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Results for “receiver optimization”

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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

Design for On-Sun Evaluation of Evaporator Receivers

A heat pipe designed for operation as a solar power receiver should be optimized to accept the solar energy flux and transfer this heat into a reactor. Optical properties of the surface, thermal conductance of the receiver wall, contact resistance of the heat pipe wick, and other heat pipe wick properties ultimately define the maximum amount of power that can be extracted from the concentrated sunlight impinging on the evaporator surface. Modeling of solar power receivers utilizing optical and physical properties provides guidance to their design. On-sun testing is another important means of gathering information on performance. A test rig is being designed and built to conduct on-sun testing. The test rig is incorporating a composite strip mirror concentrator developed as part of a Small Business Innovative Research effort and delivered to NASA Glenn Research Center. In the strip concentrator numerous, lightweight composite parabolic strips of simple curvature were combined to form an array 1.5 m x 1.5 m in size. The line focus of each strip is superimposed in a central area simulating a point of focus. A test stand is currently being developed to hold the parabolic strip concentrator, track the sun, and turn the beam downward towards the ground. The hardware is intended to be sufficiently versatile to accommodate on-sun testing of several receiver concepts, including those incorporating heat pipe evaporators. Characterization devices are also being developed to evaluate the effectiveness of the solar concentrator, including a receiver designed to conduct calorimetry. This paper describes the design and the characterization devices of the on-sun test rig, and the prospect of coupling the concentrated sunlight to a heat pipe solar power receiver developed as part of another Small Business Innovative Research effort.

Jaworske, Donald A.↗
NASA NTRS1982

Optimization of Dish Solar Collectors with and without Secondary Concentrators

Methods for optimizing parabolic dish solar collectors and the consequent effects of various optical, thermal, mechanical, and cost variables are examined. The most important performance optimization is adjusting the receiver aperture to maximize collector efficiency. Other parameters that can be adjusted to optimize efficiency include focal length, and, if a heat engine is used, the receiver temperature. The efficiency maxima associated with focal length and receiver temperature are relatively broad; it may, accordingly, be desirable to design somewhat away from the maxima. Performance optimization is sensitive to the slope and specularity errors of the concentrator. Other optical and thermal variables affecting optimization are the reflectance and blocking factor of the concentrator, the absorptance and losses of the receiver, and, if a heat engine is used, the shape of the engine efficiency versus temperature curve. Performance may sometimes be improved by use of an additional optical element (a secondary concentrator) or a receiver window if the errors of the primary concentrator are large or the receiver temperature is high.

Jaffe, L. D.↗
NASA NTRS1983

Optimization of dish solar collectors

Methods for optimizing parabolic dish solar collectors and the consequent effects of various optical, thermal, mechanical, and cost variables are examined. The most important performance optimization is adjusting the receiver aperture to maximize collector efficiency. Other parameters that can be adjusted to optimize efficiency include focal length, and, if a heat engine is used, the receiver temperature. The efficiency maxima associated with focal length and receiver temperature are relatively broad; it may, accordingly, be desirable to design somewhat away from the maxima. Performance optimization is sensitive to the slope and specularity errors of the concentrator. Other optical and thermal variables affecting optimization are the reflectance and blocking factor of the concentrator, the absorptance and losses of the receiver, and, if a heat engine is used, the shape of the engine efficiency versus temperature curve. Performance may sometimes be improved by use of an additional optical element (a secondary concentrator) or a receiver window if the errors of the primary concentrator are large or the receiver temperature is high. Previously announced in STAR as N83-19224

Jaffe, L. D.↗
NASA NTRS1985

Design and optimization of NbCN/PbBi mixer elements for heterodyne receivers

Superconductor-Insulator-Superconductor (SIS) quantum mixers provide a relatively new approach to millimeter wave mixing potentially offering conversion gain, a low local oscillator power demand and potential mixer temperatures near the quantum limit. This paper presents device modeling and fabrication development for NbCN lead-alloy submicron edge-contact SIS mixers for use at 115 GHz.

Lichtenberger, A. W.↗
NASA NTRS1983

Capabilities and limitations of EISCAT as an MST radar

The European Incoherent Scatter Radar Facility also has facilities which can be used for coherent scatter research of the middle atmosphere. The observatory consists of two independent systems which allow observations of the upper, middle, and lower atmosphere: a tristatic UHF radar capable of vector drift measurements, and a monostatic VHF system. The characteristics of the components are are described including inter-site communication, on-line displays, and the real-time operating system. Analysis of about 60 hours of middle atmosphere observations in 1982 indicate that EISCAT's capabilities to measure mesospheric parameters should improve during moderately or strongly disturbed conditions, enabling measurement of profiles of wind velocity, electron density, and temperature/collision frequency, and in some instances, ion masses. Because of not yet optimized transmit-receive switching, some limitations exist in the monostatic mode when observing coherent scattering in the stratosphere at short ranges.

