Frequency modulation and demodulation system and signal processing method

Abstract

The frequency modulation and demodulation system comprises a variable capacitance diode frequency modulation circuit module which generates an oscillation signal with stable frequency as the center frequency of a frequency modulation signal, realizes frequency modulation of an input modulation signal through a variable capacitance diode, sets the direct-current reverse bias voltage of the diode randomly in a power supply voltage range to change the center frequency and the frequency modulation sensitivity of the frequency modulation signal; a down-conversion circuit module which reduces the center frequency of the frequency modulation signal so as to adapt to sampling of an oscilloscope with a lower sampling rate; a low-frequency digital oscilloscope which is used for sampling and outputting the time domain waveform data of the frequency modulation signal; and a upper computer which is used for importing the data into the MATLAB software platform for demodulation calculation. The method has the beneficial effects that important performance index parameters such as the maximum frequency offset, the center frequency and the frequency modulation linear distortion degree of the frequency modulation signal can be simply, effectively and accurately measured.

Description

technical field [0001] The invention relates to the technical field of frequency modulation demodulation, in particular to a frequency modulation demodulation system capable of accurately and quantitatively measuring main performance index parameters of frequency modulation signals and a signal processing method thereof. Background technique [0002] As the main technical means in high-frequency communication, signal frequency modulation technology is widely used in FM broadcasting, TV audio, microwave communication, phase-locked circuit and frequency scanner, etc. [0003] In practical application, performance requirements such as large FM frequency deviation, good FM linearity, stable center frequency, and small parasitic amplitude modulation are put forward for the FM circuit. In the experimental research, the measurement of the above performance indicators is mainly through the spectrum analyzer to measure the frequency spectrum of the FM signal, and the center frequency...

AI Technical Summary

Problems solved by technology

However, through the above method of measuring the frequency spectrum of the FM signal with a spectrum analyzer to measure the main performance index parameters of the FM signal, there are problems such as large measurement errors in the center frequency and maximum frequency deviation of the FM signal, and the judgment of the FM linearity is not intuitive and accurate enough.

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