Development and Study of Demodulation Techniques for Frequency Manipulated Signals

Abstract

The goal of our research is development and study of different demodulation techniques for a frequency shift keyed signals. The signal under study is a frequency-shift keyed (FSK) signal when the information signal regulates the carrier frequency. We consider a model imitating data transmission channels and allowing us to perform error counting. The data transmission channels have ideal synchronization. Several techniques of demodulator design are introduced for demodulating frequency-shift keyed (FSK) signal and we compare the techniques using the criterion of error number of a demodulated signal relative to a signal prior to modulation for different signal-to-noise ratio. Signal-to-noise ratio is calculated as a ratio of the energy of the information symbol to the noise power spectral density. We have tested different demodulation techniques with different signal-to-noise ratio and produced a table containing information on demodulation accuracy for different techniques. Overall, we have simulated 100 sec. of continuous bit packages. We indicate that the best results for signal-to-noise ratio exceeding 5 dB are provided with the technique based on double correlation, and for signal-to-noise ratio less than 5 dB - with the technique based on the fast Fourier transform.

Keywords

• demodulation
• frequency-shift keyed signals
• fast fourier transform
• autocorrelation function
• double correlation