Effective electrothermal analysis of electronic devices and systems with parameterized macromodeling

We propose a parameterized macromodeling methodology to effectively and accurately carry out dynamic electrothermal (ET) simulations of electronic components and systems, while taking into account the influence of key design parameters on the system behavior. In order to improve the accuracy and to reduce the number of computationally expensive thermal simulations needed for the macromodel generation, a decomposition of the frequency-domain data samples of the thermal impedance matrix is proposed. The approach is applied to study the impact of layout variations on the dynamic ET behavior of a state-of-the-art 8-finger AlGaN/GaN high-electron mobility transistor grown on a SiC substrate. The simulation results confirm the high accuracy and computational gain obtained using parameterized macromodels instead of a standard method based on iterative complete numerical analysis

A survey on RF and microwave doherty power amplifier for mobile handset applications

This survey addresses the cutting-edge load modulation microwave and radio frequency power amplifiers for next-generation wireless communication standards. The basic operational principle of the Doherty amplifier and its defective behavior that has been originated by transistor characteristics will be presented. Moreover, advance design architectures for enhancing the Doherty power amplifier’s performance in terms of higher efficiency and wider bandwidth characteristics, as well as the compact design techniques of Doherty amplifier that meets the requirements of legacy 5G handset applications, will be discussed.Agencia Estatal de Investigación | Ref. TEC2017-88242-C3-2-RFundação para a Ciência e a Tecnologia | Ref. UIDP/50008/201

A Directly Matched PA-Integrated K-band Antenna for Efficient mm-Wave High-Power Generation

A K-band slot antenna element with integrated GaN (Gallium nitride) power amplifier (PA) is presented. It has been optimized through a circuit-EM co-design methodology to directly match the transistor drain output to its optimal load impedance (\ua0Zopt=17+j46Ω\ua0) while accounting for the over-the-air coupling effects in the vicinity of the transition between the PA and antenna. This obviates the need for using a potentially lossy and bandwidth-limiting output impedance matching network. The measured PA-integrated antenna gain of 15 dBi with a 40% total efficiency at 28 dBm output power agrees well with the theoretically achievable performance targets. The proposed element is compact (\ua00.6 70.5 70.3\ua0λ3\ua0), and thus well-suited to meet the high-performance demands of future emerging beamforming active antenna array applications

High Electron Mobility Transistors: Performance Analysis, Research Trend and Applications

In recent years, high electron mobility transistors (HEMTs) have received extensive attention for their superior electron transport ensuring high speed and high power applications. HEMT devices are competing with and replacing traditional field‐effect transistors (FETs) with excellent performance at high frequency, improved power density and satisfactory efficiency. This chapter provides readers with an overview of the performance of some popular and mostly used HEMT devices. The chapter proceeds with different structures of HEMT followed by working principle with graphical illustrations. Device performance is discussed based on existing literature including both analytical and numerical models. Furthermore, some notable latest research works on HEMT devices have been brought into attention followed by prediction of future trends. Comprehensive knowledge of up‐to‐date results, future directions, and their analysis methodology would be helpful in designing novel HEMT devices

Co-Design and Validation Approach for Beam-Steerable Phased Arrays of Active Antenna Elements with Integrated Power Amplifiers

An approach for designing a beam-steering active phased array of antenna elements with integrated power amplifiers (PAs) is presented. It is based on an amplifying active integrated unit cell (AiUC) concept, where the AiUC comprises a radiating slot element, a GaN high electron mobility transistor (HEMT), its input matching and DC biasing/feeding circuitry. The HEMT is embedded in the antenna element, being directly impedance-matched to HEMT’s drain output, i.e. without using any intermediate and potentially lossy impedance matching network. The proposed co-design approach involves a full-wave analysis of the AiUC passive part (naturally including elements mutual coupling effects) along with the subsequent full system harmonic balance simulations. Furthermore, we extend the standard definition of the scan element pattern (SEP) to the active scan element pattern (ASEP) that accounts for nonlinear effects of PAs on AiUC performance. We show that the ASEP is, in general, power-dependent and has a different shape as compared to the SEP. The proposed approach has been demonstrated for a K-band AiUC design example. It was verified through an active waveguide simulator, which is equivalent to the 23.7\ub0 H-plane beam-steering case. Measurements are in good agreement with simulations, revealing AiUC 47% peak drain efficiency and 33 dBm maximum radiated power. The predicted scan range is \ub160\ub0 and \ub137\ub0 in the E- and H-plane, respectively

O impacto dos efeitos da memória de longo termo na linearizabilidade de amplificadores de potência baseados em AlGaN/GaN HEMT

