Question

Generate a baseband message signal m(t) to be a square waveform of duration 120 msec and amplitude
1 V. The sampling frequency is -
= 10 . Use a carrier of amplitude 1 and frequency 600 Hz and
perform the following modulation/demodulation operations:
1. DSB-SC
a. modulation of the message signal m(t)
b. coherent demodulation, assuming that the local carrier @ the receive-side is perfectly
synchronized in frequency and phase with the transmit-side carrier.
c. lowpass filtering of the demodulated output and signal recovery
( )
2. AM
a. modulation
b. noncoherent demodulation (for ex. you can use a rectifier)
c. lowpass filtering of the demodulated output and signal recovery
( )
3. SSB-SC
a. modulation (using Hilbert transform method preferred)
b. coherent demodulation, assuming that the local carrier @ the receive-side is perfectly
synchronized in frequency and phase with the transmit-side carrier.
c. lowpass filtering of the demodulated output and signal recovery
( )
For each modulation scheme, calculate the energy of the estimation error : () = (
( ) −
( ))


over the signal’s duration T, and compare all modulation schemes.
Plot in both time and frequency domains:
1. Message signal.
For each of the 3 above cases you should plot in both time and frequency domains:
2. Modulated signal.
3. Demodulated signal.
4. Recovered signal
( ).
You will need to design the proper FIR lowpass filter (LPF) (filter order and cutoff frequency), to filter
the demodulated signal, and produce the recovered signal
( ).
For your report, please create a word document to include all results and Matlab plots and code.

Answer 1