Hello.
My name is Chris Benki, an Offering Manager
with the Aerospace and Defense Business Unit at NI.
Phased arrays are becoming an important RF architecture
and aerospace and defense applications such as radar
and satellite communications.
The components and modules used to build these electronically
scanned arrays require unique and stringent RF measurements
to ensure their functionality.
As such, NI is recently released the electronically scanned
array characterization reference architecture or ESA reference
architecture for short, which includes all of the IP
necessary to perform these measurements.
In this demonstration, we will show you
how to perform custom S-parameters
using the NI vector signal transceiver or VST for short.
S-parameters are a fundamental vector measurement
performed on RF components such as power amplifiers
and transmit receive modules.
This measurement includes phase information
and gain information to ensure that the module is performing
correctly.
The pulsed RF measurement library
included within the ESA reference architecture
includes the ability to perform custom S-parameters
using the BST.
These custom S-parameters separate the reflectometry
through the couplers from the instrument itself allowing
for several topologies.
These topologies can be optimized
for things such as cost, test time, and performance
of the measurement itself.
Here we see three topology supported within the pulsed RF
measurement library, ranging from cost on the left to high
performance on the right.
In this demonstration, we will use the middle topology,
which uses a single VST and dual couplers on each measurement
port.
The advantage of doing custom S-parameters using the VST
comes three-fold.
The first is that you can perform
flexible S-parameter measurements using
the same stimulus and setup as your typical large signal
analysis.
The second advantage is that by combining these parameters
with other parametric tests, it simplifies the integration
in the overall test plan.
As such, the third advantage is a reduced overall cost
of tests and a reduction in test time allowing you to get
the results you need faster.
In this particular demonstration,
we'll perform S-parameters on a typical X-band transmit
receive module used in radar applications.
This transmit receive module is typically
interfaced with a radiating antenna on one port
and a signal distribution device such as a one to four
beamformer on the other.
As such, the setup for this device
will use this beamformer to provide three functionalities.
The first is an amplified RF stimulus
to hit the transmit receive input at the right power level.
The second is digital control to ensure
that the transmit receive module's
configured in the right state.
And the third is a regulated DC bias
to ensure the power amplifier is performing
at the right efficiency.
A typical setup for measuring S-parameters
would include a vector measurement
device such as a vector network analyzer.
The downside of this setup, however,
is given the fact that the couplers are integrated
in the instrument, you're limited on where
your test interfaces can be.
In this scenario, if we used a VNA,
while one port would be correctly connected
to the radiating antenna, the other port
would be actually on the other side of the one to four
beamformer.
Therefore, the S-parameters you're measuring
are not the device under test but the overall test set up
itself.
By taking advantage of the custom S-parameters
with the VST, you can actually separate out the couplers
and put them at the right interfaces.
This allows both ports and the four S-parameters
to be focused on the transmit receive module itself
while maintaining the more complex test setup
required to perform the remainder of your test plan.
Now that we've established the setup
and shown how the hardware and software should work together,
let's switch to the software itself.
Here we see the interactive test panel included in the pulsed RF
measurement laboratory.
This provides an easy to use interactive method of setting
up calibrating and performing the parameter measurements.
As you can see in the test plan, you
set up your hardware configuration
based on the topology that you'd like to use.
In this case, as I mentioned earlier,
we use a single VST and two couplers per port.
You can also configure your switches based
on how your system is set up.
In this case, I'm using a single switch with dual muxes.
Furthermore, you can set up your stimulus,
whether it be a CW sweep or a pulsed stimulus,
as well as the test points required in your sweep,
and then subsequently, the measurement
settings such as IF bandwidth, averaging,
and where you want your calibration to be pulled from.
Speaking of calibration, as everyone knows,
calibration is essential to perform accurate S-parameters.
And as such, the interactive example
provides the ability to easily do calibration
on your custom setup in the same manner
that you might be familiar with in other scenarios.
These include setup such as qsort
or short-Open-Load-Reciprocal, SOLR.
This calibration wizard once you open
it will guide you through the process of calibrating
your custom at S-parameter setup and then provide the ability
to save those calibration values to a file for later use.
For the second time, we've already
done this, so let's skip ahead to the measurement itself.
I've specified my previous Cal File
and now I'll go ahead and click Measure.
An interactive panel will open showing you
how to set up the connections to your device,
and once you click Go, the measurement will start.
As the measurement's occurring, we
provide the automation and synchronization
of the stimulus, response, and the switching required
to measure all the parameters necessary
in the S-parameter results.
The resulting data is then displayed in various views
that you might be familiar with, such as your gain plot,
your phase plot, your return loss magnitude, or a Smith
chart, depending on how you like to look at the data.
Once you're done with the measurements,
you can save the data to a file for post processing.
You've now completed the S-parameter measurement
as required and you can move on to the next test
step in your overall plan.
So in this video, we've shown you
how to perform custom S-parameters using
the pulsed RF measurement library within the ESA
reference architecture.
Some of the common test challenges
that you might be familiar with with S-parameters include
correlation of the small signal analysis
with large signal measurements, the complexity
of the data to phases, such as the one we showed you today,
and performing fundamental RF measurements
under unique application specific stimuli.
The NI advantage with this reference architecture
is that we solve most of those common test challenges using
software defined setups, modular devices, and the ability
to combine your small signal and large signal
analysis into a single test plan.
This reduces the overall test time and cost
of your overall project allowing you to go to the market
much faster.
To learn more about custom S-parameter measurements,
please visit ni.com.