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Title: Continuous mode high efficiency power amplifier design for X band
Author: Canning, Timothy A. J.
ISNI:       0000 0004 5358 7343
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2014
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This thesis is focused on the investigation and implementation of novel techniques for the design of X band (8 - 12GHz) power amplifiers. One of the main topics is the expansion and novel implementation of continuous mode theory, with the intention of improving the bandwidth and efficiency of X band power amplifiers. This work builds upon the Class B/J continuous mode theory to incorporate cases where <[ZF0] 6= RL, not described by the original Class B/J theory, with a tool called the “clipping contour”. The clipping contour tool shows a graphical representation on the Smith chart of the boundary between impedances generating a voltage waveform which will modulate or “clip” the current waveform, and a voltage waveform which will leave the current waveform unaltered. This non-clipping space is shown, with measured load pull and amplifier data, to represent the maximum efficiency case for a given ZF0, thus the clipping contour tool thus gives designers the ability to predict the areas of highest efficiency and power given any ZF0, without the need to use costly, time consuming multi harmonic load pull techniques. Push pull amplifiers using quarter wave coupled line baluns are proposed as an ideal matching topology to exploit this new tool. Various balun topologies are studied using a novel extended transmission line model. This model is shown to predict accurately and explain the “trace separation” effect seen in planar baluns and not their 3D coaxial cable equivalents. It also forms the basis of analysis which results in a powerful new equation capable of guaranteeing the elimination of trace separation completely, without compromising performance. This equation is used to design an optimal balun which possesses the largest fractional bandwidth (130%) of any balun ever published on single layer thin film Alumina, whilst simultaneously eliminating trace separation. The optimised Alumina baluns are used to construct push pull output demonstrator circuits which show efficiencies of 40% over greater than an octave bandwidth, a significant advancement of any other comparable published work. These techniques demonstrate the potential to exceed double octave bandwidths with efficiencies greater than 40% once optimised. Initial investigations on MMIC and 2.5D processes show the potential to replicate the Alumina performance over octave and decade bandwidths respectively.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TA Engineering (General). Civil engineering (General)