AWR Connected™
for National
Instruments
Application Note
AWR AND NI TOGETHER DELIVER A POWERFUL DESIGN
PLATFORM FOR COMPLEX WIRELESS CIRCUITS
Many veteran designers no doubt remember how comparatively simple it was
to design base station or mobile phone amplifiers when the only modulation
Linking RF Design
and Test through
AWR Software and
National Instruments
LabVIEW/T&M
technique was analog and amplifier performance could be verified using
Additive White Gaussian Noise (AWGN). Nowadays, second (and subsequent)
generations of wireless networks usher in digital modulation techniques that
necessitate the need to stimulate amplifiers and other circuits with waveforms
they actually process in service. It therefore necessitates far tighter integration
between the baseband signal processing and high-frequency circuit design
tools as well as actual test equipment for both generating these modulated
waveforms and evaluating their effects on the performance of the design.
This application note describes the benefits of using AWR’s high-frequency design
software products (Microwave Office™ and Visual System Simulator™ (VSS))
seamlessly alongside National Instruments’ graphical programming software
environment, LabVIEW, and a broad range of modular instruments to better meet
the challenges posed by today’s complex wireless access methods.
The higher-order modulation and other advanced signaling techniques employed in
today’s third-and fourth-generation wireless systems demand unprecedented levels
of linearity, efficiency, and signal integrity over broader bandwidths. The designer’s
challenge may start at baseband but also extends throughout the transmit and
receive paths through RF and microwave frequencies. Traditionally, the use of
software tools for these tasks were disparate. However, today’s advancements in
wireless applications and modulation techniques are driving the need for tighter
design, verification, test, and debugging across the entire signal chain.
DESIGN TOOL INTEGRATION:
FROM BASEBAND TO MICROWAVE
Today, baseband signal processing, high-frequency design,
and system verification software can be employed together
along with hardware-based or virtual measurement systems
that generate both standard-based and random waveforms
and measure the design’s performance. The software tools
described in this application note are employed either singly
or together at various points in the design process, which
offers significant benefits to designers, not the least of which
is their ability to catch problems at even the earliest stages of
the design flow where they are considerably easier, faster, and
less expensive to fix.
Designers have long used LabVIEW as a programming language to automate
instrumentation. AWR and National Instruments have begun to blur the lines between
the software solutions. The AWR design environment provides a convenient plug-nplay interface to LabVIEW, adding LabVIEW’s graphical programming environment
for a broad range of signal processing and software-defined, virtual instrumentation
approach to RF device testing into its product portfolio.
Hardware-in-the-loop design flow.
AWR Connected
for National
Instruments
Application Note
For example, a VSS block can call LabVIEW directly via a Virtual Instrument (VI)
server interface, which makes analysis easier within the AWR Design Environment
and increases the designer’s productivity. Simulated measurements within the
LabVIEW environment can also be accessed for further domain-specific analyses.
Correlation of both simulated and actual measurements is acquired in the
LabVIEW environment. VSS software can also provide a simulated version of the
design under test, which allows LabVIEW to build test and validation cases earlier
in the design flow, and even before a prototype is fabricated.
Using an RF power amplifier as an example, LabVIEW can generate, analyze, and
measure an LTE baseband signal within the AWR Design Environment. Using a
Microwave Office design of the Infineon power amplifier
used in this application note.
single VSS system diagram, the signal is passed into a simulation model of the
amplifier that was designed and analyzed using Microwave Office software at the
circuit level. VSS manages the signal from LabVIEW and dynamically creates a
system model for the amplifier based on the circuit-level simulation performed using
Microwave Office software. The output of the simulated amplifier is then passed
back to LabVIEW to be demodulated and the baseband signal analyzed. Microwave
Office software handles the simulation, LabVIEW the signal processing, and VSS
the system-level simulation. Measurements are made with National Instruments PXI
hardware during the design and simulation stages.
Measured results from the physical instruments can be easily retrieved by
VSS via the VI integration block. An LTE waveform generated in LabVIEW is
introduced to the simulated model of the power amplifier within Microwave
Office software. As VSS software can communicate with the National
Instruments RF vector signal generator and vector signal analyzer and the
power amplifier under test, it can bring the measured data back to Microwave
Office software for comparison with the simulations and analysis to reveal
differences between the two.
SUMMARY
Shown above
is the VSS
block diagram
for an Infineon
power amplifier.
Shown to the
right is the tight
agreement
between
simulated and
measured
results for
the PA’s
constellation
and power
spectrum.
Not long ago, integration of baseband signal processing, high-frequency, and
system-level software tools with either virtual or hardware-based instruments
was extremely difficult if it could be accomplished at all. Today, the performance requirements
imposed by wireless standards make it a necessity and software tools such as LabVIEW,
Microwave Office, VSS and AXIEM®, combined with the flexibility of virtual instruments make this
not only possible but straightforward and accurate as well.
When used together, they provide a formidable weapon with which to combat challenges such
as maintaining signal linearity over broad bandwidths as well as meeting the requirements of
wireless standards such as LTE and WiMAX. These challenges will invariably continue to increase in
complexity with the emergence of LTE-Advanced that will follow its predecessor in five years or so,
and surely in even more spectrally-efficient communications technologies of the future. When they
do, the process described in this application note will be up to the challenge.
AWR, 1960 East Grand Avenue, Suite 430, El Segundo, CA 90245, USA
Tel: +1 (310) 726-3000 Fax: +1 (310) 726-3005
www.awrcorp.com
Copyright © 2012 AWR Corporation. All rights reserved. AWR is a National Instruments Company.
AWR, the AWR logo and AXIEM are registered trademarks and AWR Design Environment, Microwave Office
and Visual System Simulator are trademarks of AWR Corporation.
All others are trademarks of their respective holders.
AN-HIL-2012.5.31