Hi, my name is Eric Diez. I am an engineer
at Agilent Technologies. Many customers have asked us how to generate and analyze digitally
modulated signals at millimeter-wave frequencies. And this is becoming increasingly important,
as new applications appear at these high frequencies – things like automotive radar or wireless
HD video transmission. So today, we are going to demonstrate creating and analyzing a 64-QAM
signal at 65 GHz. And to do that, we will be using a PSG vector signal generator, a
PSG analog signal generator, an EXA signal analyzer running the 89600 vector signal analysis
software. Let’s take a closer look at how to set up this measurement. To generate our
signal, let’s begin with the vector PSG. We are creating our 64-QAM signal internally
and modulating a 15 GHz carrier. And that is mean output here on the RF output. Now
using the internal baseband generator, we can generate up to 80 MHz of modulation bandwidth.
But some applications require more bandwidth. So in those cases, we use the external IQ
inputs on the rear panel and an arbitrary waveform generator that can create up to 2
GHz of modulation bandwidth. So that gets us very wide modulation, up to 44 GHz. But
in this case, we want to go up to 65 GHz, and we will use an up-converting technique.
And to do that, I need a local oscillator. So for that, I will use the analog PSG. It
is putting out a 25 GHz signal with +17 dBm. Now the reason I use the high level +17 dBm
output is because that helps us get better conversion efficiency in the mixer. Now to
perform the actual up-conversion, I am using this mixer right here, mounted on the front
panel. And, normally, this would be an option in the analog PSG called “Option H65,”
that is mounted behind the rear panel. I am using it here externally, so it helps us visualize
the signal flow better. Now this particular mixer has an integrated doubler, so that doubles
our 25 GHz signal from the PSG to 50 GHz. We combine that 50 GHz signal now with the
15 GHz IF from the vector PSG, and that is what gets us to 65 GHz. So that is how we
generate our modulated signal up at the millimeter frequency. Let us take a look at how we analyze
the signal now. Now to analyze our signal, we will be using the EXA Signal Analyzer,
which is part of Agilent’s family of X-Series signal analyzers. This happens to be the 44
GHz model, and it has the external mixing option. The external mixer we are using is
right here. That is one of our smart mixers. And we call it a smart mixer because it has
onboard memory that has all the correction values for this particular mixer stored inside.
When I connect this to the EXA, I am using a USB cable. And when I plug that in, it will
automatically identify which mixer I am using, and it will download those correction factors
into the memory of the EXA. That corrects for the frequency response of the smart mixer,
giving us the very best amplitude accuracy. We also have this RF cable that takes the
LO signal from the EXA, runs it to the smart mixer. And then the IF signal comes back through
the same cable into the instrument. Inside the EXA, we are using the 89600 VSA software.
This is a really powerful software package that lets us analyze a wide variety of signals
and modulation types. And you will note here on the display, we have, in the upper left
quadrant, our familiar constellation diagram for a 64 QAM signal. Then down here, we have
all the measurement results that were calculated with the software. And, in particular, I will
point out that we have a very good EVM number. It is running about 1.6 percent, which is
pretty remarkable, considering we are looking at fairly high-order modulation up at 65 GHz.
So in this short demonstration, we have been able to show how you can generate and analyze
a digitally moderated signal up at 65 GHz with low EVM. If you would like to find out
more information about Agilent’s millimeter-wave solutions, please visit the URL shown here
or talk to your Agilent sales representative. Thanks for watching.