调幅广播

开始一个有限带宽的信号.

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a = BandpassFilter[ AudioNormalize@ AudioResample[Import["ExampleData/rule30.wav"], 96000], {Quantity[ 10, "Hertz"], Quantity[5000, "Hertz"]}, 201]

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Periodogram[a, 2000, ImageSize -> Small, PlotRange -> {{0, 10000}, All}]

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用 22,050 Hz 正弦波调整振幅将内容移动至频谱的最高点. 对于大部分人应该听不见结果.

In[3]:=

amsignal = ((.5 + a) AudioGenerator[{"Sin", Quantity[22050, "Hertz"]}, Duration@a])/2

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Periodogram[amsignal, 2200, ImageSize -> Small]

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通过将结果再乘以另外相同相位的 22,050 Hz 正弦波，将调幅信号解调.

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result = BandpassFilter[ amsignal*AudioGenerator[{"Sin", Quantity[22050, "Hertz"]}, Duration@amsignal], {Quantity[100, "Hertz"], Quantity[5000, "Hertz"]}, 201]

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使用非线性滤波器将调幅信号解调.

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BandpassFilter[# - Mean@# &@ MaxFilter[amsignal, 4], {Quantity[100, "Hertz"], Quantity[5000, "Hertz"]}, 201]

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