy regimens. The second characteristic that should be investigated is the suggestion that combination of ICRF-187 with an anthracycline may ameliorate the cardiac toxicity of the latter. The third factor in the preclinical evaluation of the bis-diketopiperazines that may have clinical application is the evidence that suggests that these drugs have an antimetastatic effect.

Tunable biasing magnetic field design of ferrite tuner for ICRF heating system in EAST

NASA Astrophysics Data System (ADS)

Manman, XU; Yuntao, SONG; Gen, CHEN; Yanping, ZHAO; Yuzhou, MAO; Guang, LIU; Zhen, PENG

2017-11-01

Ion cyclotron range of frequency (ICRF) heating has been used in tokamaks as one of the most successful auxiliary heating tools and has been adopted in the EAST. However, the antenna load will fluctuate with the change of plasma parameters in the ICRF heating process. To ensure the steady operation of the ICRF heating system in the EAST, fast ferrite tuner (FFT) has been carried out to achieve real-time impedance matching. For the requirements of the FFT impedance matching system, the magnet system of the ferrite tuner (FT) was designed by numerical simulations and experimental analysis, where the biasing magnetic circuit and alternating magnetic circuit were the key researched parts of the ferrite magnet. The integral design goal of the FT magnetic circuit is that DC bias magnetic field is 2000 Gs and alternating magnetic field is ±400 Gs. In the FTT, E-type magnetic circuit was adopted. Ferrite material is NdFeB with a thickness of 30 mm by setting the working point of NdFeB, and the ampere turn of excitation coil is 25 through the theoretical calculation and simulation analysis. The coil inductance to generate alternating magnetic field is about 7 mH. Eddy-current effect has been analyzed, while the magnetic field distribution has been measured by a Hall probe in the medium plane of the biasing magnet. Finally, the test results show the good performance of the biasing magnet satisfying the design and operating requirements of the FFT.

Extending the ICRF to Higher Radio Frequencies

NASA Technical Reports Server (NTRS)

Jacobs, C. S.; Jones, D. L.; Lanyi, G. E.; Lowe, S. T.; Naudet, C. J.; Resch, G. M.; Steppe, J. A.; Zhang, L. D.; Ulvestad, J. S.; Taylor, G. B.

2002-01-01

The ICRF forms the basis for all astrometry including use as the inertial coordinate system for navigating deep space missions. This frame was defined using S/X-band observations over the past 20+ years. In January 2002, the VLBA approved our proposal for observing time to extend the ICRF to K-band (24 GHz) and Q-band (43 GHz). The first step will be observations at K- and Q-bands on a subset of ICRF sources. Eventually, K- and Q-band multi-epoch observations will be used to estimate positions, flux density and source structure for a large fraction of the current S/X-band ICRF source list. This work will benefit the radio astronomy community by extending the VLBA calibrator list at these bands. In the longer term, we would also like to extend the ICRF to Ka-band (32 GHz). A celestial reference frame will be needed at this frequency to support deep space navigation. A navigation demonstration is being considered for NASA's Mars 2005 mission. The initial K- and Q-band work will serve to identify candidate sources at Ka-band for use with that mission.

Toward the ICRF3: Astrometric Comparison of the USNO 2016A VLBI Solution with ICRF2 and Gaia DR1

NASA Astrophysics Data System (ADS)

Frouard, Julien; Johnson, Megan C.; Fey, Alan; Makarov, Valeri V.; Dorland, Bryan N.

2018-06-01

The VLBI USNO 2016A (U16A) solution is part of a work-in-progress effort by USNO toward the preparation of the ICRF3. Most of the astrometric improvement with respect to the ICRF2 is due to the re-observation of the VCS sources. Our objective in this paper is to assess U16A’s astrometry. A comparison with ICRF2 shows statistically significant offsets of size 0.1 mas between the two solutions. While Gaia DR1 positions are not precise enough to resolve these offsets, they are found to be significantly closer to U16A than ICRF2. In particular, the trend for typically larger errors for southern sources in VLBI solutions is decreased in U16A. Overall, the VLBI-Gaia offsets are reduced by 21%. The U16A list includes 718 sources not previously included in ICRF2. Twenty of those new sources have statistically significant radio-optical offsets. In two-thirds of the cases, these offsets can be explained from PanSTARRS images.

Uses of the ICRF and implications for future VLBI

NASA Technical Reports Server (NTRS)

Ma, Chopo

2006-01-01

Since its inception on 1 Jan 1998, the fundamental ICRF has been set by the VLBI positions of 212 "defining" extragalactic radio sources. In all there are approx.3000 sources with usefully accurate (< few mas) positions consistent with the ICRF. The uses of the ICRF include fundamental astrometry, monitoring of Earth orientation, and spacecraft navigation. For fundamental astrometry, stability and accuracy are most important, and realizations at different frequencies must be in proper registration. However, there is no preferred frequency, and the GAIA mission has the potential for an optical ICRF with 500,000 objects at the 50 microarcsec level some time after the planned 2011 launch. The radio ICRF should be properly prepared for a transition to assure long term stability and consistency. Earth orientation monitoring requires objects attached to the solid Earth, and VLBI will continue to be the fundamental technique. For this purpose it is essential that the new VLBI stations contemplated in the VLBI20l0 report be capable of observing a sufficiently large and well-distributed set of stable sources, and identifying these sources is an on-going effort. Spacecraft navigation by differential VLBI is planned using the Ka-band telemetry signal, and work has begun towards an ICRF realization suitable for this purpose. The balancing of different needs related to the VLBI ICRF will be discussed.

International Celestial Reference Frame (ICRF): mantenimiento y extensión

NASA Astrophysics Data System (ADS)

Ma, C.; Arias, E. F.; Eubanks, T.; Fey, A. L.; Gontier, A.-M.; Jacobs, C. S.; Sovers, O. J.; Archinal, B. A.; Charlot, P.

A partir de enero de 1998 el sistema de referencia celeste convencional está representado por el International Celestial Reference System (ICRS) y materializado a través de las coordenadas VLBI del conjunto de radiofuentes extragalácticas que conforman el International Celestial Reference Frame (ICRF). La primera realización del ICRF, fue elaborada en 1995 por un grupo de expertos designado por la IAU, la que encomendó al International Earth Rotation Service el mantenimiento del ICRS, del ICRF y del vínculo con marcos de referencia en otras frecuencias. Una primera extensión del ICRF se realizó entre abril y junio de 1999, con el objetivo primario de proveer posiciones de radiofuentes extragalácticas observadas a partir de julio de 1995 y de mejorar las posiciones de las fuentes ``candidatas" con la inclusión de observaciones adicionales. Objetivos secundarios fueron monitorear a las radiofuentes para verificar que siguen siendo adecuadas para realizar al ICRF y mejorar las técnicas de análisis de datos. Como resultado del nuevo análisis se obtuvo una solución a partir de la cual se construyó la primera extensión del ICRF, denominada ICRF - Ext.1. Ella representa al ICRS, sus fuentes de definición se mantienen con las mismas posiciones y errores que en la primera realización del ICRF; las demás radiofuentes tienen coordenadas mejor determinadas que en ICRF; el marco de referencia se densificó con el agregado de 59 nuevas radiofuentes.

Acceleration of Dense Flowing Plasmas using ICRF Power in the VASIMR Experiment

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

Squire, Jared P.

2005-09-26

ICRF power in the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) concept energizes ions (> 100 eV) in a diverging magnetic field to accelerate a dense ({approx} 1019 m-3) flowing plasma to velocities useful for space propulsion ({approx}100 km/s). Theory predicts that an ICRF slow wave launched from the high field side of the resonance will propagate in the magnetic beach to absorb nearly all of the power at the resonance, thus efficiently converting the RF power to ion kinetic energy. The plasma flows through the resonance only once, so the ions are accelerated in a single pass. This process hasmore » proven efficient ({approx} 70%) with an ICRF power level of 1.5 kW at about 3.6 MHz in the VASIMR experiment, VX-30, using deuterium plasma created by a helicon operating in flowing mode. We have measured ICRF plasma loading up to 2 ohms, consistent with computational predictions made using Oak Ridge National Laboratory's EMIR code. Recent helicon power upgrades (20 kW at 13.56 MHz) have enabled a 5 cm diameter target plasma for ICRF with an ion flux of over 3x10 20 s-1 and a high degree of ionization. This paper summarizes our ICRF results and presents the latest helicon developments in VX-30.« less

The Second International Celestial Reference Frame (ICRF2)

NASA Technical Reports Server (NTRS)

Ma, Chopo

2010-01-01

The ICRF2 catalog was constructed by the IERS/IVS Working Group with oversight by the IAU Working Group. Derived using data from August 1979 through March 2009, it is a great improvement over the original ICRF with 3414 extragalactic radio source positions, a noise floor of 40 microarcsec, and axis stability of 10 microarcsec. Significant refinements were made in the selection of defining sources, modeling, and the integration of CRF, TRF, and EOP. The adoption of the ICRF2 was approved by the IAU in Resolution B3 at the XXVII IAU General Assembly and became effective 1 January 2010.

VizieR Online Data Catalog: VLBI ICRF2 (Fey+, 2015)

NASA Astrophysics Data System (ADS)

Fey, A. L.; Gordon, D.; Jacobs, C. S.; Ma, C.; Gaume, R. A.; Arias, E. F.; Bianco, G.; Boboltz, D. A.; Bockmann, S.; Bolotin, S.; Charlot, P.; Collioud, A.; Engelhardt, G.; Gipson, J.; Gontier, A.-M.; Heinkelmann, R.; Kurdubov, S.; Lambert, S.; Lytvyn, S.; MacMillan, D. S.; Malkin, Z.; Nothnagel, A.; Ojha, R.; Skurikhina, E.; Sokolova, J.; Souchay, J.; Sovers, O. J.; Tesmer, V.; Titov, O.; Wang, G.; Zharov, V.

2016-01-01

We present the second realization of the International Celestial Reference Frame (ICRF2) at radio wavelengths using nearly 30 years of Very Long Baseline Interferometry observations. The earliest observations used are from 1979 August and the latest are from 2009 March. ICRF2 consists of accurate positions of 295 new "defining" sources and positions of 3119 additional compact radio sources to densify the frame. ICRF2 has more than 5 times as many sources as ICRF1 (Ma et al. 1997, cat. I/251), is roughly 5-6 times more accurate, and is nearly twice as stable in the orientation of its axes. (3 data files).

ICRF Development for the Variable Specific Impulse Magnetoplasma Rocket

NASA Astrophysics Data System (ADS)

Ryan, P. M.; Baity, F. W.; Barber, G. C.; Carter, M. D.; Hoffman, D. J.; Jaeger, E. F.; Taylor, D. J.; Chang-Diaz, F. R.; Squire, J. P.; McCaskill, G.

1997-11-01

The feasibility of using magnetically vectored and rf-heated plasmas for space propulsion (F. R. Chang-Diaz, et al., Bull. Am. Phys. Soc., 41, 1541 (1996)) is being investigated experimentally on an asymmetric magnetic mirror device at the Advanced Space Propulsion Laboratory (ASPL), Johnson Space Center, NASA. Analysis of the antenna interaction with and the wave propagation through the dense plasma propulsion system is being studied at ORNL(Oak Ridge National Laboratory, managed by Lockheed Martin Energy Research Corp. for the U.S. Department of Energy under contract number DE-AC05-96OR22464.), using antenna design codes developed for ICH systems and mirror codes developed for the EBT experiment at ORNL. The present modeling effort is directed toward the ASPL experimental device. Antenna optimization and performance, as well as the design considerations for space-qualified rf components and systems (minimizing weight while maximizing reliability) will be presented.

Bulk ion heating with ICRF waves in tokamaks

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

Mantsinen, M. J., E-mail: mervi.mantsinen@bsc.es; Barcelona Supercomputing Center, Barcelona; Bilato, R.

2015-12-10

Heating with ICRF waves is a well-established method on present-day tokamaks and one of the heating systems foreseen for ITER. However, further work is still needed to test and optimize its performance in fusion devices with metallic high-Z plasma facing components (PFCs) in preparation of ITER and DEMO operation. This is of particular importance for the bulk ion heating capabilities of ICRF waves. Efficient bulk ion heating with the standard ITER ICRF scheme, i.e. the second harmonic heating of tritium with or without {sup 3}He minority, was demonstrated in experiments carried out in deuterium-tritium plasmas on JET and TFTR andmore » is confirmed by ICRF modelling. This paper focuses on recent experiments with {sup 3}He minority heating for bulk ion heating on the ASDEX Upgrade (AUG) tokamak with ITER-relevant all-tungsten PFCs. An increase of 80% in the central ion temperature T{sub i} from 3 to 5.5 keV was achieved when 3 MW of ICRF power tuned to the central {sup 3}He ion cyclotron resonance was added to 4.5 MW of deuterium NBI. The radial gradient of the T{sub i} profile reached locally values up to about 50 keV/m and the normalized logarithmic ion temperature gradients R/LT{sub i} of about 20, which are unusually large for AUG plasmas. The large changes in the T{sub i} profiles were accompanied by significant changes in measured plasma toroidal rotation, plasma impurity profiles and MHD activity, which indicate concomitant changes in plasma properties with the application of ICRF waves. When the {sup 3}He concentration was increased above the optimum range for bulk ion heating, a weaker peaking of the ion temperature profile was observed, in line with theoretical expectations.« less

Workshop on High Power ICH Antenna Designs for High Density Tokamaks

NASA Astrophysics Data System (ADS)

Aamodt, R. E.

1990-02-01

A workshop in high power ICH antenna designs for high density tokamaks was held to: (1) review the data base relevant to the high power heating of high density tokamaks; (2) identify the important issues which need to be addressed in order to ensure the success of the ICRF programs on CIT and Alcator C-MOD; and (3) recommend approaches for resolving the issues in a timely realistic manner. Some specific performance goals for the antenna system define a successful design effort. Simply stated these goals are: couple the specified power per antenna into the desired ion species; produce no more than an acceptable level of RF auxiliary power induced impurities; and have a mechanical structure which safely survives the thermal, mechanical and radiation stresses in the relevant environment. These goals are intimately coupled and difficult tradeoffs between scientific and engineering constraints have to be made.

Influence of ICRF heating on the stability of TAEs

NASA Astrophysics Data System (ADS)

Sears, J.; Burke, W.; Parker, R. R.; Snipes, J. A.; Wolfe, S.

2007-11-01

Unstable toroidicity-induced Alfv'en eigenmodes (TAEs) can appear spontaneously due to resonant interaction with fast particles such as fusion alphas, raising concern that TAEs may threaten ITER performance. This work investigates the progression of stable TAE damping rates toward instability during a scan of ICRF heating power up to 3.1 MW. Stable eigenmodes are identified in Alcator C-Mod by the Active MHD diagnostic. Unstable TAEs are observed to appear spontaneously in C-Mod limited L-mode plasmas at sufficient tail energies generated by >3 MW of ICRF heating. However preliminary analysis of experiments with moderate ICRF heating power show that TAE stability may not simply degrade with overall fast particle content. There are hints that the stability of some TAEs may be enhanced in the presence of fast particle distribution tails. Furthermore, the radial profile of the energetic particle distribution relative to the safety factor profile affects the ICRF power influence on TAE stability.

The IAU Division A Working Group on the Third Realization of the ICRF: Background, Goals, Plans

NASA Astrophysics Data System (ADS)

Gaume, Ralph

2015-08-01

The XXVIII General Assembly of the IAU (Beijing, 2012) established the Division A Working Group on the Third Realization of the International Celestial Reference Frame (ICRF). The adopted charter of the ICRF3 Working Group includes a commitment to report on the implementation and execution plans for ICRF3 during the XXIX General Assembly of the IAU along with a targeted completion and presentation of ICRF3 in 2018 to the XXX General Assembly for adoption. This talk will discuss the background, purpose, and overall implementation plan for ICRF3, and motivate the concept, currently under consideration by the ICRF3 Working Group, that future realizations of the ICRF be based on multi-frequency astrometric data, starting with ICRF3.

TOPICA/TORIC integration for self-consistent antenna and plasma analysis

NASA Astrophysics Data System (ADS)

Maggiora, Riccardo; Lancellotti, Vito; Milanesio, Daniele; Kyrytsya, Volodymyr; Vecchi, Giuseppe; Bonoli, Paul T.; Wright, John C.

2006-10-01

TOPICA [1] is a numerical suite conceived for prediction and analysis of plasma-facing antennas. It can handle real-life 3D antenna geometries (with housing, Faraday screen, etc.) as well as a realistic plasma model, including measured density and temperature profiles. TORIC [2] solves the finite Larmor radius wave equations in the ICRF regime in arbitrary axisymmetric toroidal plasmas. Due to the approach followed in developing TOPICA (i.e. the formal splitting of the problem in the vacuum region around the antenna and the plasma region inside the toroidal chamber), the code lends itself to handle toroidal plasmas, provided TORIC is run independently to yield the plasma surface admittance tensorsY (m,m',n). The latter enter directly into the integral equations solved by TOPICA, thus allowing a far more accurate plasma description that accounts for curvature effects. TOPICA outputs comprise, among others, the EM fields in front of the plasma: these can in turn be input to TORIC, in order to self-consistently determine the EM field propagation in the plasma. In this work, we report on the theory underlying the TOPICA/TORIC integration and the ongoing evolution of the two codes. [1] V. Lancellotti et al., Nucl. Fusion, 46 (2006) S476 [2] M. Brambilla, Plasma Phys. Contr. Fusion (1999) 41 1

A new B-dot probe-based diagnostic for amplitude, polarization, and wavenumber measurements of ion cyclotron range-of frequency fields on ASDEX Upgrade

NASA Astrophysics Data System (ADS)

Ochoukov, R.; Bobkov, V.; Faugel, H.; Fünfgelder, H.; Noterdaeme, J.-M.

2015-11-01

A new B-dot probe-based diagnostic has been installed on an ASDEX Upgrade tokamak to characterize ion cyclotron range-of frequency (ICRF) wave generation and interaction with magnetized plasma. The diagnostic consists of a field-aligned array of B-dot probes, oriented to measure fast and slow ICRF wave fields and their field-aligned wavenumber (k//) spectrum on the low field side of ASDEX Upgrade. A thorough description of the diagnostic and the supporting electronics is provided. In order to compare the measured dominant wavenumber of the local ICRF fields with the expected spectrum of the launched ICRF waves, in-air near-field measurements were performed on the newly installed 3-strap ICRF antenna to reconstruct the dominant launched toroidal wavenumbers (ktor). Measurements during a strap current phasing scan in tokamak discharges reveal an upshift in k// as strap phasing is moved away from the dipole configuration. This result is the opposite of the ktor trend expected from in-air near-field measurements; however, the near-field based reconstruction routine does not account for the effect of induced radiofrequency (RF) currents in the passive antenna structures. The measured exponential increase in the local ICRF wave field amplitude is in agreement with the upshifted k//, as strap phasing moves away from the dipole configuration. An examination of discharges heated with two ICRF antennas simultaneously reveals the existence of beat waves at 1 kHz, as expected from the difference of the two antennas' operating frequencies. Beats are observed on both the fast and the slow wave probes suggesting that the two waves are coupled outside the active antennas. Although the new diagnostic shows consistent trends between the amplitude and the phase measurements in response to changes applied by the ICRF antennas, the disagreement with the in-air near-field measurements remains. An electromagnetic model is currently under development to address this issue.

A new B-dot probe-based diagnostic for amplitude, polarization, and wavenumber measurements of ion cyclotron range-of frequency fields on ASDEX Upgrade.

PubMed

Ochoukov, R; Bobkov, V; Faugel, H; Fünfgelder, H; Noterdaeme, J-M

2015-11-01

A new B-dot probe-based diagnostic has been installed on an ASDEX Upgrade tokamak to characterize ion cyclotron range-of frequency (ICRF) wave generation and interaction with magnetized plasma. The diagnostic consists of a field-aligned array of B-dot probes, oriented to measure fast and slow ICRF wave fields and their field-aligned wavenumber (k(//)) spectrum on the low field side of ASDEX Upgrade. A thorough description of the diagnostic and the supporting electronics is provided. In order to compare the measured dominant wavenumber of the local ICRF fields with the expected spectrum of the launched ICRF waves, in-air near-field measurements were performed on the newly installed 3-strap ICRF antenna to reconstruct the dominant launched toroidal wavenumbers (k(tor)). Measurements during a strap current phasing scan in tokamak discharges reveal an upshift in k(//) as strap phasing is moved away from the dipole configuration. This result is the opposite of the k(tor) trend expected from in-air near-field measurements; however, the near-field based reconstruction routine does not account for the effect of induced radiofrequency (RF) currents in the passive antenna structures. The measured exponential increase in the local ICRF wave field amplitude is in agreement with the upshifted k(//), as strap phasing moves away from the dipole configuration. An examination of discharges heated with two ICRF antennas simultaneously reveals the existence of beat waves at 1 kHz, as expected from the difference of the two antennas' operating frequencies. Beats are observed on both the fast and the slow wave probes suggesting that the two waves are coupled outside the active antennas. Although the new diagnostic shows consistent trends between the amplitude and the phase measurements in response to changes applied by the ICRF antennas, the disagreement with the in-air near-field measurements remains. An electromagnetic model is currently under development to address this issue.

The Position/Structure Stability of Four ICRF2 Sources

NASA Technical Reports Server (NTRS)

Fomalont, Ed; Johnston, Kenneth; Fey, Alan; Boboltz, Dave; Oyama, Tomoaki; Honma, Mareki

2010-01-01

Four compact radio sources in the International Celestial Reference Frame (ICRF2) catalog were observed using phase referencing with the VLBA at 43, 23, and 8.6-GHz, and with VERA at 23-GHz over a one-year period. The goal was to determine the stability of the radio cores and to assess structure effects associated with positions in the ICRF2. Conclusions are: (1) 43-GHz VLBI high-resolution observations are often needed to determine the location of the radio core. (2) Over the observing period, the relative positions among the four radio cores were constant to 0.02 mas, suggesting that once the true radio core is identified, it remains stationary in the sky to this accuracy. (3) The emission in 0556+238, one of the four sources investigated and one of the 295 ICRF2 defining sources, was dominated by a strong component near the core and moved 0.1 mas during the year. (4) Comparison of the VLBA images at 43, 23, and 8.6-GHz with the ICRF2 positions suggests that the 8-GHz structure is often dominated by a bright non-core component. The measured ICRF2 position can be displaced more than 0.5 mas from the radio core and partake in the motion of the bright jet component.

Development of Novel Integrated Antennas for CubeSats

NASA Technical Reports Server (NTRS)

Jackson, David; Fink, Patrick W.; Martinez, Andres; Petro, Andrew

2015-01-01

The Development of Novel Integrated Antennas for CubeSats project is directed at the development of novel antennas for CubeSats to replace the bulky and obtrusive antennas (e.g., whip antennas) that are typically used. The integrated antennas will not require mechanical deployment and thus will allow future CubeSats to avoid potential mechanical problems and therefore improve mission reliability. Furthermore, the integrated antennas will have improved functionality and performance, such as circular polarization for improved link performance, compared with the conventional antennas currently used on CubeSats.

Extending fullwave core ICRF simulation to SOL and antenna regions using FEM solver

NASA Astrophysics Data System (ADS)

Shiraiwa, S.; Wright, J. C.

2016-10-01

A full wave simulation approach to solve a driven RF waves problem including hot core, SOL plasmas and possibly antenna is presented. This approach allows for exploiting advantages of two different way of representing wave field, namely treating spatially dispersive hot conductivity in a spectral solver and handling complicated geometry in SOL/antenna region using an unstructured mesh. Here, we compute a mode set in each region with the RF electric field excitation on the connecting boundary between core and edge regions. A mode corresponding to antenna excitation is also computed. By requiring the continuity of tangential RF electric and magnetic fields, the solution is obtained as unique superposition of these modes. In this work, TORIC core spectral solver is modified to allow for mode excitation, and the edge region of diverted Alcator C-Mod plasma is modeled using COMSOL FEM package. The reconstructed RF field is similar in the core region to TORIC stand-alone simulation. However, it contains higher poloidal modes near the edge and captures a wave bounced and propagating in the poloidal direction near the vacuum-plasma boundary. These features could play an important role when the single power pass absorption is modest. This new capability will enable antenna coupling calculations with a realistic load plasma, including collisional damping in realistic SOL plasma and other loss mechanisms such as RF sheath rectification. USDoE Awards DE-FC02-99ER54512, DE-FC02-01ER54648.

Potential Refinement of the ICRF

NASA Technical Reports Server (NTRS)

Ma, Chopo

2003-01-01

The analysis and data used for the ICRF represented the state of the art in global, extragalactic, X/S band microwave astrometry in 1995. The same general analysis method was used to extend the ICRF with subsequent VLBI data in a manner consistent with the original catalog. Since 1995 there have been considerable advances in the geodetic/astrometric VLBI data set and in the analysis that would significantly improve the systematic errors, stability, and density of the next realization of the ICRS when the decision is made to take this step. In particular, data acquired since 1990, including extensive use of the VLBA, are of higher quality and astrometric utility because of changes in instrumentation, schedule design, and networks as well as specifically astrometric intent. The IVS (International VLBI Service for Geodesy and Astrometry) continues to devote a portion of its observing capability to systematic extension of the astrometric data set. Sufficient data distribution exists to select a better set of defining sources. Improvements in troposphere modeling will minimize known systematic astrometric errors while accurate modeling and estimation of station effects from loading and nonlinear motions will permit the reintegration of the celestial reference frame, terrestrial reference frame and Earth orientation parameters though a single VLBI solution. The differences between the current ICRF and the potential next realization will be described.

IVS Observation of ICRF2-Gaia Transfer Sources

NASA Astrophysics Data System (ADS)

Le Bail, K.; Gipson, J. M.; Gordon, D.; MacMillan, D. S.; Behrend, D.; Thomas, C. C.; Bolotin, S.; Himwich, W. E.; Baver, K. D.; Corey, B. E.; Titus, M.; Bourda, G.; Charlot, P.; Collioud, A.

2016-03-01

The second realization of the International Celestial Reference Frame (ICRF2), which is the current fundamental celestial reference frame adopted by the International Astronomical Union, is based on Very Long Baseline Interferometry (VLBI) data at radio frequencies in X band and S band. The European Space Agency’s Gaia mission, launched on 2013 December 19, started routine scientific operations in 2014 July. By scanning the whole sky, it is expected to observe ∼500,000 Quasi Stellar Objects in the optical domain an average of 70 times each during the five years of the mission. This means that, in the future, two extragalactic celestial reference frames, at two different frequency domains, will coexist. It will thus be important to align them very accurately. In 2012, the Laboratoire d’Astrophysique de Bordeaux (LAB) selected 195 sources from ICRF2 that will be observed by Gaia and should be suitable for aligning the radio and optical frames: they are called ICRF2-Gaia transfer sources. The LAB submitted a proposal to the International VLBI Service (IVS) to regularly observe these ICRF2-Gaia transfer sources at the same rate as Gaia observes them in the optical realm, e.g., roughly once a month. We describe our successful effort to implement such a program and report on the results. Most observations of the ICRF2-Gaia transfer sources now occur automatically as part of the IVS source monitoring program, while a subset of 37 sources requires special attention. Beginning in 2013, we scheduled 25 VLBI sessions devoted in whole or in part to measuring these 37 sources. Of the 195 sources, all but one have been successfully observed in the 12 months prior to 2015 September 01. Of the sources, 87 met their observing target of 12 successful sessions per year. The position uncertainties of all of the ICRF2-Gaia transfer sources have improved since the start of this observing program. For a subset of 24 sources whose positions were very poorly known, the uncertainty

Vehicle antenna development for mobile satellite applications

NASA Technical Reports Server (NTRS)

Woo, K.

1988-01-01

The paper summarizes results of a vehicle antenna program at JPL in support of a developing U.S. mobile satellite services (MSS) designed to provide telephone and data services for the continental United States. Two classes of circularly polarized vehicle antennas have been considered for the MSS: medium-gain, satellite-tracking antennas with 10-12-dBic gain; and low-gain, azimuthally omnidirectional antennas with 3-5-dBic gain. The design and performance of these antennas are described, and the two antennas are shown to have peculiar advantages and disadvantages.

Arc detection for the ICRF system on ITER

NASA Astrophysics Data System (ADS)

D'Inca, R.

2011-12-01

The ICRF system for ITER is designed to respect the high voltage breakdown limits. However arcs can still statistically happen and must be quickly detected and suppressed by shutting the RF power down. For the conception of a reliable and efficient detector, the analysis of the mechanism of arcs is necessary to find their unique signature. Numerous systems have been conceived to address the issues of arc detection. VSWR-based detectors, RF noise detectors, sound detectors, optical detectors, S-matrix based detectors. Until now, none of them has succeeded in demonstrating the fulfillment of all requirements and the studies for ITER now follow three directions: improvement of the existing concepts to fix their flaws, development of new theoretically fully compliant detectors (like the GUIDAR) and combination of several detectors to benefit from the advantages of each of them. Together with the physical and engineering challenges, the development of an arc detection system for ITER raises methodological concerns to extrapolate the results from basic experiments and present machines to the ITER scale ICRF system and to conduct a relevant risk analysis.

The International Celestial Reference Frame (ICRF) and the Relationship Between Frames

NASA Technical Reports Server (NTRS)

Ma, Chopo

2000-01-01

The International Celestial Reference Frame (ICRF), a catalog of VLBI source positions, is now the basis for astrometry and geodesy. Its construction and extension/maintenance will be discussed as well as the relationship of the ICRF, ITRF, and EOP/nutation.

THE POSITION/STRUCTURE STABILITY OF FOUR ICRF2 SOURCES

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

Fomalont, Ed; Johnston, Kenneth; Fey, Alan

2011-03-15

Four close radio sources in the International Celestial Reference Frame (ICRF) catalog were observed using phase referencing with the VLBA at 43, 23, and 8.6 GHz, and with VERA at 23 GHz over a one-year period. The goal was to determine the stability of the radio cores and to assess structure effects associated with positions in the ICRF. Although the four sources were compact at 8.6 GHz, the VLBA images at 43 GHz with 0.3 mas resolution showed that all were composed of several components. A component in each source was identified as the radio core using some or allmore » of the following emission properties: compactness, spectral index, location at the end of the extended emission region, and stationary in the sky. Over the observing period, the relative positions between the four radio cores were constant to 0.02 mas, the phase-referencing positional accuracy obtained at 23 and 43 GHz among the sources, suggesting that once a radio core is identified, it remains stationary in the sky to this accuracy. Other radio components in two of the four sources had detectable motion in the radio jet direction. Comparison of the 23 and 43 GHz VLBA images with the VLBA 8.6 GHz images and the ICRF positions suggests that some ICRF positions are dominated by a moving jet component; hence, they can be displaced up to 0.5 mas from the radio core and may also reflect the motion of the jet component. Future astrometric efforts to determine a more accurate quasar reference frame at 23 and 43 GHz and from the VLBI2010 project are discussed, and supporting VLBA or European VLBI Network observations of ICRF sources at 43 GHz are recommended in order to determine the internal structure of the sources. A future collaboration between the radio (ICRF) and the optical frame of GAIA is discussed.« less

A new B-dot probe-based diagnostic for amplitude, polarization, and wavenumber measurements of ion cyclotron range-of frequency fields on ASDEX Upgrade

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

Ochoukov, R.; Bobkov, V.; Faugel, H.

2015-11-15

A new B-dot probe-based diagnostic has been installed on an ASDEX Upgrade tokamak to characterize ion cyclotron range-of frequency (ICRF) wave generation and interaction with magnetized plasma. The diagnostic consists of a field-aligned array of B-dot probes, oriented to measure fast and slow ICRF wave fields and their field-aligned wavenumber (k{sub //}) spectrum on the low field side of ASDEX Upgrade. A thorough description of the diagnostic and the supporting electronics is provided. In order to compare the measured dominant wavenumber of the local ICRF fields with the expected spectrum of the launched ICRF waves, in-air near-field measurements were performedmore » on the newly installed 3-strap ICRF antenna to reconstruct the dominant launched toroidal wavenumbers (k{sub tor}). Measurements during a strap current phasing scan in tokamak discharges reveal an upshift in k{sub //} as strap phasing is moved away from the dipole configuration. This result is the opposite of the k{sub tor} trend expected from in-air near-field measurements; however, the near-field based reconstruction routine does not account for the effect of induced radiofrequency (RF) currents in the passive antenna structures. The measured exponential increase in the local ICRF wave field amplitude is in agreement with the upshifted k{sub //}, as strap phasing moves away from the dipole configuration. An examination of discharges heated with two ICRF antennas simultaneously reveals the existence of beat waves at 1 kHz, as expected from the difference of the two antennas’ operating frequencies. Beats are observed on both the fast and the slow wave probes suggesting that the two waves are coupled outside the active antennas. Although the new diagnostic shows consistent trends between the amplitude and the phase measurements in response to changes applied by the ICRF antennas, the disagreement with the in-air near-field measurements remains. An electromagnetic model is currently under

The development of inflatable array antennas

NASA Technical Reports Server (NTRS)

Huang, J.

2001-01-01

Inflatable array antennas are being developed to significantly reduce the mass, the launch vehicle's stowage volume, and the cost of future spacecraft systems. Three inflatable array antennas, recently developed for spacecraft applications, are a 3.3 m x 1.0 m L-band synthetic-aperture radar (SAR) array, a 1.0 m-diameter X-band telecom reflectarray, and a 3 m-diameter Ka-band telecom reflectarray. All three antennas are similar in construction, and each consists of an inflatable tubular frame that supports and tensions a multi-layer thin-membrane RF radiating surface with printed microstrip patches. The L-band SAR array achieved a bandwidth of 80 MHz, an aperture efficiency of 74%, and a total mass of 15 kg. The X-band reflectarray achieved an aperture efficiency of 37%, good radiation patterns, and a total mass of 1.2 kg (excluding the inflation system). The 3 m Ka-band reflectarray achieved a surface flatness of 0.1 mm RMS, good radiation patterns, and a total mass of 12.8 kg (excluding the inflation system). These antennas demonstrated that inflatable arrays are feasible across the microwave and millimeter-wave spectrums. Further developments of these antennas are deemed necessary, in particular, in the area of qualifying the inflatable structures for space-environment usage.

ASDE-3 Antenna Development and Test

DOT National Transportation Integrated Search

1981-01-01

The ASDE-3 radar antenna was developed so that closely spaced targets on an airport surface could be resolved. The requirement of accurately detecting targets as close as 500 feet from the antenna necessitated some type of near field focussing. A var...

VizieR Online Data Catalog: Radio fluxes of 195 ICRF2-Gaia transfer sources (Le Bail+, 2016)

NASA Astrophysics Data System (ADS)

Le Bail, K.; Gipson, J. M.; Gordon, D.; MacMillan, D. S.; Behrend, D.; Thomas, C. C.; Bolotin, S.; Himwich, W. E.; Baver, K. D.; Corey, B. E.; Titus, M.; Bourda, G.; Charlot, P.; Collioud, A.

2016-07-01

The second realization of the International Celestial Reference Frame (ICRF2) is based on Very Long Baseline Interferometry (VLBI) data at radio frequencies in X band and S band. The European Space Agency's Gaia mission, launched on 2013 December 19, started routine scientific operations in 2014 July. By scanning the whole sky, it is expected to observe ~500000 Quasi Stellar Objects in the optical domain. This means that, in the future, two extragalactic celestial reference frames, at two different frequency domains, will coexist. It will thus be important to align them very accurately. In 2012, the Laboratoire d'Astrophysique de Bordeaux (LAB) selected 195 sources from ICRF2 that will be observed by Gaia and should be suitable for aligning the radio and optical frames: they are called ICRF2-Gaia transfer sources. The LAB submitted a proposal to the International VLBI Service (IVS) to regularly observe these ICRF2-Gaia transfer sources at the same rate as Gaia observes them in the optical realm, e.g., roughly once a month. Of the 195 sources, all but one have been successfully observed in the 12 months prior to 2015 September 01. Table1 lists the 195 ICRF2-Gaia transfer sources. Beginning in 2003 June, the Goddard VLBI group developed a program to purposefully monitor when sources were observed and to increase the observations of "under-observed" sources. In 2013 March, we added all 195 ICRF2-Gaia transfer sources to the IVS source monitoring program with an observation target of 12 successful sessions per year. (1 data file).

Global Confinement, Sawtooth Mixing, and Stochastic Diffusion Ripple Loss of Fast ICRF-driven H+ Minority Ions in TFTR

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

Petrov, M.P.; Bell, R.; Budny, R.V.

1998-07-01

This paper presents studies of ICRF-driven H+ minority ions in TFTR (Tokamak Fusion Test Reator) deuterium plasmas using primarily passive Ho flux detection in the energy range of 0.2-1.0 MeV with some corroborating active (lithium pellet charge exchange) measurements. It is shown that in the passive mode the main donors for the neutralization of H+ ions in this energy range are C5+ ions. The measured effective H+ tail temperatures range from 0.15 MeV at an ICRF power of 2 MW to 0.35 MeV at 6 MW. Analysis of the ICRF-driven H+ ion energy balance has been performed on the basismore » of the dependence of effective H+ temperatures on the plasma parameters. The analysis showed that H+ confinement times are comparable with their slowing-down times and tended to decrease with increasing ICRF power. Radial redistribution of ICRF-driven H+ ions was detected when giant sawtooth crashes occurred during the ICRF heating. The redistribution affected ions with energy below 0.7-0.8 MeV. The sawtooth crashes displace H+ ions outward along the plasma major radius into the stochastic ripple diffusion domain were those ions are lost in about 10 milliseconds. These observations are consistent with the model of the redistribution of energetic particles developed previously to explain the results of deuterium-tritium alpha-particle redistribution due to sawteeth observed in TFTR. The experimental data are also consistent with ORBIT code simulations of H+ stochastic ripple diffusion losses.« less

Interleaved array antenna technology development

NASA Technical Reports Server (NTRS)

1985-01-01

This is the third phase of a program to establish an antenna concept for shuttle and free flying spacecraft earth resources experiments using Synthetic Aperture Radar. The feasibility of a plated graphite epoxy waveguide for a space antenna was evaluated. A quantity of flat panels and waveguides were developed, procured, and tested for electrical and mechanical properties. In addition, processes for the assembly of a unique waveguide array were investigated. Finally, trades between various configurations that would allow elevation (range) electronic scanning and that would minimize feed complexity for various RF bandwidths were made.

The interaction of the near-field plasma with antennas used in magnetic fusion research

NASA Astrophysics Data System (ADS)

Caughman, John

2015-09-01

Plasma heating and current drive using antennas in the Ion Cyclotron Range of Frequencies (ICRF) are important elements for the success of magnetic fusion. The antennas must operate in a harsh environment, where local plasma densities can be >1018/m3, magnetic fields can range from 0.2-5 Tesla, and antenna operating voltages can be >40 kV. This environment creates operational issues due to the interaction of the near-field of the antenna with the local plasma. In addition to parasitic losses in this plasma region, voltage and current distributions on the antenna structure lead to the formation of high electric fields and RF plasma sheaths, which can lead to enhanced particle and energy fluxes on the antenna and on surfaces intersected by magnetic field lines connected to or passing near the antenna. These issues are being studied using a simple electrode structure and a single-strap antenna on the Prototype Materials Plasma EXperiment (Proto-MPEX) at ORNL, which is a linear plasma device that uses an electron Bernstein wave heated helicon plasma source to create a high-density plasma suitable for use in a plasma-material interaction test stand. Several diagnostics are being used to characterize the near-field interactions, including double-Langmuir probes, a retarding field energy analyzer, and optical emission spectroscopy. The RF electric field is being studied utilizing Dynamic Stark Effect spectroscopy and Doppler-Free Saturation Spectroscopy. Recent experimental results and future plans will be presented. ORNL is managed by UT-Battelle, LLC, for the U.S. DOE under Contract DE-AC-05-00OR22725.

Design and development of conformal antenna composite structure

NASA Astrophysics Data System (ADS)

Xie, Zonghong; Zhao, Wei; Zhang, Peng; Li, Xiang

2017-09-01

In the manufacturing process of the common smart skin antenna, the adhesive covered on the radiating elements of the antenna led to severe deviation of the resonant frequency, which degraded the electromagnetic performance of the antenna. In this paper, a new component called package cover was adopted to prevent the adhesive from covering on the radiating elements of the microstrip antenna array. The package cover and the microstrip antenna array were bonded together as packaged antenna which was then embedded into the composite sandwich structure to develop a new structure called conformal antenna composite structure (CACS). The geometric parameters of the microstrip antenna array and the CACS were optimized by the commercial software CST microwave studio. According to the optimal results, the microstrip antenna array and the CACS were manufactured and tested. The experimental and numerical results of electromagnetic performance showed that the resonant frequency of the CACS was close to that of the microstrip antenna array (with error less than 1%) and the CACS had a higher gain (about 2 dB) than the microstrip antenna array. The package system would increase the electromagnetic radiating energy at the design frequency nearly 66%. The numerical model generated by CST microwave studio in this study could successfully predict the electromagnetic performance of the microstrip antenna array and the CACS with relatively good accuracy. The mechanical analysis results showed that the CACS had better flexural property than the composite sandwich structure without the embedment of packaged antenna. The comparison of the electromagnetic performance for the CACS and the MECSSA showed that the package system was useful and effective.

Microstrip antenna developments at JPL

NASA Technical Reports Server (NTRS)

Huang, John

1991-01-01

The in-house development of microstrip antennas, initiated in 1981, when a spaceborne lightweight and low-profile planar array was needed for a satellite communication system, is described. The work described covers the prediction of finite-ground-plane effects by the geometric theory of diffraction, higher-order-mode circularly polarized circular patch antennas, circularly polarized microstrip arrays with linearly polarized elements, an impedance-matching teardrop-shaped probe feed, a dual-polarized microstrip array with high isolation and low cross-polarization, a planar microstrip Yagi array, a microstrip reflectarray, a Ka-band MMIC array, and a series-fed linear arrays.

Broadband standard dipole antenna for antenna calibration

NASA Astrophysics Data System (ADS)

Koike, Kunimasa; Sugiura, Akira; Morikawa, Takao

1995-06-01

Antenna calibration of EMI antennas is mostly performed by the standard antenna method at an open-field test site using a specially designed dipole antenna as a reference. In order to develop broadband standard antennas, the antenna factors of shortened dipples are theoretically investigated. First, the effects of the dipole length are analyzed using the induced emf method. Then, baluns and loads are examined to determine their influence on the antenna factors. It is found that transformer-type baluns are very effective for improving the height dependence of the antenna factors. Resistive loads are also useful for flattening the frequency dependence. Based on these studies, a specification is developed for a broadband standard antenna operating in the 30 to 150 MHz frequency range.

