Full-digital demodulation method based on open loop structure

Abstract

The invention provides an all-digital demodulation method based on an open loop structure. The receiver firstly filters out-of-band noise of an obtained digital baseband signal through a matching filter, detects a burst signal on the basis of a double-sliding-window algorithm; an O & M algorithm is adopted to complete timing error estimation of the burst signal, controls a cubic interpolation filter to carry out interpolation operation on the obtained sample value through a timing error; and performs cross-correlation operation on the signal after timing synchronization and a local synchronization code element to complete frame synchronization and eliminate a frequency offset error, and finally, removes phase offset through a phase offset estimation algorithm based on a maximum likelihoodcriterion to complete stripping of a carrier, thereby obtaining a recovered baseband signal. The sampling rate is reduced, and the calculation 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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