How does RFxpert work to make antenna measurements under a second?

13 days ago
How does RFxpert work? How can RFxpert make antenna performance measurements in less than a second? In this video, we talk about the hardware inside ...

English subtitle

Welcome to EMSCANLab.
Today what we are doing is looking inside
the RFxpert to see how it is that this equipment
can make antenna measurements in less than
one second.
So, first of all what we have set up is the
RFX.
This system is connected to our computer and
ready to do a measurement.
As a device, I have this small 2.4 GHz transmitter.
I place this on the RFX, turn it on and come
over to the software and do a measurement.
Almost instantly we can see measurement results
on the screen.
So, here we are looking at the near-field
results, Hx, Hy, amplitude and phase.
And we have also converted this near-field
data into the far-field representation showing
pattern, power level, gain and efficiency
as well as other parameters.
So, if we go back to the near-field measurements
for a moment, we can actually look inside
the hardware to see how do we get this so
quickly.
So, this system here is identical to the RFX
that we were doing measurements with.
It’s already been taken apart, all the screws
are at the side.
What we will do is just to take this apart
slowly.
First we have the lid.
And you can see this is really just a foam
spacer.
What this does is keep the antenna at a specific
distance away from the antenna or the measurement
aperture.
Now, you can increase that separation and
take care of that in the software by inputting
a separation parameter.
But this makes sure that you attain at least
25 mm minimum separation.
Directly below the lid, we have the actual
measurement system.
This is an array of small near-field probes.
And you can actually see the surface of these
probes, on the top of the PCB.
These are printed directly into the PCB itself
to give a very repeatable structure.
Each one of these probes is about 2 millimeter
in size and is a loop structure oriented directly
into the scanner so that we can pick up the
X and Y polarizations of the H-field.
If we look at the other side of the scanner,
these probes then feed into a large switch
matrix.
So, this is just an electronic switch array
that allows us to address anyone of those
probes and feed it to our RF outputs.
You can see that we have multiple RF outputs
so that we can do various testing as well
as do the measurement versus reference channel,
phase comparison.
So, this board simply couples those magnetic
near-fields over a large area, switches between
all those probes to allow us to sample in
each location and feeds that energy down into
the measurement tool below.
So, if we go further into the system, we can
look below this chamber and see that there
is an RF receiver and a power and control
board.
So, this RF receiver is fairly straight forward
and it measures from 300 MHz up to 6 GHz.
The main difference being that it will measure
both amplitude and a phase difference very
quickly.
So, this system was designed specifically
for the RFxpert and it allows us to do that
sampling of those fields very quickly as you
have seen.
This information is then captured over the
entire array.
Transferred back over USB to the software
where we then do the processing.
So, at this point where we take these near-field
measurement results, apply all the calibration
factors that we have done for the path loss
to each probe in this measurement array.
Each one of these probes is measured during
the manufacturing individually where we characterize
the path loss, amplitude loss and phase across
all the frequencies individually for each
probe.
That data is then uploaded in to the software,
we apply those corrections, and get a very
uniform, normalized near-field result.
It’s at that point where standard transformation
is going from near-field to far-field take
over and because we are using Fourier transform
based technique, those also happen very fast.
So, that just gives you a very small glimpse
of what happens inside the RFxpert.
Hopefully, giving you a little bit more confidence
that this isn’t black magic.
That there’s actually some real techniques
and equipment built in here that generate
these near-field results under one second.
So, join us again at EMSCANLab for other videos.
If you have any questions or comments, you
can post those below.