Double differential coherent detection method for capturing weak satellite signal

Abstract

The invention relates to a double differential coherent detection method for capturing a weak satellite signal. The signal comprises a pseudorange measurement code. The method comprises the following steps that: A. total quantity of search units is determined according to an inputted signal sampling rate and a correlation integral time; B. each potential satellite and each search unit are undertaken the correlation integral with the length of N millisecond, and relevant results of homodromous and orthogonal branch circuits are respectively recorded; C. data processed in step B is inputted into a double differential device to obtain a single differential result of each search unit; D. the result which is obtained in step C is accumulated for M times; E. the search unit corresponding to the maximum value of the outputted result in step D is found out; F. a signal-to-noise ratio corresponding to the result in step E is solved and is compared with a threshold to judge whether the signal exists or not. The double differential coherent detection method overcomes the phase influence in the traditional differential accumulation, has higher noise resistant performance compared with the traditional double differential method, and can improve the detected signal-to-noise ratio.

Description

technical field [0001] The invention relates to the field of navigation satellite signal capture, in particular to a double-difference coherent detection method suitable for weak satellite signal capture. Background technique [0002] In recent years, satellite navigation and positioning systems have been more and more widely used. The general-purpose satellite navigation receiver can conveniently perform three-dimensional positioning and achieve positioning accuracy that meets the requirements. However, in harsh positioning environments such as indoors, forests, city centers, canyons, and tunnels, the navigation satellite signals are attenuated to varying degrees, making the received satellites The signal power is lower than ordinary satellite signals. For ordinary satellite navigation receivers, the capture of navigation satellite signals cannot be realized in this case, and the tracking and positioning calculation of signals cannot be performed. In order to break throug...

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Problems solved by technology

[0003] The differential coherent detector originated from the detection and estimation of CDMA communication system signals, and is an emerging signal detection method, J.Iinatti, A.Pouttu, "Differentially coherent code acquisition in Doppler", Proc.IEEE VTC'99Fall, vol.2 , Sep.1999, pp.703-707. and HaraldElders-Boll, Uwe Dettmar.Efficient Differentially Coherent Code / DopplerAcquisition of Weak GPS Signals.IEEE.2004 all discuss that real differential coherent detectors have The effect of anti-square loss, but there is no specific analysis of the noise probability and statistical characteristics of the differential coherent detector, so it is impossible to demonstrate its superiority from the perspective of signal-to-noise ratio

Wei Yu, Differential Combining for Acquiring Weak GPS Signals, Signal Processing 87(2007) 824-840 proposed the architecture of complex differential coherent detector for the first time, and proved that real differential coherent detector will be affected by carrier phase, but did not give specific solution

Compared with the real differential coherent detector, the advantage of the complex differential coherent detector is that there is no influence of the carrier phase, but the improvement of the signal-to-noise ratio is not obvious. Certain obstacles

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