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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 NTRS2014

Aerogel Antennas Communications Study Using Error Vector Magnitude Measurements

This paper discusses an aerogel antennas communication study using error vector magnitude (EVM) measurements. The study was performed using 4x2 element polyimide (PI) aerogel-based phased arrays designed for operation at 5 GHz as transmit (Tx) and receive (Rx) antennas separated by a line of sight (LOS) distance of 8.5 meters. The results of the EVM measurements demonstrate that polyimide aerogel antennas work appropriately to support digital communication links with typically used modulation schemes such as QPSK and pi/4 DQPSK. As such, PI aerogel antennas with higher gain, larger bandwidth and lower mass than typically used microwave laminates could be suitable to enable aerospace-to-ground communication links with enough channel capacity to support voice, data and video links from cubesats, unmanned air vehicles (UAV), and commercial aircraft.

Aerogel Antennas↗
NASA NTRS2014

Aerogel Antennas Communications Study Using Error Vector Magnitude Measurements

This presentation discusses an aerogel antennas communication study using error vector magnitude (EVM) measurements. The study was performed using 2x4 element polyimide (PI) aerogel-based phased arrays designed for operation at 5 GHz as transmit (Tx) and receive (Rx) antennas separated by a line of sight (LOS) distance of 8.5 meters. The results of the EVM measurements demonstrate that polyimide aerogel antennas work appropriately to support digital communication links with typically used modulation schemes such as QPSK and 4 DQPSK. As such, PI aerogel antennas with higher gain, larger bandwidth and lower mass than typically used microwave laminates could be suitable to enable aerospace-to- ground communication links with enough channel capacity to support voice, data and video links from CubeSats, unmanned air vehicles (UAV), and commercial aircraft.

Polyimide Aerogel↗
NASA NTRS2016

Measurement of Error Vector Magnitude (EVM) to Characterize the Impairment of the Tracking and Data Relay Satellite (TDRS) Channel

A digital signal is transmitted via a carrier wave, it demodulates at a receiver, and locates at an ideal constellation point. However, noise distortion, carrier leakage, and phase noise can force a signal to divert from its ideal position to a new position. Consequently, the performance of the signal is decreased. Bit Error Rate (BER) and Error Vector Magnitude (EVM) measurement techniques are used to enable the analysis and assessment of the extent to which the performance of a signal has been decreased. In this paper, we present the EVM measurement technique as a figure of merit to analyze and evaluate the performance of a User Services Subsystem Component Replacement (USSCR) modem. Also, we demonstrate the use of the EVM measurement technique in a Tracking and Data Relay Satellite (TDRS) system to measure and evaluate channel impairment between a satellite (transmitter) and the ground terminal (receiver) at the White Sands Complex.

Spacecraft RF Communications↗
NASA NTRS2011

Spaceflight Ka-Band High-Rate Radiation-Hard Modulator

A document discusses the creation of a Ka-band modulator developed specifically for the NASA/GSFC Solar Dynamics Observatory (SDO). This flight design consists of a high-bandwidth, Quadriphase Shift Keying (QPSK) vector modulator with radiation-hardened, high-rate driver circuitry that receives I and Q channel data. The radiationhard design enables SDO fs Ka-band communications downlink system to transmit 130 Mbps (300 Msps after data encoding) of science instrument data to the ground system continuously throughout the mission fs minimum life of five years. The low error vector magnitude (EVM) of the modulator lowers the implementation loss of the transmitter in which it is used, thereby increasing the overall communication system link margin. The modulator comprises a component within the SDO transmitter, and meets the following specifications over a 0 to 40 C operational temperature range: QPSK/OQPSK modulator, 300-Msps symbol rate, 26.5-GHz center frequency, error vector magnitude less than or equal to 10 percent rms, and compliance with the NTIA (National Telecommunications and Information Administration) spectral mask.

