Consider the following discrete-time signal 1 where f = 1 and f 128 where fe = 50 128 (c) = x[n] = cos(2fn) + cos(2fn) modulates the amplitude-modulated carrier signal 5 128 xe[n] = cos(2nfcn) The resulting amplitude modulated signal is Xam[n] = x[n]x[n] (a) Using MATLAB, plot the signals x[n], xe[n] and xam [n], for 0 n 511 (b) Compute and plot the 128-point DFT of the signal xam [n] for 0 n 127 Compute and plot the 128-point DFT of the signal xam [n] for 0 n 99 (5 marks) (5 marks) (5 marks) (d) Compute and plot the 1028-point DFT of the signal xam [n] for 0 n 1023. Comment on your results viz Parts (b) and (c). (10 marks)