AlGaN/GaN High Electron Mobility Transistor (HEMT)s are among the preferred options for radio-frequency power amplification in cellular base station transmitters and radar applications. However, despite their promising outlook, the pervasiveness of trapping effects makes them resilient to conventional digital predistortion schemes, which not only decrease their current range of applications but could also preclude their integration in future small cells and multiple-input multiple-output architectures where simpler predistortion schemes are mandatory. So, this PhD thesis aims at developing a meaningful link between the device physics and the linearizability of the AlGaN/GaN HEMT-based Power Amplifier (PA). In order to bridge this gap, this thesis begins with a clear explanation for the mechanisms governing the dominant source of trapping effects in standard AlGaN/GaN HEMTs, namely buffer traps. Based on this knowledge, we explain why the best known physically-supported trapping models, used to represent these devices, are insufficient and present a possible improvement to what we consider to be the most accurate model, supported by Technology Computer-Aided Design (TCAD) simulations. This has also been corroborated through a novel double-pulse technique able to describe experimentally both the capture and emission transients in a wide temporal span under guaranteed isothermal conditions. The measured stretched capture transients validated our understanding of the process while the temperature dependence of the emission profiles confirmed buffer traps as the dominant source of trapping effects. Finally, through both simulations and experimental results, we elaborate here the relationship between the emission time constant and the achievable linearity of GaN HEMT-based PAs, showing that the worst-case scenario happens when the emission time constant is on the order of the time between consecutive envelope peaks above a certain amplitude threshold. This is the case in which we observed a more pronounced hysteresis on the gain and phase-shift characteristics, and so, a stronger impact of the memory effects. The main outcome of this thesis suggests that the biggest linearizability concern in standard AlGaN/GaN HEMT-based PAs lies on the large emission time constants of buffer traps.AlGaN/GaN HEMTs estão entre as opções preferidas para amplificação de potência de radiofrequência em transmissores de estacão base celular e aplicações de radar. No entanto, apesar de sua perspetiva promissora, a influência dos efeitos de defeitos com níveis profundos torna-os imunes aos esquemas convencionais de pre-distorção digital. Assim, esta tese de doutoramento visa desenvolver uma ligação significativa entre a física do dispositivo e a linearização de amplificadores de potência baseados em Al- GaN/GaN HEMTs. Por forma a preencher esta lacuna, esta tese começa com uma explicação clara dos mecanismos que governam a fonte dominante de efeitos de defeitos com níveis profundos em AlGaN/GaN HEMTs standard, especificamente defeitos no buffer. Com base neste conhecimento, são aparentadas as falhas dos modelos físicos mais conhecidos de defeitos de nível profundo usados para representar estes dispositivos, assim como uma possível melhoria suportada em simulações de TCAD. Isto é também corroborado por uma nova técnica de duplo-pulso capaz de descrever experimentalmente os transientes de captura e emissão num amplo intervalo temporal sob condições isotérmicas. Os transientes de captura medidos validam a nossa compreensão do processo, enquanto que a dependência da temperatura nos perfis de emissão confirmou os defeitos no buffer como a fonte dominante de efeitos de defeitos com níveis profundos. Por fim, através de simulações e resultados experimentais, elabora-se aqui a relação entre a constante de tempo de emissão e a linearizabilidade dos amplificadores baseados em AlGaN/GaN HEMT, mostrando que o pior cenário acontece quando a constante de tempo de emissão é da mesma ordem do tempo entre picos consecutivos da envolvente acima de um certo limiar de amplitude. Este é o caso para o qual se observa uma histerese mais pronunciada nas características de ganho e fase e, consequentemente, um impacto mais forte dos efeitos de memória. O resultado principal desta tese sugere que a maior preocupação na linearização de amplificadores baseados em AlGaN/GaN HEMTs standard está nas grandes constantes de tempo de emissão dos defeitos no buffer.Programa Doutoral em Engenharia Eletrotécnic

Contributing to Second Harmonic Manipulated Continuum Mode Power Amplifiers and On-Chip Flux Concentrators

