是属于清华大学出的书 数字信号处理及电子课件光盘内容

				%  ex_07_03_2.m :  习题 7.3
				
				clear all;
				fl=pi/6;fh=pi/3;N=29;
				factor=(N+1)/2;m=factor*fl/pi;
				m=floor(m);m2=factor*fh/pi;m2=ceil(m2);
				j=sqrt(-1);
				for k=0:(N-1)
				       if((k=(N-m))||((k>=m2)&&(k				            a=-j*(N-1)*k*pi/N;
				            H(k+1)=exp(a);
				       else
				            H(k+1)=0;
				       end
				end;
				for i=0:(N-1)
				      s=0;
				      for k=0:(N-1)
				         a=j*2*pi*i*k/N;
				         s=s+H(k+1)*exp(a);
				      end
				      h(i+1)=s/N;
				end
				h=real(h);h1=freqz(h,1,N);
				t=0:0.5/N:0.5-0.5/N;
				figure('color','w');
				subplot(221);plot(t,abs(h1));grid;