TRW designed and fabricated two identical SP-HVDE trays which were flown in the NASA 5.75-year LDEF (Long Duration Exposure Facility), one near the leading edge and the other near the trailing edge, in the LEO (Low Earth Orbit) environment. Each experiment tray consisted of six assemblies with each made of Kapton dielectric samples of varying thicknesses (i.e., 2 mils, 3 mils, and 5 mils) biased under +/-300 V I +/-500 V I and +/-1000 V. The objectives have been successfully achieved by measuring the first post-flight long-term (i.e. roughly 8-month experiment) average leakage current through 95% measurable coulombmeters and surface materials. M/D (Micrometeoroid and Debris) impacts over the dielectric samples were examined using a SEM (Scanning Electron Microscope) and an EDS (Energy Dispersive Xray Spectrometer) to investigate the synergism of surface degradation and environmental interactions.
An X-band high-power amplifier (HPA) based on gallium nitride (GaN) high electron mobility transistors (HEMTs) has been developed for synthetic aperture radar (SAR) applications. A hybrid power combining technique, including microstrip circuits and waveguides, is used to design the HPA. For reducing the size, four 50 W GaN HEMTs cascaded with one 1-to-4 power divider and one 4-to-1 power combiner form a 4-way power combined PCB circuits. For combing the high power and driving an antenna, two PCB circuits are combined by magic-T waveguides. The transmission efficiency of the power combining is approximately 80%. In the 10% duty cycle (pulse width 100 us), the output power of the HPA is over 200 W across the band of 9.5–9.8 GHz. The maximum output power is 230 W at 9.5 GHz, and the power gain is 8.3 dB at 46.1°C.
Radiation effects on InP -based electrical and optical devices are discussed from the standpoint of device structure and physics. The devices addressed are High Electron Mobility Transistor (HEMT), Heterojunction Bipolar Transistor (HBT), and solar cells.Radiation effects due to neutrons, gamma rays, electrons, protons, x rays, and total dose radiation can result in device parameter degradation, upset, burnout, and current leakage problems. The effects are correlated to device structure and material properties. Comparisons are made to GaAs or Si devices that have performance characteristics similar to the above -mentioned InP devices. Finally, recommendations are made for testing and modeling these effects.
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