基于FrFT的直扩接收机片内多径搜索

为提高多径信号的能量利用率,提出一种基于分数傅里叶变换(FrFT)的片内多径搜索方法.该方法使用Chirp信号作为导频信号,在接收端对多径Chirp信号进行分数傅里叶变换,根据多径时延差与分数域信号峰值的位置差之间的线性关系,通过检测分数域峰值位置计算出各多径分量的相对时延,搜索精度为Chirp信号带宽的倒数.当Chirp带宽大于扩频带宽时,可用于直扩接收机分辨片内多径.仿真结果表明,文中方法能有效地计算出片内多径时延,在采用等增益方式对片内多径进行合并后,直扩接收机的误码率性能提高.

Subchip Multipath Search for DSSS Receiver 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.