Events
IEEE APS/CASS/EDS/MTTS/SSCS SSCS Distinguished Lecturer Seminar
Title: Over A Century of Electronic Power Amplifiers from D(oherty)PAs to D(igital)PAs
Speaker: Professor Jeff Walling
Virginia Tech
Date: Thursday, November 7, 2024 at 4:00-5:30pm PDT
Location: Qualcomm Q Auditorium (6455 Lusk Blvd, San Diego, CA 92121)
In Person only
*Non-Qualcomm Employees*: Please arrive 10-15 minutes earlier to find parking. Proceed to the front lobby of Building Q and sign in at the front desk.
Abstract:
The first vacuum tube amplifiers appeared circa 1912 and were used originally as audio amplifiers. Shortly thereafter they helped to popularize AM radio broadcasting. Generating sufficient broadcast power was difficult and electricity costs were high for operators, driving many key innovations to improve output power and efficiency, particularly when amplifying signals with large peak-to-average power ratios. The Doherty Power Amplifier (D(oherty)PA), invented in 1936 by William Doherty was a transformative invention that enabled high power and efficiency simultaneously, using two amplifiers in a configuration that enabled load modulation to improve efficiency at output power backoff. It is surprising that after almost 90 years, and a transformation from vacuum tubes to solid-state electronics, that the D(oherty)PA remains one of the most popular PA architectures, especially for mmWave PAs. In this talk, I will review the D(oherty)PA and several key innovations in PAs over the past century, including outphasing (Chireix 1935), envelope elimination and restoration (Kahn 1952) and class-G/multi-supply (Feldman 1976), while providing several examples of recent transformations to allow these PA innovations to operate in modern transistor processes. The drive for innovations in PAs continues today and I will then introduce the Digital PA, a revolutionary transformation to the PA that embeds a DAC and mixer into a switching PA. The D(igital)PA provides a pathway for high levels of integration that are necessary for multi- band and MIMO transmitters. It also provides a means to realize the voltage-mode D(oherty)PA, linking the D(oherty)PA to the D(igital)PA.
Speaker biography:
Jeff Walling received his BS from University of South Florida and his MS and PhD from University of Washington, all in Electrical Engineering. He has held industrial positions at Motorola, Intel, Qualcomm and Skyworks. His research has primarily focused on circuits for wireless communications and sensing. From 2012 to 2019, he was an assistant, then associate professor at the University of Utah. Then he was head of RF transceivers at Tyndall National Institute in Cork, Ireland. Since 2021, he has been an associate professor at Virginia Tech. He has served as an associate editor for TCAS-II, TCAS-I and JSSC, and on the technical program committees of the IEEE RFIC, ISSCC and NEWCAS conferences. He is a senior member of the IEEE and has more than 80 papers in peer-reviewed conferences and journals.
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