| FM Doppler radio of the fixed distance system transmits frequency modulated continuous wave signal,through the signal processing of the difference frequency signal which is gotten by mixing the transmitted signal and the received signal, the speed and distance information of the target can be valued. FM modes include:sine wave FM, triangle and sawtooth FM. Its characteristics are:high fixed distance precision, high receiver sensitivity, low working voltage, good distance selectivity, simple structure and strong anti-interference ability, so the study into it has important theoretical and practical significance.In this paper, sine wave frequency modulation of the fixed distance system is mainly studied:firstly, the spectrum of the difference frequency signal under the circumstances of both stationary and moving targets is analyzed, then, the mathematical expressions of the difference frequency signal which is gotten by mixing the transmitted signal and the received signal in both time and frequency domain are deduced, on this basis, the fixed distance scheme is proposed, then use the Matlab/Simulink software platform for the whole system simulation so as to demonstrate the fixed distance scheme, use the Multisim software to design the specific circuit and simulate, use the Protel DXP software for PCB drawing, then weld the real circuit board and debug, finally, compare the sine wave FM of the fixed distance system with the linear FM of the fixed distance system, for example, the sawtooth wave FM system, analyze their advantages and disadvantages respectively. |
PDF Full Text Request