GaN Monolithic Microwave Integrated Amplifiers for Space and Wireless Applications
AdvisorGhannouchi, Fadhel M.
AuthorAbounemra, Ahmed Mohammed Elelimy Ramadan
Committee MemberBelostotski, Leonid
ClassificationEngineering--Electronics and Electrical
SubjectBroadband Doherty power amplifier
Harmonic controlling network
Wide-band low noise amplifier
MetadataShow full item record
AbstractIn modern communication systems, such as the fourth-generation (4G) and fifth-generation (5G), the frequency spectrum needs to be fully utilized to support broadband applications and keep up with increasing user demand for high data rates. As an important component of the RF front-end in the transmitter, the power amplifier (PA) is used to convert the DC supply power into RF power. As the PA consumes most of the power in the transmitter, minimizing the power dissipation of the PA would have a significant effect on the efficiency of the whole transceiver. Doherty power amplifiers (DPAs) based on gallium nitride (GaN) transistors are poised to play a leading role in wireless base stations and repeaters in achieving high power efficiency and in meeting the linearity requirements set by wireless network standards. Although DPAs are widely utilized in field-deployed 4G base stations, they still suffer from many limitations. These limitations are mainly related to hardware imperfections in the RF blocks of the Doherty PA, such as narrow bandwidth and the gain imbalance between the main and the peak branches. Also, the large size of the circuit, because of the use of λ/4 transformers in the output combining network, is considered a critical problem for broadband DPA design. To adequately overcome the limitations of the Doherty PA, a new design methodology for Doherty architecture based on three-port input and output networks topology is proposed in the first part of this thesis. The output three-port network performs the impedance matching from any load impedance to the optimum loads, for both main and peak transistors and combines the power delivered from the two devices at any power ratio. The input splitting network is proposed for matching the input impedances of the two transistors to the source impedance. The freedom in choosing the power division ratio of the input network, enables us to achieve a tradeoff between efficiency and linearity. An asymmetric two-stage broadband Doherty amplifier is implemented using a 0.25-um GaN HEMT MMIC process to validate the proposed topology. The second part of the thesis concerns the study and the design of a wide-band harmonic controlling network (HCN) based DPA, using a new output combining network to achieve higher power efficiency over the broadband operating frequency range. In this design, the frequency sensitivity of the impedance inverters was compensated to minimize the efficiency degradation across the designed bandwidth. In many microwave systems, like radar and satellite applications, unwanted high input power levels such as jamming and interfering signals, affect LNAs. One of the characteristics of LNAs, designed using GaN technology, is the ability to endure these power levels with no need for using a limiter in front of the LNA. The third part of this dissertation presents a survivability study of wideband GaN HEMT LNA. It was concluded that GaN LNA can sustain relatively very high input power overdrive before device performance degradation or failure.
CitationAbounemra, A. M. E. R. (2021). GaN Monolithic Microwave Integrated Amplifiers for Space and Wireless Applications (Unpublished doctoral thesis). University of Calgary, Calgary, AB.
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