关于北斗卫星接收机信号捕获策略仿真研究

Simulation Research About the Signal Acquisition of BDS Receiver

由于北斗接收机信号捕获时间直接影响着接收机的性能,为了提高捕获速度,软件接收机一般采用FFT操作来代替相关运算。北斗信号采用了高速率码及组合码的结构,高速率的导航数据以及二次编码引起的比特翻转,使得常规的FFT操作捕获方法不适用于北斗信号。根据北斗信号的结构特点,对并行码相位搜索法进行了改进,避免了北斗信号二次编码翻转及导航电文跳变对相关结果的影响。同时,采用圆周移位,在不降低载波多普勒频移精度的情况下,减少了捕获中的运算量。仿真结果表明,改进后的FFT方法,能快速有效的实现不同结构的北斗信号捕获。

Signal acquisition time directly affects the performance of receiver. To improve the acquisition speed, the software receiver generally uses FFT operation for correlation calculation. High rate code and combined code are adopted in BDS signal structure. The bit-flipping is caused by high rate code and combined code, so the traditional acquisition method is not suitable for those signals. According to BDS signal structure, based on the former method, a new method was proposed which avoids the influence of coherent result caused by bit-flipping. Also, the circumference displacement was adopted to reduce the computation burden with the same accuracy of carrier doppler shift. Simulations show that the new method is a rapid and efficient means of capturing BDS signal.