1 X T Sin 6200 7 7d4 Sin 5800 Na 1d4 Sinc 800t Cos 6000 74 Od4 Is A Qam Quadrature Amplitude Modula 1 (89.75 KiB) Viewed 35 times
1 X T Sin 6200 7 7d4 Sin 5800 Na 1d4 Sinc 800t Cos 6000 74 Od4 Is A Qam Quadrature Amplitude Modula 2 (62.04 KiB) Viewed 35 times
1. x(t) = (sin(6200 7 + 7d4) + sin(5800 na + 1d4)] + sinc(800t) cos(6000 74 + od4) is a QAM (quadrature amplitude modulation) signal. The I-phase message signal in x(t) is sinc(800t). x(t) is to be demodulated using a coherent QAM demodulator. (a) Determine the local carrier signal and the lowpass filter bandwidth to be used in the I-phase of the QAM demodulator. (5 Marks) (b) Sketch the amplitude spectrum of x(t) and use it to deduce the lowpass filter bandwidth required to demodulate the Q-phase message signal. (8 Marks)
(C) Determine the Q-phase demodulator output signal expression. (5 Marks) (d) Is the answer to part (c) unique, i.e., can part (c) have multiple answers? Explain why. (4 Marks) (e) If the communication channel is a white noise channel, explain whether the I-phase or Q-phase demodulator output will have more noise. (Note: No need to calculate SNR.) (3 Marks)
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