Fast-ion distributions from third harmonic ICRF heating studied with neutron emission spectroscopy

NASA Astrophysics Data System (ADS)

Hellesen, C.; Gatu Johnson, M.; Andersson Sundén, E.; Conroy, S.; Ericsson, G.; Eriksson, J.; Sjöstrand, H.; Weiszflog, M.; Johnson, T.; Gorini, G.; Nocente, M.; Tardocchi, M.; Kiptily, V. G.; Pinches, S. D.; Sharapov, S. E.; EFDA Contributors, JET

2013-11-01

The fast-ion distribution from third harmonic ion cyclotron resonance frequency (ICRF) heating on the Joint European Torus is studied using neutron emission spectroscopy with the time-of-flight spectrometer TOFOR. The energy dependence of the fast deuteron distribution function is inferred from the measured spectrum of neutrons born in DD fusion reactions, and the inferred distribution is compared with theoretical models for ICRF heating. Good agreements between modelling and measurements are seen with clear features in the fast-ion distribution function, that are due to the finite Larmor radius of the resonating ions, replicated. Strong synergetic effects between ICRF and neutral beam injection heating were also seen. The total energy content of the fast-ion population derived from TOFOR data was in good agreement with magnetic measurements for values below 350 kJ.

The behavior of neutron emissions during ICRF minority heating of plasma at EAST

NASA Astrophysics Data System (ADS)

Zhong, Guoqiang; Cao, Hongrui; Hu, Liqun; Zhou, Ruijie; Xiao, Min; Li, Kai; Pu, Neng; Huang, Juan; Liu, Guangzhu; Lin, Shiyao; Lyu, Bo; Liu, Haiqing; Zhang, Xinjun; EAST Team

2016-07-01

Ion cyclotron radio frequency (ICRF) wave heating is a primary method to heat ions in the Experimental Advanced Superconducting Tokamak (EAST). Through neutron diagnostics, effective ion heating was observed in hydrogenminority heating (MH) scenarios. At present, investigation of deuterium-deuterium (DD) fusion neutrons is mostly based on time-resolved flux monitor and spectrometer measurements. When the ICRF was applied, the neutron intensity became one order higher. The H/H  +  D ratio was in the range of 5-10%, corresponding to the hydrogen MH dominated scenario, and a strong high energy tail was not displayed on the neutron spectrum that was measured by a liquid scintillator. Moreover, ion temperature in the plasma center (T i) was inversely calculated by the use of neutron source strength (S n) and the plasma density based on classical fusion reaction equations. This result indicates that T i increases by approximately 30% in L-mode plasma, and by more than 50% in H-mode plasma during ICRF heating, which shows good agreement with x-ray crystal spectrometer (XCS) diagnostics. Finally, the DD neutron source strength scaling law, with regard to plasma current (I P) and ICRF coupling power (P RF) on the typical minority heating condition, was obtained by statistical analysis.

Ferroelectric/Semiconductor Tunable Microstrip Patch Antenna Developed

NASA Technical Reports Server (NTRS)

Romanofsky, Robert R.

2001-01-01

A lithographically printed microwave antenna that can be switched and tuned has been developed. The structure consists of a rectangular metallic "patch" radiator patterned on a thin ferroelectric film that was grown on high-resistivity silicon. Such an antenna may one day enable a single-phased array aperture to transmit and receive signals at different frequencies, or it may provide a simple way to reconfigure fractal arrays for communications and radar applications.

WRAP-RIB antenna technology development

NASA Technical Reports Server (NTRS)

Freeland, R. E.; Garcia, N. F.; Iwamoto, H.

1985-01-01

The wrap-rib deployable antenna concept development is based on a combination of hardware development and testing along with extensive supporting analysis. The proof-of-concept hardware models are large in size so they will address the same basic problems associated with the design fabrication, assembly and test as the full-scale systems which were selected to be 100 meters at the beginning of the program. The hardware evaluation program consists of functional performance tests, design verification tests and analytical model verification tests. Functional testing consists of kinematic deployment, mesh management and verification of mechanical packaging efficiencies. Design verification consists of rib contour precision measurement, rib cross-section variation evaluation, rib materials characterizations and manufacturing imperfections assessment. Analytical model verification and refinement include mesh stiffness measurement, rib static and dynamic testing, mass measurement, and rib cross-section characterization. This concept was considered for a number of potential applications that include mobile communications, VLBI, and aircraft surveillance. In fact, baseline system configurations were developed by JPL, using the appropriate wrap-rib antenna, for all three classes of applications.

A technology development program for large space antennas

NASA Technical Reports Server (NTRS)

Russell, R. A.; Campbell, T. G.; Freeland, R. E.

1980-01-01

The design and application of the offset wrap rib and the maypole (hoop/column) antenna configurations are described. The NASA mission model that generically categorizes the classes of user requirements, as well as the methods used to determine critical technologies and requirements are discussed. Performance estimates for the mesh deployable antenna selected for development are presented.

Multi-frequency ICRF diagnostic of Tokamak plasmas

NASA Astrophysics Data System (ADS)

Lafonteese, David James

This thesis explores the diagnostic possibilities of a fast wave-based method for measuring the ion density and temperature profiles of tokamak plasmas. In these studies fast waves are coupled to the plasma at frequencies at the second harmonic of the ion gyrofrequency, at which wave energy is absorbed by the finite-temperature ions. As the ion gyrofrequency is dependent upon the local magnetic field, which varies as l/R in a tokamak, this power absorption is radially localized. The simultaneous launching of multiple frequencies, all resonating at different plasma positions, allows local measurements of the ion density and temperature. To investigate the profile applications of wave damping measurements in a simulated tokamak, an inhouse slab-model ICRF code is developed. A variety of analysis methods are presented, and ion density and temperature profiles are reconstructed for hydrogen plasmas for the Electric Tokamak (ET) and ITER parameter spaces. These methods achieve promising results in simulated plasmas featuring bulk ion heating, off-axis RF heating, and density ramps. The experimental results of similar studies on the Electric Tokamak, a high aspect ratio (R/a = 5), low toroidal field (2.2 kG) device are then presented. In these studies, six fast wave frequencies were coupled using a single-strap, low-field-side antenna to ET plasmas. The frequencies were variable, and could be tuned to resonate at different radii for different experiments. Four magnetic pickup loops were used to measure of the toroidal component of the wave magnetic field. The expected greater eigenmode damping of center-resonant frequencies versus edge-resonant frequencies is consistently observed. Comparison of measured aspects of fast wave behavior in ET is made with the slab code predictions, which validate the code simulations under weakly-damped conditions. A density profile is measured for an ET discharge through analysis of the fast wave measurements, and is compared to an

Long-Term Variations of the EOP and ICRF2

NASA Technical Reports Server (NTRS)

Zharov, Vladimir; Sazhin, Mikhail; Sementsov, Valerian; Sazhina, Olga

2010-01-01

We analyzed the time series of the coordinates of the ICRF radio sources. We show that part of the radio sources, including the defining sources, shows a significant apparent motion. The stability of the celestial reference frame is provided by a no-net-rotation condition applied to the defining sources. In our case this condition leads to a rotation of the frame axes with time. We calculated the effect of this rotation on the Earth orientation parameters (EOP). In order to improve the stability of the celestial reference frame we suggest a new method for the selection of the defining sources. The method consists of two criteria: the first one we call cosmological and the second one kinematical. It is shown that a subset of the ICRF sources selected according to cosmological criteria provides the most stable reference frame for the next decade.

From core to coax: extending core RF modelling to include SOL, Antenna, and PFC

NASA Astrophysics Data System (ADS)

Shiraiwa, Syun'ichi

2017-10-01

A new technique for the calculation of RF waves in toroidal geometry enables the simultaneous incorporation of antenna geometry, plasma facing components (PFCs), the scrape off-layer (SOL), and core propagation. Traditionally, core RF wave propagation and antenna coupling has been calculated separately both using rather simplified SOL plasmas. The new approach, instead, allows capturing wave propagation in the SOL and its interactions with non-conforming PFCs permitting self-consistent calculation of core absorption and edge power loss, as well as investigating far and near field impurity generation from RF sheaths and a breakdown issue from antenna electric fields. Our approach combines the field solutions obtained from a core spectral code with a hot plasma dielectric and an edge FEM code using a cold plasma approximation via surface admittance-like matrix. Our approach was verified using the TORIC core ICRF spectral code and the commercial COMSOL FEM package, and was extended to 3D torus using open-source scalable MFEM library. The simulation result revealed that as the core wave damping gets weaker, the wave absorption in edge could become non-negligible. Three dimensional capabilities with non axisymmetric edge are being applied to study the antenna characteristic difference between the field aligned and toroidally aligned antennas on Alcator C-Mod, as well as the surface wave excitation on NSTX-U. Work supported by the U.S. DoE, OFES, using User Facility Alcator C-Mod, DE-FC02-99ER54512 and Contract No. DE-FC02-01ER54648.

Electronic Warfare Closed Loop Laboratory (EWCLL) Antenna Motor Software and Hardware Development

DTIC Science & Technology

2016-09-01

ARL-TN-0779 ● SEP 2016 US Army Research Laboratory Electronic Warfare Closed Loop Laboratory (EWCLL) Antenna Motor Software and...Electronic Warfare Closed Loop Laboratory (EWCLL) Antenna Motor Software and Hardware Development by Neal Tesny Sensors and Electron Devices Directorate...TITLE AND SUBTITLE Electronic Warfare Closed Loop Laboratory (EWCLL) Antenna Motor Software and Hardware Development 5a. CONTRACT NUMBER 5b

Phased Array Antenna Testbed Development at the NASA Glenn Research Center

NASA Technical Reports Server (NTRS)

Lambert, Kevin M.; Kubat, Gregory; Johnson, Sandra K.; Anzic, Godfrey

2003-01-01

Ideal phased array antennas offer advantages for communication systems, such as wide-angle scanning and multibeam operation, which can be utilized in certain NASA applications. However, physically realizable, electronically steered, phased array antennas introduce additional system performance parameters, which must be included in the evaluation of the system. The NASA Glenn Research Center (GRC) is currently conducting research to identify these parameters and to develop the tools necessary to measure them. One of these tools is a testbed where phased array antennas may be operated in an environment that simulates their use. This paper describes the development of the testbed and its use in characterizing a particular K-Band, phased array antenna.

Allowing for Slow Evolution of Background Plasma in the 3D FDTD Plasma, Sheath, and Antenna Model

NASA Astrophysics Data System (ADS)

Smithe, David; Jenkins, Thomas; King, Jake

2015-11-01

We are working to include a slow-time evolution capability for what has previously been the static background plasma parameters, in the 3D finite-difference time-domain (FDTD) plasma and sheath model used to model ICRF antennas in fusion plasmas. A key aspect of this is SOL-density time-evolution driven by ponderomotive rarefaction from the strong fields in the vicinity of the antenna. We demonstrate and benchmark a Scalar Ponderomotive Potential method, based on local field amplitudes, which is included in the 3D simulation. And present a more advanced Tensor Ponderomotive Potential approach, which we hope to employ in the future, which should improve the physical fidelity in the highly anisotropic environment of the SOL. Finally, we demonstrate and benchmark slow time (non-linear) evolution of the RF sheath, and include realistic collisional effects from the neutral gas. Support from US DOE Grants DE-FC02-08ER54953, DE-FG02-09ER55006.

High Voltage Test-Stand Research Done on ICRF Antenna Elements of the High-Harmonic Fast-Wave System of NSTX

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

Perkins, R. J.; Ahn, J.W.; Bortolon, A.

The twelve-strap high-harmonic fast-wave (HHFW) antenna on NSTX has exhibited a high-voltage standoff around 25 kV during previous experimental campaigns; this standoff needs to be improved for increased power coupling. During the recent NSTX-U upgrade period, a test-stand was set up with two antenna straps along with Faraday screens for testing purposes. Using a diagnostic suite consisting of a fast camera, a residual gas analyzer, a pressure gage, high-voltage probes, and an infrared camera, several interesting discoveries were made, leading to possible improvements of the antenna RF voltage operation level. First, arcing was observed outside the Faraday shields towards themore » low-voltage ("grounded") end of the straps (faraday shield box ends); this arcing was successfully eliminated by installing an additional grounding point between the Faraday shield box and the vessel wall. Second, considerable outgassing was observed during the RF pulse and the amount of outgassing was found to decrease with increasing RF power, possibly indicative of multipacting. Finally, infrared camera measurements of heating on the Faraday shield assembly suggest that the return currents on the Faraday shield box are highly localized at the box sides and possibly account for the pressure increase observed. Computations of these RF currents using Microwave Studio show qualitative agreement with the heated regions. New grounding points between the antenna box and the vessel have been implemented in NSTX-U, where future tests will be done to determine if the high-voltage standoff has improved. Further antenna improvements will be sought through future experiments on the test stand.« less

Developing novel 3D antennas using advanced additive manufacturing technology

NASA Astrophysics Data System (ADS)

Mirzaee, Milad

In today's world of wireless communication systems, antenna engineering is rapidly advancing as the wireless services continue to expand in support of emerging commercial applications. Antennas play a key role in the performance of advanced transceiver systems where they serve to convert electric power to electromagnetic waves and vice versa. Researchers have held significant interest in developing this crucial component for wireless communication systems by employing a variety of design techniques. In the past few years, demands for electrically small antennas continues to increase, particularly among portable and mobile wireless devices, medical electronics and aerospace systems. This trend toward smaller electronic devices makes the three dimensional (3D) antennas very appealing, since they can be designed in a way to use every available space inside the devise. Additive Manufacturing (AM) method could help to find great solutions for the antennas design for next generation of wireless communication systems. In this thesis, the design and fabrication of 3D printed antennas using AM technology is studied. To demonstrate this application of AM, different types of antennas structures have been designed and fabricated using various manufacturing processes. This thesis studies, for the first time, embedded conductive 3D printed antennas using PolyLactic Acid (PLA) and Acrylonitrile Butadiene Styrene (ABS) for substrate parts and high temperature carbon paste for conductive parts which can be a good candidate to overcome the limitations of direct printing on 3D surfaces that is the most popular method to fabricate conductive parts of the antennas. This thesis also studies, for the first time, the fabrication of antennas with 3D printed conductive parts which can contribute to the new generation of 3D printed antennas.

NASA's Mobile and Telecom Antenna Development at JPL

NASA Technical Reports Server (NTRS)

Huang, John

1997-01-01

Chartered by NASA to develop and demonstrate enabling technologies for mobile and satellite telecommuniation systems, JPL has developed various antenna technologies throughout the microwave spectrum in the past two decades.

Northern Hemisphere observations of ICRF sources on the USNO stellar catalogue frame

NASA Astrophysics Data System (ADS)

Fienga, A.; Andrei, A. H.

2004-06-01

The most recent USNO stellar catalogue, the USNO B1.0 (Monet et al. \\cite{Monet03}), provides positions for 1 042 618 261 objects, with a published astrometric accuracy of 200 mas and five-band magnitudes with a 0.3 mag accuracy. Its completeness is believed to be up to magnitude 21th in V-band. Such a catalogue would be a very good tool for astrometric reduction. This work investigates the accuracy of the USNO B1.0 link to ICRF and give an estimation of its internal and external accuracies by comparison with different catalogues, and by computation of ICRF sources using USNO B1.0 star positions.

Progress on ion cyclotron range of frequencies heating physics and technology in support of the International Tokamak Experimental Reactor

NASA Astrophysics Data System (ADS)

Wilson, J. R.; Bonoli, P. T.

2015-02-01

Ion cyclotron range of frequency (ICRF) heating is foreseen as an integral component of the initial ITER operation. The status of ICRF preparations for ITER and supporting research were updated in the 2007 [Gormezano et al., Nucl. Fusion 47, S285 (2007)] report on the ITER physics basis. In this report, we summarize progress made toward the successful application of ICRF power on ITER since that time. Significant advances have been made in support of the technical design by development of new techniques for arc protection, new algorithms for tuning and matching, carrying out experimental tests of more ITER like antennas and demonstration on mockups that the design assumptions are correct. In addition, new applications of the ICRF system, beyond just bulk heating, have been proposed and explored.

Scrape-off layer reflectometer for Alcator C-Mod.

PubMed

Hanson, G R; Wilgen, J B; Lau, C; Lin, Y; Wallace, G M; Wukitch, S J

2008-10-01

A two-frequency x-mode reflectometer operating from 100 to 146 GHz is deployed on Alcator C-Mod to measure the density profile and fluctuations in the scrape-off layer (SOL) immediately in front of the new J-port ICRF antenna and the new C-port lower hybrid launcher. The reflectometer covers densities from 10(16) to 10(20) m(-3) at 5-5.4 T. To provide the greatest flexibility and capability to deal with density fluctuations approaching 100% peak-to-peak in the SOL, both full-phase and differential-phase measurement capabilities with sweep speeds of approximately 10 micros to >1 ms are implemented. The differential-phase measurement uses a difference frequency of 500 MHz, corresponding to cutoff layer separations ranging from about 0.1 to 1 mm. The reflectometer has six sets of launchers: three on the ICRF antenna and three on the lower hybrid launcher. Both the ICRF antenna and the lower hybrid launcher incorporate reflectometer antennas at their top, bottom, and midplane locations.

AAFE large deployable antenna development program: Executive summary

NASA Technical Reports Server (NTRS)

1977-01-01

The large deployable antenna development program sponsored by the Advanced Applications Flight Experiments of the Langley Research Center is summarized. Projected user requirements for large diameter deployable reflector antennas were reviewed. Trade-off studies for the selection of a design concept for 10-meter diameter reflectors were made. A hoop/column concept was selected as the baseline concept. Parametric data are presented for 15-meter, 30-meter, and 100-meter diameters. A 1.82-meter diameter engineering model which demonstrated the feasiblity of the concept is described.

User Antennas

NASA Technical Reports Server (NTRS)

Jamnejad, Vahraz; Cramer, Paul

1990-01-01

The following subject areas are covered: (1) impact of frequency change of user and spacecraft antenna gain and size; (2) basic personal terminal antennas (impact of 20/30 GHz frequency separation; parametric studies - gain, size, weight; gain and figure of merit (G/T); design data for selected antenna concepts; critical technologies and development goals; and recommendations); and (3) user antenna radiation safety concerns.

Space station high gain antenna concept definition and technology development

NASA Technical Reports Server (NTRS)

Wade, W. D.

1972-01-01

The layout of a technology base is reported from which a mechanically gimballed, directional antenna can be developed to support a manned space station proposed for the late 1970's. The effort includes the concept definition for the antenna assembly, an evaluation of available technology, the design of critical subassemblies and the design of critical subassembly tests.

Development of a Gimballed, dual frequency, space-based, microwave antenna for volume production

NASA Technical Reports Server (NTRS)

Leckie, Martin; Laidig, Dave

1996-01-01

A dual-frequency, two-axis Gimballed, Microwave Antenna (GMA) has been developed by COM DEV and Motorola for commercial satellites. The need for volume production of over three hundred antennas at a rate of four per week, a compressed development schedule, and the commercial nature of the effort necessitated a paradigm shift to an 'overall' cost-driven design approach. The translation of these demands into antenna requirements, a description of the resulting GMA design, and examples of development issues are detailed herein.

The Seasat scanning multichannel microwave radiometer /SMMR/: Antenna pattern corrections - Development and implementation

NASA Technical Reports Server (NTRS)

Njoku, E. G.; Christensen, E. J.; Cofield, R. E.

1980-01-01

The antenna temperatures measured by the Seasat scanning multichannel microwave radiometer (SMMR) differ from the true brightness temperatures of the observed scene due to antenna pattern effects, principally from antenna sidelobe contributions and cross-polarization coupling. To provide accurate brightness temperatures convenient for geophysical parameter retrievals the antenna temperatures are processed through a series of stages, collectively known as the antenna pattern correction (APC) algorithm. A description of the development and implementation of the APC algorithm is given, along with an error analysis of the resulting brightness temperatures.

Linking Deep Astrometric Standards to the ICRF

NASA Astrophysics Data System (ADS)

Frey, S.; Platais, I.; Fey, A. L.

2007-07-01

The next-generation large aperature and large field-of-view telescopes will address fundamantal questions of astrophysica and cosmology such as the nature of dark matter and dark energy. For a variety of applications, the CCD mosaic detectors in the focal plane arrays require astronomic calibrationat the milli-arcsecond (mas) level. The existing optical reference frames are insufficient to support such calibrations. To address this problem, deep optical astronomic fields are being established near the Galactic plane. In order to achiev a 5-10-mas or better positional accuracyfor the Deepp Astrometric Standards (DAS), and to obtain bsolute stellar proper motions for the study of Galactic structure, it is crucial to link these fields to the International Celestial Reference Frame (ICRF). To this end, we selected 15 candidate compact extragalactic radio sources in the Gemini-Orion-Taurus (GOT) field. These sources were observed with the European VLBI Network (EVN) at 5 GHz in phase-reference mode. The bright compact calibrator source J0603+2159 and seven other sources were detected and imaged at the angular resolution of -1.5-8 mas. Relative astrometric positions were derived for these sources at a milli-arcsecond accuracy level. The detection of the optical counterparts of these extragalactic radio sources will allow us to establish a direct link to the ICRF locally in the GOT field.

Development of an Ultra-Wideband Circularly Polarized Multiple Layer Dielectric Rod Antenna Design

NASA Astrophysics Data System (ADS)

Wainwright, Gregory D.

This dissertations focuses on the development of a novel Ultra-Wideband (UWB) circularly polarized dielectric rod antenna (CPDRA) which yields a constant gain, pattern, and phase center. These properties are important in many applications. Within radar systems a constant phase center is desirable to avoid errors within downrange and crossrange measurements. In a reflector antenna the illumination, spillover, and phase efficiencies will remain the same over an ultra-wideband. Lastly, near field probes require smooth amplitude and phase patterns over frequency to avoid errors during the calibration process of the antenna under test. In this dissertation a novel CP feeding network has been developed for an ultra-wideband dielectric rod antenna. Circularly-polarized antennas have a major advantage over its linearly-polarized counterpart in that the polarization mismatch loss caused by misalignment between the polarizations of the incident fields and antenna can be avoided. This is important in satellite communications and broadcasts where signal propagation through the ionosphere can experience Faraday Rotation. A circularly polarized antenna is also helpful in mobile radar and communication systems where the receiving antennas orientation is not fixed. Previous research on UWB dielectric rod antenna designs has focused on Dual linear feeds. Each polarization within the dual linear feed is excited by a pair of linear launcher arms fed with a 0°-180° hybrid balun. The proposed CPDRA design does not require the 0°-180° hybrid baluns or 0°-90° hybrid for achieving CP operation. These hybrids will increase the antennas size, weight, cost, and reduce operational bandwidth. A design technique has been developed for an UWB multilayer dielectric waveguide used in a CPDRA antenna. This design technique uses near-field Electric field data from inside the waveguide, in conjunction with a genetic algorithm optimization to yield a wideband waveguide with a near field

A Complete Bank of Optical Images of the ICRF QSOs

NASA Astrophysics Data System (ADS)

Humberto Andrei, Alexandre; Taris, Francois; Anton, Sonia; Bourda, Geraldine; Damljanovic, Goran; Souchay, Jean; Vieira Martins, Roberto; Pursimo, Tapio; Barache, Christophe; Nepomuceno da Silva Neto, Dario; Fernandes Coelho, Bruno David

2015-08-01

We have been developing a systematic effort to collect good quality images of the optical counterpart of ICRF sources, in particular for those that have been regularly radio surveyed either for future implementation at high frequencies and/or those that will be the link sources between the ICRF and the Gaia CRF. Observations have been taken at the LNA/Brazil, CASLEO/Argentina, NOT/Spain, LFOA/Austria, Rozhen/Bulgária, and ASV/Serbia. In complement images were collected from the SDSS. As a step to implement such image data bank and make it publicly available through the IERS service we present its description, that comprises for each source the number of measurements, filter, pixel scale, size of field, and seeing at each observation. The photometry analysis is centered on the morphology, since there remain still cases in which the host galaxy is overwhelming, and many cases in which the host asks for a non-stellar PSF modeling. On basis of the neighbor stars we assign magnitudes and variability whenever possible. Finally, assisted by previous literature, the redshift and luminosity are used to derive astrophysical quantities, in special the absolute magnitude, SED and spectral index. Moreover, since Gaia will not obtain direct images of the observed sources, the morphology and magnitude becomes useful as templates onto which assembling and interpreting the one-dimensional and uncontinuous line spread function samplings that will be delivered by Gaia for each QSO.

Optical Spectra of Candidate International Celestial Reference Frame (ICRF) Flat-spectrum Radio Sources. III.

NASA Astrophysics Data System (ADS)

Titov, O.; Pursimo, T.; Johnston, Helen M.; Stanford, Laura M.; Hunstead, Richard W.; Jauncey, David L.; Zenere, Katrina A.

2017-04-01

In extending our spectroscopic program, which targets sources drawn from the International Celestial Reference Frame (ICRF) Catalog, we have obtained spectra for ˜160 compact, flat-spectrum radio sources and determined redshifts for 112 quasars and radio galaxies. A further 14 sources with featureless spectra have been classified as BL Lac objects. Spectra were obtained at three telescopes: the 3.58 m European Southern Observatory New Technology Telescope, and the two 8.2 m Gemini telescopes in Hawaii and Chile. While most of the sources are powerful quasars, a significant fraction of radio galaxies is also included from the list of non-defining ICRF radio sources.

Optical Spectra of Candidate International Celestial Reference Frame (ICRF) Flat-spectrum Radio Sources. III

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

Titov, O.; Stanford, Laura M.; Pursimo, T.

In extending our spectroscopic program, which targets sources drawn from the International Celestial Reference Frame (ICRF) Catalog, we have obtained spectra for ∼160 compact, flat-spectrum radio sources and determined redshifts for 112 quasars and radio galaxies. A further 14 sources with featureless spectra have been classified as BL Lac objects. Spectra were obtained at three telescopes: the 3.58 m European Southern Observatory New Technology Telescope, and the two 8.2 m Gemini telescopes in Hawaii and Chile. While most of the sources are powerful quasars, a significant fraction of radio galaxies is also included from the list of non-defining ICRF radiomore » sources.« less

Advanced Microstrip Antenna Developments : Volume II. Microstrip GPS Antennas for General Aviation Aircraft

DOT National Transportation Integrated Search

1982-03-01

This report describes the application of microstrip antenna technology to the design of general aviation (G/A) aircraft antennas for use with the Global Positioning System (GPS). For most G/A aircraft, only single frequency operation will be required...

Interleaved arrays antenna technology development

NASA Technical Reports Server (NTRS)

1986-01-01

Phase one and two of a program to further develop and investigate advanced graphite epoxy waveguides, radiators, and components with application to space antennas are discussed. The objective of the two phases were to demonstrate mechanical integrity of a small panel of radiators and parts procured under a previous contract and to develop alternate designs and applications of the technology. Most of the emphasis was on the assembly and test of a 5 x 5 element module. This effort was supported by evaluation of adhesives and waveguide joint configurations. The evaluation and final assembly considered not only mechanical performance but also producibility in large scale.

Development and coupling analysis of active skin antenna

NASA Astrophysics Data System (ADS)

Zhou, Jinzhu; Huang, Jin; He, Qingqang; Tang, Baofu; Song, Liwei

2017-02-01

An active skin antenna is a multifunctional composite structure that can provide load-bearing structure and steerable beam pointing functions, and is usually installed in the structural surface of aircraft, warships, and armored vehicles. This paper presents an innovative design of the active skin antenna, which consists of a package layer, control and signal processing layer, and RF (radio frequency) layer. The RF layer is fabricated by low temperature co-fired ceramics, with 64 microstrip antenna elements, tile transmitting and receiving modules, microchannel heat sinks, and feeding networks integrated into a functional block 2.8 mm thick. In this paper, a full-sized prototype of an active skin antenna was designed, fabricated, and tested. Moreover, a coupling analysis method was presented to evaluate the mechanical and electromagnetic performance of the active skin antenna subjected to aerodynamic loads. A deformed experimental system was built to validate the effectiveness of the coupling analysis method, which was also implemented to evaluate the performance of the active skin antenna when subjected to aerodynamic pressure. The fabricated specimen demonstrated structural configuration feasibility, and superior environmental load resistance.

Methodology for Designing and Developing a New Ultra-Wideband Antenna Based on Bio-Inspired Optimization Techniques

DTIC Science & Technology

2017-11-01

ARL-TR-8225 ● NOV 2017 US Army Research Laboratory Methodology for Designing and Developing a New Ultra-Wideband Antenna Based...Research Laboratory Methodology for Designing and Developing a New Ultra-Wideband Antenna Based on Bio-Inspired Optimization Techniques by...SUBTITLE Methodology for Designing and Developing a New Ultra-Wideband Antenna Based on Bio-Inspired Optimization Techniques 5a. CONTRACT NUMBER

ICRF wall conditioning at TEXTOR-94 in the presence of a 2.25 T magnetic field

NASA Astrophysics Data System (ADS)

Esser, H. G.; Lyssoivan, A.; Freisinger, M.; Koch, R.; van Oost, G.; Weschenfelder, F.; Winter, J.; Textor-Icrh-Team

1997-02-01

To investigate alternative conditioning concepts for future fusion devices with permanent magnetic fields, plasmas produced by the coupling of ICRF power to He and gas mixtures of Helium + silane, have been analyzed in the presence of a 2.25 T toroidal magnetic field at TEXTOR-94. Their qualification for wall conditioning has been investigated for different He-pressures, PHe (1 × 10 -3 < PHe ( Pa) < 1 × 10 -1) and ICRF power, PICRF (100 < PICRF ( kW) < 800). Electron densities n e averaged along different radial lines of sight across the vacuum vessel from the top to the bottom have been obtained in the range 5 × 10 10 < ne ( cm-3) < 3 × 10 12. To study quantitatively the efficiency of hydrogen desorption from the first wall at different ICRF plasma conditions in a reproducible way, the first wall was presaturated by RG-glow discharges in H 2. The amount and the evolution of the H 2 desorption from rf discharge to rf discharge was determined by ion gauge measurements combined with mass spectrometry. To demonstrate the capability of the new method for plasma assisted thin film deposition, different amounts of silane (<50%) were added to the He gas. During the ICRF pulses, the silane molecules were dissociated in the plasma and the Si atoms stick to the wall. A good balance of the amount of Si disappearing from the gas phase and that measured by post mortem surface analyses of collector probes at the wall position was found.

Mechanical Development of a Very Non-Standard Patch Array Antenna for Extreme Environments

NASA Technical Reports Server (NTRS)

Hughes, Richard; Chamberlain, Neil; Jakoboski, Julie; Petkov, Mihail

2012-01-01

This paper describes the mechanical development of patch antenna arrays for the Juno mission. The patch arrays are part of a six-frequency microwave radiometer instrument that will be used to measure thermal emissions from Jupiter. The very harsh environmental conditions in Jupiter orbit, as well as a demanding launch environment, resulted in a design that departs radically from conventional printed circuit patch antennas. The paper discusses the development and qualification of the Juno patch array antennas, with emphasis on the materials approach that was devised to mitigate the effects of electron charging in Jupiter orbit.

Characterization of the mutual influence of Ion Cyclotron and Lower Hybrid Range of frequencies systems on EAST

NASA Astrophysics Data System (ADS)

Urbanczyk, Guillaume; Zhang, Xinjun; Qin, Chengming; Zhao, Yanping; Zhang, Tao; Zhang, Ling; Li, Jiangang; Yuan, Shuai; Chen, Liang; Zhang, Heng; Zhang, Jiahui; Wang, Jianhua; Yang, Xiuda; Qian, Jinping

2017-10-01

Waves in the Ion Cyclotron (ICRF) and Lower Hybrid (LH) Range of Frequencies are efficient techniques respectively to heat the plasma and drive current. Main difficulties come from a trade-off between good RF coupling and acceptable level of impurities release. The mutual influence of both systems makes such equilibrium often hard to reach [1]. In order to investigate those interactions based on Scrape-Off Layer (SOL) plasma parameters, a new reciprocating probe was designed allying a three tips Langmuir probe with an emissive wire. The emissive filament provides a precise measure of plasma potential [2], which can be used to calibrate Langmuir probe's results. This paper reports on experimental results obtained on EAST, where there are two ICRF antennas and two LH launchers. Among others diagnostics, the new reciprocating probe enabled to evidence the deleterious influence of ICRF power on LHWs coupling in L-mode plasmas. In areas connected with an active ICRF antenna, SOL potentials increase while densities tend to decrease, respectively enhancing impurities release and deteriorating LHWs coupling. This phenomenon has mostly been attributed to RF sheath; the one that forms on top of Plasma Facing Components (PFCs) and causes ExB density convections [3]. From those experiments it seems ICRF has a strong influence on magnetically connected areas, both in the near field - influencing ICRF waves coupling - and in farther locations such as in front of LH grills. Moreover, influence of ICRF on LH system was observed both in L and H modes. Those results are consistent with RF sheath rectification process. Concerning the influence of LHWs on ICRF coupling, nothing was observed in L-mode. Besides during H-mode experiments, LHWs have been identified as having a mitigating effect on ELMs [4], which on average lowers the pedestal, increasing edge densities to the profit of ICRF waves coupling.

Development And Test of A Digitally Steered Antenna Array for The Navigator GPS Receiver

NASA Technical Reports Server (NTRS)

Pinto, Heitor David; Valdez, Jennifer E.; Winternitz, Luke M. B.; Hassouneh, Munther A.; Price, Samuel R.

2012-01-01

Global Positioning System (GPS)-based navigation has become common for low-Earth orbit spacecraft as the signal environment is similar to that on the Earth s surface. The situation changes abruptly, however, for spacecraft whose orbital altitudes exceed that of the GPS constellation. Visibility is dramatically reduced and signals that are present may be very weak and more susceptible to interference. GPS receivers effective at these altitudes require increased sensitivity, which often requires a high-gain antenna. Pointing such an antenna can pose a challenge. One efficient approach to mitigate these problems is the use of a digitally steered antenna array. Such an antenna can optimally allocate gain toward desired signal sources and away from interferers. This paper presents preliminary results in the development and test of a digitally steered antenna array for the Navigator GPS research program at NASA s Goddard Space Flight Center. In particular, this paper highlights the development of an array and front-end electronics, the development and test of a real-time software GPS receiver, and implementation of three beamforming methods for combining the signals from the array. Additionally, this paper discusses the development of a GPS signal simulator which produces digital samples of the GPS L1C/A signals as they would be received by an arbitrary antenna array configuration. The simulator models transmitter and receiver dynamics, near-far and multipath interference, and has been a critical component in both the development and test of the GPS receiver. The GPS receiver system was tested with real and simulated GPS signals. Preliminary results show that performance improvement was achieved in both the weak signal and interference environments, matching analytical predictions. This paper summarizes our initial findings and discusses the advantages and limitations of the antenna array and the various beamforming methods.

The Development of Large Inflatable Antenna for Deep-Space Communications

NASA Technical Reports Server (NTRS)

Huang, John; Fang, Houfei; Lovick, Richard; Lou, Michael

2004-01-01

NASA/JPL's deep-space exploration program has been placing emphasis on reducing the mass and stowage volume of its spacecraft's high-gain and large-aperture antennas. To achieve these goals, the concept of deployable flat reflectarray antenna using an inflatable/thin-membrane structure was introduced at JPL several years ago. A reflectarray is a flat array antenna space-fed by a low-gain feed located at its focal point in a fashion similar to that of a parabolic reflector. The ref1ectarray's elements, using microstrip technology, can be printed onto a flat thin-membrane surface and are each uniquely designed to compensate for the different phase delays due to different path lengths from the feed. Although the reflectarray suffers from limited bandwidth (typically < 10%), it offers a more reliably deployed and maintained flat "natural" surface. A recent hardware development at JPL has demonstrated that a 0.2mm rms surface tolerance (l/50th of a wavelength) was achieved on a 3-meter Ka-band inflatable reflectarray. Another recent development, to combat the reflectarray's narrow band characteristic, demonstrated that dual-band performance, such as X- and Ka-bands, with an aperture efficiency of above 50 percent is achievable by the reflectarray antenna. To mechanically deploy the antenna, the reflectarray's thin membrane aperture surface is supported, tensioned and deployed by an inflatable tubular structure. There are several critical elements and challenging issues associated with the inflatable tube structure. First, the inflatable tube must be made rigidizable so that, once the tube is fully deployed in space, it rigidizes itself and the inflation system is no longer needed. In addition, if the tube is penetrated by small space debris, the tube will maintain its rigidity and not cause deformation to the antenna structure. To support large apertures (e.g. 10m or beyond) without causing any buckling to the small-diameter inflatable tube during vibration, the tube

Mode conversion in three ion species ICRF heating scenario

NASA Astrophysics Data System (ADS)

Lin, Y.; Edlund, E.; Ennever, P.; Porkolab, M.; Wright, J.; Wukitch, S.

2016-10-01

Three-ion species ICRF heating has been studied on Alcator C-Mod and on JET. It has been shown to heat the plasma and generate energetic particles. In a typical three-ion scenario, the plasma consists of 60-70% D, 30-40% H and a trace level (1% or less) of 3He. This species mixture creates two hybrid resonances (D-3He and 3He-H) in the plasma, in the vicinity of the 3He IC resonance (on both sides). The fast wave can undergo mode conversion (MC) to ion Bernstein waves and ion cyclotron waves at the two hybrid resonances. A phase contrast imaging (PCI) system has been used to measure the RF waves in the three-ion heating experiment. The experimentally measured MC locations and the separating distance between the two MC regions help to determine the concentration of the three species. The PCI signal amplitudes for the RF waves are found to be sensitive to RF and plasma parameters, including PRF, Te, ne and also the species mix concentration. The parameter dependences found in the experiment will be compared with ICRF code simulations. Supported by USDoE Awards DE-FC02-99ER54512 and DE-FG02-94-ER54235.

Inflatable Antenna for CubeSat: Extension of the Previously Developed S-Band Design to the X-Band

NASA Technical Reports Server (NTRS)

Babuscia, Alessandra; Choi, Thomas; Cheung, Kar-Ming; Thangavelautham, Jekan; Ravichandran, Mithun; Chandra, Aman

2015-01-01

The inflatable antenna for CubeSat is a 1 meter antenna reflector designed with one side reflective Mylar, another side clear Mylar with a patch antenna at the focus. The development of this technology responds to the increasing need for more capable communication systems to allow CubeSats to operate autonomously in interplanetary missions. An initial version of the antenna for the S-Band was developed and tested in both anechoic chamber and vacuum chamber. Recent developments in transceivers and amplifiers for CubeSat at X-band motivated the extension from the S-Band to the X-Band. This paper describes the process of extending the design of the antenna to the X-Band focusing on patch antenna redesign, new manufacturing challenges and initial results of experimental tests.

Design and development of a unit element microstrip antenna for aircraft collision avoidance system

NASA Astrophysics Data System (ADS)

De, Debajit; Sahu, Prasanna Kumar

2017-10-01

Aircraft/traffic alert and collision avoidance system (ACAS/TCAS) is an airborne system which is designed to provide the service as a last defense equipment for avoiding mid-air collisions between the aircraft. In the existing system, four monopole stub-elements are used as ACAS directional antenna and one blade type element is used as ACAS omnidirectional antenna. The existing ACAS antenna has some drawbacks such as low gain, large beamwidth, frequency and beam tuning/scanning issues etc. Antenna issues like unwanted signals reception may create difficulties to identify the possible threats. In this paper, the focus is on the design and development of a unit element microstrip antenna which can be used for ACAS application and to overcome the possible limitations associated with the existing techniques. Two proposed antenna models are presented here, which are single feed and dual feed microstrip dual patch slotted antenna. These are designed and simulated in CST Microwave Studio tool. The performance and other antenna characteristics have been explored from the simulation results followed by the antenna fabrication and measurement. A good reflection coefficient, Voltage Standing Wave Ratio (VSWR), narrow beamwidth, perfect directional radiation pattern, high gain and directivity make this proposed antenna a good candidate for this application.

High temperature antenna development for space shuttle, volume 1

NASA Technical Reports Server (NTRS)

Kuhlman, E. A.

1973-01-01

Design concepts for high temperature flush mounted Space Shuttle Orbiter antenna systems are discussed. The design concepts include antenna systems for VHF, L-band, S-band, C-band and Ku-band frequencies. The S-band antenna system design was completed and test hardware fabricated. It was then subjected to electrical and thermal testing to establish design requirements and determine reuse capabilities. The thermal tests consisted of applying ten high temperature cycles simulating the Orbiter entry heating environment in an arc tunnel plasma facility and observing the temperature distributions. Radiation pattern and impedance measurements before and after high temperature exposure were used to evaluated the antenna systems performance. Alternate window design concepts are considered. Layout drawings, supported by thermal and strength analyses, are given for each of the antenna system designs. The results of the electrical and thermal testing of the S-band antenna system are given.

Antennas for mobile satellite communications

NASA Technical Reports Server (NTRS)

Huang, John

1991-01-01

A NASA sponsored program, called the Mobile Satellite (MSAT) system, has prompted the development of several innovative antennas at L-band frequencies. In the space segment of the MSAT system, an efficient, light weight, circularly polarized microstrip array that uses linearly polarized elements was developed as a multiple beam reflector feed system. In the ground segment, a low-cost, low-profile, and very efficient microstrip Yagi array was developed as a medium-gain mechanically steered vehicle antenna. Circularly shaped microstrip patches excited at higher-order modes were also developed as low-gain vehicle antennas. A more recent effort called for the development of a 20/30 GHz mobile terminal antenna for future-generation mobile satellite communications. To combat the high insertion loss encountered at 20/30 GHz, series-fed Monolithic Microwave Integrated Circuit (MMIC) microstrip array antennas are currently being developed. These MMIC arrays may lead to the development of several small but high-gain Ka-band antennas for the Personal Access Satellite Service planned for the 2000s.

Conformal, Transparent Printed Antenna Developed for Communication and Navigation Systems

NASA Technical Reports Server (NTRS)

Lee, Richard Q.; Simons, Rainee N.

1999-01-01

Conformal, transparent printed antennas have advantages over conventional antennas in terms of space reuse and aesthetics. Because of their compactness and thin profile, these antennas can be mounted on video displays for efficient integration in communication systems such as palmtop computers, digital telephones, and flat-panel television displays. As an array of multiple elements, the antenna subsystem may save weight by reusing space (via vertical stacking) on photovoltaic arrays or on Earth-facing sensors. Also, the antenna could go unnoticed on automobile windshields or building windows, enabling satellite uplinks and downlinks or other emerging high-frequency communications.

Radio antennas

NASA Astrophysics Data System (ADS)

Gibson, S. W.

