class-E Power Amplifier Research Articles

Design of a differential power oscillator for 433 MHz WPT using e-GaN HEMTs

This paper presents a new differential power oscillator design based on a differential class-E power amplifier. The designs use high power enhancement-GaN HEMT (e-GaN) for its fast switching time, low ON resistance and wide energy band gap properties. The target application is far field wireless power transfer for wireless charging applications. The initial guess for design parameters follows the well known Sokal approach then LTSpice simulator is used to finalize the design. The simulated output power of the power oscillator is 60 W at the 433 MHz ISM band with high DC-to-RF conversion efficiency. Effect of process and design parameter variability is considered to assess the design sensitivity to manufacturing tolerances in both active and passive components.

High-Efficiency Class-E Power Amplifiers for mmWave Radar Sensors: Design and Implementation

This article presents high-efficiency power amplifiers (PAs) implemented in Texas Instruments’ (TI) 130-nm BiCMOS process for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V$ </tex-math></inline-formula> - and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$E$ </tex-math></inline-formula> -band millimeter-wave (mmWave) radar sensors. A new Class-E output network based on a doubly tuned (DT) transformer is proposed to enable high-efficiency mmWave operation. The proposed Class-E network allows increasing PA device size beyond the traditional Class-E design limits while preserving nonoverlapping Class-E current and voltage waveforms. Design examples for single-ended and differential implementation of the proposed Class-E network are presented in this article. Three PA prototypes (a 79-GHz two-stage PA, a 63-GHz single-stage PA, and a 79-GHz single-stage PA) have been designed and fabricated in a high-volume production 130-nm BiCMOS process. A Class-E interstage network with a split-and-combine 45° transformer is employed in the two-stage PA to ease driving the last stage PA devices. Device layout optimization for improved efficiency is described in this article. The measurement results achieve a peak power-added efficiency (PAE) of 30.5%/34.7%/32.6% with an output power of 17/18.1/17 dBm for the 79-GHz two-stage, 63-GHz single-stage, and 79-GHz single-stage PAs, respectively. To the best of our knowledge, these are the record PAE numbers reported for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V$ </tex-math></inline-formula> - and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$E$ </tex-math></inline-formula> -band PAs in any silicon process, demonstrating the efficacy of the proposed DT transformer-based Class-E output network.

Analysis and design of class-E power amplifier considering MOSFET nonlinear capacitance

Class-E power amplifiers are integrated into many applications because their simple design and high performance. The efficiency of the power amplifier is significantly impacted by the nonlinear characteristic of the switching device, which is not analyzed clearly in theory. The nonlinear drain-to-source parasitic capacitance of the power transistor and the linear external capacitance are both contributed to the optimum conditions for obtaining the exact shunt capacitance. In this paper, a high-efficiency class-E power amplifier with shunt capacitance is designed with the consideration of both linear and nonlinear capacitance. Furthermore, a mathematical analysis is derived to calculate the component values in order to design the class-E power amplifier. Consequently, high power-added efficiency of 94.6% is obtained using MRF9030 MOSFET transistor with parameter of 4W output power and 13.56 MHz operating frequency. Finally, the measurement result of a linear class-E power amplifier circuit is obtained to compare and realize the efficiency of the proposed work.

Wireless Drone Charging Station Using Class-E Power Amplifier in Vertical Alignment and Lateral Misalignment Conditions

Recent major advancements in drone charging station design are related to the differences in coil design between the material (copper or aluminum) and inner thickness (diameter design) to address power transfer optimization and increased efficiency. The designs are normally challenged with reduced weight on the drone’s side, which can lead to reduced payload or misalignment position issues between receiver and transmitter, limiting the performance of wireless charging. In this work, the coil combination was tested in vertical alignment from 2 cm to 50 cm, and in lateral misalignment positions that were stretched across 2, 5, 8, 10, and 15 cm ranges. Simulated and experimental results demonstrated improved transfer distances when the drone battery load was 100 Ω. With the proposed design, the vertical transfer power that was achieved was 21.12 W, 0.460 A, with 81.5% transfer efficiency, while the maximum lateral misalignment air gap that was achieved was 2 cm with 19.22 W and 74.15% efficiency. This study provides evidence that the developed circuit that is based on magnetic resonant coupling (MRC) is an effective technique towards improving power transfer efficiency across different remote and unmanned Internet of Things (IoT) applications, including drones for radiation monitoring and smart agriculture.

