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Wireless power transfer systems play an important role in the application of modern power supply technology. Wireless charging has been widely used in portable devices such as smartphones, laptops, and even some medical devices. Higher system efficiency can be achieved while reducing costs. This article describes the design of a capacitive power transfer (CPT) system using the Class-E amplifier method. When the capacitance of the coupling plate is small, the operation of Class-E amplifiers under Zero-Voltage-Switching (ZVS) conditions is very sensitive to their circuit parameters. By adding an additional capacitor to the Class-E amplifier, the coupling capacitance can be increased, resulting in better circuit performance. The high efficiency of the Class-E amplifier is verified by simulation and experimental results.

This paper presents a new approach to simplify the design of class-E power amplifier (PA) using hybrid artificial neural-optimization network modeling. The class-E PA is designed for wireless power transfer (WPT) applications to be used in biomedical or internet of things (IoT) devices. Artificial neural network (ANN) models are combined with optimization algorithms to support the design of the class-E PA. In several amplifier circuits, the closed form equations cannot be extracted. Hence, the complicated numerical calculations are needed to find the circuit elements values and then to design the amplifier. Therefore, for the first time, ANN modeling is proposed in this paper to predict the values of the circuit elements without using the complex equations. In comparison with the other similar models, high accuracy has been obtained for the proposed model with mean absolute errors (MAEs) of 0.0110 and 0.0099, for train and test results. Moreover, root mean square errors (RMSEs) of 0.0163 and 0.0124 have been achieved for train and test results for the proposed model. Moreover, the best and the worst-case related errors of 0.001 and 0.168 have been obtained, respectively, for the both design examples at different frequencies, which shows high accuracy of the proposed ANN design method. Finally, a design of class-E PA is presented using the circuit elements values that, first, extracted by the analyses, and second, predicted by ANN. The calculated drain efficiencies for the designed class-E amplifiers have been obtained equal to 95.5% and 91.2% by using analyses data and predicted data by proposed ANN, respectively. The comparison between the real and predicted values shows a good agreement. [ABSTRACT FROM AUTHOR]

In this brief, a new wireless power transfer and data telemetry circuit for biomedical implants is proposed that increases the data-rate without compromising power transmission efficiency. The power and data are transferred through an inductive link driven by a class-E amplifier. In addition to the proposed modulation, this transmitter can be used for a variety of amplitude modulations such as ON-OFF keying and carrier-width modulation. Based on the suspended carrier modulation idea, the data rate to carrier frequency (DRCF) ratio is improved in the proposed transmitter. In comparison with the conventional suspended carrier transmitter, our design is more efficient and less complex. The DRCF ratio in the proposed transmitter is 50 percent. A proof-of-concept prototype of the proposed transmitter has been implemented on printed circuit board. At 1 MHz carrier frequency, the transmitter power efficiency is close to 61% for the power delivered to the load of 32.3 mW and the data rate of 0.5 Mbps. [ABSTRACT FROM AUTHOR]

This paper investigates the design of a Class-E amplifier to be used to drive a CMUT element. An important parameter of amplifier design is the load which determines the overall noise performance, bandwidth of CMUT operation and its transmit efficiency. Airborne CMUTs unlike PZTs have a large capacitive reactance at resonance along with the radiation resistance. We employ a simple LC section between the amplifier output and CMUT input to cancel the capacitive reactance and transform its radiation resistance to any desired amplifier load. Class-E amplifier can then be designed for the given transformed load. In this work we show that higher transformed CMUT loads have lower radiated power with increased 3-dB bandwidth and improved overall noise performance of amplifier and CMUT system. We use lumped equivalent circuit model of CMUT in air to determine the input impedance of CMUT at resonance and then transform its impedance to various design load values. Harmonic balance circuit simulations results show that CMUT 3-dB bandwidth increases from 14 kHz to 44 kHz with fractional loss of amplifier reducing from 6.8 % to 0.14 % when designed with a 500 Ω transformed load instead of 10 Ω . However the radiated power decreases from 4.92 μ W to 0.14 μ W at the same frequency. [ABSTRACT FROM AUTHOR]

