3 4 Here a sine wave information signal is modulating a sine wave carrier but

3 4 here a sine wave information signal is modulating

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Percentage of Modulation Amplitude Modulation Fundamentals 97 m
to compute the modulation index from measurements taken on the composite modulated wave itself. When the AM signal is displayed on an oscilloscope, the modulation index can be computed from and , as shown in Fig. 3-5. The peak value of the mod- ulating signal is one-half the difference of the peak and trough values: As shown in Fig. 3-5, is the peak value of the signal during modulation, and is the lowest value, or trough, of the modulated wave. The is one-half the peak-to-peak value of the AM signal, or Subtracting from produces the peak- to-peak value of the modulating signal. One-half of that, of course, is simply the peak value. The peak value of the carrier signal is the average of the and values:

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