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Saturated Power Amplifier Optimized for Efficiency Using Self-Generated Harmonic Current and Voltage
Jungjoon Kim,Jangheon Kim,Junghwan Moon,Jungwhan Son,Ildu Kim,Seunghoon Jee,Bumman Kim IEEE 2011 IEEE transactions on microwave theory and techniqu Vol.59 No.8
<P>A saturated power amplifier (PA) optimized for efficiency is described. As a PA is driven into saturated operation, the current source of the device generates a large third harmonic current, which creates a quasi-rectangular current waveform. The large nonlinear output capacitor of the transistor generates a second harmonic voltage with a very small third harmonic component. The second harmonic voltage is in-phase with the fundamental voltage, making a half-sine wave voltage waveform with voltage peaking. These waveforms are similar to those of a class F<SUP>-1</SUP> . The fundamental load at the intrinsic device is resistive with the output capacitance tuned out, which is identical to the class F<SUP>-1</SUP> case. However, the required harmonic impedances are just larger than the impedance levels of the output capacitance for both the second and third harmonics. Therefore, the circuit topology is similar to that of a class E amplifier, which is very simple. The PA implemented using a GaN HEMT delivers the expected good performance using the simple circuit topology.</P>
Optimization of Envelope Tracking Power Amplifier for Base-Station Applications
Jungjoon Kim,Jungwhan Son,Seunghoon Jee,Seokhyeon Kim,Bumman Kim IEEE 2013 IEEE transactions on microwave theory and techniqu Vol.61 No.4
<P>We have proposed two methods of enhancing efficiency of an envelope tracking power amplifier (ET PA) from an interlock operation. The first is the utilization of sinking current. The sinking current is a critical efficiency reduction factor since it is a wasted power. To reduce the sinking current, the gate bias of the power amplifier (PA) is increased so that the sinking current is delivered to the PA and is utilized for amplification. The other one is the RF input shaping method. The input signal of ET PAs is a modulated RF signal, and the signal does not guarantee fully saturated operation of the PA at all power levels due to <I>g m</I> nonlinearity of a device. To obtain the maximum efficiency for all of the envelope voltage, we have found the optimum RF input conditions and applied it to the input of the PA. To verify the methods, the proposed ET PA is implemented using a Cree CGH40045 GaN HEMT. For a long-term evolution 5-MHz signal with 6.5-dB peak-to-average power ratio, the PA delivers power-added efficiency of 58.76% with 40.14-dBm output power at 889 MHz.</P>
김정준(Jungjoon Kim),김진섭(Jin-Sub Kim),류춘하(Chunha Ryu),김정홍(Jeong-Hong Kim),박길흠(Kil-Houm Park) 한국통신학회 2013 韓國通信學會論文誌 Vol.38 No.8(통신이론)
본 논문에서는 모바일 환경에서 유비쿼터스 건강 관리시스템 구현을 위한 실시간 심전도 신호 전송방안을 제시한다. 심전도 신호 전송은 그 데이터량의 과다함으로 인해 실시간 전송에 제한이 필요하다. 평균 10% 정도의 특이파형을 갖는 부정맥 심전도 신호에서 R파의 왜곡에 따른 특이 파형 검출 알고리즘에 기반한 실시간 심전도 모니터링 방안을 제안함으로써 많은 시간 동안 심전도 신호를 관찰 및 분석해야 하는 의료진에게 비용과 시간 측면에서 상당히 큰 효과를 볼 수 있다. 전위와 첨도의 문턱 값을 점진적으로 조정할 수 있도록 하여 특이 파형 관찰을임의로 모니터링 함으로써 전송 데이터량 축소 효과와 함께 특이 파형 신호 판독의 유의 수준을 임의로 제고할 수 있도록 하기 위한 효과를 갖는다. 부정맥 심전도에서 특이 파형을 검출하는 제안 알고리즘을 모바일 연동 환경의 클라이언트에서 구현하고 실시간 심전도 신호 모니터링이 가능한 유비쿼터스 건강관리시스템에 적용 가능 하도록 하였다. 이는 이동성을 보장하면서 지속적인 실시간 모니터링을 가능토록 한다. In this paper, we present a method of transmitting ECG signals in real-time mobile environment to be possible to implement the ubiquitous healthcare system. Because of the excessive amount of data transmission of ECG signals, it is necessary to propose a limitation to the real-time transmission. We propose a real-time electrocardiographic monitoring system based on the proposal of unusual waveform detection algorithm which detects the R-wave distortions from the arrhythmia ECG signals having unusual waveform of about 10% on average. It is very effective in terms of time and cost for medical staffs to monitor and analyze ECG signals for a long period of time. Monitoring unusual waveform by gradually adjusting the threshold values of potential and kurtosis makes the amount of data transmitted decrease and significance level of waveform to be enhanced. The unusual waveform detection algorithm is implemented with ubiquitous environment inter-working device client. It is applicable to ubiquitous healthcare system capable of real-time monitoring the ECG signal. While ensuring the mobility, it allows for real-time continuous monitoring of ECG signals.
