Method and device for capturing l2c signal in GPS

Abstract

The invention discloses a method and device for capturing L2C signals in the GPS. The method includes the steps of firstly, conducting A / D sampling on intermediate signals, processed by the front end of a receiver, according to the sampling rate; secondly, conducting digital down conversion on the signals sampled in the first step to obtain carrier frequency cells to be searched; thirdly, adding up the signals obtained in the second step with the length of two L2C chips serving as a period to obtain received signals; fourthly, generating local fake codes at the CM code speed in the L2C according to the range of code phase positions to be found; fifthly, conducting related operation on the local fake codes generated in the fourth step and the received signals obtained in the third step; sixthly, if a related value obtained in the fifth step is larger than a capturing threshold, detecting the code phase positions corresponding to sampling points in the adding process in the third step according to the code phase positions corresponding to the related value so that the fuzzy code phase positions caused by adding operation in the third step can be removed; seventhly, if the related value obtained in the fifth step is not larger than the capturing threshold, enabling the receiving signals to slide to find the next code phase position, or adjusting a digital down conversion unit so as to search the next carrier frequency cell till all the code phase positions are found and the whole carrier frequency space is completely searched.

Description

technical field [0001] The present invention relates to the field of global positioning system (GPS), in particular to a method and device for capturing L2C signals in GPS. Background technique [0002] In the process of modernization of the Global Positioning System (GPS), in order to improve signal acquisition and tracking capabilities and improve user performance under weak signal conditions, a new type of civilian signal, namely L2C (English full name: L2civil, where L2 means its Signal frequency point in GPS) signal. The spreading sequence adopted by this signal is significantly different from the widely used C / A code signal. It mixes medium-length pseudocodes (called CM codes) and long-period pseudocodes (called CL codes) through a time-division multiplexing technique. After adopting this technology, the navigation message only modulates the CM code, not the CL code. Adjust the CM code with the navigation message as the data channel to provide the receiving device w...

AI Technical Summary

Problems solved by technology

[0003] Capturing the L2C signal is the prerequisite for the work of the L2C receiving terminal, but the existing capture method takes a long time to capture

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