• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.1 s.104
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• pp.45-51
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• 2006

In this paper, a new predistortion linearizer for controlling the amplitude of low frequency intermodulation distortion signals is proposed. The low frequency intermodulation distortion(IMD) components are generated by harmonic generator. A vector modulator, modulate fundamental signal with low frequency IMD signals, generates predistortion IMD signals and controls amplitude and phase of them with modulation factors. As a result, this predistorter is suppressed IMD signals of power amplifier effectively. The predistortion linearizer has been manufactured to operate in cellular base-station transmitting band($869{\sim}894\;MHz$). The experimental results show that IMD3 of power amplifier are improved more than 20 dB for CW two-tone signals. Also, it's improved the adjacent channel power ratio(ACPR) more than 10 dB for IS-95 CDMA IFA signals.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.10
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• pp.998-1004
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• 2002

This paper reports a design of feedforward linear power amplifier using pilot tone for IMT-2000 band repeaters accepting multi-carrier. As this time pilot tone is applied to the circuit differently from the existing method. Only one pilot tone is used in both 1-st loop(IMD abstraction loop) and 2-nd loop(IMD cancellation loop) to cancell IMD signals automatically according to variation of frequency or power level of input signals. As an experiment, in range of 2110 MHz - 2170 MHz at LPA output power of $20 W_{avg}$, IMD characteristics of over 20 dB was improved maintaining below -60 dBc considering respective 20 MHz. Therefore the supposed feedforward linear power amplifier can be used for linear power amplifier in IMT-2000 band repeaters.

• The Journal of the Acoustical Society of Korea
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• v.17 no.7
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• pp.61-73
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• 1998

라우드스피커의 비선형 음향특성을 해석하기 위하여 라우드스피커 다이아프램의 비 선형특성을 실험적으로 분석하였다. 라우드스피커를 집중질량계로 모델링하고, 출력소음이 없을 때 적용이 가능한 하모닉 발란스법과 출력소음이 있을 때도 적용할 수 있는 통계적 방 법인 라그란지 배수법을 사용하여 비선형 매개변수를 규명하였다. 70Hz 이하의 주파수 영역 에서는 라그란지 배수법이 2차 하모닉 왜곡특성에서 상대적으로 좋은 결과를 보였으며, 3차 하모닉 왜곡특성에서는 하모닉 발란스법이 실험결과와 잘 일치하였다. 전압가진 및 전류 가 진실험을 통하여, 일반화된 주파수 응답함수를 유도하였고 하모닉 왜곡 및 상호변조 특성을 고찰하였다. 고차 주파수 응답특성은 라우드스피커 비선형 매개변수의 변동에 따른 다이아 프램의 비선형특성을 해석하는데 유용한 수단이 될 수 있음도 확인하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.4A
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• pp.502-511
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• 2000

The Gaussian Minimum Shift Keying (GMSK) modulation technique belongs to the class of nonlinear modulation technique, and it is known to be bandwidth efficient. The GMSK modulation is chosen for the digital cellular phone standard by the European Telecommunications Standards Institute (ETSI). In this paper, an efficient method for implementing all digital GMSK modulator is introduced. The proposed modulator is shown to be simple to implement as well as satisfying the required spectral shape recommended by the ETSI.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.138-138
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• 2010

이중 주파수를 이용한 고주파 용량성 결합 플라즈마 장치는 반도체 및 디스플레이 생산 공정에서 널리 사용되는 장치 형태이며 일반적으로 이온 플라즈마 주파수보다 높은 주파수의 고주파 전력과 이온 플라즈마 주파수보다 낮은 주파수의 저주파 전력을 인가하여 플라즈마 발생 밀도 및 입사 이온 에너지를 독립적으로 조절할 수 있다. 용량성 결합 플라즈마 장치에서는 전극의 쉬스 임피던스가 비선형적으로 변화함에 따라 전극의 전압, 전류 및 플라즈마 전위는 수많은 고조파를 포함하게 되며, 이중 주파수가 인가된 경우 이러한 고주파와 저주파 신호의 고조파가 상호 변조된 형태로 나타나게 된다. 본 연구에서는 주파수에 따른 이온의 거동 특성 차이를 이용하여 변조된 형태의 Lieberman의 비균일 RF쉬스 모델을 가정한 고주파 쉬스를 단순한 저주파 쉬스로 모사하였다. 단순화된 저주파 쉬스 임피던스를 이용한 회로 모델을 구성하여 100MHz와 2MHz RF전력을 사용하는 용량성 결합 플라즈마 장치에서 측정된 전극 전압, 전류 및 플라즈마 전위 신호의 위상차 및 고조파 발생 특성을 분석하였다.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.6
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• pp.677-681
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• 2011

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.6 s.109
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• pp.587-596
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• 2006

Recently a new spectrum ruling has been proposed for UWB(Ultra-Wideband) communication applications. The new proposal is expected to reduce the usable UWB spectrum significantly and may cause to weaken the unique advantages of the UWB pulses such as high resolution synchronizations and robustness to the multipath effects. In this paper, we investigate the performance degradation caused by the reduced UWB spectrum. As a means to overcome the performance degradation, a modified discrete linear frequency modulation technique is proposed. We show that, when multipath components are present in the received signal, the proposed method exhibits superior performances in terms of pulse detection efficiency and range resolutions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.4
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• pp.519-529
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• 1993

A spectral and power efficient modulation technique, named Compact Superposed Quadrature Amplitude Modulation (Compact-SQAM), is introduced. The performance of Compact-SQAM system, in a Linearly and nonlinearly amplified single and multicarrier environment, in the presence of additive white Gaussian noise(AWGN), intersymbol interference(ISI), timing jitter and adjacent channel interference (ACI), is experimentally analyzed via computer simulation. Various channel conditions, such as channel spacing, between the main and adjacent channels and fade depth on the desired main channel, are examined. Our result shows that Compact-SQAM, and better P(e) performance that other modems using simple Butteroworth type postdetection receive filters. Especially, Compact-SQAM modem achieves higher efficiency of frequency utilization and better P(e) performance than other modems in the severly bandlimited nonlinear multicarrier channels.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.231-234
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• 2008

The paper proposed the new underwater wireless communication system fitted to non-linear acoustic channel. Generally, in non-linear acoustic channel, one used to do acoustic communication using parametric effect that is some effect caused from acoustic wave having frequency different of two primary acoustic wave frequency. In the paper, Offset PSK communication method fitted to non-linear acoustic channel was proposed, and it was demonstrated through simulations.

• 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.