Real-time Blind Demodulation Method for Short-time Burst Signals with Large Frequency Shift

Abstract

The invention provides a method for real-time blind demodulation of a large-frequency-shift short-time burst signal, and aims to provide a method which can increase a correct detection probability of the burst signal and effectively eliminate frequency offset influences of different target signals. According to the technical scheme, the method comprises the following steps: partitioning obtained baseband signals into two paths through a signal processor, detecting one path of baseband signals through a frequency domain amplitude of a digital signal processor (DSP) module, performing fixed-point FFT (Fast Fourier Transform) on the baseband signals, performing accumulated smoothing on a plurality of FFT results, and then performing bandwidth measurement according to accumulated frequency spectrums; and making the other path of baseband signals pass through the DSP module, performing carrier frequency rough measurement through a pilot signal, performing down conversion on the baseband signals once again according to a rough measurement carrier frequency, calculating an accurate measured value of the carrier frequency, setting parameters of a demodulator in an FPGA (Field Programmable Gate Array) according to a modulation type and a symbol rate by the signal processor, guiding the demodulator in the FPGA to perform coherent demodulation in conjunction with a modulation type recognition result and a symbol rate estimation value, and outputting a demodulation result.

Description

technical field [0001] The invention relates to a blind demodulation method suitable for short-time burst signals with large frequency shift. More specifically, it relates to a blind detection and blind demodulation method suitable for short-time burst signals with large frequency shift in satellite communication signals. Background technique [0002] In satellite communication systems and satellite navigation and positioning systems, ultra-long PN code sequences are widely used because of their long repetition period and high code rate, which can provide higher security anti-interference ability and ranging accuracy. In the actual environment, due to the movement of the satellite or the user, the carrier of the received signal has a large Doppler frequency shift, resulting in a sharp drop in the peak value of the PN code correlation. Therefore, the fast acquisition of long PN codes in the environment of Doppler frequency shift is an important factor affecting the performan...

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Problems solved by technology

[0006] The purpose of the present invention is to provide a method that can improve the probability of correct detection of burst signals and can improve the probability of correct detection of burst signals in order to solve the problem that the duration of short-term burst signals with large frequency shifts and burst intervals are different and the length of burst intervals is different in satellite communication signals, and the signal demodulation is difficult. A method for real-time blind demodulation of short-duration burst signals with large frequency shifts that effectively eliminates the frequency offset effects of different target signals

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