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Hwiseob Lee,Wonseob Lim,Jongseok Bae,Wooseok Lee,Hyunuk Kang,Kang-Yoon Lee,Keum Cheol Hwang,Youngoo Yang IET 2017 IET microwaves, antennas & propagation Vol.11 No.12
<P>This study presents a broadband four-way power combiner/divider for very high frequency (VHF) to ultra-high frequency (UHF) bands using 0 degrees hybrids and impedance transformers based on transmission lines. The 0 degrees hybrids were used as in-phase power combiners or dividers, and 1 : 4 impedance transformers were adopted to transform the impedance so that all input and output ports had a 50 Omega impedance. Each component was analysed using equivalent circuits. The overall size of the implemented four-way power combiner/divider module was 110 x 163 mm(2). Based on the measured S-parameters, an ultrabroad bandwidth from 8.0 to 600 MHz was achieved with an insertion loss < 1.0 dB, reflection coefficients below -10.0 dB, isolation among the ports less than -15.0 dB, and magnitude and phase imbalances less than +/- 0.1 dB and 0.5 degrees, respectively.</P>
Lee, Hwiseob,Lim, Wonseob,Lee, Wooseok,Kang, Hyunuk,Bae, Jongseok,Park, Cheon-Seok,Hwang, Keum Cheol,Lee, Kang-Yoon,Yang, Youngoo IEEE 2017 IEEE microwave and wireless components letters Vol.27 No.3
<P>This letter presents a compact load network for Doherty power amplifier (DPA) integrated circuits (ICs) using p-type left-handed (LH) and right-handed (RH) transmission lines (TLs) based on lumped components. The quarter-wave impedance transformers based on the LH TLs and a compensation method for the internal shunt capacitance using a shunt inductor were adopted for the impedance matching networks. The p-type LH and RH TLs for the matching networks and a combining network can be further simplified by merging adjacent shunt components. In order to verify the proposed load network, a 2.6-GHz DPA IC was designed and fabricated using a 0.4-mu m gallium nitride high-electron-mobility transistor process for small-cell base stations. The overall size of the chip is 1.7 x 1.8 mm(2) and the chip was mounted on a quad flat no-leads package. For a long term evolution signal with a signal bandwidth of 10 MHz and a peak-to-average power ratio of 6.5 dB, a high drain efficiency of 52.2% was obtained at an average output power of 34.0 dBm.</P>
Optimized Current of the Peaking Amplifier for Two-Stage Doherty Power Amplifier
Lee, Hwiseob,Kwon, Jinhee,Lim, Wonseob,Lee, Wooseok,Kang, Hyunuk,Hwang, Keum Cheol,Lee, Kang-Yoon,Park, Cheon-seok,Yang, Youngoo Professional Technical Group on Microwace Theory a 2017 IEEE Transactions on Microwave Theory and Techniqu Vol. No.
<P>This paper presents a method of improving efficiency for the two-stage Doherty power amplifier (DPA) using the optimized current of the peaking amplifier. The DPA has a two-stage structure for both the carrier and peaking amplifiers. The first stage of the peaking amplifier has an adjusted bias condition for a near Class-B operation, while the first stage of the carrier amplifier has a higher Class-AB operation. The gain expansion of the first stage due to its lower gate bias helps the second stage of the peaking amplifier to be biased for light Class-C operation and to have steeper turn-ON characteristics, which leads higher peak output power and higher back-off efficiency. The two-stage DPA was designed for the 2.655-GHz band. Using a downlink long-term evolution signal with a signal bandwidth of 10 MHz and a peak-to-average power ratio of 6.5 dB, the overall power gain of 25 dB and a peak output power of 54.2 dBm are experimentally obtained. Using an optimized shape of the peaking amplifier's current, a drain efficiency (DE) of 53% and an adjacent channel leakage power ratio of -30 dBc were obtained at an average output power of 47.8 dBm. A DE of 56.8% and an adjacent channel leakage power ratio of -25 dBc were also obtained at an average output power of 49.5 dBm.</P>
Small-Cell 기지국 시스템을 위한 2.6 GHz GaN-HEMT Doherty 전력증폭기 집적회로 설계
이휘섭(Hwiseob Lee),임원섭(Wonseob Lim),강현욱(Hyunuk Kang),이우석(Wooseok Lee),이형준(Hyoungjun Lee),윤정상(Jeongsang Yoon),이동우(Dongwoo Lee),양영구(Youngoo Yang) 한국전자파학회 2016 한국전자파학회논문지 Vol.27 No.2
