Hansik Oh’s research while affiliated with Samsung Medison Co., Ltd. and other places

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Publications (40)


Simplified All-in-One Load Network of the Broadband Doherty Power Amplifier
  • Article

January 2024

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28 Reads

IEEE Transactions on Microwave Theory and Techniques

Yifei Chen

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Jaekyung Shin

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[...]

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Youngoo Yang

A simplified all-in-one load network of Doherty power amplifier (DPA) was proposed for extended back-off range and broadband operation in this study. Although the proposed load network was simplified to just have a postmatching network (PMN) and compact L -section matching networks for both carriers and peaking amplifiers, it could fully incorporate previously known back-off range extending methods, such as asymmetric structure, virtual stub (VS), out-phased current combining (OCC) method, and complex combining load (CCL). Accurate closed-form expressions for the elements and impedances of the load network based on the back-off range extending methods were derived and used to design the structure of the load network. Among available configurations of synthesized load networks, a structure suited for broadband operation was derived. To verify the proposed load network and its closed-form expression, an asymmetric DPA based on GaN-HEMT with an extended back-off range of 8 dB was designed and implemented for a frequency band of 2.9–4.0 GHz, which includes the N78 5G frequency band. Lumped inductors for the initial configuration were transformed using transmission lines for a quasi-lumped structure which was optimized to have a frequency response similar to the original inductor. Implemented DPA exhibited a drain efficiency (DE) of 50%–56% under an output power back-off (OBO) of 8.0 dB from a saturated output power of about 43 dBm, while it showed a DE of 62%–76% over a frequency range of 2.9–4.0 GHz using a continuous-wave (CW) signal. An efficiency of as high as 50.6%–58.0% and an adjacent channel leakage power ratio (ACLR) of under - 46.0 dBc after a digital predistortion (DPD) based on a memory polynomial were achieved at an average output power of 35 dBm using a 5G new radio (NR) signal with a signal bandwidth of 100 MHz and a peak-to-average power ratio (PAPR) of 7.8 dB.


60 W Class-E/F 3 Switching Power Amplifier With an Improved Second Harmonic Distortion of −49 dBc
  • Article
  • Full-text available

January 2024

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46 Reads

IEEE Access

This paper presents a Class-E/F 3 switching power amplifier (SPA) with reduced second harmonic leakage using parallel resonant circuit in series for the second harmonics. The proposed Class-E/F 3 SPA has a structure utilizing a series resonant circuit in shunt for the third harmonic, designed to function as a shunt capacitor for the fundamental, and an additional parallel resonant circuit for the second harmonic, designed to operate as a series inductor for the fundamental. Using the proposed scheme, a Class-E/F 3 SPA was designed and implemented for 6.78 MHz, and was evaluated with various supply voltages. It exhibited output power levels ranging from 10.26 to 59.98 W (40.11 to 47.78 dBm) with supply voltages ranging from 10 to 24 V. The efficiency was maintained at over 89.25%. Additionally, it demonstrated very low second and third harmonic distortion levels, each not exceeding -49.98 dBc, while the total harmonic distortion (THD) ranged from 1.54% to 2.15%.

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FIGURE 3. Schematic of the active bias circuits for the carrier and peaking amplifiers.
FIGURE 7. Simulated load impedance of the drive amplifier (Z drv ) for the 2.8-3.8 GHz band on PAE and output power contours.
FIGURE 9. T equivalent circuit model of the output transformer including Cs and Cp.
FIGURE 12. Layouts of the LMN using a 6-layer laminate: (a) overall 3D view, (b) top view of the three metal layers of M1, M2, and M3.
FIGURE 13. Vertical structure of the 6-layer laminate with the InGaP/GaAs HBT IC.
Broadband InGaP/GaAs HBT Doherty Power Amplifier IC Using Direct Interstage Power Division for Compact 5G NR Handset Module