Radio frequency (RF) power amplifiers are an integral part of many academic, medical, and industrial applications. For many of these applications, the RF power needs to quickly transition from one level to another. For switched-mode amplifiers, one way to achieve this is with an out-phasing modulation technique. This power control technique, however, presents its own disadvantages, including poor light-load efficiency and an increase in overall system size. In this paper, we present an alternative power modulation method to create a high-efficiency high-speed RF amplifier system. This control technique utilizes two mechanisms, modular on/off and phase-shifting. In modular on/off, a different number of sub-circuits are turned “on” or “off” to crudely adjust the output power. In phase-shifting, the smallest sub-circuit of the whole system is phase-shifted away from the rest of the circuit to fine-tune the output power. This system's performance is first compared with existing out-phasing systems via circuit simulation. Then, an actual circuit implementation with a 13.56-MHz, 1500-W RF amplifier is demonstrated. A 93% dc-to-RF efficiency is achieved at full load, and above 80% efficiency is maintained all the way down to 7% load.

As one of the core components of the RF power system, the RF power source has a fixed frequency and low conversion efficiency, which has become a bottleneck restricting the development of the RF power system. Aiming at this problem, a design scheme for freely switching the RF power source between dual frequency operation modes is proposed. Direct Digital Synthesizer is used as the RF signal source. The MOSFTE producted by IXYS Company of Germany is used to achieve the amplification of small signals, which improves conversion efficiency and the stability of the output frequency. The method of parallel inductors reduces power loss during switching time. Switching the frequency selection network with a digital-controlled switch achieves adaptation of the system at dual frequencies. At the same time, Multisim simulation is carried out on the proposed scheme and theory. After actual testing, the RF power source can achieve dual frequency selection output of 13.56 MHz and 27.12 MHz at 300 W, and the conversion efficiency can reach 90.1%.

In this article, a novel class-E amplifier topology, based on the functioning principle of the stacked converters, is presented. In this amplifier the available output electric power is determined by the addition of the electric power generated by each of the associated devices. Herein, two MOSFETs connected in series are linked, on the one hand, to a dc voltage source and, on the other hand, to a resonant LC circuit and a resistance charge connected in parallel to the capacitor. Both MOSFETs are driven by a gate-to-source square signal allowing a synchronized commutation, promoting a quasi-resonant amplifier behavior similar to that of the classical class-E amplifier; with the characteristic of being able to manage the double of applied dc voltage amplitude and to supply twice electric power to the same load in comparison with the class-E amplifier. This device is able to distribute the same electric power between both MOSFETs, reducing at almost half the magnitude of applied drain-to-source voltage. As a result, voltage stress of each power switch is reduced in comparison with the typical class-E amplifier. Drain efficiency (DE), power added efficiency, and gain of the proposed device were obtained in function of the applied dc voltage. [ABSTRACT FROM AUTHOR]

In this paper, we develop a variable-frequency pulse width modulation (VFPWM) circuit for input control of 6.78-MHz resonant wireless power transfer (WPT) systems. The zero-voltage switching control relies on the adjustments of both duty cycle and switching frequency for the class-E amplifier used in the WPT as the power transmission unit. High-frequency pulse wave modulation integrated circuits exist, but some have insufficiently high frequency or unfavorable resolution for duty cycle tuning. The novelty of this work is the VFPWM circuit design that we put together. A voltage-controlled oscillator (VCO) of radio frequency and capacitor-coupled difference amplifiers are used to simultaneously perform the frequency and duty cycle tuning required in resonant WPT applications. Different circuit topologies of VFPWM are compared analytically and numerically. The most favorable circuit topology, enabling independent control of the frequency and duty cycle, is employed in experiments. The experimental results demonstrate the validity of the novel VFPWM, which is capable of operating at 6.78-MHz and has a duty ratio adjustable from 20% to 45% of the range applicable in the resonant WPT applications.

In this study, we implemented a depletion (D)-mode gallium nitride high electron mobility transistor (GaN HEMT, which has the advantage of having no body diode) in a class-E amplifier. Instead of applying a zero voltage switching control, which requires high frequency sampling at a high voltage (>600 V), we developed an innovative control method called the minimum power input control. The output of this minimum power input control can be presented in simple empirical equations allowing the optimal power transfer efficiency for 6.78 MHz resonant wireless power transfer (WPT). In order to reduce the switching loss, a gate drive design for the D-mode GaN HEMT, which is highly influential for the reliability of the resonant WPT, was also produced and described here for circuit designers.

