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Unformatted text preview: Lecture S17 Muddiest Points General Comments Today, we began talking about amplitude modulation (AM). We looked at double sideband / suppressed carrier amplitude modulation. We also looked at coherent demodulation of AM-DSB/SC signals. Responses to Muddiest-Part-of-the-Lecture Cards (7 cards) 1. So the reason you can’t make [an ideal low-pass filter] is because the inverse Fourier transform is noncausal? (1 student) Exactly. The impulse response of an ideal low-pass filter is a sinc function, which is noncausal, and therefore cannot be implemented in real time. 2. Why did we start with x ( t ) just to end up with x ( t ) [when we were doing modulation and demodulation]? (1) The point is that we modulate the signal in order to allow it to be transmitted via radio frequency waves. At the receiving end, we demodulate the signal, and of course hope to recover the same x ( t ) that we used as a modulating signal to begin with....
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This note was uploaded on 01/28/2012 for the course AERO 16.01 taught by Professor Markdrela during the Fall '05 term at MIT.
- Fall '05