Two-dimensional capture method and device in Doppler domain and delay domain

Abstract

The invention relates to a two-dimensional acquisition method and device in the Doppler domain and delay domain, and belongs to the technical field of direct sequence spread spectrum communication. In this method, FFT transformation and circular shift are performed on the direct spread pilot signal, and then multiplied by the FFT transformation sequence of the local pseudo code, and after IFFT transformation, the matched filter result of carrier Doppler compensation is obtained, and then the interpolation is used to fit Methods The sampling rate of the matched filtering results was adjusted to achieve code Doppler compensation. The output results of interpolation and fitting were non-coherently accumulated and thresholded to determine the carrier frequency offset and pseudo code phase of the direct spread pilot signal. Compared with the prior art, the present invention uses the acquisition method of carrier Doppler and code Doppler joint compensation, which overcomes the shortcomings of the traditional acquisition method in high dynamic, large pseudo-code length, and weak signal environments. The method corrects the movement of the correlation peak, thereby avoiding the platform effect in the non-coherent accumulation, and greatly improving the capture performance.

Description

technical field [0001] The invention relates to a two-dimensional acquisition method in the Doppler domain and delay domain, especially suitable for the detection of the pilot signal of the direct sequence spread spectrum system and the search for its Doppler frequency offset and code offset in the environment of high dynamics and low signal-to-noise ratio The invention relates to a pseudo code phase and belongs to the technical field of direct sequence spread spectrum communication. Background technique [0002] The baseband digital signal processing of the direct sequence spread spectrum communication system mainly uses two modules of acquisition and tracking. The acquisition module mainly realizes the rough estimation of the carrier frequency and pseudo code phase of the received signal, and provides the initial value of frequency and code phase for the carrier loop and code loop of the tracking module. [0003] It is assumed that the spreading code of the direct sequenc...

AI Technical Summary

Problems solved by technology

[0043] In many cases such as long distances and weak signals, the acquisition module often needs to increase the height of the correlation peak through incoherent accumulation to meet the requirements of capture accuracy. However, traditional algorithms often ignore the movement of the correlation peak caused by the code offset. In the case of large Puller or long pseudo-code, the movement of the correlation peak will cause a platform effect in the non-coherent accumulation, which will have a huge impact on the capture accuracy

[0044] The principle of the platform effect is: as mentioned above, |y m (n)| peak appears at n=(0 f s +δmN>) N At , with the change of m, the peak position will also move accordingly. When the Doppler is small, the pseudo code length is short, or the number of incoherent accumulation symbols is small, the traditional algorithm often ignores the movement of the correlation peak, and considers that (0 f s +δmN>) N =(0 f s +mN>) N =(0 f s >) N , all correlation peaks appear at n=(0 f s >) N However, in the application environment such as satellite communication, due to reasons such as high dynamics, long distance, limited transmission signal power, and high communication security requirements, the Doppler effect is strong, the pseudo code is long and the number of non-coherent accumulation symbols is large, As a result, the correlation peak no longer appears at the same position, but presents a small-scale average dispersion, and the result of incoherent accumulation presents a platform shape, and the peak is obviously weakened, which seriously affects the capture accuracy

Images