This book is concerned with providing an explanation of the function of an antenna without delving too deeply into the mathematics or theory. The characteristics of an antenna are examined, taking into account aspects of antenna radiation, wave motion on the antenna, resistance in the antenna, impedance, the resonant antenna, the effect of the ground, polarization, radiation patterns, coupling effects between antenna elements, and receiving vs. transmitting. Aspects of propagation are considered along with the types of antennas, transmission lines, matching devices, questions of antenna design, antennas for the lower frequency bands, antennas for more than one band, limited space antennas, VHF antennas, and antennas for 20, 15, and 10 meters. Attention is given to devices for measuring antenna parameters, approaches for evaluating the antenna, questions of safety, and legal aspects.

The Role of Combined ICRF and NBI Heating in JET Hybrid Plasmas in Quest for High D-T Fusion Yield

NASA Astrophysics Data System (ADS)

Mantsinen, Mervi; Challis, Clive; Frigione, Domenico; Graves, Jonathan; Hobirk, Joerg; Belonohy, Eva; Czarnecka, Agata; Eriksson, Jacob; Gallart, Dani; Goniche, Marc; Hellesen, Carl; Jacquet, Philippe; Joffrin, Emmanuel; King, Damian; Krawczyk, Natalia; Lennholm, Morten; Lerche, Ernesto; Pawelec, Ewa; Sips, George; Solano, Emilia R.; Tsalas, Maximos; Valisa, Marco

2017-10-01

Combined ICRF and NBI heating played a key role in achieving the world-record fusion yield in the first deuterium-tritium campaign at the JET tokamak in 1997. The current plans for JET include new experiments with deuterium-tritium (D-T) plasmas with more ITER-like conditions given the recently installed ITER-like wall (ILW). In the 2015-2016 campaigns, significant efforts have been devoted to the development of high-performance plasma scenarios compatible with ILW in preparation of the forthcoming D-T campaign. Good progress was made in both the inductive (baseline) and the hybrid scenario: a new record JET ILW fusion yield with a significantly extended duration of the high-performance phase was achieved. This paper reports on the progress with the hybrid scenario which is a candidate for ITER longpulse operation (˜1000 s) thanks to its improved normalized confinement, reduced plasma current and higher plasma beta with respect to the ITER reference baseline scenario. The combined NBI+ICRF power in the hybrid scenario was increased to 33 MW and the record fusion yield, averaged over 100 ms, to 2.9x1016 neutrons/s from the 2014 ILW fusion record of 2.3x1016 neutrons/s. Impurity control with ICRF waves was one of the key means for extending the duration of the high-performance phase. The main results are reviewed covering both key core and edge plasma issues.

High field side launch of RF waves: A new approach to reactor actuators

NASA Astrophysics Data System (ADS)

Wallace, G. M.; Baek, S. G.; Bonoli, P. T.; Faust, I. C.; LaBombard, B. L.; Lin, Y.; Mumgaard, R. T.; Parker, R. R.; Shiraiwa, S.; Vieira, R.; Whyte, D. G.; Wukitch, S. J.

2015-12-01

Launching radio frequency (RF) waves from the high field side (HFS) of a tokamak offers significant advantages over low field side (LFS) launch with respect to both wave physics and plasma material interactions (PMI). For lower hybrid (LH) waves, the higher magnetic field opens the window between wave accessibility (n∥≡c k∥/ω >√{1 -ωpi 2/ω2+ωpe 2/ωce 2 }+ωp e/|ωc e| ) and the condition for strong electron Landau damping (n∥˜√{30 /Te } with Te in keV), allowing LH waves from the HFS to penetrate into the core of a burning plasma, while waves launched from the LFS are restricted to the periphery of the plasma. The lower n∥ of waves absorbed at higher Te yields a higher current drive efficiency as well. In the ion cyclotron range of frequencies (ICRF), HFS launch allows for direct access to the mode conversion layer where mode converted waves absorb strongly on thermal electrons and ions, thus avoiding the generation of energetic minority ion tails. The absence of turbulent heat and particle fluxes on the HFS, particularly in double null configuration, makes it the ideal location to minimize PMI damage to the antenna structure. The quiescent SOL also eliminates the need to couple LH waves across a long distance to the separatrix, as the antenna can be located close to plasma without risking damage to the structure. Improved impurity screening on the HFS will help eliminate the long-standing issues of high Z impurity accumulation with ICRF. Looking toward a fusion reactor, the HFS is the only possible location for a plasma-facing RF antenna that will survive long-term. By integrating the antenna into the blanket module it is possible to improve the tritium breeding ratio compared with an antenna occupying an equatorial port plug. Blanket modules will require remote handling of numerous cooling pipes and electrical connections, and the addition of transmission lines will not substantially increase the level of complexity. The obvious engineering

Multibeam antenna study, phase 1

NASA Technical Reports Server (NTRS)

Bellamy, J. L.

1972-01-01

A multibeam antenna concept was developed for providing spot beam coverage of the contiguous 48 states. The selection of a suitable antenna concept for the multibeam application and an experimental evaluation of the antenna concept selected are described. The final analysis indicates that the preferred concept is a dual-antenna, circular artificial dielectric lens. A description of the analytical methods is provided, as well as a discussion of the absolute requirements placed on the antenna concepts. Finally, a comparative analysis of reflector antenna off-axis beam performance is presented.

Comsat Antenna

NASA Technical Reports Server (NTRS)

1978-01-01

The antenna shown is the new, multiple-beam, Unattended Earth Terminal, located at COMSAT Laboratories in Clarksburg, Maryland. Seemingly simple, it is actually a complex structure capable of maintaining contact with several satellites simultaneously (conventional Earth station antennas communicate with only one satellite at a time). In developing the antenna, COMSAT Laboratories used NASTRAN, NASA's structural analysis computer program, together with BANDIT, a companion program. The computer programs were used to model several structural configurations and determine the most suitable, The speed and accuracy of the computerized design analysis afforded appreciable savings in time and money.

Antenna Technologies for NASA Applications

NASA Technical Reports Server (NTRS)

Miranda, Felix

2007-01-01

This presentation addresses the efforts being performed at GRC to develop antenna technology in support of NASA s Exploration Vision. In particular, the presentation discusses the communications architecture asset-specific data services, as well as wide area coverage, high gain, low mass deployable antennas. Phased array antennas as well as electrically small, lightweight, low power, multifunctional antennas will be also discussed.

Antenna Technologies for NASA Applications

NASA Technical Reports Server (NTRS)

Miranda, Felix A.

2006-01-01

This presentation addresses the efforts being performed at GRC to develop antenna technology in support of NASA s Exploration Vision. In particular, the presentation discusses the communications architecture asset-specific data services, as well as wide area coverage, high gain, low mass deployable antennas. Phased array antennas as well as electrically small, lightweight, low power, multifunctional antennas will be also discussed.

Autonomous omnidirectional spacecraft antenna system

NASA Technical Reports Server (NTRS)

Taylor, T. H.

1983-01-01

The development of a low gain Electronically Switchable Spherical Array Antenna is discussed. This antenna provides roughly 7 dBic gain for receive/transmit operation between user satellites and the Tracking and Data Relay Satellite System. When used as a pair, the antenna provides spherical coverage. The antenna was tested in its primary operating modes: directed beam, retrodirective, and Omnidirectional.

Milestones in Broadcasting: Antennas.

ERIC Educational Resources Information Center

Media in Education and Development, 1985

1985-01-01

Briefly describes the development of antennas in the prebroadcast era (elevated antenna, selectivity to prevent interference between stations, birth of diplex, directional properties, support structures), as well as technological developments used in long-, medium-, and short-wave broadcasting, VHF/FM and television broadcasting, and satellite…

SIDON: A simulator of radio-frequency networks. Application to WEST ICRF launchers

NASA Astrophysics Data System (ADS)

Helou, Walid; Dumortier, Pierre; Durodié, Frédéric; Goniche, Marc; Hillairet, Julien; Mollard, Patrick; Berger-By, Gilles; Bernard, Jean-Michel; Colas, Laurent; Lombard, Gilles; Maggiora, Riccardo; Magne, Roland; Milanesio, Daniele; Moreau, Didier

2015-12-01

SIDON (SImulator of raDiO-frequency Networks) is an in-house developed Radio-Frequency (RF) network solver that has been implemented to cross-validate the design of WEST ICRF launchers and simulate their impedance matching algorithm while considering all mutual couplings and asymmetries. In this paper, the authors illustrate the theory of SIDON as well as results of its calculations. The authors have built time-varying plasma scenarios (a sequence of launchers front-faces L-mode and H-mode Z-matrices), where at each time step (1 millisecond here), SIDON solves the RF network. At the same time, when activated, the impedance matching algorithm controls the matching elements (vacuum capacitors) and thus their corresponding S-matrices. Typically a 1-second pulse requires around 10 seconds of computational time on a desktop computer. These tasks can be hardly handled by commercial RF software. This innovative work allows identifying strategies for the launchers future operation while insuring the limitations on the currents, voltages and electric fields, matching and Load-Resilience, as well as the required straps voltage amplitude/phase balance. In this paper, a particular attention is paid to the simulation of the launchers behavior when arcs appear at several locations of their circuits using SIDON calculator. This latter work shall confirm or identify strategies for the arc detection using various RF electrical signals. One shall note that the use of such solvers in not limited to ICRF launchers simulations but can be employed, in principle, to any linear or linearized RF problem.

Optical antenna gain. I - Transmitting antennas

NASA Technical Reports Server (NTRS)

Klein, B. J.; Degnan, J. J.

1974-01-01

The gain of centrally obscured optical transmitting antennas is analyzed in detail. The calculations, resulting in near- and far-field antenna gain patterns, assume a circular antenna illuminated by a laser operating in the TEM-00 mode. A simple polynomial equation is derived for matching the incident source distribution to a general antenna configuration for maximum on-axis gain. An interpretation of the resultant gain curves allows a number of auxiliary design curves to be drawn that display the losses in antenna gain due to pointing errors and the cone angle of the beam in the far field as a function of antenna aperture size and its central obscuration. The results are presented in a series of graphs that allow the rapid and accurate evaluation of the antenna gain which may then be substituted into the conventional range equation.

Notch Antennas

NASA Technical Reports Server (NTRS)

Lee, Richard Q.

2004-01-01

Notch antennas, also known as the tapered slot antenna (TSA), have been the topics of research for decades. TSA has demonstrated multi-octave bandwidth, moderate gain (7 to 10 dB), and symmetric E- and H- plane beam patterns and can be used for many different applications. This chapter summarizes the research activities on notch antennas over the past decade with emphasis on their most recent advances and applications. This chapter begins with some discussions on the designs of single TSA; then follows with detailed discussions of issues associated with TSA designs and performance characteristics. To conclude the chapter, some recent developments in TSA arrays and their applications are highlighted.

X-Antenna: A graphical interface for antenna analysis codes

NASA Technical Reports Server (NTRS)

Goldstein, B. L.; Newman, E. H.; Shamansky, H. T.

1995-01-01

This report serves as the user's manual for the X-Antenna code. X-Antenna is intended to simplify the analysis of antennas by giving the user graphical interfaces in which to enter all relevant antenna and analysis code data. Essentially, X-Antenna creates a Motif interface to the user's antenna analysis codes. A command-file allows new antennas and codes to be added to the application. The menu system and graphical interface screens are created dynamically to conform to the data in the command-file. Antenna data can be saved and retrieved from disk. X-Antenna checks all antenna and code values to ensure they are of the correct type, writes an output file, and runs the appropriate antenna analysis code. Volumetric pattern data may be viewed in 3D space with an external viewer run directly from the application. Currently, X-Antenna includes analysis codes for thin wire antennas (dipoles, loops, and helices), rectangular microstrip antennas, and thin slot antennas.

High temperature antenna development for space shuttle, volume 2. [space environment simulation effects on antenna radiation patterns

NASA Technical Reports Server (NTRS)

Kuhlman, E. A.

1974-01-01

An S-band antenna system and a group of off-the-shelf aircraft antenna were exposed to temperatures simulating shuttle orbital cold soak and entry heating. Radiation pattern and impedance measurements before and after exposure to the thermal environments were used to evaluate the electrical performance. The results of the electrical and thermal testing are given. Test data showed minor changes in electrical performance and established the capability of these antenna to withstand both the low temperatures of space flight and the high temperatures of entry.

Initial '80s Development of Inflated Antennas

NASA Technical Reports Server (NTRS)

Friese, G. J.; Bilyeu, G. D.; Thomas, M.

1983-01-01

State of the art technology was considered in the definition and documentation of a membrane surface suitable for use in a space reflector system for long durations in orbit. Requirements for a metal foil-plastic laminate structural element were determined and a laboratory model of a rigidized element to test for strength characteristics was constructed. Characteristics of antennas ranging from 10 meters to 1000 meters were determined. The basic antenna configuration studied consists of (1) a thin film reflector, (2) a thin film cone, (3) a self-rigidizing structural torus at the interface of the cone and reflector; and (4) an inflation system. The reflector is metallized and, when inflated, has a parabolic shape. The cone not only completes the enclosure of the inflatant, but also holds the antenna feed at its apex. The torus keeps the inflated cone-reflector from collapsing inward. Laser test equipment determined the accuracy of the inflated paraboloids.

Development and validation of a low-frequency modeling code for high-moment transmitter rod antennas

NASA Astrophysics Data System (ADS)

Jordan, Jared Williams; Sternberg, Ben K.; Dvorak, Steven L.

2009-12-01

The goal of this research is to develop and validate a low-frequency modeling code for high-moment transmitter rod antennas to aid in the design of future low-frequency TX antennas with high magnetic moments. To accomplish this goal, a quasi-static modeling algorithm was developed to simulate finite-length, permeable-core, rod antennas. This quasi-static analysis is applicable for low frequencies where eddy currents are negligible, and it can handle solid or hollow cores with winding insulation thickness between the antenna's windings and its core. The theory was programmed in Matlab, and the modeling code has the ability to predict the TX antenna's gain, maximum magnetic moment, saturation current, series inductance, and core series loss resistance, provided the user enters the corresponding complex permeability for the desired core magnetic flux density. In order to utilize the linear modeling code to model the effects of nonlinear core materials, it is necessary to use the correct complex permeability for a specific core magnetic flux density. In order to test the modeling code, we demonstrated that it can accurately predict changes in the electrical parameters associated with variations in the rod length and the core thickness for antennas made out of low carbon steel wire. These tests demonstrate that the modeling code was successful in predicting the changes in the rod antenna characteristics under high-current nonlinear conditions due to changes in the physical dimensions of the rod provided that the flux density in the core was held constant in order to keep the complex permeability from changing.

Satellite Antenna Systems

NASA Technical Reports Server (NTRS)

1997-01-01

Through the Technology Affiliates Program at the Jet Propulsion Laboratory, the ACTS antenna system was transferred from experimental testing status to commercial development with KVH Industries, Inc. The ACTS design enables mobile satellite antennas to remain pointed at the satellite, regardless of the motion or vibration on which it is mounted. KVH's first product based on the ACTS design is a land-mobile satellite antenna system that will enable direct broadcast satellite television aboard moving trucks, recreational vehicles, trains, and buses. Future products could include use in broadcasting, emergency medical and military vehicles.

ICRF fast wave current drive and mode conversion current drive in EAST tokamak

NASA Astrophysics Data System (ADS)

Yin, L.; Yang, C.; Gong, X. Y.; Lu, X. Q.; Du, D.; Chen, Y.

2017-10-01

Fast wave in the ion-cyclotron resonance frequency (ICRF) range is a promising candidate for non-inductive current drive (CD), which is essential for long pulse and high performance operation of tokamaks. A numerical study on the ICRF fast wave current drive (FWCD) and mode-conversion current drive (MCCD) in the Experimental Advanced Superconducting Tokamak (EAST) is carried out by means of the coupled full wave and Ehst-Karney parameterization methods. The results show that FWCD efficiency is notable in two frequency regimes, i.e., f ≥ 85 MHz and f = 50-65 MHz, where ion cyclotron absorption is effectively avoided, and the maximum on-axis driven current per unit power can reach 120 kA/MW. The sensitivity of the CD efficiency to the minority ion concentration is confirmed, owing to fast wave mode conversion, and the peak MCCD efficiency is reached for 22% minority-ion concentration. The effects of the wave-launch position and the toroidal wavenumber on the efficiency of current drive are also investigated.

Development of plasma sources for ICRF heating experiment in KMAX mirror device

NASA Astrophysics Data System (ADS)

Sun, Xuan; Liu, Ming; Yi, Hongshen; Lin, Munan; Shi, Peiyun

2016-10-01

KMAX, Keda Mirror with AXisymmeticity, is a tandem mirror machine with a length of 10 meters and diameters of 1.2 meters in the central cell and 0.3 meters in the mirror throat. In the past experiments, the plasma was generated by helicon wave launched from the west end. We obtained the blue core mode in argon discharge, however, it cannot provide sufficient plasma for hydrogen discharge, which is at least 1012 cm-3 required for effective ICRF heating. Several attempts have thus been tried or under design to increase the central cell's plasma density: (1) a washer gun with aperture of 1cm has been successfully tested, and a plasma density of 1013 cm-3 was achieved in the west cell near the gun, however, the plasma is only 1011 cm-3 in the central cell possible due to the mirror trapping and/or neutral quenching effect (2) a larger washer gun with aperture of 2.5 cm and a higher power capacitor bank are being assembled in order to generate more plasmas. In addition, how to mitigate the neutrals is under consideration (3) A hot cathode is been designed and will be tested in combination with plasma gun or alone. Preliminary results from those plasma sources will be presented and discussed.

Volumetric pattern analysis of fuselage-mounted airborne antennas. Ph.D. Thesis; [prediction analysis techniques for antenna radiation patterns of microwave antennas on commercial aircraft

NASA Technical Reports Server (NTRS)

Yu, C. L.

1976-01-01

A volumetric pattern analysis of fuselage-mounted airborne antennas at high frequencies was investigated. The primary goal of the investigation was to develop a numerical solution for predicting radiation patterns of airborne antennas in an accurate and efficient manner. An analytical study of airborne antenna pattern problems is presented in which the antenna is mounted on the fuselage near the top or bottom. Since this is a study of general-type commercial aircraft, the aircraft was modeled in its most basic form. The fuselage was assumed to be an infinitely long perfectly conducting elliptic cylinder in its cross-section and a composite elliptic cylinder in its elevation profile. The wing, cockpit, stabilizers (horizontal and vertical) and landing gear are modeled by "N" sided bent or flat plates which can be arbitrarily attached to the fuselage. The volumetric solution developed utilizes two elliptic cylinders, namely, the roll plane and elevation plane models to approximate the principal surface profile (longitudinal and transverse) at the antenna location. With the belt concept and the aid of appropriate coordinate system transformations the solution can be used to predict the volumetric patterns of airborne antennas in an accurate and efficient manner. Applications of this solution to various airborne antenna problems show good agreement with scale model measurements. Extensive data are presented for a microwave landing antenna system.

Telecommunications Antennas for the Juno Mission to Jupiter

NASA Technical Reports Server (NTRS)

Vacchione, Joseph D.; Kruid, Ronald C.; Prata, Aluizio, Jr.; Amaro, Luis R.; Mittskus, Anthony P.

2012-01-01

The Juno Mission to Jupiter requires a full sphere of coverage throughout its cruise to and mission at Jupiter. This coverage is accommodated through the use of five (5) antennas; forward facing low gain, medium gain, and high gain antennas, and an aft facing low gain antenna along with an aft mounted low gain antenna with a torus shaped antenna pattern. Three of the antennas (the forward low and medium gain antennas) are classical designs that have been employed on several prior NASA missions. Two of the antennas employ new technology developed to meet the Juno mission requirements. The new technology developed for the low gain with torus shaped radiation pattern represents a significant evolution of the bicone antenna. The high gain antenna employs a specialized surface shaping designed to broaden the antenna's main beam at Ka-band to ease the requirements on the spacecraft's attitude control system.

Study of ICRF wave propagation and plasma coupling efficiency in a linear magnetic mirror device

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

Peng, S.Y.

1991-07-01

Ion Cyclotron Range of Frequency (ICRF) wave propagation in an inhomogeneous axial magnetic field in a cylindrical plasma-vacuum system has historically been inadequately modelled. Previous works either sacrifice the cylindrical geometry in favor of a simpler slab geometry, concentrate on the resonance region, use a single mode to represent the entire field structure, or examine only radial propagation. This thesis performs both analytical and computational studies to model the ICRF wave-plasma coupling and propagation problem. Experimental analysis is also conducted to compare experimental results with theoretical predictions. Both theoretical as well as experimental analysis are undertaken as part of themore » thesis. The theoretical studies simulate the propagation of ICRF waves in an axially inhomogeneous magnetic field and in cylindrical geometry. Two theoretical analysis are undertaken - an analytical study and a computational study. The analytical study treats the inhomogeneous magnetic field by transforming the (r,z) coordinate into another coordinate system ({rho},{xi}) that allows the solution of the fields with much simpler boundaries. The plasma fields are then Fourier transformed into two coupled convolution-integral equations which are then differenced and solved for both the perpendicular mode number {alpha} as well as the complete EM fields. The computational study involves a multiple eigenmode computational analysis of the fields that exist within the plasma-vacuum system. The inhomogeneous axial field is treated by dividing the geometry into a series of transverse axial slices and using a constant dielectric tensor in each individual slice. The slices are then connected by longitudinal boundary conditions.« less

Design and test of voltage and current probes for EAST ICRF antenna impedance measurement

NASA Astrophysics Data System (ADS)

Jianhua, WANG; Gen, CHEN; Yanping, ZHAO; Yuzhou, MAO; Shuai, YUAN; Xinjun, ZHANG; Hua, YANG; Chengming, QIN; Yan, CHENG; Yuqing, YANG; Guillaume, URBANCZYK; Lunan, LIU; Jian, CHENG

2018-04-01

On the experimental advanced superconducting tokamak (EAST), a pair of voltage and current probes (V/I probes) is installed on the ion cyclotron radio frequency transmission lines to measure the antenna input impedance, and supplement the conventional measurement technique based on voltage probe arrays. The coupling coefficients of V/I probes are sensitive to their sizes and installing locations, thus they should be determined properly to match the measurement range of data acquisition card. The V/I probes are tested in a testing platform at low power with various artificial loads. The testing results show that the deviation of coupling resistance is small for loads R L > 2.5 Ω, while the resistance deviations appear large for loads R L < 1.5 Ω, which implies that the power loss cannot be neglected at high VSWR. As the factors that give rise to the deviation of coupling resistance calculation, the phase measurement error is the more significant factor leads to deleterious results rather than the amplitude measurement error. To exclude the possible ingredients that may lead to phase measurement error, the phase detector can be calibrated in steady L-mode scenario and then use the calibrated data for calculation under H-mode cases in EAST experiments.

Development of distortion measurement system for large deployable antenna via photogrammetry in vacuum and cryogenic environment

NASA Astrophysics Data System (ADS)

Zhang, Pengsong; Jiang, Shanping; Yang, Linhua; Zhang, Bolun

2018-01-01

In order to meet the requirement of high precision thermal distortion measurement foraΦ4.2m deployable mesh antenna of satellite in vacuum and cryogenic environment, based on Digital Close-range Photogrammetry and Space Environment Test Technology of Spacecraft, a large scale antenna distortion measurement system under vacuum and cryogenic environment is developed in this paper. The antenna Distortion measurement system (ADMS) is the first domestic independently developed thermal distortion measurement system for large antenna, which has successfully solved non-contact high precision distortion measurement problem in large spacecraft structure under vacuum and cryogenic environment. The measurement accuracy of ADMS is better than 50 μm/5m, which has reached international advanced level. The experimental results show that the measurement system has great advantages in large structural measurement of spacecrafts, and also has broad application prospects in space or other related fields.

Development of Leaky Wave Antennas for Layered Ridge Dielectric Waveguide

NASA Technical Reports Server (NTRS)

Ponchak, George E.; Katehi, Linda P. B.

1993-01-01

The millimeter wave, especially above 100 GHz, and the submillimeter wave frequency spectrum offers the possibility for narrow-beam, high-resolution antennas which are critical for high definition radars required for space debris tracking, airport ground avoidance radars, and missile tracking. In addition, the frequency which most atmospheric constituents may be detected lie in this part of the frequency spectrum. Therefore, the development of electronic components for millimeter/submillimeter wave passive sensors is required for environmental monitoring of the Earth's atmosphere. Typical microwave transmission lines such as microstrip and coplanar waveguide rely on two or more electrical conductors to concentrate and guide the electromagnetic energy. Unfortunately, the surface resistance of the conductors increases as the square root of frequency. In addition, the circuit dimensions must be decreased with increasing frequency to maintain a single mode transmission line which further increases the conductor loss. An alternative family of transmission lines are formed from two or more insulating materials and rely on the differences in the permittivities between the two materials to guide the wave. No metal conductors are required although some dielectric waveguides do utilize a metallic ground plane to facilitate the interconnections of active electrical elements or to reduce the transmission line size. Examples of such transmission lines are image guides, insulated image guides, trapped image guides, ridge guide, and layered ridge dielectric waveguide (LRDW). Although most dielectric waveguides have dimensions on the order of lambda to provide sufficient field confinement, the LRDW has been shown to provide good field confinement for electrically small lines. This offers an advantage in circuit integration. It has been shown that a periodic array of metallic strips placed either along or on top of a dielectric waveguide forms an effective radiator. This antenna is

An Approach for Smart Antenna Testbed

NASA Astrophysics Data System (ADS)

Kawitkar, R. S.; Wakde, D. G.

2003-07-01

The use of wireless, mobile, personal communications services are expanding rapidly. Adaptive or "Smart" antenna arrays can increase channel capacity through spatial division. Adaptive antennas can also track mobile users, improving both signal range and quality. For these reasons, smart antenna systems have attracted widespread interest in the telecommunications industry for applications to third generation wireless systems.This paper aims to design and develop an advanced antennas testbed to serve as a common reference for testing adaptive antenna arrays and signal combining algorithms, as well as complete systems. A flexible suite of off line processing software should be written using matlab to perform system calibration, test bed initialization, data acquisition control, data storage/transfer, off line signal processing and analysis and graph plotting. The goal of this paper is to develop low complexity smart antenna structures for 3G systems. The emphasis will be laid on ease of implementation in a multichannel / multi-user environment. A smart antenna test bed will be developed, and various state-of-the-art DSP structures and algorithms will be investigated.Facing the soaring demand for mobile communications, the use of smart antenna arrays in mobile communications systems to exploit spatial diversity to further improve spectral efficiency has recently received considerable attention. Basically, a smart antenna array comprises a number of antenna elements combined via a beamforming network (amplitude and phase control network). Some of the benefits that can be achieved by using SAS (Smart Antenna System) include lower mobile terminal power consumption, range extension, ISI reduction, higher data rate support, and ease of integration into the existing base station system. In terms of economic benefits, adaptive antenna systems employed at base station, though increases the per base station cost, can increase coverage area of each cell site, thereby reducing

Development of Quantum Cascade Lasers with Novel Active Regions and Integrated Nano-Antennas

NASA Astrophysics Data System (ADS)

Dey, Dibyendu

Quantum Cascade Laser (QCL), invented in 1994, has led to path-breaking improvements in room-temperature operation in mid and long wave infrared, and has been used in gas and chemical sensing, bio-imaging, free-space communications and many other military applications. One of the major operational drawbacks of standard QCL is added phonon relaxation in the injector region leading to generation of excess heat. The first part of my thesis focuses on developing a novel injectorless QCL (I-QCL) which circumvents this problem. The fabricated laser was both electrically and optically tested and compared with two types of standard QCLs---one developed in our laboratory and another provided by MIT Lincoln Laboratory. Voltage defect is a key parameter used to quantify excess heat generated in a QCL. We were able to measure a record low voltage defect of ˜ 57 meV at 77 K using the I-QCL we have developed. The effect of injectors on thermal performance of QCL was further analyzed through time-resolved spectral analysis. Next, we focused on developing a composite material based plasmonic antenna integrated QCL. The device was capable of squeezing the optical mode to ˜ 100 nm which is 60 times smaller than the operating wavelength (˜ 6 um). Such mode confinement can overcome the primary drawback in a mid-IR bio-sensor where the dimensional mismatch between long wavelengths (order of microns) and tiny probed molecules (˜ few nanometers) makes probe-particle interaction strength extremely weak. An apertureless near-field scanning optical microscope (a-NSOM) was built to measure the antenna near-field characteristic. We further worked on measuring the optical force generated near the antenna "hotspot" due to high electric field gradient. We then worked on understanding the coupling between antenna plasmonic modes and the laser cavity mode. This unusual coupling has been explained based on optical feedback effect. The final part of my research focused on delivering the bio

ATCRBS Improvement Program Reflector Antenna Development

DOT National Transportation Integrated Search

1976-06-01

This report describes the results of a program undertaken by Texas Instruments Incorporated, under contract to the Transportation Systems Center (TSC), to investigate improved antennas for the Air Traffic Control Radar Beacon System (ATCRBS). Under t...

Design and Development of Aerogel-Based Antennas for Aerospace Applications: A Final Report to the NARI Seedling

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B.; Miranda, Felix A.

2014-01-01

explored the possibility of developing these arrays in thin, flexible form to make conformable antennas.

System-Level Integrated Circuit (SLIC) development for phased array antenna applications

NASA Technical Reports Server (NTRS)

Shalkhauser, K. A.; Raquet, C. A.

1991-01-01

A microwave/millimeter wave system-level integrated circuit (SLIC) being developed for use in phased array antenna applications is described. The program goal is to design, fabricate, test, and deliver an advanced integrated circuit that merges radio frequency (RF) monolithic microwave integrated circuit (MMIC) technologies with digital, photonic, and analog circuitry that provide control, support, and interface functions. As a whole, the SLIC will offer improvements in RF device performance, uniformity, and stability while enabling accurate, rapid, repeatable control of the RF signal. Furthermore, the SLIC program addresses issues relating to insertion of solid state devices into antenna systems, such as the reduction in number of bias, control, and signal lines. Program goals, approach, and status are discussed.

System-level integrated circuit (SLIC) development for phased array antenna applications

NASA Technical Reports Server (NTRS)

Shalkhauser, K. A.; Raquet, C. A.

1991-01-01

A microwave/millimeter wave system-level integrated circuit (SLIC) being developed for use in phased array antenna applications is described. The program goal is to design, fabricate, test, and deliver an advanced integrated circuit that merges radio frequency (RF) monolithic microwave integrated circuit (MMIC) technologies with digital, photonic, and analog circuitry that provide control, support, and interface functions. As a whole, the SLIC will offer improvements in RF device performance, uniformity, and stability while enabling accurate, rapid, repeatable control of the RF signal. Furthermore, the SLIC program addresses issues relating to insertion of solid state devices into antenna systems, such as the reduction in number of bias, control, and signal lines. Program goals, approach, and status are discussed.

Inflatable Space Structures Technology Development for Large Radar Antennas

NASA Technical Reports Server (NTRS)

Freeland, R. E.; Helms, Richard G.; Willis, Paul B.; Mikulas, M. M.; Stuckey, Wayne; Steckel, Gary; Watson, Judith

2004-01-01

There has been recent interest in inflatable space-structures technology for possible applications on U.S. Department of Defense (DOD) missions because of the technology's potential for high mechanical-packaging efficiency, variable stowed geometry, and deployment reliability. In recent years, the DOD sponsored Large Radar Antenna (LRA) Program applied this new technology to a baseline concept: a rigidizable/inflatable (RI) perimeter-truss structure supporting a mesh/net parabolic reflector antenna. The program addressed: (a) truss concept development, (b) regidizable materials concepts assessment, (c) mesh/net concept selection and integration, and (d) developed potential mechanical-system performance estimates. Critical and enabling technologies were validated, most notably the orbital radiation durable regidized materials and the high modulus, inflatable-deployable truss members. These results in conjunction with conclusions from previous mechanical-packaging studies by the U.S. Defense Advanced Research Projects Agency (DARPA) Special Program Office (SPO) were the impetus for the initiation of the DARPA/SPO Innovative Space-based Antenna Technology (ISAT) Program. The sponsor's baseline concept consisted of an inflatable-deployable truss structure for support of a large number of rigid, active radar panels. The program's goal was to determine the risk associated with the application of these new RI structures to the latest in radar technologies. The approach used to define the technology maturity level of critical structural elements was to: (a) develop truss concept baseline configurations (s), (b) assess specific inflatable-rigidizable materials technologies, and (c) estimate potential mechanical performance. The results of the structures portion of the program indicated there was high risk without the essential materials technology flight experiments, but only moderate risk if the appropriate on-orbit demonstrations were performed. This paper covers both

Development of a Multi-Band Shared Aperture Reflectarray/Reflector Antenna Design for NASA

NASA Technical Reports Server (NTRS)

Spence, Thomas; Cooley, Michael; Stenger, Peter; Park, Richard; Li, Lihua; Racette, Paul; Heymsfield, Gerald; Mclinden, Matthew

2016-01-01

A dual-band (Ka/W) shared-aperture antenna system design has been developed as a proposed solution to meet the needs of NASA's planned Aerosol, Clouds, and Ecosystem (ACE) mission. The design is comprised of a compact Cassegrain reflector/reflect array with a fixed W-band feed and a cross track scanned Ka-band Active Electronically Scanned Array (AESA). Critical Sub-scale prototype testing and flight tests have validated some of the key aspects of this innovative antenna design, including the low loss reflector/reflect array surface. More recently the science community has expressed interest in a mission that offers the ability to measure precipitation (Ku- band with scanning) in addition to clouds and aerosols. In this paper we present findings from a design study that explores options for realizing a tri-frequency (Ku/Ka/W), shared-aperture antenna system to meet these science objectives. Design considerations included meeting performance requirements while striving to minimize payload size, weight, prime power, and cost. The extensive trades and lessons learned from the ACE system development were utilized as the foundation for this work.

E-Textile Antennas for Space Environments

NASA Technical Reports Server (NTRS)

Kennedy, Timothy F.; Fink, Patrick W.; Chu, Andrew W.

2007-01-01

The ability to integrate antennas and other radio frequency (RF) devices into wearable systems is increasingly important as wireless voice, video, and data sources become ubiquitous. Consumer applications including mobile computing, communications, and entertainment, as well as military and space applications for integration of biotelemetry, detailed tracking information and status of handheld tools, devices and on-body inventories are driving forces for research into wearable antennas and other e-textile devices. Operational conditions for military and space applications of wireless systems are often such that antennas are a limiting factor in wireless performance. The changing antenna platform, i.e. the dynamic wearer, can detune and alter the radiation characteristics of e-textile antennas, making antenna element selection and design challenging. Antenna designs and systems that offer moderate bandwidth, perform well with flexure, and are electronically reconfigurable are ideally suited to wearable applications. Several antennas, shown in Figure 1, have been created using a NASA-developed process for e-textiles that show promise in being integrated into a robust wireless system for space-based applications. Preliminary characterization of the antennas with flexure indicates that antenna performance can be maintained, and that a combination of antenna design and placement are useful in creating robust designs. Additionally, through utilization of modern smart antenna techniques, even greater flexibility can be achieved since antenna performance can be adjusted in real-time to compensate for the antenna s changing environment.

Development of 2-D horn-antenna millimeter-wave imaging device (HMID) for the plasma diagnostics

NASA Astrophysics Data System (ADS)

Nagayama, Y.; Ito, N.; Kuwahara, D.; Tsuchiya, H.; Yamaguchi, S.

2017-04-01

The two-dimensional (2-D) Horn-antenna Millimeter-wave Imaging Device (HMID) has been developed for the O-mode Microwave Imaging Reflectometry (O-MIR) in the Large Helical Device (LHD). The detectable frequency range of the HMID is 23-33 GHz, which corresponds to the cutoff electron density of 0.8-1.5 × 1019 m-3 in the O-MIR. The HMID is a 2-D imaging device that improves on the horn-antenna mixer array, which had been developed for the X-mode MIR in the LHD. In the HMID, the signal (RF) wave from the horn antenna is transmitted to the microstrip line by the finline transmitter, and this is mixed by the double-balanced-mixer with the local oscillation wave that is fed by a coaxial cable. By using the HMID, the MIR optical system can be significantly simplified.

Smart Antenna UKM Testbed for Digital Beamforming System

NASA Astrophysics Data System (ADS)

Islam, Mohammad Tariqul; Misran, Norbahiah; Yatim, Baharudin

2009-12-01

A new design of smart antenna testbed developed at UKM for digital beamforming purpose is proposed. The smart antenna UKM testbed developed based on modular design employing two novel designs of L-probe fed inverted hybrid E-H (LIEH) array antenna and software reconfigurable digital beamforming system (DBS). The antenna is developed based on using the novel LIEH microstrip patch element design arranged into [InlineEquation not available: see fulltext.] uniform linear array antenna. An interface board is designed to interface to the ADC board with the RF front-end receiver. The modular concept of the system provides the capability to test the antenna hardware, beamforming unit, and beamforming algorithm in an independent manner, thus allowing the smart antenna system to be developed and tested in parallel, hence reduces the design time. The DBS was developed using a high-performance [InlineEquation not available: see fulltext.] floating-point DSP board and a 4-channel RF front-end receiver developed in-house. An interface board is designed to interface to the ADC board with the RF front-end receiver. A four-element receiving array testbed at 1.88-2.22 GHz frequency is constructed, and digital beamforming on this testbed is successfully demonstrated.

Shuttle antenna radome technology test program. Volume 2: Development of S-band antenna interface design

NASA Technical Reports Server (NTRS)

Kuhlman, E. A.; Baranowski, L. C.

1977-01-01

The effects of the Thermal Protection Subsystem (TPS) contamination on the space shuttle orbiter S band quad antenna due to multiple mission buildup are discussed. A test fixture was designed, fabricated and exposed to ten cycles of simulated ground and flight environments. Radiation pattern and impedance tests were performed to measure the effects of the contaminates. The degradation in antenna performance was attributed to the silicone waterproofing in the TPS tiles rather than exposure to the contaminating sources used in the test program. Validation of the accuracy of an analytical thermal model is discussed. Thermal vacuum tests with a test fixture and a representative S band quad antenna were conducted to evaluate the predictions of the analytical thermal model for two orbital heating conditions and entry from each orbit. The results show that the accuracy of predicting the test fixture thermal responses is largely dependent on the ability to define the boundary and ambient conditions. When the test conditions were accurately included in the analytical model, the predictions were in excellent agreement with measurements.

Optics Design for the U.S. SKA Technology Development Project Design Verification Antenna

NASA Technical Reports Server (NTRS)

Imbriale, W. A.; Baker, L.; Cortes-Medellin, G.

2012-01-01

The U.S. design concept for the Square Kilometer Array (SKA) program is based on utilizing a large number of 15 meter dish antennas. The Technology Development Project (TDP) is planning to design and build the first of these antennas to provide a demonstration of the technology and a solid base on which to estimate costs. This paper describes the performance of the selected optics design. It is a dual-shaped offset Gregorian design with a feed indexer that can accommodate corrugated horns, wide band single pixel feeds or phased array feeds.

A Modal Approach to Compact MIMO Antenna Design

NASA Astrophysics Data System (ADS)

Yang, Binbin

MIMO (Multiple-Input Multiple-Output) technology offers new possibilities for wireless communication through transmission over multiple spatial channels, and enables linear increases in spectral efficiency as the number of the transmitting and receiving antennas increases. However, the physical implementation of such systems in compact devices encounters many physical constraints mainly from the design of multi-antennas. First, an antenna's bandwidth decreases dramatically as its electrical size reduces, a fact known as antenna Q limit; secondly, multiple antennas closely spaced tend to couple with each other, undermining MIMO performance. Though different MIMO antenna designs have been proposed in the literature, there is still a lack of a systematic design methodology and knowledge of performance limits. In this dissertation, we employ characteristic mode theory (CMT) as a powerful tool for MIMO antenna analysis and design. CMT allows us to examine each physical mode of the antenna aperture, and to access its many physical parameters without even exciting the antenna. For the first time, we propose efficient circuit models for MIMO antennas of arbitrary geometry using this modal decomposition technique. Those circuit models demonstrate the powerful physical insight of CMT for MIMO antenna modeling, and simplify MIMO antenna design problem to just the design of specific antenna structural modes and a modal feed network, making possible the separate design of antenna aperture and feeds. We therefore develop a feed-independent shape synthesis technique for optimization of broadband multi-mode apertures. Combining the shape synthesis and circuit modeling techniques for MIMO antennas, we propose a shape-first feed-next design methodology for MIMO antennas, and designed and fabricated two planar MIMO antennas, each occupying an aperture much smaller than the regular size of lambda/2 x lambda/2. Facilitated by the newly developed source formulation for antenna stored

Structurally Integrated Antenna Concepts for HALE UAVs

NASA Technical Reports Server (NTRS)

Cravey, Robin L.; Vedeler, Erik; Goins, Larry; Young, W. Robert; Lawrence, Roland W.

2006-01-01

This technical memorandum describes work done in support of the Multifunctional Structures and Materials Team under the Vehicle Systems Program's ITAS (Integrated Tailored Aero Structures) Project during FY 2005. The Electromagnetics and Sensors Branch (ESB) developed three ultra lightweight antenna concepts compatible with HALE UAVs (High Altitude Long Endurance Unmanned Aerial Vehicles). ESB also developed antenna elements that minimize the interaction between elements and the vehicle to minimize the impact of wing flexure on the EM (electromagnetic) performance of the integrated array. In addition, computer models were developed to perform phase correction for antenna arrays whose elements are moving relative to each other due to wing deformations expected in HALE vehicle concepts. Development of lightweight, conformal or structurally integrated antenna elements and compensating for the impact of a lightweight, flexible structure on a large antenna array are important steps in the realization of HALE UAVs for microwave applications such as passive remote sensing and communications.

Deployable antenna phase A study

NASA Technical Reports Server (NTRS)

Schultz, J.; Bernstein, J.; Fischer, G.; Jacobson, G.; Kadar, I.; Marshall, R.; Pflugel, G.; Valentine, J.

1979-01-01

Applications for large deployable antennas were re-examined, flight demonstration objectives were defined, the flight article (antenna) was preliminarily designed, and the flight program and ground development program, including the support equipment, were defined for a proposed space transportation system flight experiment to demonstrate a large (50 to 200 meter) deployable antenna system. Tasks described include: (1) performance requirements analysis; (2) system design and definition; (3) orbital operations analysis; and (4) programmatic analysis.

Inflatable Antennas Support Emergency Communication

NASA Technical Reports Server (NTRS)

2010-01-01

Glenn Research Center awarded Small Business Innovation Research (SBIR) contracts to ManTech SRS Technologies, of Newport Beach, California, to develop thin film inflatable antennas for space communication. With additional funding, SRS modified the concepts for ground-based inflatable antennas. GATR (Ground Antenna Transmit and Receive) Technologies, of Huntsville, Alabama, licensed the technology and refined it to become the world s first inflatable antenna certified by the Federal Communications Commission. Capable of providing Internet access, voice over Internet protocol, e-mail, video teleconferencing, broadcast television, and other high-bandwidth communications, the systems have provided communication during the wildfires in California, after Hurricane Katrina in Mississippi, and following the 2010 Haiti earthquake.

