50 – 500 MHz Low Noise Amplifier with FM band rejection

Abstract

Observing the radio sky at low frequencies, particularly in sites where FM signal and other RFI dominates, is highly challenging, since the radio receiver is prone to be driven to saturation by these strong signals. So it is required that the receiver should have high dynamic range and / or very low sensitivity to FM signal for proper observation. We have developed a low- noise amplifier with about 40 dB rejection to the FM signal, in the frequency range of 50 – 500 MHz for use in the Sky Watch Array Network (SWAN). It has a noise temperature ranging from 40-80 K, a gain of 20 dB with a variation of ± 1.5 dB around the band center and around 60 dB dynamic range over the specified band. The design details and test results are presented in this report.