TELECOMMUNICATION ENGINEERING MASTER
COMMUNICATION SYSTEMS AND CIRCUITS LAB
PRACTICE 1. Instrumentation.
INTRODUCTION.
This practise is focused on the basic equipment of the radiofrequency and
microwave lab. This equipment will be used for implementing the design and
testing the results of some of the following practises.
The basic operation of the following equipment will be learnt in this practise:
• Oscilloscope. It is used for visualizing signals in the time domain. Also, it
incorporates an FFT function to obtain a basic representation of signals in
the frequency domain.
• Programmable function generator. It is used for generating pre-defined
basic function signals and some basic modulations. Also, it includes a USB
communication system intended to receive more complex signals
programmed in a computer. In the lab, we will use firstly the application
provided by the manufacturer and, in a next practise, we will use MATLAB
(with the required toolbox) to obtain any waveform generated by signal
processing as an output.
• High-frequency function generator. It is used for generating signals in the
GHz range and, because of the high frequency, the appropriate interfaces
are required to connect the equipment with microwave circuits.
• High-frequency spectrum analyser. It is used for visualizing signals in the
frequency domain with an appropriate quality of representation and
reaching microwave frequency range. A huge set of parameters can be
properly represented by the equipment depending on the properties of the
signal and on the type of analysis to be implemented.
• Network analyser. It is used for analysing N-port systems and obtaining
typical parameters at microwave systems as the Smith chart or the
scattering parameters.
DESCRIPTION.
First, a brief description and a basic operation example of the equipment are given
by the lecturer. Then, and after revising the equipment handbooks, some
experiments are required:
• Basic signal representation. The signals to be represented are sinusoidal,
squared, triangular and sync periodic functions. Check that time and
frequency measures match with the parameters of the function generator.
Be focused on evaluating the amplitude of each Dirac function in the
frequency domain and the relation between the obtained representation
and the theoretical frequency transform.
• Representation of modulations. The function generator is able to provide
different modulations. For each available modulation (and with the
appropriate parameters), draw the time and frequency domain
representation and check that the obtained measures are in consonance
with the generated parameters.
• Generating arbitrary waveforms with the ArbWaveExpress application.
Using the ArbWaveExpress program, generate arbitrary waveforms with
the drawing option (utilizing the mouse or a set of points). Once stored in
the appropriate format, the data will be sent to the function generator to
be visualised and measured. Pay attention to the representation of
discontinuities and Dirac functions in the time domain and to the matching
between the defined and measured signals.
• Generating equation-defined waveforms with the ArbWaveExpress
application. Using the ArbWaveExpress program, generate waveforms
with equation editor. Design mixed signals (multiplication) to check the
behaviour in the frequency domain. Generate digital waveforms
(pseudorandom sequences of bits) to analyse the obtained spectrum.
• Representation of high frequency modulations. The high frequency
function generator is able to provide different modulations. For an
amplitude and a frequency/phase available modulation (and with the
appropriate parameters), draw the time and frequency domain
representation and check that the obtained measures are in consonance
with the generated parameters.
EVALUATION.
The main topics to be evaluated are:
• The representation in the oscilloscope and the spectrum analyser of the
generated signals.
• The measured parameters in the time and frequency domain for each
signal. For example, the amplitude of each Dirac function for a squared
periodic signal; the bandwidth and the modulation index for an amplitude
modulation; the bandwidth and the time resolution obtained for a sync
periodic function, etc. As can be seen, the evaluation includes the selection
of the appropriate parameters for each signal.
• Programming and generating signals with the ArbWaveExpress application
and the visualization of the proper parameters.
The evaluation will be held in an individual exam at the lab.
TIMING.
This practise is estimated to be accomplished in three hours at the lab.
