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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 1,063 records · Page 59
All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

Gated CDS Integrator

A Gated CDS Integrator (GCI) may amplify low-level signals without introducing excessive offset and noise. The GCI may also amplify the low level signals with accurate and variable gain. The GCI may include a modulator preceding an amplifier such that offset or noise present in a signal path between the modulator and a demodulator input is translated to a higher out of band frequency, and thereafter reduced by a double sampled discrete time integrator which also reduces thermal noise. The thermal noise may also be reduced by averaging the output of the discrete time integrator.

Quilligan, Gerard T.↗
NASA NTRS2019

A Novel Reconfigurable GaN Based Fully Solid-State Microwave Power Module for Communications/Radar Applications

In this paper, we present as a proof-of-concept (POC) the design, integration, and performance of a novel reconfigurable GaN based fully solid-state MPM. The module synergistically integrates diplexers, pre-amplifiers, multistage medium power amplifiers (MPAs), SPDT switches, and CW/Pulsed high power amplifiers (HPAs) with a voltage sequencer, a DC blanking controller, and a low voltage electronic power conditioner. The POC SSMPM operates at both S-band and X-band to serve multiple roles. The SSMPM can be reconfigured to deliver Psat of 39 dBm (8 W CW) at S-band, Psat of 46 dBm (40 W CW) at X-band, and Psat of >50 dBm (>100 W Pulsed) at X-band. Lastly, our link budget calculations indicate that the SSMPM with Psat = 40 W when coupled to a 10 cm X-band transmit antenna on a low Earth orbiting (900 km) satellite can close a 1 Gbps (QPSK) data downlink to a 1 m receive antenna on ground with 3 dB margin.

Simons, Rainee N.↗
NASA NTRS2018

Fiber-Based Laser MOPA Transmitter Packaging for Space Environment

NASA’s Goddard Space Flight Center has been developing lidar to remotely measure CO2 and CH4 in the Earth’s atmosphere. The ultimate goal is to make space-based satellite measurements with global coverage. We are working on maturing the technology readiness of a fiber-based, 1.57-micron wavelength laser transmitter designed for use in atmospheric CO2 remote-sensing. To this end, we are building a ruggedized prototype to demonstrate the required power and performance and survive the required environment. We are building a fiber-based master oscillator power amplifier (MOPA) laser transmitter architecture. The laser is a wavelength-locked, single frequency, externally modulated DBR operating at 1.57-micron followed by erbium-doped fiber amplifiers. The last amplifier stage is a polarization-maintaining, very-large-mode-area fiber with ~1000 μm2 effective area pumped by a Raman fiber laser. The optical output is single-frequency, one microsecond pulses with >450 μJ pulse energy, 7.5 KHz repetition rate, single spatial mode, and > 20 dB polarization extinction.

Lasers and Masers↗
NASA NTRS2018

High-Rate Ka-Band Modulator for the NISAR Mission

In order to meet ever-increasing data return requirements, more satellites are using the near-Earth Ka-band (25.5 – 27.0 GHz) to achieve higher downlink rates. The paper discusses the Universal Space Transponder - Ka-band Modulator (UST-KaM) developed at the NASA Jet Propulsion Laboratory for the NASA-ISRO SAR (NISAR) mission, which is capable of transmitting up to 1.74 Gbps with 7/8 LDPC encoding. The UST-KaM utilizes OQPSK with both baseband and RF filtering to contain the 1 Gsps transmission spectrum within the 1.5 GHz Ka-band, even with the use of an external, saturated amplifier. Due to the high data rates involved, several technical hurdles were overcome in both the digital and RF designs. The UST-KaM is a software defined radio with two digital circuit board assemblies: a low speed housekeeper board for commanding and telemetry, and a high-rate signal processing board known as the Signal Processing Module (SPM). The SPM receives data from the spacecraft via a SERDES interface at up to 2 Gbps, processes and encodes the data using a Xilinx Virtex-5 FPGA, and produces 1 Gsps OQPSK I and Q waveforms via synchronized, multiplexed DACs. The RF Electronics in the UST-KaM employ a heterodyne architecture in which the I/Q digital waveforms are filtered and then up-converted using a sub-harmonic IQ mixer. The LO of the converter, which is included in the exciter assembly, is at 13.125GHz, and the RF output is a 26.25GHz carrier which is modulated with the OQPSK waveforms. The output of the mixer is then filtered using low loss quartz thinfilm edge coupled Chebyshev filters and amplified through a series of low gain Ka-Band amplifiers. The exciter assembly also has a 2GHz, low-phase-noise, PLL synthesizer to supply the clock to the DACs for the high rate digital waveforms.