Jaso, Jeffery M.↗
NASA NTRSDate not supplied

Amplifier Output Power, Gain, Efficiency, and Bandwidth: A Comparative Study of GaN HEMT MMIC Multi-Stage Power Amplifiers versus Distributed Power Amplifiers

In this paper we present first, the results of a study conducted to investigate the microwave performance of a wideband (25-31 GHz) GaN MMIC distributed high power amplifier (HPA). Second, we compare and contrast the above performance with that of an alternate architecture that relies on two HPAs to provide contiguous 25-31 GHz coverage. The two HPAs operate across 25-28 GHz and 27-31 GHz, respectively, and can be switched in and out depending on the need at any given time. The parameters investigated includes the output power, gain, power added efficiency, bandwidth, RMS error vector magnitude for offset-QPSK, 8PSK, 16APSK, and 32 APSK waveforms, 3rd-order intermodulation distortion products, noise figure, and single sideband phase noise.

MMIC↗
NASA NTRS2024

Spectrally Efficient GaN High-Power Amplifier for Lunar Communications

The paper demonstrates a spectrally efficient Ka-band GaN MMIC based high-power amplifier (HPA) that uses a waveguide 4-port magic-tee as a 2-way power combiner to combine the output from two lower power amplifier circuits. The paper presents for the prototype HPA the measured output power, gain, power added efficiency, error vector magnitude for Offset-QPSK, 8PSK, 16APSK, 32APSK, and 16QAM waveforms, waveform spectrum, and out-of-band spectral regrowth. The HPA is intended for establishing a direct communication link between assets on the lunar surface/orbit and Earth.

Gallium nitride↗
NASA NTRSDate not supplied

Ka-Band GaN-on-SiC MMIC Balanced High Power Amplifier for NASA's Lunar Missions

The feasibility of Ka-band GaN-on-SiC MMIC based balanced power amplifier for science data downlinks from NASA’s lunar mission assets in space is investigated. The balanced amplifier combines the RF output power from two power amplifiers using a rectangular waveguide based 3-dB hybrid coupler. The investigation includes characterizing the balanced amplifier for the overall RF output power, Gain, power added efficiency, RMS error vector magnitude for offset-QPSK, 8PSK, 16APSK, and 32APSK waveforms, 3rd order intermodulation products, and noise figure. The balanced amplifier has high output RF power and good linearity and can support high data rate downlinks from the surface and vicinity of the Moon to Earth.

Gallium Nitride↗
NASA NTRSDate not supplied

Benefits of Ka-band GaN MMIC High Power Amplifiers With Wide Bandwidth and High Spectral/Power Added Efficiencies for Cognitive Radio Platforms

A cognitive radio on a future NASA near-Earth spacecraft will be capable of sensing its environment and dynamically adapting its operating parameters to provide the desired SATCOM service to the mission. A key component that can enable this type of operation is a high-power amplifier (HPA) that resides on the radio platform. In this paper, we present the RF performance characteristics of a Ka-band gallium nitride (GaN) monolithic microwave integrated circuit (MMIC) based HPA for cognitive radio platforms. These characteristics include the output power, gain, power added efficiency (PAE), RMS error vector magnitude (EVM), spectral efficiency, 3rd-order intermodulation distortion (IMD) products, spectrum, spectral regrowth, noise figure (NF), and phase noise. The data presented indicates that the HPA meets NTIA, military, and commercial spectral mask requirements. In addition, we discuss the benefits offered by the above performance characteristics toward the design and implementation of a cognitive radio platform. Furthermore, as examples, we discuss three potential use cases that apply artificial intelligence (AI) and machine learning (ML) techniques and exploit the performance characteristics discussed above to provide a knowledge-based cognitive radio platform design for SATCOM. Thus, cognitive radios with performance flexibility can enable roaming and provide seamless interoperability autonomously in the future between NASA, commercial, and other space networks owned by U.S. government agencies.

