10 GHz Modulation Bandwidths for Exploring 5G mmW Backhaul and Unlicensed Spectrum


Hi–my name is Randy. I’m an application engineer at Keysight. Remember when wideband cdma was considered
wide, which had a channel bandwidth of 5 MHz. Today’s modern communication systems are using
bandwidth in excess of a gigahertz. Take, for example, 802.11ad, which has a channel
bandwidth of 2 GHz. In the future, 802.11ay will have even wider
bandwidth through the use of channel bonding. Even 5G is using wider modulation bandwidths. Everybody wants to have higher data rates
to the end user, and one of the ways this is being done is through the use of wider
modulation bandwidth at the microwave and millimeter wave frequencies. Today I’m going to show you a demo using our
AWG and UXA to generate and analyze ultra-wide bandwidth signals. Let’s take a look at the demo setup. We’ll start with the M8195A arbitrary waveform
generator. This has a sample rate up to 65 gigasamples
per second. This enables us to generate signals that have
a bandwidth in excess of 10 GHz. In this demo we’re going to generate an IF
directly centered at 5 GHz, with a bandwidth of nearly 10 GHz. This will be the input to our up-converter. We’re also using a MXG signal generator as
the LO. This gets mixed with the IF to produce an
output at a frequency of 83.5 GHz. The output of our up-converter goes through
an amplifier to increase the signal level and then the output of the amplifier–we go
from a waveguide to coax transition and then we go to our UXA signal analyzer, the N9041B,
which has a frequency range from DC all the way 110 GHz. The UXA has an internal digitizer that can
digitize signals up to a GHz in bandwidth. Because we have a signal that is nearly 10
GHz wide, we’re going to take the IF output of 5 GHz and use that to drive one of our
wide bandwidth oscilloscopes. Where we have the VSA software running which
will do the demodulation for our demonstration. So let me show you how we generated the signal
for this demo. We’re using our IQ Tools application, which
comes with the M8195 AWG to generate our wide bandwidth signal. First we’re going to set the symbol rate to
7.1 GHz. We’ll set the modulation type to 16 QAM. We’ll set the filter to a Root Raised cosine
filter with an alpha of .35, and then we’ll set the carrier offset to 5 GHz. So this will give us a 16 QAM signal with
a bandwidth of nearly 10 GHz centered at an IF of 5 GHz. Once you’re satisfied with the settings, we
press the download button, and it gets downloaded into the AWG and begins generating the signal. Now that we’ve generated the signal, let’s
take a look at the spectrum on the signal analyzer. We’re making a swept tuned measurement of
our spectrum coming out of the upconverter. On the screen you can see the upper and lower
mixing products of the LO and the IF. The signal that we’re actually demodulating
is centered at 83.5 GHz. The UXA has several band breaks over its frequency
range and because of this, the specified bandwidth of the analyzer is 5 GHz. However, in many other frequencies of bandwidth
it’s much wider. In fact, you can see today we’re generating
and analyzing a signal that’s 10 GHz wide at 83.5 GHz, which is in the lightly licensed
e-band region. Now we’re going to demodulate the signal and
look at the demodulation metrics. To do that, we’re going to use our VSA software. In the upper left screen, you see the constellation
diagram, which shows the 16 QAM signal. In the lower left screen, you see the spectrum
which shows nearly a 10 GHz bandwidth. And then, if we look in the lower middle screen,
we can see the EVM, which shows an incredible result considering the very wide modulation
bandwidth that we’re using. Then in the upper right part of the screen,
we see the overall channel response from the equalizer and in the lower right we see the
CCDF curve. The flexibility of the VSA software enables
a large number of other traces and metrics to be displayed, depending upon your specific
requirements and device under test. If you’re an R&D engineer working on ultra-wide
bandwidth communication systems, consider Keysight’s off-the-shelf solutions with
capability up to 110 GHz. For more information, visit us on the web. Thanks for watching.

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