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Title: Some aspects of efficiency and linearity improvement techniques for microwave GaAs HBT power amplifier
Author: Ali, Fazal
ISNI:       0000 0001 3412 0914
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 2001
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This thesis examines some aspects of improving the power-added efficiency (PAE) and the third order inter-modulation distortion (IMD) performance of microwave GaAs HBT power amplifiers. The research encompasses analysis, computer-aided design and simulation and also includes investigation of the measured performance of some HBT power amplifiers. This then allows conclusions to be drawn as to the merits of the proposed techniques applied to GaAs HBT microwave power amplifier compared to the known published methods. High efficiency, Class C operation of microwave HBT power amplifier is described for the first time. A record PAE of 84% has been demonstrated for a 0.75-Watt HBT power amplifier operating at 6 GHz. Simulated and measured performance are presented and compared with the conventional high efficiency Class AB mode operation of HBT power amplifier. The third order IMD performance of a microwave HBT power amplifier is improved significantly by using the second harmonic injection technique. This is the first demonstration of this technique applied to a HBT microwave power amplifier. Mathematical analysis, CAD simulations and practical measurements have been carried out to show the feasibility of this technique. A record 46 dB reduction in the third order IMD product has been achieved from a two-stage, 28 dBm HBT Power amplifier operating over the 824-849 MHz frequency band. The technique has also been successfully applied with FM, AM, and digitally modulated RF input signals.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Power added; Inter-modulation distortion