• ETRI Journal
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• v.30 no.1
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• pp.158-160
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• 2008

A highly linear and efficient GaN HEMT Doherty amplifier for wideband code division multiple access (WCDMA) repeaters is presented. For better performance, the adaptive gate bias control of the peaking amplifier using the power tracking circuit and the shunt capacitors is employed. The measured one-carrier WCDMA results show an adjacent channel leakage ratio of -43.2 dBc at ${\pm}2.5$-MHz offset with a power added efficiency of 40.1% at an average output power of 37 dBm, which is a 7.5 dB back-off power from the saturated output power.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.1
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• pp.107-111
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• 2009

In this paper, the power added efficiency(PAE) of a Doherty amplifier has been improved by applying Photonic Bandgap(PBG) characteristics on the output of amplifier. As a result of the high order harmonics termination, excellent improvement in PAE, maximum output power as well as linearity is obtained. The PAE is improved as much as relatively 35% compared with a conventional Doherty amplifier. Moreover, size of LPF is reduced by PBG characteristics. Therefore the whole amplifier circuit size is considerably reduced by diminishing in size of the LPF as compared with a Doherty amplifier using conventional LPFs.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.11
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• pp.834-841
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• 2018

A power amplifier for subgigahertz short-range wireless communication using $0.18-{\mu}m$ CMOS technology is presented. It is designed as a differential structure to form easily a virtual ground node, to increase output power, and to design a cascode structure to prevent breakdown. The transistor gate width was determined to maximize the output power and power-added efficiency(PAE), and the balun was optimized through electromagnetic simulation to minimize the loss caused by the matching network. This power amplifier had a gain of more than 49.5 dB, a saturation power of 26.7 dBm, a peak PAE of 20.7 % in the frequency range of 860 to 960 MHz, and a chip size of $2.14mm^2$.

• Journal of the Semiconductor & Display Technology
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• v.13 no.4
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• pp.43-48
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• 2014

Two-level inverter has some disadvantages like high harmonics contained in the output current, efficiency limit and stress to switching device as IGBT and FET. Many researches have reported multi-level inverter to complement two-level inverter of problems. In this paper, we suggest MPPT algorithm of multi-string three-level solar inverter that considered nowadays. We added midpoint controller in order to implement the MPPT algorithm because the three-level inverter has to need midpoint controller and procured the stability of direct current link. We verify the superiority of multi-string T-Type inverter and the algorithm we suggested with solar irradiance variation experiment and MPPT efficiency measurement. The MPPT efficiency was confirmed with a high efficiency more than 99.97%.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.1
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• pp.1-11
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• 2009

In this paper, a new 1 kW power amplifier with high efficiency and high stability in a RF generator is designed and fabricated for plasma applications. The efficiency of power amplifier is improved by using class-E amplifier that consists of one push-pull MOSFET and high current drive IC instead of class-C amplifier composed of several single ended MOSFET. Switchable damper that allows selecting three different modes of amplifiers for considering efficiency and stability is added into the amplifier for plasma applications. Stable region of an early electronic discharge section is extended to VSWR of 4.5:1 compared to conventional VSWR of 3.8:1 through using switchable damper. The dimension of the amplifier is also reduced to 30 % of conventional amplifier. The 80 % efficiency of power amplifier with switchable damper is obtained the output power of 1 kW in operating frequency of 13.56 MHz. In comparison of conventional power amplifier for plasma applications, 13 % efficiency is improved.

• Journal of electromagnetic engineering and science
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• v.16 no.3
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• pp.143-149
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• 2016

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.

• Journal of Advanced Navigation Technology
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• v.13 no.3
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• pp.358-364
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• 2009

This paper shows some variable bias techniques which can improve the power added efficiency(PAE) for the designed power amplifier. Some simulations have been done to get the effect of the bias change, and variable bias is adopted to get the higher efficiency for dual mode amplifier which generates two different output power levels. With drain bias change and a fixed gate bias, the amplifier shows PAE improvement compared to the fixed bias amplifier. In addition, this paper analyzed nonlinear distortion of the power amplifier and has used the digital predistortion which can result in 10dB ACPR improvement for the dual band amplifier.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.5
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• pp.72-79
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• 2010

In this paper, we describe the design and implementation of a high efficiency Doherty power amplifier using gallium nitride (GaN) high-electron mobility transistor (HEMT). The carrier and peaking amplifiers of the proposed Doherty power amplifier consist of the switching-mode Class-E power amplifiers. The test conditions are a duty of 10% and a pulse width of $100\;{\mu}s$ and pulse repetition frequency (PRF) of 1 kHz for a S-band radar application. A RF performance peak PAE of 64% with drain efficiency of 80.6%, at 6 dB output back-off point from saturated output power of 45.5 dBm, was obtained at 2.85 GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.3
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• pp.276-282
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• 2015

Until recently, power amplifiers using LDMOS were Class-AB and Doherty type, and showed 55 % efficiency for narrowband of 60 MHz bandwidth. However, owing to the RRH application of base stations power amplifier module, a bandwidth expansion of at least 100 MHz and high efficiency power amplifiers of at least 60 % power efficiency are required. In this study, a Class-J power amplifier was designed by optimizing an output matching circuit so that the second harmonic load will contain a pure reactance element only and have broadband characteristics by using GaN HEMT. The measurements showed that a 45 W Class-J power amplifier with a power added efficiency of 60~75 % was achieved when continuous wave signals were input at 1.6~2.3 GHz, including W-CDMA application.

• Proceedings of the KIEE Conference
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• 2008.10c
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• pp.142-144
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• 2008

This paper is studied on the characteristic analyses of a high performance buck-boost converter added electric isolation by using a soft switching method. To be achieved of a high performance system, the proposed buck-boost converter is constructed by using a partial resonant circuit. The control switches using in the converter are operated with soft switching for a Partial resonant method. The controlling switches are operated without increasing their voltage and current stresses by the soft switching technology. The result is that the switching loss is very low and the converter efficiency is high. And the proposed converter is added in a electric isolation. When the power conversion system is required to electric isolation, the proposed converter is adopted with the system development of high efficiency. The soft switching operation and system efficiency of the proposed converter is verified by digital simulation and experimental results.