Computer‐aideddesign methodology for inductive compensated microwaveclass‐Epower amplifier

This article presents a simulation-based analysis to first evaluate the impact of excessive transistor output capacitance on class-E power amplifiers and to second show how inductive compensation can be used to recover optimum class-E operating conditions. As a starting point, the finite-feed inductor in a parallel-circuit topology is replaced by a frequency-dependent inductor, which in turn can be substituted by a network composed of a series inductor and additional subharmonic resonators. This complex lumped-element network is then replaced by a generalized transmission line equivalent topology, suitable for microwaves. Calculation of the transmission line impedances and electrical lengths of the proposed generalized network is shown in detail and a design procedure for this modified class-E is provided. The analysis presented here is further extended by using a simplified large-signal model for the employed GaN HEMT device, which allows evaluating the effects of non-ideal switching as well as of capacitance voltage-dependency and feedback capacitance. The analysis is validated by simulation and design of a test board. Measurements of the test board showed a drain efficiency of 80.3%, power-added efficiency of 76.3% and output power of 40.1 dBm at 1.96 GHz, demonstrating the validity of the proposed approach.

Shielded Capacitive Power Transfer (S-CPT) without Secondary Side Inductors

In this study, we propose a four-plate structure with two shielding plates to produce shielded capacitive power transfer (S-CPT) at an operating frequency of 6.78 MHz for a 10 W system. By eliminating the inductors at the secondary side to form an asymmetrical topology, an S-CPT system was developed with a class-E power amplifier. Using MATLAB software, analysis was performed to obtain the parameters in the S-CPT system regarding resonance and impedance matching, and the proposed coupler structure was investigated through electric field simulation. The shield plate voltage stability was also investigated by analysing both the simulation and hardware experiment results. A prototype of S-CPT was established to validate the analysis results and to demonstrate the voltage at the shield plate of the proposed coupler structure. The experimental results are in good agreement with the simulation results. The proposed S-CPT exhibits an AC–AC efficiency of 84%, with a 56% voltage ground stability reduction because of implementing a balun.

Impedance Matching Method for 6.78 MHz Class-E2-Based WPT System

The performance of a conventional Class-E2-based WPT system is sensitive to system parameters such as the coil coupling coefficient and load variation. System efficiency decreases rapidly when the coil coupling coefficient and load deviate from their optimum values. In this paper, an impedance matching method and a design procedure are proposed to maintain high system efficiency over a wider range of coupling coefficient and load variations. The load-pull technique is adopted to identify the high-efficiency load region of a Class-E power amplifier (PA), and a double-L-type impedance matching network (IMN) is proposed to transform the load impedance of a Class-E PA into a high-efficiency working region. Compared to a single L-type IMN, a double-L-type IMN is more flexible and has better tuning performance. A 6.78 MHz Class-E2-based WPT system was built to validate the proposed design method. The experimental results show that the proposed double-L-type IMN can significantly attenuate the decline in Class-E PA efficiency when system parameters dynamically change. With a double-L-type IMN, the WPT system could maintain high efficiency (over 55%) under a wider range of coil coupling coefficient and load variations. The peak system efficiency reached 83.2% with 13.7 W output power. The impedance matching method and design procedure in this paper could provide a practical solution for building a high-efficiency WPT system with strong robustness.

