Performance of the cross-correlator receiver for binary digital frequency modulation

The error probability of the cross-correlator receiver for binary digital frequency modulation (FM) detection is studied using theoretical analysis and computer simulations. The index of performance is taken as the bit-error rate (BER). The BER results obtained permit the selection of an optimum combination of modulation index and receiver bandwidth. This selection is carried out and is compared for analysis based on both computer simulation and theoretical calculation. The performance of the cross-correlator is also compared to that of the limiter-discriminator, and is found to be similar. This is noteworthy because the general I/Q demodulator structure of the cross-correlator is ideally suited to DSP chip implementation, and furthermore, severe amplitude limiting does not have to be performed on the input signal to the receiver. Input signal amplitude variations of up to 20% of the average signal value can be tolerated with only a 1-dB loss in performance, and the receiver is completely independent of the rate of amplitude variation. The theoretical analysis of the receiver uses a Fourier series approach which takes into account the effects of FM distortion and intersymbol interference (ISI). Theoretical and simulation results are found to agree within 0.5 dB in E/sub b//N/sub o/. We also address the issue of timing recovery. Results obtained indicate that losses due to timing error can be reduced to less than 0.5 dB in E/sub b//N/sub o/.