860 MHz Low Noise Transistor Preamplifier for Satellite Communication Down Link

Abstract

This paper describes the design and performance of a low noise 860 MHz transistor preamplifier developed for the down chain of earth stations capable of TASO grade I TV reception. Both lumped components and microstripline circuits have been tried as matching sections at the input and output ports of the transistor, to realize a goal of 25 db gain and noise figure <4·0 db over the frequency range 860±20 MHz. The two-stage amplifier has been designed using the S-parameters of the transistor, the first stage being biased for minimum noise figure and the second stage for maximum gain.The two-stage amplifier using lumped components gives a gain of 20±0·5 db and a noise figure around 3·6 db over the frequency range. The lumped component approach suffers from many distinct disadvantages at UHF and microwaves. Hence microstripline design was taken up. A two-stage amplifier using the same transistors and microstripline circuits was built on Rexolite, 1/32 in. thick, copper clad sheet. A gain of 27·5±0·25 db over t...