A Modified Design of Class-E Power Amplifier with Balanced FETs and High Output Power for RFID Applications

In Radio Frequency (RF) communication, a Power Amplifier (PA) is used to amplify the signal at the required power level with less utilization of Direct Current (DC) power. The main characteristic of class-E PA is sturdy nonlinearity due to the switching mode action. In this study, a modified design of class-E PA with balanced Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) and high output power for Electronic Article Surveillance (EAS) Radio Frequency Identification (RFID) application is presented. MOSFETs are adjusted to have high output performance of about 80% for RFID-based EAS system. A matching network is also proposed for accurate matching because there are differences in the behavior between RF waves and low frequency waves. The design of a matching network is a tradeoff among the complexity, adjustability, implementation, and bandwidth for the required output power and frequency. The implemented PA is capable of providing 44.8 dBm output power with Power-Added Efficiency (PAE) of 78.5% at 7.7 MHz to 8.7 MHz.

Design, Simulation and Fabrication of Broadband Class-E Power Amplifier Using Double-Reactance Compensation Technique and Second and Third Harmonic Control Circuits

Design, Simulation and Fabrication of Broadband Class-E Power Amplifier Using Double-Reactance Compensation Technique and Second and Third Harmonic Control Circuits

Performance Tradeoff Analysis of Hybrid Signaling SWIPT Systems with Nonlinear Power Amplifiers

Simultaneous wireless information and power transfer (SWIPT) is a promising technology to achieve wide-area energy transfer by sharing the same radio frequency (RF) signal and infrastructure of legacy wireless communication systems. To enlarge the effective range of energy transfer in practice, it is desirable to have a hybrid signaling SWIPT scheme, which combines a high-power multitone energy signal with a low-power broadband information signal. This paper presents a systematic study on the performance of hybrid signaling SWIPT systems with memoryless nonlinear transmitter power amplifiers (PAs). Using PA efficiency and signal-to-noise-and-distortion ratio (SNDR) as the metrics to measure the efficiency of energy transfer and information transmission, respectively, we derive the tradeoff between these two metrics for two PA classes, two nonlinear PA models, and two SNDR definitions. Our results reveal insights into the fundamental performance tradeoff inherent in SWIPT systems using hybrid signaling schemes.

A comprehensive design analysis of a cost-effective WPT system with a class-E power amplifier and a T-matching network

Magnetically-coupled resonant wireless power transfer systems (WPTs) operating in the megahertz range is well-suited for mid-range transmission of moderate power levels. The class-E power amplifier (PA) is attractive for the MHz WPT applications due to the high-efficiency and soft-switching properties. However, since the output power and the efficiency of the class-E PA strongly depends on the output load, any change in the mutual inductance of coupling coils, which leads to the PA load variation, results in a dramatic loss in the overall performance of WPT system. This paper provides a comprehensive design analysis to analytically and numerically mimic the PA behavior to conveniently adapt any variation of the input impedance of the coupled coils to the PA optimum load using a T-type matching network. An equivalent circuit analysis followed by the design theory for the class-E PA, coupled coils, and the T-network has been presented. For validation purposes, the class-E PA implemented by the cost-effective IRF640 MOSFET was first fabricated and its performance was measured for different load values. The PA efficiency and output power was measured as high as 96.7% and 25.8 W, respectively, for the optimum load value of 9 Ω, which was closely predicted from the theory. A 1 MHz WPT system was then built for the operating range up to 27 cm, showcasing its behavior in presence and absence of the proposed T-type matching circuits at two arbitrary 10 cm and 25 cm distances between the coupling coils; the input impedance of the WPT system for those separation distances were 4 Ω and 0.2 Ω, respectively. Results demonstrate power transfer efficiencies of 88% and 15% at distances of 10 cm and 25 cm with the T-network, respectively, improved by 33% and 12% to the non-matching state, respectively. The overall DC output power achieved using a full-bridge rectifier are 21.9 W and 6.8 W at 10 cm and 25 cm, respectively.

