Wooseok Lee’s research while affiliated with Sungkyunkwan University and other places

What is this page?


This page lists works of an author who doesn't have a ResearchGate profile or hasn't added the works to their profile yet. It is automatically generated from public (personal) data to further our legitimate goal of comprehensive and accurate scientific recordkeeping. If you are this author and want this page removed, please let us know.

Publications (33)


Optimized Broadband Load Network for Doherty Power Amplifier Based on Bandwidth Balancing
  • Article

December 2020

·

20 Reads

·

5 Citations

IEEE Microwave and Wireless Components Letters

·

Wooseok Lee

·

Sungjae Oh

·

[...]

·

Youngoo Yang

This letter presents an optimized broadband load network for the Doherty power amplifier (DPA) based on bandwidth balancing between low- and peak-power levels. The optimized broadband load network is composed of a quasi-lumped λ\lambda /4 impedance transformer (ITF), a modified multiple resonance circuit (MMRC), and a broadband postmatching network (PMN). The quasi-lumped ITF at the carrier amplifier has an optimized characteristic impedance for bandwidth balancing between low- and peak-power levels. The MMRC provides the quasi-lumped ITF with an appropriate susceptance for optimized bandwidth. It also matches the impedance for the peaking amplifier. To validate this design concept, the broadband DPA was implemented using 30-W gallium–nitride high electron mobility transistor (GaN-HEMT) for both carrier and peaking amplifiers. For the down-link long-term evolution (LTE) signal with a channel bandwidth of 10 MHz and a peak-to-average power ratio (PAPR) of 6.5 dB at the frequency range of 1.15–2.45 GHz, DE ranging from 38.4% to 52.2%, and the adjacent channel leakage power ratio (ACLR) ranging from −23.9 to −35.0 dBc at an average output power of from 39.7 to 41.7 dBm were achieved.


Figure 2. Measured and modeled pulsed-IV (PIV) results.
Figure 8. EM simulation results for the layout versus circuit simulation results for the equivalent circuit of the pad.
Figure 9. Overall equivalent circuit of the 10-finger GaN HEMT.
Figure 10. Simulated PIV for the modeled 10-finger GaN-HEMT.
Figure 11. Simulated and measured gain and PAE of the scaled 10-finger GaN-HEMT at a frequency of 3.5 GHz.

+1

Scaled GaN-HEMT Large-Signal Model Based on EM Simulation
  • Article
  • Full-text available

April 2020

·

419 Reads

·

3 Citations

Electronics

This paper presents a scaled GaN-HEMT large-signal model based on EM simulation. A large-signal model of the 10-finger GaN-HEMT consists of a large-signal model of the two-finger GaN-HEMT and an equivalent circuit of the interconnection circuit. The equivalent circuit of the interconnection circuit was extracted according to the EM simulation results. The large-signal model for the two-finger device is based on the conventional Angelov channel current model. The large-signal model for the 10-finger device was verified through load-pull measurement. The 10-finger GaN-HEMT produced an output power of about 20 W for both simulation and load-pullmeasurements.

Download


6.78 MHz Wireless Power Transmitter Based on a Reconfigurable Class-E Power Amplifier for Multiple Device Charging

November 2019

·

114 Reads

·

28 Citations

IEEE Transactions on Power Electronics

This paper presents a 6.78 MHz wireless power transmitter based on a reconfigurable Class-E power amplifier for various and multiple device charging. To maintain high efficiency for various power receiving devices, an optimized offset transmission line based on lumped components and a susceptance switching circuit are proposed at the load network of the differential Class-E power amplifier. The offset transmission line changes the load impedances of the Class-E power amplifier for the various receivers to the high-power and high-efficiency region. In addition, the susceptance switching circuit further shifts the load impedances of the Class-E power amplifier for some receivers to the high-power and high-efficiency region. To verify the proposed offset line and susceptance switching circuit, a 6.78 MHz wireless power transmitter for A4WP standard was implemented and verified for various receivers. For three different receivers, the transmitter maintains optimal transmission efficiencies for received power levels of 39.7, 16.3, and 8.5 W. A peak system efficiency of 81.4% was achieved when the received power is 31.9 W. The system efficiency maintained well around 74.2 and 70.6% for the received power of 16.3 and 8.5 W, respectively.