This paper presents a complete design methodology of a Class-E inverter with a loosely coupled transformer under zero-voltage switching conditions. At a selected maximum coupling coefficient, the inverter satisfies both zero-voltage switching (ZVS) and zero-derivative switching (ZDS) conditions to achieve a high efficiency. As the coupling coefficient is decreased from its maximum value to zero, the inverter satisfies the ZVS condition over a wide range of load resistance. The proposed method absorbs the magnetizing inductance and the leakage inductance into the inverter topology. The closed-form expressions for all the Class-E inverter parameters are derived in terms of the coupling coefficient, including: 1) input impedance of the transformer with a complex load impedance; 2) equivalent phase of the resonant circuit for both nominal and suboptimum operations; and 3) slope of the switch voltage waveform. The relationship between the voltage slope and the coupling coefficient is introduced, which indicates the proximity of the operating point from ZVS and ZDS conditions. A design example of the Class-E inverter is presented to achieve both ZVS and ZDS, at an optimum coupling coefficient of 0.77, and ZVS condition for any coupling coefficient lower than 0.77 and over a wide range of load resistance. Saber simulations and experimental results are given to validate the soft-switching capabilities over a wide range of the coupling coefficient and load resistance. The theoretical results were in good agreement with Saber simulations and experiments. [ABSTRACT FROM AUTHOR]

In this study, we investigated the resonance mechanism of 6.78 MHz resonant wireless power transfer (WPT) systems. The depletion mode of a gallium nitride high-electron-mobility transistor (GaN HEMT) was used to switch the states in a class-E amplifier circuit in this high frequency. The D-mode GaN HEMT without a body diode prevented current leakage from the resonant capacitor when the drain-source voltage became negative. The zero-voltage switching control was derived according to the waveform of the resonant voltage across the D-mode GaN HEMT without the use of body diode conduction. In this study, the effect of the resonant frequency and the duty cycle on the resonance mechanism was derived to achieve the highest WPT efficiency. The result shows that the power transfer efficiency (PTE) is higher than 80% in a range of 40 cm transfer distance, and the power delivered to load (PDL) is measured for different distances. It is also possible to cover different applications related to battery charging and others using the proposed design.

We present a method for optimizing the electronic power system for a new type of photobioreactor or photoreactor in general. In the case of photobioreactors, photosynthetic active microorganisms or cells are grown. A novel concept for the illumination of photobioreactors was necessary, as the external illumination of those reactors leads to a limited penetration depth of light. Due to the limited penetration depth, no standard reactors can be use for cultivation, but custom made reactors with very small volume to surface ratio have to be used. This still prevents the technology from a large scale industrial impact. The solution we propose in this paper is an internal illumination via Wireless Light Emitters. This increases the manageable culture volume of photosynthetic active microorganisms or cells. The illumination system is based on floating light emitters, which are powered wirelessly by near field resonant inductive coupling. The floating light emitters are able to illuminate a photobioreactor more homogeneously than external illumination systems do. We designed a class-E amplifier and field coils to produce an intermediate frequency electromagnetic field inside the reactor. An appropriate magnetic flux density was found to be approx. B = 1 mT and the driving frequency is f = 176 kHz. We conducted experiments with a laboratory size photoreactor. The cultivation volume was 30 L containing up to 3000 WLEs. The maximum electric power input was more than 300 W and we calculated an efficiency of up to 76%.

This paper presents the design of a capacitive power transfer (CPT) system by using the Class-E amplifier approach. The Class-E amplifier approach is chosen to be adopted since it produces high efficiency as close as to 100%, theoretically. Based on the Class-E approach, a design of wireless power transfer system is used to transfer power to a LED lamp. The system has an output around 4.2 watts at a distance of 2 millimeters which transfer enough output power to light a LED lamp. Simulation and experimental results are carried out to verify the high efficiency of the Class-E amplifier. Finally, the design of practical wireless LED lamp is achieved. [ABSTRACT FROM AUTHOR]

