• 전자공학회논문지B
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• 제31B권10호
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• pp.73-81
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• 1994

It is AGC(Automatic Gain Control) amplifier to decide characteristics of IF(Intermediate Frequency) processing IC. When demodulated IF signal by PLL type demodulator, the amplitude of input singla should be maintained at a certain amplitude. The AGC amplifier is an important factor to achieve this condition. The AGC amplifier needs the wide dynamic range, the wide AGC range and better noise characteristics. We designed the AGC amplifier to satisfy these characteristics.

• 센서학회지
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• 제26권4호
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• pp.251-258
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• 2017

According to recent studies by scientists about how to search for food, homes and the mates, it is found that the gradient information plays a key role. From cells to insects and large animals, they mostly either have special sensing organism or use a strategy to measure the gradient. Use of a perturbation as an additional input is introduced for sensor signal processing in order to get the gradient information. Different from typical approach, which calculates the gradient from differentiation, the proposed processing is done by a form of integration, thus it is very robust to noise. Discrete time domain analyses are given for one, two and three input functions for the estimation of the gradients. The amplitude and the frequency of the perturbation are two important parameters for this approach. A quantitative index to measure the effects of the amplitude is developed based on the linear regression analysis. The frequency of the perturbation is to be selected high enough to finish one period of the perturbation before the property is changed significantly with respect to time. Another quantitative index is proposed for guiding the selection of the frequency.

• 한국전자파학회논문지
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• 제27권7호
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• pp.620-624
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• 2016

본 논문은 AM 변조 신호를 전송하기 위한 전류모드논리 주파수 분할기를 설계하고, 모의실험 결과를 통해 입출력 파형과 bias 포인트의 변화에 따른 출력 전압을 분석하였다. 또한, 입력 주파수 1,400 MHz에서 최적화되어 동작하는 주파수 분할기를 설계하였으며, 이를 통해 700 MHz 변조 신호의 전송 가능성을 확인하였다. 설계된 주파수 분할기는 100 MHz부터 3,000 MHz까지 동작하며, 2,900 MHz의 대역폭을 가지고 입력 주파수 1,400 MHz에서 -33 dBm의 입력 전력으로 변환 이득 14 dB를 갖도록 설계되었다. DC 전압 $V_{DD}=3V$에서 입력 전압 $V_{Peak}=0.2V$일 때 $I_{total}=30mA$가 흐르며, 변조 지수 m=0.5인 진폭 변조 신호의 반송파 주파수가 1,400 MHz에서 700 MHz로 분주되는 것을 확인하였다.

• 인터넷정보학회논문지
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• 제4권3호
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• pp.9-14
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• 2003

기존의 성도 정규화 방법은 화자 간 정규화의 정확성을 개선하기 위한 매우 좋은 방법이다. 본 논문에서는 피치 변경 발성에 기반을 둔 새로운 화자 내 warping 인수 추정 방법을 제안한다. 화자 내 피치 변경 발성은 성문과 성도에 의해 발생되는 음성의 음향학적 차이 때문에 음성의 특징 공간 분포는 다르게 나타날 것이다. 발성의 변동은 frequency 성분과 amplitude 성분의 두가지 유형이 있다. 성도 정규화는 화자 간 정규화 방법들 중에서 주파수 정규화 방법이다. 여기에서는 화자 내 정규화를 위하여 진폭 변동을 정규화하는 방법을 제안한다. 참조 피치와 입력 피치의 역비례 계산에 의해서 진폭 warping 인수를 결정하는 것이 가능하다. 성능 평가를 위한 인식 실험 결과 숫자와 단어 인식에서 0.4%∼2.3% 정도의 인식 오류가 감소되었다.

• 제어로봇시스템학회논문지
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• 제11권1호
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• pp.1-8
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• 2005

A new discretization algorithm for nonlinear systems with delayed input is proposed. The algorithm is represented by Taylor series expansion and ZOH assumption. This method is applied to the sampled-data representation of a nonlinear system with the time-delay input. Additionally, the delay in input is time varying and its amplitude is bounded. The maximum time-delay in input is assumed to be two sampling periods. The mathematical expressions of the discretization method are presented and the ability of the algorithm is tested for some of the examples. The computer simulation proves the proposed algorithm discretizes the nonlinear system with the variable time-delay input accurately.

• ETRI Journal
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• 제29권1호
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• pp.89-94
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• 2007

A mathematical model for the input-output characteristic of an amplifier exhibiting gain expansion and weak and strong nonlinearities is presented. The model, basically a Fourier-series function, can yield closed-form series expressions for the amplitudes of the output components resulting from multisinusoidal input signals to the amplifier. The special case of an equal-amplitude two-tone input signal is considered in detail. The results show that unless the input signal can drive the amplifier into its nonlinear region, no gain expansion or minimum intermodulation performance can be achieved. For sufficiently large input amplitudes that can drive the amplifier into its nonlinear region, gain expansion and minimum intermodulation performance can be achieved. The input amplitudes at which these phenomena are observed are strongly dependent on the amplifier characteristics.

