A modulation and demodulation method for direct spread dpsk signal

Abstract

The invention proposes a method for modulation and demodulation of direct spread DPSK signals, which generates a set of 0 / 1 original data; performs 2 / 3 convolutional coding and differential coding on the original data; uses spreading codes to spread the coded data Processing; Carrier modulation is performed on the spread-spectrum signal to obtain a direct-spread DPSK signal; Down-conversion and low-pass filtering are performed on the received direct-spread DPSK signal to move the spectrum to near zero frequency; the down-converted data Synchronization, synchronization includes capture and tracking, use matched filter to capture pseudo-code phase difference, use multi-delay correlation algorithm to capture Doppler frequency offset value, and complete the rough synchronization process; code tracking through lead-lag delay phase-locked loop, through Costas loop Perform carrier phase tracking to realize the synchronization of code phase and carrier; despread and demodulate the synchronized signal to obtain transmission information. The invention improves the anti-interference ability of the signal, and realizes the synchronization of the pseudo code and the carrier wave, and ensures the correct despreading and demodulation of the receiving end.

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...

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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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