Digital Signal Processing Reference
In-Depth Information
predominantly the 4 KHz signal and note down the voltage levels
of both the signal components.
6.3.2
Signal Demodulation Applications
Exercise 3: Filtering of amplitude modulated (AM) signal to recover the
baseband signal
a. Simulate the AM
modulation
system,
3
as shown in Figure 6.6a, using
MATLAB or Simulink. Check the AM output at the carrier, and two
sideband frequencies.
b. Simulate the AM
demodulation
system, as shown in Figure 6.6b, using
MATLAB or Simulink. The output of the multiplier will consist of
both high frequency and low frequency signal components. Sample
the multiplier output by passing it through the sample and hold
circuit, at the Nyquist sampling rate corresponding to the highest
frequency, which would be the higher sideband frequency.
c. Design a digital low-pass filter having a cutoff frequency slightly
higher than 2 KHz, which is the frequency of the input baseband signal.
Carrier signal
(10V, 50 kHz)
AM
output
+
X
Modulating
signal (0.1V, 2
kHz)
(a)
AM signal
Digital
lowpass
filter
Sample
and Hold
circuit
X
Carrier signal
(10V, 50 kHz)
Baseband
output
(b)
FIGURE 6.6
(a) Model for amplitude modulation system; (b) model for amplitude demodulation system.
