Pseudo-random code estimation method of direct sequence spread spectrum system

Abstract

The invention discloses a pseudo-random code estimation method of a direct sequence spread spectrum system, which mainly overcomes the shortcomings of high requirement on sampling precision, great error of carrier frequency estimation and poor universality of the prior method. The invention comprises the following steps: 1. obtaining a pseudo code period and a symbol period from a secondary spectrum and a secondary moment of related functions; 2. determining a starting point of the pseudo code of a period according to an autocorrelation matrix of a received signal; 3. taking a pseudo code starting point as the starting point for the received signal, taking a plurality of pseudo code periods as window size for subsection, carrying out inherent time-scale decomposition on each section through carrier frequency and a first zero-crossing point frequency, and obtaining respective instantaneous amplitude value; 4. subtracting one instantaneous amplitude value from the other instantaneous amplitude value to obtain a difference signal, and making a column diagram to set two thresholds; 5. recording the moment when a minimum point is lower than a smaller threshold in a pseudo code period ofthe difference signal; and 6. setting the polarity of starting code strip, determining the polarity of each code strip from the second code strip, and determining the pseudo code according to pseudocode property. The invention has the advantages of high estimation precision and strong universality, and is used for monitoring frequency spectrum.

Description

technical field [0001] The invention belongs to the field of communication and signal processing, and in particular relates to a method for estimating a pseudo-random code, which is used for estimating the pseudo-random code of a direct sequence spread spectrum signal under non-cooperative conditions. Background technique [0002] The communication system based on direct spread technology has been widely used in military communications. Since direct spread signals usually work at a very low signal-to-noise ratio, the signal is very weak and submerged in white noise. For direct spread signals, especially spread spectrum false Estimation of random sequences has always been a hot and difficult research topic in the field of communication countermeasures. In the field of civil communication, the rapid development of mobile communication represented by code division multiple access has brought huge challenges to spectrum monitoring, and a fast and appropriate pseudo code estimati...

AI Technical Summary

Problems solved by technology

Utilizing the cyclic shift characteristic of the m sequence, the estimated value of the m sequence is obtained by calculating the third-order correlation function of the m sequence. This method can only estimate the m sequence. For other spread spectrum pseudo-random sequences, it does not satisfy the cyclic shift characteristic. cannot be estimated by this method

[0006] The above-mentioned methods all complete the estimation of the pseudo-random sequence on the baseband, but the estimated carrier signal used for down-conversion has errors, which leads to carrier residue after down-conversion, which affects the estimation accuracy of the pseudo-random code; at the same time Due to the need to sample the signal at the chip rate, it has high requirements for timing synchronization

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