S-band High-performance Broadband Channel Receiver Front-end System Developed

The first part is to introduce the application background of the research project and the background of the application in the receiver of the high temperature superconducting technology. And the basic designing theory of receiver, diplexer of the HTS and low temperature LNA is discussed in details. The method and process of the receiver designing are described. Finally, the testing results of the main components of the receiver and the overall system are presented.The diplexer of HTS is successfully designed by regulating the characteristic impedance and electrical length of the T-type transmission line and the coupling coefficient of the band pass filter according to the theory of the linear matching network. Compared with conventional diplexers including the type comprised with high and low pass filters, the type composed of coupler connecting with bandpass filters, and the type comprised with circulors, this diplexer is smaller and has better performance. According to the design method in normal temperature, and combining with the low temperature design experience, a low noise figure amplifier working in the low temperature is designed. For achieving the ultimate goal of the receiving system, the components including the RF module, mixing module and IF module are also completed.According to the experimental results, the diplexer made of HTS thin films with very low microwave surface resistance has low insertion loss, little effect on the noise performance of the system even if placed in the front. The low temperature LNA operating in liquid nitrogen temperature reduces the system noise. Therefore, the performance of sensitivity and interference suppression of the front-end system of channelized receiver composed of the high-temperature superconducting diplexer and low temperature LNA have been improved greatly.