4 图144用汉宁窗口滤波后的富里哀级数 因为乘以窗口函数,改变了富里哀级数的系数,所以,现在图形(见图144)看起来 好多了 接下来,让我们把锯齿波加到传递函数为H(s)= 的线性系统中 s+60 函数 fares专门解决此类问题。 function y=fsresp(num, den, un, wo) %o FSRESP Fourier Series Linear System Response FSRESP(N, D, Un, Wo)returns the comples exponential FS of the output of a linear system when the input is given by a FS N and d are the numerator and denominator coefficients espectively of the system transfer function Un is the complex exponential Fourier Series of the system input Wo is the fundamental frequency associated with the input Copyright(c)1996 by Prentice-Hall, Inc if nargin<4. wo=1: end N=(length(un )-1)/2: highest harmonic jn Wo=sqrt(-1)*(-N: N)*wo; frequencies of harmonics y=(polyval(num, nwO). /polyval(den, jn Wo)). * un; output is Yn=HGnWo)*Un 运用 forest,我们得到 >>Yn=fsresp(60,[1 601, Fn, wo); find response coefficients >>y=fseval(Yn, t, wo); evaluate output 结果见图145。0 0.1 0.2 0.3 0.4 0.5 0 2 4 6 8 10 图 14.4 用汉宁窗口滤波后的富里哀级数 因为乘以窗口函数，改变了富里哀级数的系数，所以，现在图形（见图 14.4）看起来 好多了。 接下来，让我们把锯齿波加到传递函数为 H s s ( ) = + 60 60 的线性系统中。 函数 fsresp 专门解决此类问题。 function y=fsresp(num, den, un, wo) % FSRESP Fourier Series Linear System Response % FSRESP(N, D, Un, Wo) returns the comples exponential FS of the % output of a linear system when the input is given by a FS % N and D are the numerator and denominator coefficients % respectively of the system transfer function. % Un is the complex exponential Fourier Series of the system input. % Wo is the fundamental frequency associated with the input. % Copyright (c) 1996 by Prentice-Hall, Inc. if nargin<4, wo=1; end N=(length(un)-1)/2; % highest harmonic jnWo=sqrt(-1)*(-N : N)*wo; % frequencies of harmonics y=(polyval(num, jnWo) ./ polyval(den, jnWo)).*un; % output is Yn=H(jnWo)*Un 运用 fsresp，我们得到： >>Yn=fsresp(60, [1 60], Fn, wo); % find response coefficients >>y=fseval(Yn, t, wo); % evaluate output >>plot(t, f, f, y) % plot system input and output 结果见图 14.5