Question

7. [20 points] Two signals mi(t) and m2(t) shown in the figure below have to be transmitted simul taneously over a channel by multiplexing. The signal at point b is the multiplexed signal, which modulates a carrier of frequency 20 kHz. The modulated signal at point c is then transmitted over the channel. (a) Sketch the spectra of the signals at points a, b and e An Mar) 42 2 cos(20, 000mt) (b) What must be the bandwidth of the distortionless channel? (c) How can you design a receiver to recover mi(t) and m2(t) from the modulated signal at point c

Answer 1

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-1250-(abo -7500 -5000-2500 250。500 7500 10,O00 12500 Sjmal as reint s Signat at point e m, (f)(2Cos (40,000자)) +m(t)12 Co th (t))(2 Cas 60,000 2 ne 2ac00) )n (990)

(f+io00 n(f-10000) 0006 "190 เ0000 1190 5000 1750 2000 22 São 250 o ZSo 3000 32 500

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