Spurgers, Carl↗
NASA NTRS2022

Linear Disturbance Amplification Over Blunted Flat Plates in High-Speed Flows

Modal and nonmodal instability characteristics of cylindrically blunted flat plates with varying leading edge radii are described for Mach 4 and Mach 6 freestream conditions. The selection of leading edge radii and freestream parameters is informed by experimental conditions. The investigation of this 2D problem provides a slow entropy layer swallowing which allows for an isolated development of perturbations seeded upstream within different wall-normal regions of the flow. At both Mach numbers, a decrease in modal instability amplification was seen as the leading edge radius was increased. Nonmodal analysis reveals amplifying perturbations in the boundary layer as well as in the entropy layer. The medium bluntness regime exhibits the strongest amplification of nonmodal disturbances that is nonmonotonic in character. Small amplitude boundary forcing at the plate surface or volumetric forcing at various wall-normal heights was used to account for receptivity effects. While wall forcing effectively induced modal instabilities, only an actuation above the boundary layer captured disturbances that amplify within the entropy layer. The optimal nonmodal theory’s entropy-layer disturbance evolution exhibited outstanding agreement with controlled forcing, including receptivity effects. The evolution of entropy-layer disturbances from the optimal nonmodal theory showed excellent agreement with the results of receptivity to controlled forcing. Therefore, the nonmodal optimal growth analysis may provide a useful as well as efficient technique to identify the complete disturbance spectrum in blunt hypersonic configurations, where both modal and nonmodal disturbances can amplify in the boundary-layer and entropy-layer regions.

Boundary layer transition↗
NASA NTRS2022

Linear Disturbance Amplification Over Blunted Flat Plates in High-Speed Flows

Modal and nonmodal instability characteristics of cylindrically blunted flat plates with varying leading edge radii are described for Mach 4 and Mach 6 freestream conditions. The selection of leading edge radii and freestream parameters is informed by experimental conditions. The investigation of this 2D problem provides a slow entropy layer swallowing which allows for an isolated development of perturbations seeded upstream within different wall-normal regions of the flow. At both Mach numbers, a decrease in modal instability amplification was seen as the leading edge radius was increased. Nonmodal analysis reveals amplifying perturbations in the boundary layer as well as in the entropy layer. The medium bluntness regime exhibits the strongest amplification of nonmodal disturbances that is nonmonotonic in character. Small amplitude boundary forcing at the plate surface or volumetric forcing at various wall-normal heights was used to account for receptivity effects. While wall forcing effectively induced modal instabilities, only an actuation above the boundary layer captured disturbances that amplify within the entropy layer. The optimal nonmodal theory’s entropy-layer disturbance evolution exhibited outstanding agreement with controlled forcing, including receptivity effects. The evolution of entropy-layer disturbances from the optimal nonmodal theory showed excellent agreement with the results of receptivity to controlled forcing. Therefore, the nonmodal optimal growth analysis may provide a useful as well as efficient technique to identify the complete disturbance spectrum in blunt hypersonic configurations, where both modal and nonmodal disturbances can amplify in the boundary-layer and entropy-layer regions.

Boundary layer transition↗
NASA NTRS2022

Responses of Compound Daytime and Nighttime Warm-Dry and Warm-H Events to Individual Anthropogenic Forcings

Daytime heat is often associated with reduced soil moisture and cloud cover, while nighttime heat is connected to high humidity and increased cloud cover. Due to these differing mechanisms, compound daytime and nighttime heat events may respond differently to major anthropogenic forcings (greenhouse gases, anthropogenic aerosols, land-use and land-cover change). Here, we use GISS ModelE2.1-G historical single-forcing runs from 1955 to 2014 to examine how individual anthropogenic forcings affect compound heat events—specifically warm daytime and nighttime temperatures compounded with dry precipitation or high humidity conditions. We show that greenhouse gases alone amplify the natural frequency of warm-dry events by 1.5–5 times and warm-humid events by 2–9 times in tropical and extratropical latitudes. Conversely, aerosols and land-use/land-cover change reduce the frequency of these events, resulting in more modest increases and in some regions, declines, in the historical 'all-forcings' scenario. Individually, aerosol effects are stronger and more widespread compared to land-use, oftentimes reducing the natural frequency of these events by 60%–100%. The responses of these compound events are primarily driven by changes in daytime and nighttime temperatures through large-scale warming via greenhouse gases and cooling from aerosols and land-use/land-cover change. However, changes in warm-dry events are amplified in regions with concurrent precipitation declines (e.g. Central America, Mediterranean regions) and warm-humid events are amplified by global concurrent humidity increases. Additionally, we find differences between daytime and nighttime compound responses in the historical experiment that can be traced back to the individual forcings. In particular, aerosols produce a greater cooling effect on daytime relative to nighttime temperatures, which notably results in a historical reduction of Northern Hemisphere daytime warm-dry events relative to natural conditions. Our analysis provides a more comprehensive understanding of the significant impacts of different anthropogenic climate forcings on daytime and nighttime warm-dry and warm-humid events, informing future risk and impact assessments.