The current cellular network consumes a staggering 100 TWh of energy every year. In the coming years, millions of devices will be added to the existing network to realize the Internet of Things (IoT), further increasing its power consumption. An RF power amplifier typically consumes a large proportion of the DC power in a wireless transceiver, improving its efficiency has the largest impact on the overall system. Additionally, amplifiers need to demonstrate high linearity and bandwidth to adhere to constraints imposed by wireless standards and to reduce the number of amplifiers required as an amplifier with a broader bandwidth can potentially replace several narrowband amplifiers. A typical approach to improve efficiency is to present an appropriate load at the harmonics generated by the transistor. Recently proposed continuous modes based on harmonic manipulation, such as class B/J continuum, continuous class F (CCF) and continuous class F-1 (CCF-1), have shown the capability of achieving counteracting requirements viz., high efficiency, high linearity, and broad bandwidth (with a fractional bandwidth greater than 30%). In these classes of amplifiers, the second harmonic is manipulated by placing a reactive second harmonic load and the reactive component of the fundamental load is adjusted while keeping a fixed resistive component of the fundamental load. The first contribution of this work is to investigate the reason for amplifiers designed in classes B/J continuum and CCF to achieve high efficiency at back-off and 1dB compression. In this thesis, we demonstrate that the variation of the phase of the current through the non-linear intrinsic capacitances due to the variation of the phase in the continuum of drain voltage waveforms in Class B/J/J* continuum leads to either a reduction or enhancement of intrinsic drain current. Consequently, a subset of voltage waveforms of the class B/J/J* continuum can be used to design amplifiers with higher P1dB, and efficiency at P1dB than in Class B. A simple choice of this subset is demonstrated with a 2.6GHz Class B/J/J* amplifier, achieving a P1dB of 38.1dBm and PAE at P1dB of 54.7%, the highest output power and efficiency at P1dB amongst narrowband linear amplifiers using the CGH40010 reported to date, at a comparable peak PAE of 72%. Secondly, we propose a new formulation for high-efficiency modes of power amplifiers in which both the in-phase and out-of-phase components of the second harmonic of the current are varied, in addition to the second harmonic component of the voltage. A reduction of the in-phase component of the second harmonic of current allows reduction of the phase difference between the voltage and current waveforms, thereby increasing the power factor and efficiency. Our proposed waveforms offer a continuous design space between class B/J continuum and continuous F-1 achieving an efficiency of up to 91% in theory, but over a wider set of load impedances than continuous class F-1. These waveforms require a short at third and higher harmonic impedances, which are easier to achieve at a higher frequency. The load impedances at the second harmonic are reactive and can be of any value between -j∞ and j∞, easing the amplifier design. A trade-off between linearity and efficiency exists in the newly proposed broadband design space, but we demonstrate inherent broadband capability. The fabricated narrowband amplifier using a GaN HEMT CGH40010F demonstrates 75.9% PAE and 42.2 dBm output power at 2.6 GHz, demonstrating a comparable frequency weighted efficiency for this device to that reported in the literature. IoT devices may be deployed in critical applications such as radar or 5G transceivers of an autonomous vehicle and hence need to operate free of failure. Monitoring the drain current of the RF GaN MMIC would allow to optimize the device performance and protect it from surges in its supply current. Galvanic current sensors rely on the magnetic field generated by the current as a non-invasive method of current sensing. In this thesis, our third major contribution is a planar on-chip magnetic flux concentrator, is enhance the magnetic field at the current sensor, thereby improving the current detection capability of a current sensor. Our layout utilizes a discontinuity in a magnetic via, resulting in penetration of the magnetic field into the substrate. The proposed concentrator has a magnetic gain x1.8 in comparison to air. The permeability of the magnetic core required is 500, much lower than that reported in off-chip concentrators, resulting in a significant easing of the specifications of the material properties of the core. Additionally, we explore a novel three-dimensional spiral-shaped magnetic flux concentrator. It is predicted via simulations that this geometry becomes a necessity to enhance the magnetic field for increased form factor as the magnetic field from a single planar concentrator deteriorates as its size increases

Physics-Based Compact Model for p-GaN/AlGaN/GaN. Application: Understanding of Degradation After Gamma-Ray Irradiation

This thesis explores the nature of gallium nitride devices from the point of view of compact modeling paying particular attention to power electronic application. To model the behavior of such devices, the physics of the typical GaN HEMT is studied by solving the Schrodinger's and Poisson's equations. The Physical-Based model is used to help our understanding of the effect of gamma irradiation on GaN based devices

Distributed Modeling Approach for Electrical and Thermal Analysis of High-Frequency Transistors

The research conducted in this dissertation is focused on developing modeling approaches for analyzing high-frequency transistors and present solutions for optimizing the device output power and gain. First, a literature review of different transistor types utilized in high-frequency regions is conducted and gallium nitride high electron mobility transistor is identified as the promising device for these bands. Different structural configurations and operating modes of these transistors are explained, and their applications are discussed. Equivalent circuit models and physics-based models are also introduced and their limitations for analyzing the small-signal and large-signal behavior of these devices are explained. Next, a model is developed to investigate the thermal properties of different semiconductor substrates. Heat dissipation issues associated with some substrate materials, such as sapphire, silicon, and silicon carbide are identified, and thinning the substrates is proposed as a preliminary solution for addressing them. This leads to a comprehensive and universal approach to increase the heat dissipation capabilities of any substrate material and 2X-3X improvement is achieved according to this novel technique. Moreover, for analyzing the electrical behavior of these devices, a small-signal model is developed to examine the operation of transistors in the linear regions. This model is obtained based on an equivalent circuit which includes the distributed effects of the device at higher frequency bands. In other words, the wave propagation effects and phase velocity mismatches are considered when developing the model. The obtained results from the developed simulation tool are then compared with the measurements and excellent agreement is achieved between the two cases, which serves as the proof for validation. Additionally, this model is extended to predict and analyze the nonlinear behavior of these transistors and the developed tool is validated according to the obtained large-signal analysis results from measurement. Based on the developed modeling approach, a novel fabrication technique is also proposed which ensures the high-frequency operability of current devices with the available fabrication technologies, without forfeiting the gain and output power. The technical details regarding this approach and a sample configuration of the electrode model for the transistor based on the proposed design are also provided