Multiband Photonic Phased-Array Antenna

NASA Technical Reports Server (NTRS)

Tang, Suning

2015-01-01

A multiband phased-array antenna (PAA) can reduce the number of antennas on shipboard platforms while offering significantly improved performance. Crystal Research, Inc., has developed a multiband photonic antenna that is based on a high-speed, optical, true-time-delay beamformer. It is capable of simultaneously steering multiple independent radio frequency (RF) beams in less than 1,000 nanoseconds. This high steering speed is 3 orders of magnitude faster than any existing optical beamformer. Unlike other approaches, this technology uses a single controlling device per operation band, eliminating the need for massive optical switches, laser diodes, and fiber Bragg gratings. More importantly, only one beamformer is needed for all antenna elements.

Miniaturization of Microwave Ablation Antennas

NASA Astrophysics Data System (ADS)

Luyen, Hung

Microwave ablation (MWA) is a promising minimally invasive technique for the treatment of various types of cancers as well as non-oncological diseases. In MWA, an interstitial antenna is typically used to deliver microwave energy to the diseased tissue and heat it up to lethal temperature levels that induce cell death. The desired characteristics of the interstitial antenna include a narrow diameter to minimize invasiveness of the treatment, a low input reflection coefficient at the operating frequency, and a localized heating zone. Most interstitial MWA antennas are fed by coaxial cables and designed for operation at either 915 MHz or 2.45 GHz. Coax-fed MWA antennas are commonly equipped with coaxial baluns to achieve localized heating. However, the conventional implementation of coaxial baluns increases the overall diameters of the antennas and therefore make them more invasive. It is highly desirable to develop less invasive antennas with shorter active lengths and smaller diameters for MWA applications. In this work, we demonstrate the feasibility of using higher frequency microwaves for tissue ablation and present several techniques for decreasing diameters of MWA antennas. First, we investigated MWA at higher frequencies by conducting numerical and experimental studies to compare ablation performance at 10 GHz and 1.9 GHz. Simulation and ex vivo ablation experiment results demonstrate comparable ablation zone dimensions achieved at these two frequencies. Operating at higher frequencies enables interstitial antennas with shorter active lengths. This can be combined with smaller-diameter antenna designs to create less invasive applicators or allow integration of multiple radiating elements on a single applicator to have better control and customization of the heating patterns. Additionally, we present three different coax-fed antenna designs and a non-coaxial-based balanced antenna that have smaller-diameter configurations than conventional coax-fed balun

Review of Large Spacecraft Deployable Membrane Antenna Structures

NASA Astrophysics Data System (ADS)

Liu, Zhi-Quan; Qiu, Hui; Li, Xiao; Yang, Shu-Li

2017-11-01

The demand for large antennas in future space missions has increasingly stimulated the development of deployable membrane antenna structures owing to their light weight and small stowage volume. However, there is little literature providing a comprehensive review and comparison of different membrane antenna structures. Space-borne membrane antenna structures are mainly classified as either parabolic or planar membrane antenna structures. For parabolic membrane antenna structures, there are five deploying and forming methods, including inflation, inflation-rigidization, elastic ribs driven, Shape Memory Polymer (SMP)-inflation, and electrostatic forming. The development and detailed comparison of these five methods are presented. Then, properties of membrane materials (including polyester film and polyimide film) for parabolic membrane antennas are compared. Additionally, for planar membrane antenna structures, frame shapes have changed from circular to rectangular, and different tensioning systems have emerged successively, including single Miura-Natori, double, and multi-layer tensioning systems. Recent advances in structural configurations, tensioning system design, and dynamic analysis for planar membrane antenna structures are investigated. Finally, future trends for large space membrane antenna structures are pointed out and technical problems are proposed, including design and analysis of membrane structures, materials and processes, membrane packing, surface accuracy stability, and test and verification technology. Through a review of large deployable membrane antenna structures, guidance for space membrane-antenna research and applications is provided.

Generation and Sustainment of Plasma Rotation by ICRF Heating

NASA Astrophysics Data System (ADS)

Perkins, F. W.

2000-10-01

When tokamak plasmas are heated by the fundamental minority ion-cyclotron process, they are observed to rotate toroidally, even though this heating process introduces negligable angular momentum. This work proposes and evaluates a physics mechanism which resolves this apparent conflict. The argument has two elements. First, it is assumed that angular momentum transport is governed by a diffusion equation with a v_tor = 0 boundary condition at the plasma surface and a torque-density source. When the source consists of separated regions of positive and negative torque density, a finite central rotation velocity results, even though the volume integrated torque density - the angular momentum input - vanishes. Secondly, ions energized by the ICRF process can generate separated regions of positive and negative torque density. Heating increases their banana widths which leads to radial energetic-particle transport that must be balanced by neutralizing radial currents and a j_rB_pR torque density in the bulk plasma. Additional, comparable torque density results from collisional transfer of mechanical angular momentum from energetic particles to the bulk plasma and particle loss through banana particles impacting the wall. Monte-Carlo calculations utilizing the ORBIT code evaluate all sources of torque density and rigorously assure that no net angular momentum is introduced. Two models of ICRF heating, diffusive and instantaneous, give similar results. When the resonance location is on the LFS, the calculated rotation has the magnitude, profile, and co-current sense of Alcator C-Mod observations. For HFS resonance locations, the model predicts counter-current rotation. Scans of rotational profiles vs. resonance location, initial energy, particle loss, pitch, and qm will be presented as will the location of the velocity shear layer its scaling to a reactor.

One antenna, two antennae, big antennae, small: total antennae length, not bilateral symmetry, predicts odor-tracking performance in the American cockroach Periplaneta americana.

PubMed

Lockey, Jacob K; Willis, Mark A

2015-07-01

Determining the location of a particular stimulus is often crucial to an animal's survival. One way to determine the local distribution of an odor is to make simultaneous comparisons across multiple sensors. If the sensors detect differences in the distribution of an odor in space, the animal can then steer toward the source. American cockroaches, Periplaneta americana, have 4 cm long antennae and are thought to track odor plumes using a spatial sampling strategy, comparing the amount of odor detected between these bilateral sensors. However, it is not uncommon for cockroaches to lose parts of their antennae and still track a wind-borne odor to its source. We examined whether bilateral odor input is necessary to locate an odor source in a wind-driven environment and how the loss of increasing lengths of the antennae affects odor tracking. The tracking performances of individuals with two bilaterally symmetrical antennae of decreasing length were compared with antennal length-matched individuals with one antenna. Cockroaches with one antenna were generally able to track an odor plume to its source. In fact, the performances of unilaterally antennectomized individuals were statistically identical to those of their bilaterally symmetrical counterparts when the combined length of both antennae equaled the length of the single antenna of the antennectomized individuals. This suggests that the total length of available antennae influences odor tracking performance more than any specific piece of antenna, and that they may be doing something more complex than a simple bilateral comparison between their antennae. The possibility of an antenna-topic map is discussed. © 2015. Published by The Company of Biologists Ltd.

Development of 2-D horn-antenna millimeter-wave imaging device (HMID) for the plasma diagnostics.

PubMed

Nagayama, Y; Ito, N; Kuwahara, D; Tsuchiya, H; Yamaguchi, S

2017-04-01

The two-dimensional (2-D) Horn-antenna Millimeter-wave Imaging Device (HMID) has been developed for the O-mode Microwave Imaging Reflectometry (O-MIR) in the Large Helical Device (LHD). The detectable frequency range of the HMID is 23-33 GHz, which corresponds to the cutoff electron density of 0.8-1.5 × 10 19 m -3 in the O-MIR. The HMID is a 2-D imaging device that improves on the horn-antenna mixer array, which had been developed for the X-mode MIR in the LHD. In the HMID, the signal (RF) wave from the horn antenna is transmitted to the microstrip line by the finline transmitter, and this is mixed by the double-balanced-mixer with the local oscillation wave that is fed by a coaxial cable. By using the HMID, the MIR optical system can be significantly simplified.

Progress in integrated-circuit horn antennas for receiver applications. Part 1: Antenna design

NASA Technical Reports Server (NTRS)

Eleftheriades, George V.; Ali-Ahmad, Walid Y.; Rebeiz, Gabriel M.

1992-01-01

The purpose of this work is to present a systematic method for the design of multimode quasi-integrated horn antennas. The design methodology is based on the Gaussian beam approach and the structures are optimized for achieving maximum fundamental Gaussian coupling efficiency. For this purpose, a hybrid technique is employed in which the integrated part of the antennas is treated using full-wave analysis, whereas the machined part is treated using an approximate method. This results in a simple and efficient design process. The developed design procedure has been applied for the design of a 20, a 23, and a 25 dB quasi-integrated horn antennas, all with a Gaussian coupling efficiency exceeding 97 percent. The designed antennas have been tested and characterized using both full-wave analysis and 90 GHz/370 GHz measurements.

RF wave simulation for cold edge plasmas using the MFEM library

NASA Astrophysics Data System (ADS)

Shiraiwa, S.; Wright, J. C.; Bonoli, P. T.; Kolev, T.; Stowell, M.

2017-10-01

A newly developed generic electro-magnetic (EM) simulation tool for modeling RF wave propagation in SOL plasmas is presented. The primary motivation of this development is to extend the domain partitioning approach for incorporating arbitrarily shaped SOL plasmas and antenna to the TORIC core ICRF solver, which was previously demonstrated in the 2D geometry [S. Shiraiwa, et. al., "HISTORIC: extending core ICRF wave simulation to include realistic SOL plasmas", Nucl. Fusion in press], to larger and more complicated simulations by including a 3D realistic antenna and integrating RF rectified sheath potential model. Such an extension requires a scalable high fidelity 3D edge plasma wave simulation. We used the MFEM [http://mfem.org], open source scalable C++ finite element method library, and developed a Python wrapper for MFEM (PyMFEM), and then a radio frequency (RF) wave physics module in Python. This approach allows for building a physics layer rapidly, while separating the physics implementation being apart from the numerical FEM implementation. An interactive modeling interface was built on pScope [S Shiraiwa, et. al. Fusion Eng. Des. 112, 835] to work with an RF simulation model in a complicated geometry.

Reinstated JET ICRF ILA: Overview and Results

NASA Astrophysics Data System (ADS)

Dumortier, Pierre; Durodié, Frédéric; Blackman, Trevor; Helou, Walid; Jacquet, Philippe; Lerche, Ernesto; Monakhov, Igor; Noble, Craig; Bobkov, Volodymyr; Goulding, Richard; Kaufman, Michael; Van Eester, Dirk

2017-10-01

The works undertaken to reinstate the JET ICRF ILA are reviewed. The vacuum matching capacitors were replaced, an extensive calibration of all the measurements in the RF circuit was carried out, new simulation tools were created and new control algorithms were implemented for the - toroidal and poloidal - phase control of the array as well as for the matching of the second stage. A review of the contribution of the reinstated ILA to the JET programme during the last campaigns is given showing namely that the new controls allowed extending the range of the operation to lower (29MHz) and higher (51MHz) frequencies than previously achieved and allowed more flexible and reliable operation. Operation with coupled power levels up to 2.8MW and voltages up to 40kV was achieved. ILA results on plasma are discussed and emphasis is given to the features of interest for ITER.

Recent activities in printed Antennas at LeRC

NASA Technical Reports Server (NTRS)

Lee, Richard Q.; Simons, Rainee N.

1993-01-01

This paper will report two recent R&D efforts in printed antennas at NASA Lewis Research Center. These efforts are: (1) to enhance the current antenna performance in gain, bandwidth and pattern characteristics, and (2) to develop coplanar waveguide/aperture coupled feeding technique for dual excitation of a patch antenna. Research in area (1) has led to the development of a nonplanar linearly tapered slot antenna (LTSA) which has exhibited over 10 dB gain with broad bandwidth and excellent radiation patterns. This endfire antenna element is most suitable for use in MMIC arrays of 'brick' construction. A space power amplifier composed of active LTSA has been demonstrated and shown to have a gain of 30 dB at 20 GHz. In each of the antenna elements, a GaAs monolithic microwave integrated circuit (MMIC) three-stage power amplifier is integrated with two LTSA's. A single active LTSA has also been demonstrated and exhibited a power gain of 6.7 dB with the MMIC amplifier turned on. The aperture coupled feeding technique with coplanar waveguide feeds has demonstrated high coupling efficiency on both LTSA and patch antennas. Recent efforts have been focused on applying this technique for dual excitation (dual frequency and/or dual polarization) of a patch antenna. Preliminary results confirm the feasibility of this approach. Further development is required to improve the coupling efficiency and antenna radiation characteristics.

Advanced Microstrip Antenna Developments : Volume I. Technology Studies for Aircraft Phased Arrays

DOT National Transportation Integrated Search

1981-06-01

Work has continued on improvement of microstrip phased-array antenna technology since the first microstrip phased-array was flight-tested during the FAA 1974-1975 ATS-6 test program. The present development has extended this earlier work in three are...

Reconfigurable antenna pattern verification

NASA Technical Reports Server (NTRS)

Drexler, Jerome P. (Inventor); Becker, Robert C. (Inventor); Meyers, David W. (Inventor); Muldoon, Kelly P. (Inventor)

2013-01-01

A method of verifying programmable antenna configurations is disclosed. The method comprises selecting a desired antenna configuration from a plurality of antenna configuration patterns, with the selected antenna configuration forming at least one reconfigurable antenna from reconfigurable antenna array elements. The method validates the formation of the selected antenna configuration to determine antenna performance of the at least one reconfigurable antenna.

Ku-band multiple beam antenna

NASA Technical Reports Server (NTRS)

Chen, C. C.; Franklin, C. F.

1980-01-01

The frequency reuse capability is demonstrated for a Ku-band multiple beam antenna which provides contiguous low sidelobe spot beams for point-to-point communications between any two points within the continental United States (CONUS), or regional coverage beams for direct broadcast systems. A spot beam antenna in the 14/21 GHz band which provides contiguous overlapping beams covering CONUS and two discrete beams covering Hawaii and Alaska were designed, developed, and tested. Two reflector antennas are required for providing contiguous coverage of CONUS. Each is comprised of one offset parabolic reflector, one flat polarization diplexer, and two separate planar array feeds. This antenna system provides contiguous spot beam coverage of CONUS, utilizing 15 beams. Also designed, developed and demonstrated was a shaped contoured beam antenna system which provides contiguous four time zone coverage of CONUS from a single offset parabolic reflector incorporating one flat polarization diplexer and two separate planar array feeds. The beams which illuminate the eastern time zone and the mountain time zone are horizontally polarized, while the beams which illuminate the central time zone and the pacific time zone are vertically polarized. Frequency reuse is achieved by amplitude and polarization isolation.

CAD/CAM for development and fabrication of cosecant reflector antennas

NASA Astrophysics Data System (ADS)

Petri, U.

The application of CAD/CAM techniques to lower the cost of redesigning and manufacturing specialized cosecant reflector antennas for use in the mm-wave range is described and demonstrated. Consideration is given to the theoretical computation of reflector surfaces; the representation of a reflector surface in a CAD system; the numerically controlled milling of an Al, wood, or plastic model antenna; and the construction of the antenna (by spraying the 300-micron Sn-alloy conducting layer onto the coated model surface and then applying a 1-mm-thick epoxy-matrix GFRP layer, a 20-30-mm layer of flexible polyurethane foam, and a final GFRP layer). Diagrams and photographs are provided.

Development and evaluation of a boat-mounted RFID antenna for monitoring freshwater mussels

USGS Publications Warehouse

Fischer, Jesse R.; Neebling, Travis E.; Quist, Michael C.

2012-01-01

Development of radio frequency identification (RFID) technology and passive integrated transponder (PIT) tags has substantially increased the ability of researchers and managers to monitor populations of aquatic organisms. However, use of transportable RFID antenna systems (i.e., backpack-mounted) is currently limited to wadeable aquatic environments (<1.4 m water depth). We describe the design, construction, and evaluation of a boat-mounted RFID antenna to detect individually PIT-tagged benthic aquatic organisms (mussels). We evaluated the effects of tag orientation on detection distances in water with a 32-mm half-duplex PIT tag. Detection distances up to 50 cm from the antenna coils were obtained, but detection distance was dependent on tag orientation. We also evaluated detection distance of PIT tags beneath the sediment to simulate detection of burrowing mussels with 23- and 32-mm tags. In sand substrate, the maximum detection distance varied from 3.5 cm and 4.5 cm (vertical tag orientation) to 24.7 cm and 39.4 cm (45° tag orientation) for the 23- and 32-mm PIT tags, respectively. Our results suggest a 1.4-m total detection width for tagged mussels on the substrate surface by the boat-mounted antenna system regardless of tag orientation. However, burrowed mussels may require multiple passes to increase detection that would be influenced by depth, tag orientation, and tag size. Construction of the boat-mounted antenna was relatively low in cost (<500 USD) and had several advantages (less labor and time intensive, increased safety) over traditional mussel sampling techniques (diving, snorkeling) in nonwadeable habitats.

Equipment: Antenna systems

NASA Astrophysics Data System (ADS)

Petrie, L. E.

1983-05-01

Some antenna fundamentals as well as definitions of the principal terms used in antenna engineering are described. Methods are presented for determining the desired antenna radiation patterns for an HF communication circuit or service area. Sources for obtaining or computing radiation pattern information are outlined. Comparisons are presented between the measured and computed radiation patterns. The effect of the properties of the ground on the antenna gain and pattern are illustrated for several types of antennas. Numerous examples are given of the radiation patterns for typical antennas used on short, intermediate and long distance circuits or both mobile and fixed service operations. The application of adaptive antenna arrays and active antennas in modern HF communication systems are briefly reviewed.

Equipment: Antenna systems

NASA Astrophysics Data System (ADS)

Petrie, L. E.

1986-03-01

Some antenna fundamentals as well as definitions of the principal terms used in antenna engineering are described. Methods are presented for determining the desired antenna radiation patterns for HF communication circuit or service area. Sources for obtaining or computing radiation pattern information are outlined. Comparisons are presented between the measured and computed radiation patterns. The effect of the properties of the ground on the antenna gain and the pattern are illustrated for several types of antennas. Numerous examples are given of the radiation patterns for typical antennas used on short, intermediate and long distance circuits for both mobile and fixed service operations. The application of adaptive antenna arrays and active antennas in modern HF communication systems are briefly reviewed.

Development of a four-frequency selective surface prototype spacecraft antenna

NASA Astrophysics Data System (ADS)

Hickey, Gregory S.; Wu, Te-Kao

NASA-JPL's four-frequency telecommunication system design entails the creation and integration of a frequency-selective surface (FSS) subreflector into the high-gain antenna subsystem. The FSS design, which incorporates a periodic array of conducting elements on a kevlar/polymer composite structure, will be able to multiplex S, X, Ku, and Ka frequency-band wavelengths. Accounts are presented of the FSS's development, mechanical testing, and electrical testing.

Antenna Construction and Propagation of Radio Waves.

ERIC Educational Resources Information Center

Marine Corps Inst., Washington, DC.

Developed as part of the Marine Corps Institute (MCI) correspondence training program, this course on antenna construction and propagation of radio waves is designed to provide communicators with instructions in the selection and/or construction of the proper antenna(s) for use with current field radio equipment. Introductory materials include…

S-band antenna phased array communications system

NASA Technical Reports Server (NTRS)

Delzer, D. R.; Chapman, J. E.; Griffin, R. A.

1975-01-01

The development of an S-band antenna phased array for spacecraft to spacecraft communication is discussed. The system requirements, antenna array subsystem design, and hardware implementation are examined. It is stated that the phased array approach offers the greatest simplicity and lowest cost. The objectives of the development contract are defined as: (1) design of a medium gain active phased array S-band communications antenna, (2) development and test of a model of a seven element planar array of radiating elements mounted in the appropriate cavity matrix, and (3) development and test of a breadboard transmit/receive microelectronics module.

Numerical Modeling of Ultra Wideband Combined Antennas

NASA Astrophysics Data System (ADS)

Zorkal'tseva, M. Yu.; Koshelev, V. I.; Petkun, A. A.

2017-12-01

With the help of a program we developed, based on the finite difference method in the time domain, we have investigated the characteristics of ultra wideband combined antennas in detail. The antennas were developed to radiate bipolar pulses with durations in the range 0.5-3 ns. Data obtained by numerical modeling are compared with the data of experimental studies on antennas and have been used in the synthesis of electromagnetic pulses with maximum field strength.

Antenna Technologies for Future NASA Exploration Missions

NASA Technical Reports Server (NTRS)

Miranda, Felix A.

2006-01-01

NASA s plans for the manned exploration of the moon and Mars will rely heavily on the development of a reliable communications infrastructure on the surface and back to Earth. Future missions will thus focus not only on gathering scientific data, but also on the formation of the communications network. In either case, unique requirements become imposed on the antenna technologies necessary to accomplish these tasks. For example, surface activity applications such as robotic rovers, human extravehicular activities (EVA), and probes will require small size, lightweight, low power, multi-functionality, and robustness for the antenna elements being considered. Trunk-line communications to a centralized habitat on the surface and back to Earth (e.g., surface relays, satellites, landers) will necessitate wide-area coverage, high gain, low mass, deployable antennas. Likewise, the plethora of low to high data rate services desired to guarantee the safety and quality of mission data for robotic and human exploration will place additional demands on the technology. Over the past year, NASA Glenn Research Center has been heavily involved in the development of candidate antenna technologies with the potential for meeting these strict requirements. This technology ranges from electrically small antennas to phased array and large inflatable structures. A summary of this overall effort is provided, with particular attention being paid to small antenna designs and applications. A discussion of the Agency-wide activities of the Exploration Systems Mission Directorate (ESMD) in forthcoming NASA missions, as they pertain to the communications architecture for the lunar and Martian networks is performed, with an emphasis on the desirable qualities of potential antenna element designs for envisioned communications assets. Identified frequency allocations for the lunar and Martian surfaces, as well as asset-specific data services will be described to develop a foundation for viable

Design of a C- Band Circular Polarization Microstrip Antenna

NASA Astrophysics Data System (ADS)

Yohandri; Jumiah, Yusna; Tetuko Sri Sumantyo, Josaphat

2018-04-01

The development of circularly polarized microstrip antenna is an interesting topic in current research, due to its superiority in various applications. In this work, the design of a circular polarization antenna that will be operated in the C-band range will be described. The developed antenna is intended to be used for Synthetic Aperture Radar (SAR) applications. Through this application, various targets or areas on the surface of the earth, such as buildings, soil and land can be observed. To get the ideal antenna characteristic, in this research the various parameters in antenna design will be simulated. A software CST Studio will be operated in this simulation. Based on the simulation results, the optimum parameters are obtained in term of reflection coefficient, VSWR, axial ratio, and gain. The reflection coefficient of the antenna (S11) is obtained at -19.75 dB and VSWR of 1.23. Meanwhile, the axial ratio and gain of the antenna were obtained at 2.66 dB and 2.1 dBi, respectively. Based on this simulated results, antenna design is potential to be developed and fabricated for SAR sensor applications.

Development of long-pulse heating & current drive actuators & operational techniques compatible with a high-Z divertor & first wall

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

Tynan, George

This was a collaboration between UCSD and MIT to study the effective application of ion-cyclotron heating (ICRH) on the EAST tokamak, located in China. The original goal was for UCSD to develop a diagnostic that would allow measurement of the steady state, or DC, convection pattern that develops on magnetic field lines that attach or connect to the ICRH antenna. This diagnostic would then be used to develop techniques and approaches that minimize or even eliminate such DC convection during application of strong ICRH heating. This was thought to then indicate reduction or elimination of parasitic losses of heating power,more » and thus be an indicator of effective RF heating. The original plan to use high speed digital gas-puff imaging (GPI) of the antenna-edge plasma region in EAST was ultimately unsuccessful due to limitations in machine and camera operations. We then decided to attempt the same experiment on the ALCATOR C-MOD tokamak at MIT which had a similar instrument already installed. This effort was ultimately successful, and demonstrated that the underlying idea of using GPI as a diagnostic for ICRH antenna physics would, in fact, work. The two-dimensional velocity fields of the turbulent structures, which are advected by RF-induced E x B flows, are obtained via the time-delay estimation (TDE) techniques. Both the magnitude and radial extension of the radial electric field E-r were observed to increase with the toroidal magnetic field strength B and the ICRF power. The TDE estimations of RF-induced plasma potentials are consistent with previous results based on the probe measurements of poloidal phase velocity. The results suggest that effective ICRH heating with reduced impurity production is possible when the antenna/box system is designed so as to reduce the RF-induced image currents that flow in the grounded conducting antenna frame elements that surround the RF antenna current straps.« less

Test and Analysis of an Inflatable Parabolic Dish Antenna

NASA Technical Reports Server (NTRS)

Gaspar, james L.; Sreekantamurthy, Tham; Mann, Troy; Behun, Vaughn; Romanofsky, Robert; Lambert, Kevin; Pearson, James

2006-01-01

NASA is developing ultra-lightweight structures technology for large communication antennas for application to space missions. With these goals in mind, SRS Technologies has been funded by NASA Glenn Research Center (GRC) to undertake the development of a subscale ultra-thin membrane inflatable antenna for deep-space applications. One of the research goals is to develop approaches for prediction of the radio frequency and structural characteristics of inflatable and rigidizable membrane antenna structures. GRC has teamed with NASA Langley Research Center (LaRC) to evaluate inflatable and rigidizable antenna concepts for potential space missions. GRC has completed tests to evaluate RF performance, while LaRC completed structural tests and analysis to evaluate the static shape and structural dynamic responses of a laboratory model of a 0.3 meter antenna. This paper presents the details of the tests and analysis completed to evaluate the radio frequency and structural characteristics of the antenna.

Downsizing Antenna Technologies for Mobile and Satellite Communications

NASA Technical Reports Server (NTRS)

Huang, J.; Densmore, A.; Tulintseff, A.; Jamnejad, V.

1993-01-01

Due to the increasing and stringent functional requirements (larger capacity, longer distances, etc.) of modern day communication systems, higher antenna gains are generally needed. This higher gain implies larger antenna size and mass which are undesirable to many systems. Consequently, downsizing antenna technology becomes one of the most critical areas for research and development efforts. Techniques to reduce antenna size can be categorized and are briefly discussed.

Magnetic antenna excitation of whistler modes. IV. Receiving antennas and reciprocity

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

Stenzel, R. L., E-mail: stenzel@physics.ucla.edu; Urrutia, J. M.

Antenna radiation patterns are an important property of antennas. Reciprocity holds in free space and the radiation patterns for exciting and receiving antennas are the same. In anisotropic plasmas, radiation patterns are complicated by the fact that group and phase velocities differ and certain wave properties like helicity depend on the direction of wave propagation with respect to the background magnetic field B{sub 0}. Interference and wave focusing effects are different than in free space. Reciprocity does not necessarily hold in a magnetized plasma. The present work considers the properties of various magnetic antennas used for receiving whistler modes. Itmore » is based on experimental data from exciting low frequency whistler modes in a large uniform laboratory plasma. By superposition of linear waves from different antennas, the radiation patterns of antenna arrays are derived. Plane waves are generated and used to determine receiving radiation patterns of different receiving antennas. Antenna arrays have radiation patterns with narrow lobes, whose angular position can be varied by physical rotation or electronic phase shifting. Reciprocity applies to broadside antenna arrays but not to end fire arrays which can have asymmetric lobes with respect to B{sub 0}. The effect of a relative motion between an antenna and the plasma has been modeled by the propagation of a short wave packet moving along a linear antenna array. An antenna moving across B{sub 0} has a radiation pattern characterized by an oscillatory “whistler wing.” A receiving antenna in motion can detect any plane wave within the group velocity resonance cone. The radiation pattern also depends on loop size relative to the wavelength. Motional effects prevent reciprocity. The concept of the radiation pattern loses its significance for wave packets since the received signal does not only depend on the antenna but also on the properties of the wave packet. The present results are of

The development and testing of the Lens Antenna Deployment Demonstration (LADD) test article

NASA Technical Reports Server (NTRS)

Pugh, Mark L.; Denton, Robert J., Jr.; Strange, Timothy J.

1993-01-01

The USAF Rome Laboratory and NASA Marshall Space Flight Center, through contract to Grumman Corporation, have developed a space-qualifiable test article for the Strategic Defense Initiative Organization to demonstrate the critical structural and mechanical elements of single-axis roll-out membrane deployment for Space Based Radar (SBR) applications. The Lens Antenna Deployment Demonstration (LADD) test article, originally designed as a shuttle-attached flight experiment, is a large precision space structure which is representative of operational designs for space-fed lens antennas. Although the flight experiment was cancelled due to funding constraints and major revisions in the Strategic Defense System (SDS) architecture, development of this test article was completed in June 1989. To take full advantage of the existence of this unique structure, a series of ground tests are proposed which include static, dynamic, and thermal measurements in a simulated space environment. An equally important objective of these tests is the verification of the analytical tools used to design and develop large precision space structures.

Simulation of cold magnetized plasmas with the 3D electromagnetic software CST Microwave Studio®

NASA Astrophysics Data System (ADS)

Louche, Fabrice; Křivská, Alena; Messiaen, André; Wauters, Tom

2017-10-01

Detailed designs of ICRF antennas were made possible by the development of sophisticated commercial 3D codes like CST Microwave Studio® (MWS). This program allows for very detailed geometries of the radiating structures, but was only considering simple materials like equivalent isotropic dielectrics to simulate the reflection and the refraction of RF waves at the vacuum/plasma interface. The code was nevertheless used intensively, notably for computing the coupling properties of the ITER ICRF antenna. Until recently it was not possible to simulate gyrotropic medias like magnetized plasmas, but recent improvements have allowed programming any material described by a general dielectric or/and diamagnetic tensor. A Visual Basic macro was developed to exploit this feature and was tested for the specific case of a monochromatic plane wave propagating longitudinally with respect to the magnetic field direction. For specific cases the exact solution can be expressed in 1D as the sum of two circularly polarized waves connected by a reflection coefficient that can be analytically computed. Solutions for stratified media can also be derived. This allows for a direct comparison with MWS results. The agreement is excellent but accurate simulations for realistic geometries require large memory resources that could significantly restrict the possibility of simulating cold plasmas to small-scale machines.

The design, development and qualification of a lightweight antenna pointing mechanism

NASA Technical Reports Server (NTRS)

Shmulevitz, M.; Halsband, A.

1996-01-01

This paper describes the design, development, and qualification of a new lightweight and compact Antenna Pointing Mechanism (APM). The APM was specially designed to meet the stringent mass, envelope, and environmental requirements of OFFEQ experimental satellite. During the development phase, some problems were encountered with the brushless DC motors, slip ring contact resistance, and bearing drag torque. All of these problems were resolved, and two APM units have been operating successfully in orbit since April, 1995.

Extending the ICRF into the Infrared: 2MASS - UCAC Astrometry

NASA Technical Reports Server (NTRS)

Zacharias, Norbert; McCallon, Howard L.; Kopan, Eugene; Cutri, Roc M.

2000-01-01

An external comparison between the infrared 2MASS and the optical UCAC positions was performed, both being on the same system, the ICRS. About 48 million sources in common were identified. Random errors of the 2MASS catalog positions are about 60 to 70 mas per coordinate for the Ks = 4 to 14 range, increasing to about 100 to 150 mas for saturated and very faint stars. Systematic position differences between the 2 catalogs are very small, about 5 to 10 mas as a function of magnitude and color, with somewhat larger errors as a function of right ascension and declination. The extension of the ICRF into the infrared has become a reality.

An Overview of Antenna R&D Efforts in Support of NASA's Space Exploration Vision

NASA Technical Reports Server (NTRS)

Manning, Robert M.

2007-01-01

This presentation reviews the research and development work being conducted at Glenn Research Center in the area of antennas for space exploration. In particular, after reviewing the related goals of the agency, antenna technology development at GRC is discussed. The antennas to be presented are large aperture inflatable antennas, phased array antennas, a 256 element Ka-band antenna, a ferroelectric reflectarray antenna, multibeam antennas, and several small antennas.

Modeling and analysis of the DSS-14 antenna control system

NASA Technical Reports Server (NTRS)

Gawronski, W.; Bartos, R.

1996-01-01

An improvement of pointing precision of the DSS-14 antenna is planned for the near future. In order to analyze the improvement limits and to design new controllers, a precise model of the antenna and the servo is developed, including a finite element model of the antenna structure and detailed models of the hydraulic drives and electronic parts. The DSS-14 antenna control system has two modes of operation: computer mode and precision mode. The principal goal of this investigation is to develop the model of the computer mode and to evaluate its performance. The DSS-14 antenna computer model consists of the antenna structure and drives in azimuth and elevation. For this model, the position servo loop is derived, and simulations of the closed-loop antenna dynamics are presented. The model is significantly different from that for the 34-m beam-waveguide antennas.

Integrated reflector antenna design and analysis

NASA Technical Reports Server (NTRS)

Zimmerman, M. L.; Lee, S. W.; Ni, S.; Christensen, M.; Wang, Y. M.

1993-01-01

Reflector antenna design is a mature field and most aspects were studied. However, of that most previous work is distinguished by the fact that it is narrow in scope, analyzing only a particular problem under certain conditions. Methods of analysis of this type are not useful for working on real-life problems since they can not handle the many and various types of perturbations of basic antenna design. The idea of an integrated design and analysis is proposed. By broadening the scope of the analysis, it becomes possible to deal with the intricacies attendant with modem reflector antenna design problems. The concept of integrated reflector antenna design is put forward. A number of electromagnetic problems related to reflector antenna design are investigated. Some of these show how tools for reflector antenna design are created. In particular, a method for estimating spillover loss for open-ended waveguide feeds is examined. The problem of calculating and optimizing beam efficiency (an important figure of merit in radiometry applications) is also solved. Other chapters deal with applications of this general analysis. The wide angle scan abilities of reflector antennas is examined and a design is proposed for the ATDRSS triband reflector antenna. The development of a general phased-array pattern computation program is discussed and how the concept of integrated design can be extended to other types of antennas is shown. The conclusions are contained in the final chapter.

Development of the 15 meter diameter hoop column antenna

NASA Technical Reports Server (NTRS)

1986-01-01

The building of a deployable 15-meter engineering model of the 100 meter antenna based on the point-design of an earlier task of this contract, complete with an RF-capable surface is described. The 15 meter diameter was selected so that the model could be tested in existing manufacturing, near-field RF, thermal vacuum, and structural dynamics facilities. The antenna was designed with four offset paraboloidal reflector surfaces with a focal length of 366.85 in and a primary surface accuracy goal of .069 in rms. Surface adjustment capability was provided by manually resetting the length of 96 surface control cords which emanated from the lower column extremity. A detailed description of the 15-meter Hoop/Column Antenna, major subassemblies, and a history of its fabrication, assembly, deployment testing, and verification measurements are given. The deviation for one aperture surface (except the outboard extremity) was measured after adjustments in follow-on tests at the Martin Marietta Near-field Facility to be .061 in; thus the primary surface goal was achieved.

A predictive transport modeling code for ICRF-heated tokamaks

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

Phillips, C.K.; Hwang, D.Q.; Houlberg, W.

In this report, a detailed description of the physic included in the WHIST/RAZE package as well as a few illustrative examples of the capabilities of the package will be presented. An in depth analysis of ICRF heating experiments using WHIST/RAZE will be discussed in a forthcoming report. A general overview of philosophy behind the structure of the WHIST/RAZE package, a summary of the features of the WHIST code, and a description of the interface to the RAZE subroutines are presented in section 2 of this report. Details of the physics contained in the RAZE code are examined in section 3.more » Sample results from the package follow in section 4, with concluding remarks and a discussion of possible improvements to the package discussed in section 5.« less

A predictive transport modeling code for ICRF-heated tokamaks

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

Phillips, C.K.; Hwang, D.Q.; Houlberg, W.

1992-02-01

In this report, a detailed description of the physic included in the WHIST/RAZE package as well as a few illustrative examples of the capabilities of the package will be presented. An in depth analysis of ICRF heating experiments using WHIST/RAZE will be discussed in a forthcoming report. A general overview of philosophy behind the structure of the WHIST/RAZE package, a summary of the features of the WHIST code, and a description of the interface to the RAZE subroutines are presented in section 2 of this report. Details of the physics contained in the RAZE code are examined in section 3.more » Sample results from the package follow in section 4, with concluding remarks and a discussion of possible improvements to the package discussed in section 5.« less

Mobile SATCOM Antenna Developments and Experimental Results of Land- and Aeronautical -Mobile Field Trials

NASA Technical Reports Server (NTRS)

Densmore, A. C.; Huang, J.

1996-01-01

This paper discusses several mobile satcom antenna systems that the Jet Propulsion Laboratory (JPL) has developed and demonstrated during the last ten years for land -and aeronautical mobile digital audio/data/video satellite communication.

Development and Qualification of an Antenna Pointing Mechanism for the ExoMars High-Gain Antenna

NASA Astrophysics Data System (ADS)

St-Andre, Stephane; Dumais, Marie-Christine; Lebel, Louis-Philippe; Langevin, Jean-Paul; Horth, Richard; Winton, Alistair; Lebleu, Denis

2015-09-01

The European Space Agency ExoMars 2016 mission required a gimbaled High Gain Antenna (HGA) for orbiter-to-earth communications. The ExoMars Program is a cooperative program between ESA and ROSCOSMOS with participation of NASA. The ExoMars Program industrial consortium is led by THALES ALENIA SPACE.This paper presents the design and qualification test results of the Antenna Pointing Mechanism (APM) used to point the HGA towards Earth. This electrically redundant APM includes motors, drive trains, optical encoders, cable cassette and RF Rotary Joints.Furthermore, the paper describes the design, development and the qualification approach applied to this APM. The design challenges include a wide pointing domain necessary to maximise the communication duty cycle during the early operation phase, the interplanetary cruise phase and during the mission’s orbital science phase. Other design drivers are an extended rotation cycle life with very low backlash yielding little wear and accurate position feedback on both axes. Major challenges and related areas of development include:• Large moments are induced on the APM due to aerobraking forces when the Mars atmosphere is used to slow the orbiter into its science mission orbit,• Thermal control of the critical components of the APM due to the different environments of the various phases of the mission. Also, the large travel range of the actuators complicated the radiator design in order to maintain clearances and to avoid overheating.• The APM, with a mass less than 17.5 kg, is exposed to a demanding dynamic environment due to its mounting on the spacecraft thrust tube and aggravated by its elevated location on the payload.• Power and Data transmission between elevation and azimuth axes through a compact large rotation range spiral type cable cassette.• Integration of a 16 bit redundant encoder on both axes for position feedback: Each encoder is installed on the back of a rotary actuator and is coupled using the

Conformal Lightweight Antenna Structures for Aeronautical Communication Technologies

NASA Technical Reports Server (NTRS)

Meador, Mary Ann

2017-01-01

This project is to develop antennas which enable beyond line of sight (BLOS) command and control for UAVs. We will take advantage of newly assigned provisional Ku-band spectrum for UAVs and use unique antenna designs to avoid interference with ground systems. This will involve designing antennas with high isotropic effective radiated power (EIRP) and ultra-low sidelobes. The antennas will be made with polymer aerogel as a substrate to both reduce weight and improve performance, as demonstrated in an Aero Seedling. In addition, designing the antennas to be conformal to the aircraft fuselage will reduce drag.

Antenna theory: Analysis and design

NASA Astrophysics Data System (ADS)

Balanis, C. A.

The book's main objective is to introduce the fundamental principles of antenna theory and to apply them to the analysis, design, and measurements of antennas. In a description of antennas, the radiation mechanism is discussed along with the current distribution on a thin wire. Fundamental parameters of antennas are examined, taking into account the radiation pattern, radiation power density, radiation intensity, directivity, numerical techniques, gain, antenna efficiency, half-power beamwidth, beam efficiency, bandwidth, polarization, input impedance, and antenna temperature. Attention is given to radiation integrals and auxiliary potential functions, linear wire antennas, loop antennas, linear and circular arrays, self- and mutual impedances of linear elements and arrays, broadband dipoles and matching techniques, traveling wave and broadband antennas, frequency independent antennas and antenna miniaturization, the geometrical theory of diffraction, horns, reflectors and lens antennas, antenna synthesis and continuous sources, and antenna measurements.

Fundamental Fractal Antenna Design Process

NASA Astrophysics Data System (ADS)

Zhu, L. P.; Kim, T. C.; Kakas, G. D.

2017-12-01

Antenna designers are always looking to come up with new ideas to push the envelope for new antennas, using a smaller volume while striving for higher bandwidth, wider bandwidth, and antenna gain. One proposed method of increasing bandwidth or shrinking antenna size is via the use of fractal geometry, which gives rise to fractal antennas. Fractals are those fun shapes that if one zooms in or zoom out, the structure is always the same. Design a new type of antenna based on fractal antenna design by utilize the Design of Experiment (DOE) will be shown in fractal antenna design process. Investigate conformal fractal antenna design for patterns, dimensions, and size, of the antenna but maintaining or improving the antenna performance. Research shows an antenna designer how to create basic requirements of the fractal antenna through a step by step process, and provides how to optimize the antenna design with the model prediction, lab measurement, and actual results from the compact range measurement on the antenna patterns.

View north of the antenna array, note the communications antenna ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

View north of the antenna array, note the communications antenna in the middleground - Over-the-Horizon Backscatter Radar Network, Christmas Valley Radar Site Transmit Sector Four Antenna Array, On unnamed road west of Lost Forest Road, Christmas Valley, Lake County, OR

View of antenna tunnel end. Right to Antenna Silo #1, ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

View of antenna tunnel end. Right to Antenna Silo #1, left to Antenna Silo #2 - Titan One Missile Complex 2A, .3 miles west of 129 Road and 1.5 miles north of County Line Road, Aurora, Adams County, CO

L-Band Orthogonal-Mode Crossed-Slot Antenna and VHF Crossed-Loop Antenna

DOT National Transportation Integrated Search

1972-01-01

A low-gain, circularly polarized, L-ban antenna; a low-gain, lineraly polarized, L-band antenna; and a low-gain, lineraly polarized, L-ban antenna; and a low-gain, circularly polarized, upper hemisphere, VHF satellite communications antenna intended ...

Investigation of high temperature antennas for space shuttle

NASA Technical Reports Server (NTRS)

Kuhlman, E. A.

1973-01-01

The design and development of high temperature antennas for the space shuttle orbiter are discussed. The antenna designs were based on three antenna types, an annular slot (L-Band), a linear slot (C-Band), and a horn (C-Band). The design approach was based on combining an RF window, which provides thermal protection, with an off-the-shelf antenna. Available antenna window materials were reviewed and compared, and the materials most compatible with the design requirements were selected. Two antenna window design approaches were considered: one employed a high temperature dielectric material and a low density insulation material, and the other an insulation material usable for the orbiter thermal protection system. Preliminary designs were formulated and integrated into the orbiter structure. Simple electrical models, with a series of window configurations, were constructed and tested. The results of tests and analyses for the final antenna system designs are given and show that high temperature antenna systems consisting of off-the-shelf antennas thermally protected by RF windows can be designed for the Space Shuttle Orbiter.

