• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.5C
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• pp.522-529
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• 2002

MMIC circuits in whole receiver system was fabricated based on GaAs pHEMT technology. And a V-band downconverter module was fabricated by integrating these circuits. The downconverter module consists of a LO drive power amplifier which generates 24dBm output power, a low noise amplifier(LNA) which shows 20 dB small signal gain, an active parallel feedback oscillator which generates 1.6 dBm output power, and a cascode mixer which shows over 6dB conversion gain. The good conversion gain performance of our mixer made no need to attach any IF amplifier which grows conversion gain. Measured results of the complete downconverter show a conversion gain of over 20 dB between 57.5 GHz and 61.7GHz without IF amplifier.

• Journal of electromagnetic engineering and science
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• v.9 no.4
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• pp.218-222
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• 2009

In this paper, we present a CPW-based 77 GHz 3-stage power amplifier MMIC for automotive radar systems. The power amplifier MMIC has been realized using a 130 nm $In_{0.88}$GaP/$In_{0.4}$AlAs/$In_{0.4}$GaAs metamorphic high-electron mobility transistors(mHEMTs) technology and an output stage with a cascode configuration. This produced a good output power and gain performance at 77 GHz. The fabricated power amplifier MMIC exhibited a small-signal gain of 18 dB, an output power of 17 dBm and 9 % power added efficiency(PAE) at 77 GHz with a total gate width of 800 ${\mu}m$ in the output stage. These performances could be useful to low-cost and small-sized components for 77 GHz automotive radar systems.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.9
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• pp.54-58
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• 2011

In this paper a dual-band Class-E power amplifier using Composite Right-/Left-Handed transmission lines and PIN diode is proposed. Dual-band operation is achieved by the frequency offset and nonlinear phase slope of CRLH TL for the matching network of power amplifiers. The proposed power amplifier has been realized by using in the input and the output matching network for high power added efficiency. PIN diode has been used to obtain the dual-band of power amplifier. The measured results show that output powers of 42.17 dBm and 41.43 dBm were obtained at 800 MHz and 1900 MHz, respectively. At this frequency, we have obtained the power-added efficiency(PAE) of 67.84 % and 65.31 % in two operation frequencies, respectively.

• Journal of IKEEE
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• v.26 no.4
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• pp.722-727
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• 2022

In this paper, we present the design and characterization of a power amplifier (PA) monolithic microwave integrated circuit (MMIC) in the X-band. The device is designed using a 0.25 ㎛ gate length AlGaN/GaN high electron mobility transistor (HEMT) on SiC process. The developed X-band AlGaN/GaN power amplifier MMIC achieves small signal gain of over 21.6 dB and output power more than 46.11 dBm (40.83 W) in the entire band of 9 GHz to 10 GHz. Its power added efficiency (PAE) is 43.09% ~ 44.47% and the chip dimensions are 3.6 mm × 4.3 mm. The generated output power density is 2.69 W/mm². It seems that the developed AlGaN/GaN power amplifier MMIC could be applicable to various X-band radar systems operating X-band.

• Proceedings of the KIPE Conference
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• 1997.07a
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• pp.261-265
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• 1997

Driving the electrodeless fluorescent lamp, the high ac voltage with high frequency is required. The linear power amplifier has been widely used as a driving circuit of electrodeless fluorescent lamp. However, the low efficiency of the power amplifier causes th driving circuit to be replaced by a PWM switching inverter. In order to use a PWM switching inverter as the driving circuit of an electrodeless fluorescent lamp, the high switching frequency is required. But due to the switching loss at switches of the inverter, the limitation of high switching frequency appears in the inverter. One solution to this limitation is to reduce the switching loss by using the zero voltage switching technique. In this paper, zero voltage switching resonant inverter for driving an electrodeless fluorescent lamp is discussed. The results of analysis about the inverter are presented and the equations for design are established. And the validity of the analyzed results are verified through the experiment.

• Proceedings of the Optical Society of Korea Conference
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• 1989.02a
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• pp.49-54
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• 1989

Thin solid film systems polarizing beam splitter and disk amplifier used in the high power laser system ({{{{ lambda }}0=1060nm) are designed by computer aided optimization technique. Extinction ratio of designed polarizing beam splitter for incidence angle 30$^{\circ}$, 45$^{\circ}$, 55.60$^{\circ}$ are 1:93, 1:895, 1:1991. respectively. Maximum reflectance of designed thin film system of disk amplifier is less than 3% for pumping band (500-900nm) and 0.15% for laser beam. Further, SiO film chosen as one of the suitable thin films in the high power laser system is prepared by the sol=-gel process which gives high damage threshold. When the withdrawal speed is 6.15cm/min -16.62 cm/min and the mixing ratio is in the range of 1 mol (ethylsilicate): 4-8mol(ethylalcohol) : 2mol(water), the thickness of deposited film is in the range of 500{{{{ ANGSTROM }}-1500{{{{ ANGSTROM }}.

• ETRI Journal
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• v.29 no.5
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• pp.670-672
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• 2007

An ultra-wideband low-noise amplifier is proposed with operation up to 8.2 GHz. The amplifier is fabricated with a 0.18-${\mu}m$ CMOS process and adopts a two-stage cascode architecture and a simplified Chebyshev filter for high gain, wide band, input-impedance matching, and low noise. The gain of 19.2 dB and minimum noise figure of 3.3 dB are measured over 3.4 to 8.2 GHz while consuming 17.3 mW of power. The Proposed UWB LNA achieves a measured power-gain bandwidth product of 399.4 GHz.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.1
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• pp.231-238
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• 2019

In this paper, we have studied how to improve the amplifiers efficiency by minimizing the combining loss when several unit power amplifiers are combined to obtain high output power. Specifically, we have developed Ka-band Spatial Combining Amplifier. The fabricated Spatial Combining Amplifier is a Ka-band 20W class SSPA, which uses a 5W class unit amplifier module 8EA designed using a GaN bare die. We also combined The unit amplifier module using 8-way spatial divider and combiner with a hybrid radial structure. The output combining loss of the fabricated spatial coupler is about 0.334dB, which is about 92.6% efficiency. In this paper, we developed a Spatial Combining Amplifier with a maximum saturation output of 10W and a power addition efficiency of over 15%. As a result, we achieved the maximum saturation output of 30W and the power addition efficiency of 19%.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.9
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• pp.783-789
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• 2015

This paper presents a Doherty power amplifier(DPA) operating in the 2.6 GHz band for long term evolution(LTE) systems. In order to achieve high efficiency, second and third harmonic impedances are controlled using a compact output matching network. The DPA was implemented using a gallium nitride high electron mobility transistor(GaN-HEMT) that has many advantages, such as high power density and high efficiency. The implemented DPA was measured using an LTE downlink signal with a 10 MHz bandwidth and 6.5 dB PAPR. The implemented DPA exhibited a gain of 13.1 dB, a power-added efficiency(PAE) of 57.6 %, and an ACLR of -25.7 dBc at an average output power of 33.4 dBm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.7A
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• pp.557-567
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• 2005

We evaluate the BER performance of OFDMA system for Wibro services in frequency selective Rayleigh fading channel, considering the carrier frequency offset and the nonlinear high power amplifier. In the uplink OFDMA, nonlinear amplifier and frequency offset introduce larger BER degradation than in the downlink. We explain the reason and obtain the required output back-off of the nonlinear amplifier and value of frequency offset for good BER performance.