基于FrFT的直扩系统片内多径搜索及合并方法

提出一种基于分数阶傅立叶变换的直扩系统片内多径搜索方法.使用Chirp信号作为导频信号,在接收端对多径Chirp信号进行分数阶傅立叶变换,根据多径时延差与分数域信号峰值的位置差之间存在的线性关系,通过检测分数域峰值位置进而计算出各多径分量的相对时延.搜索精度等于Chirp信号带宽的倒数,所以当Chirp带宽大于扩频带宽时可分辨片内多径.仿真结果表明,提出的方法能够有效地计算片内多径时延,在采用等增益方式对片内多径进行合并后接收机误码率性能获得提高.

On Search and Combination of Subchip Multipath for DSSS System Based on Fractional Fourier Transform

A subchip multipath search method for DSSS system based on fractional fourier transform(FrFT) is proposed. Linear frequency modulated chirp signal is used as pilot signal, the multipath chirps are processed by FrFT at receiver, then the relative delays between multipath chirps can be calculated after detecting peak positions according to the linear relationship between the relative delay in time domain and difference between peak positions of multipath chirps in FrFT domain. The search resolution in time domain is equal to reciprocal of the bandwidth of Chirp signal, so the Chirp signal with bandwidth lager than that of DSSS signal shoud be used to recognize subchip multipath. Simulation results show that the proposed method can calculate the relative delay of subchip multipath effectively, and the BER performance of receiver can be improved after the EGC process of the recognized subchip multipath.