Design Of Front-End Circuit Of K-Band Satellite Receiver

The front-end circuit is important in satellite communication systems. In this paper, some of the key circuits were designed and built, including waveguide-to-microstrip transition, low noise amplifier (LNA), image-reject filter, mixer etc.In this paper, two kinds of waveguide-to-microstrip transitions were analyzed and designed by commercial EM field solver (CST? Microwave Studio). The experimental results show that the insert loss of K-band probe waveguide-to-microstrip transition is less than 0.4dB. Additionally, the short conductive septa in finline were analyzed by the same EM field solver and a finline filter was designed. Furthermore, the finline filter is combined with a wide-band w/g-to-microstrip probe transition to configure a compact high-performance quasi-planar filter which is low insertion loss, high slope selectivity and can be easily integrated with planar solid circuit. The experimental result indicates that the insert loss is less than 2dB in passband and more than 70dB in stopband.Basing on HEMT FET, a mono-stage LNA was designed. The testing data shows that the noise figure (NF) of the LNA is less than 1.5dB with a gain more than 11dB. The parallel-coupled microstrip image-reject filter achieves attenuation more than 65dB in the image frequency.To sum up, it can be concluded that if those circuits were integrated into the low noise block, the noise figure of the low noise block can be less than 1.8dB.