Design Of Mhz Power Amplifiers Using Wide Bandgap Devices

Power amplifiers are essential building blocks in many applications, including radio transmission, wireless power transfer, medical devices, and plasma generation. Conventional linear power amplifiers, such as Class A, Class AB, Class B, and Class C, have good linearity but low efficiencies. Switched-mode power amplifiers, such as Class D, Class E, and Class F2, can achieve a theoretical efficiency of 100%. However, these power amplifiers are designed to operate only at a fixed operating point, and changes in frequency or loading conditions can result in a significant degradation of their efficiencies and output power. Wireless power transfer systems and plasma generators are among the increasing number of applications that use high-frequency power converters. Increasing switching frequency can reduce the energy storage requirements of the passive elements that can lead to higher power densities or even the elimination of magnetic cores. However, operating at higher frequencies requires faster switching devices in packages with low-parasitics. Wide bandgap (WBG) power devices like gallium nitride (GaN) and silicon carbide (SiC) devices, have high critical fields and high thermal conductivity that make them good candidates for efficient high-voltage and high-frequency operations. Commercially available GaN and SiC devices have ratings targeting different applications. Lateral GaN devices dominate in lower-voltage (

Compact radio-frequency (RF) power amplifiers are essential building blocks in various applications, including radio transmission, medical imaging, wireless power transfer, industrial plasma generation, and micro-satellite propulsion. Over the past decades, new wide bandgap (WBG) semiconductor devices, particularly gallium nitride (GaN) and silicon carbide (SiC), were successfully commercialized. These devices, some specially designed and optimized for high-frequency operation, have theoretical benefits over silicon (Si) counterparts of multiple orders-of-magnitude. Consequently, they became the prime focus for those looking to further increase the power amplifier efficiency beyond what was previously possible. Unfortunately, while these WBG devices promise exceptional performances, recent studies have found that they possess additional undocumented loss mechanisms called dynamic on-resistance and junction capacitance Coss loss. To attain the maximum efficiency with these devices, additional design consideration and optimization is therefore needed. In this thesis, we address the challenges that are in the way of achieving a high-efficiency RF power amplifier system. The main goal is to improve and optimize how switched-mode amplifiers, specifically class-E amplifiers, are designed as much as possible so that high efficiency, high power, and fast control speed can be achieved simultaneously. First, to get the highest efficiency out of an amplifier with a WBG device, we present an analysis on how to select the optimal input voltage and the device size such that the two additional losses will be minimized. To enable the additional loss to be easily simulated, we also propose a distributed model for the loss, in analogy with the generalized Steinmetz equation. Second, to efficiently scale up the power, we present a unique design of a class-E amplifier called "power-combinable class-E, " which allows multiple amplifiers to be directly connected at the output combining the power. This eliminates the need for a separate power combiner circuit, a source of efficiency loss in a standard multi-amplifier system. Third, to adjust the output power of the proposed amplifier system, we develop a new power modulation scheme called the Modular On/Off and Phase-Shifting control. This control technique requires no additional component to be added to the circuit. In Modular On/Off, a different number of sub-circuits are turned on/off to crudely control the output power. In Phase-Shifting, one sub-circuit is phase-shifted away from the rest to finely adjust the output power. Finally, we examine a broader aspect of optimization. We look at a wireless power transfer (WPT) system employing a power amplifier as a single unit to be optimized. Specifically, we consider the hurdles that prevent the high-frequency WPT system's adoption and present a method to improve the circuit's efficiency as well as reduce its size by designing the WPT coils such that their leakage and magnetizing inductances can be used as resonating inductors for the class-E power amplifiers.

