400-to-800-MHz GaAs pHEMT-Based Wideband LNA for Radio-Astronomy Antenna-Array Feed

This letter presents the design of a two-stage 400-to-800-MHz GaAs pseudomorphic high-electron-mobility transistor wideband low-noise amplifier (LNA) to upgrade an aperture synthesis radio telescope. The first stage is based on an inductive-source-degenerated amplifier topology, uses a low voltage supply, and utilizes an intrinsic input-transistor gate-drain feedback to improve the LNA bandwidth and gain. The final stage, a common-source amplifier, provides 50-Ω match and increases the gain. Employing matching via intrinsic feedback and a low-voltage supply, the LNA exhibits gain (S
₂₁
) from 41.1 to 43.3 dB, a minimum input-referred 1-dB compression point of -32.8 dBm, and a noise figure from 0.26 to 0.34 dB over the 400-to-800-MHz band. A future antennaarray feed with such LNAs is expected to exhibit 18.8-26.3 K beam-referred noise temperatures. The LNA consumes 406 mW from a 1.4-V supply.