Date of Award
Doctor of Philosophy (PhD)
Electrical, Computer & Energy Engineering
Modern communication and radar signals increasingly utilize signals with high peak-to-average power ratios to achieve spectral efficiency. Three power amplifier architectures have been developed to efficiently amplify such signals one of which is outphasing. At high frequencies, such as X-band, outphasing requires enhancement in the form of discrete supply modulation or rectification to achieve performance competitive with alternatives such as Doherty and envelope tracking. This thesis focuses on the development, theoretically and experimentally, of the outphasing power amplifier, including enhanced modes of operation.
A novel quasi-MMIC outphasing PA and measurement setup are developed to enable the direct measurement of power waves internal to the PA architecture, yielding internal PA performance and load modulation. Due to the flexibility of the PA prototype and measurement setup, both isolated and non-isolated combiners are utilized with and without discrete supply modulation. Insight into the dynamic operation of five outphasing variations is gained.
Two enhanced outphasing PAs are fully integrated on GaN MMICs. A power recycling LINC PA makes use of the duality between a high efficiency PA and rectifier to recover power wasted in the isolated combiner. A multi-level Chireix outphasing PA utilizes discrete supply modulation to minimize DC power consumption, thereby improving efficiency at back-off. Realistic testing with a GaN discrete supply modulator MMIC shows particular promise for the novel multi-level Chireix outphasing architecture.
Finally, the importance of the gain of power amplifiers internal to the outphasing architecture is substantiated in simulation and measurement. Highly efficient multi-stage power amplifiers are optimized through the development of harmonically terminated interstage matching networks.
Litchfield, Michael Philip, "Efficiency Enhancement Techniques for the Outphasing Power Amplifier" (2016). Electrical, Computer & Energy Engineering Graduate Theses & Dissertations. 132.