Emerging wide bandgap (WBG) semiconductors hold the potential to advance the global industry in the same way that, more than 50 years ago, the invention of the silicon (Si) chip enabled the modern computer era. SiC- and GaN-based devices are starting to become more commercially available. Smaller, faster, and more efficient than their counterpart Si-based components, these WBG devices also offer greater expected reliability in tougher operating conditions. Furthermore, in this frame, a new class of microelectronic-grade semiconducting materials that have an even larger bandgap than the previously established wide bandgap semiconductors, such as GaN and SiC, have been created, and are thus referred to as “ultra-wide bandgap” materials. These materials, which include AlGaN, AlN, diamond, Ga2O3, and BN, offer theoretically superior properties, including a higher critical breakdown field, higher temperature operation, and potentially higher radiation tolerance. These attributes, in turn, make it possible to use revolutionary new devices for extreme environments, such as high-efficiency power transistors, because of the improved Baliga figure of merit, ultra-high voltage pulsed power switches, high-efficiency UV-LEDs, and electronics. This Special Issue aims to collect high quality research papers, short communications, and review articles that focus on wide bandgap device design, fabrication, and advanced characterization. The Special Issue will also publish selected papers from the 43rd Workshop on Compound Semiconductor Devices and Integrated Circuits, held in France (WOCSDICE 2019), which brings together scientists and engineers working in the area of III–V, and other compound semiconductor devices and integrated circuits. In particular, the following topics are addressed: – GaN- and SiC-based devices for power and optoelectronic applications – Ga2O3 substrate development, and Ga2O3 thin film growth, doping, and devices – AlN-based emerging material and devices – BN epitaxial growth, characterization, and devices

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.

The need for high power, highly efficient, multi-band and multi-mode radio frequency (RF) and microwave power amplifiers in the commercial and defense wireless industries continues to drive the research and development of gallium nitride (GaN) devices and their implementation in the receiver and transmitter lineups of modern microwave systems. Unlike silicon (Si) or gallium arsenide (GaAs), GaN is a direct wide bandgap semiconductor that permits usage in high voltage and therefore high power applications. Additionally, the increased saturation velocity of GaN allows for operation well into the super high frequency (SHF) portion of the RF spectrum. For the power amplifier designer, active devices utilizing GaN will exhibit power densities almost an order of magnitude greater than comparably sized GaAs devices and almost two orders of magnitude greater than Si devices. Not only does this mean an overall size reduction of an amplifier for a given output power, but it allows GaN to replace specialized components such as the traveling-wave tube (TWT) and other circuits once deemed impossible to realize using solid-state electronics. Designs utilizing GaN in amplifiers, switches, mixers, etc., are able to meet the continually shrinking size, increased power, stringent thermal, and cost requirements of a modern microwave system.There are two relatively straight forward methods used to investigate the intrinsic power scaling properties of a GaN high-electron-mobility transistor (HEMTs) configured as a common source amplifier. The first method involves sweeping the applied drain to source voltage bias and the second method involves scaling the physical size of the transistor. The prior method can be used to evaluate fixed sized transistors while the latter method requires an understanding of the obtainable power density for a given device technology prior to fabrication. Since the power density is also a function of the drain to source voltage bias, an initial iterative component of the design cycle may be required to fully characterize the device technology. If a scalable nonlinear device model is available to the designer, the harmonic balance simulator in most computer aided design (CAD) tools can be used to evaluate device parameters such as the maximum output power and power added efficiency (PAE) using large signal load pull simulations.The circuits presented in this thesis address two power amplifier design approaches commonly used in industry. The first approach utilizes commercially available bare die GaN transistors that can be wire-bonded to matching circuitry on a printed circuit board (PCB). This technique is known as hybrid packaging. The second approach utilizes a fully integrated design or monolithic microwave integrated circuit (MMIC) and the process design kit (PDK) used to design, simulate and layout the power amplifier circuitry before submission to a foundry for fabrication. In both cases, the nonlinear transistor models are used to investigate the power scalability of class E mode GaN power amplifiers and the techniques used to implement such circuits. The design, results, and challenges of each approach are discussed and future work is presented.

