A full AM (DSB-LC) has s(t) = 10[1+ k, m(t)] cos ( 2 10 t) where m(t) = A cos (2n-10 t) and k, = 0.2: a) Find and draw S(f). b) What is the maximum allowable value for Am. c) Find the average power in the carrier and sidebands if Am-2V. d) Draw a circuit diagram for the switching modulator and the envelope detector. Q2 A DSB-SC signal is given by s(t) = Ac m(t) cos (2 x fc t): a) Draw a circuit diagram for the ring modulator which generates this s(t). b) If m(t)- Am cos (2 fm t), find the Fourier transform of s(t) and draw its spectrum. c) Draw a block diagram for the Costas receiver (demodulator). d) If s(t) is demodulated by multiplying it by cos [ 2 (fe+ Af)t +0] and then passed through a LPF, find the signal at the output of the LPF. Q3 A SSB signal is given by s(t) = Ac m(t) cos ( 2 z f. t) + Ac m (t) sin (2 xf, t) where m (t) is the Hilbert transform of m(t). a) Draw a block diagram to generate s(t). b) If m(t) - Am cos (2 x fm t) and m(t)= A sin ( 2 z fm, t), Show that s(t) is reduced to a single sinusoidal term. Find and draw ihe Fourier transform of s(t). Q4 a) Two signals m(t) and m(t) are transmitted using quadrature amplitude modulation (QAM) with s(t) = Ac m(t) cos ( 2 f, t) + Ac m(t) sin (2 x f, t). Draw a block diagram for the modulator and show how to recover m(t) and m(t). b) Three signals m (t), m(t), and m(t) are multiplexed using frequency division multiplexing (FDM) with carrier frequencies fet, fe2, and fe. Write expression for the signal at the output of the multiplexer s(t), draw its spectrum, and draw a block diagram for the FDM demultiplexer.