Say we set the carrier frequency to fc 12 khz then

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Unformatted text preview: the positive frequency part of the magnitude of the DFT of x vs. CT frequency f, and verify that the signal has CT bandwidth B = 5 kHz. (b) Increasing the sample rate to avoid aliasing: In order to simulate AM we need to use a carrier frequency > 2B = 10 kHz. Say we set the carrier frequency to fc = 12 kHz. Then the highest frequency in the AM signal is 12+5 = 17 kHz, so to avoid aliasing in the AM signal we need a sample rate of at least 34 kHz. But we are going to use an envelope detector receiver. Recall from class that this nonlinear system generates harmonics of the input frequency, so at the envelope detector output we will see terms at center frequencies 0, 12 kHz, 24 kHz, 36 kHz, etc. We have to sample fast enough that the harmonics do not cause significant aliasing in the signal at the receiver output. Harmonics beyond the third (that is, the term with center frequency 36 kHz) are quite small...
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