• 한국통신학회논문지
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• 제22권1호
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• pp.12-20
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• 1997

Physical interconnect such as Printed Circuit Board(PCB) traces introduces new challenges for parameter extraction and delay calculation for high-speed system design. PCB traces are dominated by frequency dependent LC propagation which makes precharacterization difficult for all possible configurations. Moreover, simulating the transient behavior of the trace for noise and delay analysis requries the combined used of a variety of models and techniques for efficiently handling lossy, low-loss, frequency dependent, and coupled transmission lines together with lumped elements. In this paper we explain how the frequency dependence caused by ground plane proximity and skin effects can be modeled using the adstracted models. These abstracted (lumped) models are SPICE-compatible and can be simulated in time-domain, along with precharacterized lumped parasitic elements and nonlinear driver and load models.

• ETRI Journal
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• 제30권4호
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• pp.535-545
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• 2008

This paper introduces a systematic top-down and bottom-up design methodology to assist the designer in the implementation of continuous-time (CT) cascade sigma-delta (${\Sigma}{\Delta}$) modulators. The salient features of this methodology are (a) flexible behavioral modeling for optimum accuracy-efficiency trade-offs at different stages of the top-down synthesis process, (b) direct synthesis in the continuous-time domain for minimum circuit complexity and sensitivity, (c) mixed knowledge-based and optimization-based architectural exploration and specification transmission for enhanced circuit performance, and (d) use of Pareto-optimal fronts of building blocks to reduce re-design iterations. The applicability of this methodology will be illustrated via the design of a 12-bit 20 MHz CT ${\Sigma}{\Delta}$ modulator in a 1.2 V 130 nm CMOS technology.

• 전기학회논문지
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• 제59권1호
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• pp.176-183
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• 2010

This paper presents some practical design issues that should be carefully considered when a notch filter is included in a linear feedback controller. A notch filter is generally used to compensate the effects of resonant modes that may result in poor performance. It is very common that the practical engineers prefer to add such a notch filter after having previously designed a feedback controller without the filter. It is known that the resulting performance by this approach is not seriously different from when a feedback controller is designed for a plant previously compensated by a notch filter. However, we will point out that there are some cases where both approaches have different performances. In order to show this, a low-order controller design using the partial model matching method has been applied to a linear time invariant (L Tn model. The results suggest that there is a tendency to achieve much better time responses in terms of reducing the overshoot and shortening the settling time, and in the frequency domain characteristics such as the sensitivity function and the stability margins when the design of a feedback controller after including a notch filter is carried out.

• 한국정밀공학회지
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• 제17권8호
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• pp.126-133
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• 2000

This paper is a study on robust PID controller tuning technique using the frequency region model matching method.To design the robust PID controller satisfying disturbance attenuation and robust tracking property for a reference input first an {{{{ETA _$\infty$}}}} controller satisfying given performances is designed using an H$_{\infty}$ control method, And then the parameters(proportional gain integral gain and derivation gain) of the robust PID controller with the performances of the desinged H$_{\infty}$ controller are determined using the model matching method at frequency domain. in this paper this PID controller tuning technique is applied to PID speed controller design for BLDC motors. Consequently simulation results show that the proposed PID speed controller satisfies load torque disturbance attenuation and robust tracking property and this study has usefulness and applicability for the speed control system; design of BLDC motors.

• 한국광학회지
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• 제13권1호
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• pp.27-31
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• 2002

본 논문에서는 광자 크리스탈로 구성된 1$\times$4 광 분배기를 설계하여 특성을 Finite-Difference Time-Domain 방법을 사용하여 고찰하였다. Simulation한 결과 bend에서의 4가지 광자 크리스탈 배열 구조와 입사파의 주파수에 따라 투과 특성이 변하는 것을 관찰하였다. 투과 특성이 가장 좋은 bend구조로 1$\times$4광 분배기를 설계하고 특정 주파수를 입사시킨 결과, 입사파의 파워가 4개로 균등히 나누어 짐과 전체 전송 효율이 약 93%임을 관찰하였다.

• 한국통신학회논문지
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• 제24권6B호
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• pp.1142-1148
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• 1999

본 논문에서는 Ku-밴드의 마이크로파 대역에서 위상배열 안테나에 사용 가능한 결합선로를 이용하여 위상천이기에서 기존에 고려하지 않았던 주파수에 따른 분산특성을 전파(Full-wave) 해석방법인 SDA(Spectral Domain Approach)를 사용하여 정확히 해석하였다. 또한 비대칭 결합선로를 사용하는 위상천이와 유전치 덮개층이 부가된 위상천이기의 설계를 제안하였다. 현재 사용되고 있는 대칭 결합선로를 이용한 쉬프만 위상천이기와 비교하여, 이에 대한 위상응답의 특성변화에서 통과대역의 위상편차가 줄고 대역폭이 확대되어 광대역 특성이 개선되는 것을 이론적으로 해석하고 실험을 통하여 검증하였다.

• 한국항해학회지
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• 제23권2호
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• pp.61-66
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• 1999

It is being more and more difficult to suppress emissions from electronic products using PCB(Printed Circuit Board) to the limit. Therefore, the exact evaluation of the emission from PCB has been more important to reduce the required time and the cost at the design phase of the products, especially on board ship's equipments. This research has evaluated the emission radiated from PCB based on the theoretical approach of SDA(Spectral Domain Analysis), which is available to analyze microwave stripline, coplanar line, patch antenna, etc. According to the theoretical results, it has been clearly shown that the emission radiated from PCB is reduced as the thickness of PCB is thinner, the permittivity of PCB is higher, the length of stripline is shorter, and the frequency is lower.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 학술대회 논문집 정보 및 제어부문
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• pp.628-631
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• 2005

In this paper, we propose tuning method of PID-PD controller to satisfy design specifications in frequency domain as well as time domain. The proposed tuning method of PID-PD controller that consist of the convex set of PID and PI-PD controller controls the closed-loop response to locate between the step responses, and Bode magnitudes of closed-loop transfer functions controlled by PID and PI-PD controller. The controller is designed by the optimum tuning method to minimize the proposed specific cost function subject to sensor noise insensitivity and robust stability. Its effectiveness is examined by the case study and analysis.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.607-608
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• 2008

Locking time of the DLL is the important design issue in case of clock gating for low power system. For precise analysis of the locking speed of the DLL, this paper analyzes the locking process of the DLL in time domain. Analysis result shows that the value of the DLL bandwidth over reference frequency should be limited to below 1 ($i.e.w_n/F_{REF}<1$) for the stable operation and relation between bandwidth and lock time is expressed by log function.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.457-464
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• 2001

The aeroacoustic phenomena in the simple rectangular open cavity are well published by many researchers. But the geometry shapes of aircraft landing gear wells, weapon bays, etc. are more complicate than that of the simple retangular cavity. They are more similar to the cavity having cover-plates at adges, or Helmholtz resonator. Therefore, the effects of cover-plates existing on edges of rectangular open cavity are numerically investigated in this paper. The compressible Navier-Stokes equations are solved for two-dimensional cavities with laminar boundary layers upstream. The high-order and high-resolution numerical schemes are used for the evaluation of spatial derivatives and the time integration. Physically correct numerical boundary conditions and buffer zone techniques are implemented to produce time-accurate solutions in the whole computation domain. The computational domain is large enough to directly resolve a portion of the radiated acoustic field. Results show that the cover-plates existing on edges of cavity reduce the noise convected from cavity, make the frequency of noise become higher, and change the directivity pattern. So these results can be used in the design of a low noise cavity.