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Signal Modulation

  1. Oct 16, 2004 #1
    How come a signal modulated using Amplitud Shift Keying and/or Phase Shift Keying (such as QAM) require a bandwidth? I mean, since the frequence is constant; only the amplitude and phase is changed.

    Thanks in advance!
  2. jcsd
  3. Oct 16, 2004 #2


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    It is not constant! The slope dV/dT changes from that of the unmodulated sine wave. This means that for a small periods of time it is different frequencies.
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