Gallium nitride↗
NASA NTRS2023

Benefits of Ka-band GaN MMIC High Power Amplifiers With Wide Bandwidth and High Spectral/Power Added Efficiencies for Cognitive Radio Platforms

A cognitive radio on a future NASA near-Earth spacecraft will be capable of sensing its environment and dynamically adapting its operating parameters to provide the desired SATCOM service to the mission. A key component that can enable this type of operation is a high-power amplifier (HPA) that resides on the radio platform. In this report, we present the RF performance characteristics of a Ka-band gallium nitride (GaN) monolithic microwave integrated circuit (MMIC) based HPA for cognitive radio platforms. These characteristics include the output power, gain, power added efficiency (PAE), RMS error vector magnitude (EVM), spectral efficiency, 3rdorder intermodulation distortion (IMD) products, spectrum, spectral regrowth, noise figure (NF), phase noise, and group delay. The data presented indicates that the HPA meets NTIA, military, and commercial spectral mask requirements. In addition, we discuss the benefits offered by the above performance characteristics toward the design and implementation of a cognitive radio platform. Furthermore, as examples, we discuss three potential use cases that apply artificial intelligence (AI) and machine learning (ML) techniques and exploit the performance characteristics discussed above to provide a knowledge-based cognitive radio platform design for SATCOM. Thus, cognitive radios with performance flexibility can enable roaming and provide seamless interoperability autonomously in the future between NASA, commercial, and other space networks owned by U.S. government agencies.

Gallium nitride↗
NASA NTRS2008

Applying EVM to Satellite on Ground and In-Orbit Testing - Better Data in Less Time

Using Error Vector Magnitude (EVM) in satellite integration and test allows rapid verification of the Bit Error Rate (BER) performance of a satellite link and is particularly well suited to measurement of low bit rate satellite links where it can result in a major reduction in test time (about 3 weeks per satellite for the Geosynchronous Operational Environmental Satellite [GOES] satellites during ground test) and can provide diagnostic information. Empirical techniques developed to predict BER performance from EVM measurements and lessons learned about applying these techniques during GOES N, O, and P integration test and post launch testing, are discussed.

Peters, Robert↗
DOE OSTI2019

Direct digital predistortion technique for the compensation of laser chirp and fiber dispersion in long haul radio over fiber links

Analog Radio-over-Fiber (A-RoF) communication technology constitutes a promising technique for next generation radio access networks thanks to its relatively low bandwidth requirements. Within this context, an efficient predistortion technique is proposed, which can be applied to reduce the impairments of A-RoF systems due to the combined effects of frequency chirp of the laser source and chromatic dispersion of the optical channel. The radio frequency signal is firstly put in digital form through an analog to digital converter, then the predistortion operation is realized, and finally the resulting signal is put again into analog form. A comprehensive analysis on the theoretical basis of the proposed approach is presented, together with the approximations introduced, which makes it practically realizable. The improvements on the quality of the received signal due to the proposed solution are illustrated with reference to scenarios of applicative interest. The performance of proposed technique is evaluated in terms of adjacent channel leakage ratio and error vector magnitude when long term evolution signal is applied at the input.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Integrating Radio-Over-Fiber Communication System and BOTDR Sensor System

In this paper, we propose and experimentally demonstrate for the first time, the integration of a radio-over-fiber (RoF) communication system and a Brillouin optical time-domain reflectometry (BOTDR) distributed sensor system using a single optical fiber link. In this proof-of-concept integrated system, the communication system is composed of three modulation formats of quadrature phase-shift keying (QPSK), 16-quadrature amplitude modulation (16-QAM) and 64-QAM, which are modulated onto an orthogonal frequency division multiplexing (OFDM) signal. Whereas, the BOTDR sensor system is used for strain and/or temperature monitoring over the fiber distance with a spatial resolution of 5 m using a 25 km single-mode silica fiber. The error vector magnitude (EVM) is analyzed in three modulation formats in the presence of various BOTDR input pump powers. Using QPSK modulation, optimized 18 dBm sensing and 10 dBm data power, the measured EVM values with and without bandpass filter are 3.5% and 14.5%, respectively. The proposed system demonstrates a low temperature measurement error (±0.49 °C at the end of 25 km) and acceptable EVM values, which were within the 3GPP requirements. The proposed integrated system can be effectively applied for practical applications, which significantly reduces the fiber infrastructure cost by effective usage of a single optical fiber link.

