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Results for “polarization switching”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

Switched-Polarization Birefringent Optical Delay Lines

Controllable birefringent optical delay lines proposed for use in photonically controlling phases of signals in radiating elements of phased-array antennas. Features low optical insertion losses and made very compact, enabling high packing densities where multiple delay channels needed. Polarization switched in segments to adjust overall delay. Furthermore, two or more delay lines cascaded increases delay-adjustment range.

Yao, Xiaotian Steve↗
NASA NTRS1988

Bistable polarization switching in a continuous wave ruby laser

Bistability in the output power, polarization state, and mode volume of an argon-ion laser pumped single mode ruby laser at 6943 A has been observed. The laser operates in a radially confined mode which exhibits hysteresis and bistability only when the pump polarization is parallel to the c-axis.

Lawandy, N. M.↗
NASA NTRS1988

A digital beacon receiver

A digital satellite beacon receiver is described which provides measurement information down to a carrier/noise density ratio approximately 15 dB below that required by a conventional (phase locked loop) design. When the beacon signal fades, accuracy degrades gracefully, and is restored immediately (without hysteresis) on signal recovery, even if the signal has faded into the noise. Benefits of the digital processing approach used include the minimization of operator adjustments, stability of the phase measuring circuits with time, repeatability between units, and compatibility with equipment not specifically designed for propagation measuring. The receiver has been developed for the European Olympus satellite which has continuous wave (CW) beacons at 12.5 and 29.7 GHz, and a switched polarization beacon at 19.8 GHz approximately, but the system can be reconfigured for CW and polarization-switched beacons at other frequencies.

Ransome, Peter D.↗
NASA NTRS2002

Microelectromechanical Systems (MEMS) Actuator-Based, Polarization Reconfigurable Patch Antenna Demonstrated

A nearly square patch antenna with a contact actuator along a radiating edge for polarization reconfiguration was demonstrated at Ka-band frequencies at the NASA Glenn Research Center. The layout of the antenna is shown in the following sketch. This antenna has the following advantages: 1) It can be dynamically reconfigured to receive and transmit a linearly polarized signal or a circularly polarized signal. This feature allows the substitution of multiple antennas on a satellite by a single antenna, thereby resulting in significant cost savings. 2) In our approach, the polarization is switched between the two states without affecting the frequency of operation; thus, valuable frequency spectrum is conserved. 3) The ability to switch polarization also helps mitigate propagation effects due to adverse weather on the performance of a satellite-to-ground link. Hence, polarization reconfigurability enhances link reliability.

Simons, Rainee N.↗
NASA NTRS1984

S band radar differential reflectivity measurements in multiple polarization planes along satellite slant paths

A novel approach to making differential reflectivity measurements in multiple polarization planes has been proposed. This paper describes a versatile technique using a mechanical polarization switch and the systematic errors in differential reflectivity measurements which result. Initial results of simultaneous X band slant path measurements of attenuation and depolarization at 11.6 GHz and differential reflectivity measurements at 2.8 GHz using a slow polarization switch are presented.

Marshall, R. E.↗
NASA NTRS1978

Chopper-stabilized phase detector

Phase-detector circuit for binary-tracking loops and other binary-data acquisition systems minimizes effects of drift, gain imbalance, and voltage offset in detector circuitry. Input signal passes simultaneously through two channels where it is mixed with early and late codes that are alternately switched between channels. Code switching is synchronized with polarity switching of detector output of each channel so that each channel uses each detector for half time. Net result is that dc offset errors are canceled, and effect of gain imbalance is simply change in sensitivity.

Hopkins, P. M.↗
NASA NTRS1994

Automated System Tests Ferroelectric Capacitors

Polarization-switching parameters measured under computer control. Ferroelectric-capacitor-testing system applies voltage pulses and measures responses of ferroelectric capacitor to determine write; "time dependence of polarization," polarization-retention and fatigue characteristics of capacitor. Highly integrated setup quite flexible, versatile, and interactive, and allows convenient computer storage and analysis of data.

Lakata, Mark↗
NASA NTRS2012

Scientific Verification of Faraday Rotation Modulators: Detection of Diffuse Polarized Galactic Emission

The design and performance of a wide bandwidth linear polarization-modulator based on the Faraday effect is described. Faraday Rotation Modulators (FRMs) are solid-state polarization switches that are capable of modulation up to approx 10 kHz. Six FRMs were utilized during the 2006 observing season in the Background Imaging of Cosmic Extragalactic Polarization (BICEP) experiment; three FRMs were used at each of BICEP fs 100 and 150 GHz frequency bands. The technology was verified through high signal-to-noise detection of Galactic polarization using two of the six FRMs during four observing runs in 2006. The features exhibit strong agreement with BICEP fs measurements of the Galaxy using non-FRM pixels and with the Galactic polarization models. This marks the first detection of high signal-to-noise mm-wave celestial polarization using fast, active optical modulation. The performance of the FRMs during periods when they were not modulated was also analyzed and compared to results from BICEP fs 43 pixels without FRMs.

Moyerman, S.↗
NASA NTRS1976

The high-power X-band planetary radar at Goldstone - Design, development, and early results

Selected critical microwave components for a 400-kW very-long-pulse (several hours) X-band radar system are discussed from theoretical and practical viewpoints. Included are the special-sized waveguide and flanges, hybrid power combiner, couplers, switches, polarizer, rotary joints, feedhorn, and radome. The system is installed on the National Aeronautics and Space Administration/Jet Propulsion Laboratory 64-m-diam reflector antenna at Goldstone, CA.

