TAMPEREEN TEKNILLINEN YLIOPISTO
TAMPERE UNIVERSITY OF TECHNOLOGY
TLT-5500, TLT-5506
83950
Telecommunication Laboratory Course
Network analyzer work
E-mail: ari.asp@tut.fi
Room: TG 212
Lab:TG205
INTRODUCTION
You can find the information you need for the pre-lab part in the following book
Hewlett & Packard: "Back to Basics" (later referred as B to B)
Also Lehto/Räisänen: "Mikroaaltomittaustekniikka" is quite useful.
NOTE! The sources mentioned above can be found in the shelf of TLT-LAB (TG206).
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 s.64). Explain
the calibration principle, i.e. how calibration corrects measurement errors
(B to B s.71).
1.3
What are meant by the following terms?
Frequency response, 3dB bandwidth, quality factor, insertion loss/gain, phase
response, passing time delay, rejection, the 1-dB compression point of an
amplifier and amplification.
2. MEASUREMENTS
Measurements are carried out by HP network analyzer 8714C. Measurement range is
from 300 kHz to 3 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, manufactured
by MINI CIRCUITS or HP.
Amplifier Mini Circuit ZFL-1000
Attenuator Mini Circuit NAT-20
Terminator Mini Circuit NTERM-50
Filter K & L 71 MHz/0
Network analyzer basic use
After turning on, you can immediately set the equipment to its basic operation mode
by pressing PRESET –button. Now we have only one of the two channels in use.
(Transmission measurements, 300 kHz -3 GHz, source power 0 dBm, etc). Hence we
can use the equipment to measure transmittance (amplification/attenuation). It has
to be said, however, that the measurements are inaccurate, if we don’t perform the
measurement calibration.
You can easily find the default settings for different measurements by pressing the
BEGIN –button. You can find the settings for amplifiers, filters, broadband passive
components and mixers from the menu. By pressing AMPLIFIER ->TRANSMISSN
the range of scaling and also the bandwidth of the measurement system change.
As we have two channels in our equipment, we can measure two parameters at the
same time. We can define the measurements by pressing MEAS 1 and MEAS 2
buttons. So we measure transmission, reflection, power, etc. We can also find
different options for different types of demodulators: broad- and narrowband.
From the frequency menu FREQ, we can change the frequency band of measurement
by entering the START and STOP frequencies. We can also set the CENTER (center
frequency) and SPAN. By pressing CW button, we get into non sweeping measurement
mode, in other words SPAN = 0 Hz and we can change the measurement frequency by
keying in or by using the rotating disc of the equipment.
By pressing the SWEEP button you find the options to chenge sweep parameters.
By pressing the POWER button you find the options by which you can adjust the level
of the signal source LEVEL, turn on/off the power source RF ON/off and also set
the value for the source power when pressing the PRESET button Pwr Level at
Preset.
By pressing the SCALE button, you find some common setting possibilities, which you
should already know from the spectrum analyzer, and a couple of new ones, which may
be needed under some special circumstances.
You shouldn’t have any difficulty to figure out what MARKER button does.
By pressing the DISPLAY button, you get a menu with different options. In this
work, however, we don’t use any of them, except for NORMALIZE and More Display > Split Disp FULL split, by which you can split the display into two “sub-displays” (for
each channel).
After pressing FORMAT you can choose the format in which you would like to see
the measurement results. For example, after pressing FORMAT in REFLECTIONmeasurements you can see the reflection coefficient in logarithmic scale by choosing
Log Mag option. This is naturally equivalent to return loss, while choosing Lin Mag,
would give you SWR. By pressing Smith Chart you have RF-man’s dream on the
display. Polar display, though used less frequently, is available too.
CAL menu is a very important one, especially at the beginning of the measurements,
and also when the reference level of calibration (reference line) changes, (mainly as a
result of change in electrical length). We will shortly get back to this.
By pressing the AWG button, you will find the mean of the measurements, so the
equipment takes the average of the measurement results. This means that the
equipment takes sweeps by the value determined by the mean coefficient, and then
calculates the average. This would reduce the noise on the display. Included in AWG
menu is also System Bandwidth setting, by which you can make the dynamics of the
analyzer better, because the noise level reduces to a narrower bandwidth. Sweeping
time however increases.
Calibration
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 instance) Räisänen/Lehto: Mikroaaltomittaustekniikka page.107.
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.
E.G:
In transmission measurements, Transmission Cal gives different options for
calibration: Restore Defaults, Response, Response & Isolation and
Enhanced response. In each of these, there is a different error model, and so there
are different numbers of standards to be measured.
In reflection measurement, the equipment proposes: Restore Defaults or One Port.
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 level; in other words
don’t connect any adapter between the calibration reference level and the equipment
to be measured. If you doubt the measurement results, perform CAL CHECK.
AT THIS STAGE, YOU SHOULD ALREADY KNOW THAT THERE ARE TWO
CHANNELS IN THE INSTRUMENT, AND THE REFLECTION MEASUREMENTS
CAN ONLY BE CARRIED OUT FROM THE REFLECTION PORT. ALSO
TRANSMISSION CAN ONLY BE MEASURED FROM THE REFLECTION PORT TO
THE TRANSMISSION PORT.
S-parameters can not be measured directly. Especially we can’t measure the four sparameters simultaneously, though it is possible with more expensive equipment.
Transmission- and reflection measurements
Set MEAS 2 = off and MEAS 1 = reflection. Press CAL and One Port.
Connect a piece of cable (almost 30 cm long) to the reflection port. Perform the
calibration.
2.1
Let’s examine the effect of the cable length on the accuracy of the
calibration/measurements. Connect Mini-Circuit 50  terminator to the end of
the cable and check the return loss: => FORMAT = Log Mag.
You can also try the Smith Chart format. Is the value of the terminator 50 
in the 300kHz - 3GHz range? Take the cable off and connect the terminator
directly to the reflection port. How did the measurement result change?
2.2
Measure the reflection and transmission of Mini-Circuit 20 dB attenuator.
Press the BEGIN button and try to see if there is any difference between
Amplifier, Filter and Broadband Passive options. Choose Broadband Passive.
Measure Reflection and Transmission, what can you say about the reliability of
the results; especially about Transmission measurement?
2.3
Perform the Transmission Cal Enhanced Response and measure once more.
Compare the results.
2.4
Measure the 3dB bandwidth, amplification and 1 dB compression point 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 Murata GSM or K & L
71MHz band pass filter.
Note that you can measure the parameters above in different manners, for
example using a -marker or directly.
3. POST-LAB ASSIGNMENTS
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.
2.
3.
4.
5.
6.
A. Lehto, A. Räisänen: MIKROAALTOMITTAUSTEKNIIKKA
Pekka Eskelinen: NYKYAIKAISEN RADIOTEKNIIKAN MITTAUKSET
KÄYTÄNNÖSSÄ
A. Räisänen, A. Lehto: Radiotekniikka
Hewlett & Packard: BACK TO BASICS
Fluke: The ABC´s of OSCILLOSCOPES
Mini-Circuits: RF / IF DESIGNER´S HANDBOOK