42 ENGINEERING↗
DOE OSTI2019

100 Gbps multiplexed inter-satellite optical wireless communication system

In this paper, the performance analysis of the inter-satellite optical wireless communication system (IsOWC) is carried out in presence of optical space channel. Here the proposed model is a 16×100 Gbps dense multiplexed IsOWC. The dual polarized quadrature phase shift keying (DP-QPSK) modulation is used for improving the optical signal to noise ratio tolerance of the system. Further, the spectral efficiency and the receiver sensitivity is improved by incorporating the coherent orthogonal frequency division multiplexing (CO-OFDM) technique in the proposed IsOWC system. The performance of the system is evaluated by bit error rate (BER), error vector magnitude percentage, received signal power, constellation diagram. A comparative study has been carried out between different modulation techniques such as quadrature phase shift keying and DP-QPSK used in IsOWC system. It is observed that, an inter-satellite distance of 15,600 km is obtained with the proposed model at 100 Gbps for a targeted forward error correction log of BER value of − 2.42 or BER of 3.8×10{sup −3}. The maximum possible data rate for different inter and intra orbit satellite has been calculated. Also, the maximum possible transceiver distance has been calculated for different data rates. The integration of two advanced technologies such as DP-QPSK modulation with CO-OFDM technique in the proposed model may impel the market demands for high bandwidth intensive and high data rate applications.

42 ENGINEERING↗
DOE OSTI2026

Generalized Theory and Realization of Reconfigurable Bandpass Filtering Equalizers

Here, in this article, a generalized theory of bandpass filtering equalizers is proposed. A filtering equalizer is a device that combines the frequency-selective properties of a filter with the controllable slope of an equalizer into a single component. The equations used to design the function for a desired slope are provided, and the design methodology to determine the necessary filtering polynomials is also shown. The controllable slope of the dual-function component is realized using variable capacitors, which are used to tune both a transmission zero and a matching network to achieve the desired slope. A third-order bandpass filtering equalizer is designed, fabricated, and measured to verify the generalized theory. The component is designed to operate at 1 GHz with a slope that can be reconfigured from 1 to 3 dB along the passband. This proposed filtering equalizer demonstrates the feasibility of a tunable, low-cost, size, weight, and power (C-SWaP) solution to enable increased flatness in the overall system response and thereby decrease the error vector magnitude (EVM) of future radio frequency (RF) systems and a design process that allows for future development of filtering equalizers.

Filter↗
NASA NTRSDate not supplied

Design of a Thermal Testbed for Metrology of Active Antennas

NASA mission requirements have driven an increased interest in active phased array antennas (APAA) for space-based user communication terminals. Recent advancements in 5G technology have driven down the cost of APAA development and manufacturing all while providing a technology solution that covers many existing Ka-Band satellite communication spectrum bands. While these developments have provided ample opportunities to leverage new chips and arrays for use in space, there is also a need to evaluate these antennas in a relevant environment. Active arrays, as designed for use in 5G, require thermal management to avoid damage to the device as well as to maintain performance. Measured performance under various thermal conditions is essential both for understanding overall APAA performance and ensuring operation is within required tolerances. To address these measurement needs, the SmallSat Ka-band Operations User Terminal (SKOUT) project at the NASA Glenn Research Center (GRC) developed a test environment that combines traditional antenna and communication system metrology with a conduction cooling/heating thermal control system to simulate the space thermal environment. This paper will address the metrologysystem design and performance specifications as well as test article setup and operation. Tests that are typically performed at ambient temperature can now be performed over the typical temperature range of a Low Earth Orbit (LEO) mission. These tests include error vector magnitude (EVM), gain to noise temperature (G/T), antenna patterns, and non-linear characterization. The paper will cover the configuration for each test and provide results from a recent test campaign. Results illustrate the importance of higher fidelity environmental testing when evaluating the performance of an APAA.