Design of the Class-E Power Amplifier with Finite DC Feed Inductance under Maximum-Rating Constraints

This paper proposes an analytical expression set to determine the maximum values of currents and voltages in the Class-E Power Amplifier (PA) with Finite DC-Feed Inductance (FDI) under the following assumptions—ideal components (e.g., inductors and capacitors with infinite quality factor), a switch with zero rise and fall commutation times, zero on-resistance, and infinite off-resistance, and an infinite loaded quality factor of the output resonant circuit. The developed expressions are the average supply current, the RMS (Root Mean Square) current through the DC-feed inductance, the peak voltage and current in the switch, the RMS current through the switch, the peak voltages of the output resonant circuit, and the peak voltage and current in the PA load. These equations were obtained from the circuit analysis of this ideal amplifier and curve-fitting tools. Furthermore, the proposed expressions are a useful tool to estimate the maximum ratings of the amplifier components. The accuracy of the expressions was analyzed by the circuit simulation of twelve ideal amplifiers, which were designed to meet a wide spectrum of application scenarios. The resulting Mean Absolute Percentage Error (MAPE) of the maximum-rating constraints estimation was 2.64%.

Analysis and design procedure of a mm-Wave Class-E power amplifier

This paper presents a Class-E Power Amplifier (PA) design procedure for operation at mm-Wave frequencies, which accounts for the loss of passive components, ON-resistance (Ron) of the transistor, and its breakdown voltage (VBr). The quality factor of inductors is modeled with equivalent resistors and integrated into time-domain equations for the first time. The proposed procedure is examined for the design of a 24 ​GHz Class-E PA in 130 ​nm CMOS technology and compared with former best-known design recipes in the same technology node. Besides, a simplified design technique is introduced based on Ron-Cout (Cout is the transistor output capacitance) curves of the transistor versus its width, obtained by Harmonic Balance (HB) simulation. By the proposed method, the Figure of Merit (FoM) of the designed PA, including a combination of the output power, efficiency, and maximum drain voltage, is improved significantly (52%) compared to the other procedure outcomes in the literature.

Design of the Class-E Power Amplifier Considering the Temperature Effect of the Transistor On-Resistance for Sensor Applications

This brief presents the analysis and compensation technique for the class-E power amplifier (PA) considering the temperature effect of the non-zero transistor on-resistance for sensor network applications. It is shown theoretically and by simulation that the output power level and efficiency decrease with the increase of the transistor on-resistance. The transistor biasing condition for achieving near-zero temperature dependence is derived. With this, a dynamic biasing technique is proposed to stabilize the output power of the PA over a wide temperature range. A prototype class-E PA was designed and fabricated in a 0.18- $\mu \text{m}$ CMOS process. Operating at 477 MHz, the PA has 4 output stages and the measured maximum output variation is about ±0.3 dB from −40 °C to 85 °C. This measurement has a good agreement with the theoretical analysis and simulation.

High-performance class-E power amplifier integrated with a microstrip bandpass-filter for wireless applications

In this paper, a class-E power amplifier using a harmonic control network consisting of a bandpass filter and a harmonic control circuit is presented. The advantage of using the bandpass filter in the harmonic control network is the elimination of the DC-block capacitor between the transistor and the load. As a result, losses due to this capacitor are eliminated at operating frequencies. In this design, a new narrow bandpass filter is used with a practical central frequency of 2.4 GHz. The filter carries the maximum power to the load due to its low insertion loss. On the other hand, the harmonic control circuit comprises a tunable elliptic resonator, which resonated in the third harmonic and a quadratic wavelength line, which controls the even harmonics. The input impedance of the harmonic controller circuit is also controlled by a microstrip transmission line that minimizes the parasitic effects of the transistor output. This design is fabricated and measured on the RO4001 board. The maximum measured power output of this narrow-band amplifier is 24 dBm, with 72% power added efficiency.

A Study and Analysis of High Efficiency CMOS Power Amplifier for IoT Applications

This paper presents a study and analysis of high efficiency CMOS power amplifier (PA) for Internet of Thing (IoT) application. The studied mainly focused on the topology employed in designing high efficiency PA in gigahertz range frequencies. This study covers the basic class-E PA and the topologies in designing class-E PA such as single-stage, two-stage, multistage and differential. The circuits structure and the performances of class-E PA is discussed. The analysis is focusing on the efficiency of the proposed PA. The latest CMOS PAs developments have been studied and a summarization of the performance specification for different topologies are elaborated.