Compact Directional Microwave Antenna for Localized Heating

NASA Technical Reports Server (NTRS)

Fink, Patrick W.; Lin, Gregory Y.; Chu, Andrew W.; Dobbins, Justin A.; Arndt, G. Dickey; Ngo, Phong

2008-01-01

A directional, catheter-sized cylindrical antenna has been developed for localized delivery of microwave radiation for heating (and thus killing) diseased tissue without excessively heating nearby healthy tissue. By "localized" is meant that the antenna radiates much more in a selected azimuthal direction than in the opposite radial direction, so that it heats tissue much more on one side than it does on the opposite side. This antenna can be inserted using either a catheter or a syringe. A 2.4-mm prototype was tested, although smaller antennas are possible. Prior compact, cylindrical antennas designed for therapeutic localized hyperthermia do not exhibit such directionality; that is, they radiate in approximately axisymmetric patterns. Prior directional antennas designed for the same purpose have been, variously, (1) too large to fit within catheters or (2) too large, after deployment from catheters, to fit within the confines of most human organs. In contrast, the present antenna offers a high degree of directionality and is compact enough to be useable as a catheter in some applications.

Antenna Controller Replacement Software

NASA Technical Reports Server (NTRS)

Chao, Roger Y.; Morgan, Scott C.; Strain, Martha M.; Rockwell, Stephen T.; Shimizu, Kenneth J.; Tehrani, Barzia J.; Kwok, Jaclyn H.; Tuazon-Wong, Michelle; Valtier, Henry; Nalbandi, Reza;

A survey of various enhancement techniques for square rings antennas

NASA Astrophysics Data System (ADS)

Mumin, Abdul Rashid O.; Alias, Rozlan; Abdullah, Jiwa; Abdulhasan, Raed Abdulkareem; Ali, Jawad; Dahlan, Samsul Haimi; Awaleh, Abdisamad A.

2017-09-01

The square ring shape becomes a famous reconfiguration on antenna design. The researchers have been developed the square ring by different configurations. It has high efficiency and simple calculation method. The performance enhancement for an antenna is the main reason to use this setting. Furthermore, the multi-objectives for the antenna also are considered. In this paper, different studies of square ring shape are discussed. This shape is developed in five different techniques, which are the gain enhancement, dual band antenna, reconfigurable antenna, CSRR, and circularly polarization. Moreover, the validation between these configurations also demonstrates for square ring shapes. In particular, the square ring slot improved the gain by 4.3 dB, provide dual band resonance at 1.4 and 2.6 GHz while circular polarization at 1.54 GHz, and multi-mode antenna. However, square ring strip achieved an excellent band rejection on UWB antenna at 5.5 GHz. The square ring slot length is the most influential factor on the antenna performance, which refers to the free space wavelength. Finally, comparisons between these techniques are presented.

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

Vdovin V.L.

In this report we describe theory and 3D full wave code description for the wave excitation, propagation and absorption in 3-dimensional (3D) stellarator equilibrium high beta plasma in ion cyclotron frequency range (ICRF). This theory forms a basis for a 3D code creation, urgently needed for the ICRF heating scenarios development for the operated LHD, constructed W7-X, NCSX and projected CSX3 stellarators, as well for re evaluation of ICRF scenarios in operated tokamaks and in the ITER . The theory solves the 3D Maxwell-Vlasov antenna-plasma-conducting shell boundary value problem in the non-orthogonal flux coordinates ({Psi}, {theta}, {var_phi}), {Psi} being magneticmore » flux function, {theta} and {var_phi} being the poloidal and toroidal angles, respectively. All basic physics, like wave refraction, reflection and diffraction are self consistently included, along with the fundamental ion and ion minority cyclotron resonances, two ion hybrid resonance, electron Landau and TTMP absorption. Antenna reactive impedance and loading resistance are also calculated and urgently needed for an antenna -generator matching. This is accomplished in a real confining magnetic field being varying in a plasma major radius direction, in toroidal and poloidal directions, through making use of the hot dense plasma wave induced currents with account to the finite Larmor radius effects. We expand the solution in Fourier series over the toroidal ({var_phi}) and poloidal ({theta}) angles and solve resulting ordinary differential equations in a radial like {Psi}-coordinate by finite difference method. The constructed discretization scheme is divergent-free one, thus retaining the basic properties of original equations. The Fourier expansion over the angle coordinates has given to us the possibility to correctly construct the ''parallel'' wave number k{sub //}, and thereby to correctly describe the ICRF waves absorption by a hot plasma. The toroidal harmonics are tightly coupled with

Spacecraft Antennas

NASA Technical Reports Server (NTRS)

Jamnejad, Vahraz; Manshadi, Farzin; Rahmat-Samii, Yahya; Cramer, Paul

1990-01-01

Some of the various categories of issues that must be considered in the selection and design of spacecraft antennas for a Personal Access Satellite System (PASS) are addressed, and parametric studies for some of the antenna concepts to help the system designer in making the most appropriate antenna choice with regards to weight, size, and complexity, etc. are provided. The question of appropriate polarization for the spacecraft as well as for the User Terminal Antenna required particular attention and was studied in some depth. Circular polarization seems to be the favored outcome of this study. Another problem that has generally been a complicating factor in designing the multiple beam reflector antennas, is the type of feeds (single vs. multiple element and overlapping vs. non-overlapping clusters) needed for generating the beams. This choice is dependent on certain system design factors, such as the required frequency reuse, acceptable interbeam isolation, antenna efficiency, number of beams scanned, and beam-forming network (BFN) complexity. This issue is partially addressed, but is not completely resolved. Indications are that it may be possible to use relatively simple non-overlapping clusters of only a few elements, unless a large frequency reuse and very stringent isolation levels are required.

Structural Test and Analysis of a Hybrid Inflatable Antenna

NASA Technical Reports Server (NTRS)

Gaspar, James L.; Mann, Troy; Sreekantamurthy, Tham; Behun, Vaughn

2007-01-01

NASA is developing ultra-lightweight structures technology for communication antennas for space missions. One of the research goals is to evaluate the structural characteristics of inflatable and rigidizable antennas through test and analysis. Being able to test and analyze the structural characteristics of a full scale antenna is important to enable the simulation of various mission scenarios to determine system performance in space. Recent work completed to evaluate a Hybrid Inflatable Antenna concept will be discussed. Tests were completed on a 2-m prototype to optimize its static shape and identify its modal dynamics that are important for analytical model validation. These test results were used to evaluate a preliminary finite element model of the antenna, and this model development and correlation activity is also described in the paper.

Antenna Allocation in MIMO Radar with Widely Separated Antennas for Multi-Target Detection

PubMed Central

Gao, Hao; Wang, Jian; Jiang, Chunxiao; Zhang, Xudong

2014-01-01

In this paper, we explore a new resource called multi-target diversity to optimize the performance of multiple input multiple output (MIMO) radar with widely separated antennas for detecting multiple targets. In particular, we allocate antennas of the MIMO radar to probe different targets simultaneously in a flexible manner based on the performance metric of relative entropy. Two antenna allocation schemes are proposed. In the first scheme, each antenna is allocated to illuminate a proper target over the entire illumination time, so that the detection performance of each target is guaranteed. The problem is formulated as a minimum makespan scheduling problem in the combinatorial optimization framework. Antenna allocation is implemented through a branch-and-bound algorithm and an enhanced factor 2 algorithm. In the second scheme, called antenna-time allocation, each antenna is allocated to illuminate different targets with different illumination time. Both antenna allocation and time allocation are optimized based on illumination probabilities. Over a large range of transmitted power, target fluctuations and target numbers, both of the proposed antenna allocation schemes outperform the scheme without antenna allocation. Moreover, the antenna-time allocation scheme achieves a more robust detection performance than branch-and-bound algorithm and the enhanced factor 2 algorithm when the target number changes. PMID:25350505

Antenna allocation in MIMO radar with widely separated antennas for multi-target detection.

PubMed

Gao, Hao; Wang, Jian; Jiang, Chunxiao; Zhang, Xudong

2014-10-27

In this paper, we explore a new resource called multi-target diversity to optimize the performance of multiple input multiple output (MIMO) radar with widely separated antennas for detecting multiple targets. In particular, we allocate antennas of the MIMO radar to probe different targets simultaneously in a flexible manner based on the performance metric of relative entropy. Two antenna allocation schemes are proposed. In the first scheme, each antenna is allocated to illuminate a proper target over the entire illumination time, so that the detection performance of each target is guaranteed. The problem is formulated as a minimum makespan scheduling problem in the combinatorial optimization framework. Antenna allocation is implemented through a branch-and-bound algorithm and an enhanced factor 2 algorithm. In the second scheme, called antenna-time allocation, each antenna is allocated to illuminate different targets with different illumination time. Both antenna allocation and time allocation are optimized based on illumination probabilities. Over a large range of transmitted power, target fluctuations and target numbers, both of the proposed antenna allocation schemes outperform the scheme without antenna allocation. Moreover, the antenna-time allocation scheme achieves a more robust detection performance than branch-and-bound algorithm and the enhanced factor 2 algorithm when the target number changes.

In-Space Deployable Reflectarray Antenna: Current and Future

NASA Technical Reports Server (NTRS)

Fang, Houfei; Knarr, Kevin; Quijano, Ubaldo; Huang, John; Thomson, Mark

2008-01-01

Technologies associated with a 10-m X/Ka-band dual-frequency reflectarray antenna have been developed for deep space communication applications. The first task is the development of a 3-m diameter X/Ka dual frequency reflectarray which serves as a stepping-stone to the 10-m aperture antenna. The second task is to develop a deployable frame.

Implantable ferrite antenna for biomedical applications

NASA Astrophysics Data System (ADS)

Fazeli, Maxwell L.

We have developed an implantable microstrip patch antenna with dimensions of 10x10x1.28 mm, operating around the Industrial, Scientific and Medical (ISM) band (2.4-2.5 GHz). The antenna is characterized in skin-mimicking gels and compared with simulation results. The experimental measurements are in good agreement with simulations, having a -16 dB reflection coefficient and -18 dBi realized gain at resonance, with a 185 MHz -10 dB bandwidth. The simulated effects of ferrite film loading on antenna performance are investigated, with comparisons made for 5 and 10 microm thick films, as well as for 10 microm thick films with varying magnetic loss (tan delta micro = 0.05, 0.1 and 0.3). Our simulations reveal that the addition of 10 microm thick magnetic layers has effectively lowered the resonant frequency by 70 MHz, while improving return loss and -10 dB bandwidth by 3 dB and 40 MHz, respectively, over the uncoated antenna. Ferrite film coating also improved realized gain within the ISM band, with largest gain increases at resonance found for films having lower magnetic loss. Additionally, the gain (G) variance at ISM band limits, Delta Gf(2.5GHz)-f (2.4GHz), decreased from 1.97 to 0.44 dBi for the antenna with 10 microm films over the non-ferrite antenna. The measured dip-coated NiCo ferrite films effectively reduces the antenna resonance by 110 MHz, with a 4.2 dB reflection coefficient improvement as compared to an antenna without ferrite. The measured ferrite antenna also reveals a 6 dBi and 35 MHz improvement in realized gain and -10 dB bandwidth, respectively, at resonance. Additionally, the ferrite-coated antenna shows improved directivity, with wave propagation attenuated at the direction facing the body internal. These results indicate that implantable antenna miniaturization and reliable wireless communication in the operating frequency band can be realized with ferrite loading.

LSST (Hoop/Column) Maypole Antenna Development Program, phase 1, part 1

NASA Technical Reports Server (NTRS)

Sullivan, M. R.

1982-01-01

The first of a two-phase program was performed to develop the technology necessary to evaluate, design, manufacture, package, transport and deploy the hoop/column deployable antenna reflector by means of a ground based program. The hoop/column concept consists of a cable stiffened large diameter hoop and central column structure that supports and contours a radio frequency reflective mesh surface. Mission scenarios for communications, radiometer and radio astronomy, were studied. The data to establish technology drivers that resulted in a specification of a point design was provided. The point design is a multiple beam quadaperture offset antenna system wich provides four separate offset areas of illumination on a 100 meter diameter symmetrical parent reflector. The periphery of the reflector is a hoop having 48 segments that articulate into a small stowed volume around a center extendable column. The hoop and column are structurally connected by graphite and quartz cables. The prominence of cables in the design resulted in the development of advanced cable technology. Design verification models were built of the hoop, column, and surface stowage subassemblies. Model designs were generated for a half scale sector of the surface and a 1/6 scale of the complete deployable reflector.

Expected antenna utilization and overload

NASA Technical Reports Server (NTRS)

Posner, Edward C.

1991-01-01

The trade-offs between the number of antennas at Deep Space Network (DSN) Deep-Space Communications Complex and the fraction of continuous coverage provided to a set of hypothetical spacecraft, assuming random placement of the space craft passes during the day. The trade-offs are fairly robust with respect to the randomness assumption. A sample result is that a three-antenna complex provides an average of 82.6 percent utilization of facilities and coverage of nine spacecraft that each have 8-hour passes, whereas perfect phasing of the passes would yield 100 percent utilization and coverage. One key point is that sometimes fewer than three spacecraft are visible, so an antenna is idle, while at other times, there aren't enough antennas, and some spacecraft do without service. This point of view may be useful in helping to size the network or to develop a normalization for a figure of merit of DSN coverage.

Impulse Testing of Corporate-Fed Patch Array Antennas

NASA Technical Reports Server (NTRS)

Chamberlain, Neil F.

2011-01-01

This paper discusses a novel method for detecting faults in antenna arrays. The method, termed Impulse Testing, was developed for corporate-fed patch arrays where the element is fed by a probe and is shorted at its center. Impulse Testing was devised to supplement conventional microwave measurements in order to quickly verify antenna integrity. The technique relies on exciting each antenna element in turn with a fast pulse (or impulse) that propagates through the feed network to the output port of the antenna. The resulting impulse response is characteristic of the path through the feed network. Using an oscilloscope, a simple amplitude measurement can be made to detect faults. A circuit model of the antenna elements and feed network was constructed to assess various fault scenarios and determine fault-detection thresholds. The experimental setup and impulse measurements for two patch array antennas are presented. Advantages and limitations of the technique are discussed along with applications to other antenna array topologies

MSU Antenna Pattern Data

NASA Technical Reports Server (NTRS)

Mo, Tsan; Kleespies, Thomas J.; Green, J. Philip

2000-01-01

The Microwave Sounding Unit (MSU) antenna pattern data for nine MSU Flight Models (FMs) have been successfully rescued from 22-year old 7-track and 9-track magnetic tapes and cartridges. These antenna pattern data were unpacked into user-friendly ASCII format, and are potentially useful for making antenna pattern corrections to MSU antenna temperatures in retrieving the true brightness temperatures. We also properly interpreted the contents of the data and show how to convert the measured antenna signal amplitude in volts into relative antenna power in dB with proper normalization. It is found that the data are of high quality with a 60-dB drop in the co-polarized antenna patterns from the central peak value to its side-lobe regions at scan angles beyond 30 deg. The unpacked antenna pattern data produced in this study provide a useful database for data users to correct the antenna side-lobe contribution to MSU measurements. All of the data are available to the scientific community on a single CD-ROM.

Advanced Antenna Design for NASA's EcoSAR Instrument

NASA Technical Reports Server (NTRS)

Du Toit, Cornelis F.; Deshpande, Manohar; Rincon, Rafael F.

2016-01-01

Advanced antenna arrays were designed for NASA's EcoSAR airborne radar instrument. EcoSAR is a beamforming synthetic aperture radar instrument designed to make polarimetric and "single pass" interferometric measurements of Earth surface parameters. EcoSAR's operational requirements of a 435MHz center frequency with up to 200MHz bandwidth, dual polarization, high cross-polarization isolation (> 30 dB), +/- 45deg beam scan range and antenna form-factor constraints imposed stringent requirements on the antenna design. The EcoSAR project successfully developed, characterized, and tested two array antennas in an anechoic chamber. EcoSAR's first airborne campaign conducted in the spring of 2014 generated rich data sets of scientific and engineering value, demonstrating the successful operation of the antennas.

Qualification of UHF Antenna for Extreme Martian Thermal Environments

NASA Technical Reports Server (NTRS)

Ramesham, Rajeshuni; Amaro, Luis R.; Brown, Paula R.; Usiskin, Robert

2013-01-01

The purpose of this development was to validate the use of the external Rover Ultra High Frequency (RUHF) antenna for space under extreme thermal environments to be encountered during the surface operations of the Mars Science Laboratory (MSL) mission. The antenna must survive all ground operations plus the nominal 670 Martian sol mission that includes summer and winter seasons of the Mars thermal environment.The qualification effort was to verify that the RUHF antenna design and its bonding and packaging processes are adequate to survive the harsh environmental conditions. The RUHF is a quadrifilar helix antenna mounted on the MSL Curiosity rover deck. The main components of the RUHF antenna are the helix structure, feed cables, and hybrid coupler, and the high-power termination load. In the case of MSL rover externally mounted hardware, not only are the expected thermal cycle depths severe, but there are temperature offsets between the Mars summer and winter seasons. The total number of temperature cycles needed to be split into two regimes of summer cycles and winter cycles. The qualification test was designed to demonstrate a survival life of three times more than all expected ground testing, plus a nominal 670 Martian sol missions. Baseline RF tests and a visual inspection were performed prior to the start of the qualification test. Functional RF tests were performed intermittently during chamber breaks over the course of the qualification test. For the RF return loss measurements, the antenna was tested in a controlled environment outside the thermal chamber with a vector network analyzer that was calibrated over the antenna s operational frequency range. A total of 2,010 thermal cycles were performed. Visual inspection showed a dulling of the solder material. This change will not affect the performance of the antenna. No other changes were observed. RF tests were performed on the RUHF helix antenna, hybrid, and load after the 2,010 qualification cycles test

Development of horn antenna mixer array with internal local oscillator module for microwave imaging diagnostics

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

Kuwahara, D., E-mail: dkuwahar@cc.tuat.ac.jp; Ito, N.; Nagayama, Y.

A new antenna array is proposed in order to improve the sensitivity and complexity of microwave imaging diagnostics systems such as a microwave imaging reflectometry, a microwave imaging interferometer, and an electron cyclotron emission imaging. The antenna array consists of five elements: a horn antenna, a waveguide-to-microstrip line transition, a mixer, a local oscillation (LO) module, and an intermediate frequency amplifier. By using an LO module, the LO optics can be removed, and the supplied LO power to each element can be equalized. We report details of the antenna array and characteristics of a prototype antenna array.

Development of horn antenna mixer array with internal local oscillator module for microwave imaging diagnostics.

PubMed

Kuwahara, D; Ito, N; Nagayama, Y; Yoshinaga, T; Yamaguchi, S; Yoshikawa, M; Kohagura, J; Sugito, S; Kogi, Y; Mase, A

2014-11-01

A new antenna array is proposed in order to improve the sensitivity and complexity of microwave imaging diagnostics systems such as a microwave imaging reflectometry, a microwave imaging interferometer, and an electron cyclotron emission imaging. The antenna array consists of five elements: a horn antenna, a waveguide-to-microstrip line transition, a mixer, a local oscillation (LO) module, and an intermediate frequency amplifier. By using an LO module, the LO optics can be removed, and the supplied LO power to each element can be equalized. We report details of the antenna array and characteristics of a prototype antenna array.

Deployable antenna

NASA Technical Reports Server (NTRS)

Fink, Patrick W. (Inventor); Dobbins, Justin A. (Inventor); Lin, Greg Y. (Inventor); Chu, Andrew W. (Inventor); Scully, Robert C. (Inventor)

2006-01-01

A deployable antenna and method for using wherein the deployable antenna comprises a collapsible membrane having at least one radiating element for transmitting electromagnetic waves, receiving electromagnetic waves, or both.

Implementation for wideband applications using UWB fractal patch antenna

NASA Astrophysics Data System (ADS)

Kumar, D. Naresh

2018-04-01

This paper defines in detail about the diverse fractal patch antenna. Microstrip patch antennas has evolved in the field of research and development extending its impact across wide range of applications. A combination of patch antenna with fractal patterns has become a tryout to outspread it further. Because of its low profile nature patch antennas have added to a lot of prominence. Apart from have this property it can also be renovated further for wide bandwidth (2929 MHz) applications, as it exhibits self-analogous property. This antenna is premeditated on a patch using Sierpinski(4.040 GHz, 6.566 GHz) and Koch fractal geometries respectively. The antenna is designed using HFSS software.

Multibeam Antenna Design and Development for NASA Advanced Communications Technology Satellite (ACTS)

NASA Technical Reports Server (NTRS)

Choung, Youn H.; Wong, William C.

1986-01-01

The design of the ACTS multibeam antenna is described, and its performance is evaluated. The multibeam antenna is designed to cover the continential U.S. and provides three fixed spot beams for high burst rate operations and two scanning beams for low burst rate operations. The antenna has one main reflector, a dual polarized subreflector, and two orthogonal feed assemblies. The feed system is to receive a linearly polarized communication signal from 28.9-30.0 GHz and to provide the elevation and azimuth error tracking signals at 29.975 GHz with a 0.01 deg tracking accuracy. The feed system uses a single multiflare conical horn and a multimode coupler to provide a symmetric primary pattern for the communication signal. The sidelobe characteristics of the reflector, and the relation between the sidelobe level and surface distortion are studied. It is noted that the performance measurements for the multibeam antenna correlate well with predictions for secondary patterns and scan characteristics.

Microwave monolithic integrated circuit development for future spaceborne phased array antennas

NASA Technical Reports Server (NTRS)

Anzic, G.; Kascak, T. J.; Downey, A. N.; Liu, D. C.; Connolly, D. J.

1983-01-01

The development of fully monolithic gallium arsenide (GaAs) receive and transmit modules suitable for phased array antenna applications in the 30/20 gigahertz bands is presented. Specifications and various design approaches to achieve the design goals are described. Initial design and performance of submodules and associated active and passive components are presented. A tradeoff study summary is presented highlighting the advantages of distributed amplifier approach compared to the conventional single power source designs.

Microwave monolithic integrated circuit development for future spaceborne phased array antennas

NASA Astrophysics Data System (ADS)

Anzic, G.; Kascak, T. J.; Downey, A. N.; Liu, D. C.; Connolly, D. J.

1983-12-01

The development of fully monolithic gallium arsenide (GaAs) receive and transmit modules suitable for phased array antenna applications in the 30/20 gigahertz bands is presented. Specifications and various design approaches to achieve the design goals are described. Initial design and performance of submodules and associated active and passive components are presented. A tradeoff study summary is presented highlighting the advantages of distributed amplifier approach compared to the conventional single power source designs.

Development of components for an S-band phased array antenna subsystem

NASA Technical Reports Server (NTRS)

1975-01-01

The system requirements, module test data, and S-band phased array subsystem test data are discussed. Of the two approaches to achieving antenna gain (mechanically steered reflector or electronically steered phased array), the phased array approach offers the greatest simplicity and lowest cost (size, weight, power, and dollars) for this medium gain. A competitive system design is described as well as hardware evaluation which will lead to timely availability of this technology for implementing such a system. The objectives of the study were: to fabricate and test six engineering model transmit/receive microelectronics modules; to design, fabricate, and test one dc and logic multilayer manifold; and to integrate and test an S-band phased array antenna subsystem composed of antenna elements, seven T/R modules, RF manifolds and dc manifold.

Measurement of LHCD antenna position in Aditya tokamak

NASA Astrophysics Data System (ADS)

Ambulkar, K. K.; Sharma, P. K.; Virani, C. G.; Parmar, P. R.; Thakur, A. L.; Kulkarni, S. V.

2010-02-01

To drive plasma current non-inductively in ADITYA tokamak, 120 kW pulsed Lower Hybrid Current Drive (LHCD) system at 3.7 GHz has been designed, fabricated and installed on ADITYA tokamak. In this system, the antenna consists of a grill structure, having two rows, each row comprising of four sub-waveguides. The coupling of LHCD power to the plasma strongly depends on the plasma density near the mouth of grill antenna. Thus the grill antenna has to be precisely positioned for efficient coupling. The movement of mechanical bellow, which contracts or expands up to 50mm, governs the movement of antenna. In order to monitor the position of the antenna precisely, the reference position of the antenna with respect to the machine/plasma position has to be accurately determined. Further a mechanical system or an electronic system to measure the relative movement of the antenna with respect to the reference position is also desired. Also due to poor accessibility inside the ADITYA machine, it is impossible to measure physically the reference position of the grill antenna with respect to machine wall, taken as reference position and hence an alternative method has to be adopted to establish these measurements reliably. In this paper we report the design and development of a mechanism, using which the antenna position measurements are made. It also describes a unique method employing which the measurements of the reference position of the antenna with respect to the inner edge of the tokamak wall is carried out, which otherwise was impossible due to poor accessibility and physical constraints. The position of the antenna is monitored using an electronic scale, which is developed and installed on the bellow. Once the reference position is derived, the linear potentiometer, attached to the bellow, measures the linear distance using position transmitter. The accuracy of measurement obtained in our setup is within +/- 0.5 % and the linearity, along with repeatability is excellent.

FDTD simulation tools for UWB antenna analysis.

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

Brocato, Robert Wesley

2004-12-01

This paper describes the development of a set of software tools useful for analyzing ultra-wideband (UWB) antennas and structures. These tools are used to perform finite difference time domain (FDTD) simulation of a conical antenna with continuous wave (CW) and UWB pulsed excitations. The antenna is analyzed using spherical coordinate-based FDTD equations that are derived from first principles. The simulation results for CW excitation are compared to simulation and measured results from published sources; the results for UWB excitation are new.

A Novel Approach for a Low-Cost Deployable Antenna

NASA Technical Reports Server (NTRS)

Amend, Chris; Nurnberger, Michael; Oppenheimer, Paul; Koss, Steve; Purdy, Bill

2010-01-01

The Naval Research Laboratory (NRL) has designed, built, and fully qualified a low cost, low Passive Intermodulation (PIM) 12-foot (3.66-m) diameter deployable ultra high frequency (UHF) antenna for the Tacsat-4 program. The design utilized novel approaches in reflector material and capacitive coupling techniques. This paper discusses major design trades, unique design characteristics, and lessons learned from the development of the Tacsat 4 deployable antenna. This antenna development was sponsored by the Office of Naval Research.

Theoretical analysis, design and development of a 27-MHz folded loop antenna as a potential applicator in hyperthermia treatment.

PubMed

Kouloulias, Vassilis; Karanasiou, Irene; Giamalaki, Melina; Matsopoulos, George; Kouvaris, John; Kelekis, Nikolaos; Uzunoglu, Nikolaos

2015-02-01

A hyperthermia system using a folded loop antenna applicator at 27 MHz for soft tissue treatment was investigated both theoretically and experimentally to evaluate its clinical value. The electromagnetic analysis of a 27-MHz folded loop antenna for use in human tissue was based on a customised software tool and led to the design and development of the proposed hyperthermia system. The system was experimentally validated using specific absorption rate (SAR) distribution estimations through temperature distribution measurements of a muscle tissue phantom after electromagnetic exposure. Various scenarios for optimal antenna positioning were also performed. Comparison of the theoretical and experimental analysis results shows satisfactory agreement. The SAR level of 50% reaches 8 cm depth in the tissue phantom. Thus, based on the maximum observed SAR values that were of the order of 100 W/kg, the antenna specified is suitable for deep tumour heating. Theoretical and experimental SAR distribution results as derived from this study are in agreement. The proposed folded loop antenna seems appropriate for use in hyperthermia treatment, achieving proper planning and local treatment of deeply seated affected areas and lesions.

Automated Antenna Design with Evolutionary Algorithms

NASA Technical Reports Server (NTRS)

Hornby, Gregory S.; Globus, Al; Linden, Derek S.; Lohn, Jason D.

2006-01-01

algorithm and stochastic hill-climbing has been fabricated and tested. Laboratory results correspond well with simulation. Aerospace component design is an expensive and important step in space development. Evolutionary design can make a significant contribution wherever sufficiently fast, accurate and capable software simulators are available. We have demonstrated successful real-world design in the spacecraft antenna domain; and there is good reason to believe that these results could be replicated in other design spaces.

OPTICAL SPECTRA OF CANDIDATE INTERNATIONAL CELESTIAL REFERENCE FRAME (ICRF) FLAT-SPECTRUM RADIO SOURCES

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

Titov, O.; Stanford, Laura M.; Johnston, Helen M.

2013-07-01

Continuing our program of spectroscopic observations of International Celestial Reference Frame (ICRF) sources, we present redshifts for 120 quasars and radio galaxies. Data were obtained with five telescopes: the 3.58 m European Southern Observatory New Technology Telescope, the two 8.2 m Gemini telescopes, the 2.5 m Nordic Optical Telescope (NOT), and the 6.0 m Big Azimuthal Telescope of the Special Astrophysical Observatory in Russia. The targets were selected from the International VLBI Service for Geodesy and Astrometry candidate International Celestial Reference Catalog which forms part of an observational very long baseline interferometry (VLBI) program to strengthen the celestial reference frame.more » We obtained spectra of the potential optical counterparts of more than 150 compact flat-spectrum radio sources, and measured redshifts of 120 emission-line objects, together with 19 BL Lac objects. These identifications add significantly to the precise radio-optical frame tie to be undertaken by Gaia, due to be launched in 2013, and to the existing data available for analyzing source proper motions over the celestial sphere. We show that the distribution of redshifts for ICRF sources is consistent with the much larger sample drawn from Faint Images of the Radio Sky at Twenty cm (FIRST) and Sloan Digital Sky Survey, implying that the ultra-compact VLBI sources are not distinguished from the overall radio-loud quasar population. In addition, we obtained NOT spectra for five radio sources from the FIRST and NRAO VLA Sky Survey catalogs, selected on the basis of their red colors, which yielded three quasars with z > 4.« less

Microstrip Yagi array for MSAT vehicle antenna application

NASA Technical Reports Server (NTRS)

Huang, John; Densmore, Arthur; Pozar, David

1990-01-01

A microstrip Yagi array was developed for the MSAT system as a low-cost mechanically steered medium-gain vehicle antenna. Because its parasitic reflector and director patches are not connected to any of the RF power distributing circuit, while still contributing to achieve the MSAT required directional beam, the antenna becomes a very efficient radiating system. With the complete monopulse beamforming circuit etched on a thin stripline board, the planar microstrip Yagi array is capable of achieving a very low profile. A theoretical model using the Method of Moments was developed to facilitate the ease of design and understanding of this antenna.

GPS antenna designs

NASA Technical Reports Server (NTRS)

Laube, Samuel J. P.

1987-01-01

Application of the current GPS NAVSTAR system to civilian service requires that a right hand, circularly polarized, -160 dBW spread spectrum signal be received from an orbiting satellite, where the antenna environment is also moving. This presents a design challenge when inexpensive antennas are desired. The intent of this survey is to provide information on the antennas mentioned and to construct and test prototypes to determine whether the choice made by the industry, the quadrifilar helix, is the best. The helix antenna is currently the low cost standard for GPS. Prototype versions were constructed using 12 gauge wire and subminiature coaxial hardline. The constructed antennas were tested using a signal generator and a reference turnstile. A spectrum analyzer was used to measure the level of the received signal.

A Review of Antenna Technologies for Future NASA Exploration Missions

NASA Technical Reports Server (NTRS)

Miranda, Felix A.; Nessel, James A.; Romanofsky, Robert R.; Acostia, Roberto J.

2006-01-01

NASA s plans for the manned exploration of the Moon and Mars will rely heavily on the development of a reliable communications infrastructure from planetary surface-to-surface, surface-to-orbit and back to Earth. Future missions will thus focus not only on gathering scientific data, but also on the formation of the communications network. In either case, unique requirements become imposed on the antenna technologies necessary to accomplish these tasks. For example, proximity (i.e., short distance) surface activity applications such as robotic rovers, human extravehicular activities (EVA), and probes will require small size, lightweight, low power, multi-functionality, and robustness for the antenna elements being considered. In contrast, trunk-line communications to a centralized habitat on the surface and back to Earth (e.g., relays, satellites, and landers) will necessitate high gain, low mass antennas such as novel inflatable/deployable antennas. Likewise, the plethora of low to high data rate services desired to guarantee the safety and quality of mission data for robotic and human exploration will place additional demands on the technology. Over the last few years, NASA Glenn Research Center has been heavily involved in the development and evaluation of candidate antenna technologies with the potential for meeting the aforementioned requirements. These technologies range from electrically small antennas to phased arrays and large inflatable antenna structures. A summary of these efforts will be discussed in this paper. NASA planned activities under the Exploration Vision as they pertain to the communications architecture for the Lunar and Martian scenarios will be discussed, with emphasis on the desirable qualities of potential antenna element designs for envisioned communications assets. Identified frequency allocations for the Lunar and Martian surfaces, as well as asset-specific data services will be described to develop a foundation for viable antenna

A Review of Antenna Technologies for Future NASA Exploration Missions

NASA Technical Reports Server (NTRS)

Miranda, Felix A.; Nessel, James A.; Romanofsky, Robert R.; Acosta, J.

2007-01-01

NASA's plans for the manned exploration of the Moon and Mars will rely heavily on the development of a reliable communications infrastructure from planetary surface-to-surface, surface-to-orbit and back to Earth. Future missions will thus focus not only on gathering scientific data, but also on the formation of the communications network. In either case, unique requirements become imposed on the antenna technologies necessary to accomplish these tasks. For example, proximity (i.e., short distance) surface activity applications such as robotic rovers, human extravehicular activities (EVA), and probes will require small size, lightweight, low power, multi-functionality, and robustness for the antenna elements being considered. In contrast, trunk-line communications to a centralized habitat on the surface and back to Earth (e.g., relays, satellites, and landers) will necessitate high gain, low mass antennas such as novel inflatable/deployable antennas. Likewise, the plethora of low to high data rate services desired to guarantee the safety and quality of mission data for robotic and human exploration will place additional demands on the technology. Over the last few years, NASA Glenn Research Center has been heavily involved in the development and evaluation of candidate antenna technologies with the potential for meeting the aforementioned requirements. These technologies range from electrically small antennas to phased arrays and large inflatable antenna structures. A summary of these efforts will be discussed in this paper. NASA planned activities under the Exploration Vision as they pertain to the communications architecture for the Lunar and Martian scenarios will be discussed, with emphasis on the desirable qualities of potential antenna element designs for envisioned communications assets. Identified frequency allocations for the Lunar and Martian surfaces, as well as asset-specific data services will be described to develop a foundation for viable antenna

Reconfigurable Antennas for High Data Rate Multi-beam Communication Systems

NASA Technical Reports Server (NTRS)

Bernhard, Jennifer T.; Michielssen, Eric

2005-01-01

High-speed (2-100 Mb/sec) wireless data communication - whether land- or satellite-based - faces a major challenge: high error rates caused by interference and unpredictable environments. A planar antenna system that can be reconfigured to respond to changing conditions has the potential to dramatically improve data throughput and system reliability. Moreover, new planar antenna designs that reduce array size, weight, and cost can have a significant impact on terrestrial and satellite communication system performance. This research developed new individually-reconfigurable planar antenna array elements that can be adjusted to provide multiple beams while providing increased scan angles and higher aperture efficiency than traditional diffraction-limited arrays. These new elements are microstrip spiral antennas with specialized tuning mechanisms that provide adjustable radiation patterns. We anticipate that these new elements can be used in both large and small arrays for inter-satellite communication as well as tracking of multiple mobile surface-based units. Our work has developed both theoretical descriptions as well as experimental prototypes of the antennas in both single element and array embodiments. The technical summary of the results of this work is divided into six sections: A. Cavity model for analysis and design of pattern reconfigurable antennas; B. Performance of antenna in array configurations for broadside and endfire operation; C. Performance of antenna in array configurations for beam scanning operation; D. Simulation of antennas in infinite phased arrays; E. Demonstration of antenna with commercially-available RF MEMS switches; F. Design of antenna MEMS switch combinations for direct simultaneous fabrication.

Dual Mode Slotted Monopole Antenna

DTIC Science & Technology

2017-01-05

of 15 DUAL MODE SLOTTED MONOPOLE ANTENNA STATEMENT OF GOVERNMENT INTEREST [0001] The invention described herein may be manufactured and used by...to a dual mode antenna having one mode as a slotted cylinder antenna and another mode as a monopole antenna . (2) Description of the Prior Art...0004] Slotted cylinder antennas are popular antennas for use in line of sight communications systems, especially where the carrier frequency exceeds

Smart skin spiral antenna with chiral absorber

NASA Astrophysics Data System (ADS)

Varadan, Vijay K.; Varadan, Vasundara V.

1995-05-01

Recently there has been considerable interest toward designing 'smart skins' for aircraft. The smart skin is a composite layer which may contain conformal radars, conformal microstrip antennas or spiral antennas for electromagnetic applications. These embedded antennas will give rise to very low radar cross section (RCS) or can be completely 'hidden' to tracking radar. In addition, they can be used to detect, monitor or even jam other unwanted electromagnetic field signatures. This paper is designed to address some technical advances made to reduce the size of spiral antennas using tunable dielectric materials and chiral absorbers. The purpose is to design, develop and fabricate a thin, wideband, conformal spiral antenna architecture that is structurally integrable and which uses advanced Penn State dielectric and absorber materials to achieve wideband ground planes, and together with low RCS. Traditional practice has been to design radome and antenna as separate entities and then resolve any interface problems during an integration phase. A structurally integrable conformal antenna, however, demands that the functional components be highly integrated both conceptually and in practice. Our concept is to use the lower skin of the radome as a substrate on which the radiator can be made using standard photolithography, thick film or LTCC techniques.

Design of Miniaturized Dual-Band Microstrip Antenna for WLAN Application

PubMed Central

Yang, Jiachen; Wang, Huanling; Lv, Zhihan; Wang, Huihui

2016-01-01

Wireless local area network (WLAN) is a technology that combines computer network with wireless communication technology. The 2.4 GHz and 5 GHz frequency bands in the Industrial Scientific Medical (ISM) band can be used in the WLAN environment. Because of the development of wireless communication technology and the use of the frequency bands without the need for authorization, the application of WLAN is becoming more and more extensive. As the key part of the WLAN system, the antenna must also be adapted to the development of WLAN communication technology. This paper designs two new dual-frequency microstrip antennas with the use of electromagnetic simulation software—High Frequency Structure Simulator (HFSS). The two antennas adopt ordinary FR4 material as a dielectric substrate, with the advantages of low cost and small size. The first antenna adopts microstrip line feeding, and the antenna radiation patch is composed of a folded T-shaped radiating dipole which reduces the antenna size, and two symmetrical rectangular patches located on both sides of the T-shaped radiating patch. The second antenna is a microstrip patch antenna fed by coaxial line, and the size of the antenna is diminished by opening a stepped groove on the two edges of the patch and a folded slot inside the patch. Simulation experiments prove that the two designed antennas have a higher gain and a favourable transmission characteristic in the working frequency range, which is in accordance with the requirements of WLAN communication. PMID:27355954

Design of Miniaturized Dual-Band Microstrip Antenna for WLAN Application.

PubMed

Yang, Jiachen; Wang, Huanling; Lv, Zhihan; Wang, Huihui

2016-06-27

Wireless local area network (WLAN) is a technology that combines computer network with wireless communication technology. The 2.4 GHz and 5 GHz frequency bands in the Industrial Scientific Medical (ISM) band can be used in the WLAN environment. Because of the development of wireless communication technology and the use of the frequency bands without the need for authorization, the application of WLAN is becoming more and more extensive. As the key part of the WLAN system, the antenna must also be adapted to the development of WLAN communication technology. This paper designs two new dual-frequency microstrip antennas with the use of electromagnetic simulation software-High Frequency Structure Simulator (HFSS). The two antennas adopt ordinary FR4 material as a dielectric substrate, with the advantages of low cost and small size. The first antenna adopts microstrip line feeding, and the antenna radiation patch is composed of a folded T-shaped radiating dipole which reduces the antenna size, and two symmetrical rectangular patches located on both sides of the T-shaped radiating patch. The second antenna is a microstrip patch antenna fed by coaxial line, and the size of the antenna is diminished by opening a stepped groove on the two edges of the patch and a folded slot inside the patch. Simulation experiments prove that the two designed antennas have a higher gain and a favourable transmission characteristic in the working frequency range, which is in accordance with the requirements of WLAN communication.

The ESA/MBB unfurlable mesh antenna development for mobile services

NASA Astrophysics Data System (ADS)

Kellermeier, H.; Vorbrugg, H.; Pontoppidan, K.; Eaton, D. C. G.

Mobile services via satellite in the 800-900 MHz frequency range have recently been studied by SPAR Aerospace Ltd in the M-SAT phase B using various unfurlable offset reflector concepts between 9 and 5 m aperture diameters for 6-, 4- and 2-beam coverage. For a 2-beam coverage of Canada and U.S.A. two offset antennas each of 5 m aperture diameter are required. The MBB offset unfurlable mesh antenna (UMA) developed since 1983 under an ESA contract is one of the attractive candidates: The design concept chosen uses foldable radial ribs of carbon fibre which deploy a gold plated molybdenum mesh on adjustable stand-offs. This concept is applicable for offset aperture diameters up to 12 m since the carbon fibre ribs are double folded and provide for a high package density when stowed at the spacecraft during launch. The electrical analysis performed by TICRA/Copenhagen was assisted by electrical measurements on mesh samples, verifying that main charactertics as ohmic resistance, transmission loss and passive intermodulation products (PIMP) lie within the required tolerances if the mesh is pretensioned to a certain configuration. For on-orbit testing and retrieval by the Shuttle the reflector shows a unique design feature of retractability by the reversable deployment sequence.

Microwave holographic metrology for antenna diagnosis

NASA Astrophysics Data System (ADS)

Rahmat-Samii, Y.

1990-11-01

Advances in antenna diagnostic methodologies have been very significant in recent years. In particular, microwave holographic diagnostic techniques have been applied very successfully in improving the performance of reflector and array antennas. These techniques use the knowledge of the measured amplitude and phase of the antenna radiated fields and then take advantage of the existing Fourier transform relationships between the radiated fields and the effective aperture or current distribution to eventually determine the reflector surface or array excitation coefficients anomalies. In this paper an overview of the recent developments in applying microwave holography is presented. The theoretical, numerical and measurement aspects of this technique is detailed by providing representative results.

Study of wrap-rib antenna design

NASA Technical Reports Server (NTRS)

Wade, W. D.; Sinha, A.; Singh, R.

