plotspec.m

来自「很全的通讯理论书籍源码」· M 代码 · 共 21 行

function [freq,specdB]= plotspec(spec,Fs,Nsmp,N);
%----------------------------------------------
nspec = spec / max(spec);
nspec = fftshift(nspec);
nspec = filter(ones(11,1)/11,1,nspec);
nspec = [nspec(6:end); nspec(1:5)];
nspec = nspec(length(nspec)/2:16:end);
nspec = nspec / max(nspec);

%freq = [-N*Nsmp/2: N*Nsmp/2-1]/(N*Nsmp) * Nsmp*Fs;
freq = [0: 16: N*Nsmp/2]/(N*Nsmp) * Nsmp*Fs;
ind = min(find(freq>4));
freq = freq(1:ind);
specdB = 10*log10(nspec(1:ind));
plot (freq, specdB,'g')
xlabel('Frequency (kHz)')
ylabel('Spectrum (dB)')
grid
axis([0 3 -60 10]);