Hello, this is Part 2 of a 3 part series addressing beamforming test challenges.
My name is Sheri DeTomasi with Keysight Technologies.
This video describes the key measurements to
visualize and validate your
beamforming applications.
Be sure to watch part 1 on application and measurement challenges
and part 3 on showing how the Keysight multi-channel LTE/LTE-Advanced
Reference Solution combines the multiple
phase-coherent PXIe Vector Signal Generators
and PXIe Vector Signal Analyzers
with the Keysight industry-leading application software
and multi-channel configuration and
correction tools to allow you to accelerate your test setup
and gain deeper insight faster our application expert Craig Grimley
will now walk to some key beamforming measurements with the 89600 VSA
software
plus multi-channel signal analyzer
we can start by doing the time synchronized RF signal capture
from all eight antenna elements enabling the 89600 VSA
spectrogram
feature we can immediately gain insight into the frequency resource activity
this allows us to quickly build up a picture of Pair subframe
RF activity levels for user specific resource block scheduling
as well as common control channels and signals note this feature
does not require any demodulation at this point and is a very useful debugging tool
when investigating unexpected RF or scheduling issues
especially when those issues impair normal demodulation of the signal
prior to demodulating the TD LTE capture signal
we need to configure the 89600 VSA software
antenna a group parameter with the appropriate number of elements and
spacing used
to match or physical RF antenna configuration as mentioned earlier
the beamforming weightings can be changed on an individual resource block
basis
therefore we may choose to view the UE specific weightings results
on a pair resource block basis or alternatively
per user allocation The TD LTE measurment application provides a rich set of
demodulation results
to help you verify and visualize your MIMO beamforming
signals available results include
IQ constellations EVM result metrics
detected resource allocations UE specific reference signal weights
cell specific reference signal weights
and impairments UE specific
and common broadcast antenna beam patterns let's take a closer look at
some of these result traces
the demodulated IQ constellations are displayed per spatial multiplexing layer
and provide a quick visual indication of the signals modulation quality
correctness
the frame summary trace provides access to individual EVM and power
metrics associated with each channel and signal type
it also provides a color key for all channel type results
which is reused throughout the VSA traces the detected allocations trace
lets you visualize the resource block allocations for each user specific
transmission
plus resource allocations used by common control channels
measured UE specific reference signal weights
are presented in table format for each of the eight antenna elements
weightings can be evaluated in both magnitude and phase
down to the individual resource block allocations associate it with each user
transmission
separate UE specific reference signal weights traces
are available for each spatial multiplexing layer to help you
visualize the beamforming performance
the VSA software also presents a resulting combined
beam pattern trace associate it with each antenna group
measure UE specific reference signal weights from the first four input channels
are used to compute the antenna group zero beam pattern trace
this process is repeated for the second four input channels
to compute the resultant antenna group one beam pattern trace
note that a separate bean pattern trace can be visualized for each
resource block associated with each user device
similar to how the IQ constellation provides a quick visual health check of
modulation quality
the antenna group beam pattern trace provides a quick visual health check of
beamforming baseband encoding
and RF calibration quality any identified anomalies can be investigated
in detail
using the UE specific weight trace metrics channel frequency magnitude and
phase response traces can be viewed simultaneously for all
eight antenna elements along with VSA supported common tracking error trace
the VSA MIMO info trace reports cell specific reference signal metrics and
impairments
measured for all eight antenna elements reported metrics include cell RS power
EVM timing phase symbol clock
and frequency error allowing you to better
verify the common broadcast beam pattern weightings associated with each
antenna element the VSA software also extracts these relative antenna
weightings in order to produce the cell
RS derived sector wide broadcast beam pattern
shown here in blue user-specific and common broadcast beam pattern trace results
can be viewed in either IQ polar format
or alternatively in log magnitude dB format
both formats support the VSA markers
for easy tracking of main lobe peak levels and azimuth impflications during live
measurement updates VSA markers can also be used to readout
various beam pattern characteristics like Null depth azimuth inflacations
and main lobe to side lobe levels a key metric to be verified within TD LTE
beamforming transmissions
is beamforming gain the VSA software has added a new beamforming gain results
trace
specifically for this purpose it reports dB difference between each UE specific
beam pattern
and the common cell-specific broadcast beam pattern
to produce a beamforming gain trace result for each user allocation
the beamforming game results can be viewed for each individual resource
block associated with each user's allocation
thanks Craig for the detailed explanation on these measurements
be sure to watch the next video in this series to find out how the
Keysight LTE/LTE-Advanced
multi-channel Reference Solution provides the essential elements of this
solution
that enables you to get to results quickly and with more confidence.
Thanks for watching! For more information, be sure to visit us at:
http://www.keysight.com/find/solution-lte