An all-digital demodulation method based on open-loop structure

Abstract

The present invention provides an all-digital demodulation method based on an open-loop structure. The receiver first filters the obtained digital baseband signal through a matched filter to remove out-of-band noise, and then detects the burst signal based on a double sliding window algorithm, and then uses The O&M algorithm completes the timing error estimation of the burst signal, interpolates the obtained sample value through the timing error control cubic interpolation filter, and then performs the cross-correlation operation between the timing synchronized signal and the local synchronization symbol to complete the frame synchronization and eliminate Finally, the phase offset is removed by the phase offset estimation algorithm based on the maximum likelihood criterion to complete the stripping of the carrier and obtain the recovered baseband signal. The sampling rate of the present invention is reduced, and the computational complexity is reduced. The method is simple, the demodulation effect is good, the noise tolerance is high, and the reliability and efficiency of burst signal demodulation are improved.

Description

technical field [0001] The present invention relates to the field of communication technology, in particular to the reception of timing synchronization and carrier synchronization for burst signals modulated by differentially encoded eight-phase phase shift keying (D8PSK) in a VHF DataBroadcast (VHF DataBroadCast) subsystem in a ground-based augmentation system method. Background technique [0002] The document "VHF Data Broadcasting Signal Demodulation Algorithm Design, Computer Application, 2013, 33(10): 2739-2741." discloses a demodulation method based on de-difference, which de-differences the signal before synchronization , by delaying the received signal by one symbol and taking the conjugate, and then multiplying it with the original received signal, so as to eliminate the influence of frequency offset on the synchronization effect. The burst detection, timing synchronization and frequency offset estimation of the system are completed by using the good autocorrelatio...

AI Technical Summary

Problems solved by technology

The method described in the literature completes timing synchronization by increasing the oversampling rate, but does not consider the influence of sampling clock instability on the oversampling rate, and the unstable oversampling rate will bring large errors to the calculation of frequency offset

At the same time, the frequency offset estimation method proposed in the literature does not consider the change of the waveform caused by the pulse shaping filter, which leads to the low frequency offset calculation accuracy of the proposed method in the actual situation.

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