Dual Redundant S-band Ultra Low Noise Amplifier for Space Application
Cunado, O.C.; Albiol, M.A.D.; Vilaseca, R.V.M.
MIER COMUNICACIONES, S.A.

This paper presents the design and measurement results of a Dual Redundant S-band Ultra Low Noise Amplifier that has been space qualified for TERRESTAR I and II satellite programs. Each unit includes two RF chains working in 2-for-1 cold redundancy. The most demanding parameter of this amplifier design is the required Noise Figure (<1.1 dB at 60°C) at operating frequency range (2.0 - 2.02 GHz). This noise figure value includes the insertion losses of the input switch used for selecting the active RF chain.

In order to achieve the minimum insertion losses for the input switch, a miniaturized electromechanical device has been chosen. The first stage of amplification is provided by a packaged GaAs MMIC with the matching and biasing networks implemented externally to the package. These networks have been optimised at the operating frequency band for obtaining the minimum noise figure (0.45 dB at ambient temperature), which allows for a drop-in isolator to be added at the input. Finally, a custom MHIC with two die transistors has been designed as second gain stage in order to achieve the required overall gain of the chain (39 dB).

In total, 160 Dual Redundant Flight Model LNA units have been manufactured and tested with very successful results. Moreover, 4 Engineering Models have been assembled and have been subjected to the full qualification environmental test flow (vibration, shock and thermal vacuum). All the units have fulfilled specifications showing very low dispersion noise figure at 60°C (1.00 ± 0.08 dB) and very stable gain in the temperature range (± 0.3 dB) from -5 to +60°C.