This thesis presents the theory, design, and implementation of two high power (>10 W) RF power amplifiers operating in the S-band (2 to 4 GHz) and employing the Class F mode of efficiency enhancement. The amplifiers are based around gallium nitride (GaN) high electron mobility transistors (HEMTs) which provide the high power capability. A complex wideband design using synthesized low-pass transforming filters as large-bandwidth matching networks is presented, followed by a more elegant narrowband design employing simple stub matching networks for impedance matching and harmonic control. Also presented in this thesis is a detailed study into the computer modeling of the GaN HEMT devices in order to accurately predict their behavior when integrated into a system. A complete small-signal circuit model is developed which is capable of predicting the scattering parameters of the devices with a high degree of accuracy to the measured behavior. Large-signal device models of increasing complexity are studied to investigate fundamental behaviors of field-effect transistors for which HEMTs are a subset. Finally, the manufacturer design kit’s computer model is investigated and verified for accuracy with the measured results.An overview of power amplifier design and classes of operation is given, and specifically Class F theory and implementation are analyzed. The efficiency enhancement by waveform shaping is studied, as well as the mechanism of waveform shaping via harmonic manipulation. Once fabricated and tested, the wideband design is shown to achieve at least 38.8 dBm output power between 2.2 to 3.3 GHz centered around 2.75 GHz, giving a fractional bandwidth of 40%. Over that range, the PA is able to sustain PAE > 40%, with a peak efficiency of 61%. The narrowband design achieves an output power at its center frequency of 3 GHz of 41.48 dBm, or ~14 W, with the PAE achieving a maximum of approximately 66%.

The textbook discusses design and analysis of microwave high power and high efficiency amplifiers for communications, appropriate for undergraduate, post-graduate students, practical circuit designers and researchers in the field of electronics and communication engineering. This book covers basics of III-V group semiconductor materials and GaAs and GaN based High Electron Mobility Transistors (HEMTs) most suitable for microwave and mm wave power amplifiers required for present wireless communication systems and upcoming 4G and 5G mobile base stations. The book describes design and analysis of classical class of amplifier operations such as Class-A, B, AB, C and F. The coverage extends to advanced classes of amplifier operation such as extended continuous Class-B/Class-J, and extended continuous Class-F operations for broadband, high power and high efficiency performance. Analytical expressions are derived for circuit elements and performance parameters for clear understanding and required for practical design of power amplifiers. Each topic is supplemented with suitable schematic diagrams, analytical expressions and plotted results for clear understanding.

This work has arisen out of the strong demand for a superior power-added efficiency (PAE) of AlGaN/GaN high electron mobility transistor (HEMT) high-power amplifiers (HPAs) that are part of any advanced wireless multifunctional RF-system with limited prime energy. Different concepts and approaches on device and design level for PAE improvements are analyzed, e.g. structural and layout changes of the GaN transistor and advanced circuit design techniques for PAE improvements of GaN HEMT HPAs.

This is a one-stop guide for circuit designers and system/device engineers, covering everything from CAD to reliability.

The modern wireless communication systems require modulated signals with wide modulation bandwidth. This, in turns, requires signals with very high dynamic range and peak-to-average power ratio (PAPR). This means that the amplifier in the base-station has to work at a power back-off as large as the dynamic range of the signal, so that the amplifier has a high linearity in this region. For the standard single-stage amplifiers, this large power back-off reduces the efficiency dramatically. In this work, a three-way Doherty power amplifier (DPA) aiming at high power efficiency within a dynamic range of 9.5 dB, is designed and fabricated using partitioning design approach. The partitioning design approach decomposes a complex design task into small-sized, well-controllable, and verifiable subcircuits. This advanced straight forward method has shown very promising results. Using this design approach, a three-way DPA has been designed to demonstrate the advantages of this reliable design technique as well. Based on the design of a single-stage power amplifier and proposing a novel output power combiner, a 6 W three-way DPA has been designed which allows the mandatory load modulation principle in three-way DPA structures to be realized with simpler elements, whereas the design of a standard Doherty combiner would have been very challenging and not practical due to the extremely small value of its characteristic line impedance. The proposed combiner is calculated for a three-way DPA with 2-mm AlGaN/GaN-HEMTs. The simulation result shows a very good load modulation for the amplifier, which confirms the theoretical expectation for a three-way DPA. The efficiency of the designed 6 W three-way DPA at large back-off shows very promising values compared to recently reported amplifiers. The measured IMD3 products confirm the good linearity of the amplifier as well. Accordingly, the proposed power combiner and the design strategy are recommended to be used as the preferred option for designing three-way DPA structures with very high output power.

This is a rigorous tutorial on radio frequency and microwave power amplifier design, teaching the circuit design techniques that form the microelectronic backbones of modern wireless communications systems. Suitable for self-study, corporate training, or Senior/Graduate classroom use, the book combines analytical calculations and computer-aided design techniques to arm electronic engineers with every possible method to improve their designs and shorten their design time cycles.