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Myreka Technologies
myreka
EKT 441: MICROWAVE ENGINEERING
ME1000 RF Circuit Design Courseware
Power Amplifier Measurement
with Vector Network Analyzer
in collaboration with
a Premier Technical Training Provider
dreamcatcher.com.my
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The usage of Lecture Material and Lab Sheets supplied with this courseware is subjected to the
following terms and conditions :

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the materials may be used only for personal and non-commercial use (for example
academic) provided that you retain all copyright and other proprietary notices contained
in the original materials on any copies of the materials
you may not modify the materials in any way or reproduce or publicly display, perform,
or distribute or otherwise use them for any public or commercial purpose
the materials are copyrighted and any unauthorized use of any materials may violate
copyright, trademark, and other laws
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Lab 6 – Power Amplifier Measurement with Vector Network Analyzer
Objectives
1) To characterize power amplifier with reflection and transmission measurement via
Vector Network Analyzer.
2) To measure gain compression using power sweep via Vector Network Analyzer
Basic Equipment Setup
PC/
Notebook
Vector Network Analyzer
P1
P2
USB Radio Software −
control panel
SMA Cable
PA
Output
USB Cable
PA Module
USB port
Antenna
Module
RF Filter
Module
PA Input
IF Filter
Module
Mixer
Module
Power
Module
SMA Cable
Transmitter unit
Accessories Required
SMA M-M Coax Cable
USB Cable
PC / Notebook with
USB Radio Software
installed
Figure 1. General Equipment configuration for PA measurement using VNA.
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IMPORTANT INFORMATION:
In measuring a high gain amplifier, it is possible of overloading the amplifier input by causing
it to saturate, demonstrate significant non-linearity, and possibly damaging the unit. It can also
damage the test equipment due to high power amplification. You should either add more
attenuation to the input or output of the amplifier or reduce the RF power of the signal source
before repeating the measurement.
For this laboratory, you recall the TRM calibration data from lab 1 by pressing <Save/Recall>
and using the knob to select the saved calibration data in the non-volatile memory and finally
pressing RECALL STATE
It is best to look at just one channel at a time. That is, when you are looking at transmission
measurements, turn Ch 1 off, and when you are doing reflection measurements turn Ch 2 off.
When viewing signals, the <Scale>, <Format> and <Marker> menus will be most helpful.
Under <Scale>, the AUTO SCALE button can be quite handy at first, but you will likely use it
less and less as you get more comfortable with manipulating the display.
Finally, if you hit <Preset> your calibration will need to be recalled. You can verify your
calibration at anytime with a TRM short PCB board for reflection and a TRM thru PCB board
for transmission. (Preset also sets the “calibration kit” selection to the default kit which
generally does not correspond to the TRM PCB boards you will use.)
Transmission Measurements
1. Recall the TRM calibration data (saved in previous lab) from the non-volatile memory.
2. Connect the PA as shown in Figure 1.
3. Do the following setting to reduce the input source power to the PA.
Power
: power range manual (PWR RANGE > Man)
: power range –45 to –20 dBm (PWR RANGES 3)
: source power, –40dBm (Enter using keypad follow by <x1>)
4. At the PC/Notebook, open the USB Radio Software. Click Connect to USB Radio
button. Under the TX Frontend Control area, click On PA to power up the PA. You
shall see the led light blinking in the PA PCB after power on.
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5. Choose the following setting to determine the small signal gain of the PA for frequency
range of 700 MHz to 1 GHz:
Start
: 700 MHz
Stop
: 1 GHz
Format
: log magnitude
Meas
: transmission (or S21)
Scale
: autoscale
OBSERVATIONS / DATA RECORDING
a) Find the maximum gain, and the frequency at which it occurs?
Gmax = _____ dB at ______MHz
b) Find the frequency below this at which the gain is reduced by 3dB from the maximum
gain.
Gmax – 3dB occurs at _____ MHz.
c) Find the gain at frequency of 868 MHz.
Gain @ 868 MHz = _________ dB
6. Change the following setting to determine the isolation of the PA:
Format
: log magnitude
Meas
: isolation (or S12)
Scale
: autoscale
OBSERVATIONS / DATA RECORDING
a) Find the isolation 868 MHz
Isolation @ 868 MHz = _________ dB
[Note – Use averaging, smoothing and smoothing aperture if necessary]
b) Elaborate the importance of isolation in amplifier.
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Reflection Measurements
1.
Choose the following setting to determine the input return loss of the PA:
Format
: log magnitude
Meas
: reflection (or S11)
Scale
: autoscale
OBSERVATIONS / DATA RECORDING
a) Find the minimum input return loss, and the frequency at which it occurs?
Min return loss = _____ dB at ______MHz
b) Find the maximum input return loss, and the frequency at which it occurs?
Max return loss = _____ dB at ______MHz
c) Find the input return loss at frequency of 868 MHz.
Return loss @ 868 MHz = _________ dB
[Note – Use the marker function to search for maximum and minimum]
2.
Choose the following setting to determine the output return loss of the PA:
Format
: log magnitude
Meas
: reflection (or S22)
Scale
: autoscale
OBSERVATIONS / DATA RECORDING
a) Find the minimum output return loss, and the frequency at which it occurs?
Min return loss = _____ dB at ______MHz
b) Find the maximum output return loss, and the frequency at which it occurs?
Max return loss = _____ dB at ______MHz
c) Find the output return loss at frequency of 868 MHz.
Return loss @ 868 MHz = _________ dB
[Note – Use the marker function to search for maximum and minimum]
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Gain compression measurement with power sweep.
1. Perform a power sweep at 868 MHz by setting the following:
Sweep Setup : CW Frequency to 868 MHZ
: Sweep Type to Power Sweep
Power
: Power Range 1 (–25dBm to 0dBm)
Start
: –25 dBm
Stop
: –10 dBm
Meas
: transmission (or S21)
OBSERVATIONS / DATA RECORDING
a) Define and elaborate the meaning of 1dB compression point.
Gain, S21 (dB)
b) Plot the gain vs power sweep graph. Use marker to locate the P1dB point.
Power(dBm)
c) What is the VNA setting at 1dB compression point?
P1dB = _______dBm
d) What is the measured gain at 1dB compression?
Gain@P1dB = _______dB
e) Is the above P1dB measure refer to input or output ?
Input P1dB or Output P1dB
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Noise
Source
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References
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Application Note 1287-1, “Understanding the Fundamental Principles of Vector
Network Analysis”, Agilent Technologies.
Application Note 1287-2, “Exploring the Architectures of Network Analyzers”, Agilent
Technologies.
Application Note 1287-3, “Applying Error Correction to Network Analyzer
Measurements”, Agilent Technologies.
Application Note 1287-4, “Network Analyze Measurements: Filter and Amplifier
Examples”, Agilent Technologies.
Product Note 8753-1, “RF Component Measurements: Amplifier Measurements Using
the Agilent 8753 Network Analyzer”, Agilent Technologies.
Thomas H. Lee, “Planar Microwave Engineering”, Cambridge University Press, 2004.
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