| The theory and method of the linear and sequential FM wave signal is used in the fixed distance system of FM Doppler, which is good at choosing distance and capable of anti-interference.In this thesis, the fixed distance system of sawtooth wave FM Doppler is worked over. The expression of the difference frequency signal is particularly speculated and analyzed,which is mixed by the transmitted signal and received signal in the system. According to the analysis, the basic fixed distance scheme is proposed. The feasibility of the entire system is proved by the Matlab/Simulink simulation. The circuits of signal processing are designed and implemented by using the software of the Multisim simulation, which is including the integral circuit and the difference frequency signal demodulated circuit and so on. Thereinto, the integral circuit is used for producing modulated signal and the difference frequency signal demodulated circuit is composed of operational amplifier. Finally, based on the different characteristic expression of the modulated signal, we compare and analyze the fixed distance system of the sawtooth wave FM Doppler and that of the triangle wave FM Doppler. |
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