Lightweight low noise space qualified L-band LNA/filter assemblies

The authors present the design and results of a compact L-band low noise amplifier (LNA) and receive filter assembly that has been space qualified for the INMARSAT 3 satellite program. Up to 88 (dual redundant) flight model assemblies are required (22 per satellite). Twenty four engineering models have been built, one of which has been subjected to full qualification levels of vibration and thermal vacuum. The design of the low noise amplifier stages and receive filter incorporate many new design features to satisfy the requirements of very stable gain and phase performance with low noise figure (2.3 dB max) when subjected to wide temperature differential (95°C range). Tracking (gain and phase) between units is of paramount importance in this phased array application. Maximum phase difference between units for any 18°C temperature delta is 4°. Total gain of the amplifiers is 47 dB. The amplifier chains incorporate a phase compensation network and an ASIC controlled temperature gain compensation circuit. The filter incorporates a temperature compensation mechanism which provides for very stable phase performance and state of the art techniques for satisfying the stringent rejection requirements