TAMPEREEN TEKNILLINEN YLIOPISTO
TAMPERE UNIVERSITY OF TECHNOLOGY
COMM.SYS.800
Telecommunication Laboratory Course
2022 onwards
Network analyzer work
Lab:TC407
Ari Asp ari.asp@tuni.fi
INTRODUCTION
You can find the information you need for the pre-lab part in the following books Hewlett &
Packard: "Back to Basics" (later referred as B to B) /can be found in the shelf of TLT-LAB/
Rohde&Schwarz (Michael Hieber): Fundamentals of Vector Network Analysis
Also Lehto/Räisänen: "Mikroaaltomittaustekniikka" is quite useful.
1
PRE-LAB ASSIGNMENT
1.1 Draw a block diagram of a network analyzer and explain operating principle.
What can you measure with a network analyzer?
1.2 What are the different sources of measurement errors and calibration
(=measurement calibration or work calibration) methods? (B to B p.64).
Explain the calibration principle, i.e. how calibration corrects measurement
errors (B to B p.71).
1.3 What is definition of the following terms? Frequency response, 3dB
bandwidth, quality factor, insertion loss/gain, phase response, group delay,
rejection, 1-dB compression point.
2
MEASUREMENTS
Measurements are carried out by Rohde & Schwarz ZVL network analyzer. Measurement range
is from 9 kHz to 6 GHz. You should familiarize yourself with the theory of network analysis,
network analyzer and other equipment used in the measurements before starting the lab.
For calibration we use the kit HP 85032B.
In this lab we measure characteristics of different circuit elements
Amplifier Mini Circuit ZFL-1000 (with the power supply)
Attenuator Mini Circuit NAT-20
Terminator Mini Circuit NTRM-50
70 or 71 MHz band pass filter
Network analyzer basic use (check ZVL quick start guide page 43 onwards)
CAL menu is a very important one, especially at the beginning of the measurements, and also
when the reference level of calibration (reference plane) changes, (mainly as a result of
change in electrical length).
At the beginning of measurements you must always perform measurement calibration, which is
usually done using a calibration kit. There are different kits for different connector types.
Look at (for example): ZVL quick start page 45.
By performing the standard measurements (measurement of the known loads): “open”, “short”,
“load” and “through” the analyzer can find the error parameters in the error model and
compensate for different error sources. By pressing CAL button -depending on what we are
measuring - the equipment suggests different calibration methods (quick start page 93).
For example, by pressing One Port the equipment asks you to connect different standards to
be measured, and then calculates correction coefficients at the end of the measurements.
Perform the measurements always at the calibration reference plane; in other words don’t
connect any adapter between the calibration reference plane and the equipment to be
measured. If you doubt the measurement results, perform calibration again.
Note: press “Preset” button before new series of measurements to negotiate
effect from previous particular calibrations.
2.1 Transmission- and reflection measurements
Let’s examine the effect of the cable length on the accuracy of the
calibration/measurements.
Connect the Mini-Circuit 50  terminator directly to the reflection Port 1 and measure the
reflection, check the Smith Chart format.
Connect a piece of cable (almost 30 cm long) with the suitable connector for terminator to the
reflection Port 1, connect Mini-Circuit 50  terminator to the end of the cable and check the
reflection.
Perform the calibration (normalization) for Port 1 with a cable (press CAL and One Port).
Connect terminator to the end of the cable and check the reflection again.
Compare results. How did the measurement result change?
Is the value of the terminator 50  in the 9 kHz – 6 GHz range?
(don’t forget to press ‘Preset’ button after finishing 2.1)
2.2 Measure the reflection and transmission of Mini-Circuit 20 dB attenuator.
Measure Reflection and Transmission, what can you say about the reliability
of the results; especially about Transmission measurement?
2.3 Perform One-Path Two-Port calibration with the cable (choose ideal kit in
the calibration menu and use the usual cable as a through) and measure
once more. Compare the results.
(don’t forget to press ‘Preset’ button after finishing 2.3)
2.4 Measure the 3dB bandwidth and amplification of the Mini Circuit ZFL-1000
amplifier.
2.5 Measure the frequency response, 3 dB bandwidth, quality factor, insertion
loss, group delay, phase response, rejection, etc. of 70 MHz band pass
filter.
Note, that you can measure the parameters above in different manners, for example using a marker or directly.
2.6 Research of antenna using Network Analyzer
Work is performed using the Network Analyzer ZVL, laboratory layout with the wire simple
wire antenna for 2.1 GHz, because it is a range for 3G UMTS and CDMA communication
systems. The aim of the work is to familiarize with the main antenna parameters.
Antenna is a device that couples electrical current into electromagnetic waves and radiates it
into the free space (the transmitting antenna) or receives radio frequency energy of free
oscillations and converts it into energy of electromagnetic waves for the input of the receiver
(the receiving antenna).
Transmitting and receiving antennas have the reciprocity property, i.e. the same antenna can
radiate or receive electromagnetic waves and in both modes it has the same properties and
parameters.
Important parameters characterizing the antenna systems efficiency are the reflection
coefficient from the input, standing wave ratio (SWR) and the input impedance of the antenna
(its active and reactive parts). These parameters are the same for the both antenna modes –
transmission and receiving.
Any antenna can be represented as a two-port microwave device and the SWR can be defined
in terms of the scattering matrix elements or by using the regular transmission line
mathematical model.
On a regular part of any transmission line field is a superposition of incident and reflected
waves. The incident wave running from the generator to the load, the reflected wave
generated by the load or tract heterogeneity (inhomogeneity) and running towards the
incident wave. Any incident wave component depends from the longitudinal coordinate  such as
e −i ,

