Research On X-Band FET Mixers Based On Field Effect Transistor

In the wireless communication receiver system, the X band mixer is one of the important components in the system. It has also been using for satellite broadcasting, communications satellites, the earth exploration satellite, meteorological satellite and other purposes in space applications. The degree of image rejection, conversion loss, isolation and noise directly affect the performance of wideband receiver system. So the research of X band FET mixer has a very important significance. This thesis mainly based on multiple planar microstrip circuit devices,two kinds of X band mixer, i.e.drain mixer and self-oscillating mixer, were researched and designed.First of all, this thesis on the drain mixer put forward the scheme of the block diagram of drain mixer through the relevant theoretical analysis. According to the design scheme, this thesis designs of single tube FET drain mixer, in order to obtain conversion loss lower; wide stopband lowpass filter, in order to inhibit harmonic and reduce the mixer conversion loss; parallel coupled bandpass filter, in order to recovery RF signal, barrier IF signal and reduce the unnecessary energy consumption; DC bias circuit, in order to protect DC signal source and reduce leakage of radio frequency and intermediate frequency signal respectively. The circuit device used HFSS and ADS for simulation and finished the processing test. The test results show that the frequency range of 12.8GHz~13.2GHz, conversion loss is less than 5dB; the RF signal is 13.1GHz, the input power is-20 dBm, the gate voltage is 0V, the drain voltage is 3V and the optimal local oscillator power 13 d B.Secondly, this thesis analyses the theory of self-oscillating mixer. The SIW resonant cavity, open stub low-pass filter and X band oscillator circuit module are simulated by HFSS and ADS software. Then, each module combined together to carry out the joint simulation and the circuits are fabricated and tested. The test results show that, the RF signal is 10.8GHz~11.2GHz, the input power is 5d Bm, the gate voltage is 0V, the drain voltage for the 3V case, the oscillation frequency is generated for the 10 GHz, mixer conversion loss less than 8dB. The circuit has the advantages of compact structure, good performance, convenient testing, will have certain practical application prospect.From the test results of the above two kinds of mixer, the main performance parameters test and simulation test are in good agreement, which proves the correctness of this thesis studies and the rationality of theoretical analysis.