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Unformatted text preview: EE132A, Spring 2009 Communication Systems Prof. John Villasenor Handout# 5 TA: Pooya Monajemi, Erica Han Homework 2 Assigned: Monday, April 6, 2009 Due: Monday, April 13, 2009 Reading Assignment: Proakis & Salehi, chapter 3 (sections 3.1, 3.2, 3.3), and chapter 4 (sections 4.1, 4.2, 4.3). 1. Overmodulation . Consider the AM signal s(t) = A c (1 + k a A m cos(2 f m t)) cos(2 f c t) where the message signal m(t) = A m cos(2 f m t) is transmitted using basic AM. (a) Find the values of = k a A m for which overmodulation is avoided and m(t) may be received correctly by an ideal envelope detector. (b) Suppose that = 2. The choice of causes significant overmodulation. Sketch the signal v(t) that would be produced by an ideal envelope detector receiving this overmodulated signal. Include at least one full period of m(t) in your sketch. Identify the regions where overmodulation has caused the signal to be received improperly and label the time instants that bound these regions. the signal to be received improperly and label the time instants that bound these regions....
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- Spring '09