窗函数在成形滤波器设计中的应用

The Application of Window's Function to Design of Shaping Filter

讨论了具有奇对称过渡带的成形滤波器的设计问题，得到一个较为一般性的结论：在频域上，成形滤波函数为一个理想低通滤波函数与一个窗函数的卷积；其中升余弦滚降滤波器为一特例。在理论上进一步证明了引入滚降系数可以降低对采样时钟精度的要求。理论分析和数值分析的结果表明升余弦滚降滤波器并非一较好的滤波器。

in this paper,the problem of design of shaping filter with odd symmetrical transition band is discussed.An relatively general conclusion is obtained:on frequency domain,the shaping filtered function is the convolution of ideal low pass filtered function and one window's function.As one special example,the rasied consine roll off function is the convolution of ideal low pass filtered function and consine window's function.It is proved that introducing of roll off coefficienta,(0<α<1)can reduce the requirement of sampling clock accurate theoretically.When te bias of sampling clock exists,acording to the requirement of quantity of intersymbol interference,the tapnumber of equalizer can be calculated by using numerical analysis.Meanwhile,the result of theoretical and numerical analysis shows that the rasied consine roll off filter is not a better shaping filter.