Broadband InGaP/GaAs HBT Power Amplifier Integrated Circuit Using Cascode Structure and Optimized Shunt Inductor

September 2019

·

85 Reads

·

24 Citations

IEEE Transactions on Microwave Theory and Techniques

This article presents a broadband two-stage cascode power amplifier integrated circuit (PAIC) using a 2-μm InGaP/GaAs heterojunction bipolar transistor process. Since higher supply voltage of cascode power amplifier (PA) results in lower impedance transformation ratio of the matching network due to lower current, cascode PAs generally have broader bandwidth than common-emitter (CE) PAs. However, bandwidth analysis for handset PAs with a single-section load matching network, including transistors output capacitance, revealed that cascode PAs had bandwidth similar to CE PAs. Through bandwidth analysis based on power and efficiency contours at the internal plane of the transistor, an optimized shunt inductor with a single-section load matching network was proposed in this article to increase the bandwidth of cascode PA. Performances of both cascode and CE PAs with and without the optimized shunt inductor were compared. A broadband two-stage cascode PAIC with a compensating shunt inductor and an L-section matching network was designed and implemented. The implemented PAIC exhibited an output power of at least 30.1 dBm at frequency band ranging from 1.55 to 2.65 GHz for continuous-wave excitation. Using a long-term evolution signal with a peak-to-average power ratio of 7.5 dB and a signal bandwidth of 10 MHz, a power gain of more than 23.7 dB, power-added efficiency of 30.9% to 38.4%, and average output power of 26.7 to 27.7 dBm were obtained at a given adjacent channel leakage power ratio of -30 dBc. A fractional bandwidth was calculated to be 54.3% based on measured results.



FIGURE 1. Source-and load-pull setup with R-C feedback and resistive gate biasing circuits.
FIGURE 2. Simulated MSGs with and without feedback and resistive biasing circuits.
Performance comparison to recently published broadband PAs
6–18 GHz GaAs pHEMT Broadband Power Amplifier Based on Dual-Frequency Selective Impedance Matching Technique

May 2019

·

136 Reads

·

28 Citations

IEEE Access

This paper presents a broadband gallium-arsenide pseudomorphic high-electron-mobilitytransistor (GaAs pHEMT) power amplifier integrated circuit (PAIC) based on a dual-frequency selective impedance matching technique for warfare applications. For a broadband PA design, lower and upper-frequency corners where serious performance degradation is likely to occur should be carefully considered. Feedback and resistive biasing circuits were adopted for driver and main stages to making their frequency responses as flat as possible. Optimum impedances of not only extended lower and upper-frequency corners but also center frequency, were then extracted. Such dual-frequency selective impedance matching technique was applied for extended lower and upper-frequency corners while checking the mismatch level for the center frequency. The proposed broadband PAIC for frequency band from 6 to 18 GHz was designed using a 0.15 μm GaAs enhanced-mode pHEMT (E-pHEMT) process. The implemented broadband PAIC with a simple two-stage structure had a very small chip size of 1.19×0.82 mm 2 . It exhibited a power gain of more than 16.4 dB and output power of 19.2 dBm. Very flat characteristics in power gain and an output power within ±1.0 dB through the whole band were achieved.



Striving for Efficiency: A 475-kHz High-Efficiency Two-Stage Class-E Power Amplifier

January 2019

·

91 Reads

·

3 Citations

IEEE Microwave Magazine

This article presents the design and validation for the high-efficiency class-E power amplifier (PA) that won first place in the high-efficiency PA for 475 kHz Student Design Competition held during the 2018 IEEE Microwave Theory and Techniques Society International Microwave Symposium (IMS 2018) in Philadelphia, Pennsylvania. Participants were required to implement and evaluate their own PAs. The team that achieved the highest drain efficiency while satisfying the conditions of the competition rules was the winner.


