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Keysight Technologies
Simple Scalar Network Analysis of Frequency
Converter Devices using the U2000 USB Power
Sensor Series with the ENA Network Analyzer
Application Note
Introduction
This application note will show how to make easy scalar network Introduction . . . . . . . . . . . . . . . . 2
analysis or power measurements using the Keysight Technologies, Inc.
U2000 series USB power sensor with the Keysight ENA. Controlling Part 1 . . . . . . . . . . . . . . . . . . . . . . . . . 2
this ultra-light and easy-connection USB power sensor with the Operation of frequency offset mode
ENA's built-in VBA macro as a broadband power detector, you can and its limitation . . . . . . . . . . . . . .3
easily make scalar network analysis of frequency converter devices. Using the USB power sensor with
the ENA . . . . . . . . . . . . . . . . . . . . .4
Part 1 explains the case that the USB power sensor is useful com-
pared to the normal frequency offset mode (FOM) of the ENA. Part 2 Part 2.. . . . . . . . . . . . . . . . . . . . . . . . . 6
will show a measurement example using a sample VBA Wizard. Operation example using sample
VBA Wizard . . . . . . . . . . . . . . . . . .6
Typical cycle time . . . . . . . . . . . . . . . .12
System requirements . . . . . . . . . . . . .12
Part 1 Related literature. . . . . . . . . . . . . . . . .13
There are some components that are suitable to be measured with
scalar network analysis. For example, frequency converter com-
ponents with an embedded local oscillator (LO), such as a CATV
tuner, low noise block (LNB, down converter of satellite TV parabola
antenna) of satellite communications, or similar components. Embed-
ded LO signals of these devices are sometimes not accessible from
outside and are difficult to lock the phase between RF and IF signals
when measuring.
Note: The USB power sensor control for power calibration of the ENA is not
yet supported with Firmware version 9.1 or earlier firmware versions
Note: Vector network analysis is not available using power sensors.
Operation of Frequency Offset Mode and Its Limitation
Keysight network analyzers (PNA series and ENA) have a frequency offset
mode (FOM) option1 that allows users to set source or receiver port frequency
independently. When using FOM, frequency converter devices can be measured
precisely and accurately2. The operation requires defining the offset of a source
port frequency and a receiver port frequency precisely, and then the receiver port
can detect the down-converted or up-converted signals. However, to apply the
FOM method properly, the LO signal of a DUT has to be known and locked to the
source or the receiver port frequency of a network analyzer. Otherwise the differ-
ence between predicted IF signal and actual IF signal directly causes a magnitude
error due to the IFBW filter shape implemented in these network analyzers3. In
general, when the IFBW is set to 1 kHz, the 3 dB bandwidth of the IFBW filter is
approximately 1 kHz. That means if an actual output frequency of DUT has 500 Hz
offset (=BW/2) from a target frequency, a measured magnitude result has
3 dB error. Also, when the output signal is drifted, measurement results are
also changed at the same time.
Figure 1. IFBW vs. LO frequency drift with FOM
1. For the Keysight E5071C, Option 008 frequency offset mode is necessary to enable the FOM option.
2. The PNA and ENA provide advanced calibration methods to measure absolute group delay using Keysight
patented Vector Mixer Calibration (VMC) technique, or matching error corrected measurement using Scalar
Mixer Calibration (SMC) technique.
3. The PNA series offers an advanced method Embedded LO Measurement (Option 084) for accurate relative
phase and absolute group delay measurement.
3
Using the USB Power Sensor with the ENA
One reasonable solution for this application is to use a power sensor as a
broadband power detector. A power sensor detects all power in its bandwidth.
Thus, unless the frequency range of the output signal is within the bandwidth of
a power sensor, its measurement result is stable and not influenced by output
signal offset or drift as shown Figure 3. The U2000 series USB power sensor is
a good solution with its small size, easy connection, controllability, and its
affordable price.
Figure 2. Power sensor (broadband detect) vs. LO frequency drift
4
The next two figures show the result of measuring a mixer with a locked (Figure
3) and drifted (Figure 4) LO signal by FOM (trace 1 in blue) function of the ENA
and by the USB power sensor (trace 2 in red). The measurement result of the
USB power sensor has good correlation with FOM at locked signal, and is stable
with drifted LO signal.
Figure 3. Measurement results with Locked LO (RF Power vs. IF Power)
Figure 4. Measurement results with drifted LO (RF Power vs. IF Power)
5
Part 2
Operation Example with Sample VBA Wizard
Here is an example procedure using a sample VBA program (USB power sensor
measurement wizard) using the E5071C ENA network analyzer. The VBA makes
scalar power measurements with a U2000 series USB power sensor using port 1
of the ENA as a signal source. S11 reflection measurement is also performed to
measure return loss of the DUT.
Connect the U2000 series USB power sensor to the E5071C using a USB cable.
Confirm the power sensor is recognized correctly using"Keysight Connection
Expert", which can run from Windows Desktop menu [Start] > [All Programs] >
[Keysight IO Libraries Suite] > Keysight Connection Expert.
The USB connected instruments has to be listed with the correct serial number
and a VISA alias. If the VISA alias is missing, add it by right-clicking the U200xA
model icon, then select "Add VISA Alias" to be recognized by the sample VBA.
Figure 5. Keysight Connection Expert
After confirming the USB power sensor connection, run the program on the
ENA menu from [Macro setup] > {Load Project} > and select "E5071C_USB-
PSmeasWizard_xxxx.vba", then press [Macro Run] button or select {Select
Macro} > {Module1 main} by softkey.
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Start. Program running with USB recognition
The first page of the wizard is shown in Figure 6. This sample wizard consists of
eight steps to complete the measurement process. Press [Next] button to select
the USB power sensor.
Figure 6. Top page
Step 1. USB Power Sensor Selection
Select the USB power sensor that is connected to the ENA. The serial numbers
of the USB power sensor connected to the ENA are displayed in this menu. If you
don't see the proper serial number, check the USB power sensor connection by
returning to Setup.
Figure 7. USB power sensor selection page
7
Step 2. Measurement parameters setup
Select pre-defined parameters and trace locations for three cases.
Figure 8. Measurement parameters setup
Step 3. Parameters setup
Set the ENA's stimulus and sweep parameter setting. Also, you can check the
USB power sensor's measurement range in the lower right hand side.
Figure 9. ENA parameter setup
8
Step 4. ENA calibration (optional)
Take the full 1-port SOLT calibration to the port 1 of ENA that is valid for S11
measurement.
Figure 10. ENA port 1 calibration
Select the ENA's system impedance between 50 ohm and 75 ohm based-on the
impedance of the DUT. When selecting 75 ohm, connect 11852B 50 ohm / 75 ohm
minimum loss pads to the test cable and power sensor. Loss value of the 11852B
can be set in this form.
Figure 11. Connecting minimum loss pad when 75 ohm system is selected
9
Step 5. USB power sensor parameters setup
Set the power sensor's target power and target frequency. If the RF signal of the
ENA is from 500 MHz to 600 MHz and the DUT's LO signal is 400 MHz, then set
the target frequency as RF + LO (900 MHz to 1000 MHz) or RF