ECS204                                                                 Course: Signals and Systems
Jan-Apr 2025                                                                   IISER Bhopal
HW8
1. State the similarities and differences between
    (a) Convolution of continuous-time signals and Convolution of discrete-time signals
    (b) Fourier transform of continuous-time signals and Fourier transform of discrete-time
        signals
    (c) Fourier transform of continuous-time periodic signals and their corresponding Inverse
        Fourier transforms
    (d) Fourier transform of discrete-time periodic signals and their corresponding Inverse Fourier
        transforms
    (e) Fourier transform of continuous-time aperiodic signals and their corresponding Inverse
        Fourier transforms
     (f) Fourier transform of discrete-time aperiodic signals and their corresponding Inverse
         Fourier transforms
2. A message signal x(t) = cos(4π10t) is used to modulate a carrier c(t) = cos(2π103 t) in
   an Amplitude Modulation (AM) system. Calculate the frequency content in the modulated
   signal.
           X1 (ω)                              X2 (ω)                               X3 (ω)
               1.5                                1.5
                                                                                       1
                                                   0.5
   −10π           10π      ω           −8π            8π       ω            −12π           12π      ω
                      Figure 1: Spectrum of three signals x1 (t), x2 (t), x3 (t)
3. Consider Figure 1. Construct an Frequency Division Multiplexing system to transmit three
   signals x1 (t), x2 (t), x3 (t) respectively using carriers ck (t) = cos(22k π103 t), k = 1, 2, 3. Pro-
   vide a scheme to demodulate and receive the three signals x1 (t), x2 (t), x3 (t) at the receiver.
4. Construct a Time Division Multiplexing system to transmit three signals x1 (t), x2 (t), x3 (t)
   respectively using pulse trains of appropriate ∆ and time-period T . Provide a scheme to
   demodulate and receive the three signals x1 (t), x2 (t), x3 (t) at the receiver.
5. What should be the sampling frequency if one were to sample each of the time-domain signals
   x1 (t), x2 (t), x3 (t) whose spectrum is shown in Figure 1? What type of filter would you use
   to reconstruct the signals from its samples?