Motivated by recent advances in wide-bandgap (WBG) gallium nitride (GaN) semiconductor technology, there is considerable interest in developing efficient solidstate power amplifiers (SSPAs) as an alternative to the traveling-wave tube amplifier (TWTA) for space applications. This article documents the results of a study to investigate power-combining technology and SSPA architectures that can enable a 120-W, 40 percent power-added efficiency (PAE) SSPA. Results of the study indicate that architectures based on at least three power combiner designs are likely to enable the target SSPA. The proposed architectures can power combine 16 to 32 individual monolithic microwave integrated circuits (MMICs) with >80 percent combining efficiency. This corresponds to MMIC requirements of 5- to 10-W output power and >48 percent PAE. For the three proposed architectures [1], detailed analysis and design of the power combiner are presented. The first architecture studied is based on a 16-way septum combiner that offers low loss and high isolation over the design band of 31 to 36 GHz. Analysis of a 2-way prototype septum combiner had an input match >25 dB, output match >30 dB, insertion loss 30 dB over the design band. A 16-way design, based on cascading this combiner in a binary fashion, is documented. The second architecture is based on a 24-way waveguide radial combiner. A prototype 24-way radial base was analyzed to have an input match >30 dB (under equal excitation of all input ports). The match of the mode transducer that forms the output of a radial combiner was found to be >27 dB. The functional bandwidth of the radial base and mode transducer, which together will form a radial combiner/divider, exceeded the design band. The third architecture employs a 32-way, parallel-plate radial combiner. Simulation results indicated an input match >24 dB, output match >22 dB, insertion loss

This book focuses on broadband power amplifier design for wireless communication. Nonlinear model embedding is described as a powerful tool for designing broadband continuous Class-J and continuous class F power amplifiers. The authors also discuss various techniques for extending bandwidth of load modulation based power amplifiers, such as Doherty power amplifier and Chireix outphasing amplifiers. The book also covers recent trends on digital as well as analog techniques to enhance bandwidth and linearity in wireless transmitters. Presents latest trends in designing broadband power amplifiers; Covers latest techniques for using nonlinear model embedding in designing power amplifiers based on waveform engineering; Describes the latest techniques for extending bandwidth of load modulation based power amplifiers such as Doherty power amplifier and Chireix outphasing amplifiers; Includes coverage of hybrid analog/digital predistortion as wideband solution for wireless transmitters; Discusses recent trends on on-chip power amplifier design with GaN /GaAs MMICs for high frequency applications.

