关键词: QI, 2FSK, 解调器

Abstract: The paper analyzes the characteristic of the 2FSK signal in the QI standard.And a new method of digital demodulation for 2FSK signals is proposed and implemented.In the method,we reflects the change of frequency,accordingto the change ofthe sum of the width of the multi period.Firstly,the frequencyof the input signal is measured by a fixed frequency,and summed.Then,the value is filtered and smoothed,so that the frequency variation characteristics are extracted so as to facilitate the later decoding process.In the final FPGA implementation,the method can detect frequency variations of the two signals with periodic phase difference 32nsonlybythe frequencyofthe 2MHz.

Key words: QI, 2FSK, demodulator