GaN-HEMT asymmetric three-way Doherty power amplifier using GPD

November 2018

·

118 Reads

·

6 Citations

IET Microwaves Antennas & Propagation

A gallium-nitride high electron mobility transistor (GaN-HEMT) three-way asymmetric Doherty power amplifier using an unequal three-way Gysel power divider (GPD) is presented in this study. Considering the output power capacity of transistors, the peaking amplifier was designed to have an output power capacity that is 1.5 times larger than that of the carrier amplifier through the use of a parallel combination of two different power amplifiers. A peaking amplifier that is 1.5 times larger can provide a back-off level of 7.5 dB for another peak efficiency. Two different power amplifiers in the peaking amplifier can work as a single power amplifier through an optimization of the input power division ratio (PDR). To split the input power for the carrier and the two peaking amplifiers, an unequal three-way GPD with an optimized PDR was employed. The implemented Doherty power amplifier for the 2.14 GHz band exhibited a drain efficiency (DE) of 59.5% and an adjacent channel leakage ratio (ACLR) of 27.1 dBc at an average output power of 37.2 dBm (7.2 dB for the output power back-off) for the 2.14 GHz downlink long-term evolution signal, which has a peak-to-average power ratio of 6.5 dB and a signal bandwidth of 10 MHz.


Citations (25)


... In order to extend the working bandwidth, some new techniques have been employed to the impedance transformers. As communication standards are currently spreading in different carrier frequencies, research efforts aiming to realize DPAs with ultra-wideband or multiband behaviors are urgently desired [13][14][15][16][17][18][19][20][21][22]. Multi-band DPAs allow the DPAs to optimize the performance in each carrier frequency, as demonstrated by both dualand tri-band, which mainly focus on the optimization of the output combiners and the PAs [23][24][25][26]. ...

Reference:

Asymmetric Doherty Power Amplifier with Input Phase/Power Adjustment and Envelope Tracking
Optimized Broadband Load Network for Doherty Power Amplifier Based on Bandwidth Balancing
  • Citing Article
  • December 2020

IEEE Microwave and Wireless Components Letters

... 기존 도허티 전력증폭기의 낮은 OBO를 확장하기 위해서 Multi-way, Asymmetric 도허티 전력증폭기, OCC(out-phased current combining), CCL(complex combining load), VS(virtual short stub) 도허티 전력증폭기 등 연구가 활발히 진행되고 있 다 [3]∼ [12] . 또한, 낮은 대역폭을 극복하기 위해서 기생 성분 을 상쇄시키거나 보조 전력증폭기에 공진회로를 사용하 는 MRC(multiple resonance circuit) 방법 등이 연구되었다 [13], [14] . OBO는 참고문헌 [11] 및 참고문헌 [12] 이게 된다. ...

Wideband Asymmetric 0.6~1.0 GHz Doherty Power Amplifier with Parallel Resonance Circuit for Peaking Amplifier
  • Citing Article
  • April 2020

The Journal of Korean Institute of Electromagnetic Engineering and Science

... This choice is particularly advantageous for low-power and very-high-frequency WPT applications. The Class-E PA demonstrates its efficacy even in dynamic charging scenarios, such as when there is misalignment between the transmitter and receiver coils [24,25]. ...

6.78 MHz Wireless Power Transmitter Based on a Reconfigurable Class-E Power Amplifier for Multiple Device Charging
  • Citing Article
  • November 2019

IEEE Transactions on Power Electronics

... The advent of high-speed storage, the emergence of the 5G era, and the growing demands of the Internet and artificial intelligence require stable and efficient energy transmission. High-frequency RF transmission (above GHz) has been extensively studied due to its efficiency in transmitting large amounts of data [4,5]. For instance, Zhongyu Liao's team at Southeast University designed a power amplifier with an output power of 34 dBm and a power added efficiency (PAE) of 64% [6]. ...

