Design Of Front-End Circuit Of K Band Satellite Receiver

The front-end circuit is important in satellite communication systems. In this paper, the design of the K-band front-end circuit of satellite receiver , is presented. It has many distinct advantages such as high gain ,low noise ,low cost and simple structure, making it promising in future application. First we give the analysis of the receiver front-end block diagram, link budget and specification allocation (such as noise figure). Then, all the sub-circuits , including low noise amplifier, waveguide-to-microstrip transition , image reject band--pass filter, low-pass filter, and sub-harmonic mixer , are described in details. Finally the test circuits are designed, manufactured and measured.The experimental result and EM analysis show that "probe" type waveguide-to-microstrip transition, compared with other types , has the merit of simple structure, good hermeticity and low insertion loss ( less than 0.3dB ); The amplifier using HEMT produces noise figure of 1.5dB with 8dB gain; The image reject band pass filter , using parallel coupling line structure, can improve noise performance and eliminate interference , by suppressing image more than 60dB ; the sub-harmonic mixer will simplify local oscillator design, especially in millimeter wave bands. A novel approach is presented in sub-harmonic mixer design ,which enables to establish the optimum loading conditions for the different signals to get low conversion loss and good matching simultaneously. Total noise figure of the front-end is less than 2dB with 55dB overall gain over the specified frequency band.