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扩频码周期与信息码周期之比非周期将会导致相邻的信息码对应的扩频码不同,常规的同步方法不再适用。为解决非周期性直扩信号伪码快速捕获和同步的难题,提出了采用每1/4个码元积分,然后取绝对值相加的方法来剥离信息位,进行伪码粗捕和跟踪,每1/2个码元积分进行位同步,最后将位同步信息进行载波跟踪完成整个同步过程的方法。该方法运算速度快,对符号位不敏感,能够消除非周期直序列扩频带来的影响。现场可编程门阵列(FPGA)实现结果表明:该方法在信噪比大于-20d B条件下,对伪码长度为1023的M序列非周期直序列扩频,能做到可实现无误码同步性能。
The non-periodicity between the spreading code period and the information code period will result in different spreading codes corresponding to adjacent information codes, and the conventional synchronization method is no longer applicable. In order to solve the problem of fast capture and synchronization of aperiodic DSSS signal pseudo-code, this paper proposes to strip the information bit by every 1/4 symbol integral and then add the absolute value, Every 1/2 symbol integral bit synchronization, and finally the bit synchronization information carrier tracking to complete the synchronization process. The method is fast in computation and insensitive to the sign bit, and can eliminate the influence of non-periodic direct sequence spreading. The result of field programmable gate array (FPGA) shows that the proposed method can achieve error-free synchronization when the S / N ratio is greater than -20d B .