| Because of its inherent advantages,W band coherent radar have been widely used in speed detection and imaging.But the initial phase difference between local oscillator and transmit signal will greatly impact on the radar's one-dimensional range. In this paper, based on the coherent theory,the improvement of phase noise for coherent radar frequency synthesizers was analysised , then we simulate the deterioration of one-dimensional range profile causeed by the nonlinear initial phase difference. Based on the coherence analysis and the simulation results,a K-band and W-band coherence measurement modules were done,and the test experiment carried on. Finally one method provided to amendment the fuzzy of one-dimensional range profile caused by the nonlinear phase difference.In order to realize the coherence testing,the theoretical and simulation software were used to analysis the impact of coherent factor of phase noise and range profile,then experimental program designed to get the coherent factor and correct method for the one-dimensional range profile of the radar system.The implementation of W-band coherence measurement system is mainly about the W-band fourth harmonic mixer technology, the low noise amplifier and filter technology and the quadrature demodulation technology. The research on the K-band system is concentrated on the double balance mixer, fivetimes multiplier and the quadrature demodulator. Some components like the harmonic mixer and filter technology were deeply researched.In short, in this dissertation, a simple way was used to measure the coherence of the radar frequency synthesizer. Including harmonic mixer, double balance mixer,multiplier,low noise amplifier(LNA),filter and quadrature demodulator are researched. Those technologies are detailly studied,which might be helpful to further application in microwave and millimeter wave circuits design. |
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