Tech Briefs

Wideband, Dual-Polarized, Ultra-Low-Noise Focal Plane Array Feed for Active/Passive Microwave Remote Sensing

Goddard Space Flight Center, Greenbelt, Maryland NASA missions utilize active, passive, or both, microwave sounders with a large reflector antenna as an important component. In most of these applications, design engineers have realized that desirable science requirements (spatial and temporal resolutions) can be met only by compromising between conflicting engineering design parameters. A microwave remote sensor designed to achieve high spatial resolution would result in longer revisit time, yielding low temporal resolution and vice-versa. To overcome these conflicting requirements, the present technology advocates use of a cluster of feed horns arranged in the focal plane of the primary reflector antenna. Each feed horn produces a different footprint with appropriate overlaps covering a wide swath, allowing a high temporal resolution. Each feed horn, since they act independently, is designed to produce high spatial resolution. However, this approach has many disadvantages compared to an antenna system in which the cluster of horn feeds is made to act as a Focal Plane Array (FPA). Furthermore, the current approach does not enable maximization of the antenna gain, or immunity for radio frequency interference (RFI).

Posted in: Briefs, RF & Microwave Electronics

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RF Source Modifications to Improve Performance of an Electronegative Plasma Thruster

Marshall Space Flight Center, Alabama In traditional gridded electrostatic ion thrusters, positively charged ions are generated from a plasma discharge of noble gas propellant and accelerated to provide thrust. A separate electron source, typically a neutralizer cathode that consumes propellant, is required in the propulsion system to neutralize the ion beam after it exits the thruster, thereby maintaining overall charge balance. However, if high-electronegativity propellant gases are used, a plasma discharge can result that consists of both positive and negative ions. Such an electronegative plasma thruster has the ability to generate thrust with a quasi-neutral ion-ion plume, thus allowing for the elimination of the neutralizer cathode subsystem, reduction of propulsion system complexity, and improvement of system lifetime and operational flexibility.

Posted in: Briefs, RF & Microwave Electronics

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Simple Impedance Matched Planar Microwave Blocking Filter

Goddard Space Flight Center, Greenbelt, Maryland Thermal blocking filters find wide use in cryogenic applications ranging from quantum computing to ultra-low-noise detectors. They can be used to provide the environmental isolation between cooled devices and the warmer temperature supporting bias and readout circuitry. In particular, they are effective in rejecting thermal radiation, limiting radio frequency interference, and providing a convenient means of heat sinking or realizing a vacuum feedthrough for signal lines.

Posted in: Briefs, RF & Microwave Electronics

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Microwave Regenerative Sorbent-based Hydrogen Purifier (MRSHP)

Marshall Space Flight Center, Alabama The Microwave Regenerative Sorbent-based Hydrogen Purifier (MRSHP) is a unique microwave power-based technology demonstrator created for the purification of a hydrogen product stream produced by the Plasma Pyrolysis Assembly (PPA). The MRSHP prototype uses 2.45-GHz microwave power to heat a 13x sorbent bed during a vacuum/thermal contaminant desorption step. By utilizing the well-known high-sorbate-loading capability of conventional physical sorbents coupled with microwave dielectric heating phenomenon, this technology is employed as a regenerative filter for a contaminated hydrogen gas stream.

Posted in: Briefs, RF & Microwave Electronics

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Low-Power Wireless Body Area Network (WBAN) Communication System

Applications include astronaut health monitoring, parts tracking, and sensing. Lyndon B. Johnson Space Center, Houston, Texas NASA seeks semi-passive, RFIDenabled wearable tags for inventory tracking and astronaut body area network applications. Wearable sensor tags can be printed on astronaut clothing or suits, and are powered by printed thin film batteries and/or via energy harvesting. Energy is harvested by flexible solar cells or from the kinetic energy of the astronaut’s motion by minimizing the power requirement of the suit electronics. A tag antenna functions while being flexed or bent, which normally occurs with clothing. Tags communicate with the astronaut body area network. The functions of the RFID system can be extended to include low-data-rate telemetry for bio-monitoring utilizing wearable RFID-enabled biosensors.

Posted in: Briefs, RF & Microwave Electronics

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RF System MATLAB Model Simulation Using a Variety of Data Sources

NASA’s Jet Propulsion Laboratory, Pasadena, California During the development of the Soil Moisture Active-Passive (SMAP) High-Power Amplifier (HPA), a power glitch was observed with the characteristic of producing small 0.1-0.3 dB jumps in power across temperature. In order to troubleshoot this glitch behavior, a nonlinear model that could describe the saturation behavior of the HPA across temperature was desired. However, nonlinear device models were not available for the transistors and components within the HPA. Measured data of the HPA subassemblies were available but were of various formats, including s-parameters, nonlinear pin-pout curves, and fixed losses over temperature, and not easily modeled within commercial EDA (electronic design automation) simulation tools. This tool was built to be able to understand the gain/power distribution stackup and the sensitivities to power changes in the HPA over temperature.

Posted in: Briefs, RF & Microwave Electronics

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Lightweight, Reusable Payload Launch and Transportation Latch

This device can be used for latching cargo in aircraft, supporting hazardous materials, or latching pallets and shipping boxes. Langley Research Center, Hampton, Virginia This innovation addresses the problem of automatic engagement and disengagement of payloads from their transport vehicle when lifted by a crane or other material handling device. The prior state-of-the-art is in material handling devices that require personnel to activate the latch, or latches that are actuated by heavy, bulky actuator systems fixed to the transportation device. These require significant accommodations on the transport vehicle to mate to the latch.

Posted in: Briefs, Mechanical Components

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