half_band_2.m

设计一个半带滤波器

%2倍的半带滤波
function h_band_2=half_band_2(reg)
reg=[0 0 0 0 0 0 0 0 0 0 0 1];
x=Rcos_squ_4(reg);
y(1,1:8192)=upsample(x(1,1:4096),2);   %I路信号2倍内插
y(2,1:8192)=upsample(x(2,1:4096),2);    %Q路信号2倍内插

half_band_2=[-0.031303406,0.000000000,0.281280518,0.499954224,0.281280518,0.0000000000,-0.031303406]; % 2阶半带滤波器的系数矩阵
h_band_2_I=filter(half_band_2,1,y(1,1:8192));
h_band_2_Q=filter(half_band_2,1,y(2,1:8192));

h_band_2=[h_band_2_I;h_band_2_Q];
H_BAND_2_I=fft(h_band_2_I);
H_BAND_2_Q=fft(h_band_2_Q);

figure(4);
subplot(2,2,1);
stem([1:8192],h_band_2_I);axis([1 600 -0.7 0.7]);
xlabel('n');ylabel('h__band__2__I');title('I路信号2倍内插后半带滤波');grid;

subplot(2,2,2);
stem([1:8192],h_band_2_Q);axis([1 600 -0.7 0.7]);
xlabel('n');ylabel('h__band__2__Q');title('Q路信号2倍内插半带滤波');grid;

subplot(2,2,3);
n=[1:8192];
plot(2*n/8192,abs(H_BAND_2_I));axis([0 2 -20 170]);
xlabel('frequency(*pi)');ylabel('H__BAND__2__I');title('I路信号2倍内插半带滤波频谱');grid;

subplot(2,2,4);
n=[1:8192];
plot(2*n/8192,abs(H_BAND_2_Q));axis([0 2 -20 170]);
xlabel('frequency(*pi)');ylabel('H__BAND__2__Q');title('Q路信号2倍内插半带滤波频谱');grid;