The Design Of The Radar Receiver For An IF Direction-finding System By Comparing Amplitude And Phase

This paper is based on the project of the ultra band IF direction finder by comparing amplitude and phase, which belongs to the 985 projects. According to the working principle and the requirement of the direction finder, the structure of the 4 channels 1 frequency conversion superheterodyne receiver based on the MIC and the MMIC devices is designed. And the frequency source of the receiver is designed and manufactured.Firstly, according to the radar receiver system modules'parameter, the frequency character in the frequency conversion circuit is analyzed. Then the design scheme of the system is decided and the function module is confirmed. The design scheme is realizable, which is proved by checking the performance of the receiver system.The circuit of the frequency down-conversion module is the main part of the receiver system. The double balance frequency mixer is used in this module. The function modules of the frequency down-conversion module, which include coupling circuit, low noise amplifier module, frequency mixer circuit, intermediate frequency amplifier and filter, power-splitter circuit for LO and power-splitter circuit for test signal, are designed and manufactured. And the EMC design of the frequency down-conversion module is also carried out.The design of frequency source has become the key technique of the receiver system and the radar system. The direct digital frequency synthesizer (DDS) and PLL technique are used in the design of the frequency synthesizer in this paper. The frequency synthesizer, which includes the DDS, PLL and the control circuit based on ARM, is designed and tested.The test results of the receiver and the frequency source circuit show that the design meets the system requirement well.