A method of soft demodulation of fsk signal based on fft

Abstract

The invention discloses an FFT-based FSK signal soft demodulation method, which relates to the signal demodulation technology in wireless communication. This method first performs discrete Fourier transform on the received signal, and calculates the amplitude corresponding to the modulation frequency of the FSK signal; then searches for the maximum amplitude corresponding to when the transmitted information bit is 0 and 1 among the amplitudes of all modulation frequencies, and uses The maximum magnitude computes the demodulated soft information for the transmitted information bits. In this method, when calculating the soft information, the maximum amplitude is used to reduce noise accumulation, improve the accuracy of the output soft information, and then improve the receiving performance. In addition, this method is applicable to FSK signals with different modulation orders, and can be jointly applied with different soft-input decoding algorithms. At the same time, the FFT-based frequency domain processing method has the advantage of low complexity in multi-channel parallel demodulation.

Description

technical field [0001] The invention relates to an FFT-based FSK signal soft demodulation method, belongs to the technical field of wireless communication, and is particularly suitable for a frequency-hopping anti-jamming communication system adopting FSK modulation. Background technique [0002] There are three types of modulation methods commonly used in digital modulation technology: amplitude keying (ASK), frequency shift keying (FSK), and phase shift keying (PSK). Among them, the FSK modulation method carries the transmission information on the carrier frequency, and maps different information sequences to different carrier frequencies for transmission during transmission. The receiving end realizes FSK signal demodulation by detecting the carrier frequency of the signal. The commonly used demodulation methods mainly include envelope detection, zero-crossing detection, frequency domain detection and other methods, and the demodulation implementation complexity is low. ...

AI Technical Summary

Problems solved by technology

[0004] For the soft demodulation technology of FSK signals, a soft demodulation method is disclosed in the Chinese patent "A 4FSK Soft Demodulation Method" with the application number 200610020632.X, which uses the energy values ​​of 4 modulation frequency points for conversion , get high and low demodulation soft information, but this method can only be applied to 4FSK signal demodulation

A soft demodulation method suitable for MFSK is disclosed in the Chinese invention patent "A M-Dimensional Soft Decision Viterbi Decoding Method Applicable to MFSK" with the application number 201410712964.9, but this method can only be compared with Viterbi decoding Code algorithm combined use, there are certain limitations in application

Images