January 2023

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135 Reads

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4 Citations

IEEE Access

This paper presents a 2.8-3.8 GHz broadband 2-stage fully differential Doherty power amplifier using direct interstage power division based on a 2-μmInGaP/GaAs HBT process for 5G new radio handset applications. A compact transformer-less interstage network is proposed for direct power division for carrier and peaking amplifiers. The power division ratio at the interstage is designed to dynamically vary according to the input power level to provide higher power gain and desired load impedance modulation. By utilizing the non-linear input reactance of the peaking amplifier, broadband dynamic power division circuits were designed for an operating frequency band of as broad as 1 GHz. In addition, active bias circuits for the peaking amplifier were optimized to have sufficient gain expansion, so that the overall AM-AM characteristics is as flat as possible. A broadband load modulation network using one transformer and two quarter-wave transmission lines is proposed. For the off-chip output transformer, impedance trajectory for the wide band impedance matching is presented using a T-equivalent circuit of the transformer. The self-inductance ratio of the transformer is optimized to maximize the bandwidth. Using the 5G new radio uplink signal with a signal bandwidth of 100 MHz, the implemented Doherty PA IC exhibited a power gain of 31.9 to 38.4 dB, PAE of 22.0 to 30.6%, and average output power of 26.0 to 27.8 dBm at a given ACLR of -33.0 dBc without pre-distortion.


A Multimode GaN Doherty Power Amplifier MMIC With N-Scalable Amplifiers for Selective Back-Off Power Level

January 2023

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27 Reads

IEEE Transactions on Microwave Theory and Techniques

This article presents a multimode Doherty power amplifier (M-DPA) monolithic microwave integrated circuit (MMIC). The M-DPA comprises of a load network (LN) based on a combination of current-and voltage-combining methods. By arranging the turn-on transitions of four parallel amplifiers based on the input power level, two carrier and two peaking amplifiers (2C2P) mode for 6-dB output power back-off (OBO) or one carrier and three peaking amplifiers (1C3P) mode for 12-dB OBO can be configured. The performances between efficiency and gain can be balanced according to the selected mode. The M-DPA concept was theoretically expanded to a generalized structure based on N (or = 2m2^m ) scalable amplifiers in parallel that were simply modeled as current sources. This generalized M-DPA supports N1N-1 different operation modes with m different OBO levels. For verification, the M-DPA MMIC was implemented using a 0.25- μ\mu m gallium nitride (GAN)-HEMT process for 5G new radio (NR) applications (3.3–3.6-GHz band). Using a 5G NR downlink signal with a signal bandwidth of 100 MHz and a peak-to-average power ratio (PAPR) of 7.86 dB, at a frequency of 3.55 GHz, the drain efficiencies (DEs) of 37.7 and 33.8% and power gains of 8.3 and 6.4 dB were obtained for the 2C2P mode with an average output power of 37.0 dBm and for the 1C3P mode with an average output power of 31.0 dBm, respectively.




Doherty Power Amplifier With Extended High-Efficiency Range Based on the Utilization of Multiple Output Power Back-Off Parameters

April 2022

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34 Reads

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18 Citations

IEEE Transactions on Microwave Theory and Techniques

This article presents a novel method of extending the high-efficiency range of Doherty power amplifiers (DPAs) by utilizing multiple output power back-off (OBO) parameters. The OBO extension techniques of the DPAs, such as complex combining load (CCL), virtual stub (VS), and out-phased current combining (OCC) methods, were defined, and a general expression for these OBO extension techniques was derived. Using the general expression, three OBO extension methods were comparatively and comprehensively analyzed. Based on the analysis, the DPA with an extended OBO can be designed by simultaneously employing multiple back-off techniques with a high degree of freedom. To verify the general expression and its analysis, a DPA design for the frequency band of 3.45–3.75 GHz with GaN HEMTs was conducted using multiple OBO extension techniques of VS and OCC methods for a large OBO of 8.5 dB. Using a long-term evolution (LTE) signal with a signal bandwidth of 20 MHz and a peak-to-average power ratio (PAPR) of 8 dB, the drain efficiency (DE) of 38.9%–56.8% was achieved at the average output power levels of 34.4–36.8 dBm while satisfying ACLR of no larger than −45 dBc with digital predistortion (DPD) linearization. Under excitation of a 5G new radio (NR) signal with a signal bandwidth of 100 MHz and a PAPR of 8 dB, the DE of 38.5%–50.2% was achieved at the average output power levels of 34.6–36.8 dBm with an ACLR of under −24.6 dBc without DPD linearization.