For the class-E amplifier in a wireless power transfer (WPT) system, the design parameters are always determined by the nominal model. However, this model neglects the conduction loss and voltage stress of MOSFET and cannot guarantee the highest efficiency in the WPT system for biomedical implants. To solve this problem, this paper proposes a novel circuit model of the subnominal class-E amplifier. On a WPT platform for capsule endoscope, the proposed model was validated to be effective and the relationship between the amplifier’s design parameters and its characteristics was analyzed. At a given duty ratio, the design parameters with the highest efficiency and safe voltage stress are derived and the condition is called ‘optimal subnominal condition.’ The amplifier’s efficiency can reach the highest of 99.3% at the 0.097 duty ratio. Furthermore, at the 0.5 duty ratio, the measured efficiency of the optimal subnominal condition can reach 90.8%, which is 15.2% higher than that of the nominal condition. Then, a WPT experiment with a receiving unit was carried out to validate the feasibility of the optimized amplifier. In general, the design parameters of class-E amplifier in a WPT system for biomedical implants can be determined with the proposed optimization method in this paper. [ABSTRACT FROM PUBLISHER]

Based on the magnetic resonance coupling principle, in this paper a wireless energy transfer system is designed and implemented for the power supply of micro-implantable medical sensors. The entire system is composed of the in vitro part, including the energy transmitting circuit and resonant transmitter coils, and in vivo part, including the micro resonant receiver coils and signal shaping chip which includes the rectifier module and LDO voltage regulator module. Transmitter and receiver coils are wound by Litz wire, and the diameter of the receiver coils is just 1.9 cm. The energy transfer efficiency of the four-coil system is greatly improved compared to the conventional two-coil system. When the distance between the transmitter coils and the receiver coils is 1.5 cm, the transfer efficiency is 85% at the frequency of 742 kHz. The power transfer efficiency can be optimized by adding magnetic enhanced resonators. The receiving voltage signal is converted to a stable output voltage of 3.3 V and a current of 10 mA at the distance of 2 cm. In addition, the output current varies with changes in the distance. The whole implanted part is packaged with PDMS of excellent biocompatibility and the volume of it is about 1 cm3.

This paper presents the design of capacitive wireless power transfer systems based on a Class-E inverter approach. The main reason for adopting the Class-E inverter approach is because of its high efficiency, theoretically 100%. However, the operation of a Class-E inverter is highly sensitive to its circuit’s parameters. In a typical capacitive wireless power transfer application, the capacitive coupling distance between plates is subject to changes, and hence its power transfer efficiency is greatly affected if the Class-E inverter is properly tuned. This drawback motivates us to develop an auto frequency tuning algorithm for a Class-E inverter which maintains its power transfer efficiency in spite of the variations of capacitive coupling distances between plates and circuit’s parameters. Finally, simulation and experiment are carried out to verify the effectiveness of the auto frequency tuning algorithm. [ABSTRACT FROM AUTHOR]

This work presents a method used for designing a broadband class-E power amplifier that combines the two techniques of a nonlinear shunt capacitance and a low quality factor of a series resonator. The nonlinear shunt capacitance theory accurately extracts the value of class-E components. In addition, the quality factor of the series resonator was considered to obtain a wide bandwidth for the power amplifiers. The purpose of using this method was to produce a simple topology and a high efficiency, which are two outstanding features of a class-E power amplifier. The experimental results show that a design was created using from a 130 to 180 MHz frequency with a bandwidth of 32% and a peak measured power added efficiency of 84.8%. This prototype uses an MRF282SR1 MOSFET transistor at a 3-W output power level. Furthermore, a summary of the experimental results compared with other high-efficiency articles is provided to validate the advantages of this method. [ABSTRACT FROM AUTHOR]

A class-E synchronous rectifier has been designed and implemented using 0.13- \mu \text m CMOS technology. A design methodology based on the theory of time-reversal duality has been used where a class-E amplifier circuit is transformed into a class-E rectifier circuit. The methodology is distinctly different from other CMOS RF rectifier designs which use voltage multiplier techniques. Power losses in the rectifier are analyzed including saturation resistance in the switch, inductor losses, and current/voltage overlap losses. The rectifier circuit includes a 50- $\Omega $ single-ended RF input port with on-chip matching. The circuit is self-biased and completely powered from the RF input signal. Experimental results for the rectifier show a peak RF-to-dc conversion efficiency of 30% measured at a frequency of 2.4 GHz. [ABSTRACT FROM PUBLISHER]

