Digital Signal Processing Reference
In-Depth Information
primary basic group formation according to Illustration 166. What are the
programme limitations of DASY
Lab
for simulation with reference to the creation
of secondary, tertiary and quaternary basic groups?
Exercise 5 Mixing
(a)
Design and simulate an AM tuner according to Illustration 168. You will have to set
the sampling rate at roughly 2 MHz and the blocklength at at least 1024.
(b)
Afterwards create a realistic AM signal in the medium wave range from 525 to 1645
kHz which you superimpose on noise. Try to retrieve and demodulate the
corresponding AM signal. Tip: make sure there is a favourable relationship between
the signal and the level of noise.
Exercise 6 Frequency modulation FM
(a)
Familiarise yourself with the function of the FM generator according to Illustration
169.
(b)
How can you set the FM mid-frequency and frequency swing in the module “source
signal” (without using a manual regulator)? In these experiments select a sinusoidal
source signal.
(c)
Vary the frequency swing and the mid-frequency according to Illustration 169 using
a manual regulator. Extend the circuit.
(d)
Examine the composition and the influence in the frequency domain of the
frequency swing, the frequency of the source signal and the FM mid-frequency
on the width of the FM spectrum.
Exercise 7 Demodulation of FM signals
(a)
Try to demodulate an FM signal on the edge of a lowpass filter
(b)
Try to demodulate an FM signal with the same cutoff frequency as (a) on the edge
of a highpass filter. How do the results differ?
(c)
Repeat (a) and (b) with a realistic source signal (filtered noise).
(d)
Design a phase detector according to Illustration 179.
(e)
Try to replicate the experiment carried out in Illustration 180.
(f)
On your own design a PLL as in Illustration 181 and try to set the control voltage
for the VCO in such a way that the PLL works.
Exercise 8 Difference between PM and FM
(a)
Develop the circuit corresponding to Illustration 182 and carry out the comparison
of PM and FM yourself.
(b)
Give reasons for the differences in the immunity to interference of PM and FM.
(c)
Why are
preemphasis
and
deemphasis
used in the case of FM.