Hartop, R.↗
NASA NTRS1994

Optically Addressable, Ferroelectric Memory With NDRO

For readout, memory cells addressed via on-chip semiconductor lasers. Proposed thin-film ferroelectric memory device features nonvolatile storage, optically addressable, nondestructive readout (NDRO) with fast access, and low vulnerability to damage by ionizing radiation. Polarization switched during recording and erasure, but not during readout. As result, readout would not destroy contents of memory, and operating life in specific "read-intensive" applications increased up to estimated 10 to the 16th power cycles.

Thakoor, Sarita↗
NASA NTRS1996

Ladderlike Switched-Path Optical Delay Lines

Switched-path adjustable optical delay lines with ladderlike configurations proposed for use in photonically controlling phases of radio signals in radiating elements of phased-array antennas and in adaptive filtering of signals. Lines relatively simple, compact, easy to fabricate, and inexpensive. Switchable delay blocks stacked like building blocks to form incrementally adjustable delay lines. Delay lines also stacked to form high-density multiple-channel delay systems. To reduce number of blocks, heights of blocks increased successively by factor of 2, similar to crystal arrangement described in article "Switched-Polarization Birefringent Optical Delay Lines" (NPO-19412).

Yao, Xiaotian Steve↗
NASA NTRS1997

Laser-Induced Damage Threshold and Certification Procedures for Optical Materials

This document provides instructions for performing laser-induced-damage-threshold tests and pass-fail certification tests on optical materials used in pulsed-laser systems. The optical materials to which these procedures apply include coated and uncoated optical substrates, laser crystals, Q-switches, polarizers, and other optical components employed in pulsed-laser systems.

Source record↗
NASA NTRS2001

A Model for Rate-Dependent Hysteresis in Piezoceramic Materials Operating at Low Frequencies

This paper addresses the modeling of certain rate-dependent mechanisms which contribute to hysteresis inherent to piezoelectric materials operating at low frequencies. While quasistatic models are suitable for initial material characterization in some applications, the reduction in coercive field and polarization values which occur as frequencies increase must be accommodated to achieve the full capabilities of the materials. The model employed here quantifies the hysteresis in two steps. In the first, anhysteretic polarization switching is modeled through the application of Boltzmann principles to balance the electrostatic and thermal energy. Hysteresis is then incorporated through the quantification of energy required to translate and bend domain walls pinned at inclusions inherent to the materials. The performance of the model is illustrated through a fit to low frequency data (0.1 Hz - 1 Hz) from a PZT5A wafer.

Smith, Ralph C.↗
NASA NTRS2004

T/R module development for large aperture L-band phased array

This paper describes a transmit / receive (T/R) module for a large L-band space based radar active phased array being developed at JPL. Electrical performance and construction techniques are described, with emphasis on the former. The T/R modules have a bandwidth of more than 80 MHz centered at 1260MHz and support dual, switched polarizations. Phase and amplitude are controlled by a 6-bit phase shifter and a 6-bit attenuator, respectively. The transmitter power amplifier generates 2.4 W into a nominal 50 ohm load with 36% overall efficiency. The receiver noise figure is 4.4 dB including all front-end losses. The module weighs 32 g and has a footprint of 8 cm x 4.5 cm. Fourteen of these T/R modules were fabricated at the JPL Pick-and-Place Facility and were tested using a computer-controlled measurement facility developed at JPL. Calibrated performance of this set of T/R modules is presented and shows good agreement with design predictions.

transmit / receive (T/R) module↗
NASA NTRS2004

Spatial light modulators for full cross-connections in optical networks

A polarization-independent optical switch is disclosed for switching at least one incoming beam from at least one input source to at least one output drain. The switch includes a polarizing beam splitter to split each of the at least one incoming beam into a first input beam and a second input beam, wherein the first input beam and the second input beams are independently polarized; a wave plate optically coupled to the second input beam for converting the polarization of the second input beam to an appropriately polarized second input beam; a beam combiner optically coupled to the first input beam and the modified second input beam, wherein the beam combiner accepts the first input beam and the modified second input beam to produce a combined beam; the combined beam is invariant to the polarization state of the input source's polarization; and a controllable spatial light modulator optically coupled to the combined beam, wherein the combined beam is diffracted by the controllable spatial light modulator to place light at a plurality of output locations.

Juday, Richard D.↗
NASA NTRS1992

Method and circuit for controlling the evolution time interval of a laser output pulse

The invention is a method and circuit for controlling the evolution time interval of a laser output pulse used for making precise spectral measurements. It comprises the means for pumping a laser medium in a resonator that includes a Q-switch and polarizer that act in combination to control the loss in the resonator. A photodiode senses the resulting fluorescence which is applied to a two level Q-switch and polarizer from high to intermediate to substantially zero loss states to control the evolution time interval of the resulting laser output pulse.

Barnes, Norman P.↗
NASA NTRS2016

Solar Activity Studies using Microwave Imaging Observations

We report on the status of solar cycle 24 based on polar prominence eruptions (PEs) and microwave brightness enhancement (MBE) information obtained by the Nobeyama radioheliograph. The north polar region of the Sun had near-zero field strength for more than three years (2012-2015) and ended only in September 2015 as indicated by the presence of polar PEs and the lack of MBE. The zero-polar-field condition in the south started only around 2013, but it ended by June 2014. Thus the asymmetry in the times of polarity reversal switched between cycle 23 and 24. The polar MBE is a good proxy for the polar magnetic field strength as indicated by the high degree of correlation between the two. The cross-correlation between the high- and low-latitude MBEs is significant for a lag of approximately 5.5 to 7.3 years, suggesting that the polar field of one cycle indicates the sunspot number of the next cycle in agreement with the Babcock-Leighton mechanism of solar cycles. The extended period of near-zero field in the north-polar region should result in a weak and delayed sunspot activity in the northern hemisphere in cycle 25.

microwave radio emission↗