ABSTRACT A fully integrated medium power amplifier operating over the entire X-band is demonstrated in a 0.11-μm CMOS technology. A double-resonance technique is used for wideband input matching. At the output load, wideband class-E harmonic matching is performed for up to the third harmonic frequency to achieve high output power and efficiency. The amplifier exhibits measured small-signal gain exceeding 7.6 dB over a wide 3-dB bandwidth from 7.6 to 13.7 GHz. The output power and power added efficiency (PAE) are higher than 10.7 dBm and 15%, respectively, at the entire X-band (8-12 GHz). The peak PAE is 20.2% with an output power of 12.4 dBm at 10 GHz. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:645-649, 2015 [ABSTRACT FROM AUTHOR]

In this paper, a broadband high-efficiency supply modulator is proposed. This modulator, with a node controlled by \Delta \Sigma modulator's output, consists of a conventional Class-E amplifier and a Class-E rectifier. The configurations and operation principles of this modulator are introduced to explain the envelope reconstruction process. The performance of this modulator in steady state is analyzed to show the reason for high-efficiency operations assisted by a shunt diode, especially for short-circuited load resistance. Its performance for broadband envelopes amplification is analyzed using numerical difference equations. The results show that efficiency degradation and nonlinearity of this modulator are inevitable due to transient responses. The most significant factors related to the performance degradation, such as switch loss and conduction loss, are determined and verified by numerical simulations. The simulations for one-carrier wavelength code-division multiple-access (WCDMA) envelopes show that over 80% average efficiency and normalized mean square error (NMSE) of -\16 dB can be obtained in numerical examples even considering the nonidealities. An experimental supply modulator is given to verify the proposed modulator. In this experiment, 48.6% average efficiency and NMSE of -\15.9 dB are measured for WCDMA envelopes of 6.1-dB peak-to-average-power ratio. [ABSTRACT FROM PUBLISHER]

In this article, a high-efficient class-E amplifier design with low voltage and broadband characteristics using a novel Front Coupled Tapered Compact Microstrip Resonant Cell is presented. The proposed micorstrip resonator is used as the harmonic control network in order to suppress higher order harmonics, which obtained the optimized impedance matching for the fundamental and harmonics. The class-E amplifier is realized from 0.7 to 1.8 GHz, and obtained the power added efficiency of 72.5-77.5%. The maximum value of Power added efficiency (PAE) is 79.7% with 11-dBm input power at 1.5 GHz. The designed class-E amplifier using the proposed harmonic control network gained 15.34% increment in PAE, and 25.6% reduction in the circuit size in comparison with the conventional class-E amplifier. The simulation and measurement results show the validity of the proposed design procedure of the broadband class-E amplifier using a novel microstrip resonator cell. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1118-1124, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27490 [ABSTRACT FROM AUTHOR]

Abstract: The design, simulation and implementation of a dedicated Class-E driver for inductive power transfer is presented. Whereas focus is placed on wireless endoscopy, other upper body monitoring applications can be powered simultaneously. The driver is developed to generate a sinusoidal current signal through a coil, for the generation of an alternating magnetic field at 1MHz with a field intensity of about 300μT. The volume within the coil, implemented in a Helmholtz configuration, wherein this magnetic field is guaranteed, allows to cover a volume up to ∼0.2m3. This is an improvement by a factor of 20 compared to previous work and sufficiently large to cover the full upper body of patients. The magnetic field thereby generated, is adequate to provide up to 300mW of power to previously developed capsules, in all possible orientations. Patient safety and solutions to reduce parasitic influences are addressed briefly. [Copyright &y& Elsevier]

Based on the magnetic resonance coupling principle, in this paper a wireless energy transfer system is designed and implemented for the power supply of micro-implantable medical sensors. The entire system is composed of the in vitro part, including the energy transmitting circuit and resonant transmitter coils, and in vivo part, including the micro resonant receiver coils and signal shaping chip which includes the rectifier module and LDO voltage regulator module. Transmitter and receiver coils are wound by Litz wire, and the diameter of the receiver coils is just 1.9 cm. The energy transfer efficiency of the four-coil system is greatly improved compared to the conventional two-coil system. When the distance between the transmitter coils and the receiver coils is 1.5 cm, the transfer efficiency is 85% at the frequency of 742 kHz. The power transfer efficiency can be optimized by adding magnetic enhanced resonators. The receiving voltage signal is converted to a stable output voltage of 3.3 V and a current of 10 mA at the distance of 2 cm. In addition, the output current varies with changes in the distance. The whole implanted part is packaged with PDMS of excellent biocompatibility and the volume of it is about 1 cm3 [ABSTRACT FROM AUTHOR]