As demand for electric vehicles (EVs) grows, wireless power transfer (WPT) technology becomes beneficial by removing the need for manual intervention to charge EV batteries. These high-power applications require power electronics systems that not only efficiently deliver sufficient power, but are also small enough to be embedded in the EV. However, while the size of other vehicle components has shrunk considerably over the past decade, that of power electronics systems has not. This presents a major challenge to making power electronics systems for EVs, plasma generation and other high-power industrial applications both efficient and small. This dissertation describes the design and implementation of efficient, compact power electronics systems for charging EVs and other industrial applications, as well as their extensions to WPT. A large part of this work involves overcoming technical limitations by designing high-power (above 2 kW) and high-efficiency (above 90%) systems to operate at tens of MHz switching frequency. First, wide bandgap (WBG) devices such as silicon carbide (SiC) MOSFETs or enhancement mode gallium nitride (eGaN) FETs are used to reduce the size and weight of the entire WPT system and improve system performance. With SiC MOSFETs and eGaN FETs, 2 kW resonant inverters and resonant rectifiers for WPT systems can successfully operate at 13.56 MHz switching frequency. Thus, this work opens up the possibility of achieving kilowatt-level output powers at MHz switching frequencies. After implementing a high-efficiency resonant inverter for the WPT system, the coupling coils must be designed very carefully to deliver power with high efficiency over a mid-range coil distance. Therefore, an open-type four-coil unit is also presented in this work. The advantage of the coils is that the resonant frequency can be changed by adjusting the length of copper wire and distance between two coils. Using this type of coil unit eliminates the need for external capacitors that incur additional losses. However, even when the coupling coils are designed and implemented perfectly to provide high efficiency, the WPT system performance may decrease because of misalignments between the transmitting and receiving coils. Specifically, resonant converters are sensitive to load variation, which increases losses in switching devices. The impedance of magnetic resonant coupling (MRC) coils seen by inverters can be easily changed according to the distance or alignment between transmitting and receiving coils. This is one of the main factors that degrades the overall efficiency of WPT systems. To overcome this issue, this dissertation introduces a new kind of matching network, called an impedance compression network (ICN), to maintain the robustness of coil efficiency in various coil positions. An ICN consisting of a resistance compression network (RCN) and a phase compression network (PCN) was designed and implemented to compensate for distance and alignment variations between coils in a WPT system. Using an ICN helps maintain zero voltage switching (ZVS) and zero dv/dt operation in a resonant inverter and achieve system performance of over 90% efficiency. While WPT systems offer a convenient way to enable high-power applications, a critical unresolved concern is the safety of these systems. This dissertation presents two safety guidelines for EMF exposure and previous studies that evaluate human exposure level compared to the values recommended in the regulations. However, the limits of human exposure to electric, magnetic and electromagnetic fields in high-power WPT systems have not been clearly demonstrated yet. Based on the guidelines and the previous research, future research is required to evaluate EMF exposure in high-frequency, high-power WPT systems. One of the challenges in designing WPT systems for EVs is the need to combine power amplifiers to obtain higher power levels. To address this problem, this dissertation proposes a power-combining resonant inverter that can be applied not only to WPT systems, but also plasma generation and other industrial applications. Current RF power amplifiers for plasma generation operate at very high frequency (VHF), but provide low efficiency around 70% because they use linear amplifier topologies. Using a resonant inverter with WBG devices provides high power while maintaining high efficiency in a 40.68 MHz plasma-generation system. However, WBG devices cannot effectively dissipate heat at frequencies above 40 MHz. To reduce the losses in each eGaN FET, a power-combining inverter based on a class Phi2 inverter is designed and implemented to provide 1.2 kW output power at 40.68 MHz. A configurable method used to tune a class Phi2 inverter allows us to easily connect four of them in parallel to create a power-combining inverter that can achieve up to 1.2 kW output power. Also, the proposed inverter topology reduces the power loss in each switching device, improving the power density of the resonant inverter. In conclusion, this dissertation proposes high-frequency, high-power resonant converters with WBG devices to improve the power density and efficiency of both WPT and plasma generation systems. Furthermore, it presents a novel ICN topology that mitigates misalignment problems caused by MRC coils.

Advances in electronics have pushed mankind to create devices, ranging from - credible gadgets to medical equipment to spacecraft instruments. More than that, modern society is getting used to—if not dependent on—the comfort, solutions, and astonishing amount of information brought by these devices. One ?eld that has continuously bene?tted from those advances is the radio frequency integrated c- cuit (RFIC) design, which in its turn has promoted countless bene?ts to the mankind as a payback. Wireless communications is one prominent example of what the - vances in electronics have enabled and their consequences to our daily life. How could anyone back in the eighties think of the possibilities opened by the wireless local area networks (WLANs) that can be found today in a host of places, such as public libraries, coffee shops, trains, to name just a few? How can a youngster, who lives this true WLAN experience nowadays, imagine a world without it? This book dealswith the design oflinearCMOS RF PowerAmpli?ers(PAs). The RF PA is a very important part of the RF transceiver, the device that enables wireless communications. Two important aspects that are key to keep the advances in RF PA design at an accelerate pace are treated: ef?ciency enhancement and frequen- tunable capability. For this purpose, the design of two different integrated circuits realizedina0. 11μmtechnologyispresented,eachoneaddressingadifferentaspect. With respect to ef?ciency enhancement, the design of a dynamic supply RF power ampli?er is treated, making up the material of Chaps. 2 to 4.

This practical resource offers expert guidance on the most critical aspects of microwave power amplifier design. This comprehensive book provides descriptions of all the major active devices, discusses large signal characterization, explains all the key circuit design procedures. Moreover you gain keen insight on the link between design parameters and technological implementation, helping you achieve optimal solutions with the most efficient utilization of available technologies. The book covers a broad range of essential topics, from requirements for high-power amplifiers, device models, phase noise and power combiners... to high-efficiency amplifiers, linear amplifier design, bias circuits, and thermal design.