A kind of FM pilot signal generating method and circuit

Abstract

The application provides an FM (frequency modulation) pilot signal generation method and circuit, wherein the method comprises: processing a double-track audio signal into a baseband signal, and introducing the baseband signal into a system PLL, the system PLL being provided with a VCO; the system PLL locking a reference oscillation frequency to be a simulation signal according to the channel coding corresponding to a target emission frequency, modulating the simulation signal according to the baseband signal, and controlling the VCO to output the carrier wave signal of a first frequency according to a modulation result; performing first frequency division treatment on the carrier wave signal to obtain an FM emission signal of the target emission frequency; performing second frequency division treatment on the carrier wave signal to obtain a signal of a second frequency; and a DDS performing frequency controlling on the signal of a second frequency according to a frequency control word to generate a pilot signal. The FM pilot signal generation method and circuit are suitable for a low frequency crystal oscillator FM double-track stereo emission system, and can generate an FM emission signal and a pilot signal through the system PLL.

Description

technical field [0001] The present invention relates to the technical field of FM (frequency modulation, frequency modulation), in particular to a method and circuit for generating an FM pilot signal. Background technique [0002] In FM stereo transmission, since stereo is more susceptible to signal interference than mono, the left channel signal L and the right channel signal R need to be algebraically coded, that is, sign1=L+R, sign2=L-R, composed of two independent The audio channel is used for transmission; sign1 is transmitted by the main channel as baseband audio, and the transmission frequency range is 30Hz to 15kH; sign2 is transmitted by the subcarrier signal, and the specific sign2 is transmitted on the 38kHz double-sided suppressed carrier (DSB-SC) signal through amplitude modulation. Occupies the frequency band 23kHz ~ 53kHz. When receiving stereo audio, it is necessary to receive the sign1 and sign2 signals, and calculate and restore the information of the left...

AI Technical Summary

Problems solved by technology

[0004] At present, in the FM two-channel stereo transmission system, the 19kHz pilot frequency is mainly generated by fixed high-frequency crystal oscillators such as 24M / 12M / 7.6M. However, in some FM two-channel stereo transmission systems, the crystal oscillator does not High frequency, such as only 32.768kHz; therefore, the FM two-channel stereo transmission system for low-frequency crystal oscillators mainly realizes the FM transmission frequency and 19kHz pilot frequency by setting two system PLLs (Phase Locked Loop, phase-locked loop) Signal generation, that is, one of the system PLLs is used to generate the FM transmission frequency, and the other system PLL is used to generate the 19kHz pilot signal; however, the power of the system PLL is relatively large, and two channels are set in the FM two-channel stereo transmission system A system PLL will make the system produce larger power consumption; therefore, how to realize the generation of the pilot signal with lower power consumption in the FM two-channel stereo transmission system becomes a problem that those skilled in the art need to consider

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