扩频接收机中带通滤波器最优相对带宽分析

Analysis of the Band-pass Filter's Optimum Relative Bandwidth in Spread-Spectrum Receivers

本文推导了扩频接收机检波前信噪比与接收端带通滤波器带宽等参数的关系,并进行了相应的数值分析。研究结果表明,接收端带通滤波器存在最优相对带宽使得检波前信噪比最大,并且最优带宽不等于信号带宽;最优相对带宽与输入载噪比、中心频率及相关积分时间无关,但受收发两端滤波器类型影响;当发射端滤波器相对带宽大于等于0.8时,接收端滤波器最优相对带宽与发射端滤波器相对带宽无关。

This paper presents the expression of signal -to -noise ratio（SNR） before detection and the parameters such as the band- pass filter＇s bandwidth and so on in spread- spectrum receivers. Through numerical analysis, it is proved that there is an optimum relative bandwidth of this band - pass filter which maximizes the SNR before detection and which is not equal to the bandwidth of the signal. The optimum relative bandwidth is independent of the input carrier - to - noise ratio, center frequency and correlative integral time. But it is affected by the filter＇s type in both transmitters and receivers. When the filter relative bandwidth of the transmitters is not less than 0.8, the optimum relative bandwidth in the receivers is independent of the band - pass filter＇s bandwidth of transmitters.