1979-01-01

The results of a parametric design study conducted to develop the significant characteristics and technology limitations of space deployable antenna systems with aperture sizes ranging from 50 up to 300 m and F/D ratios between 0.5 and 3.0 are presented. Wrap/rib type reflectors of both the prime and offset fed geometry and associated feed support structures were considered. The significant constraints investigated as limitations on achievable aperture were inherent manufacturability, orbit dynamic and thermal stability, antenna weight, and antenna stowed volume. A data base, resulting in the defined maximum achievable aperture size as a function of diameter, frequency and estimated cost, was formed.

RF models for plasma-surface interactions

NASA Astrophysics Data System (ADS)

Jenkins, Thomas; Smithe, David; Lin, Ming-Chieh; Kruger, Scott; Stoltz, Peter

2013-09-01

Computational models for DC and oscillatory (RF-driven) sheath potentials, arising at metal or dielectric-coated surfaces in contact with plasma, are developed within the VSim code and applied in parameter regimes characteristic of fusion plasma experiments and plasma processing scenarios. Results from initial studies quantifying the effects of various dielectric wall coating materials and thicknesses on these sheath potentials, as well as on the ensuing flux of plasma particles to the wall, are presented. As well, the developed models are used to model plasma-facing ICRF antenna structures in the ITER device; we present initial assessments of the efficacy of dielectric-coated antenna surfaces in reducing sputtering-induced high-Z impurity contamination of the fusion reaction. Funded by U.S. DoE via a Phase I SBIR grant, award DE-SC0009501.

Investigation of a Light Gas Helicon Plasma Source for the VASIMR Space Propulsion System

NASA Technical Reports Server (NTRS)

Squire, J. P.; Chang-Diaz, F. R.; Jacobson, V. T.; Glover, T. W.; Baity, F. W.; Carter, M. D.; Goulding, R. H.; Bengtson, R. D.; Bering, E. A., III

2003-01-01

An efficient plasma source producing a high-density (approx.10(exp 19/cu m) light gas (e.g. H, D, or He) flowing plasma with a high degree of ionization is a critical component of the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) concept. We are developing an antenna to apply ICRF power near the fundamental ion cyclotron resonance to further accelerate the plasma ions to velocities appropriate for space propulsion applications. The high degree of ionization and a low vacuum background pressure are important to eliminate the problem of radial losses due to charge exchange. We have performed parametric (e.g. gas flow, power (0.5 - 3 kW), magnetic field , frequency (25 and 50 MHz)) studies of a helicon operating with gas (H2 D2, He, N2 and Ar) injected at one end with a high magnetic mirror downstream of the antenna. We have explored operation with a cusp and a mirror field upstream. Plasma flows into a low background vacuum (<10(exp -4) torr) at velocities higher than the ion sound speed. High densities (approx. 10(exp 19/cu m) have been achieved at the location where ICRF will be applied, just downstream of the magnetic mirror.

Cellular Reflectarray Antenna

NASA Technical Reports Server (NTRS)

Romanofsky, Robert R.

2010-01-01

The cellular reflectarray antenna is intended to replace conventional parabolic reflectors that must be physically aligned with a particular satellite in geostationary orbit. These arrays are designed for specified geographical locations, defined by latitude and longitude, each called a "cell." A particular cell occupies nominally 1,500 square miles (3,885 sq. km), but this varies according to latitude and longitude. The cellular reflectarray antenna designed for a particular cell is simply positioned to align with magnetic North, and the antenna surface is level (parallel to the ground). A given cellular reflectarray antenna will not operate in any other cell.

High-temperature superconductor antenna investigations

NASA Technical Reports Server (NTRS)

Karasack, Vincent G.

1990-01-01

The use of superconductors to increase antenna radiation efficiency and gain is examined. Although the gain of all normal-metal antennas can be increased through the use of superconductors, some structures have greater potential for practical improvement than others. Some structures suffer a great degradation in bandwidth when replaced with superconductors, while for others the improvement in efficiency is trivial due to the minimal contribution of the conductor loss mechanism to the total losses, or the already high efficiency of the structure. The following antennas and related structures are discussed: electrically small antennas, impedance matching of antennas, microstrip antennas, microwave and millimeter-wave antenna arrays, and superdirective arrays. The greatest potential practical improvements occur for large microwave and millimeter-wave arrays and the impedance matching of antennas.

Determination of antenna factors using a three-antenna method at open-field test site

NASA Astrophysics Data System (ADS)

Masuzawa, Hiroshi; Tejima, Teruo; Harima, Katsushige; Morikawa, Takao

1992-09-01

Recently NIST has used the three-antenna method for calibration of the antenna factor of an antenna used for EMI measurements. This method does not require the specially designed standard antennas which are necessary in the standard field method or the standard antenna method, and can be used at an open-field test site. This paper theoretically and experimentally examines the measurement errors of this method and evaluates the precision of the antenna-factor calibration. It is found that the main source of the error is the non-ideal propagation characteristics of the test site, which should therefore be measured before the calibration. The precision of the antenna-factor calibration at the test site used in these experiments, is estimated to be 0.5 dB.

Microwave monolithic integrated circuit development for future spaceborne phased array antennas

NASA Technical Reports Server (NTRS)

Anzic, G.; Kascak, T. J.; Downey, A. N.; Liu, D. C.; Connolly, D. J.

1984-01-01

The development of fully monolithic gallium arsenide (GaAs) receive and transmit modules suitable for phased array antenna applications in the 30/20 gigahertz bands is presented. Specifications and various design approaches to achieve the design goals are described. Initial design and performance of submodules and associated active and passive components are presented. A tradeoff study summary is presented, highlighting the advantages of a distributed amplifier approach compared to the conventional single power source designs. Previously announced in STAR as N84-13399

Microwave monolithic integrated circuit development for future spaceborne phased array antennas

NASA Astrophysics Data System (ADS)

Anzic, G.; Kascak, T. J.; Downey, A. N.; Liu, D. C.; Connolly, D. J.

The development of fully monolithic gallium arsenide (GaAs) receive and transmit modules suitable for phased array antenna applications in the 30/20 gigahertz bands is presented. Specifications and various design approaches to achieve the design goals are described. Initial design and performance of submodules and associated active and passive components are presented. A tradeoff study summary is presented, highlighting the advantages of a distributed amplifier approach compared to the conventional single power source designs. Previously announced in STAR as N84-13399

Deployable antenna kinematics using tensegrity structure design

NASA Astrophysics Data System (ADS)

Knight, Byron Franklin

With vast changes in spacecraft development over the last decade, a new, cheaper approach was needed for deployable kinematic systems such as parabolic antenna reflectors. Historically, these mesh-surface reflectors have resembled folded umbrellas, with incremental redesigns utilized to save packaging size. These systems are typically over-constrained designs, the assumption being that high reliability necessary for space operations requires this level of conservatism. But with the rapid commercialization of space, smaller launch platforms and satellite buses have demanded much higher efficiency from all space equipment than can be achieved through this incremental approach. This work applies an approach called tensegrity to deployable antenna development. Kenneth Snelson, a student of R. Buckminster Fuller, invented Tensegrity structures in 1948. Such structures use a minimum number of compression members (struts); stability is maintain using tension members (ties). The novelty introduced in this work is that the ties are elastic, allowing the struts to extend or contract, and in this way changing the surface of the antenna. Previously, the University of Florida developed an approach to quantify the stability and motion of parallel manipulators. This approach was applied to deployable, tensegrity, antenna structures. Based on the kinematic analyses for the 3-3 (octahedron) and 4-4 (square anti-prism) structures, the 6-6 (hexagonal anti-prism) analysis was completed which establishes usable structural parameters. The primary objective for this work was to prove the stability of this class of deployable structures, and their potential application to space structures. The secondary objective is to define special motions for tensegrity antennas, to meet the subsystem design requirements, such as addressing multiple antenna-feed locations. This work combines the historical experiences of the artist (Snelson), the mathematician (Ball), and the space systems engineer

Overview of ASDEX Upgrade results

DOE PAGES

Aguiam, D.

2017-06-28

Here, the ASDEX Upgrade (AUG) programme is directed towards physics input to critical elements of the ITER design and the preparation of ITER operation, as well as addressing physics issues for a future DEMO design. Since 2015, AUG is equipped with a new pair of 3-strap ICRF antennas, which were designed for a reduction of tungsten release during ICRF operation. As predicted, a factor two reduction on the ICRF-induced W plasma content could be achieved by the reduction of the sheath voltage at the antenna limiters via the compensation of the image currents of the central and side straps in the antenna frame. There are two main operational scenario lines in AUG. Experiments with low collisionality, which comprise current drive, ELM mitigation/suppression and fast ion physics, are mainly done with freshly boronized walls to reduce the tungsten influx at these high edge temperature conditions. Full ELM suppression and non-inductive operation up to a plasma current ofmore » $${{I}_{\\text{p}}}=0.8$$ MA could be obtained at low plasma density. Plasma exhaust is studied under conditions of high neutral divertor pressure and separatrix electron density, where a fresh boronization is not required. Substantial progress could be achieved for the understanding of the confinement degradation by strong D puffing and the improvement with nitrogen or carbon seeding. Inward/outward shifts of the electron density profile relative to the temperature profile effect the edge stability via the pressure profile changes and lead to improved/decreased pedestal performance. Seeding and D gas puffing are found to effect the core fueling via changes in a region of high density on the high field side (HFSHD).« less

Mode Matching for Optical Antennas

NASA Astrophysics Data System (ADS)

Feichtner, Thorsten; Christiansen, Silke; Hecht, Bert

2017-11-01

The emission rate of a point dipole can be strongly increased in the presence of a well-designed optical antenna. Yet, optical antenna design is largely based on radio-frequency rules, ignoring, e.g., Ohmic losses and non-negligible field penetration in metals at optical frequencies. Here, we combine reciprocity and Poynting's theorem to derive a set of optical-frequency antenna design rules for benchmarking and optimizing the performance of optical antennas driven by single quantum emitters. Based on these findings a novel plasmonic cavity antenna design is presented exhibiting a considerably improved performance compared to a reference two-wire antenna. Our work will be useful for the design of high-performance optical antennas and nanoresonators for diverse applications ranging from quantum optics to antenna-enhanced single-emitter spectroscopy and sensing.

Antenna cab interior showing equipment rack and fiberglass antenna panels, ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Antenna cab interior showing equipment rack and fiberglass antenna panels, looking west. - Western Union Telegraph Company, Jennerstown Relay, Laurel Summit Road off U.S. 30, Laughlintown, Westmoreland County, PA

Antenna cab interior showing equipment rack and fiberglass antenna panels, ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Antenna cab interior showing equipment rack and fiberglass antenna panels, looking southeast. - Western Union Telegraph Company, Jennerstown Relay, Laurel Summit Road off U.S. 30, Laughlintown, Westmoreland County, PA

Mechanical Technology Development on A 35-m Deployable Radar Antenna for Monitoring Hurricanes

NASA Technical Reports Server (NTRS)

Fang, Houfei; Im, Eastwood

2006-01-01

The NEXRAD in Space project develops a novel instrument concept and the associated antenna technologies for a 35-GHz Doppler radar to monitor hurricanes, cyclones, and severe storms from a geostationary orbit. Mechanical challenges of this concept include a 35-m diameter lightweight in space deployable spherical reflector and a feeder scanning mechanism. The feasibility of using shape memory polymer material to develop the large deployable reflector has been investigated by this study. A spiral scanning mechanism concept has been developed and demonstrated by an engineering model.

Modified Reference SPS with Solid State Transmitting Antenna

NASA Technical Reports Server (NTRS)

Woodcock, G. R.; Sperber, B. R.

1980-01-01

The development of solid state microwave power amplifiers for a solar power satellite transmitting antenna is discussed. State-of-the-art power-added efficiency, gain, and single device power of various microwave solid state devices are compared. The GaAs field effect transistors and the Si-bipolar transistors appear potentially feasible for solar power satellite use. The integration of solid state devices into antenna array elements is examined and issues concerning antenna integration and consequent satellite configurations are examined.

Antenna cab interior showing waveguide from external parabolic antenna (later ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Antenna cab interior showing waveguide from external parabolic antenna (later addition), looking north. - Western Union Telegraph Company, Jennerstown Relay, Laurel Summit Road off U.S. 30, Laughlintown, Westmoreland County, PA

A 32 GHz microstrip array antenna for microspacecraft application

NASA Technical Reports Server (NTRS)

Huang, J.

1994-01-01

JPL/NASA is currently developing microspacecraft systems for future deep space applications. One of the frequency bands being investigated for microspacecraft is the Ka-band (32 GHz), which can be used with smaller equipment and provides a larger bandwidth. This article describes the successful development of a circularly polarized microstrip array with 28 dBic of gain at 32 GHz. This antenna, which is thin, flat, and small, can be surface-mounted onto the microspacecraft and, hence, takes very little volume and mass of the spacecraft. The challenges in developing this antenna are minimizing the microstrip antenna's insertion loss and maintaining a reasonable frequency bandwidth.

Phase Retrieval for Radio Telescope and Antenna Control

NASA Technical Reports Server (NTRS)

Dean, Bruce

2011-01-01

Phase-retrieval is a general term used in optics to describe the estimation of optical imperfections or "aberrations." The purpose of this innovation is to develop the application of phase retrieval to radio telescope and antenna control in the millimeter wave band. Earlier techniques do not approximate the incoherent subtraction process as a coherent propagation. This approximation reduces the noise in the data and allows a straightforward application of conventional phase retrieval techniques for radio telescope and antenna control. The application of iterative-transform phase retrieval to radio telescope and antenna control is made by approximating the incoherent subtraction process as a coherent propagation. Thus, for systems utilizing both positive and negative polarity feeds, this approximation allows both surface and alignment errors to be assessed without the use of additional hardware or laser metrology. Knowledge of the antenna surface profile allows errors to be corrected at a given surface temperature and observing angle. In addition to imperfections of the antenna surface figure, the misalignment of multiple antennas operating in unison can reduce or degrade the signal-to-noise ratio of the received or broadcast signals. This technique also has application to the alignment of antenna array configurations.

Study of array plasma antenna parameters

NASA Astrophysics Data System (ADS)

Kumar, Rajneesh; Kumar, Prince

2018-04-01

This paper is aimed to investigate the array plasma antenna parameters to help the optimization of an array plasma antenna. Single plasma antenna is transformed into array plasma antenna by changing the operating parameters. The re-configurability arises in the form of striations, due to transverse bifurcation of plasma column by changing the operating parameters. Each striation can be treated as an antenna element and system performs like an array plasma antenna. In order to achieve the goal of this paper, three different configurations of array plasma antenna (namely Array 1, Array 2 and Array 3) are simulated. The observations are made on variation in antenna parameters like resonance frequency, radiation pattern, directivity and gain with variation in length and number of antenna elements for each array plasma antenna. Moreover experiments are also performed and results are compared with simulation. Further array plasma antenna parameters are also compared with monopole plasma antenna parameters. The study of present paper invoke the array plasma antenna can be applied for steering and controlling the strength of Wi-Fi signals as per requirement.

A True Metasurface Antenna.

PubMed

El Badawe, Mohamed; Almoneef, Thamer S; Ramahi, Omar M

2016-01-13

We present a true metasurface antenna based on electrically-small resonators. The resonators are placed on a flat surface and connected to one feed point using corporate feed. Unlike conventional array antennas where the distance between adjacent antennas is half wavelength to reduce mutual coupling between adjacent antennas, here the distance between the radiating elements is electrically very small to affect good impedance matching of each resonator to its feed. A metasurface antenna measuring 1.2λ × 1.2λ and designed to operate at 3 GHz achieved a gain of 12 dBi. A prototype was fabricated and tested showing good agreement between numerical simulations and experimental results. Through numerical simulation, we show that the metasurface antenna has the ability to provide beam steering by phasing all the resonators appropriately.

An antenna pointing mechanism for large reflector antennas

NASA Technical Reports Server (NTRS)

Heimerdinger, H.

1981-01-01

An antenna pointing mechanism for large reflector antennas on direct broadcasting communication satellites was built and tested. After listing the requirements and constraints for this equipment the model is described, and performance figures are given. Futhermore, results of the qualification level tests, including functional, vibrational, thermovacuum, and accelerated life tests are reported. These tests were completed successfully.

Unidirectional Magneto-Electric Dipole Antenna for Base Station: A Review

NASA Astrophysics Data System (ADS)

Idayachandran, Govindanarayanan; Nakkeeran, Rangaswamy

2018-04-01

Unidirectional base station antenna design using Magneto-Electric Dipole (MED) has created enormous interest among the researchers due to its excellent radiation characteristics like low back radiation, symmetrical radiation at E-plane and H-plane compared to conventional patch antenna. Generally, dual polarized antennas are used to increase channel capacity and reliability of the communication systems. In order to serve the evolving mobile communication standards like long term evolution LTE and beyond, unidirectional dual polarized MED antenna are required to have broad impedance bandwidth, broad half power beamwidth, high port isolation, low cross polarization level, high front to back ratio and high gain. In this paper, the critical electrical requirements of the base station antenna and frequently used frequency bands for modern mobile communication have been presented. It is followed by brief review on broadband patch antenna and discussion on complementary antenna concepts. Finally, the performance of linearly polarized and dual polarized magneto-electric dipole antennas along with their feeding techniques are discussed and summarized. Also, design and modeling of developed MED antenna is presented.

Large-Aperture Membrane Active Phased-Array Antennas

NASA Technical Reports Server (NTRS)

Karasik, Boris; McGrath, William; Leduc, Henry

2009-01-01

Large-aperture phased-array microwave antennas supported by membranes are being developed for use in spaceborne interferometric synthetic aperture radar systems. There may also be terrestrial uses for such antennas supported on stationary membranes, large balloons, and blimps. These antennas are expected to have areal mass densities of about 2 kg/sq m, satisfying a need for lightweight alternatives to conventional rigid phased-array antennas, which have typical areal mass densities between 8 and 15 kg/sq m. The differences in areal mass densities translate to substantial differences in total mass in contemplated applications involving aperture areas as large as 400 sq m. A membrane phased-array antenna includes patch antenna elements in a repeating pattern. All previously reported membrane antennas were passive antennas; this is the first active membrane antenna that includes transmitting/receiving (T/R) electronic circuits as integral parts. Other integral parts of the antenna include a network of radio-frequency (RF) feed lines (more specifically, a corporate feed network) and of bias and control lines, all in the form of flexible copper strip conductors on flexible polymeric membranes. Each unit cell of a prototype antenna (see Figure 1) contains a patch antenna element and a compact T/R module that is compatible with flexible membrane circuitry. There are two membrane layers separated by a 12.7-mm air gap. Each membrane layer is made from a commercially available flexible circuit material that, as supplied, comprises a 127-micron-thick polyimide dielectric layer clad on both sides with 17.5-micron-thick copper layers. The copper layers are patterned into RF, bias, and control conductors. The T/R module is located on the back side of the ground plane and is RF-coupled to the patch element via a slot. The T/R module is a hybrid multilayer module assembled and packaged independently and attached to the membrane array. At the time of reporting the information for

Astigmatism in reflector antennas.

NASA Technical Reports Server (NTRS)

Cogdell, J. R.; Davis, J. H.

1973-01-01

Astigmatic phase error in large parabolic reflector antennas is discussed. A procedure for focusing an antenna and diagnosing the presence and degree of astigmatism is described. Theoretical analysis is conducted to determine the nature of this error in such antennas.

Ultra-broadband near-field antenna for terahertz plasmonic applications

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

Polischuk, O. V., E-mail: polischuk.sfire@mail.ru; Popov, V. V., E-mail: popov-slava@yahoo.co.uk; Knap, W.

A new type of ultra-broadband near-field antenna for terahertz frequencies is proposed. This antenna is a short-period planar metal array. It is theoretically shown that irradiation of the short-period array antenna by a plane homogeneous terahertz waves excite a highly inhomogeneous near electric field near the metal array. In this case, the amplitude of the excited inhomogeneous near electric field is almost independent of frequency in the entire terahertz frequency range. The excitation of plasma oscillations in a two-dimensional electron system using the antenna under study is numerically simulated in the resonant and non-resonant plasmonic response modes. This type ofmore » antenna can be used for developing ultra-broadband plasmonic detectors of terahertz radiation.« less

Structure and postembryonic development of the intersegmental nodules in the non-muscular joints of the antennae in Rhodnius prolixus.

PubMed

Ospina-Rozo, Bibiana; Forero-Shelton, Manu; Molina, Jorge

2017-03-01

The antennae of Insecta consist of two basal segments and the distal annulated flagellum lacking intrinsic muscles. Non-muscular joints are important to preserve the flexibility and structure of the long heteropteran antennae which bear an intersegmental nodule on each non-muscular joint. Little is known about their properties or function. Here we characterize the structure and postembryonic development of the non-muscular joints of Rhodnius prolixus antennae. Using Scanning Electron Microscopy, we tracked the changes in shape and size of both intersegmental nodules during the course of the hemimetabolous insect life cycle. Using Atomic Force Microscopy, we established a qualitative correlation between the topography of the surface and the rigidity of the joint between pedicel and flagellum. Our results confirmed the presence of two sub-articulations on each non-muscular joint. Also, the two intersegmental nodules have different origins: the one between the two flagellar segments (intraflagelloid) is a sclerite already present from the early nymph, while the nodule between pedicel and flagellum (prebasiflagellite) originates by gradual separation of the proximal end of the basiflagellum during postembryonic development. Various changes occur in the non-muscular joints and segments of the antenna during the life cycle of R. prolixus. Copyright © 2016 Elsevier Ltd. All rights reserved.

History of Antenna Technology for Mobile Communications in Korea

NASA Astrophysics Data System (ADS)

Min, Kyeong-Sik; Park, Chul-Keun; Kang, Suk-Youb

In this paper, we discuss the development of wireless and mobile communications in Korea, current technological trends, and the future outlook on technological developments. Since the introduction of the telegraph and the telephone in September 1885, Korea's wired and wireless communications industry has consistently developed for over 100 years. Since 1984, upon the provision of the mobile telecommunications service, the industry has seen drastic qualitative and quantitative growth in terms of both technical and economic aspects, which played a crucial role in the rapid growth of the digital industry in Korea. After the era of the analog cellular service based on the Advanced Mobile Phone System (AMPS), a precursor to the modern mobile service, Korea became the world's first country to commercialize Code Division Multiple Access (CDMA) in 1996 and succeeded in commercializing CDMA 2000 lx (IMT 2000) in 2001. With further developments in the mobile communication technology, the technology for antennas also saw drastic advancements. As the mobile antennas moved from the second to the third generation, they grew from external models to very small internal models. At the same time, they evolved into highly functional and high performance multiple band and wide band antennas. Furthermore, Korea was the first country to commercialize and offer the Wireless Broadband Internet (WiBro) service in 2006. By leading the wireless communications standardization and exerting remarkable efforts in research and development, Korea is consolidating its status as an Information Technology (IT) leader in the global market. The antenna's inherent importance will be further emphasized in the near future as it satisfies the performance and structural needs of portable terminals necessary for realizing the projected establishment of the ubiquitous world. It is thought that antenna technologies will not be limited to simple concepts as previously experienced but will utilize various kinds

All-dielectric rod antenna array for terahertz communications

NASA Astrophysics Data System (ADS)

Withayachumnankul, Withawat; Yamada, Ryoumei; Fujita, Masayuki; Nagatsuma, Tadao

2018-05-01

The terahertz band holds a potential for point-to-point short-range wireless communications at sub-terabit speed. To realize this potential, supporting antennas must have a wide bandwidth to sustain high data rate and must have high gain and low dissipation to compensate for the free space path loss that scales quadratically with frequency. Here we propose an all-dielectric rod antenna array with high radiation efficiency, high gain, and wide bandwidth. The proposed array is integral to a low-loss photonic crystal waveguide platform, and intrinsic silicon is the only constituent material for both the antenna and the feed to maintain the simplicity, compactness, and efficiency. Effective medium theory plays a key role in the antenna performance and integrability. An experimental validation with continuous-wave terahertz electronic systems confirms the minimum gain of 20 dBi across 315-390 GHz. A demonstration shows that a pair of such identical rod array antennas can handle bit-error-free transmission at the speed up to 10 Gbit/s. Further development of this antenna will build critical components for future terahertz communication systems.

Analysis of airborne antenna systems using geometrical theory of diffraction and moment method computer codes

NASA Technical Reports Server (NTRS)

Hartenstein, Richard G., Jr.

1985-01-01

Computer codes have been developed to analyze antennas on aircraft and in the presence of scatterers. The purpose of this study is to use these codes to develop accurate computer models of various aircraft and antenna systems. The antenna systems analyzed are a P-3B L-Band antenna, an A-7E UHF relay pod antenna, and traffic advisory antenna system installed on a Bell Long Ranger helicopter. Computer results are compared to measured ones with good agreement. These codes can be used in the design stage of an antenna system to determine the optimum antenna location and save valuable time and costly flight hours.

Antenna-coupled unbiased detectors for LW-IR regime

NASA Astrophysics Data System (ADS)

Tiwari, Badri Nath

At room temperature (300K), the electromagnetic (EM) radiation emitted by humans and other living beings peaks mostly in the long-wavelength infrared (LW-IR) regime. And since the atmosphere shows relatively little absorption in this band, applications such as target detection, tracking, active homing, and navigation in autonomous vehicles extensively use the LW-IR frequency range. The present research work is focused on developing antenna-based, uncooled, and unbiased detectors for the LW-IR regime. In the first part of this research, antenna-coupled metal-oxide-metal diodes (ACMOMD) are investigated. In response to the EM radiation, high-frequency antenna currents are induced in the antenna. An asymmetric-barrier Al-Al2O3-Pt MOM diode rectifies the antenna currents. Two different types of fabrication processes have been developed for ACMOMDs namely one-step lithography and two-step lithography. The major drawbacks of MOM-based devices include hard-to-control fabrication processes, generally very high zero-biased resistances, and vulnerability to electrostatic discharges, leading to unstable electrical characteristics. The second part of this research focuses on the development of unbiased LW-IR sensors based on the Seebeck effect. If two different metals are joined together at one end and their other ends are open-circuited, and if a non-zero temperature difference exists between the joined end and the open ends, then a non-zero open-circuit voltage can be measured between the open ends of the wires. Based on this effect, we have developed antenna-coupled nano-thermocouples (ACNTs) in which radiation-induced antenna currents produce polarization-dependent heating of the joined end of the two metals whereas the open ends remain at substrate temperature. This polarization-dependent heating induces polarization-dependent temperature difference between the joined end and the open ends of the metals leading to a polarization-dependent open-circuit voltage between the

'Invisible' antenna takes up less space

NASA Astrophysics Data System (ADS)

Shelley, M.; Bond, K.

1986-06-01

A compensated microstrip patch design is described that also uses grounded coplanar waveguide to permit a second, independent antenna to be mounted on any type of existing primary radar antenna aboard an aircraft without affecting its radiation. Successful integration of the IFF (identification friend or foe) antenna, which works at D-band, and the primary radar antenna is possible because of the diversity in frequency between the two antennas. Construction of a microstrip radiating element, electromagnetically invisible to the primary antenna, requires orthogonal grating elements and use of the primary antenna as the ground plane. Coplanar mounting of a stripline array with the primary antenna reduces the manufacturing costs and increases the functional performance of the IFF antenna.

One- and two-dimensional antenna arrays for microwave wireless power transfer (MWPT) systems and dual-antenna transceivers

NASA Astrophysics Data System (ADS)

Lin, Yo-Sheng; Hu, Chun-Hao; Chang, Chi-Ho; Tsao, Ping-Chang

2018-06-01

In this work, we demonstrate novel one-dimensional (1D) and two-dimensional (2D) antenna arrays for both microwave wireless power transfer (MWPT) systems and dual-antenna transceivers. The antenna array can be used as the MWPT receiving antenna of an integrated MWPT and Bluetooth (BLE) communication module (MWPT-BLE module) for smart CNC (computer numerical control) spindle incorporated with the cloud computing system SkyMars. The 2D antenna array has n rows of 1 × m 1D array, and each array is composed of multiple (m) differential feeding antenna elements. Each differential feeding antenna element is a differential feeding structure with a microstrip antenna stripe. The stripe length is shorter than one wavelength to minimise the antenna area and to prevent being excited to a high-order mode. That is, the differential feeding antenna element can suppress the even mode. The mutual coupling between the antenna elements can be suppressed, and the isolation between the receiver and the transmitter can be enhanced. An inclination angle of the main beam aligns with the broadside, and the main beam is further concentrated and shrunk at the elevation direction. Moreover, if more differential feeding antenna elements are used, antenna gain and isolation can be further enhanced. The excellent performance of the proposed antenna arrays indicates that they are suitable for both MWPT systems and dual-antenna transceivers.

Using a focal-plane array to estimate antenna pointing errors

NASA Technical Reports Server (NTRS)

Zohar, S.; Vilnrotter, V. A.

1991-01-01

The use of extra collecting horns in the focal plane of an antenna as a means of determining the Direction of Arrival (DOA) of the signal impinging on it, provided it is within the antenna beam, is considered. Our analysis yields a relatively simple algorithm to extract the DOA from the horns' outputs. An algorithm which, in effect, measures the thermal noise of the horns' signals and determines its effect on the uncertainty of the extracted DOA parameters is developed. Both algorithms were implemented in software and tested in simulated data. Based on these tests, it is concluded that this is a viable approach to the DOA determination. Though the results obtained are of general applicability, the particular motivation for the present work is their application to the pointing of a mechanically deformed antenna. It is anticipated that the pointing algorithm developed for a deformed antenna could be obtained as a small perturbation of the algorithm developed for an undeformed antenna. In this context, it should be pointed out that, with a deformed antenna, the array of horns and its associated circuitry constitute the main part of the deformation-compensation system. In this case, the pointing system proposed may be viewed as an additional task carried out by the deformation-compensation hardware.

Development of theoretical models of integrated millimeter wave antennas

NASA Technical Reports Server (NTRS)

Yngvesson, K. Sigfrid; Schaubert, Daniel H.

1991-01-01

Extensive radiation patterns for Linear Tapered Slot Antenna (LTSA) Single Elements are presented. The directivity of LTSA elements is predicted correctly by taking the cross polarized pattern into account. A moment method program predicts radiation patterns for air LTSAs with excellent agreement with experimental data. A moment method program was also developed for the task LTSA Array Modeling. Computations performed with this program are in excellent agreement with published results for dipole and monopole arrays, and with waveguide simulator experiments, for more complicated structures. Empirical modeling of LTSA arrays demonstrated that the maximum theoretical element gain can be obtained. Formulations were also developed for calculating the aperture efficiency of LTSA arrays used in reflector systems. It was shown that LTSA arrays used in multibeam systems have a considerable advantage in terms of higher packing density, compared with waveguide feeds. Conversion loss of 10 dB was demonstrated at 35 GHz.

Design and Development of VHF Antennas for Space Borne Signal of Opportunity Receivers for Cubesat Platforms

NASA Technical Reports Server (NTRS)

Deshpande, Manohar; Piepmeier, Jeffrey

2015-01-01

Design and Development of VHF Antennas for Space Borne Signal of Opportunity Receivers for Cubesat Platforms. Space borne microwave remote sensors at VHF/UHF frequencies are important instruments to observe reflective properties of land surfaces through thick and heavy forestation on a global scale. One of the most cost effective ways of measuring land reflectivity at VHF/UHF frequencies is to use signals transmitted by existing communication satellites (operating at VHF/UHF band) as a signal of opportunity (SoOp) signal and passive receivers integrated with airborne/space borne platforms operating in the Low Earth Orbit (LEO). One of the critical components of the passive receiver is two antennas (one to receive only direct signal and other to receive only reflected signal) which need to have ideally high (>30dB) isolation. However, because of small size of host platforms and broad beam width of dipole antennas, achieving adequate isolation between two channels is a challenging problem and need to be solved for successful implementation of space borne SoOp technology for remote sensing. In this presentation a novel enabling VHF antenna technology for Cubesat platforms is presented to receive direct as well as reflected signal with needed isolation. The novel scheme also allows enhancing the gain of individual channels by factor of 2 without use of reflecting ground plane

Low-Profile, Dual-Wavelength, Dual-Polarized Antenna

NASA Technical Reports Server (NTRS)

Carswell, James R.

2010-01-01

A single-aperture, low-profile antenna design has been developed that supports dual-polarization and simultaneous operation at two wavelengths. It realizes multiple beams in the elevation plane, and supports radiometric, radar, and conical scanning applications. This antenna consists of multiple azimuth sticks, with each stick being a multilayer, hybrid design. Each stick forms the h-plane pattern of the C and Ku-band vertically and horizontally polarized antenna beams. By combining several azimuth sticks together, the elevation beam is formed. With a separate transceiver for each stick, the transmit phase and amplitude of each stick can be controlled to synthesize a beam at a specific incidence angle and to realize a particular side-lobe pattern. By changing the transmit phase distribution through the transceivers, the transmit antenna beam can be steered to different incidence angles. By controlling the amplitude distribution, different side lobe patterns and efficiencies can be realized. The receive beams are formed using digital beam synthesis techniques, resulting in very little loss in the receive path, thus enabling a very-low loss receive antenna to support passive measurements.

ATCRBS Antenna Modification Kit

DOT National Transportation Integrated Search

1976-06-01

The report describes the design, fabrication and test results of an improved ATCRBS (Air Traffic Control Radar Beacon System) array antenna for mounting on the reflector of an ASR radar antenna. The antenna consists of a 4-foot high by 26-foot wide a...

Mutual Elements and Substrate Effect Analysis on Patch Antenna Arrays

NASA Astrophysics Data System (ADS)

Wallace, Matthew J.

There have been many different technology advancements with the invention of solid state electronics, leading to the digital era which has changed the way users employ electronic circuits. Antennas are no different; however, they are still analog devices. With the advancements in technology, antennas are being fabricated on much higher frequencies and with greater bandwidths, all while trying to keep size and weight to a minimum. Centimeter and millimeter wave technologies have evolved for many different radio frequency (RF) applications. Microstrip patch antennas have been developed, as wire and tubular antenna elements are difficult to fabricate with the tolerances required at micro-wavelengths. Microstrip patch antennas are continuously being improved. These types of antennas are great for embedded or conformal applications where size and weight are of the essence and the ease of manufacturing elements to tight tolerances is important. One of the greatest benefits of patch antennas is the ease in creating an array. Many simulation programs have been created to assist in the design of patch antennas and arrays. However, there are still discrepancies between simulated results and actual measurements. This research will focus on these differences. It begins with a literature research of patch antenna design, followed by an assessment of simulation programs used for patch antenna design. The resulting antenna design was realized by the fabrication of an antenna from the Genesys software. Laboratory measurements of the real-world antenna are then compared to the theoretical antenna characteristics. This process is used to illustrate deficiencies in the software models and likely improvements that need to be made.

Microstrip patch antenna for simultaneous strain and temperature sensing

NASA Astrophysics Data System (ADS)

Mbanya Tchafa, F.; Huang, H.

2018-06-01

A patch antenna, consisting of a radiation patch, a dielectric substrate, and a ground plane, resonates at distinct fundamental frequencies that depend on the substrate dielectric constant and the dimensions of the radiation patch. Since these parameters change with the applied strain and temperature, this study investigates simultaneous strain and temperature sensing using a single antenna that has two fundamental resonant frequencies. The theoretical relationship between the antenna resonant frequency shifts, the temperature, and the applied strain was first established to guide the selection of the dielectric substrate, based on which an antenna sensor with a rectangular radiation patch was designed and fabricated. A tensile test specimen instrumented with the antenna sensor was subjected to thermo-mechanical tests. Experiment results validated the theoretical predictions that the normalized antenna resonant frequency shifts are linearly proportional to the applied strain and temperature changes. An inverse method was developed to determine the strain and temperature changes from the normalized antenna resonant frequency shifts, yielding measurement uncertainty of 0.4 °C and 17.22 μ \\varepsilon for temperature and strain measurement, respectively.

Microstrip Yagi array antenna for mobile satellite vehicle application

NASA Technical Reports Server (NTRS)

Huang, John; Densmore, Arthur C.

1991-01-01

A novel antenna structure formed by combining the Yagi-Uda array concept and the microstrip radiator technique is discussed. This antenna, called the microstrip Yagi array, has been developed for the mobile satellite (MSAT) system as a low-profile, low-cost, and mechanically steered medium-gain land-vehicle antenna. With the antenna's active patches (driven elements) and parasitic patches (reflector and director elements) located on the same horizontal plane, the main beam of the array can be tilted, by the effect of mutual coupling, in the elevation direction providing optimal coverage for users in the continental United States. Because the parasitic patches are not connected to any of the lossy RF power distributing circuit the antenna is an efficient radiating system. With the complete monopulse beamforming and power distributing circuits etched on a single thin stripline board underneath the microstrip Yagi array, the overall L-band antenna system has achieved a very low profile for vehicle's rooftop mounting, as well as a low manufacturing cost. Experimental results demonstrate the performance of this antenna.

Optically addressed ultra-wideband phased antenna array

NASA Astrophysics Data System (ADS)

Bai, Jian

Demands for high data rate and multifunctional apertures from both civilian and military users have motivated development of ultra-wideband (UWB) electrically steered phased arrays. Meanwhile, the need for large contiguous frequency is pushing operation of radio systems into the millimeter-wave (mm-wave) range. Therefore, modern radio systems require UWB performance from VHF to mm-wave. However, traditional electronic systems suffer many challenges that make achieving these requirements difficult. Several examples includes: voltage controlled oscillators (VCO) cannot provide a tunable range of several octaves, distribution of wideband local oscillator signals undergo high loss and dispersion through RF transmission lines, and antennas have very limited bandwidth or bulky sizes. Recently, RF photonics technology has drawn considerable attention because of its advantages over traditional systems, with the capability of offering extreme power efficiency, information capacity, frequency agility, and spatial beam diversity. A hybrid RF photonic communication system utilizing optical links and an RF transducer at the antenna potentially provides ultra-wideband data transmission, i.e., over 100 GHz. A successful implementation of such an optically addressed phased array requires addressing several key challenges. Photonic generation of an RF source with over a seven-octave bandwidth has been demonstrated in the last few years. However, one challenge which still remains is how to convey phased optical signals to downconversion modules and antennas. Therefore, a feed network with phase sweeping capability and low excessive phase noise needs to be developed. Another key challenge is to develop an ultra-wideband array antenna. Modern frontends require antennas to be compact, planar, and low-profile in addition to possessing broad bandwidth, conforming to stringent space, weight, cost, and power constraints. To address these issues, I will study broadband and miniaturization

47 CFR 95.1013 - Antennas.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 5 2013-10-01 2013-10-01 false Antennas. 95.1013 Section 95.1013... SERVICES Low Power Radio Service (LPRS) General Provisions § 95.1013 Antennas. (a) The maximum allowable... this chapter, at the band edges. (b) AMTS stations must employ directional antennas. (c) Antennas used...

47 CFR 95.1213 - Antennas.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 5 2011-10-01 2011-10-01 false Antennas. 95.1213 Section 95.1213... SERVICES Medical Device Radiocommunication Service (MedRadio) § 95.1213 Antennas. No antenna for a MedRadio transmitter shall be configured for permanent outdoor use. In addition, any MedRadio antenna used outdoors...

47 CFR 95.1013 - Antennas.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 5 2012-10-01 2012-10-01 false Antennas. 95.1013 Section 95.1013... SERVICES Low Power Radio Service (LPRS) General Provisions § 95.1013 Antennas. (a) The maximum allowable... this chapter, at the band edges. (b) AMTS stations must employ directional antennas. (c) Antennas used...

47 CFR 95.1213 - Antennas.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 5 2010-10-01 2010-10-01 false Antennas. 95.1213 Section 95.1213... SERVICES Medical Device Radiocommunication Service (MedRadio) § 95.1213 Antennas. No antenna for a MedRadio transmitter shall be configured for permanent outdoor use. In addition, any MedRadio antenna used outdoors...

47 CFR 95.1013 - Antennas.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 5 2011-10-01 2011-10-01 false Antennas. 95.1013 Section 95.1013... SERVICES Low Power Radio Service (LPRS) General Provisions § 95.1013 Antennas. (a) The maximum allowable... this chapter, at the band edges. (b) AMTS stations must employ directional antennas. (c) Antennas used...

47 CFR 95.1013 - Antennas.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 5 2014-10-01 2014-10-01 false Antennas. 95.1013 Section 95.1013... SERVICES Low Power Radio Service (LPRS) General Provisions § 95.1013 Antennas. (a) The maximum allowable... this chapter, at the band edges. (b) AMTS stations must employ directional antennas. (c) Antennas used...

47 CFR 95.1013 - Antennas.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 5 2010-10-01 2010-10-01 false Antennas. 95.1013 Section 95.1013... SERVICES Low Power Radio Service (LPRS) General Provisions § 95.1013 Antennas. (a) The maximum allowable... this chapter, at the band edges. (b) AMTS stations must employ directional antennas. (c) Antennas used...

Analysis of the stress-deformed condition of the disassembly parabolic antenna

NASA Astrophysics Data System (ADS)

Odinets, M. N.; Kaygorodtseva, N. V.; Krysova, I. V.

2018-01-01

Active development of satellite communications and computer-aided design systems raises the problem of designing parabolic antennas on a new round of development. The aim of the work was to investigate the influence of the design of the mirror of a parabolic antenna on its endurance under wind load. The research task was an automated analysis of the stress-deformed condition of various designs of computer models of a paraboloid mirror (segmented or holistic) at modeling the exploitation conditions. The peculiarity of the research was that the assembly model of the antenna’s mirror was subjected to rigid connections on the contacting surfaces of the segments and only then the finite element grid was generated. The analysis showed the advantage of the design of the demountable antenna, which consists of cyclic segments, in front of the construction of the holistic antenna. Calculation of the stress-deformed condition of the antennas allows us to conclude that dividing the design of the antenna’s mirror on parabolic and cyclic segments increases it strength and rigidity. In the future, this can be used to minimize the mass of antenna and the dimensions of the disassembled antenna. The presented way of modeling a mirror of a parabolic antenna using to the method of the finite-element analysis can be used in the production of antennas.

Dependence of Helicon Antenna Loading on the Antenna/Plasma Gap and n|| in DIII-D Experiments

NASA Astrophysics Data System (ADS)

Pinsker, R. I.; Moeller, C. P.

2017-10-01

A comprehensive set of measurements of the plasma loading of a 12-element antenna array, designed to launch helicon waves (i.e., very-high-harmonic fast waves), were performed on DIII-D in 2016. The antenna, operated in the 466 - 486 MHz band, is prototypical of a wider array for a 1-MW-level experiment planned for 2018-9. The dependence of the antenna loading on antenna/plasma gap is of great practical significance, as the gap must be kept greater than a minimum distance to suppress deleterious plasma-material interactions, while the loading must be high enough to retain good efficiency of power transfer to the plasma. While the loading in all examined plasma regimes, including both limited and diverted L-mode discharges and H-mode discharges, decayed exponentially with increasing gap in agreement with simple theory, the characteristic decay length was in all cases larger than expected, motivating the development of a more realistic model. Furthermore, the characteristic decay length did not depend on the launched n||, though the absolute level of loading at a given gap increased as |n||| was decreased from 4 to 2. After the antenna was removed from DIII-D, measurements of the loading produced by a 100 Ω/sq resistive film were carried out on the bench. Both the antenna/film gap and n|| were scanned varied and the results compared with calculations done with the QuickWave FDTD electromagnetics solver. Very good agreement was found in this case. Work supported by the US DOE under DE-FC02-04ER54698.

