微弱GPS信号避开比特跳变的捕获算法

Avoiding Bit Transition Acquisition Algorithm for Weak GPS Signal

为了提高全球定位系统(Global Positioning System,GPS)接收机的灵敏度,信号捕获过程需要加长积分时间。分析了比特跳变对加长相干积分时间的限制,从而提出一种能够完全避免比特符号跳变的捕获算法。该算法通过对多组数据采用相干积分和非相干积分相结合的方法,比较各组积分结果并选取积分最大值,用来判决是否捕获。算法中相干积分时间为19ms,目的是使积分最大值组完全避开数据位跳变,避免导航数据符号跳变对相干积分值的影响。该算法在避开比特跳变的基础上最大程度地提高相干积分时间,提高GPS接收机的捕获灵敏度。仿真结果表明,该算法能有效地捕获到载噪比(Carrier to Noise Rate,CNR)低至26dB·Hz的信号,可有效提高GPS接收机的捕获灵敏度。

In order to enhance the sensitivity of Global Position System（GPS）receivers,increasing the coherent integration time is necessary for the signal acquisition process.This paper analyzes how the bit sign transition limits the coherent integration time and proposes a novel acquisition algorithm to avoid the bit sign transition limitation.The method employs coherent integration combing with non-coherent integration.By comparing the integration results of the several blocks,the maximum integration result is selected and is used to determine whether to acquire.The algorithm extends the coherent integration time to 19 ms.The purpose is to make the block of the maximum integration result completely avoid bit transition,and avoid the influence of navigation data bit transition on the results of the coherent integration.The algorithm extends the coherent integration time to the greatest extent on the basis of avoiding bit transition,and then improves the acquisition sensitivity of the GPS receivers.The simulation results show that the acquisition sensitivity has been improved,and the algorithm can acquire the weak signal with Carrier-to-Noise Ratio（CNR）as low as 26dB·Hz.