• Journal of Power Electronics
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• 제11권5호
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• pp.655-661
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• 2011

This paper presents two topologies for single-stage single-phase double-buck type PFC converters, designed to operate at high power factor, near sinusoidal input currents and adjustable output voltage. Unlike the known buck type PFC topologies, in which the output voltage is always lower than the maximum input voltage, the proposed converters can operate at output voltages higher than the ac input peak voltage. A reduced number of switches on the main path of the current are another characteristic of the two proposed topologies. To shape the input line currents, a fast and robust controller based on a sliding mode approach is proposed. This active non-linear control strategy, applied to these converters allows high quality input currents. A Proportional Integral (PI) controller is adopted to regulate the output voltage of the converters. This external voltage controller modulates the amplitude of the sinusoidal input current references. The performances of the presented rectifiers are verified with experimental results.

• 동력기계공학회지
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• 제14권2호
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• pp.60-64
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• 2010

This paper introduces reliability improvement and time saving in eddy current inspection by signal characteristic optimization of multi-coil eddy current array probe. In the past, Multi-coil array probe and single probe were used for the gas turbine rotor surface inspection & defect evaluation. The multi-coil array probe was used for the broad area inspection. But the signal deviations among multi-coil array probe are maximum 28% in commercial probe. This differences were considered to impedance differences among coils, so it is very difficult to evaluate exact defect size. The signal deviations among multi-coil array probe are maximum 28% in commercial probe. So, single coil inspection was used for exact defect sizing. The purpose of this study is to improve signal deviations of multi-coil array probe. The introduced new technology can improves this deviation by adjusting input voltage in each coil. At first, apply same voltage in each coil and collect signal amplitude of each coil. And calculate new input voltage based on signal amplitude of each coil. If the signal amplitude deviation is within 5% among multi-coil array probe, the signal amplitude of multi-coil array probe is reliable. The proposed technology gives 2% signal deviation among multi-coil array probe. The proposed new technology gives reliability improvement and inspection time saving in eddy current inspection.

• Journal of Welding and Joining
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• 제11권3호
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• pp.34-47
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• 1993

용접에서 발생하는 열응력 및 잔류응력을 해석하기 위한 유한요소용 모델을 개발하였다. 여러 가 지 변수의 연구를 통하여 Ramp heat input function과 Lumped모델을 제시하였다. 용접부에 열입 력을 점차적으로 주기 위하여 Ramp heat input을 이용하였으며 Ramp input을 통하여 이차원 모 델에서의 이동열원의 영향을 고려하였고 실험치와 비교에서 최적 ramp시간을 결정하였다. 다층용 접에서는 용접 pass 에 비례하여 계산시간이 증가한다. 따라서 후판용접의 잔류응력계산에는 막 대한 계산시간이 필요하며 이를 줄이기 위하여 Lumped 모델을 개발하였다. 이 Lumped모델에서 는 각 용접층에 들어있는 용접 pass들을 하나의 lumped pass으로 이용하였으며 각 pass를 따로 계산한 모델 및 시험치와의 비교를 통하여 최적 lumped technique을 제시하였다. *****Finite element models were developed for thermal and residual stress analysis for the specific welding problems. They were used to evaluate the effectiveness of the various welding heat input models, such as ramp heat input function and lumped pass models. Through the parametric studies, thermal-mechanical modeling sensitivity to the ramp function and lumping techniques was determined by comparing the predicted results with experimental data. The kinetics for residual stress formation during welding can be developed by iteration of various proposed mechanisms in the parametric study. A ramp heat input function was developed to gradually apply the heat flux with variable amplitude to the model. This model was used to avoid numerical convergence problems due to an instantaneous increase in temperature near the fusion zone. Additionally, it enables the model to include the effect of a moving arc in a two-dimensional plane. The ramp function takes into account the variation in the out of plane energy flow in a 2-D model as the arc approaches, travels across, and departs from each plane under investigation. A lumped pass model was developed to reduce the computation cost in the analysis of multipass welds. Several weld passes were assumed as one lumped pass in this model. Recommendations were provided about ramp lumping techniques and the optimum number of weld passes that can be combined into a single thermal input.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.2562-2567
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• 2005

This paper suggests a new method discretization of nonlinear system using Taylor series expansion and zero-order hold assumption. This method is applied into the sampled-data representation of a nonlinear system with input time delay. Additionally, the delayed input is time varying and its amplitude is bounded. The maximum time-delayed input is assumed to be two sampling periods. Them mathematical expressions of the discretization method are presented and the ability of the algorithm is tested for some of the examples. And 'hybrid' discretization scheme that result from a combination of the ‘scaling and squaring' technique with the Taylor method are also proposed, especially under condition of very low sampling rates. The computer simulation proves the proposed algorithm discretized the nonlinear system with the variable time-delayed input accurately.