A New Design Paradigm for Switch-Mode Power Amplifiers Supporting Concurrent Multi-Band Wireless Communication

Iowa State University, Ames IA

Investigators

Abstract

The total number of worldwide cell phone users surpassed the 5 billion mark in 2010 and annual global sales of cellular telephones is reaching 1.8 billion units, as of 2013. With mobile technology becoming almost ubiquitous and with the types of enriched features and services that are available to the end user, mobile devices are being required to support higher data rates. Unfortunately, this need for higher data rates is resulting in systems that are now required to support communication in many different, non-contiguous frequency bands spread between 0.4 and 6 GHz. The current solution consists of using multiple, parallel, single-band power amplifiers resulting in modern cellular telephones having upwards of ten separate power amplifiers. Ultimately, this problem will result in mobile devices becoming bulkier, more expensive, and unable to support key new multi-band technologies. The root problem is that, conventionally, a single power amplifier can support only a single band. Researchers have tried to address this problem through the design of concurrent multi-band power amplifiers, but, these systems suffered significant drops in performance that were largely unexplainable using conventional design theories. This research will provide a detailed understanding of the design trade-offs in concurrent multi-band power amplifiers and a new set of design techniques. The proposed research will give radio frequency (RF) designers a new set of tools enabling them to address the challenges posed by next generation wireless system design. In addition, this project will provide methods for increasing overall power efficiency and thereby increasing battery life in multi-band systems. Moreover, this project will strengthen the U.S. transceiver industry through research, through bolstering the number of women and minorities in undergraduate and graduate STEM programs, and through supporting local industry with presentations and collaborations. Modern power amplifier design is besieged on two fronts: concurrent multi-band communication is becoming a reality and wireless devices must support a variety of different communication standards. This is leading to transmitters that must support communication over many different frequency bands spread between 0.4 and 6 GHz. The current approach of using multiple, single-band power amplifiers in parallel is becoming unsustainable and new technology is going to be required for next generation wireless devices. One promising technique is the use of concurrent multi-band power amplifiers wherein a single power cell/matching network is capable of supporting multiple, simultaneous signals. Unfortunately, there is currently no existing theoretical framework to describe the maximum efficiency, output power, stability, or linearity of concurrent multi-band power. The continued lack of such basic knowledge will fundamentally limit the potential of this new technology to address the needs of future wireless devices. This proposal will develop both a theoretical framework and a set of practical guidelines for the analysis and physical implementation of such power amplifiers. Together, these results will give RF designers a new set of tools with which they can reduce the current number of power amplifiers in modern devices, and facilitate new techniques for improving data rates and efficiency in already-designated communication bands. This, in turn, will result in a more efficient use of the available spectrum without the complicated regulatory hurdles associated with techniques such as dynamic spectrum access. The broader impact of this work lies in the ability of multi-band power amplifiers to reduce the overall cost of next generation transceivers while yielding a more flexible and robust mobile device.