• Journal of electromagnetic engineering and science
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• 제11권3호
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• pp.227-233
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• 2011

This paper describes the development of a broadband quasi-Yagi antenna using a folded dipole driver. The antenna is designed on a low-permittivity substrate to reduce the surface wave effect, and hence the gain can be enhanced easily by adding directors. The folded dipole driver is connected to a 50-${\Omega}$ microstripline via a simple broadband microstrip-to-coplanar stripline transition with a quarter radial stub. The key motivation for the use of a folded dipole is to increase the input impedance at the driver, allowing a smaller mismatch loss between the antenna driver and the coplanar stripline feed. The proposed antenna has a measured bandwidth of 4.67~6.26 GHz for the -10 dB reflection coefficient, and a flat gain of 4.86~5.15 dB within the bandwidth.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.267-269
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• 2007

PLL(Phase Locked Loop) are widely used circuit technique in modern electronic systems. In this paper, We propose the low voltage and high speed PLL. We design the PFD(Phase Frequency Detector) by using TSPC (True Single Phase Clock) circuit to improve the performance and solve the dead-zone problem. We use CP(Charge Pump} and LP(Loop filter) for Negative feedback and current reusing in order to solve current mismatch and switch mismatch problem. The VCO(Voltage controlled Oscillator) with 5-stage differential ring oscillator is used to exact output frequency. The divider is implemented by using D-type flip flops asynchronous dividing. The frequency divider has a constant division ratio 32. The frequency range of VCO has from 200MHz to 1.1GHz and have 1.7GHz/v of voltage gain. The proposed PLL is designed by using 0.18um CMOS processor with 1.8V supply voltage. Oscillator's input frequency is 25MHz, VCO output frequency is 800MHz and lock time is 5us. It is evaluated by using cadence spectra RF tools.

• Journal of Audiology & Otology
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• 제23권1호
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• pp.33-38
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• 2019

Background and Objectives: Determination of the lesion side based on the direction of the nystagmus could result in confusions to the clinicians due to mismatch between the vestibular function tests and also between vestibular and audiologic features. To minimize these mistakes, we elucidated the clinical manifestation and vestibular function test results in cases with recovery spontaneous nystagmus (rSN). Subjects and Methods: Patients who visited ENT clinic of tertiary referral hospital for acute onset continuous vertigo from January 2008 to December 2011 were enrolled. In these patients, we assessed onset time of vertigo, time point of paralytic spontaneous nystagmus (SN) and time point of rSN. At each time point of SN, vestibular function tests and hearing function tests were performed. Results: We confirmed the rSN among patients with unilateral vestibulopathy and demonstrated that high gain of the rotatory chair test (slow harmonic acceleration) and/or mismatch of the SN direction and contralateral caloric weakness could indicate the recovery state of patients and nystagmus observed in this stage is recovery phase nystagmus. Conclusions: In acute vestibulopathy patients, recovery phase nystagmus was observed and on this stage of disease vestibular function tests shows several features that could predict recovery state.

• 대한청각학회지
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• 제23권1호
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• pp.33-38
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• 2019

Background and Objectives: Determination of the lesion side based on the direction of the nystagmus could result in confusions to the clinicians due to mismatch between the vestibular function tests and also between vestibular and audiologic features. To minimize these mistakes, we elucidated the clinical manifestation and vestibular function test results in cases with recovery spontaneous nystagmus (rSN). Subjects and Methods: Patients who visited ENT clinic of tertiary referral hospital for acute onset continuous vertigo from January 2008 to December 2011 were enrolled. In these patients, we assessed onset time of vertigo, time point of paralytic spontaneous nystagmus (SN) and time point of rSN. At each time point of SN, vestibular function tests and hearing function tests were performed. Results: We confirmed the rSN among patients with unilateral vestibulopathy and demonstrated that high gain of the rotatory chair test (slow harmonic acceleration) and/or mismatch of the SN direction and contralateral caloric weakness could indicate the recovery state of patients and nystagmus observed in this stage is recovery phase nystagmus. Conclusions: In acute vestibulopathy patients, recovery phase nystagmus was observed and on this stage of disease vestibular function tests shows several features that could predict recovery state.

• 대한전자공학회논문지SP
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• 제46권4호
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• pp.148-156
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• 2009

본 논문에서는 I/Q 부정합에 의한 단일 주파수 연속파 학습신호 왜곡을 새롭게 해석하고 이를 이용한 영상 제거 방법을 제안한다. 기존의 방법에서는 위상 부정합과 이득 부정합을 각각 예측하고 보상하는 방법을 사용하였다. 본 논문에서는 I/Q 부정합에 의하여 단일 주파수 연속파 학습신호의 원형 궤도가 타원 궤도로 왜곡됨을 증명한다. 이를 바탕으로 2단계로 이루어진 I/Q 부정합 보상 방법을 제안한다. 제안한 방법의 첫 번째 신호처리에서는 수신 신호의 위상을 회전하여 타원 궤도의 장축이 x축과 일치하도록 한다. 두 번째 신호처리에서는 첫 번째 신호처리를 거친 Q 경로 신호를 증폭하여 원형 궤도가 되도록 하여 I/Q 부정합을 보상하고 영상 신호를 제거한다. 모의실험을 통해서 직교 위상 편이 변조 (QPSK), 16-직교 진폭 변조 (QAM), 64-직교 진폭 변조 신호에 대해서 70dB 이상의 영상 제거 성능을 가지고 있음을 보인다. 한편, 제안한 방법이 우수함을 보이기 위하여 레일레이 페이딩 경로 환경에서 성능 분석을 한다. 비트오율 (BER) 모의실험을 통해서 제안한 방법은 직교 위상편이 변조, 16-직교 진폭 변조, 64-직교 진폭 변조 등의 다양한 변조에 대해서 부가백색가우시안잡음 (AWGN) 뿐 만 아니라 페이딩 경로에서도 영상 신호가 없는 이상적인 수신기의 비트오율과 거의 일치함을 보인다.

