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Hi. I'm Dave Ballo, a senior RF application engineer at Agilent Technologies.
I'm standing next to the world's most advanced vector network analyzer.
With a single set of connections to the device under test or DUT, the PNA-X is capable of
performing many common RF tests that used to take an entire rack of test equipment.
Measurements include S-parameters, gain compression, intermodulation distortion and noise figure.
In this video, we'll show you how the PNA-X provides the highest-accuracy noise figure
measurement in the industry.
Why is noise-figure accuracy so important?
For R&D engineers comparing simulated and measured device behavior, higher accuracy
helps speed time-to-design by enabling faster refinement of component models.
Higher accuracy also yields improved system performance by enabling better optimization
between receiver sensitivity and transmitter power.
In manufacturing, higher accuracy provides better correlation among test stations.
This results in less rework and lower cost of test.
And higher accuracy reduces measurement-uncertainty guard bands, resulting in more
competitive products with better specifications.
Why do engineers care about noise figure?
Noise figure is a handy figure of merit that describes how much electrical noise is added
by an amplifier or frequency converter in a 50-ohm system.
The definition for noise figure is simple and intuitive:
it is the ratio of the input signal-to-noise ratio to the output signal-to-noise ratio.
For any passive device with loss or any active device with gain or loss, the output signal-to-noise ratio
will always be less than that at the input.
This means the noise figure will always be larger than one in linear terms,
or greater than 0 dB.
How is noise figure measured?
The most common measurement approach is called the Y-factor method.
This method is used with Agilent's spectrum analyzers and noise figure analyzers.
The Y-factor method uses a calibrated noise source which is assumed to present a perfect
50-ohm match to the DUT.
Y-factor measurements provide good results for most connectorized devices, especially
when using low-ENR noise sources.
However, for lots of other common RF use cases, measurement accuracy can suffer.
The PNA-X uses a different method to measure noise figure.
This method maintains the ability to make a broad range of measurements
with a single set of connections to the DUT, while providing the industry's highest NF measurement accuracy.
This accuracy applies for devices with coaxial or waveguide connectors, as well as devices
that are still on the wafer or in test fixtures.
Let's examine in more detail how the PNA-X measures noise figure.
The PNA-X uses the cold source method, where the noise figure of the DUT is calculated
from two separate measurements.
The first measurement is the available gain of the DUT, and this is done with great precision
using vector-error-corrected S-parameter measurements.
The second measurement is the noise power coming from the output of the DUT,
with a room-temperature load on the input.
The PNA-X noise figure option includes a built-in low noise receiver with three different gain settings.
This means that a broad range of devices with any combination of gain and noise figure can
be tested without any additional hardware.
Part of the PNA-X's high accuracy comes from using vector-error-corrected S-parameters
to measure the available gain of the DUT.
This standard technique corrects for the mismatch between the imperfect source impedance of
the test system and the input impedance of the DUT.
Mismatch correction is also applied when measuring the DUT's output noise power.
Another major source of error comes from noise coming out of the DUT's input and interacting
with the non-50-ohm source match.
This is especially troublesome in on-wafer, in-fixture, or automated test environments,
where the system source match is degraded by the additional hardware required to connect
the analyzer to the DUT.
The PNA-X corrects for this error by using a standard ECal module as an impedance tuner.
By varying the source impedance presented to the input of the DUT and measuring the
resulting noise figures, accurate 50-ohm noise figure is calculated.
This technique yields much higher accuracy than assuming a perfect 50-ohm source match,
and is only available on Agilent network analyzers.
For devices that are not particularly sensitive to source match, a faster, simpler method
is available that eliminates the ECal tuner.
Setting up noise figure measurements on the PNA-X is easy using a tabbed dialog box where
all of the necessary setup information is entered. When measuring converters,
three additional tabs are used to define the mixing plan and local oscillator setup.
Unlike other solutions, all of the setup information is contained in one dialog box.
Calibration is simple with a calibration wizard that guides the user through all of the required
calibration steps.
A mechanical calibration kit or an electronic ECal module is required to calibrate the S-parameter receivers,
and a noise source or power meter is required to calibrate the noise receiver.
An easy test setup and calibration procedure increases productivity, as engineers and technicians
can spend more time doing other important tasks.
In summary, the PNA-X is an ideal platform for making a broad range of RF measurements on
amplifiers and converters with a single set of connections.
For noise figure measurements, Agilent's advanced error-correction methods provide
the industry's highest measurement accuracy.
This accuracy is maintained for a wide range of devices in any test environment, whether
coaxial, waveguide, on-wafer, or in-fixture.
For more information about the PNA-X's noise figure measurement capability, download application note
1408-20 from the URL shown (www.agilent.com/find/pnax).
From there you can also view other PNA-X information, including the data sheet, brochure and configuration guide
Thanks for watching this video from Agilent Technologies, the world's premier measurement company.