본 논문에서는 2.6 GHz에서 동작하는 Doherty 전력증폭기 집적회로를 설계 및 제작하여 평균 전력에서의 효율을 개선하였다. Small-cell 기지국 시스템에 적합하도록 전력 밀도가 높은 GaN-HEMT 공정을 사용하여 설계하였으며, 제작된 Doherty 전력증폭기 집적회로를 QFN 패키지 내부에 수용하여 시스템 적용에 용이하도록 하였다. 제작된 GaN-HEMT Doherty 전력증폭기 집적회로는 10 MHz의 대역폭 및 6.5 dB의 PAPR 특성을 갖는 2.6 GHz LTE 신호에 대하여 평균 전력 33.9 dBm에서 15.8 dB의 전력 이득, 43.0%의 효율 및 —30.0 dBc의 ACLR 특성을 나타낸다. This paper presents a 2.6 GHz Doherty power amplifier IC to enhance the back-off efficiency. In order to apply to small-cell base stations, the Doherty power amplifier was fabricated using GaN-HEMT process for high power density. In addition, the implemented Doherty power amplifier was mounted on a QFN package. The implemented GaN-HEMT Doherty power amplifier was measured using LTE downlink signal with 10 MHz bandwidth and 6.5 dB PAPR for verification. A power gain of 15.8 dB, a drain efficiency of 43.0 %, and an ACLR of —30.0 dBc were obtained at an average output power level of 33.9 dBm.
Design of 1:4 Ultrawideband Hybrid Transmission-Line Balun
Hwiseob Lee,Wooseok Lee,Youngoo Yang IEEE 2015 IEEE microwave magazine Vol.16 No.1
<P>This article presents the 1:4 wideband balun based on transmission lines that was awarded the first prize in the Wideband Baluns Student Design Competition. The competition was held during the 2014 IEEE Microwave Theory and Techniques Society (MTT-S) International Microwave Symposium (IMS2014). It was initiated in 2011 and is sponsored by the MTT-17 Technical Coordinating Committee. The winner must implement and measure a wideband balun of his or her own design and achieve the highest possible operational frequency from at least 1 MHz (or below) while meeting the following conditions: ? female subminiature version A (SMA) connectors are used to terminate all ports ? a minimum impedance transformation ratio of two ? a maximum voltage standing wave ratio (VSWR) of 2:1 at all ports ? an insertion loss of less than 1 dB ? a common-mode rejection ratio (CMRR) of more than 25 dB ? imbalance of less than 1 dB and 2.5?.</P>
Symmetric Three-Way Doherty Power Amplifier for High Efficiency and Linearity
Kang, Hyunuk,Lee, Hwiseob,Oh, Hansik,Lee, Wooseok,Park, Cheon Seok,Hwang, Keum Cheol,Lee, Kang Yoon,Yang, Youngoo IEEE 2017 IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS PART 2 E Vol.64 No.8
<P>This brief presents a three-way Doherty power amplifier (DPA) with a symmetric structure in terms of the output power capacities between the carrier and peaking amplifiers for high efficiency and linearity. Based on the analysis for the efficiency peak at the output power back-off, a symmetric structure was adopted to have higher overall efficiency for the modulated signal. Through the optimized bias condition for the two peaking amplifiers, the proposed three-way DPA can be linearized in the wide output power range. To validate the proposed scheme, a three-way DPA was designed and implemented using a 60 W GaN-HEMT for the carrier amplifier and two 30 W GaN-HEMTs for the peaking amplifiers. Using a 2.14 GHz long-term evolution downlink signal with a peak-to-average power ratio of 6.5 dB, the implemented symmetric three-way DPA exhibited a drain efficiency (DE) of 33.7% and an ACLR of -38 dBc at an average output power of 41.4 dBm. Compared to the condition with the same bias for the peaking amplifiers, the DE and average output power were improved by 8.0% and 2.4 dB for the given ACLR of -38 dBc, respectively.</P>
2.6 GHz GaN-HEMT Power Amplifier MMIC for LTE Small-Cell Applications
Lim, Wonseob,Lee, Hwiseob,Kang, Hyunuk,Lee, Wooseok,Lee, Kang-Yoon,Hwang, Keum Cheol,Yang, Youngoo,Park, Cheon-Seok The Institute of Electronics and Information Engin 2016 Journal of semiconductor technology and science Vol.16 No.3
This paper presents a two-stage power amplifier MMIC using a $0.4{\mu}m$ GaN-HEMT process. The two-stage structure provides high gain and compact circuit size using an integrated inter-stage matching network. The size and loss of the inter-stage matching network can be reduced by including bond wires as part of the matching network. The two-stage power amplifier MMIC was fabricated with a chip size of $2.0{\times}1.9mm^2$ and was mounted on a $4{\times}4$ QFN carrier for evaluation. Using a downlink LTE signal with a PAPR of 6.5 dB and a channel bandwidth of 10 MHz for the 2.6 GHz band, the power amplifier MMIC exhibited a gain of 30 dB, a drain efficiency of 32%, and an ACLR of -31.4 dBc at an average output power of 36 dBm. Using two power amplifier MMICs for the carrier and peaking amplifiers, a Doherty power amplifier was designed and implemented. At a 6 dB back-off output power level of 39 dBm, a gain of 24.7 dB and a drain efficiency of 43.5% were achieved.