• 전자공학회논문지C
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• 제36C권5호
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• pp.48-55
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• 1999

본 논문에서는 CMOS CCD 카메라 인터페이스 응용을 위한 자동 이득 제어(Automatic Gain Control: AGC)회로를 제안한다. 제안하는 자동 이득 제어 회로는 디지털 신호에 의해 직접 제어되므로 기존의 회로와 달리 별도의 D/A 변환기가 필요 없으며, 신호의 정착 특성은 이득 제어 신호의 변화에 거의 독립적이다. 또한 큰 캐패시턴스를 얻기 위해 적용된 캐패시터 조합 기법은 수위치드 캐패시터 기법을 사용한 자동 이득 제어 회로의 대역폭을 크게 향상시킨다. 캐패시터의 구현시 발생하는 부정합 오차 (mismatch error)는 제안하는 레이아웃 기법에 의해 0.1% 이내로 제한된다. 자동 이득 제어 회로의 출력 신호는 동일 칩에 집적된 10비트 A/D 변환기로 전달된다. 제안하는 자동 이득 제어 회로를 실장한 CCD 카메라 인터페이스 전체 시스템 시제품 0.5 um n-well CMOS 공정으로 구현되어 32dB 이득 제어 영역과 1/8dB 이득 제어 단계를 가지며, 3V 전원 전압과 25MHz의 동작 속도에서 총 173mW의 전력을 소모한다.

• 한국항공우주학회지
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• 제39권3호
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• pp.254-260
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• 2011

원격측정링크는 항공기의 움직임에 따라 안테나 이득과 편파가 실시간으로 변화하는 동적 통신링크이다. 본 논문에서는 항공기의 비행궤적, 자세, 3차원 안테나 패턴을 사용하여 실시간 탑재안테나 이득과 송수신 안테나의 편파 부정합을 계산하였다. 그리고 다중경로 환경을 2-Ray 둥근지구 반사지형으로 모델링하고, 항공기에서 송신한 RF 신호를 빔폭이 좁은 안테나로 수신할 때 수신신호세기를 예측하였다. 또한 비행시험을 실시하고 측정값과 예측값을 비교하여 잘 일치함을 확인하였다.

• Journal of Power Electronics
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• 제14권1호
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• pp.125-134
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• 2014

This paper presents a robust and speed-sensorless stator flux estimation for induction motor direct torque control. The proposed observer is based on sliding mode approach. Stator electrical equations are used in the rotor orientation reference frame to eliminate the observer dependence on rotor speed. Lyapunov's concept for systems stability is adopted to confine the observer gain. Furthermore, the sensitivity of the observer to parameter mismatch is recovered with an adaptation technique. The nonlinearities of the pulse width modulation voltage source inverter are estimated and compensated to enhance stability at low speeds. Therefore, a new method based on the model reference adaptive system is proposed. Simulation and experimental results are shown to verify the feasibility and effectiveness of the proposed algorithms.

• JSTS:Journal of Semiconductor Technology and Science
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• 제12권4호
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• pp.411-417
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• 2012

A Coarse-Fine Time-to-Digital Converter (TDC) using the single time amplifier is proposed. A vernier delay line is used to overcome process dependency and the 2-stage time amplifier is designed to have high resolution by increasing the gain of the time amplifier. Single time amplifier architecture reduces the silicon area of the TDC and alleviates mismatch effect between time amplifiers. The proposed TDC is implemented in $0.18{\mu}m$ CMOS process with the supply voltage of 1.8 V. The measured results show that the resolution of the TDC is 0.73 ps with 10-bit digital output, although highend process is not applied. The single time amplifier architecture reduces 13% of chip area compared to previous work. By reducing the supply voltage, the linearity of the TDC is enhanced and the resolution is decreased to 1.45 ps.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.830-835
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• 1993

The errors in machining process by CNC machining center are due to many elements, such as the delay of the servo drivers, friction and the gain mismatch between x-axis and y-axis motors and so on. We made a counter circuit to measure the output of motor encoders for the motion error analysis of a CNC machining center, and have measured the errors experimentally when the CNC performs a circular interpolation. We have also used an iterative learning method to reduce the radius errors and stick motion errors generated by the CNC machining center performing a circular interpolation. The proposed learning scheme worked well and the circle obtained has smaller error.