基于全相位新型余弦滚降滤波器设计

Design of a novel cosine roll-off filter based on all-phase

数字通信系统的误码率来源有两个方面,一个是码间串扰(inter symbol interference,ISI)和信道噪声,其中噪声只能抑制,而ISI则可以消除。本文基于全相位滤波技术,设计出一种新型余弦滚降特性半带滤波器,通过选择不同的卷积窗而可以得到滤波器簇。该余弦滚降滤波器在消除码间串扰的同时,对噪声进行了较大程度的抑制。首先,给出一维全相位数字滤波器系统架构,并推导出数学表达式,分析了两个重要特性。其次,设计出新型滚降特性全相位半带滤波器,仿真出幅频特性和衰减特性曲线。第三,分别基于传统和新型余弦滚降特性滤波器设计出基带数字信号传输系统,并对比统计出不同信噪比条件下的误码率。结果表明,信噪比高于2.5 dB后,采用新型余弦滚降滤波器系统的误码率明显低于传统系统,最大改善3 dB。

In digital communication system,bit error rate originates from two aspects,one of which is channel noise that can only be suppressed to some degree and the other is inter symbol interference that can absolutely be eliminated if the Tx/Rx filters have cosine roll-off characteristics.This paper presents a novel cosine roll-off semi-band filter based on all phased filtering technology.And it's convenient to construct a cluster of filters via selecting different convolution window which is obtained by convoluting base windows.Inter symbol interference(ISI)is eliminated by applying this novel cosine roll-off filter,and channel noise is restrained to larger extent as well.Firstly,the system architecture of one dimensional all-phased filter is given and the algorithm formula are derived mathematically.In addition,two properties of all-phased filter are analyzed,which are frequency sampling and correlation weakening.Secondly,a novel cosine roll-off semi-band filter is designed and the figures both of amp-freq and attenuation are simulated accordingly.Thirdly,two systems for base band digital signal transmission with the traditional and this novel cosine roll-off filters respectively are constructed,wherein BER is compared under different signal-to-noise.Experimental results show that when the signal-to-noise is below 2.5 dB,bit error rate of the system using this novel cosine roll-off filter is significantly lower than that using the traditional filter.The maximum improvement is up to 3 dB.