• 전자공학회논문지B
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• 제28B권5호
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• pp.421-430
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• 1991

This paper investigated the errect of the right-half-plane zero on stability in the buck-boost DC-DC converter which is one type of the switching regulator and the stability region for the variation of the output current is obtained by evaluating the feedback gain. And it is clarified that the damping ratio decreases gradually by increase of the feedback loop gain and the regulation system of the converter becomes unstable, and from the transient response analysis we obtainedthe stability region about this converter. From above result it is known that the stability decreases by the existence of the right-half-plane zero. For the improvement of stability, we carried out one pole compensation in feedback circuit and obtained the avaliable stability region in relation to the gain bandwidth product from the stability and transient response analysis. These results were established experiment.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 ICEIC The International Conference on Electronics Informations and Communications
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• pp.218-220
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• 2004

A new wide-band VCO topology using Miller capacitance is proposed. Contrary to conventional VCO using the Miller capacitance where the variable amplifier gain is negative, the proposed VCO uses both the negative and positive variable amplifier gain to enhance the frequency tuning range significantly. The proposed VCO is simulated using HSPICE. The simulations show that 410MHz and 220MHz frequency tuning range are obtained using the negative .and positive variable amplifier gain, respectively. The tuning range of the proposed VCO is $23\%$ of the center frequency(2.8GHz). The phase noise is -104dBc/Hz at 1MHz offset by simple model. The operating current is only 3.84mA at 2.5V power supply.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 통신소사이어티 추계학술대회논문집
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• pp.391-395
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• 2003

In this work, we have designed Gilbert cell downconversion mixer using 0.25um Anam CMOS process, we also have analyzed Conversion gain and IIP3 using Taylor series in our own unique way. Especially, bulk terminal is used as LO( Local Oscillator) input for reduction of power consumption and supply voltage. Supply voltage used in this design is lower than 1.8V and core current is less than 500uA. The simulation experiments showed that the conversion gain, IIP3, and power consumption were -1 dB, 4.46dBm, and 0.8mW, respectively.

• 한국통신학회논문지
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• 제34권5C호
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• pp.521-526
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• 2009

In this paper, a complex-valued recursive least squares escalator filter algorithm with reduced computational complexity for complex-valued signal processing applications is presented. The local tap weight of RLS-ESC algorithm is updated by incrementing its old value by an amount equal to the local estimation error times the local gain scalar, and for the gain scalar, the local input autocorrelation is calculated at the previous time. By deriving a new gain scalar that can be calculated by using the current local input autocorrelation, reduced computational complexity is accomplished. Compared with the computational complexity of the complex-valued version of RLS-ESC algorithm, the computational complexity of the proposed method can be reduced by 50% without performance degradation. The reduced computational complexity of the proposed algorithm is even less than that of the LMS-ESC. Simulation results for complex channel equalization in 64QAM modulation schemes demonstrate that the proposed algorithm has superior convergence and constellation performance.

• 한국광학회지
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• 제1권2호
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• pp.162-168
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• 1990

내경이 2.1mm인 Pyrex 모세관을 사용하여 길이가 150mm인 도파형 이산화탄소 레이저를 제작하였으며, 공진기내에 임의의 손실을 가할 수 있는 ZnSe 손실판을 설치하여 공진기의 내부손실에 따른 출력변화를 여러 방전조건에 대해 측정하였다. 본 실험에 Rigrod 이론을 적용하여 내부손실에 따른 출력변화를 예측했으며 실험치로부터 포화출력 및 불포화 이득계수를 구할 수 있었다. 방전전류와 혼합기체의 유입률이 증가함에 따라 포화출력은 증가하며, 불포화 이득계수는 감소하는 경향을 볼 수 있었다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.179-184
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• 2008

This paper presents the design of the feed forward controller to improve on the non-interference control performance of a single PWM converter in parallel for high-speed trains. The feed forward controller is designed to minimize the interference generated by converter switching in parallel operation of PWM converters. The gain value of the feed forward controller is calculated by inductance values of the input transformer. However, it is difficult to decide this gain value exactly because inductance values are changed by the operation condition of an input transformer. In this paper, the proposed design of feed forward controller can exactly decide the gain value using the leakage inductances estimated by detecting the variation of input current. the validity of the proposed feed forward controller is proved through the simulation results.

