1 research outputs found
Novel power amplifier design using non-linear microwave characterisation and measurement techniques
This thesis, addresses some aspects of the well-known, problem, experienced by designer of
radio frequency power amplifiers (RFPA): the efficiency/linearity trade-off. The thesis is
focused on finding and documenting solution to linearity problem than can be used to
advance the performance of radio frequency (RF) and microwave systems used by the
wireless communication industry. The research work, this was undertaken by performing a
detailed investigation of the behaviour of transistors, under complex modulation, when
subjected to time varying baseband signals at their output terminal: This is what in this thesis
will be referred to as ābaseband injectionā. To undertake this study a new approach to the
characterisation of non-linear devices (NLD) in the radio frequency (RF) region, such as
transistors, designated as device-under-test (DUT), subjected to time varying baseband
signals at its output terminal, was implemented. The study was focused on transistors that are
used in implementing RF power amplifiers (RFPA) for base station applications. The nonlinear
device under test (NL-DUT) is a generalisation to include transistors and other nonlinear
devices under test. Throughout this thesis, transistors will be referred to as ādeviceā or
āradio frequency power amplifier (RFPA) deviceā. During baseband injection investigations
the device is perturbed by multi-tone modulated RF signals of different complexities. The
wireless communication industry is very familiar with these kinds of devices and signals.
Also familiar to the industry are the effects that arise when these kind of signal perturb these
devices, such as inter-modulation distortion and linearity, power consumption/dissipation and
efficiency, spectral re-growth and spectral efficiency, memory effects and trapping effects.
While the concept of using baseband injection to linearize RFPAs is not new the
mathematical framework introduced and applied in this work is novel. This novel approach
NOVEL POWER AMPLIFIER DESIGN USING NON-LINEAR MICROWAVE CHARACTERISATION AND MEASUREMENT TECHNIQUES CARDIFF UNIVERISTY - UK
ABSTRACT vi
has provided new insight to this very complex problem and highlighted solutions to how it
could be a usable technique in practical amplifiers.
In this thesis a very rigorous and complex investigative mathematical and measurement
analysis on RFPA response to applied complex stimulus in a special domain called the
envelope domain was conducted. A novel generic formulation that can āengineerā signal
waveforms by using special control keys with which to provide solution to some of the
problems highlighted above is presented.
The formulation is based on specific background principles, identified from the result of both
mathematical theoretical analysis and detailed experimental device characterisation