The impact of doppler effect on the beat frequency signal of linear FM detector

The traditional analysis of linear FM detector´s beat frequency signal was based on that, the detection system and the target were stationary. As a result, it could not reflect the impact of the dynamic delay of the received signal caused by movement and the Doppler Effect. Beginning with the traditional research results, the beat frequency signal is analyzed in both time domain and frequency domain theoretically, with the help of derivation of the Doppler Effect. The result shows that, the beat frequency with the Doppler Effect is not a standard periodic signal, and the Doppler Effect not only causes the frequency spectrum shift of the beat frequency signal but also broadens the spectrum. And the broadening effect is affected by the frequency spectrum of the transmit signal mainly. Combing with the simulation results, the approximate expression of the beat frequency signal´s frequency spectrum under the sports is given at last.