• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.6
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• pp.613-622
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• 2013

In this paper, an inductive clamping class-E power amplifier has been tested for wireless power transmission at ISM band, 13.56 MHz. The implemented power amplifier is designed to operate stably without destroying power transistor in wireless power transmission system which basically keeps not to align between a transmitting antenna and a receiving antenna. The power amplifier is also designed to enhance harmonic filtering characteristic. The amplifier was tested with a DC supply voltage of 28 V and input power of 25 dBm at 13.56 MHz. The test results show the output power level of 43 dBm, the difference power level between fundamental frequency and second harmonic frequency of more than 55 dBc, the dc current consumption of 830 mA, and the high power-added efficiency of 85 %. Finally, the implemented power amplifier operated normally with 830 mA DC current consumption from 28 V source when the two antennas were aligned, and the power transmission was successful. But when the two antennas were not aligned, its DC current consumption automatically decreased down to 420 mA to protect the switching transistor.

• Journal of electromagnetic engineering and science
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• v.9 no.1
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• pp.32-37
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• 2009

Various Class-E CMOS power amplifiers for GSM applications are presented. A stage-convertible transformer for a dual mode power amplifier is proposed to increase efficiency in the low-output power region. An integrated passive device(IPD) process is used to reduce combiner losses. A split secondary 1:2 transformer with IPD process is designed to obtain efficient and symmetric power combining. A quasi-four-pair structure of CMOS PA is also proposed to overcome the complexities of power combining.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2704-2707
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• 1999

This paper presents a simple high power audio class amplifier which is controlled by a new current control switching method. Although this class D amplifier has an only one current control loop with the proposed switching method, a good performance can be obtained. And a novel switching strategy for driving stereo signal amplifier circuit with three phase full bridge is discussed also. With the simulation and experimental results, usefulness of the proposed amplifier is confirmed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.9 no.3
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• pp.132-139
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• 1984

This paper presents an exant analysis of the class E tuned power amplifier with a shunt inductor. The following performance parameters are determined for optimum operation with any switch duty ratio: the collector current and voltage waveforms, the peak values of collector current and voltage, the output power, the power output capability, and the values of the load network elements. The analysis shows that the maximum power output capability occurs at a duty ratio of 50 percent. The measured collector efficiency of experiments is 93 percent with 0.93W at 1MHz. This amplifier is especially applicable at portable transmitters because its colletor efficiency is extremely high.

• Progress in Medical Physics
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• v.16 no.3
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• pp.155-159
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• 2005

As a part of implantable device in body, a transcutaneous energy transmission system has been developed. It would be desirable to tansfer electrical energy to implantable devices transcutaneously. The distance between transcutaneous transformer windings are approximately equal to the thickness of the human's skin, nominally between 10$\~$20 mm. Class-E resonant amplifier is used to drive a primary coil for high efficiency. Maximum current is above 50 mA at any frequency. The developed system shows that the circuit operates correctly at each frequency; 500 kHz, 1 MHz and 4 MHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.1
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• pp.61-68
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• 2010

In this work, a reduced size 20W quasi class-E Power Amplifier(PA) with defected ground structure load-network is presented for WCDMA base station application. Harmonic impedances required for the class E operation are satisfied by applying the dumbbell and the asymmetric spiral DGS. Open impedance for 2nd harmonic frequency which has the highest power and nearly short impedances for other higher order harmonics are provided by the proposed DGS load-network. The maximum Power Added Efficiency(PAE) of 70.2 % at the output power of 43.1 dBm with the saturated power gain of 12.7 dB is achieved by the proposed quasi class-E PA, which is comparable to the performance of the reference class-E PA. Total size of the proposed class-E PA is only $50{\times}50\;mm^2$ and much smaller than the conventional class-E PA that is loaded with a number of open stubs.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.220-225
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• 2018

A class E power oscillator is demonstrated for 6.78-MHz wireless power transfer system. The oscillator is designed with a class E power amplifier to use an LC feedback network with a high-Q inductor between the input and the output. Multiple capacitors are used to minimize the variation of the oscillation frequency by capacitance tolerance. The gate and drain bias voltages with opposite characteristics to make the frequency shift of the oscillator are connected in a resistance distribution circuit located at the output of the low drop-out regulator and supplied bias voltages for class E operation. The measured output of the class E power oscillator, realized using the co-simulation, shows 9.2 W transmitted power, 6.98 MHz frequency and 86.5% transmission efficiency at the condition with 20 V $V_{DS}$ and 2.4 V $V_{GS}$.

• Proceedings of the KIPE Conference
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• 2007.11a
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• pp.79-81
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• 2007

본 논문에서는 소나용 고출력 전력증폭기의 효율을 향상시키기 위하여 Class E 설계 기법을 분석하고 소나 시스템의 송신기에 적용하였다. Class E 기법에 기반하여 전력소자를 스위칭 모드로 동작시켜서 Zero Voltage Switching(ZVS)이 발생하도록 회로를 설계함으로써 전력 소자의 전력 손실을 최소화하고 전력 증폭기의 효율을 최대화하여 주었다. 설계된 Class E 기법의 전력 증폭기의 동작 및 타당성을 시뮬레이션을 통하여 검증하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.6
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• pp.435-443
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• 2017

In this study, we analyzed the effects of the common-gate transistor bias of a switching mode CMOS power amplifier. Although the most earier works occured on the transistor sizes of the cascode structure, we showed that the gate bias of the common-gate transistor also influences the overall efficiency of the power amplifier. To investigate the effect of the gate bias, we analyzed the DC power consumption according to the gate bias and hence the efficiency of the power amplifier. From the analyzed results, the optimized gate bias for the maximum efficiency is lower than the supply voltage of the power amplifier. We also found that an excessively low gate bias may degrade the output power and efficiency owing to the effects of the on-resistance of the cascode structure. To verify the analyzed results, we designed a 1.9 GHz switching mode power amplifier using $0.18{\mu}m$ RF CMOS technology. As predicted in the analysis, the maximum efficiency is obtained at 2.5 V, while the supply voltage of power amplifier is 3.3 V. The measured maximum efficiency is 31.5 % with an output power of 29.1 dBm. From the measureed results, we successfully verified the analysis.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.9
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• pp.1087-1093
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• 2012

In this paper, we implemented a HF-band magnetic-field communication system consisting of an amplitude shift keying(ASK) transmitter, a pair of loop antennas, and an ASK receiver. Especially, we suggested a new ASK transmitter architecture, where a drain bias of class E amplifier is switched alternatively between two voltage levels with respect to input data. A maximum 5 W class E amplifier was designed using a low cost IRF510 power MOSFET at the frequency of 6.78 MHz. A measured sensitivity of the designed ASK receiver is -78 dBm, which consists of a log amplifier, a filter, and a comparator. Maximum communication range of magnetic-wave communication system with loop antennas was calculated using magnetic field equations in both near-field and far-field ranges. Also, in order to verify the calculated values, an indoor propagation loss was measured using a pair of loop antennas whose dimensions are $30{\times}30cm$. Maximum operating range is estimated about 35 m in case of transmitter's output power of 1 W and receiver sensitivity of -70 dBm, respectively. Finally, the communication field test using the designed ASK transmitter and receiver was successfully done at the distance of 5 m.