Anthropogenic forcings↗
NASA NTRS2024

Investigation into the Origin of the RF Phase Noise for the LISA Laser Transmitter

The Laser Interferometer Space Antenna (LISA) mission is a collaborative consortium led by the European Space Agency (ESA)in cooperation with the National Aeronautics and Space Administration (NASA). LISA’s goal is to capture gravitational wave events, such as spacetime distortions caused by massive orbiting bodies. Multiple low noise, single frequency master oscillator power amplifier (MOPA) lasers with a polarization-maintaining Yb-fiber amplifier will serve as the light sources for the LISA observatory. The NASA Goddard Space Flight Center (GSFC)is currently developing the laser transmitters for this project. The LISA lasers will carry radio frequency (RF)sidebands for exchanging reference RF clock information between spacecrafts. Excess phase noise, especially carrier-sideband differential phase noise added to the modulation side band by the phase modulator and the fiber amplifier, becomes a concern. In the gravitational wave frequency ranges, leading sources of this RF “differential” phase noise can be both intrinsic and extrinsic. Examples of intrinsic sources include thermal load on the active fiber, thermo-mechanical induced birefringence, and nonlinearities in the various passive and active fibers. Extrinsic sources can include external temperature fluctuations and infrasonic mechanical strain or vibrations. These noise spectra usually include both white and pink (1/f) thermal noise contributions. This work investigates the physical origins and impact of these sources of RF phase noise, and their characteristic spectra and management will be discussed.

Laser Interferometer Space Antenna↗
NASA NTRSDate not supplied

Progress of 2.05 uM Fiber Laser Development for A Martian Co2 Dial

We have proposed a new concept for differential absorption lidar (DIAL) operating in the 2050 nm CO 2 absorption band for atmospheric CO 2 and pressure observations on Mars. This concept has earned us funding from NASA's PICASSO Program to advance 2050 nm fiber laser technology for future space applications. The laser design is an all-fiber master oscillator and power amplifier (MOPA) system. The master oscillator with pulse shaping and several stages of fiber preamplifiers has been built. Preliminary tests show the output pulse energy can reach 1 mJ, meeting our baseline goal. However, the current power amplifier design has an issue with undesired parasitic lasing at a different frequency, which exhausts pump energy and limits the laser energy. We have modified the power amplifier design to suppress parasitic lasing, and higher laser power energy is expected. To achieve high measurement accuracy, the laser frequency must be stabilized. A fraction of the master oscillator is split to lock the laser frequency to the center of the selected absorption line. The laser can then be shifted to a frequency far from the absorption line center, where extinction due to CO 2 and other trace gases is minimal, serving as the offline reference. The online wavelength is optimized at 2050.44156 nm, ensuring a CO 2 absorption optical depth (AOD) of approximately 1.1 at 3 km, which maximizes the signal-to-noise ratio (SNR) for measurements in the lower Martian atmosphere. At the conference, we will provide more details about this project and report on the progress of instrument development.

DIAL↗
NASA NTRS1966

Applications of models to circuits

Active device models for linear circuit application and their application to design of operational amplifier and emitter-peaked voltage amplifier stage

