L26 - If the carrier signal oscillates much faster than...

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We do not have identical copies any more due to the undesired "frequency overlap" after multiplying . The original signal is even before demodulation.
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We have three frequency parameters to choose in this AM system.
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Usually given by the government (FCC). Need to purchase "licence" to use certain frequency-band. Different frequency bands will have different price, depending on the transmission range, bandwidth, channel quality, etc. Choose it to be equal to or sightly larger than
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The receiver has to have a carrier signal that is "synchronous" (or equivalently "phase coherent" to the cosine signal used in the transmitter.
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Unformatted text preview: If the carrier signal oscillates much faster than x(t), then x(t) is the "envelope" of the wave form, which can be obtained by "half-wave rectification" (see p. 590-594). (1) Quality loss due to half-wave rectification (2) Cannot take negative signals. Namely, However, since the "phase" at "t>0" changes, a shnchronous detector knows that the signal changes from x(t)= -1 for t<0 to x(t)=1 for t>0. What is the "price" of adding some DC component? Ans: We need additional transmission power at the radio station. Note: Nowadays, asynchronous demodulation is seldom used....
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L26 - If the carrier signal oscillates much faster than...

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