GaN-HEMT를 이용한 X-대역 이단 전력증폭기 설계
이우석(Wooseok Lee),이휘섭(Hwiseob Lee),박승국(Seungkuk Park),임원섭(Wonseob Lim),한재경(Jaekyoung Han),박광근(Kwanggun Park),양영구(Youngoo Yang) 한국전자파학회 2016 한국전자파학회논문지 Vol.27 No.1
본 논문에서는 GaN-HEMT를 이용하여 X-대역에서 동작하는 이단으로 구성된 전력증폭기를 설계 및 제작하였다. 높은 전력 이득을 얻기 위해 간단한 구조의 중간 단 정합 네트워크를 통해 이단으로 구성하였다. 3D EM 시뮬레이션을 통하여 본드와이어 인덕턴스와 기생 캐패시턴스를 예측하였다. 본드와이어 인덕턴스를 줄임으로써 정합 네트워크의 Q(quality-factor)를 최소화하여 대역 특성을 향상시켰다. 제작된 전력증폭기는 40 V의 동작 전압을 인가하였으며, 8.1~8.5GHz에서 16 dB 이상의 전력 이득, 42.5 dBm 이상의 출력 전력, 35 % 이상의 효율 특성을 나타냈다. This paper presents an X-band two-stage power amplifier using GaN-HEMT. Two-stage structure was adopted to take its high gain and simple inter-stage matching network. Based on a 3D EM simulation, the bond-wire inductance and the parasitic capacitance were predicted. By reducing bond-wire inductance, Q of the matching network is decreased and the bandwidth is improved. The implemented two-stage PA shows a power gain of more than 16 dB, saturated output power of more than 42.5 dBm, and a efficiency of more than 35 % in frequency range of 8.1~8.5 GHz with an operating voltage of 40 V.
2.6 GHz GaN-HEMT Power Amplifier MMIC for LTE Small-Cell Applications
Wonseob Lim,Hwiseob Lee,Hyunuk Kang,Wooseok Lee,Kang-Yoon Lee,Keum Cheol Hwang,Youngoo Yang,Cheon-Seok Park 대한전자공학회 2016 Journal of semiconductor technology and science Vol.16 No.3
This paper presents a two-stage power amplifier MMIC using a 0.4 μm GaN-HEMT process. The two-stage structure provides high gain and compact circuit size using an integrated inter-stage matching network. The size and loss of the inter-stage matching network can be reduced by including bond wires as part of the matching network. The two-stage power amplifier MMIC was fabricated with a chip size of 2.0×1.9 mm² and was mounted on a 4×4 QFN carrier for evaluation. Using a downlink LTE signal with a PAPR of 6.5 dB and a channel bandwidth of 10 MHz for the 2.6 GHz band, the power amplifier MMIC exhibited a gain of 30 dB, a drain efficiency of 32%, and an ACLR of -31.4 dBc at an average output power of 36 dBm. Using two power amplifier MMICs for the carrier and peaking amplifiers, a Doherty power amplifier was designed and implemented. At a 6 dB back-off output power level of 39 dBm, a gain of 24.7 dB and a drain efficiency of 43.5% were achieved.