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