Modulation and demodulation method for direct spread DPSK signals

Abstract

The invention provides a modulation and demodulation method for direct spread DPSK (Differential Phase Shift Keying) signals, including the following steps: generating a set of 0 / 1 original data; performing 2 / 3 convolution encoding and differential encoding on the original data; performing spectrum spreading on the encoded data by using a spread spectrum code; performing subcarrier modulation on the signals after spectrum spreading to obtain direct spread DPSK signals; performing down-conversion and low-pass filtering on the received direct spread DPSK signals, and shifting the frequency spectrum to near the zero frequency; synchronizing (including capturing and tracking) the data after down-conversion, capturing the pseudo code phase difference by matched filtering, and capturing the Doppler frequency offset value by using a multi-delay correlation algorithm, in order to complete a coarse synchronization process; carrying out code tracking through a lead-lag delay phase-locked loop, and carrying out carrier phase tracking through a Costas loop, in order to realize the synchronization of code phase and carrier; and de-spreading and demodulating the synchronized signals to obtain transmission information. The anti-interference ability of signals is improved, the synchronization of a pseudo code and a carrier is realized, and correct de-spreading and demodulating of the receiveris ensured.

Description

technical field [0001] The invention belongs to the technical field of modulation and demodulation of direct spread signals, in particular to a modulation and demodulation method of direct spread DPSK signals. Background technique [0002] In the military data link, the received signal contains Doppler frequency deviation, and the electromagnetic environment is complex, so anti-interference ability and low interception performance are also required. G.J.R.Povey and others first proposed a capture model based on the combination of digital partial matched filter and FFT (PMF-FFT). Two-dimensional acquisition of pseudo-code phase and carrier frequency offset, but this method is mainly suitable for MPSK signals, and the capture range of Doppler frequency offset is small, and it is still not applicable in the environment of high dynamic and low signal-to-noise ratio. Contents of the invention [0003] The technical problem solved by the present invention is to provide a modula...

AI Technical Summary

Problems solved by technology

G.J.R.Povey and others first proposed a capture model based on the combination of digital partial matched filter and FFT (PMF-FFT). Two-dimensional acquisition of pseudo-code phase and carrier frequency offset, but this method is mainly suitable for MPSK signals, and the capture range of Doppler frequency offset is small, and it is still not applicable in high dynamic and low SNR environments

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