Beamforming Algorithm Based on the Orthogonal Phase Bases With Trigonometric Estimation for Microwave Power Transfer Systems

January 2022

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61 Reads

IEEE Access

Microwave power transfer (MPT) has been widely studied, as sensors or mobile/wearable devices have been used, especially for IoT applications. A beamforming algorithm is essential and important for both the performance and the system complexity of MPT systems. In this paper, a beamforming algorithm that requires only 3 N -2 transmission sequences for the Tx array with N elements to estimate the optimum set of the transmission phases is proposed. The proposed algorithm is simply based on trigonometric calculations, and can be directly applied to an MPT system without element calibration. Calculation of the optimum phase set of the Tx only requires the information of the received power level from the Rx. Since simultaneous phase shifting of the multiple elements is performed during the power transmission sequence, it can have a relatively high Rx SNR, compared to the methods based on phase shifting of only one element at each sequence. In addition, optimum transmission phase sets for multiple Rx’s can be obtained from a beamforming procedure using the proposed algorithm, if the received power levels from the multiple Rx’s are collected. For verification of the proposed algorithm, a 5.2 GHz 8×4 Tx array having an output power of 0.5 W per Tx element was implemented. Beamforming experiment was performed using the proposed algorithm. A received power of 45 mW at 2 m distance was achieved, which is very close to the simulated value.


Citations (28)


... The need to maximize average efficiency, particularly for OBO ranging from 9 to 12 dB [1], calls for the extension of the existing solutions, such as the 6-dB two-way Doherty power amplifier (DPA) [2], or the development of new topologies such as the load-modulated balanced amplifier (LMBA) [3], distributed efficient power amplifier (DEPA) [4], and N -way DPA [5]. Even if a few examples extend toward high frequency [6], [7], [8], the prototypes presented in the literature mainly operate in the sub-6-GHz frequency bands and are based on single-stage demonstrators, achieving gains of the overall amplifier of the order of 10 dB. ...

Reference:

A Two-Way GaN Doherty Amplifier for 5G FR2 With Extended Back-Off Range
A 6-/12-dB Back-off Multi-Mode GaN MMIC Doherty Power Amplifier for 5G Applications
  • Citing Conference Paper
  • June 2023

... Z C_in and Z P_in of Figure 1 represent the input impedances of the carrier and peaking amplifiers, respectively. The input impedance of the peaking amplifier, Z P_in , goes through a large transition while input power increases due to the nonlinear input capacitance, while Z C_in of the carrier amplifier has relatively small variation over the input power [3]. Therefore, the transition of Z P_in can be utilized to provide different power dividing ratios at the DPA low and peak power levels by controlling design parameters of the interstage transformer, phase offset, and the subsidiary impedance matching network. ...

Broadband InGaP/GaAs HBT Doherty Power Amplifier IC Using Direct Interstage Power Division for Compact 5G NR Handset Module

IEEE Access

... In a DPA, the auxiliary amplifier, also referred to as the peak or peaking amplifier, is a critical component that works in conjunction with the main amplifier to achieve high efficiency and linearity [29]. The DPA architecture is designed to optimize power efficiency by combining the strengths of both the main and auxiliary amplifiers [30,31]. The auxiliary amplifier is responsible for handling the peak power levels of the input signal. ...

Two-stage CMOS/GaAs HBT Doherty Power Amplifier Module for 5G Handsets
  • Citing Conference Paper
  • August 2022

... Increasing the peaking periphery for efficiency improvement in itself will not be as successful as at sub-6 GHz frequencies since the performance downgrading of enlarged transistors is more critical at mm-wave. There are also reported works that focus on extending the DPA OBO range, even with symmetric transistors, through matching complex impedances at the DPA power combining node [10,19]. But these methods do not fundamentally solve the issue since DPAs at mm-wave cannot depend on DPD, and the peaking amplifier bias cannot be lowered as desired. ...

