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Power amplifiers on the hot seat

Posted: 23 Jan 2009 ?? ?Print Version ?Bookmark and Share

Keywords:power amplifier? EDA? CMOS SiGe GaAs?

Power amplifier (PA) is a hot topic, so I had a virtual "sit down" with some leaders in the industry to see where the technology is, and where they think it is going. The following includes some of the thoughts and remarks of How-Siang Yap, Agilent EE of EDA Product Marketing and Craig Christmas, director, Technology & Systems Architecture, SiGe Semiconductor.

What is the status of the technology?
Yap: Power amplifiers modules (PAM) are the main component performing PA functions in consumer wireless products. These consist of active components implemented in GaAs, SiGe, GaN or Si technologies integrated with off-chip passive components typically fabricated on laminate or LTCC and packaged in low cost QFN packages. The technology is still evolving in terms of the combination of active components used, embedded passive designs and packaging for optimizing price-performance.

Christmas: PA technology has matured rapidly over the years and has become highly integrated onto several process technologies such as SiGe BiCMOS, CMOS, and GaAs. The push for higher power and more efficient operation while at the same time driving cost and product size down results in new challenges facing the PA designer. New modulation formats such as multi-carrier OFDMA is creating the need for more accurate transistor models, simulation and EM tools for achieving successful designs with the fewest amount of design spins. PA technology is also a very diverse field. PAs for mobile and portable products have much different technology applications and requirements than high power PAs for base stations. Linearization techniques such as digital predistortion are also becoming very important for PA designs, and they have exciting potential for future development and performance improvement that will impact PA technology in the future.

How do you see market opportunities?
Yap: The market opportunity for PAs grows in spurts with each new generation of consumer wireless technologies coming on line e.g. WiMax, LTE, VWAN, WiMedia, etc. Higher efficiency PAs can lead to market churn of consumer replacement of wireless products with newer, smaller units packed with more functionality.

Christmas: The WLAN market is growing rapidly and new applications are emerging. In the past, WLAN was mainly deployed in computing applications. Now, the opportunity has enlarged to include WLAN enabled cellular handsets, VOIP phones, WLAN enabled digital cameras, and GPS units. All of these need PAs and front end modules (FEMs). The PA/FEM market size has increased.

Mobile WiMAX is starting to get deployed worldwideWibro in Korea, Xohm in the U.S. as well as UQ in Japan in 2009. WiMAX market has emerged and will grow rapidly over the next few years as WiMAX is deployed worldwide.

LTE deployment to start 2010+. This will drive requirement for next generation PA/FEMs.

What do you wish every RF engineer knew about this topic?
Christmas: Power amplifiers are continuing to evolve by becoming highly integrated into FEMs that provide filtering, switching and LNA functionality. As a result of higher integration, PA designs in new technologies such as SiGe BiCMOS are being pursued to provide a lower cost solution that can integrate all the FEM requirements along with the PA. PA design techniques also evolve with these new technologies and more emphasis is being placed into more accurate modeling and design simulation.

Yap: Every RF engineer should know that the design of PA module for the latest wireless application requires 3DEM-circuit-system co-simulation in order to design PAMs comprising active device on chip, off chip embedded passives such as inductors, and the packaging around it. Integrated 3DEM in the PAM design flow is critical to the success of PAM design because of off-chip passive components embedded in multi-layer laminate or LTCC that must be modeled with full 3DEM simulation.

Every RF engineer should know that the design of PA module requires accurate characterization of the non-linear power amplifier or device on chip. Now it is possible to capture the non-linear characteristics in terms of X-parameters through measurement with Agilent Technologies' Non Linear Vector Network Analyzer (NVNA). The measured X-parameter model can be directly used in the Advanced Design System (ADS) for load-pull PA design and verification against the target wireless standards. The final PA can also be characterized completely with X-parameters to be given to your potential customers to achieve early design wins in their system design.

- Janine Love
RF DesignLine

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