SOLID STATE DEVICE↗
NASA NTRS2006

Deep Space Network, Cryogenic HEMT LNAs

Exploration of the Solar System with automated spacecraft that are more than ten astronomical units (1 AU = 149,597,870.691 km) from earth requires very large antennae employing extremely sensitive receivers. A key figure of merit in the specification of the spacecraft-to-earth telecommunications link is the ratio of the antenna gain to operatio nal noise temperature (G/Top) of the system. The Deep Space Network (DSN) receivers are cryogenic, low-noise amplifiers (LNAs) which addres s the need to maintain Top as low as technology permits. Historicall y, the extra-ordinarily sensitive receive systems operated by the DSN have required ctyogenically cooled, ruby masers, operating at a physi cal temperature near the boiling point of helium, as the LNA. Althoug h masers continue to be used today, they are hand crafted at JPL and expensive to manufacture and maintain. Recent advances in the developm ent of indium phosphide (InP) based high electron mobility transistor s (HEMTs) combined with cryogenic cooling near the boiling point of h ydrogen have made this alternate technology comparable with and a fraction of the cost of maser technology. InP HEMT LNA modules are demons trating noise temperatures less than ten times the quantum noise limi t (10hf/k) from 1 to 100 GHz. To date, the lowest noise LNA modules developed for the DSN have demonstrated noise temperatures of 3.5 K and 8.5 K at 8.5 K at 32 GHz, respectively. Front-end receiver packages employing these modules have demonstrated operating system noise temperatures of 17 K at 8.4 GHz (on a 70m antenna at zenith) and 39 K at 3 2 GHz (on a 34m antenna at zenith). The development and demonstration of cryogenic, InP HEMT based front-end amplifiers for the DSN requir es accurate component and module characterization, and modeling from 1 to 100 GHz at physical temperatures down to 12 K. The characterizati on and modeling begins with the HEMT chip, proceeds to the multi-stag e HEMT LNA module, and culminates with the complete front-end cryogenic receiver package for the antenna. This presentation will provide a n overview of this development process. Examples will be shown for de vices, LNA modules, front-end receiver packages, antennae employing these packages and the improvements to the down-link capacity.

low-noise amplifiers (LNAs)↗
NASA NTRS2006

A G-band 160 GHz T/R Module Concept for Planetary Landing Radar

In this work, the concept of a G-band transmit/receive (T/R) module centered at 160 GHz was discussed. The design makes use of state-of-the-art G-band MMIC low noise amplifiers and power amplifiers, and a high speed SPDT InGaAs PIN diode switch. The paper reports on the designs, chip results, and the integration concept for a 160 GHz T/R module. The G-band T/R module has applications toward precision altimetry and velocimetry measurements in landing radar, such as in future planetary landers on the surface of Mars

power amplifier↗
NASA NTRSDate not supplied

Radiation-Hard Parallel Readout Circuit for Low-Frequency Voltage Signal Measurements

NASA Goddard Space Flight Center (GSFC) has successfully developed and tested a custom-designed low-noise multi-channel digitizer (MCD) application specific integrated circuit (ASIC) for operation in harsh radiation environments. The MCD-ASIC is optimized for low-frequency and low-voltage signal measurements from sensors and transducers. It has 20 input channels where each channel is comprised of auto-zeroed chopper variable-gain amplifier, post amplifier, and a second order ∑∆ modulator. ∑∆ analog-to-digital converter (ADC) relies on oversampling and noise shaping to achieve high-resolution conversion. However, the MCD-ASIC requires digital filtering and decimation to convert the output single bit streams from the ADC to useful data words. A parallel digital platform such as a field-programmable-gate-array (FPGA) is highly suitable to fully leverage the capabilities of the MCD-ASIC. The FPGA controls the MCD-ASIC via serial peripheral interface (SPI) protocol and acquires data from it. A Python-script communicates with the FPGA board through a USB interface on a cross operating platform. Using this architecture, the system is capable of monitoring up to 20 voltage readout channels simultaneously in a real-time manner. Each channel’s parameters can be programmed independently allowing maximum user versatility. In this paper, we present analysis of the analog front-end, the implementation of the digital processing unit on the FPGA, and provide noise performance results from the MCD-ASIC readout.

ASIC↗
NASA NTRS1966

Phase inverter provides variable reference push-pull output

Dual-transistor difference amplifier provides a push-pull output referenced to a dc potential which can be varied without affecting the signal levels. The amplifier is coupled with a feedback circuit which can vary the operating points of the transistors by equal amounts to provide the variable reference potentials.

Source record↗
NASA NTRS1967

Solid state phase detector replaces bulky transformer circuit

Miniature solid state phase detector using MOSFETs is used in a phase lock loop with a sun-bit detector in an integrated data-link circuit. This replaces bulky transformer circuits. It uses an inverter amplifier, a modulator switch, and a buffer amplifier.

Moberly, C. L.↗
NASA NTRS1969

Sweep frequency detector

Sweep detector or passive spectrum analyzer provides a positive monitoring of the bandwidth of the input amplifier of a tracking receiver. Used with an oscilloscope, it provides a visual display of a microwave amplifier bandpass.

Clauss, R. C.↗
NASA NTRS1970

Precision full-wave rectifier

Simplified circuit uses one operational amplifier and two precision resistors. The amplifier is operated open loop for switching and closed loop for linear gain, both simultaneously.

Deboo, G. J.↗