Doherty Power Amplifier With Extended High-Efficiency Range Based on the Utilization of Multiple Output Power Back-Off Parameters
  • Citing Article
  • April 2022

IEEE Transactions on Microwave Theory and Techniques

... As the frequency band and bandwidth for the 5G systems are increased, research on broadband and a compact power dividing method for the differential Doherty PA becomes more and more important. In this paper, a broadband Doherty PA IC for 5G NR handsets, which was partially presented in [20], is proposed with a new compact differential two-stage structure. Both carrier and peaking amplifiers for the main stage are configured as differential, while only one differential drive stage is employed. ...

2.8-3.8 GHz Broadband InGaP/GaAs HBT Doherty Power Amplifier IC for 5G New Radio Handset
  • Citing Conference Paper
  • June 2022

... 반면 advanced DPA라 불리는 VS(virtual stub), OCC(outphased current combining) 또는 CCL(complex combining load) 방식의 DPA들은 OMN의 임피던스 매칭에 complex load impedance를 사용하여 큰 load modulation을 얻음으 로써 OBO를 확장하기 때문에 asymmetric DPA의 한계점 을 극복할 수 있다 [4]∼ [6] . 하지만 symmetric 구조를 사용한 advanced DPA들은 Class-C peaking 증폭기의 상대적 출력 저하 때문에 load modulation이 위축되는 현상을 겪기 때 문에 [4]∼ [7] , 최근에는 asymmetric DPA와 advanced DPA를 모두 사용한 연구들이 진행되었다 [8], [9] . ...

Generalized Expression and Design Method of Modified Load Networks for Doherty Power Amplifier With Extended Back-Off Range

IEEE Access

... Increased input RF signal bandwidth, operating frequency and increase in PAPR of the RF input signal has become major design constraints for the ETPA designers [26]. Designers are often faced with the problem of efficiency reduction while operating the ETPA using the above-mentioned conditions. ...

Hybrid ET Supply Modulator IC with an Adaptive Quiescent Current Controller for Its Linear Amplifier
  • Citing Conference Paper
  • June 2021

... Additionally, LA designs are sensitive to process, voltage, and temperature variations that can change the class-AB quiescent current significantly (by more than 300%). Therefore, circuit-level techniques, such as accurate current quiescent control and supply voltage and temperature insensitive quiescent current control, can be used to control the variation of class-AB current and avoid wasting P LA_bias [37], [38]. ...

Dual-Mode Supply Modulator IC With an Adaptive Quiescent Current Controller for Its Linear Amplifier in LTE Mobile Power Amplifier

IEEE Access

... 반도체 기술의 발전으로 DAC(digital to analog converter) 와 ADC(analog to digital converter)의 광대역 고속 디지탈 신호처리 기술이 급격히 향상되고, 아날로그 RF 회로의 집적화로 SDR(software defined radio) 기반의 DPD 기술이 지속적으로 발전하고 있다. 그리고 DPD에 주로 사용되는 DPA(Doherty power amplifier)는 더 높은 OBO(output back-off) 영역에서 고효율 특성을 얻기 위하여 3way 구 조, 비대칭 Peaking amp 구조 그리고 복소부하 결합구조 와 같은 연구들이 지속적으로 이루어졌다 [1], [2] . ...

3.5 GHz High-Efficiency Asymmetric Doherty Power Amplifier Design Using a Complex Combining Load
  • Citing Article
  • August 2021

The Journal of Korean Institute of Electromagnetic Engineering and Science

... Although conventional mechanical beam-scanning reflector antennas have advantages in highgain with high-efficiency, low axial ratio (AR), simple structure, and low cost, they are restricted to their installation locations because of their bulky structures. Therefore, CP phased arrays with low-profile and electronically beam-scanning capability have been actively developed recently [7][8][9][10][11][12]. In CP phased arrays, AR is an important performance metric as well as bandwidth, gain, and side-lobe level. ...

5.8 GHz 4-channel Beamforming Tx IC for Microwave Power Transfer

IEEE Access