Antenna Efficiency and the Genius of the IEEE Standard for Antenna Terms [Education Column

NASA Astrophysics Data System (ADS)

Warnick, Karl F.

2012-08-01

At a 2007 Square Kilometre Array Design Studies (SKADS) workshop in Dwingeloo, Wim van Cappellen of the Nether lands Institute for Radio Astronomy (ASTRON) gave a presentation on figures of merit, in which he memorably compared antenna terms to apples. What seems like a simple, homogeneous fruit comes in all colors and varieties. Similarly, a survey of antenna literature and textbooks shows that authors use a wide variety of antenna figures of merit, often not in compliance with the relevant IEEE Standard Definitions of Terms for Antennas [1]. Since this standard is now in the process of revision by the Antennas and Propagation Society Antenna Standards Committee, it seems worth while to consider the standard, and clarify some common misunderstandings and inconsistent usages.

Carbon Nanotube Thin-Film Antennas.

PubMed

Puchades, Ivan; Rossi, Jamie E; Cress, Cory D; Naglich, Eric; Landi, Brian J

2016-08-17

Multiwalled carbon nanotube (MWCNT) and single-walled carbon nanotube (SWCNT) dipole antennas have been successfully designed, fabricated, and tested. Antennas of varying lengths were fabricated using flexible bulk MWCNT sheet material and evaluated to confirm the validity of a full-wave antenna design equation. The ∼20× improvement in electrical conductivity provided by chemically doped SWCNT thin films over MWCNT sheets presents an opportunity for the fabrication of thin-film antennas, leading to potentially simplified system integration and optical transparency. The resonance characteristics of a fabricated chlorosulfonic acid-doped SWCNT thin-film antenna demonstrate the feasibility of the technology and indicate that when the sheet resistance of the thin film is >40 ohm/sq no power is absorbed by the antenna and that a sheet resistance of <10 ohm/sq is needed to achieve a 10 dB return loss in the unbalanced antenna. The dependence of the return loss performance on the SWCNT sheet resistance is consistent with unbalanced metal, metal oxide, and other CNT-based thin-film antennas, and it provides a framework for which other thin-film antennas can be designed.

Antenna-Coupled Bolometer Arrays for Astrophysics

NASA Astrophysics Data System (ADS)

Bock, James

Bolometers offer the best sensitivity in the far-infrared to millimeter-wave region of the electromagnetic spectrum. We are developing arrays of feedhorn-coupled bolometers for the ESA/NASA Planck Surveyor and Herschel Space Observatory. Advances in the format and sensitivity of bolometric focal plane array enables future astrophysics mission opportunities, such as CMB polarimetry and far-infrared/submillimeter spectral line surveys. Compared to bolometers with extended area radiation absorbers, antenna-coupled bolometers offer active volumes that are orders of magnitude smaller. Coupled to lithographed micro-strip filters and antennas, antenna-coupled bolometer arrays allow flexible focal plane architectures specialized for imaging, polarimetry, and spectroscopy. These architectures greatly reduce the mass of sub-Kelvin bolometer focal planes that drive the design of bolometric instrumentation.

View of Antenna #1 (foreground), and Antenna #2 surface doors. ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

View of Antenna #1 (foreground), and Antenna #2 surface doors. Image looking northeast - Titan One Missile Complex 2A, .3 miles west of 129 Road and 1.5 miles north of County Line Road, Aurora, Adams County, CO

Implantable multilayer microstrip antenna for retinal prosthesis: antenna testing.

PubMed

Permana, Hans; Fang, Qiang; Rowe, Wayne S T

2012-01-01

Retinal prosthesis has come to a more mature stage and become a very strategic answer to Retinitis Pigmentosa (RP) and Age-related Macular Degeneration (AMD) diseases. In a retinal prosthesis system, wireless link holds a great importance for the continuity of the system. In this paper, an implantable multilayer microstrip antenna was proposed for the retinal prosthesis system. Simulations were performed in High Frequency Structure Simulator (HFSS) with the surrounding material of air and Vitreous Humor fluid. The fabricated antenna was measured for characteristic validation in free space. The results showed that the real antenna possessed similar return loss and radiation pattern, while there was discrepancy with the gain values.

Ion source with external RF antenna

DOEpatents

Leung, Ka-Ngo; Ji, Qing; Wilde, Stephen

2005-12-13

A radio frequency (RF) driven plasma ion source has an external RF antenna, i.e. the RF antenna is positioned outside the plasma generating chamber rather than inside. The RF antenna is typically formed of a small diameter metal tube coated with an insulator. An external RF antenna assembly is used to mount the external RF antenna to the ion source. The RF antenna tubing is wound around the external RF antenna assembly to form a coil. The external RF antenna assembly is formed of a material, e.g. quartz, which is essentially transparent to the RF waves. The external RF antenna assembly is attached to and forms a part of the plasma source chamber so that the RF waves emitted by the RF antenna enter into the inside of the plasma chamber and ionize a gas contained therein. The plasma ion source is typically a multi-cusp ion source.

UHF coplanar-slot antenna for aircraft-to-satellite data communications

NASA Technical Reports Server (NTRS)

Myhre, R. W.

1979-01-01

A lightweight low drag coplanar slot antenna was developed for use on commercial jet aircraft that will provide upper hemisphere coverage in the UHF band at frequencies of 402 and 468 MHz is described. The antenna is designed to transmit meteorological data from wide body jet aircraft to ground users via synchronous meteorological data relay satellites. The low profile antenna (23.5 cm wide by 38.1 cm long slot by 1.9 cm high) is a conformal antenna utilizing the coplanar approach with the advantages of broad frequency bandwidth and improved electrical integrity over wide range of temperature. The antenna is circular polarized, has anon axis gain of near +2.5 dB, and a HPBW greater than 90 deg. Areas discussed include antenna design, radiation characteristics, flight testing, and system performance.

DIRECTIONAL ANTENNA

DOEpatents

Bittner, B.J.

1958-05-20

A high-frequency directional antenna of the 360 d scaring type is described. The antenna has for its desirable features the reduction in both size and complexity of the mechanism for rotating the antenna through its scanning movement. These advantages result from the rotation of only the driven element, the reflector remaining stationary. The particular antenna structure comprises a refiector formed by a plurality of metallic slats arranged in the configuration of an annular cage having the shape of a zone of revolution. The slats are parallel to each other and are disposed at an angle of 45 d to the axis of the cage. A directional radiator is disposed inside the cage at an angle of 45 d to the axis of the cage in the same direction as the reflecting slats which it faces. As the radiator is rotated, the electromagnetic wave is reflected from the slats facing the radiator and thereafter passes through the cage on the opposite side, since these slats are not parallel with the E vector of the wave.

47 CFR 80.866 - Spare antenna.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 5 2011-10-01 2011-10-01 false Spare antenna. 80.866 Section 80.866... Spare antenna. A spare transmitting antenna completely assembled for immediate erection must be provided. If the installed transmitting antenna is suspended between supports, this spare antenna must be a...

47 CFR 80.866 - Spare antenna.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 5 2013-10-01 2013-10-01 false Spare antenna. 80.866 Section 80.866... Spare antenna. A spare transmitting antenna completely assembled for immediate erection must be provided. If the installed transmitting antenna is suspended between supports, this spare antenna must be a...

47 CFR 80.866 - Spare antenna.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 5 2014-10-01 2014-10-01 false Spare antenna. 80.866 Section 80.866... Spare antenna. A spare transmitting antenna completely assembled for immediate erection must be provided. If the installed transmitting antenna is suspended between supports, this spare antenna must be a...

47 CFR 80.866 - Spare antenna.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 5 2012-10-01 2012-10-01 false Spare antenna. 80.866 Section 80.866... Spare antenna. A spare transmitting antenna completely assembled for immediate erection must be provided. If the installed transmitting antenna is suspended between supports, this spare antenna must be a...

47 CFR 80.866 - Spare antenna.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 5 2010-10-01 2010-10-01 false Spare antenna. 80.866 Section 80.866... Spare antenna. A spare transmitting antenna completely assembled for immediate erection must be provided. If the installed transmitting antenna is suspended between supports, this spare antenna must be a...

Inflatable Antenna Microwave Radiometer for Soil Moisture Measurement

NASA Technical Reports Server (NTRS)

Bailey, M. C.; Kendall, Bruce M.; Schroeder, Lyle C.; Harrington, Richard F.

1993-01-01

Microwave measurements of soil moisture are not being obtained at the required spatial Earth resolution with current technology. Recently, new novel designs for lightweight reflector systems have been developed using deployable inflatable antenna structures which could enable lightweight real-aperture radiometers. In consideration of this, a study was conducted at the NASA Langley Research Center (LaRC) to determine the feasibility of developing a microwave radiometer system using inflatable reflector antenna technology to obtain high spatial resolution radiometric measurements of soil moisture from low Earth orbit and which could be used with a small and cost effective launch vehicle. The required high resolution with reasonable swath width coupled with the L-band measurement frequency for soil moisture dictated the use of a large (30 meter class) real aperture antenna in conjunction with a pushbroom antenna beam configuration and noise-injection type radiometer designs at 1.4 and 4.3 GHz to produce a 370 kilometer cross-track swath with a 10 kilometer resolution that could be packaged for launch with a Titan 2 class vehicle. This study includes design of the inflatable structure, control analysis, structural and thermal analysis, antenna and feed design, radiometer design, payload packaging, orbital analysis, and electromagnetic losses in the thin membrane inflatable materials.

Wide sector coverage antennas

NASA Astrophysics Data System (ADS)

Yaw, D. F.

1984-09-01

The general design and performance characteristics of transmit and receive antennas that are currently used in electronic warfare systems are reviewed. Among transmit antennas, three-to-one bandwidth, asymmetric-beam, and circularly polarized horns are discussed, as are extremely broadband monopoles and spiral antennas. In a discussion of receive antennas, attention is given to flat and conical spirals, including cavity-backed flat spirals operating over the 2.5-18 GHz range; log periodic dipoles; and biconical horns. Finally, the design configurations and performance of interferometer direction-finding systems are briefly discussed.

View of Antenna #1 (foreground), and Antenna #2 surface doors. ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

View of Antenna #1 (foreground), and Antenna #2 surface doors. Orientation Target #2 in background. Image looking northeast - Titan One Missile Complex 2A, .3 miles west of 129 Road and 1.5 miles north of County Line Road, Aurora, Adams County, CO

View of Antenna #2 (foreground), and Antenna #1 surface doors. ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

View of Antenna #2 (foreground), and Antenna #1 surface doors. Orientation Target #1 in background. Image looking northwest - Titan One Missile Complex 2A, .3 miles west of 129 Road and 1.5 miles north of County Line Road, Aurora, Adams County, CO

47 CFR 73.69 - Antenna monitors.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 4 2011-10-01 2011-10-01 false Antenna monitors. 73.69 Section 73.69... Broadcast Stations § 73.69 Antenna monitors. (a) Each station using a directional antenna must have in operation at the transmitter site an FCC authorized antenna monitor. (b) In the event that the antenna...

47 CFR 73.69 - Antenna monitors.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 4 2014-10-01 2014-10-01 false Antenna monitors. 73.69 Section 73.69... Broadcast Stations § 73.69 Antenna monitors. (a) Each station using a directional antenna must have in operation at the transmitter site an FCC authorized antenna monitor. (b) In the event that the antenna...

47 CFR 73.69 - Antenna monitors.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 4 2013-10-01 2013-10-01 false Antenna monitors. 73.69 Section 73.69... Broadcast Stations § 73.69 Antenna monitors. (a) Each station using a directional antenna must have in operation at the transmitter site an FCC authorized antenna monitor. (b) In the event that the antenna...

47 CFR 73.69 - Antenna monitors.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 4 2010-10-01 2010-10-01 false Antenna monitors. 73.69 Section 73.69... Broadcast Stations § 73.69 Antenna monitors. (a) Each station using a directional antenna must have in operation at the transmitter site an FCC authorized antenna monitor. (b) In the event that the antenna...

47 CFR 73.69 - Antenna monitors.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 4 2012-10-01 2012-10-01 false Antenna monitors. 73.69 Section 73.69... Broadcast Stations § 73.69 Antenna monitors. (a) Each station using a directional antenna must have in operation at the transmitter site an FCC authorized antenna monitor. (b) In the event that the antenna...

Optical Links and RF Distribution for Antenna Arrays

NASA Technical Reports Server (NTRS)

Huang, Shouhua; Calhoun, Malcolm; Tjoelker, Robert

2006-01-01

An array of three antennas has recently been developed at the NASA Jet Propulsion Laboratory capable of detecting signals at X and Ka band. The array requires a common frequency reference and high precision phase alignment to correlate received signals. Frequency and timing references are presently provided from a remotely located hydrogen maser and clock through a combination of commercially and custom developed optical links. The selected laser, photodetector, and fiber components have been tested under anticipated thermal and simulated antenna rotation conditions. The resulting stability limitations due to thermal perturbations or induced stress on the optical fiber have been characterized. Distribution of the X band local oscillator includes a loop back and precision phase monitor to enable correlation of signals received from each antenna.

From antenna to antenna: lateral shift of olfactory memory recall by honeybees.

PubMed

Rogers, Lesley J; Vallortigara, Giorgio

2008-06-04

Honeybees, Apis mellifera, readily learn to associate odours with sugar rewards and we show here that recall of the olfactory memory, as demonstrated by the bee extending its proboscis when presented with the trained odour, involves first the right and then the left antenna. At 1-2 hour after training using both antennae, recall is possible mainly when the bee uses its right antenna but by 6 hours after training a lateral shift has occurred and the memory can now be recalled mainly when the left antenna is in use. Long-term memory one day after training is also accessed mainly via the left antenna. This time-dependent shift from right to left antenna is also seen as side biases in responding to odour presented to the bee's left or right side. Hence, not only are the cellular events of memory formation similar in bees and vertebrate species but also the lateralized networks involved may be similar. These findings therefore seem to call for remarkable parallel evolution and suggest that the proper functioning of memory formation in a bilateral animal, either vertebrate or invertebrate, requires lateralization of processing.

Performance of a family of omni and steered antennas for mobile satellite applications

NASA Technical Reports Server (NTRS)

Woo, K.; Huang, J.; Jamnejad, V.; Bell, D.; Berner, J.; Estabrook, P.; Densmore, A.

1990-01-01

The design and performance of a family of vehicle antennas developed at JPL in support of an emerging US Mobile Satellite Service (MSS) system are described. Test results of the antennas are presented. Trends for future development are addressed. Recommendations on design approaches for vehicle antennas of the first generation MSS are discussed.

Characterisation and optimisation of Ground Penetrating Radar antennas

NASA Astrophysics Data System (ADS)

Warren, Craig; Giannopoulos, Antonios

2014-05-01

Research on the characterisation and optimisation of Ground Penetrating Radar (GPR) antennas will be presented as part of COST Action TU1208 "Civil Engineering Applications of Ground Penetrating Radar". This work falls within the remit of Working Group 1 - "Novel GPR instrumentation" which focuses on the design of innovative GPR equipment for Civil Engineering (CE) applications, on the building of prototypes and on the testing and optimisation of new systems. The diversity of applications of GPR has meant there are a number of different GPR antenna designs available to the end-user as well as those being used in the research community. The type and size of a GPR antenna is usually dependent on the application, e.g. low frequency antennas, which are physically larger, are used where significant depth of penetration is important, whereas high frequency antennas, which are physically smaller, are used where less penetration and better resolution are required. Understanding how energy is transmitted and received by a particular GPR antenna has many benefits: it could lead to more informed usage of the antenna in GPR surveys; improvements in antenna design; and better interpretation of GPR signal returns from the ground/structure. The radiation characteristics of a particular antenna are usually investigated by studying the radiation patterns and directivity. For GPR antennas it is also important to study these characteristics when the antenna is in different environments that would typically be encountered in GPR surveys. In this work Finite-Difference Time-Domain (FDTD) numerical models of GPR antennas have been developed. These antenna models replicate all the detailed geometry and main components of the real antennas. The models are representative of typical high-frequency, high-resolution GPR antennas primarily used in CE for the evaluation of structural features in concrete: the location of rebar, conduits, and post-tensioned cables, as well as the estimation of

47 CFR 80.863 - Antenna system.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 5 2011-10-01 2011-10-01 false Antenna system. 80.863 Section 80.863... Antenna system. (a) An antenna system must be installed which is as nondirectional and as efficient as is... construction of the required antenna must insure operation in time of emergency. (b) If the required antenna is...

47 CFR 80.863 - Antenna system.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 5 2014-10-01 2014-10-01 false Antenna system. 80.863 Section 80.863... Antenna system. (a) An antenna system must be installed which is as nondirectional and as efficient as is... construction of the required antenna must insure operation in time of emergency. (b) If the required antenna is...

47 CFR 80.863 - Antenna system.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 5 2012-10-01 2012-10-01 false Antenna system. 80.863 Section 80.863... Antenna system. (a) An antenna system must be installed which is as nondirectional and as efficient as is... construction of the required antenna must insure operation in time of emergency. (b) If the required antenna is...

47 CFR 80.863 - Antenna system.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 5 2013-10-01 2013-10-01 false Antenna system. 80.863 Section 80.863... Antenna system. (a) An antenna system must be installed which is as nondirectional and as efficient as is... construction of the required antenna must insure operation in time of emergency. (b) If the required antenna is...

Development of a Compact Eleven Feed Cryostat for the Patriot 12-m Antenna System

NASA Technical Reports Server (NTRS)

Beaudoin, Christopher; Kildal, Per-Simon; Yang, Jian; Pantaleev, Miroslav

2010-01-01

The Eleven antenna has constant beam width, constant phase center location, and low spillover over a decade bandwidth. Therefore, it can feed a reflector for high aperture efficiency (also called feed efficiency). It is equally important that the feed efficiency and its subefficiencies not be degraded significantly by installing the feed in a cryostat. The MIT Haystack Observatory, with guidance from Onsala Space Observatory and Chalmers University, has been working to integrate the Eleven antenna into a compact cryostat suitable for the Patriot 12-m antenna. Since the analysis of the feed efficiencies in this presentation is purely computational, we first demonstrate the validity of the computed results by comparing them to measurements. Subsequently, we analyze the dependence of the cryostat size on the feed efficiencies, and, lastly, the Patriot 12-m subreflector is incorporated into the computational model to assess the overall broadband efficiency of the antenna system.

Design of shape memory alloy actuated intelligent parabolic antenna for space applications

NASA Astrophysics Data System (ADS)

Kalra, Sahil; Bhattacharya, Bishakh; Munjal, B. S.

2017-09-01

The deployment of large flexible antennas is becoming critical for space applications today. Such antenna systems can be reconfigured in space for variable antenna footprint, and hence can be utilized for signal transmission to different geographic locations. Due to quasi-static shape change requirements, coupled with the demand of large deflection, shape memory alloy (SMA) based actuators are uniquely suitable for this system. In this paper, we discuss the design and development of a reconfigurable parabolic antenna structure. The reflector skin of the antenna is vacuum formed using a metalized polycarbonate shell. Two different strategies are chosen for the antenna actuation. Initially, an SMA wire based offset network is formed on the back side of the reflector. A computational model is developed using equivalent coefficient of thermal expansion (ECTE) for the SMA wire. Subsequently, the interaction between the antenna and SMA wire is modeled as a constrained recovery system, using a 1D modified Brinson model. Joule effect based SMA phase transformation is considered for the relationship between input voltage and temperature at the SMA wire. The antenna is modeled using ABAQUS based finite element methodology. The deflection found through the computational model is compared with that measured in experiment. Subsequently, a point-wise actuation system is developed for higher deflection. For power-minimization, an auto-locking device is developed. The performance of the new configuration is compared with the offset-network configuration. It is envisaged that the study will provide a comprehensive procedure for the design of intelligent flexible structures especially suitable for space applications.

GPS Attitude Determination Using Deployable-Mounted Antennas

NASA Technical Reports Server (NTRS)

Osborne, Michael L.; Tolson, Robert H.

1996-01-01

The primary objective of this investigation is to develop a method to solve for spacecraft attitude in the presence of potential incomplete antenna deployment. Most research on the use of the Global Positioning System (GPS) in attitude determination has assumed that the antenna baselines are known to less than 5 centimeters, or one quarter of the GPS signal wavelength. However, if the GPS antennas are mounted on a deployable fixture such as a solar panel, the actual antenna positions will not necessarily be within 5 cm of nominal. Incomplete antenna deployment could cause the baselines to be grossly in error, perhaps by as much as a meter. Overcoming this large uncertainty in order to accurately determine attitude is the focus of this study. To this end, a two-step solution method is proposed. The first step uses a least-squares estimate of the baselines to geometrically calculate the deployment angle errors of the solar panels. For the spacecraft under investigation, the first step determines the baselines to 3-4 cm with 4-8 minutes of data. A Kalman filter is then used to complete the attitude determination process, resulting in typical attitude errors of 0.50.

Analysis of resonant fast ion distributions during combined ICRF and NBI heating with transients using neutron emission spectroscopy

NASA Astrophysics Data System (ADS)

Hellesen, C.; Mantsinen, M.; Conroy, S.; Ericsson, G.; Eriksson, J.; Kiptily, V. G.; Nabais, F.; Contributors, JET

2018-05-01

ICRF heating at the fundamental cyclotron frequency of a hydrogen minority ion species also gives rise to a partial power absorption by deuterium ions at their second harmonic resonance. This paper studies the deuterium distributions resulting from such 2nd harmonic heating at JET using neutron emission spectroscopy data from the time of flight spectrometer TOFOR. The fast deuterium distributions are obtained over the energy range 100 keV to 2 MeV. Specifically, we study how the fast deuterium distributions vary as ICRF heating is used alone as well as in combination with NBI heating. When comparing the different heating scenarios, we observed both a difference in the shapes of the distributions as well as in their absolute level. The differences are most pronounced below 0.5 MeV. Comparisons are made with corresponding distributions calculated with the code PION. We find a good agreement between the measured distributions and those calculated with PION, both in terms of their shapes as well as their amplitudes. However, we also identified a period with signs of an inverted fast ion distribution, which showed large disagreements between the modeled and measured results. Resonant interactions with tornado modes, i.e. core localized toroidal alfven eigenmodes (TAEs), are put forward as a possible explanation for the inverted distribution.

Antenna Design Considerations for the Advanced Extravehicular Mobility Unit

NASA Technical Reports Server (NTRS)

Bakula, Casey J.; Theofylaktos, Onoufrios

2015-01-01

NASA is designing an Advanced Extravehicular Mobility Unit (AEMU)to support future manned missions beyond low-Earth orbit (LEO). A key component of the AEMU is the communications assembly that allows for the wireless transfer of voice, video, and suit telemetry. The Extravehicular Mobility Unit (EMU) currently used on the International Space Station (ISS) contains a radio system with a single omni-directional resonant cavity antenna operating slightly above 400 MHz capable of transmitting and receiving data at a rate of about 125 kbps. Recent wireless communications architectures are calling for the inclusion of commercial wireless standards such as 802.11 that operate in higher frequency bands at much higher data rates. The current AEMU radio design supports a 400 MHz band for low-rate mission-critical data and a high-rate band based on commercial wireless local area network (WLAN) technology to support video, communication with non-extravehicular activity (EVA) assets such as wireless sensors and robotic assistants, and a redundant path for mission-critical EVA data. This paper recommends the replacement of the existing EMU antenna with a new antenna that maintains the performance characteristics of the current antenna but with lower weight and volume footprints. NASA has funded several firms to develop such an antenna over the past few years, and the most promising designs are variations on the basic patch antenna. This antenna technology at UHF is considered by the authors to be mature and ready for infusion into NASA AEMU technology development programs.

Antennas for 20/30 GHz and beyond

NASA Technical Reports Server (NTRS)

Chen, C. Harry; Wong, William C.; Hamada, S. Jim

1989-01-01

Antennas of 20/30 GHz and higher frequency, due to the small wavelength, offer capabilities for many space applications. With the government-sponsored space programs (such as ACTS) in recent years, the industry has gone through the learning curve of designing and developing high-performance, multi-function antennas in this frequency range. Design and analysis tools (such as the computer modelling used in feedhorn design and reflector surface and thermal distortion analysis) are available. The components/devices (such as BFN's, weight modules, feedhorns and etc.) are space-qualified. The manufacturing procedures (such as reflector surface control) are refined to meet the stringent tolerance accompanying high frequencies. The integration and testing facilities (such as Near-Field range) also advance to facilitate precision assembling and performance verification. These capabilities, essential to the successful design and development of high-frequency spaceborne antennas, shall find more space applications (such as ESGP) than just communications.

Ka-band monopulse antenna-pointing systems analysis and simulation

NASA Technical Reports Server (NTRS)

Lo, V. Y.

1996-01-01

NASA 's Deep Space Network (DSN) has been using both 70-m and 34-m reflector antennas to communicate with spacecraft at S-band (2.3 GHz) and X-band (8.45 GHz). To improve the quality of telecommunication and to meet future mission requirements, JPL has been developing 34-m Ka-band (32-GHz) beam waveguide antennas. Presently, antenna pointing operates in either the open-loop mode with blind pointing using navigation predicts or the closed-loop mode with conical scan (conscan). Pointing accuracy under normal conscan operating conditions is in the neighborhood of 5 mdeg. This is acceptable at S- and X-bands, but not enough at Ka-band. Due to the narrow beamwidth at Ka-band, it is important to improve pointing accuracy significantly (approximately 2 mdeg). Monopulse antenna tracking is one scheme being developed to meet the stringent pointing-accuracy requirement at Ka-band. Other advantages of monopulse tracking include low sensitivity to signal amplitude fluctuations as well as single-pulse processing for acquisition and tracking. This article presents system modeling, signal processing, simulation, and implementation of Ka-band monopulse tracking feed for antennas in NASA/DSN ground stations.

A microfabricated low-profile wideband antenna array for terahertz communications.

PubMed

Luk, K M; Zhou, S F; Li, Y J; Wu, F; Ng, K B; Chan, C H; Pang, S W

2017-04-28

While terahertz communications are considered to be the future solutions for the increasing demands on bandwidth, terahertz equivalents of radio frequency front-end components have not been realized. It remains challenging to achieve wideband, low profile antenna arrays with highly directive beams of radiation. Here, based on the complementary antenna approach, a wideband 2 × 2 cavity-backed slot antenna array with a corrugated surface is proposed. The approach is based on a unidirectional antenna with a cardiac radiation pattern and stable frequency characteristics that is achieved by integrating a series-resonant electric dipole with a parallel-resonant magnetic dipole. In this design, the slots work as magnetic dipoles while the corrugated surface radiates as an array of electric dipoles. The proposed antenna is realized at 1 THz operating frequency by stacking multiple metallized layers using the microfabrication technology. S-parameter measurements of this terahertz low-profile metallic antenna array demonstrate high efficiency at terahertz frequencies. Fractional bandwidth and gain are measured to be 26% and 14 dBi which are consistent with the simulated results. The proposed antenna can be used as the building block for larger antenna arrays with more directive beams, paving the way to develop high gain low-profile antennas for future communication needs.

Design of broadband single polarized antenna

NASA Astrophysics Data System (ADS)

Shin, Phoo Kho; Aziz, Mohamad Zoinol Abidin Abd.; Ahmad, Badrul Hisham; Ramli, Mohamad Hafize Bin; Fauzi, Noor Azamiah Md; Malek, Mohd Fareq Abd

2015-05-01

In practical wireless communication application, bandwidth enhancement becomes one of the major design considerations. At the same time, circular polarized (CP) antenna received much attention for the applications of modern wireless communication system when compared to linear polarized (LP) antenna. This is because CP antenna can reduce the multipath effect. Hence, broadband antenna with operating frequency at 2.4GHz for WLAN application is proposed. The proposed antenna is done by using L-probe amendment with rectangular patch. The rectangular patch and copper ground plane is separated with 10mm air gap. This approach is used to enhance the bandwidth and the gain of the proposed antenna. The bandwidth of the designed antenna is more than 200MHz which meet broadband application. The return loss for the antenna is below -10dB to achieved 90% matching efficiency. The position of L-probe feed is altered in order to obtained different polarizations. The broadband antenna had been designed and simulated by using Computer Simulation Technology (CST) software. In this paper, the comparison for single polarized antenna with the design of non-inverted patch and inverted patch is discussed. The characteristics of the S-parameter, axial ratio, gain, surface current for each designed antenna are analyzed.

Improved Gain Microstrip Patch Antenna

DTIC Science & Technology

2015-08-06

08-2015 Publication Improved Gain Microstrip Patch Antenna David A. Tonn Naval Under Warfare Center Division, Newport 1176 Howell St., Code 00L...GAIN MICROSTRIP PATCH ANTENNA STATEMENT OF GOVERNMENT INTEREST [0001] The invention described herein may be manufactured and used by or for the...patch antenna having increased gain, and an apparatus for increasing the gain and bandwidth of an existing microstrip patch antenna . (2) Description

Screen printed UHF antennas on flexible substrates

NASA Astrophysics Data System (ADS)

Janeczek, Kamil; Młożniak, Anna; Kozioł, Grażyna; Araźna, Aneta; Jakubowska, Małgorzata; Bajurko, Paweł

2010-09-01

Printed electronics belongs to the most important developing electronics technologies. It provides new possibilities to produce low cost and large area devices. In its range several applications can be distinguished like printed batteries, OLED, biosensors, photovoltaic cells or RFID tags. In the presented investigation, antennas working in UHF frequency range were elaborated. It can be applied in the future for flexible RFID tags. To produce these antennas polymer paste with silver flakes was used. It was deposited on two flexible substrates (foil and photo paper) with screen printing techniques. After printing process surface profile, electrical and microwave parameters of performed antennas were measured using digital multimeter and network analyzer, relatively. Furthermore, a thickness of printed layers was measured.

Multi-mode horn antenna simulation

NASA Technical Reports Server (NTRS)

Dod, L. R.; Wolf, J. D.

1980-01-01

Radiation patterns were computed for a circular multimode horn antenna using waveguide electric field radiation expressions. The circular multimode horn was considered as a possible reflector feed antenna for the Large Antenna Multifrequency Microwave Radiometer (LAMMR). This horn antenna uses a summation of the TE sub 11 deg and TM sub 11 deg modes to generate far field primary radiation patterns with equal E and H plane beamwidths and low sidelobes. A computer program for the radiation field expressions using the summation of waveguide radiation modes is described. The sensitivity of the multimode horn antenna radiation patterns to phase variations between the two modes is given. Sample radiation pattern calculations for a reflector feed horn for LAMMR are shown. The multimode horn antenna provides a low noise feed suitable for radiometric applications.

Antenna Calibration and Measurement Equipment

NASA Technical Reports Server (NTRS)

Rochblatt, David J.; Cortes, Manuel Vazquez

2012-01-01

A document describes the Antenna Calibration & Measurement Equipment (ACME) system that will provide the Deep Space Network (DSN) with instrumentation enabling a trained RF engineer at each complex to perform antenna calibration measurements and to generate antenna calibration data. This data includes continuous-scan auto-bore-based data acquisition with all-sky data gathering in support of 4th order pointing model generation requirements. Other data includes antenna subreflector focus, system noise temperature and tipping curves, antenna efficiency, reports system linearity, and instrument calibration. The ACME system design is based on the on-the-fly (OTF) mapping technique and architecture. ACME has contributed to the improved RF performance of the DSN by approximately a factor of two. It improved the pointing performances of the DSN antennas and productivity of its personnel and calibration engineers.

Spiral microstrip antenna with resistance

NASA Technical Reports Server (NTRS)

Shively, David G. (Inventor)

1994-01-01

The present invention relates to microstrip antennas, and more particularly to wide bandwidth spiral antennas with resistive loading. A spiral microstrip antenna having resistor element embedded in each of the spiral arms is provided. The antenna is constructed using a conductive back plane as a base. The back plane supports a dielectric slab having a thickness between one-sixteenth and one-quarter of an inch. A square spiral, having either two or four arms, is attached to the dielectric slab. Each arm of the spiral has resistor elements thereby dissipating an excess energy not already emitted through radiation. The entire configuration provides a thin, flat, high gain, wide bandwidth antenna which requires no underlying cavity. The configuration allows the antenna to be mounted conformably on an aircraft surface.

A survey of ATL-compatible radiometer antennas

NASA Technical Reports Server (NTRS)

Love, A. W.

1975-01-01

A survey was made of antennas suitable for remote sensing of the earth's surface, in particular the world ocean, by means of microwave radiometers operating in the 1 to 26 GHz frequency region and carried on board the shuttle-launched advanced technology laboratory. Array antennas are found to be unattractive and unsuited to the task. Reflectors, including Cassegrain and offset types, as well as horn-reflectors are possible candidates but all have shortcomings which impair the accuracy of measurement. Horns of the corrugated type have excellent electrical characteristics. Although they are physically very large and will require development of suitable deployment mechanisms, they appear to be valid candidates for the task. The evolution of the periscope antenna is outlined, and it is shown to possess nearly ideal electrical characteristics for the intended application. Its only shortcoming is that the feed horn creates aperture blocking; there is no blocking due to struts or any other source. The periscope antenna is recommended for ATL radiometry.

Visualization of electromagnetic exposure near LTE antennae

NASA Astrophysics Data System (ADS)

Zvezdina, M. Yu; Shokova, Yu A.; Nazarova, O. Yu; Al-Ali, H. T. A.; Al-Farhan, G. H. A.

2018-01-01

Technical progress in wireless data transfer has given an opportunity to apply information and communication technologies in various areas of economics. Digital economy is linked to the 4th and 5th generation mobile network deployment. The peculiarities of the abovementioned standards decrease BTS antenna range three times in dense developed areas and worsen electromagnetic background in big cities. In the paper the comparative assessment results for rooftop electromagnetic exposure near BTS LTE and BTS GSM antennae are given. It is shown, that at the same level of transmitter power, energy flux density for LTE standard is three times less than the one for GSM. Moreover, the conclusion is made that the rooftop could be considered safe for people for indefinite time if antenna is placed more than 5 meters above the rooftop. The value of antenna height is taken to be on the safe side, as it is required by an application of “preventive principle”.

Broadband Cylindrical Antenna and Method

DTIC Science & Technology

2016-07-27

1 of 12 BROADBAND CYLINDRICAL ANTENNA AND METHOD STATEMENT OF GOVERNMENT INTEREST [0001] The invention described herein may be manufactured and...directed to a cylindrical antenna having a broader bandwidth and a method for making such an antenna . (2) Description of the Prior Art [0004...Slotted cylinder antennas have been proposed in submarine applications before. For example, in U.S. Patent No. 6,127,983, Rivera and Josypenko disclose

Measurements of AAFE RADSCAT antenna characteristics

NASA Technical Reports Server (NTRS)

Cross, A. E.; Jones, W. L., Jr.; Jones, A. L.

1977-01-01

Antenna characteristics (active and passive) for a modified AAFE-RADSCAT parabolic dish antenna are documented for a variety of antenna configurations. The modified antenna was a replacement for the original unit which was damaged in January 1975. Pattern measurements made at Langley Research Center and Johnson Space Center are presented, with an analysis of the results. Antenna loss measurements are also presented and summarized.

Hybrid Deployable Foam Antennas and Reflectors

NASA Technical Reports Server (NTRS)

Rivellini, Tommaso; Willis, Paul; Hodges, Richard; Spitz, Suzanne

2006-01-01

small volume - typically to 1/20 of its full size in one dimension. 4) At a temperature above its glass-transition temperature (T(sub g)), the foam strongly damps vibrations. Even at a temperature below T(sub g), the damping should exceed that of other materials. 5) In its macroscopic mechanical properties, an open-cell foam is isotropic. This isotropy facilitates computational modeling of antenna structures. 6) Through chemical formulation, the T(sub g) of an open-cell polyurethane foam can be set at a desired value between about - 100 and about 0 C. Depending on the application, it may or may not be necessary to rigidify a foam structure after deployment. If rigidification is necessary, then the T(sub g) of the foam can be tailored to exceed the temperature of the deployment environment, in conjunction with providing a heater to elasticize the foam for deployment. Once deployed, the foam would become rigidified by cooling to below T(sub g). 7) Techniques for molding or machining polymeric foams (especially including open-cell polyurethane foams) to desired sizes and shapes are well developed.

Metamaterial-based "sabre" antenna

NASA Astrophysics Data System (ADS)

Hafdallah Ouslimani, Habiba; Yuan, Tangjie; Kanane, Houcine; Priou, Alain; Collignon, Gérard; Lacotte, Guillaume

2014-05-01

The "sabre" antenna is an array of two monopole elements, vertically polarized with omnidirectional radiation patterns, and placed on either side of a composite material on the tail of an airplane. As an in-phase reflector plane, the antenna uses a compact dual-layer high-impedance surface (DL-HIS) with offset mushroom-like Sivenpiper square shape unit cells. This topology allows one to control both operational frequency and bandgap width, while reducing the total height of the antenna to under λ0/36. The designed antenna structure has a wide bandwidth higher than 24% around 1.4 GHz. The measurements and numerical simulations agree very well.

The Millimeter Wave Observatory antenna now at INAOE-Mexico

NASA Astrophysics Data System (ADS)

Luna, A.

2017-07-01

The antenna of 5 meters in diameter of the legendary "Millimeter Wave Observatory" is now installed in the INAOE-Mexico. This historic antenna was reinstalled and was equipped with a control system and basic primary focus receivers that enabled it in teaching activities. We work on the characterization of its surface and on the development of receivers and spectrometers to allow it to do research Solar and astronomical masers. The historical contributions of this antenna to science and technology in radio astronomy, serve as the guiding force and the inspiration of the students and technicians of our postgrade in Astrophysics. It is enough to remember that it was with this antenna, that the first molecular outflow was discovered, several lines of molecular emission were discovered and it was the first antenna whose surface was characterized by holography; among many other technological and scientific contributions.

Optical antenna enhanced spontaneous emission

PubMed Central

Eggleston, Michael S.; Messer, Kevin; Zhang, Liming; Yablonovitch, Eli; Wu, Ming C.

2015-01-01

Atoms and molecules are too small to act as efficient antennas for their own emission wavelengths. By providing an external optical antenna, the balance can be shifted; spontaneous emission could become faster than stimulated emission, which is handicapped by practically achievable pump intensities. In our experiments, InGaAsP nanorods emitting at ∼200 THz optical frequency show a spontaneous emission intensity enhancement of 35× corresponding to a spontaneous emission rate speedup ∼115×, for antenna gap spacing, d = 40 nm. Classical antenna theory predicts ∼2,500× spontaneous emission speedup at d ∼ 10 nm, proportional to 1/d2. Unfortunately, at d < 10 nm, antenna efficiency drops below 50%, owing to optical spreading resistance, exacerbated by the anomalous skin effect (electron surface collisions). Quantum dipole oscillations in the emitter excited state produce an optical ac equivalent circuit current, Io = qω|xo|/d, feeding the antenna-enhanced spontaneous emission, where q|xo| is the dipole matrix element. Despite the quantum-mechanical origin of the drive current, antenna theory makes no reference to the Purcell effect nor to local density of states models. Moreover, plasmonic effects are minor at 200 THz, producing only a small shift of antenna resonance frequency. PMID:25624503

Optical antenna enhanced spontaneous emission

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

Eggleston, Michael S.; Messer, Kevin; Zhang, Liming

Atoms and molecules are too small to act as efficient antennas for their own emission wavelengths. By providing an external optical antenna, the balance can be shifted; spontaneous emission could become faster than stimulated emission, which is handicapped by practically achievable pump intensities. In our experiments, InGaAsP nanorods emitting at ~200 THz optical frequency show a spontaneous emission intensity enhancement of 35 × corresponding to a spontaneous emission rate speedup ~115 ×, for antenna gap spacing, d = 40 nm. Classical antenna theory predicts ~2,500 × spontaneous emission speedup at d ~10 nm, proportional to 1/d 2. Unfortunately, at dmore » < 10 nm, antenna efficiency drops below 50%, owing to optical spreading resistance, exacerbated by the anomalous skin effect (electron surface collisions). Quantum dipole oscillations in the emitter excited state produce an optical ac equivalent circuit current, I(o) = qω|x(o)|/d, feeding the antenna-enhanced spontaneous emission, where q|x(o)| is the dipole matrix element. Despite the quantum-mechanical origin of the drive current, antenna theory makes no reference to the Purcell effect nor to local density of states models. Additionally, plasmonic effects are minor at 200 THz, producing only a small shift of antenna resonance frequency.« less

Optical antenna enhanced spontaneous emission.

PubMed

Eggleston, Michael S; Messer, Kevin; Zhang, Liming; Yablonovitch, Eli; Wu, Ming C

2015-02-10

Atoms and molecules are too small to act as efficient antennas for their own emission wavelengths. By providing an external optical antenna, the balance can be shifted; spontaneous emission could become faster than stimulated emission, which is handicapped by practically achievable pump intensities. In our experiments, InGaAsP nanorods emitting at ∼ 200 THz optical frequency show a spontaneous emission intensity enhancement of 35 × corresponding to a spontaneous emission rate speedup ∼ 115 ×, for antenna gap spacing, d = 40 nm. Classical antenna theory predicts ∼ 2,500 × spontaneous emission speedup at d ∼ 10 nm, proportional to 1/d(2). Unfortunately, at d < 10 nm, antenna efficiency drops below 50%, owing to optical spreading resistance, exacerbated by the anomalous skin effect (electron surface collisions). Quantum dipole oscillations in the emitter excited state produce an optical ac equivalent circuit current, I(o) = qω|x(o)|/d, feeding the antenna-enhanced spontaneous emission, where q|x(o)| is the dipole matrix element. Despite the quantum-mechanical origin of the drive current, antenna theory makes no reference to the Purcell effect nor to local density of states models. Moreover, plasmonic effects are minor at 200 THz, producing only a small shift of antenna resonance frequency.

Optical antenna enhanced spontaneous emission

DOE PAGES

Eggleston, Michael S.; Messer, Kevin; Zhang, Liming; ...

