Assignment-II_Q

# Assignment-II_Q - Q1. (i) (ii) (iii) (iv) EE3008 Principles...

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- 1 - EE3008 Principles of Communications Assignment 2 Q1. For the sinusoidally modulated DSB-C AM waveform shown in Fig.Q1, the modulating carrier frequencies are f m and f c , respectively. It is known that the modulation index is given by m = 0.7. (i) Find the value of B in Fig.Q1. (ii) Find the power efficiency of φ AM ( t ) . (iii) Give the mathematic expression AM ( t ) for the modulated signal. (iv) Find the frequency spectrum of AM ( t ). Specify the frequencies and amplitudes of the frequency components. F i g . Q 1 F i g . Q 2 Q2. Fig. Q2 shows the frequency spectrum F ( f ) of a message signal f ( t ). The message signal is applied to a DSB- SC AM modulator of carrier signal A c cos ω c t . (i) Sketch the spectrum of the modulated signal at the modulator output. Specify the frequencies and amplitudes of the modulated signal. (ii) If the modulated signal is multiplied by cos 2 c t again, sketch the new spectrum. Q3. The sinusoidal signal f(t)=Acos(2 π f m t ) is applied to the input of a FM system. The corresponding modulated
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## This note was uploaded on 01/11/2011 for the course EE 3008 taught by Professor Pingli during the Fall '08 term at City University of Hong Kong.

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