active phased array↗
NASA NTRS2021

Australian tidal currents – assessment of a barotropic model (COMPAS v1.3.0 rev6631) with an unstructured grid

While the variations of tidal range are large and fairly well known across Australia (less than 1 m near Perth but more than 14 m in King Sound), the properties of the tidal currents are not. We describe a new regional model of Australian tides and assess it against a validation dataset comprising tidal height and velocity constituents at 615 tide gauge sites and 95 current meter sites. The model is a barotropic implementation of COMPAS, an unstructured-grid primitive-equation model that is forced at the open boundaries by TPXO9v1. The mean absolute error (MAE) of the modelled M2 height amplitude is 8.8 cm, or 12 % of the 73 cm mean observed amplitude. The MAE of phase (10°), however, is significant, so the M2 mean magnitude of vector error (MMVE, 18.2 cm) is significantly greater. The root sum square over the eight major constituents is 26 % of the observed amplitude. We conclude that while the model has skill at height in all regions, there is definitely room for improvement (especially at some specific locations). For the M2 major axis velocity amplitude, the MAE across the 95 current meter sites, where the observed amplitude ranges from 0.1 to 156 cm s −1 , is 6.9 cm s −1 , or 22 % of the 31.7 cm s −1 observed mean. This nationwide average result is encouraging, but it conceals a very large regional variation. Relative errors of the tidal current amplitudes on the narrow shelves of New South Wales (NSW) and Western Australia exceed 100 %, but tidal currents are weak and negligible there compared to non-tidal currents, so the tidal errors are of little practical significance. Looking nationwide, we show that the model has predictive value for much of the 79 % of Australia's shelf seas where tides are a major component of the total velocity variability. In descending order this includes the Bass Strait, the Kimberley to Arnhem Land, and southern Great Barrier Reef regions. There is limited observational evidence to confirm that the model is also valuable for currents in other regions across northern Australia. We plan to commence publishing “unofficial” tidal current predictions for chosen regions in the near future based on both our COMPAS model and the validation dataset we have assembled.

Tidal currents↗
NASA NTRS1979

Evaluation of the navigation performance of shipboard-VTOL-landing guidance systems

The objective of this study was to explore the performance of a VTOL aircraft landing approach navigation system that receives data (1) from either a microwave scanning beam (MSB) or a radar-transponder (R-T) landing guidance system, and (2) information data-linked from an aviation facility ship. State-of-the-art low-cost-aided inertial techniques and variable gain filters were used in the assumed navigation system. Compensation for ship motion was accomplished by a landing pad deviation vector concept that is a measure of the landing pad's deviation from its calm sea location. The results show that the landing guidance concepts were successful in meeting all of the current Navy navigation error specifications, provided that vector magnitude of the allowable error, rather than the error in each axis, is a permissible interpretation of acceptable performance. The success of these concepts, however, is strongly dependent on the distance measuring equipment bias. In addition, the 'best possible' closed-loop tracking performance achievable with the assumed point-mass VTOL aircraft guidance concept is demonstrated.

Mcgee, L. A.↗
NASA NTRSDate not supplied

Wide Bandgap Semiconductor Devices & Systems for Communications in Extreme Environment

The feasibility of Ka-band gallium nitride (GaN) based high power amplifier (HPA) for signal amplification in extreme planetary environment is investigated and its measured performance is presented. The data includes Pout, PAE, EVM for several waveforms and data rates, output spectrum, IMD, Noise Figure, and Gain. The data indicates excellent overall performance. Potential application of this HPA includes communication systems required to operate in the extreme hot environment of Mercury and Venus, extreme cold and high radiation environment of Jupiter’s icy moons, and Artemis missions that involve human/robotic exploration and long-term presence on the Moon.

Gallium Nitride↗