Broadband InGaP/GaAs HBT Power Amplifier Integrated Circuit Using Cascode Structure and Optimized Shunt Inductor
  • Citing Article
  • September 2019

IEEE Transactions on Microwave Theory and Techniques

... In addition to high efficiency, demand for broad bandwidth has been increasing as wireless communication systems have evolved. In [12] and [13], a PA design method using power and efficiency contours referenced at the internal current source plane of the transistor was introduced. The parasitic components inside the transistor should be extracted and embedded to the load-pull contours, and broadband characteristics of the load network can be more intuitively estimated and optimized using these contours. ...

InGaP/GaAs HBT Broadband Power Amplifier IC with 54.3% Fractional Bandwidth Based on Cascode Structure
  • Citing Conference Paper
  • June 2019

... 크 없이 RF 소자에 각각의 Z opt 를 제공하여 광대역 통신 회로를 구성할 수 있고, 이를 통해 전체 회로 크기 및 손 실을 감소시킬 수 있다. 참고문헌 [7]∼참고문헌 [10]와 같은 완전 집적화된 차동 회로에서는 임피던스 매칭을 포함하는 발룬을 구성하고 있다. 또한, 회로의 출력전력 그림 1. 집중소자-분산 발룬 [5] Fig. 1. ...

High-Efficiency CMOS Power Amplifier using Low-Loss PCB Balun with Second Harmonic Impedance Matching
  • Citing Article
  • February 2019

The Journal of Korean Institute of Electromagnetic Engineering and Science

... contrast, negative feedback and reactive/resistive matching techniques in accordance with the finite gain-bandwidth product are cost-effective, device-level means to address the gain roll-off characteristics of transistors [7][8][9]. Such compensation measures are better suited for active devices with large transconductance because the extended bandwidth is accomplished by weakening the forward gain with resistors aided with reactive elements to regulate the amount of gain attenuation at different frequencies. ...

6–18 GHz GaAs pHEMT Broadband Power Amplifier Based on Dual-Frequency Selective Impedance Matching Technique

IEEE Access

... Since the impedance at the third harmonic at the terminal of the transistor approaches zero, Class-E/F 3 operation can be 4 VOLUME 10, 2022 achieved. As shown in Fig. 2(b), both SPAs satisfy (8) for the fundamental frequency, while the Class-E/F 3 SPA satisfies (7) with high impedance at the second harmonic using the parallel resonant circuit, which significantly suppress the second harmonic leakage current to the load. Fig. 2(c) shows the simulated impedances of the proposed Class-E/F 3 SPA compared to the conventional Class-E SPA. ...

Striving for Efficiency: A 475-kHz High-Efficiency Two-Stage Class-E Power Amplifier
  • Citing Article
  • January 2019

IEEE Microwave Magazine

... To extend the OBO level, several well-known methods based on an asymmetric structure, such as asymmetric DPAs [1]- [3], multi-way DPAs [4]- [6], and multi-stage DPAs [7]- [9], have been proposed. These three methods based on a relatively higher power capacity of the peaking amplifier have obvious disadvantages, such as complicated circuits and reduced power gain. ...

GaN-HEMT asymmetric three-way Doherty power amplifier using GPD
  • Citing Article
  • November 2018

IET Microwaves Antennas & Propagation

... Moreover, two 18-40 GHz RM PAs using one-order and two-order STNs are designed. Although a higher power density can be achieved by using a SiC substrate [14,23,24], the 100 nm commercial GaN-on-Si process is adopted due to the potential low-cost advantage [25][26][27]. The two PAs are proposed and provide ≥30 dBm and ≥31.9 dBm output power, with ≥17% and ≥15% of PAE, in the continuous mode. ...

X-band two-stage Doherty power amplifier based on pre-matched GaN-HEMTs
  • Citing Article
  • February 2018

IET Microwaves Antennas & Propagation