Phase judgment method used for DQPSK demodulation

Abstract

The invention discloses a phase judgment method used for differential quaternary phase shift keying (DQPSK) demodulation. The method comprises the following steps: a) determining a fixed value n according to a signal frequency Fz and an AD sampling frequency Fs of a DQPSK modulation signal; b) judging a phase area in which a phase difference (DP) of each of AD sampling points and a corresponding adjacent sampling point is positioned, wherein (n-1) sampling points are between each of the AD sampling points and the corresponding adjacent sampling point; c) counting the number of continuous AD sampling points positioned in the same phase area as the DP between the AD sampling points and the corresponding adjacent sampling points; and d) judging a signal phase change corresponding to the counting according to the number of the AD sampling points counted each time and performing modification on the next phase. The phase judgment method used for the DQPSK demodulation provided by the invention has a very good effect in near instantaneous companded audio multiplex modulation, greatly reduces bit error rate, highly effectively restores the phase shift information before demodulating and ensures the fluency of near instantaneous companded audio multiplex decoding.

Description

technical field [0001] The invention belongs to the communication field, and in particular relates to a phase judgment method for DQPSK demodulation. Background technique [0002] With the rapid development of mobile communication technology, communication systems and communication methods have also been rapidly developed. Among them, differential quadrature phase shift keying (Differential Quaternary Phase Shift Keying, DQPSK), also known as quadrature phase shift keying, is a good mobile communication technology. [0003] At present, DQPSK demodulation is mainly based on analog demodulation, supplemented by digital demodulation. Among them, phase judgment is required in digital demodulation, which is a technology that does not exist in analog demodulation. Therefore, compared with the mature analog demodulation, how to correctly and effectively restore the phase change in the digital demodulation process is a very critical and important step. [0004] For traditional DQ...

AI Technical Summary

Problems solved by technology

However, for the phase judgment of demodulation of some signals (for example: NICAM (Near Instantaneous Companded Audio multiplex, NICAM) signal), the bit error rate requirement is very high, and several thresholds cannot be simply set to define the phase state

Because there will always be some points near the threshold, once a judgment error occurs, it will seriously affect the subsequent digital decoding

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