Digital Signal Processing Reference
In-Depth Information
Exercises on Chapter 13
Exercise 1
(d)
Describe the possibilities of limiting a digital signal - i.e. a bit pattern - in frequency
before modulation and transmission.
(e)
How can overlapping by adjacent pulses (interference) be limited?
(f)
How is it possible to determine qualitatively using measuring techniques whether
the information of a received signal can be reconstructed?
(g)
Why are many filter types not suitable for filtering "rectangular" bit sequences?
Exercise 2
Summarize the general differences between classical and digital modulation processes.
Exercise 3
Compare amplitude, phase and frequency key-shifting.
(a)
What advantages and disadvantages do you see?
(b)
What is the easiest way to transform an ASK into a PSK?
Exercise 4
Describe the idea behind the (two-dimensional) signal space in the GAUSSian plane.
Exercise 5
Describe using the four phase-key shifting QPSK how practically every point in the signal
space can be reached.
Exercise 6
In digital quadrature amplitude modulation QAM any number of points arranged in
grid-form can be reached in the signal space using a mapper.
(a)
Describe its fundamental structure
(b)
How many signal states (points in the signal space) are needed for a 4 bit signal at
the input?
(c)
How can this be realized in terms of circuits in mapper?
(d)
How many discrete amplitude levels are required by the real and imaginary part of
a signal?
Exercise 7
From the representation of the QAM reception signal it can be determined exactly
whether the source signal can be reconstructed.
(a)
How can this be seen
(b)
On what principle does a QAM receiver work?