Rottger, J.↗
NASA NTRS1984

Performance test results of a low cost GPS time and frequency monitor

Final prototype and pilot production performance test results was presented on a single channel C/A code GPS receiver that was optimized for time and frequency applications. Timing accuracy and stability test results are presented, as well as position determination results. Timing accuracy, timing stability, frequency stability, position accuracy and position stability are presented in the results.

Hyatt, R. C.↗
NASA NTRS2016

A FDTD Solution of Scattering of Laser Beam with Orbital Angular Momentum by Dielectric Particles: Far-Field Characteristics

Electromagnetic (EM) beams with orbital angular momentum (OAM) may have great potential applications in communication technology and in remote sensing of the Earth-atmosphere system and outer planets. Study of their interaction with optical lenses and dielectric or metallic objects, or scattering of them by particles in the Earth-atmosphere system, is a necessary step to explore the advantage of the OAM EM beams. In this study, the 3-dimensional (3D) scattered-field (SF) finite-difference time domain (FDTD) technique with the convolutional perfectly matched layer (CPML) absorbing boundary conditions (ABC) is applied to calculate the scattering of the purely azimuthal (the radial mode number is assumed to be zero) Laguerre–Gaussian (LG) beams with the OAM by dielectric particles. We found that for OAM beam׳s interaction with dielectric particles, the forward-scattering peak in the conventional phase function (P11) disappears, and light scattering peak occurs at a scattering angle of ~15° to 45°. The disappearance of forward-scattering peak means that, in laser communications most of the particle-scattered noise cannot enter the receiver, thus the received light is optimally the original OAM-encoded signal. This feature of the OAM beam also implies that in lidar remote sensing of the atmospheric particulates, most of the multiple-scattering energy will be off lidar sensors, and this may result in an accurate profiling of particle layers in the atmosphere or in the oceans by lidar, or even in the ground when a ground penetration radar (GPR) with the OAM is applied. This far-field characteristics of the scattered OAM light also imply that the optical theorem, which is derived from plane-parallel wave scattering case and relates the forward scattering amplitude to the total cross section of the scatterer, is invalid for the scattering of OAM beams by dielectric particles.

Electromagnetic beams↗
NASA NTRS2018

Optical and Mechanical Designs of the Multi-band SWIR Receiver for the Lunar Flashlight CubeSat Mission

Mapping and quantifying lunar water ice addresses one of NASA’s Strategic Knowledge Gaps to understand the lunar resource potential for future human exploration of the Moon. Lunar Flashlight is an innovative NASA CubeSat mission dedicated to mapping water ice in the permanently-shadowed and occasionally-sunlit regions in the vicinity of the lunar South Pole. Lunar Flashlight will acquire these measurements from lunar orbit using a multi-band laser reflectometer composed of an optical receiver aligned with four lasers emitting different wavelengths in the shortwave infrared spectral region between 1 µm and 2 µm. The receiver measures the laser radiance reflected from the lunar surface in each spectral band and continuum/absorption reflectance band ratios are then analyzed to quantify water ice concentration in the illuminated spot. The receiver utilizes a 70×70-mm, aluminum, off-axis paraboloidal mirror with a focal length of 70 mm, which collects the incoming light onto a single, 2 mm diameter InGaAs detector with a cutoff wavelength of 2.4 µm. We present the optical and mechanical designs of the receiver, including its optimization for rejection of solar stray-light from outside its intended field of view. This highly mass- and volume-constrained instrument payload will demonstrate several firsts, including being one of the first instruments onboard a CubeSat performing science measurements beyond low Earth orbit and the first planetary mission to use multi-band active reflectometry from orbit.

Sellar, R. Glenn↗
NASA NTRS1989

Impact of random pointing and tracking errors on the design of coherent and incoherent optical intersatellite communication links

Given the rms transmitter pointing error and the desired probability of bit error (PBE), it can be shown that an optimal transmitter antenna gain exists which minimizes the required transmitter power. Given the rms local oscillator tracking error, an optimum receiver antenna gain can be found which optimizes the receiver performance. The impact of pointing and tracking errors on the design of direct-detection pulse-position modulation (PPM) and heterodyne noncoherent frequency-shift keying (NCFSK) systems are then analyzed in terms of constraints on the antenna size and the power penalty incurred. It is shown that in the limit of large spatial tracking errors, the advantage in receiver sensitivity for the heterodyne system is quickly offset by the smaller antenna gain and the higher power penalty due to tracking errors. In contrast, for systems with small spatial tracking errors, the heterodyne system is superior because of the higher receiver sensitivity.

Chen, Chien-Chung↗
NASA NTRS2019

Vortex Radiometry: Fundamental Concepts

Vortex radiometers (VRs) enable communication systems to maximize data throughput by determining when to employ fade mitigation most efficiently. With this information, communication systems can optimize mitigation strategies before actual fades occur. Doing so maximizes the time over which the link is available, and therefore maximizes data throughput. This paper presents the fundamental concepts of vortex radiometry, including the creation of annular beam patterns through the use of orbital angular momentum (OAM). These concepts are simulated on a 100 Mbps (Megabits per second) GEO (Geosynchrous Earth Orbit)-to-ground Ka-Band communication link. During the simulation a noise source traverses across the link, and without VR capabilities the link is disrupted. However, when the situation is repeated with VR capabilities enabled, the antenna is able to increase receiver gain and maintain the link. VRs are uniquely suited to provide communication systems with the ability to optimize receiver parameters and maximize data throughput, making them critical to enabling next generation communication networks.