An Optimal Design of High Output Power CMOS Class E Power Amplifier with Broadband Matching for RFID Applications

In the radio frequency frontend the power amplifiers are most essential block for reliable wireless communication. Power amplifiers are used for amplification and enhance the input signal to the desired power level at output. The class-E power amplifiers are used in many RF portable electronic devices that need low power consumption, high gain, and high efficiency. In this article, we present an optimum design of a complementary metal-oxide semiconductor (CMOS) class-E power amplifier (PA) that achieves high efficiency and high gain simultaneously for RF based electronic article surveillance (EAS) system. The simulated analysis and implementation of a class-E RF power amplifier with an appropriate output impedance matching network are presented. The proposed CMOS class-E PA has 41.7 dBm output power with 63% of power efficiency at frequency of 7.7 MHz to 8.7MHz.

Mid-Range Wireless Power Transfer System for Various Types of Multiple Receivers Using Power Customized Resonator

This paper presents a high-efficiency wireless power transfer (WPT) system that can charge multiple receivers (Rx's) of various types. For system analysis, the transmitted power and received power levels are derived using the parameters of the resonators based on electro-magnetic (EM) resonance. Using the analysis results, the power customized resonator (PCR) not only for deriving sufficient output power from the transmitter (Tx) but also for appropriately distributing the received power to the various and multiple Rx's is proposed. In addition to the PCR, the Tx unit is designed to work as a load-dependent voltage source using a differential Class-E power amplifier (PA) through a wide range of load impedances. Therefore, the Tx can naturally adapt to the required Tx power levels with a high efficiency corresponding to various Rx configurations without additional tunable circuits or adaptive control schemes. The WPT system, including the load-dependent voltage source for the Tx, full-bridge rectifiers for the Rx's, and the proposed PCR, was designed for the 6.78 MHz frequency band. The proposed system is validated for use with multiple mobile devices by conducting experiments with nine charging cases using three types of Rx's. For all cases, high system efficiencies of 70.7-85.5% were maintained over received power levels of 8.6-45.7 W at a charging distance of 30 mm, and each of the three types of Rx's were experimentally verified to receive sufficient power.

Optimization of Bio-Implantable Power Transmission Efficiency Based on Input Impedance

Recently, the inductive coupling link is the most robust method for powering implanted biomedical devices, such as micro-system stimulators, cochlear implants, and retinal implants. This research provides a novel theoretical and mathematical analysis to optimize the inductive coupling link efficiency driven by efficient proposed class-E power amplifiers using high and optimum input impedance. The design of the coupling link is based on two pairs of aligned, single-layer, planar spiral circular coils with a proposed geometric dimension, operating at a resonant frequency of 13.56 MHz. Both transmitter and receiver coils are small in size. Implanted device resistance varies from 200 Ω to 500 Ω with 50 Ω of stepes. When the conventional load resistance of power amplifiers is 50 Ω, the efficiency is 45%; when the optimum resonant load is 41.89 Ω with a coupling coefficient of 0.087, the efficiency increases to 49%. The efficiency optimization is reached by calculating the matching network for the external LC tank of the transmitter coil. The proposed design may be suitable for active implantable devices.

Design Methodology of the Class-E Power Amplifier with Finite Feed Inductance—A Tutorial Approach

The Class-E with finite feed inductance is a high-efficiency power amplifier that generally uses complex, long, and iterative design procedures. In this paper, we detail a design methodology that is based on an analytical model of this amplifier. This methodology explores the power amplifier design by the use of a symbolic mathematical tool, which was developed in the software Maple™. This approach helps to understand the Class-E circuit topology and it offers a fast and easy design procedure without having to examine, in-depth, the model analytical equations.