Digital Signal Processing Reference
In-Depth Information
Carrier Signal
(10V, 50 kHz)
Spectrum
Analyzer
+
X
Modulating
Signal (0.1V, 2
kHz)
FIGURE 3.8
Model of Amplitude Modulation (AM) system.
Set the frequency of the signals to 1 MHz (11 kHz for the triangular wave)
and the amplitude to 1 V. Compute the Fast Fourier Transform (FFT) of each
of the periodic signals using an output resolution of
∆
f =
1 MHz. (The FFT
can be implemented in MATLAB, see
Section 3.1.3
.
) Obtain the exponential
5 (from the FFT) for each of the above
waveforms. The power contained in the Fourier coefficients is given as
follows:
Fourier series coefficients
c
n
, 1
≤
n
≤
Pc
n
, comp
=
c
n
2
(mW)
Exercise 3: Simulation of Amplitude Modulation (AM) signals
Simulate the AM system, as shown in Figure 3.8, using MATLAB or Sim-
ulink. The power contained in the Fourier coefficients is given as follows:
Pc
n
, comp
=
c
n
2
(mW)
Calculate the power spectrum of the carrier and two sidebands in the AM
signal.
3.4
Hardware Laboratory
Exercise 4: Measurement of harmonic distortion in signal generators
Connect the output of the HP 3324A Synthesized Generator to the input of
the HP 8590L Signal Analyzer as shown in
Figure 1.8
. Set the frequency of
the generator to 1 MHz (11 kHz for the triangular wave) and the amplitude
to 1 V. Measure the power spectrum (dBm) for each of the above signals to
include the fundamental (1 MHz) and first four harmonics.