Analysis of a Fully Matched Saturated Doherty Amplifier With Excellent Efficiency
Jangheon Kim,Junghwan Moon,Young Yun Woo,Sungchul Hong,Ildu Kim,Jungjoon Kim,Bumman Kim IEEE 2008 IEEE transactions on microwave theory and techniqu Vol.56 No.2
<P>A saturated Doherty amplifier based on class-F amplifiers is analyzed in terms of its load modulation behavior, efficiency, and linearity. Simulations included the amplitude ratio and phase difference between the fundamental and third harmonic voltages, the current/voltage waveforms, load lines, and the third-order intermodulation amplitudes/phases of the carrier and peaking amplifiers. The saturated doherty power amplifier was implemented using two Eudyna EGN010MK GaN HEMTs with a 10-W peak envelope power. For a 2.14-GHz forward-fink wideband code-division multiple-access signal, the doherty amplifier delivers an excellent efficiency of 52.4% with an acceptable linearity of -28.3 dBc at an average output power of 36 dBm. Moreover, the amplifier can provide the high linearity performance of -50 dBc using the digital feedback predistortion technique.</P>
IEEE 802.16e Mobile WiMAX용 고효율 고출력 하이브리드 포락선 제거 및 복원 전력 송신기
김일두(Ildu Kim),문정환(Junghwan Moon),김장헌(Jangheon Kim),김정준(Jungjoon Kim),김범만(Bumman Kim) 한국전자파학회 2008 한국전자파학회논문지 Vol.19 No.8
본 논문에서는 효율이 특화된 전력 증폭기를 이용하여 IEEE 802.16e Mobile WiMAX용 고출력 하이브리드 포락선 제거 및 복원 전력 송신기에 대해 기술하였다. Nitronex사의 100-W PEP를 갖는 GaN HEMT 소자를 이용하여 중요한 전력 생성 Vds 구간에 대하여 최대 PAE를 가질 수 있도록 전력 증폭기를 설계하였다. 고출력 응용을 위해서 하이브리드 포락선 제거 및 복원 전력 송신기는 전력 증폭기의 bias fluctuation 문제 및 바이어스 변조기의 stability 문제에 의한 regenerative 오실레이션 문제를 반드시 고려하여 설계되어야 한다. 연동 실험을 위하여, 8.5 ㏈의 PAPR을 갖는 포락선 신호에 대해 바이어스 변조기는 30 V의 최대 출력 전압 크기를 가지면서 72 %의 높은 효율을 유지하도록 구현되었다. WiMAX 신호를 목표로 구현된 하이브리드 포락선 제거 및 복원 전력 송신기는 41.25 ㏈m의 출력 전력에서 38.8 %의 높은 PAE 성능을 얻었다. 또한, 디지털 전치 왜곡 기술을 적용함으로써 전력 송신기의 RCE 성능은 -34.5 ㏈를 기록하여 WiMAX 신호의 선형화 지표를 만족시킬 수 있었다. 본 연구는 2.655 ㎓ 주파수 대역에서 처음으로 구현된 WiMAX용 고출력 하이브리드 포락선 제거 및 복원 전력 송신기에 관한 것이다. We have described a high power hybrid envelope elimination and restoration(H-EER) transmitter for IEEE 802.16e Mobile World Interoperability for Microwave Access(WiMAX) using an efficiency optimized power amplifier(PA). The PA has been designed to have maximum PAE at the important power generation Vds region using Nitronex 100-W PEP GaN HEMT. For the high power application, H-EER transmitter should be considered the regenerative oscillation problem due to the PA’s bias fluctuation effect and bias modulator stability issue. Therefore, the bias modulator for H-EER transmitter has been designed to suppress the regenerative oscillation. For the interlock experiment, the bias modulator has been built with the efficiency of 72 % and peak output voltage of 30 V for the envelope signal with a PAPR of 8.5 ㏈. The H-EER transmitter for WiMAX application has been achieved a high PAE characteristic, 38.8 % at an output power of 41.25 ㏈m. By using digital predistortion(DPD) technique, the Relative Constellation Error (RCE) has been satisfied the specification of -34.5 ㏈. This is the first work at 2.655 ㎓ high power H-EER transmitter for WiMAX application.
김정준,김선겸,김영균,장태석,김휘준,김용진,최현주,Kim, Jungjoon,Kim, Sungyeom,Kim, Youngkyun,Jang, Taesuk,Kim, Hwi-jun,Kim, Youngjin,Choi, Hyunjoo 한국분말재료학회 (*구 분말야금학회) 2021 한국분말재료학회지 (KPMI) Vol.28 No.3
Iron-based amorphous powder attracts increasing attention because of its excellent soft magnetic properties and low iron loss at high frequencies. The development of an insulating layer on the surface of the amorphous soft magnetic powder is important for minimizing the eddy current loss and enhancing the energy efficiency of high-frequency devices by further increasing the electrical resistivity of the cores. In this study, a hybrid insulating coating layer is investigated to compensate for the limitations of monolithic organic or inorganic coating layers. Fe<sub>2</sub>O<sub>3</sub> nanoparticles are added to the flexible silicon-based epoxy layer to prevent magnetic dilution; in addition TiO<sub>2</sub> nanoparticles are added to enhance the mechanical durability of the coating layer. In the hybrid coating layer with optimal composition, the decrease in magnetic permeability and saturation magnetization is suppressed.
Oppenheim and Schur Type Inequalities for Khatri-Rao Products of Positive Definite Matrices
Kim, Sejong,Kim, Jungjoon,Lee, Hosoo Department of Mathematics 2017 Kyungpook mathematical journal Vol.57 No.4
For partitioned matrices, the Khatri-Rao product is viewed as a generalized Hadamard product. In this paper we present Oppenheim's and Schur's determinantal inequalities for the Khatri-Rao product of two positive semidefinite matrices.