• Current Optics and Photonics
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• 제2권6호
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• pp.563-567
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• 2018

We propose and experimentally demonstrate a simple tunable photonic microwave band-pass filter with high resolution using a reflective semiconductor optical amplifier (RSOA) and an optical time-delay line. The RSOA is used as a gain medium for generating cross-gain modulation (XGM) effect as well as an optical source. The optical source provides narrow spectral width by self-injection locking the RSOA in conjunction with a partial reflection filter with specific center wavelength. Then, when the RSOA is operated in the saturation region and the modulated recursive signal is injected into the RSOA, the recursive signal is inversely copied to the injection locked optical source due to the XGM effect. Also, the tunability of the passband of the proposed microwave filter is shown by controlling an optical time-delay line in a recursive loop.

• Current Optics and Photonics
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• 제3권5호
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• pp.365-373
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• 2019

This paper investigates the performance of a hybrid single input multiple output radio frequency/free-space optics (SIMO-RF/FSO) communication system. Each SIMO-RF link is modeled as an independent and identically distributed (i.i.d.) Rayleigh distribution, while the FSO link follows a generalized $M{\acute{a}}laga$ (M) distribution. Considering the fixed gain amplify-and-forward (AF) relay and misalignment errors, novel expressions for the outage probability (OP), average bit error rate (ABER) and average capacity are derived. Numerical results show that atmospheric turbulence and misalignment errors can seriously impair the system performance, and the hybrid RF/FSO communication system using SIMO-RF links can greatly improve system performance. We also analyze system performance under different types of modulation schemes. Numerical results are verified by Monte Carlo simulations.

• Current Optics and Photonics
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• 제7권1호
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• pp.28-32
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• 2023

Frequency characteristics of gain-saturated erbium-doped fiber amplifier (EDFA) are experimentally evaluated to mitigate the optical signal fluctuation induced by atmospheric turbulence in terrestrial freespace optical communication systems. Here, an acousto-optic modulator (AOM) is used to emulate optical signal fluctuations induced by atmospheric turbulence. The waveform which is generated in proportion to the refractive-index structural parameters is used to drive the AOM at various periodic frequencies. Thus, the dependence of the signal fluctuation suppression on the frequency is evaluated. The experiment is conducted using a periodic frequency sweep of the AOM driving voltage waveform and signal input power variation of the amplifier. It is observed that a low periodic frequency and high input signal power effectively suppress the optical signal fluctuation. This study evaluates the experimental results from the high-pass filter and gain-saturation characteristics of the EDFA.

• 대한전자공학회논문지TC
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• 제42권6호
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• pp.61-66
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• 2005

본 논문에서는 Step recovery diode와 반도체 레이저의 이득 스위칭을 이용하여 UWB(Ultra Wide Band) 통신 시스템의 구성요소 중 하나인 임펄스 발생기를 설계하였다. 구현된 임펄스 발생기는 4부분으로 구성하였으며, 1번째는 SRD를 이용하여 반도체 레이저의 이득스위칭을 위한 1차 임펄스 발생기, 2번째는 출력된 1차 임펄스를 이득 스위칭을 조건에 맞추기 위한 전류조절기, 3번째는 1차 임펄스 발생기에서 출력된 임펄스를 반도체 레이저의 이득 스위칭을 이용하여 가우시안 펄스를 발생하는 2차 임펄스 발생기, 4번째는 구현된 가우시안 펄스를 UWB를 위한 가우시안 모노펄스로 변환하는 펄스 변환부로 구성되어 있다. 측정된 가우시안 모노펄스는 시간상에서 360 psec의 펄스폭과 -70 mV에서 +50 mV의 크기를 가지며, 주파수상에서 -41 dBm의 크기와 3.6 GHz의 대역폭을 가짐으로써 UWB를 위한 임펄스에 적합함을 확인하였다.