Hello, my name is Riadh Said. I am an engineer at Agilent Technologies. RF engineers are
designing next-generation transceivers to support wider bandwidth for technologies such
as 802.11ac and LTE-Advanced. As you go to these wider bandwidths, amplitude flatness
and phase error becomes more significant. Unfortunately, your challenge is to maintain
the EVM quality and ACPR performance of your devices going forward. Unfortunately, maybe
in your production line or in -- or in your verification test rack, you might have a switch
matrix, where you have cabling and other issues inside the test system, which introduce linear
amplitude and phase error. I am excited to show you today a new feature, what we call
"User Channel Corrections," that allows you to equalize both the amplitude and phase of
your test system. Next what I would like to do is go ahead and demonstrate that for you.
So how does this system work? We have the switch matrix, output power amp DUT and the
spectrum analyzer. What we are going to do is take the output of the switch matrix and
feed it directly to our power sensor, connected to the MXG. That will measure the amplitude
and phase response of the test system. Those will be stored into a file inside the instrument
as complex I + jQ FIR filter coefficients. When you tune the instrument to any frequency,
the firmware will automatically apply those filter coefficients to our real-time ASIC
that applies those to your IQ waveform as they are playing. And now you will have a
perfect response right out of your switch matrix. In our setup today, we have the MXG
X-Series RF vector signal generator generating 100 MHz wide QPSK signal. It is then being
routed into our switch matrix, which has poor match, going into an external amplifier and
then into our PXA, where we are now analyzing it with our 89600 VSA software. We also have
an external USB power sensor that is plugged into the back of the MXG. And we are going
to be using that to actually calibrate out the linear errors of our device. So let's
go ahead and take a look at that. Here we have our QPSK signal on the VSA. In the top
left corner, you are seeing the QPSK constellation. The match is so bad, you cannot really even
distinguish it. It is up to 30 percent EVM with this channel. If you look at the lower
right-hand corner of your screen, we actually show the channel response. And you can see
the log magnitude phase response. It has +/- 3 to 5 dB of amplitude ripple. And in the
phase response, you can see +/- 20 degrees of phase error across that channel bandwidth,
so very poor performance. Let's go ahead and see what we can do by using the external user
channel corrections. Next what we want to do is correct for the amplitude and phase
error that you just saw on the VSA. So we are going to take our power sensor that is
connected to the MXG and connect it directly to the output of our switch matrix. What I
am going to do is disconnect it from my power amplifier, take the power sensor and connect
it directly to the output of my switch matrix. After this has been done, the next thing you
want to do is go to your signal generator and go ahead and actually set up the frequency
range over which you want to run that calibration. So in this case I am running at 5.25 GHz.
So I am going to do it at that carry frequency. You hit "configure," and you execute. Now
that the calibration is complete, let's go ahead and disconnect our power sensor and
connect it back up -- connect our switch matrix back up to our power amplifier. Once
that is done, go ahead -- let's go ahead and look at our VSA software and evaluate
how well the channel correction worked for modulation quality. So now let's look at the
response of the system. I plug it back in, as you can see, it has not changed. And that
is because we have not applied our user channel corrections to the signal yet. So I will go
to the front panel of the instrument and turn that on. When you turn it on, you can see
about 1½ to 2% EVM performance. And the amplitude response is about +/- a dB. And the phase
response is within +/- 5º or less. You have just seen our new user channel corrections
equalize the amplitude and phase response of your test system. Now you can see the true
performance of your device. If you would like to find out more about the X-Series signal
generators, please visit the URL on your screen. Thank you for watching.