Phase tracking method of low earth orbit satellite MAPSK communication system

Abstract

The invention relates to the technical field of high-order APSK carrier synchronization, in particular to a phase tracking method of a low-earth-orbit satellite MAPSK communication system. Two phase discriminators are adopted, a loop filter with variable parameters is introduced, and the carrier recovery process is divided into coarse synchronization and fine synchronization; firstly, amplitude judgment is carried out on an MAPSK modulated signal, coarse synchronization is carried out on four constellation points with high signal-to-noise ratio on an excircle by using a polarity judgment algorithm of a simplified constellation, and at the moment, the bandwidth of a loop filter is relatively large, so that large frequency offset can be quickly captured; if the state controller finds that the loop filter is in a locked state by detecting the loop phase error, the loop filter is unlocked, it shows that the coarse synchronization is finished, the carrier recovery circuit is switched to thefine synchronization, phase discrimination is carried out on all constellation points by using a decision guide algorithm, and the loop filtering achieves the purpose of stable tracking through a small-bandwidth mode, thereby effectively improving the performance of the low-orbit satellite high-order APSK communication system.

Description

technical field [0001] The invention relates to the technical field of high-order APSK carrier synchronization, in particular to a phase tracking method of a low-orbit satellite MAPSK communication system. Background technique [0002] With the development of satellite communications, spectrum resources are becoming increasingly tight, while the demand for data transmission is increasing day by day, which requires satellite communications to achieve high-speed data transmission within a limited bandwidth, so high-order modulation with high bandwidth efficiency is required Way. The satellite channel is a typical nonlinear channel. Compared with the low-order modulation, the high-order modulation signal will face more serious signal distortion. The traditional QAM modulation constellation has more amplitude levels, so it is very sensitive to channel nonlinearity; while the concentric APSK constellation has less amplitude changes, and the distortion generated when passing thro...

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Problems solved by technology

However, these high-order APSK modulation signals are more seriously affected by the carrier frequency difference, and because there are multiple amplitudes in the high-order APSK modulation constellation, the minimum phase difference between signal points is smaller, and the phase discrimination becomes narrower, limiting The phase detection range of the phase detector is limited, so that the conventional full-constellation phase detector cannot work under a large frequency offset

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