提出了一种M元正交扩频方案(MOSS:M-ary orthogonal spread spectrum)。按这种方式传输数据，发送信号不存在潜在的周期性，系统的抗干扰和抗截获性能得到了很好的保障。针对伪码较长、载波多普勒频移较大的接收机，传统的PMF-FFT同步捕获算法，进行的FFT点数较多，需要完成大量的复数乘加运算，捕获耗时长，而在较长的捕获时间内，捕获得到的参数估计过于陈旧，无法应用于载波跟踪，提出了一种基于部分匹配滤波器和两级FFT的快速同步捕获算法（PMF-TLFFT），该算法能在搜索出同步点位置的同时，有效估计载波频偏，进行频偏纠正，且计算复杂度显著降低。

Proposed in this paper is a novel method of M-ary orthogonal spread spectrum, with which the potential periodicity of transmitted signals is eliminated and the data are hard to detect or intercept. Thus, both the anti-jamming and the anti-intercept capabilities of the system are well guaranteed. In the condition of long pseudo code and large carrier Doppler frequency shift, the number of FFT points in the conventional synchronous acquisition algorithm is too large, the complex multiplication is of high computational complexity and large time cost, and the parameter evaluation acquired in a long duration is not applicable for carrier tracking because it is too old. In order to solve these problems, an improved fast synchronous acquisition algorithm is proposed, which helps to search for the code synchronization point and estimate the cartier frequency offset for correction, with the computational complexity obviously reduced.