Double threshold detection method for weak satellite signal acquisition

Abstract

The invention relates to a threshold detection method for weak satellite signal acquisition. The signal comprises pseudo range measuring codes. The method comprises the following steps: A, carrying out correlation integration on every possible satellite for N milliseconds, and carrying out M-times difference accumulation on the obtained result; B, determining whether a satellite signal exists or not according to the preset upper limit and lower limit of threshold; C, if the detected signal-to-noise ratio is greater than the upper limit of the threshold, then judging that a strong signal exists; D, if the detected signal-to-noise ratio is less than the lower limit of the threshold, then judging that no signal exists; E, if the detected signal-to-noise ratio is between the two thresholds, then carrying out near-far effect elimination algorithm on the detected strong signal, and detecting the processed data again; and F, and calculating the upper limit of the threshold after the strong signal is eliminated, and if the detected signal-to-noise ratio is greater than the threshold, then judging that a signal exists. The method considers the influence of near-far effect on weak satellitesignal acquisition and introduces the concept of detection after the strong signal is eliminated. Compared with the traditional method, the invention reduces the false-alarm probability.

Description

technical field [0001] The invention relates to the field of navigation satellite signal capture, in particular to a double-threshold 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 through the limi...

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Problems solved by technology

According to the stochastic signal processing theory, the threshold of a single detection is generally set according to the Constant False Alarm Rate (Constant False Alarm Rate), which requires setting a certain false alarm probability. Under this condition, it is calculated according to the probability density function of the detector The corresponding threshold value, the disadvantage of this threshold setting method is that it does not consider the interference and influence that may exist in the actual detection

Near-Far Effect (Near-Far Effect) is a kind of energy interference generated by the cross-correlation between different pseudo-random codes in the CDMA communication system. For the detection of weak satellite navigation signals, when strong and weak signals exist at the same time, the strong signal The resulting far-near effect interference will greatly affect the normal detection of the signal, resulting in false capture

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