High efficiency is an essential requirement for any system, where the energy
can be saved with full retention of system performance. The power amplifier in
modern mobile communications system consumes most of the supplied power
through the dissipated power and the required cooling systems. However, as
new services were added as features for the developed mobile generations, the
required data rate has increased to fulfil the new requirements. In this case, the
data should be sent with the allocated bandwidth, so complex modulation
schemes are used to utilise the available bandwidth efficiently. Nevertheless,
the modulated signal will have a Peak to Average Power Ratio (PAPR) which
increases as the modulation complexity is increasing. In this case, the power
amplifier should be backed off and designed to provide good linearity and
efficiency over high PAPR.
Among the efficiency enhancement techniques, the Doherty technique (Load
modulation technique) is the simplest one, where no additional circuity nor
signal processing is required. In this work, the theory of load modulation
amplifiers is investigated through two asymmetrical Doherty Power Amplifiers
(DPA) targeting 3.3-3.5 GHz were designed and fabricated using two transistors
(25 W and 45 W). In addition, more compact load modulation amplifiers
targeting sub 6-GHz bandwidth of 5G specifically 3.4-3.8 GHz is discussed
including the theory of implementing these amplifiers, where different amplifier
capabilities are explored. Each amplifier design was discussed in detail, in
which the input and output matching networks were designed and tested in
addition to the design of the stability circuit to make sure that the amplifier is
stable and working according to the specified requirements. The fabricated
circuits were evaluated practically using the available instrument test, whereas
Microwave Office software was used for the simulation purpose, each amplifier
was designed separately, where all the designed amplifiers were able to provide
the targeted efficiency at different back-off power points. Besides, some
additional factors that affect the designed load modulation amplifiers such as
the effect of the harmonics at the back-off and mismatching the amplifier is
discussed. / European Union’s Horizon 2020 research and innovation programme (SECRET)
| Identifer | oai:union.ndltd.org:BRADFORD/oai:bradscholars.brad.ac.uk:10454/19128 |
| Date | January 2020 |
| Creators | Abdulkhaleq, Ahmed M. |
| Contributors | Abd-Alhameed, Raed, Noras, James M., McEwan, Neil J. |
| Publisher | University of Bradford, Faculty of Engineering and Informatics |
| Source Sets | Bradford Scholars |
| Language | English |
| Detected Language | English |
| Type | Thesis, doctoral, PhD |
| Rights | <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/"><img alt="Creative Commons License" style="border-width:0" src="http://i.creativecommons.org/l/by-nc-nd/3.0/88x31.png" /></a><br />The University of Bradford theses are licenced under a <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/">Creative Commons Licence</a>. |
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