ECE405HW2Su2010 - ECE 405 HOMEWORK #2 SUMMER 2010 DR. JAMES...

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ECE 405 HOMEWORK #2 SUMMER 2010 ©DR. JAMES S. KANG 1 A message modulates a carrier () () 2 sinc mt t = ( ) 2cos 2 10 t π . (a) Find the Fourier transform of m(t) and plot it. (b) Sketch the two-sided spectrum of the modulated waveform when the modulation is (1) AM (2) DSB–SC (3) LSSB (4) USSB (c) Sketch the modulated waveform in the time domain when the modulation is (1) AM (b) DSB–SC 2 The system shown below can be used to send two messages on one carrier. (a) If and () ( ) 1 cos 2 1000 t = ( ) ( ) 2 cos 2 4000 t = , find the output y(t). (b) Device block diagram for a suitable demodulator for y(t). Lowpass filter at 100 kHz Highpass filter at 100 kHz m 1 (t) m 2 (t) cos(2 π×10 5 t) y(t) + + Σ 3 Sketch the spectrums X(f) and Y(f) in the system shown below. m(t) x(t) y(t) M(f) X(f) Y(f) Lowpass filter at 1 kHz 2cos(2 3 t) M(f) 0 –1 1 f (kHz) 4 Sketch the spectrums and () Yf ( ) Z f in the system shown below. x(t) y(t) Lowpass filter at 25 kHz z(t) π×3 0,000 t) 1
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X(f) 0 45 50 55 f (kHz) –55 –50 –45 1 5 A message m(t) and its Fourier transform ( ) M f is shown below. This message is applied to a system shown below.
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This note was uploaded on 08/09/2010 for the course ECE ECE 405 taught by Professor Jameskang during the Summer '10 term at Cal Poly Pomona.

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ECE405HW2Su2010 - ECE 405 HOMEWORK #2 SUMMER 2010 DR. JAMES...

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