2015-01-26

Atoms and molecules are too small to act as efficient antennas for their own emission wavelengths. By providing an external optical antenna, the balance can be shifted; spontaneous emission could become faster than stimulated emission, which is handicapped by practically achievable pump intensities. In our experiments, InGaAsP nanorods emitting at ~200 THz optical frequency show a spontaneous emission intensity enhancement of 35 × corresponding to a spontaneous emission rate speedup ~115 ×, for antenna gap spacing, d = 40 nm. Classical antenna theory predicts ~2,500 × spontaneous emission speedup at d ~10 nm, proportional to 1/d 2. Unfortunately, at dmore » < 10 nm, antenna efficiency drops below 50%, owing to optical spreading resistance, exacerbated by the anomalous skin effect (electron surface collisions). Quantum dipole oscillations in the emitter excited state produce an optical ac equivalent circuit current, I(o) = qω|x(o)|/d, feeding the antenna-enhanced spontaneous emission, where q|x(o)| is the dipole matrix element. Despite the quantum-mechanical origin of the drive current, antenna theory makes no reference to the Purcell effect nor to local density of states models. Additionally, plasmonic effects are minor at 200 THz, producing only a small shift of antenna resonance frequency.« less

Trade-off between land vehicle antenna cost and gain for satellite mobile communications

NASA Technical Reports Server (NTRS)

1984-01-01

Trade-offs between antenna cost and gain made for nine antennas as a feasibility study for the experimental land mobile satellite system, M-SAT(X) reported. This system is under development by JPL-NASA for a mobile telephone system to be used throughout the continental USA and Alaska. The mobile antenna is a key element in the development of this system.

Features and technologies of ERS-1 (ESA) and X-SAR antennas

NASA Technical Reports Server (NTRS)

Schuessler, R.; Wagner, R.

1986-01-01

Features and technologies of planar waveguide array antennas developed for spaceborne microwave sensors are described. Such antennas are made from carbon fiber reinforced plastic (CFRP) employing special manufacturing and metallization techniques to achieve satisfactory electrical properties. Mechanical design enables deployable antenna structures necessary for satellite applications (e.g., ESA ERS-1). The slotted waveguide concept provides high aperture efficiency, good beamshaping capabilities, and low losses. These CFRP waveguide antennas feature low mass, high accuracy and stiffness, and can be operated within wide temperature ranges.

Advanced Antenna Measurement Processing

DTIC Science & Technology

2014-06-18

reflector antenna where the reflector functions as a passive scatterer. Here we proposed to demonstrate this separation scheme using experimentally derived...orders in the multiple reflections between these antennas . The nature of these composite patterns is not known a priori so one cannot know the accuracy...SECURITY CLASSIFICATION OF: This research project is focused on the advancement of methods of post measurement processing of antenna pattern

Quartz antenna with hollow conductor

DOEpatents

Leung, Ka-Ngo; Benabou, Elie

2002-01-01

A radio frequency (RF) antenna for plasma ion sources is formed of a hollow metal conductor tube disposed within a glass tube. The hollow metal tubular conductor has an internal flow channel so that there will be no coolant leakage if the outer glass tube of the antenna breaks. A portion of the RF antenna is formed into a coil; the antenna is used for inductively coupling RF power to a plasma in an ion source chamber. The antenna is made by first inserting the metal tube inside the glass tube, and then forming the glass/metal composite tube into the desired coil shape.

UHF Microstrip Antenna Array for Synthetic- Aperture Radar

NASA Technical Reports Server (NTRS)

Thomas, Robert F.; Huang, John

2003-01-01

An ultra-high-frequency microstrippatch antenna has been built for use in airborne synthetic-aperture radar (SAR). The antenna design satisfies requirements specific to the GeoSAR program, which is dedicated to the development of a terrain-mapping SAR system that can provide information on geology, seismicity, vegetation, and other terrain-related topics. One of the requirements is for ultra-wide-band performance: the antenna must be capable of operating with dual linear polarization in the frequency range of 350 plus or minus 80 MHz, with a peak gain of 10 dB at the middle frequency of 350 MHz and a gain of at least 8 dB at the upper and lower ends (270 and 430 MHz) of the band. Another requirement is compactness: the antenna must fit in the wingtip pod of a Gulfstream II airplane. The antenna includes a linear array of microstrip-patch radiating elements supported over square cavities. Each patch is square (except for small corner cuts) and has a small square hole at its center.

Beam-Steerable Flat-Panel Reflector Antenna

NASA Technical Reports Server (NTRS)

Lee, Choon Sae; Lee, Chanam; Miranda, Felix A.

2005-01-01

Many space applications require a high-gain antenna that can be easily deployable in space. Currently, the most common high-gain antenna for space-born applications is an umbrella-type reflector antenna that can be folded while being lifted to the Earth orbit. There have been a number of issues to be resolved for this type of antenna. The reflecting surface of a fine wire mesh has to be light in weight and flexible while opening up once in orbit. Also the mesh must be a good conductor at the operating frequency. In this paper, we propose a different type of high-gain antenna for easy space deployment. The proposed antenna is similar to reflector antennas except the curved main reflector is replaced by a flat reconfigurable surface for easy packing and deployment in space. Moreover it is possible to steer the beam without moving the entire antenna system.

Broadband active electrically small superconductor antennas

NASA Astrophysics Data System (ADS)

Kornev, V. K.; Kolotinskiy, N. V.; Sharafiev, A. V.; Soloviev, I. I.; Mukhanov, O. A.

2017-10-01

A new type of broadband active electrically small antenna (ESA) based on superconducting quantum arrays (SQAs) has been proposed and developed. These antennas are capable of providing both sensing and amplification of broadband electromagnetic signals with a very high spurious-free dynamic range (SFDR)—up to 100 dB (and even more)—with high sensitivity. The frequency band can range up to tens of gigahertz, depending on Josephson junction characteristic frequency, set by fabrication. In this paper we review theoretical and experimental studies of SQAs and SQA-based antenna prototypes of both transformer and transformer-less types. The ESA prototypes evaluated were fabricated using a standard Nb process with critical current density 4.5 kA cm-2. Measured device characteristics, design issues and comparative analysis of various ESA types, as well as requirements for interfaces, are reviewed and discussed.

An antenna-pointing mechanism for the ETS-6 K-band Single Access (KSA) antenna

NASA Technical Reports Server (NTRS)

Takada, Noboru; Amano, Takahiro; Ohhashi, Toshiro; Wachi, Shigeo

1991-01-01

Both the design philosophy for the Antenna Pointing Mechanism (APM) to be used for the K-band Single Access (KSA) antenna system and experimental results of the APM Engineering Model (EM) tests are described. The KSA antenna system will be flown on the Engineering Test Satellite 6 (ETS-6).

Unfurlable satellite antennas - A review

NASA Technical Reports Server (NTRS)

Roederer, Antoine G.; Rahmat-Samii, Yahia

1989-01-01

A review of unfurlable satellite antennas is presented. Typical application requirements for future space missions are first outlined. Then, U.S. and European mesh and inflatable antenna concepts are described. Precision deployables using rigid panels or petals are not included in the survey. RF modeling and performance analysis of gored or faceted mesh reflector antennas are then reviewed. Finally, both on-ground and in-orbit RF test techniques for large unfurlable antennas are discussed.

Broad band antennas and feed methods

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

Benzel, David M.; Twogood, Richard E.

Two or more Vivaldi antennas, consisting of two plates each, each with the antenna's natural impedance of approximately 100 ohms, are placed in parallel to achieve a 50 ohm impedance in the case of two antennas or other impedances (100/n ohms) for more than two antennas. A single Vivaldi antenna plate (half Vivaldi antenna) over a ground plane can also be used to achieve a 50 ohm impedance, or two or more single plates over a ground plane to achieve other impedances. Unbalanced 50 ohm transmission lines, e.g. coaxial cables, can be used to directly feed, the dual Vivaldi (fourmore » plate) antenna in a center fed angled center departure, or more desirably, a center fed offset departure configuration.« less

Reconfigurable water-substrate based antennas with temperature control

NASA Astrophysics Data System (ADS)

Mobashsher, Ahmed Toaha; Abbosh, Amin

2017-06-01

We report an unexplored reconfigurable antenna development technique utilizing the concept of temperature variable electromagnetic properties of water. By applying this physical phenomena, we present highly efficient water-substrate based antennas whose operating frequencies can be continuously tuned. While taking the advantage of cost-effectiveness of liquid water, this dynamic tuning technique also alleviates the roadblocks to widespread use of reconfigurable liquid-based antennas for VHF and UHF bands. The dynamic reconfigurability is controlled merely via external thermal stimulus and does not require any physical change of the resonating structure. We demonstrate dynamic control of omnidirectional and directional antennas covering more than 14 and 12% fractional bandwidths accordingly, with more than 85% radiation efficiency. Our temperature control approach paves the intriguing way of exploring dynamic reconfigurability of water-based compact electromagnetic devices for non-static, in-motion and low-cost real-world applications.

Geodetic antenna calibration test in the Antarctic environment

USGS Publications Warehouse

Grejner-Brzezinska, A.; Vazquez, E.; Hothem, L.

2006-01-01

TransAntarctic Mountain DEFormation (TAMDEF) Monitoring Network is the NSF-sponsored OSU and USGS project, aimed at measuring crustal motion in the Transantarctic Mountains of Victoria Land using GPS carrier phase measurements. Station monumentation, antenna mounts, antenna types, and data processing strategies were optimized to achieve mm-level estimates for the rates of motion. These data contributes also to regional Antarctic frame definition. Significant amount of data collected over several years allow the investigation of unique aspects of GPS geodesy in Antarctica, to determine how the error spectrum compares to the mid-latitude regions, and to identify the optimum measurement and data processing schemes for Antarctic conditions, in order to test the predicted rates of motion (mm-level w.r.t. time). The data collection for the TAMDEF project was initiated in 1996. The primary antenna used has been the Ashtech L1/L2 Dorne Margolin (D/M) choke ring. A few occupations involved the use of a Trimble D/M choke ring. The data were processed using the antenna calibration data available from the National Geodetic Survey (NGS). The recent developments in new antenna designs that are lighter in weight and lower in cost are being considered as a possible alternative to the bulkier and more expensive D/M choke ring design. In November 2003, in situ testing of three alternative models of L1/L2 antennas was conducted at a site located in the vicinity of McMurdo Station, Antarctica (S77.87, E166.56). The antenna models used in this test were: Ashtech D/M choke ring, Trimble D/M choke ring, Trimble Zephyr, and the NovAtel GPS-702. Two stations, spaced within 30 meters, were used in the test. Both had the characteristics similar to the stations of the TAMDEF network, i.e., the UNAVCO fixed-height, force-centered level mounts with a constant antenna offset were used, ensuring extreme stability of the antenna/ mount/pin set up. During each of the four 3-day test data collection

Broadband Pillbox Antennas.

DTIC Science & Technology

1984-09-21

Identify by block number) - FIELD GROUP SUB-GROUP Double layer pillbox antennas Triple layer pillbox antenna The possibility of designing very broadband... Design .................... 1 Broadband Feed De gn ........................................... 2 Ex mental Simulation of Double Layer Pillbox...5 REFERENCES ................................................... 6 APPENDIX - COAXIAL TO WAVEGUIDE JUNCTION DESIGN

Novel method to control antenna currents based on theory of characteristic modes

NASA Astrophysics Data System (ADS)

Elghannai, Ezdeen Ahmed

Characteristic Mode Theory is one of the very few numerical methods that provide a great deal of physical insight because it allows us to determine the natural modes of the radiating structure. The key feature of these modes is that the total induced antenna current, input impedance/admittance and radiation pattern can be expressed as a linear weighted combination of individual modes. Using this decomposition method, it is possible to study the behavior of the individual modes, understand them and therefore control the antennas behavior; in other words, control the currents induced on the antenna structure. This dissertation advances the topic of antenna design by carefully controlling the antenna currents over the desired frequency band to achieve the desired performance specifications for a set of constraints. Here, a systematic method based on the Theory of Characteristic Modes (CM) and lumped reactive loading to achieve the goal of current control is developed. The lumped reactive loads are determined based on the desired behavior of the antenna currents. This technique can also be used to impedance match the antenna to the source/generator connected to it. The technique is much more general than the traditional impedance matching. Generally, the reactive loads that properly control the currents exhibit a combination of Foster and non-Foster behavior. The former can be implemented with lumped passive reactive components, while the latter can be implemented with lumped non-Foster circuits (NFC). The concept of current control is applied to design antennas with a wide band (impedance/pattern) behavior using reactive loads. We successfully applied this novel technique to design multi band and wide band antennas for wireless applications. The technique was developed to match the antenna to resistive and/or complex source impedance and control the radiation pattern at these frequency bands, considering size and volume constraints. A wide band patch antenna was

The principles of radio engineering and antennas. II Antennas (2nd revised and enlarged edition)

NASA Astrophysics Data System (ADS)

Belotserkovskii, G. B.

This book represents the second part of a textbook for technical schools. The characteristics and parameters of antennas are considered along with transmission lines, the theory of single dipoles and radiator systems, and the technological realization of elements and units of the antenna-feeder system, taking into account filters and multiport networks for microwave communications applications, and ferrite circulators and isolators. The first edition of this textbook was published in 1969. For the current edition, the material in the first edition has been revised, and new material has been introduced. Much attention is given to microwave antennas, including, in particular, arrays with electrical scanning characteristics. Other topics discussed are related to the general principles of antennas, the matching of the impedance of transmission lines, the elements of transmission lines, aperture-type antennas for microwaves, and the functional characteristics of antennas for ultrashort waves.

47 CFR 73.753 - Antenna systems.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 4 2014-10-01 2014-10-01 false Antenna systems. 73.753 Section 73.753... International Broadcast Stations § 73.753 Antenna systems. All international broadcasting stations shall operate with directional antennas. Such antennas shall be designed and operated so that the radiated power in...

47 CFR 73.753 - Antenna systems.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 4 2013-10-01 2013-10-01 false Antenna systems. 73.753 Section 73.753... International Broadcast Stations § 73.753 Antenna systems. All international broadcasting stations shall operate with directional antennas. Such antennas shall be designed and operated so that the radiated power in...

47 CFR 73.753 - Antenna systems.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 4 2012-10-01 2012-10-01 false Antenna systems. 73.753 Section 73.753... International Broadcast Stations § 73.753 Antenna systems. All international broadcasting stations shall operate with directional antennas. Such antennas shall be designed and operated so that the radiated power in...

47 CFR 73.753 - Antenna systems.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 4 2011-10-01 2011-10-01 false Antenna systems. 73.753 Section 73.753... International Broadcast Stations § 73.753 Antenna systems. All international broadcasting stations shall operate with directional antennas. Such antennas shall be designed and operated so that the radiated power in...

47 CFR 73.753 - Antenna systems.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 4 2010-10-01 2010-10-01 false Antenna systems. 73.753 Section 73.753... International Broadcast Stations § 73.753 Antenna systems. All international broadcasting stations shall operate with directional antennas. Such antennas shall be designed and operated so that the radiated power in...

New design concept of monopole antenna array for UHF 7T MRI.

PubMed

Hong, Suk-Min; Park, Joshua Haekyun; Woo, Myung-Kyun; Kim, Young-Bo; Cho, Zang-Hee

2014-05-01

We have developed and evaluated a monopole antenna array that can increase sensitivity at the center of the brain for 7T MRI applications. We have developed a monopole antenna array that has half the length of a conventional dipole antenna with eight channels for brain imaging with a 7T MRI. The eight-channel monopole antenna array and conventional eight-channel transceiver surface coil array were evaluated and compared in terms of transmit properties, specific absorption ratio (SAR), and sensitivity. The sensitivity maps were generated by dividing the SNR map by the flip angle distribution. A single surface coil provides asymmetric sensitivity resulting in reduced sensitivity at the center of the brain. In contrast, a single monopole antenna provides higher sensitivity at the center of the brain. Moreover, the monopole antenna array provides uniform sensitivity over the entire brain, and the sensitivity gain was 1.5 times higher at the center of the brain compared with the surface coil array. The monopole antenna array is a promising candidate for MRI applications, especially for brain imaging in a 7T MRI because it provides increased sensitivity at the center of the brain. Copyright © 2013 Wiley Periodicals, Inc.

Ionospheric effects to antenna impedance

NASA Technical Reports Server (NTRS)

Bethke, K. H.

1986-01-01

The reciprocity between high power satellite antennas and the surrounding plasma are examined. The relevant plasma states for antenna impedance calculations are presented and plasma models, and hydrodynamic and kinetic theory, are discussed. A theory from which a variation in antenna impedance with regard to the radiated power can be calculated for a frequency range well above the plasma resonance frequency is give. The theory can include photo and secondary emission effects in antenna impedance calculations.

Antenna structure with distributed strip

DOEpatents

Rodenbeck, Christopher T.

2008-10-21

An antenna comprises electrical conductors arranged to form a radiating element including a folded line configuration and a distributed strip configuration, where the radiating element is in proximity to a ground conductor. The folded line and the distributed strip can be electrically interconnected and substantially coplanar. The ground conductor can be spaced from, and coplanar to, the radiating element, or can alternatively lie in a plane set at an angle to the radiating element. Embodiments of the antenna include conductor patterns formed on a printed wiring board, having a ground plane, spacedly adjacent to and coplanar with the radiating element. Other embodiments of the antenna comprise a ground plane and radiating element on opposed sides of a printed wiring board. Other embodiments of the antenna comprise conductors that can be arranged as free standing "foils". Other embodiments include antennas that are encapsulated into a package containing the antenna.

Antenna structure with distributed strip

DOEpatents

Rodenbeck, Christopher T [Albuquerque, NM

2008-03-18

An antenna comprises electrical conductors arranged to form a radiating element including a folded line configuration and a distributed strip configuration, where the radiating element is in proximity to a ground conductor. The folded line and the distributed strip can be electrically interconnected and substantially coplanar. The ground conductor can be spaced from, and coplanar to, the radiating element, or can alternatively lie in a plane set at an angle to the radiating element. Embodiments of the antenna include conductor patterns formed on a printed wiring board, having a ground plane, spacedly adjacent to and coplanar with the radiating element. Other embodiments of the antenna comprise a ground plane and radiating element on opposed sides of a printed wiring board. Other embodiments of the antenna comprise conductors that can be arranged as free standing "foils". Other embodiments include antennas that are encapsulated into a package containing the antenna.

A Mars Riometer: Antenna Considerations

NASA Technical Reports Server (NTRS)

Fry, Craig D.

2001-01-01

This is the final report on NASA Grant NAG5-9706. This project explored riometer (relative ionospheric opacity meter) antenna designs that would be practical for a Mars surface or balloon mission. The riometer is an important radio science instrument for terrestrial aeronomy investigations. The riometer measures absorption of cosmic radio waves by the overhead ionosphere. Studies have shown the instrument should work well on Mars, which has an appreciable daytime ionosphere. There has been concern that the required radio receiver antenna (with possibly a 10 meter scale size) would be too large or too difficult to deploy on Mars. This study addresses those concerns and presents several antenna designs and deployment options. It is found that a Mars balloon would provide an excellent platform for the riometer antenna. The antenna can be incorporated into the envelope design, allowing self-deployment of the antenna as the balloon inflates.

The development of the miniaturized waveform receiver with the function measuring Antenna Impedance in space plasmas

NASA Astrophysics Data System (ADS)

Ishii, H.; Kojima, H.; Fukuhara, H.; Okada, S.; Yamakawa, H.

2012-04-01

Plasma wave is one of the most essential physical quantities in the solar terrestrial physics. The role of plasma wave receiver onboard satellites is to detect plasma waves in space with a good signal to noise ratio. There are two types of plasma wave receivers, the sweep frequency analyzer and the waveform capture. While the sweep frequency analyzer provides plasma wave spectra, the waveform capture obtains waveforms with phase information that is significant in studying nonlinear phenomena. Antenna sensors to observe electric fields of the plasma waves show different features in plasmas from in vacuum. The antenna impedances have specific characteristics in the frequency domain because of the dispersion of plasmas. These antenna impedances are expressed with complex number. We need to know not only the antenna impedances but also the transfer functions of plasma wave receiver's circuits in order to calibrate observed waveforms precisely. The impedances of the electric field antennas are affected by a state of surrounding plasmas. Since satellites run through various regions with different plasma parameters, we precisely should measure the antenna impedances onboard spacecraft. On the contrary, we can obtain the plasma density and by measuring the antenna impedances. Several formulas of the antenna impedance measurement system were proposed. A synchronous detection method is used on the BepiColombo Mercury Magnetospheric Orbiter (MMO), which will be launched in 2014. The digital data are stored in the onboard memory. They are read out and converted to the analog waveforms by D/A converter. They are fed into the input of the preamplifiers of antenna sensors through a resistor. We can calculate a transfer function of the circuit by applying the synchronous detection method to the output waveform from waveform receivers and digital data as a signal source. The size of this system is same as an A5 board. In recent years, Application Specific Integrated Circuit (ASIC

Radiation and scattering from cylindrically conformal printed antennas. Ph.D. Thesis Final Report

NASA Technical Reports Server (NTRS)

Kempel, Leo C.; Volakis, John L.

1994-01-01

Microstrip patch antennas offer considerable advantages in terms of weight, aerodynamic drag, cost, flexibility, and observables over more conventional protruding antennas. These flat patch antennas were first proposed over thirty years ago by Deschamps in the United States and Gutton and Baisinot in France. Such antennas have been analyzed and developed for planar as well as curved platforms. However, the methods used in these designs employ gross approximations, suffer from extreme computational burden, or require expensive physical experiments. The goal of this thesis is to develop accurate and efficient numerical modeling techniques which represent actual antenna structures mounted on curved surfaces with a high degree of fidelity. In this thesis, the finite element method is extended to cavity-backed conformal antenna arrays embedded in a circular, metallic, infinite cylinder. Both the boundary integral and absorbing boundary mesh closure conditions will be used for terminating the mesh. These two approaches will be contrasted and used to study the scattering and radiation behavior of several useful antenna configurations. An important feature of this study will be to examine the effect of curvature and cavity size on the scattering and radiation properties of wraparound conformal antenna arrays.

47 CFR 73.510 - Antenna systems.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 4 2011-10-01 2011-10-01 false Antenna systems. 73.510 Section 73.510... Noncommercial Educational FM Broadcast Stations § 73.510 Antenna systems. (a) All noncommercial educational... § 73.316 concerning antenna systems contained in subpart B of this part. (b) Directional antenna. No...

47 CFR 73.510 - Antenna systems.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 4 2010-10-01 2010-10-01 false Antenna systems. 73.510 Section 73.510... Noncommercial Educational FM Broadcast Stations § 73.510 Antenna systems. (a) All noncommercial educational... § 73.316 concerning antenna systems contained in subpart B of this part. (b) Directional antenna. No...

47 CFR 73.510 - Antenna systems.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 4 2013-10-01 2013-10-01 false Antenna systems. 73.510 Section 73.510... Noncommercial Educational FM Broadcast Stations § 73.510 Antenna systems. (a) All noncommercial educational... § 73.316 concerning antenna systems contained in subpart B of this part. (b) Directional antenna. No...

47 CFR 73.510 - Antenna systems.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 4 2014-10-01 2014-10-01 false Antenna systems. 73.510 Section 73.510... Noncommercial Educational FM Broadcast Stations § 73.510 Antenna systems. (a) All noncommercial educational... § 73.316 concerning antenna systems contained in subpart B of this part. (b) Directional antenna. No...

47 CFR 73.510 - Antenna systems.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 4 2012-10-01 2012-10-01 false Antenna systems. 73.510 Section 73.510... Noncommercial Educational FM Broadcast Stations § 73.510 Antenna systems. (a) All noncommercial educational... § 73.316 concerning antenna systems contained in subpart B of this part. (b) Directional antenna. No...

Technique for Radiometer and Antenna Array Calibration with Two Antenna Noise Diodes

NASA Technical Reports Server (NTRS)

Srinivasan, Karthik; Limaye, Ashutosh; Laymon, Charles; Meyer, Paul

2011-01-01

This paper presents a new technique to calibrate a microwave radiometer and phased array antenna system. This calibration technique uses a radiated noise source in addition to an injected noise sources for calibration. The plane of reference for this calibration technique is the face of the antenna and therefore can effectively calibration the gain fluctuations in the active phased array antennas. This paper gives the mathematical formulation for the technique and discusses the improvements brought by the method over the existing calibration techniques.

Solar Power Satellite (SPS) solid-state antenna power combiner

NASA Technical Reports Server (NTRS)

1980-01-01

A low loss power-combining microstrip antenna suitable for solid state solar power satellite (SPS) application was developed. A unique approach for performing both the combining and radiating function in a single cavity-type circuit was verified, representing substantial refinements over previous demonstration models in terms of detailed geometry to obtain good matching and adequate bandwidth at the design frequency. The combiner circuit was designed, built, and tested and the overall results support the view that the solid state power-combining antenna approach is a viable candidate for a solid state SPS antenna building block.

Reflection measurement of waveguide-injected high-power microwave antennas.

PubMed

Yuan, Chengwei; Peng, Shengren; Shu, Ting; Zhang, Qiang; Zhao, Xuelong

2015-12-01

A method for reflection measurements of High-power Microwave (HPM) antennas excited with overmoded waveguides is proposed and studied systemically. In theory, principle of the method is proposed and the data processing formulas are developed. In simulations, a horn antenna excited by a TE11 mode exciter is examined and its reflection is calculated by CST Microwave Studio and by the method proposed in this article, respectively. In experiments, reflection measurements of two HPM antennas are conducted, and the measured results are well consistent with the theoretical expectations.

47 CFR 101.517 - Antennas.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 5 2010-10-01 2010-10-01 false Antennas. 101.517 Section 101.517... SERVICES 24 GHz Service and Digital Electronic Message Service § 101.517 Antennas. (a) Transmitting antennas may be omnidirectional or directional, consistent with coverage and interference requirements. (b...

47 CFR 101.517 - Antennas.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 5 2014-10-01 2014-10-01 false Antennas. 101.517 Section 101.517... SERVICES 24 GHz Service and Digital Electronic Message Service § 101.517 Antennas. (a) Transmitting antennas may be omnidirectional or directional, consistent with coverage and interference requirements. (b...

47 CFR 73.816 - Antennas.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 4 2012-10-01 2012-10-01 false Antennas. 73.816 Section 73.816... Low Power FM Broadcast Stations (LPFM) § 73.816 Antennas. (a) Permittees and licensees may employ nondirectional antennas with horizontal only polarization, vertical only polarization, circular polarization or...

47 CFR 73.816 - Antennas.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 4 2014-10-01 2014-10-01 false Antennas. 73.816 Section 73.816... Low Power FM Broadcast Stations (LPFM) § 73.816 Antennas. (a) Permittees and licensees may employ nondirectional antennas with horizontal only polarization, vertical only polarization, circular polarization or...

47 CFR 73.816 - Antennas.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 4 2010-10-01 2010-10-01 false Antennas. 73.816 Section 73.816... Low Power FM Broadcast Stations (LPFM) § 73.816 Antennas. (a) Permittees and licensees may employ nondirectional antennas with horizontal only polarization, vertical only polarization, circular polarization or...

47 CFR 101.517 - Antennas.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 5 2011-10-01 2011-10-01 false Antennas. 101.517 Section 101.517... SERVICES 24 GHz Service and Digital Electronic Message Service § 101.517 Antennas. (a) Transmitting antennas may be omnidirectional or directional, consistent with coverage and interference requirements. (b...

47 CFR 101.517 - Antennas.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 5 2012-10-01 2012-10-01 false Antennas. 101.517 Section 101.517... SERVICES 24 GHz Service and Digital Electronic Message Service § 101.517 Antennas. (a) Transmitting antennas may be omnidirectional or directional, consistent with coverage and interference requirements. (b...

47 CFR 73.816 - Antennas.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 4 2013-10-01 2013-10-01 false Antennas. 73.816 Section 73.816... Low Power FM Broadcast Stations (LPFM) § 73.816 Antennas. (a) Permittees and licensees may employ nondirectional antennas with horizontal only polarization, vertical only polarization, circular polarization or...

47 CFR 73.816 - Antennas.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 4 2011-10-01 2011-10-01 false Antennas. 73.816 Section 73.816... Low Power FM Broadcast Stations (LPFM) § 73.816 Antennas. (a) Permittees and licensees may employ nondirectional antennas with horizontal only polarization, vertical only polarization, circular polarization or...

47 CFR 101.517 - Antennas.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 5 2013-10-01 2013-10-01 false Antennas. 101.517 Section 101.517... SERVICES 24 GHz Service and Digital Electronic Message Service § 101.517 Antennas. (a) Transmitting antennas may be omnidirectional or directional, consistent with coverage and interference requirements. (b...

Novel Microstrip Patch Antennas with Frequency Agility, Polarization Reconfigurability, Dual Null Steering Capability and Phased Array Antenna with Beam Steering Performance

NASA Astrophysics Data System (ADS)

Babakhani, Behrouz

Nowadays the wireless communication technology is playing an important role in our daily life. People use wireless devices not only as a conventional communication device but also as tracking and navigation tool, web browsing tool, data storage and transfer tool and so for many other reasons. Based on the user demand, wireless communication engineers try to accommodate as many as possible wireless systems and applications in a single device and therefore, creates a multifunctional device. Antenna, as an integral part of any wireless communication systems, should also be evolved and adjusted with development of wireless transceiver systems. Therefore multifunctional antennas have been introduced to support and enhance the functionality on modern wireless systems. The main focus and contribution of this thesis is design of novel multifunctional microstrip antennas with frequency agility, polarization reconfigurablity, dual null steering capability and phased array antenna with beam steering performance. In this thesis, first, a wide bandwidth(1.10 GHz to 1.60 GHz) right-handed circularly polarized (RHCP) directional antenna for global positioning system (GPS) satellite receive application has been introduced which covers all the GPS bands starting from L1 to L5. This design consists of two crossed bow-tie dipole antennas fed with sequentially phase rotated feed network backed with an artificial high impedance surface (HIS) structure to generate high gain directional radiation patterns. This design shows good CP gain and axial ratio (AR) and wide beamwidth performance. Although this design has good radiation quality, the size and the weight can be reduced as future study. In the second design, a frequency agile antenna was developed which also covers the L-band (L1 to L5) satellite communication frequencies. This frequency agile antenna was designed and realized by new implementation of varactor diodes in the geometry of a circular patch antenna. Beside wide frequency

Tissue dielectric measurement using an interstitial dipole antenna.

PubMed

Wang, Peng; Brace, Christopher L

2012-01-01

The purpose of this study was to develop a technique to measure the dielectric properties of biological tissues with an interstitial dipole antenna based upon previous efforts for open-ended coaxial probes. The primary motivation for this technique is to facilitate treatment monitoring during microwave tumor ablation by utilizing the heating antenna without additional intervention or interruption of the treatment. The complex permittivity of a tissue volume surrounding the antenna was calculated from reflection coefficients measured after high-temperature microwave heating by using a rational function model of the antenna's input admittance. Three referencing liquids were needed for measurement calibration. The dielectric measurement technique was validated ex vivo in normal and ablated bovine livers. Relative permittivity and effective conductivity were lower in the ablation zone when compared to normal tissue, consistent with previous results. The dipole technique demonstrated a mean 10% difference of permittivity values when compared to open-ended coaxial cable measurements in the frequency range of 0.5-20 GHz. Variability in measured permittivities could be smoothed by fitting to a Cole-Cole dispersion model. Further development of this technique may facilitate real-time monitoring of microwave ablation treatments through the treatment applicator. © 2011 IEEE

47 CFR 15.203 - Antenna requirement.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 1 2014-10-01 2014-10-01 false Antenna requirement. 15.203 Section 15.203... Antenna requirement. An intentional radiator shall be designed to ensure that no antenna other than that furnished by the responsible party shall be used with the device. The use of a permanently attached antenna...

47 CFR 15.203 - Antenna requirement.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 1 2012-10-01 2012-10-01 false Antenna requirement. 15.203 Section 15.203... Antenna requirement. An intentional radiator shall be designed to ensure that no antenna other than that furnished by the responsible party shall be used with the device. The use of a permanently attached antenna...

47 CFR 15.203 - Antenna requirement.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 1 2011-10-01 2011-10-01 false Antenna requirement. 15.203 Section 15.203... Antenna requirement. An intentional radiator shall be designed to ensure that no antenna other than that furnished by the responsible party shall be used with the device. The use of a permanently attached antenna...

47 CFR 73.1680 - Emergency antennas.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 4 2011-10-01 2011-10-01 false Emergency antennas. 73.1680 Section 73.1680... Rules Applicable to All Broadcast Stations § 73.1680 Emergency antennas. (a) An emergency antenna is one that is erected for temporary use after the authorized main and auxiliary antennas are damaged and...

47 CFR 73.1680 - Emergency antennas.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 4 2013-10-01 2013-10-01 false Emergency antennas. 73.1680 Section 73.1680... Rules Applicable to All Broadcast Stations § 73.1680 Emergency antennas. (a) An emergency antenna is one that is erected for temporary use after the authorized main and auxiliary antennas are damaged and...

47 CFR 15.203 - Antenna requirement.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 1 2013-10-01 2013-10-01 false Antenna requirement. 15.203 Section 15.203... Antenna requirement. An intentional radiator shall be designed to ensure that no antenna other than that furnished by the responsible party shall be used with the device. The use of a permanently attached antenna...

47 CFR 73.1680 - Emergency antennas.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 4 2014-10-01 2014-10-01 false Emergency antennas. 73.1680 Section 73.1680... Rules Applicable to All Broadcast Stations § 73.1680 Emergency antennas. (a) An emergency antenna is one that is erected for temporary use after the authorized main and auxiliary antennas are damaged and...

47 CFR 73.1680 - Emergency antennas.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 4 2012-10-01 2012-10-01 false Emergency antennas. 73.1680 Section 73.1680... Rules Applicable to All Broadcast Stations § 73.1680 Emergency antennas. (a) An emergency antenna is one that is erected for temporary use after the authorized main and auxiliary antennas are damaged and...

47 CFR 15.203 - Antenna requirement.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 1 2010-10-01 2010-10-01 false Antenna requirement. 15.203 Section 15.203... Antenna requirement. An intentional radiator shall be designed to ensure that no antenna other than that furnished by the responsible party shall be used with the device. The use of a permanently attached antenna...

47 CFR 73.1680 - Emergency antennas.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 4 2010-10-01 2010-10-01 false Emergency antennas. 73.1680 Section 73.1680... Rules Applicable to All Broadcast Stations § 73.1680 Emergency antennas. (a) An emergency antenna is one that is erected for temporary use after the authorized main and auxiliary antennas are damaged and...

Design of Vivaldi Microstrip Antenna for Ultra-Wideband Radar Applications

NASA Astrophysics Data System (ADS)

Perdana, M. Y.; Hariyadi, T.; Wahyu, Y.

2017-03-01

The development of radar technology has an important role in several fields such as aviation, civil engineering, geology, and medicine. One of the essential components of the radar system is the antenna. The bandwidth can specify the resolution of the radar. The wider the bandwidth, the higher the resolution of radar. For Ground penetrating radar (GPR) or medical applications need with a high-resolution radar so it needs an antenna with a wide bandwidth. In addition, for the radar application is required antenna with directional radiation pattern. So, we need an antenna with wide bandwidth and directional radiation pattern. One of antenna that has meet with these characteristics is vivaldi antenna. In previous research, has designed several vivaldi microstrip antenna for ultra-wideband radar applications which has a working frequency of 3.1 to 10.7 GHz. However, these studies there is still a shortage of one of them is the radiation pattern from lowest to highest frequency radiation pattern is not uniform in the sense that not all directional. Besides the antenna material used is also not easily available and the price is not cheap. This paper will discuss the design of a vivaldi microstrip antenna which has a wide bandwidth with directional radiation pattern works on 3.1 to 10.7 GHz and using cheaper substrate. Substrates used for vivaldi microstrip antenna vivaldi is FR4 with a dielectric constant of 4.3 and a thickness of 1.6 mm. Based on the simulation results we obtained that the antenna design has frequency range 3.1-10.7 GHz for return loss less than -10 dB with a directional radiation pattern. This antenna gain is 4.8 to 8 dBi with the largest dimension is 50 mm x 40 mm.

Initial development of high-accuracy CFRP panel for DATE5 antenna

NASA Astrophysics Data System (ADS)

Qian, Yuan; Lou, Zheng; Hao, Xufeng; Zhu, Jing; Cheng, Jingquan; Wang, Hairen; Zuo, Yingxi; Yang, Ji

2016-07-01

DATE5 antenna, which is a 5m telescope for terahertz exploration, will be sited at Dome A, Antarctica. It is necessary to keep high surface accuracy of the primary reflector panels so that high observing efficiency can be achieved. In antenna field, carbon fiber reinforced composite (CFRP) sandwich panels are widely used as these panels are light in weight, high in strength, low in thermal expansion, and cheap in mass fabrication. In DATE5 project, CFRP panels are important panel candidates. In the design study phase, a CFRP prototype panel of 1-meter size is initially developed for the verification purpose. This paper introduces the material arrangement in the sandwich panel, measured performance of this testing sandwich structure samples, and together with the panel forming process. For anti-icing in the South Pole region, a special CFRP heating film is embedded in the front skin of sandwich panel. The properties of some types of basic building materials are tested. Base on the results, the deformation of prototype panel with different sandwich structures and skin layers are simulated and a best structural concept is selected. The panel mold used is a high accuracy one with a surface rms error of 1.4 μm. Prototype panels are replicated from the mold. Room temperature curing resin is used to reduce the thermal deformation in the resin transfer process. In the curing, vacuum negative pressure technology is also used to increase the volume content of carbon fiber. After the measurement of the three coordinate measure machine (CMM), a prototype CFRP panel of 5.1 μm rms surface error is developed initially.

Integration of Directional Antennas in an RSS Fingerprinting-Based Indoor Localization System

PubMed Central

Guzmán-Quirós, Raúl; Martínez-Sala, Alejandro; Gómez-Tornero, José Luis; García-Haro, Joan

2015-01-01

In this paper, the integration of directional antennas in a room-level received signal strength (RSS) fingerprinting-based indoor localization system (ILS) is studied. The sensor reader (SR), which is in charge of capturing the RSS to infer the tag position, can be attached to an omnidirectional or directional antenna. Unlike commonly-employed omnidirectional antennas, directional antennas can receive a stronger signal from the direction in which they are pointed, resulting in a different RSS distributions in space and, hence, more distinguishable fingerprints. A simulation tool and a system management software have been also developed to control the system and assist the initial antenna deployment, reducing time-consuming costs. A prototype was mounted in a real scenario, with a number of SRs with omnidirectional and directional antennas properly positioned. Different antenna configurations have been studied, evidencing a promising capability of directional antennas to enhance the performance of RSS fingerprinting-based ILS, reducing the number of required SRs and also increasing the localization success. PMID:26703620

Transition-edge superconducting antenna-coupled bolometer

NASA Astrophysics Data System (ADS)

Hunt, Cynthia L.

2004-10-01

The temperature anisotropy of the cosmic microwave background (CMB) is now being probed with unprecedented accuracy and sky coverage by the Wilkinson Microwave Anisotropy Probe (WMAP), and will be definitively mapped by the Planck Surveyor after its launch in 2007. However, the polarization of the CMB will not be mapped with sufficient accuracy. In particular, the measurement of the curl-polarization, which may be used to probe the energy scale of the inflationary epoch, requires a large advance in the format of millimeter-wave bolometer arrays. SAMBA (Superconducting Antenna-coupled Multi-frequency Bolometric Array) is being developed to address these needs for the next generation of submillimeter astronomical detectors. SAMBA consists of a focal plane populated with microstrip-coupled slot antennas, whose signals are coherently added and sent to transition-edge superconducting (TES) bolometers via microstrip lines. SAMBA eliminates the need for the feedhorns and optical filters currently used on CMB observational instruments, such as Planck and Boomerang. The SAMBA architecture allows for a high density of pixels in the focal plane with minimal sub-Kelvin mass. As a precursor to a full monolithic high-density antenna array, we are developing a single-band antenna-coupled Bolometric detector. In this thesis, I report test results for a single-pixel antenna-coupled Bolometric detector. Our device consists of a dual slot microstrip-coupled slot antenna coupled to an Al/Ti/Au voltage-biased TES. The coupling architecture involves propagating the signal along super conducting microstrip lines and terminating the lines at a normal metal resistor collocated with a TES on a thermally isolated island. The device, which is inherently polarization sensitive, is optimized for 140 GHz measurements. In the thermal bandwidth of the TES, we measure a noise equivalent power (NEP) of 2.0 x 10 -17 W/[Special characters omitted.] in dark tests which agrees with the calculated NEP

35 GHz integrated circuit rectifying antenna with 33 percent efficiency

NASA Technical Reports Server (NTRS)

Yoo, T.-W.; Chang, K.

1991-01-01

A 35 GHz integrated circuit rectifying antenna (rectenna) has been developed using a microstrip dipole antenna and beam-lead mixer diode. Greater than 33 percent conversion efficiency has been achieved. The circuit should have applications in microwave/millimeter-wave power transmission and detection.

JPL Large Advanced Antenna Station Array Study

NASA Technical Reports Server (NTRS)

1978-01-01

In accordance with study requirements, two antennas are described: a 30 meter standard antenna and a 34 meter modified antenna, along with a candidate array configuration for each. Modified antenna trade analyses are summarized, risks analyzed, costs presented, and a final antenna array configuration recommendation made.

Negative ion source with external RF antenna

DOEpatents

Leung, Ka-Ngo; Hahto, Sami K.; Hahto, Sari T.

2007-02-13

A radio frequency (RF) driven plasma ion source has an external RF antenna, i.e. the RF antenna is positioned outside the plasma generating chamber rather than inside. The RF antenna is typically formed of a small diameter metal tube coated with an insulator. An external RF antenna assembly is used to mount the external RF antenna to the ion source. The RF antenna tubing is wound around the external RF antenna assembly to form a coil. The external RF antenna assembly is formed of a material, e.g. quartz, which is essentially transparent to the RF waves. The external RF antenna assembly is attached to and forms a part of the plasma source chamber so that the RF waves emitted by the RF antenna enter into the inside of the plasma chamber and ionize a gas contained therein. The plasma ion source is typically a multi-cusp ion source. A converter can be included in the ion source to produce negative ions.

Microelectromechanical Systems Actuator Based Reconfigurable Printed Antenna

NASA Technical Reports Server (NTRS)

Simons, Rainee N. (Inventor)

2005-01-01

A polarization reconfigurable patch antenna is disclosed. The antenna includes a feed element, a patch antenna element electrically connected to the feed element, and at least one microelectromechanical systems (MEMS) actuator, with a partial connection to the patch antenna element along an edge of the patch antenna element. The polarization of the antenna can be switched between circular polarization and linear polarization through action of the at least one MEMS actuator.

47 CFR 73.1675 - Auxiliary antennas.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 4 2012-10-01 2012-10-01 false Auxiliary antennas. 73.1675 Section 73.1675... Rules Applicable to All Broadcast Stations § 73.1675 Auxiliary antennas. (a)(1) An auxiliary antenna is one that is permanently installed and available for use when the main antenna is out of service for...

47 CFR 73.1675 - Auxiliary antennas.

Code of Federal Regulations, 2011 CFR

2011-10-01