【摘要】 微弱全球定位系统(GPS)卫星信号的捕获需要较长的积分时间,但受导航数据位翻转的影响,一般采用10 ms的相干积分。为进一步提高捕获灵敏度,提出了一种数据位翻转预估算法,该算法通过对多组信号积分结果的对比估算出翻转位的位置,舍弃存在位翻转的5 ms数据从而消除其影响,并对其余数据进行15 ms的分块相干积分。同时,为降低分块相干积分中非相干积分的平方损耗,采用差分相干积分对其进行改进,并在运算过程中采用"先累加后相关"的方式,在进一步提高捕获灵敏度的同时降低运算复杂度。仿真结果表明,该算法能高效地捕获到信噪比低至-50 dB的信号,可有效地提高GPS接收机的捕获灵敏度和捕获效率。更多还原

【Abstract】 Long coherent integration duration is needed for weak Global Positioning System(GPS) signal acquisition.However,it is limited in 10 ms by the navigation data bit flipping,which is far from enough. To further improve the acquisition sensitivity,a bit-flipping prediction algorithm was proposed. Firstly,the 5 ms signal with possible involve bitflipping,which was detected through the comparison of the coherent integration results of the several blocks of data,was canceled. Then coherent integration was applied to its sub-block signal in rest 15 ms and the results did differential coherent integration to overcome its bit-flip and reduced the square loss of non-coherence. At the same time,the summation operation was done ahead of coherent integration to depress its computational complexity. The theoretical research and simulation results show that the acquisition sensitivity and acquisition efficiency have been improved,and the algorithm even can capture the weak signal with Signal-to-Noise Ratio(SNR) less than- 50 dB.更多还原