This paper presents a novel design procedure for the class-EM amplifier. The numerical design procedure is applied to the design of the class-EM amplifier, which achieves simple and accurate designs for high-order circuits. As a result, no tuning process is necessary in the circuit implementations. In this paper, two types of auxiliary circuits are considered, namely, the zero-voltage switching class-E amplifier and the zero-voltage switching class-E frequency doubler. The class-E auxiliary amplifier has a lower driving power and a higher output power capability than the class-E auxiliary frequency doubler. On the other hand, the class-E auxiliary frequency doubler has lower number of the non-zero-current switchings than the class-E auxiliary amplifier and no on-interval of the antiparallel diode of the MOSFET. The laboratory experimental results agreed quantitatively with the numerical predictions, which validate the effectiveness of the proposed design procedure. [ABSTRACT FROM AUTHOR]

In this article, a new highly efficient and highly stable 1 kW power amplifier is designed and fabricated for plasma processing applications.The efficiency of the generator was improved by using a class-E type power amplifier consisting of one push–pull MOSFET and a high-current driver IC instead of a conventional class-C amplifier composed of several single ended MOSFETs. A switchable damper allows a selection of one of three different amplifier modes; these modes adjust the amplifier's efficiency and stability. The amplifier dimensions were reduced by 30% compared with the conventional class-C power amplifier. Also, a drain efficiency of 80% was produced for a generator output power of 1 kW and operating frequency of 13.56 MHz. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2438–2441, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25512 [ABSTRACT FROM AUTHOR]

The transcutaneous energy transmission system (TETS) composed of a Class-E amplifier may operate at a state away from the optimum power transmission due to the load variation. By introducing the feedback-loop technique, the TETS can keep the optimum state with constant output voltage by adjusting the important design parameters, that is, the duty ratio and frequency of the driving signal and the supply voltage. The relations between these adjusted parameters and the load are investigated. The effectiveness of the feedback technique is validated through a design example with a variable load parameter. The experimental results show that the Class- E amplifier in the feedback loop can keep operating at the optimum state under the condition of up to 50 percent variation of the load value. [ABSTRACT FROM AUTHOR]

In this paper, a single-ended class-E/F2 amplifier with a finite dc feed (FDC) inductor is proposed. In comparison to the other types of class-E amplifiers, a second harmonic parallel resonator at the drain node and an FDC feed inductor are its distinguished characteristics. The optimum operations for theoretical 100% drain efficiency are analyzed and simulated to show the performance improvements of this configuration on power output capability, maximum frequency, and load resistance compared to some previously published results. Design equations and parameters are given in lookup tables using numerical results. An example amplifier is given as a quick design guide, and from the measured results it offers 2.36-W output power, 86.6% drain efficiency, and 19.7-dB gain at 61.44 MHz. [ABSTRACT FROM AUTHOR]

In this article, a linear class AB and nonlinear class E power amplifier for WiMAX application are designed using the concept of equivalent capacitance. This concept provides a straightforward way to design power amplifiers at microwave frequencies without recurring to cumbersome formulas or optimization processes intended to get the output power and efficiencies figures associated to these amplifier classes. Furthermore, the use of optimization algorithms may lead to another class of operation if the intrinsic waveforms are not screened. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008. [ABSTRACT FROM AUTHOR]

This paper presents a design method for a compact high-efficiency quasi-class-E amplifier, using a finite bias feed inductor. It is very difficult to achieve proper class-E operation from high-power transistors operating in the high-frequency region because of their internal parasitic components. To mitigate the effects of internal parasitic components on class-E operation, a finite DC feed inductance is introduced to resonate out the capacitive parasitic components. A quasi-class-E amplifier with a finite DC feed inductor was designed and implemented at 1.2 GHz using a high-power laterally diffused metal-oxide-semiconductor field-effect transistor (LDMOSFET). We compared simulated time domain current and voltage waveforms with ideal ones. As the test results indicated, power-added efficiency as high as 70.4% was achieved, at high output power of 39.55 dBm, without losing the circuits' simplicity, one of the most important advantages of class-E operation. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1114–1118, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22368 [ABSTRACT FROM AUTHOR]