Orbital Angular Momentum↗
NASA NTRS1987

Optimized tracking of RF carriers with phase noise, including Pioneer 10 results

The ability to track very weak signals from distant spacecraft is limited by the phase instabilities of the received signal and of the local oscillator employed by the receiver. These instabilities ultimately limit the minimum loop bandwidth that can be used in a phase-coherent receiver, and hence limit the ratio of received carrier power to noise spectral density which can be tracked phase coherently. A method is presented for near real time estimation of the received carrier phase and additive noise spectrum, and optimization of the phase locked loop bandwidth. The method was used with the breadboard Deep Space Network (DSN) Advanced Receiver to optimize tracking of very weak signals from the Pioneer 10 spacecraft, which is now more distant that the edge of the solar system. Tracking with bandwidths of 0.1 Hz to 1.0 Hz reduces tracking signal threshold and increases carrier loop signal to noise ratio (SNR) by 5 dB to 15 dB compared to the 3 Hz bandwidth of the receivers now used operationally in the DSN. This will enable the DSN to track Pioneer 10 until its power sources fails near the end of the century.

Vilnrotter, V. A.↗
NASA NTRS1988

Optimal polarizations for achieving maximum contrast in radar images

A systematic approach is presented for obtaining the optimal polarimetric matched filter, which produces maximum contrast between two scattering classes in polarimetric radar images. The maximization procedure involves solving an eigenvalue problem when the eigenvector corresponding to the maximum contrast ratio is optimal polarimetric matched filter. It is shown how to realize the filter in terms of an equivalent transmitting and receiving polarization pair. The case where the radar transmitting polarization state is fixed is addressed. Here, the receiving polarization state is optimized so that the maximum constrast ratio is attained under this constraint.

Swartz, A. A.↗
NASA NTRS1992

Novel multireceiver communication systems configurations based on optimal estimation theory

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

Kumar, Rajendra↗
DOE OSTI2022

Power system load flexibility forecasting

The example embodiments are directed to a system and method for forecasting load flexibility of a power grid. In one example, the method includes receiving temperature values associated with temperature set points of a plurality of loads that are included on a power grid, forecasting a flexibility of the plurality of loads using a polynomial-time mixed-integer non-linear programming (MINLP) optimization based on the received temperature values for the plurality of loads, and outputting information about the forecasted flexibility for display to a display device. The MINLP optimization performs the forecasting of the load flexibility on a fine-grained basis in comparison to conventional methods and is still fast enough that it can be computed in real-time.

Genc, Sahika↗
NASA NTRS1991

A receiver design for the superconducting cavity-maser oscillator

A new frequency standard was demonstrated with the aid of a double phase locked loop (PLL) receiver. A superconducting cavity maser oscillator (SCMO) and a hydrogen maser are combined to show the medium term performance of the hydrogen maser together with improved short term performance made possible by the SCMO. The receiver, which generates a 100 MHz signal with reduced noise, is phase locked to (and may be used in place of) the 100 MHz hydrogen maser output. The maser signal, 2.69xxx-GHz SCMO output, and a 100 MHz quartz crystal oscillator are optimally combined by the receiver. A measured two source fractional frequency stability of 2 x 10(exp -14) was obtained for a measuring time of r = 1 sec, and 1 x 10(exp -15) at r = 1,000 sec. The 1 sec value is approx. 10 times lower than that for hydrogen masers, while the 1,000 sec value is identical to hydrogen maser performance. The design is based on phase noise models for the hydrogen maser, the SCMO, and quartz crystal oscillators for offset frequencies down to 1 x 10(exp -6) Hz.

Wang, R. T.↗
DOE OSTI2023

Evaluation of Additively Manufactured Monolithic SiC and SiC Ceramic Matrix Composites for CSP- Fabrication and Testing of Receiver Design Feature Specimens in a Simulating Lab Test via Laser Heating

Critical to the creation of a multi-component SiC receiver design concept capable of meeting the SETO CST cost goal objectives of <$150/kWth is the optimal utilization of material for solar absorption and heat transfer to transport fluid. This is to maximize the solar-thermal efficiency in the techno-economic analysis of derived use case. As a first step in preparation of sub-component design for on-sun test evaluations we use different proposed SiC absorber element in a customized laser heat flux test to assess an effective heat transfer coefficient characteristic of the design. The test results are analyzed to extract the effective heat transfer coefficient, thus enable optimization of the geometry of receiver components for heat transfer, efficiency attributes and the thermo-structural management of the components. High intensity CO2 laser is used in combination with air flow through the test specimen to assess the effective heat transfer coefficient under heat flux conditions corresponding to high solar concentrations in the range of 1000-2000 suns.

14 SOLAR ENERGY↗