• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.2 s.332
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• pp.87-92
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• 2005

In this paper, adaptive bias circuit and PBG structure have been employed to suppress IMD and improve PAE (Power Added Efficiency) of the power amplifier. It is controlling the gate 'dc' bias voltage with the envelope of the input RF signal. and The PBG structure has been employed on the output port of power amplifier . The proposed power amplifier using adaptive bias circuit and PBG has been improved the IMG by 3 dBc, and the average PAE by $35.54\%$, respectively.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.2 s.314
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• pp.32-38
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• 2007

This paper represents a Doherty amplifier (DPA) with analog predistorter (PD) to improve the linearity of the DPA while preserving the high efficiency. A third-order PD cancels fifth-order intermodulation (IM5) as well as third-order intermodulation (IM3) components by their same phase difference in the PD and DPA. This is accomplished by independently controlling their phase by using the phase-controlled error generator in the PD. Also, we confirm the phase-control ability of the error generator experimentally with a simple and accurate phase measurement setup. For experimental verification, a third-order PD has been implemented and tested in a 180-W DPA at the wide-band code division multiple access (WCDMA) band of 2.11-2.17 GHz. Two-tone test results show that significant cancellation of IM3 and IM5 components can be obtained. For four-carrier WCDMA applications, significant adjacent channel leakage ratio (ACLR) improvement is achieved over a wide range of output power levels. This technique is cost-effective and convenient due to its simple structure, compact size, and three control parameters.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.1
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• pp.14-19
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• 2001

When the high power transistor is used for amplifier in microwave frequency, the bias of transistor is usually AB-class or B-c1ass because of power efficiency. The sweet spot point having small IMD signal compared with near neighborhood exicts frequently in the high power transistor using AB class bias or B-class bias. On the sweet spot, the magnitude and phase of the main and IMD signal of HPA output change as the input signal power change, respective the relative phase on the sweet spot changes rapidly. If we know exactly the magnitude and phase characteristics of IMD signal, we can design a more adequate linearizer and understand the characteristics of transistor. In this paper the magnitude and phase of the main and IMD signal of HPA output on the sweet spot are measured using the designed hardware.

• Journal of the Korean Institute of Intelligent Systems
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• v.27 no.2
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• pp.144-149
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• 2017

In this paper, we developed an intelligent and wideband RF-receiver module to represent a high dynamic range and good linearity characteristics up to 650MHz-2700MHz frequency band. and implemented an intelligent digital-RF- distorted signal measuring system for the RF distortion (intermodulation) signals. Broadband RF-receive module was designed to represent the optimized linear parameters of the receiver to meet the low noise and wide dynamic range. The designed intelligent digital-distortion(intermodulation) signal measument system measured by applying the 1MHz IF of third intermodulation signal of DUT and Measured data was recorded by program on the PC monitor with GUI interface. By variable up to 650MHz-2700MHz measured data showed up to -127.8dBc to -138dBc of the distortion (intermodulation) signal. And developed intelligent digital- distortion signal measurement system can be used to measure intermodulation distortion signal of wireless system widely.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.301-304
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• 1999

밀리미터파 대역의 아날로그 광전송을 위한 진행파형 (travel ing wave, TW) 전계흡수 광변조기 (electroabsorption modulator, EAM)와 광수신기의 설계에 대해 발표하고자 한다. TW EAM 및 TW 광수신기의 일반적인 형태인 ridge-type의 co-planar waveguide (CPW)구조에서의 마이크로파의 전송특성을 3차원 FDTD로 분석하여 광파와 전파의 속도 정합 등을 이루는 최적화 구조를 설계하였다. TW EAM의 경우 광세기 변조의 비선형 응답특성에 있어서 마이크로파 손실과 소자길이가 RF 신호의 혼변조 왜곡 (intermodulation distortion)과 SFDR (spurious free dynamic range)성능에 미치는 영향도 이론적으로 조사하였다. TW PIN 광수신기의 경우 광파와 마이크로파의 속도정합의 영향과 이전에는 고려되지 않았던 photo-generated 전송자의 진성 영역에서의 transit time이 광수신기의 밴드 폭에 미치는 영향을 분석하여 최적화 설계하였다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.8
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• pp.580-587
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• 2003

In this paper, we introduce a novel model to analyze the linearity of a TW-EAM (traveling-wave electroabsorption modulator). The device length, microwave loss (ML), and internal reflection (IR) due to impedance mismatch have effect on the linearity of a TW-EAM. The longer devices have characteristics of lower biases with minimum IMDS (intermodulation distortions). ML decreases the output power as well as the IMD value. Internal reflection has different nonlinear characteristics according to the wavelength of the input frequency and the device length. There is little change in SFDR (spurious-free dynamic range) due to ML or IR. As a result, for a 50 GHz band RF-optical communication system, a 0.8 mm-long TW-EAM with the lowest ML would have better properties by using n, which is caused by impedance, mismatch at the output port.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2003.05a
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• pp.92-96
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• 2003

In this paper, 30 W power Amplifier for IMT-2000 repeater was developed gain flatness and the third IMD (Intermodulation distortion) by Microwave absorber. The absorption ability of the absorber is measured up to -10 ㏈ and -4 ㏈ at 3.6 ㎓, 2.3 ㎓ band respectively. Non using absorber power amplifier has the gain over 57 ㏈, the gain flatness of ${\pm}$0.33 ㏈ and the third IMD of 27 ㏈c at 33.3 W output. Otherwise, using absorber power amplifier has the gain over 58㏈, the gain flatness of less than ${\pm}$0.9, the third IMD over 29 ㏈c at the same output power. As a result, the characteristic of the different type show improvement of 1 ㏈ in gain, 0.3 ㏈ in Gain flatness and 1.77 ㏈c in IMD.

• 한국ITS학회:학술대회논문집
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• 2002.11a
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• pp.138-140
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• 2002

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.6
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• pp.293-297
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• 2005

Linearity is an important property of optical devices for analog communications. In this paper, we study the 3rd-order interrnodulation distortion (IMD3) of an Inp/InGaAsP multiple-quantum-well (MQW) traveling-wave type electroabsorption modulator (TW-EAM). We observe abnormal notches in the IMD3 results those were different from notches by general transfer curve of electroabsorption modulators (EAMs). We analyze the phenomena through absorption coefficients according to wavelengths and bias voltages to verify appearance of the abnormal notchs, where it can be known to result from Stark-shift and broadening. We propose the method to enhance linearity of MQW-EAMs by using these effects.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.6
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• pp.27-27
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• 2002

In this paper, the LPA(Linear Power Amplifier) using new analog feedforward linearizer for IMT-2000 frequency band(2110MHz∼2170MHz) is proposed and fabricated. The designed analog feedforward linearizer system possessing the characteristics of stable operation for input power variation is simple structure and small size. When two-tones in IMT-2000 frequency band are applied to an amplifier, this LPA have the average output power is about 30W and the IMD value is below about 60dBc without correcting the circuit. In camparision with an amplifier without feedforward system at the same output power, the supposed analog feedforward linear amplifier posseses improved the IMD characteristics of over 23dB.