Date of Award

Spring 1-1-2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Taylor W. Barton

Second Advisor

Zoya B. Popović

Third Advisor

Dejan S. Filipović

Fourth Advisor

Gregor Lasser

Fifth Advisor

Song Lin

Abstract

Power amplifier (PA) applications increasingly require wideband linear operation, such as in carrier aggregation, high-data rate communications as well as several other RF systems including radar, RFID, RF sensing, imaging etc. Additionally, the high peak to average power ratio (PAPR) signals of modern communications systems require operation over a wide dynamic range. Both bandwidth and linearity requirements are at odds with efficiency in conventional amplifier design. As a result, PA design with a simultaneous wideband operation, linearity, and energy efficiency has been a longstanding challenge.

This thesis presents several advanced Load Modulated Balanced Amplifier (LMBA) architectures with a common goal of operating an LMBA from a single RF-input. From previous LMBA demonstrations, an externally generated control signal is injected into the isolation port of a balanced amplifier, thus controlling the load impedance seen by the two main devices of the balanced amplifier. This study focuses on both eliminating the externally needed control signal and making LMBA architectures compatible with high PAPR modulated signals while maintaining wideband operation.

The thesis proposes three novel architectures of LMBA, the RF-input LMBA, Octaveband LMBA, and Doherty-like LMBA (D-LMBA). The proposed architectures are demonstrated through five different PAs. A narrowband version of the RF-input LMBA operating at 800 MHz uses a saturated control PA to track the optimum load as the power backs-off while maintaining the efficiency in the back-off region (6 dB output power back-off). The octaveband version, built on the same concept of RF-input operation, utilizes the passband phase response of a filter allowing it to operate over 1.8 GHz to 3.8 GHz. The D-LMBA demonstrated at 800 MHz and at 2.4 GHz utilizes a class C biased control PA, analogous to the auxiliary PA in a Doherty architecture, further increasing the back-off range to 8.5 dB. The D-LMBA concept is further extended to an X-band MMIC implementation, for which octaveband PAs operating over 6-12 GHz are designed on Qorvo’s GaN 0.15um process and are under test.

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