用matlab仿真SAR ADC的SNR的相关问题

dc33912345

学习了论坛中maxim的代码，对其中求FFT的谐波的频率和功率时的一段代码有点疑问：


%Find harmonic frequencies and power components in the FFT spectrum
for har_num=1:10
%Input tones greater than fSAMPLE are aliased back into the spectrum
tone=rem((har_num*(fin-1)+1)/numpt,1);
if tone>0.5
%Input tones greater than 0.5*fSAMPLE (after aliasing) are reflected
tone=1-tone;
end
Fh=[Fh tone];
%For this procedure to work, ensure the folded back high order harmonics do not overlap
%with DC or signal or lower order harmonics
har_peak=max(spectP(round(tone*numpt)-spanh:round(tone*numpt)+spanh));
har_bin=find(spectP(round(tone*numpt)-spanh:round(tone*numpt)+spanh)==har_peak);
har_bin=har_bin+round(tone*numpt)-spanh-1;
Ph=[Ph sum(spectP(har_bin-1:har_bin+1))];
end

请问这一句“tone=rem((har_num*(fin-1)+1)/numpt,1)” 是怎么实现“Input tones greater than fSAMPLE are aliased back into the spectrum(把大于fsample的输入分量混叠回频谱)”的。

dc33912345

dd自己