any reflected wave component – such as
propagation ratio,  – damping coefficient,
 =
2

ei ,

where
 =  − i
– the complex
- phase coefficient.
In the transmission line mathematical model the vector functions of the field distribution in
the line are replaced by integral (averaged) electromagnetic field measures. There are the
equivalent normalized voltages of the incident and reflected waves. Phases of the normalized
voltages are taken as equal to the phases of the electric field transverse components for the
corresponding waves. The transverse electric field components ratio for the incident and
reflected waves in the same point of the cross section is called the electric field reflection
 =
coefficient 
E
E tref
, and the normalized voltages ratio is called the reflection coefficient,
E
tinc
 =  . With the simultaneous existence of incident and reflected wave, power in
and always 
E
the cross section is defined as
2
P = Pinc − Pref = U inc − U ref
2
Complete normalized resistance is defined as
z = r + ix =
(
)
2
2
= U n 1 −  .
1 + 
.
1 − 
Any antenna, that is included to the microwave circuit, represents an arbitrary load, which
generates reflected wave in a given circuit. Together with the incident wave reflected wave
forms repeated MINs and MAXs of the normalized voltages and currents. This mode is
characterized by the traveling wave ratio, which is inversely proportional to the SWR. The
SWR is defined as
SWR =
U max I max 1 + 
.
=
=
U min I min 1 − 
Reflection of the incident wave from the load reduces the transmission power and lowers the
line efficiency. The reflection coefficient depends from the ratio between the load resistance
ZL (the antenna’s impedance in this case) and the transmission line wave impedance Z W.
 = 0 means no reflection, when the line is perfectly matched;
ZL=ZW, 
 = −1 means maximum negative reflection, when the line is short-circuited;
ZL=0, 
 = 1 means maximum positive reflection, when the line is open-circuited.
ZL=, 
SWR can also be expressed in the terms of scattering matrix elements
SWR =
1 + S 11
1 − S 11
,
where S11 - reflection coefficient.
In the element S nm designation the first index determines the S-matrix row number and
simultaneously the matched input number, to which power is transferred; the second index is
the S-matrix column number and the number of input, from which the excitation implemented.
Matching deterioration (SWR increasing) caused the restriction of the antenna operating
band, decreasing the signal output power, reducing the antennas efficiency.
Measurements of antenna characteristics
Connect using appropriate cable layout with the antenna to PORT 2.
Press “Preset” button in the left part on the analyzer front panel. Then using function keys
“Center” and “Span” in the upper right of the front panel and data entry keys set the central
frequency to 2,1 GHz and frequency range for example to 300 MHz to find the real bandwidth
of the antenna.
Press the function key “Meas” and choose on the display “S22”. Then press the key “Scale” and
choose “Autoscale” for better graph representation. For defining a frequency, on which the
best matching achieved, press key “Mkr->” and then find the minimum on the graph.
Now it is interesting to see the Smiths Chart of measured reflection coefficient to
understand which kind of matching is needed. For this press the “Format” key and choose
relevant function.
Then you can check antenna’s impedance real and imaginary parts by pressing “Meas”, then
choosing impedance measuring and Z->S22, as well as find antenna’s SWR characteristic graph
by pressing “Meas”->”S22”->”Format”->”SWR”.
For the report:
Write down the measurement results (received graphs): reflection coefficient, Smith Chart,
SWR, impedance.
What is the real operation frequency of experimental antenna? What we can say about the
bandwidth? Is it wideband or narrowband?
What can affect bad matching of the antenna with a microwave channel?
How does the reflection coefficient and input impedance effect on the directivity
characteristic and gain of the antenna?
3
POST-LAB ASSIGNMENTS
Read below carefully
3.1 Write down the answers to the pre-lab assignments neatly and return it
along with the post-lab assignments. (Hopefully now, after performing the
measurements, you have a deeper understanding of the concepts).
3.2 Explain, what is the significance of calibration in network analyzer
measurements? (Consider your observations during the measurements)
3.3 Answer to the questions presented in the second part of this lab assignment
and add all the necessary figures. Compare the results obtained with those
declared by the manufacturer.
REFERENCES
1. Hewlett & Packard: BACK TO BASICS
2. Rohde & Schwarz: Fundamentals of Vector Network Analysis
3. Mini-Circuits: RF / IF DESIGNER´S HANDBOOK