A Frequency Demodulator Based on Adaptive Sampling Frequency Phase-Locking Scheme for Large Deviation FM Signals

摘要

A frequency demodulation scheme based on adaptive sampling frequency phase-locking loop (PLL) is proposed for extracting large deviation message signal from sinusoidal frequency-modulated signals. The proposed scheme has been designed to track the frequency-modulated input signal using a look-up-table and adaptively changing the sampling period. While tracking the carrier signal, the numerically controlled oscillator involved in the PLL structure produces the sampling frequency according to the variation of input frequency. In the PLL, the message signal has been extracted at the output of proportional integral controller. Simulation results prove that the PLL exhibits quick acquisition behavior, wide operating range, negligible steady-state error. Experimental investigation validates the efficacy of the proposed PLL performance in message signal extraction.