This paper presents the design, fabrication, and measurements of two broadband high-efficiency active integrated antennas (AlAs) operating in linear polarization and circular polarization, respectively. A new design method is proposed for designing the broadband load network of the class-E power amplifier (PA), so that a high power-added efficiency (PAE) can be achieved over a broad bandwidth. A broadband high-efficiency class-E PA is designed based on the proposed method. The linearly polarized (LP) ALA is realized by integrating the broadband class-E PA with a broadband LP antenna, which uses a ring-slot coupled microstrip patch antenna. Then, the circularly polarized (CP) AlA is realized by integrating the broadband class-E PA with a broadband CP antenna, which uses a single-feed cross-slot-coupled microstrip patch antenna. Each antenna is designed for working as both a radiator and a harmonics-terminated load. A low-cost printed-circuit-board technology is employed in fabrication, and a p-high-electron mobility transistor is used. The PAE of the LP AlA is over 50% within a 14.6% bandwidth from 1.78 to 2.06 GHz, while the PAE of the CP AlA is over 50% within a 14% bandwidth from 1.92 to 2.21 GHz. The axial ratio of the CP AlA is below 3 dB over a 9% bandwidth from 1.99 to 2.18 GHz. [ABSTRACT FROM AUTHOR]

Power amplifiers (PAs) often exhibit instabilities leading to frequency division by two or oscillations at incommensurate frequencies. This undesired behavior can be detected through a large-signal stability analysis of the solution. However, other commonly observed phenomena are still difficult to predict and eliminate. In this paper, the anomalous behavior observed in a Class-E PA is analyzed in detail. It involves hysteresis in the power-transfer curve, oscillation, and noisy precursors. The precursors are pronounced bumps in the power spectrum due to noise amplification under a small stability margin. The correction of the amplifier performance has required the development of a new technique for the elimination of the hysteresis. Instead of a trial-and-error procedure, this technique, of general application to circuit design, makes use of bifurcation concepts to suppress the hysteresis phenomenon through a single simulation on harmonic-balance software. Another objective has been the investigation of the circuit characteristics that make the noisy precursors observable in practical circuits and a technique has been derived for their elimination from the amplifier output spectrum. All the different techniques have been experimentally validated. [ABSTRACT FROM AUTHOR]

A fully integrated 2.4 GHz class-E amplifier has been implemented by 0.18 μm CMOS technologies. By using the switching operating mode of a class-E amplifier, the dc power dissipation can be reduced. The amplifier delivers 17.3 dBm output power at 2.4 GHz, with a maximum power-added efficiency (PAE) of 63%, from a 2-V supply voltage. To ensure a stable performance of the device and circuit, the 0.18 μm MOSFET and the class-E amplifier also biased at high voltage stress for 150 h continuous testing. This monolithic amplifier includes the matching and biasing circuit, requiring no external components. [Copyright &y& Elsevier]

In this paper, we develop a variable-frequency pulse width modulation (VFPWM) circuit for input control of 6.78-MHz resonant wireless power transfer (WPT) systems. The zero-voltage switching control relies on the adjustments of both duty cycle and switching frequency for the class-E amplifier used in the WPT as the power transmission unit. High-frequency pulse wave modulation integrated circuits exist, but some have insufficiently high frequency or unfavorable resolution for duty cycle tuning. The novelty of this work is the VFPWM circuit design that we put together. A voltage-controlled oscillator (VCO) of radio frequency and capacitor-coupled difference amplifiers are used to simultaneously perform the frequency and duty cycle tuning required in resonant WPT applications. Different circuit topologies of VFPWM are compared analytically and numerically. The most favorable circuit topology, enabling independent control of the frequency and duty cycle, is employed in experiments. The experimental results demonstrate the validity of the novel VFPWM, which is capable of operating at 6.78-MHz and has a duty ratio adjustable from 20% to 45% of the range applicable in the resonant WPT applications. [ABSTRACT FROM AUTHOR]