Research into Radio Frequency Integrated Circuits (RFICs) has been growing rapidly in recent years, as wireless communication devices become more widespread (WLAN, Bluetooth, cell phones, UWB), and new generations of standards present ever changing technological hurdles to overcome to meet the demands of ever increasing data rates (1 GB/s for IEEE 802.11n). This is an exciting field to be working in, as numerous emerging applications lead to plentiful opportunities for innovation, and the rapidly growing consumer demand for wireless devices translates to strong growth in the job market in this field. All of my specific research interests fall under the umbrella of RFICs, and I am always interested in getting involved in new areas within this field.
Integrated Circuits for Phased Arrays
Phased Arrays have been used for many years in military applications such as radar and satellite communications, but in recent years they have been explored for a variety of other applications, such as a means of increasing data rates in wireless networks, automotive radar, and position sensing for instrumentation. The advent of System-on-Chip RFICs has enabled great reductions in the size and cost of phased arrays which has opened the doors to new applications. My dissertation research investigated circuits and techniques for fully integrated CMOS phased array implementations, an overview of that work which was published in the the University of Washington Electrical Engineering Kaleidoscope can be found here. My current research in this area is focused on compact, low-power phase shifter implementations.
Phase-Locked Loops
Phase-locked loops (PLLs) are an integral part of almost every wireless transceiver, as they are used to generated a stable frequency source which can be used for the up or down conversion of signals between the base band and the carrier frequency. They are also used in a number of other areas, such as clock synchronization in large digital systems, clock and data recovery in wireline communication systems, and control systems. My initial research efforts during my Ph.D. studies were in the area of PLLs, and I have gained additional experience in this area through a graduate course that I taught at the University of Washington. My current interests center around fast settling (sub 9.5 ns) PLLs for Ultra-Wideband (UWB) Orthogonal Frequency Division Multiplexing (OFDM) schemes.
Ultra-Wideband Radios for Sensor Networks
The Federal Communications Commission (FCC) defines an Ultra-Wideband (UWB) signal as one with bandwidth that exceeds the lesser of 500 MHz or 20% of the carrier frequency. A 2002 report by the FCC allocated bandwidth from 3.1 to 10.6 GHz for UWB applications with very low power levels. The combination of very low power levels and very wide bandwidths can lead to either high data rate, short range wireless systems (such as the OFDM schemes mentioned above which are being used for Personal Area Networks) or low data rate, longer range wireless systems (which typically use an UWB variant known as impulse radio) which could find application in wireless sensor networks. I am interested in exploring radio architectures and circuit techniques for very low power transceivers geared toward environmental monitoring and data gathering applications.