8844S元J5元5,A.[2]e'5"5, A.[2]e5",A.[1]eH,[m] =(A,[0], A.[1]e对H[m|做5点IDFT可得2元k-4元2元k4+4元2元k2-8元2元k3+8元55555h[k]= A,[0]+ A,[1](e) + A.[2](e+e+e2元2( (2k -4) + 24.[2]co(学(2k-4)= A,[0] + 2 A,[1]cos]5
[ ] { [0], [1]e , [2]e , [2]e , [1]e } π 5 4 j d π 5 8 j d π 5 8 j d π 5 4 j Hd m Ad Ad A A A − − = 对Hd [m]做5点IDFT可得 5 [ ] [0] [1](e e ) [2](e e ) 5 2π 3 8π j 5 2π 2 8π j d 5 2π 4 4π j 5 2π 4 j d d − + − + = + + + + k k k k h k A A A p + − = + − (2 4) 5 2π (2 4) 2 [2]cos 5 π [0] 2 [1]cos d d d A A k A k
I型线性相位滤波器在M+1个取样点值为-jM-mM+10≤m≤M/2H.[m]=3 A.[m]eH*IM+1-mlM/2+1≤m≤M例：用频率取样法设计一个满足下列指标的型线性相位高通滤波器2=0.5元，2,=0.6元M=32;Wp=0.6*pim=0:(M+1)/2;Wm=2*pi*m:/(M+1）;%mtr=ceil（Wp*（M+1）/（2*pi））Ad=[Wm>=Wp];%Ad（mtr)=0.28;Hd=Ad.*exp(-j*0.5*M*Wm);Hd=[Hdconj（fliplr(Hd(2:M/2+1)))l;h=real（ifft(Hd)）;w=linspace(0.1,pi,1000);H=fregz(h/[llw);plot(w/pi,20*logl0（abs(H)））;grid;
I型线性相位滤波器在M+1个取样点值为 + − + = + − H M m M m M H m A m m M m M M [ 1 ] / 2 1 [ ]e 0 / 2 [ ] d 1 π j d d 例:用频率取样法设计一个满足下列指标的I型线性相位高通滤波器。 Ws =0.5p，Wp =0.6p M=32;Wp=0.6*pi; m=0:(M+1)/2; Wm=2*pi*m./(M+1); %mtr=ceil(Wp*(M+1)/(2*pi)); Ad=[Wm>=Wp];%Ad(mtr)=0.28; Hd=Ad.*exp(-j*0.5*M*Wm); Hd=[Hd conj(fliplr(Hd(2:M/2+1)))]; h=real(ifft(Hd)); w=linspace(0.1,pi,1000); H=freqz(h,[1],w); plot(w/pi,20*log10(abs(H)));grid;