• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(1)
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• pp.421-424
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• 2001

In this paper, We have designed and fabricated VCO in two way, the common source and common gate circuit for I local oscillator of 60 GHz wireless LAN system. The VCO employed a GaAs MESFET for negative resistance and a varactor diode for frequency tuning. The common gate VCO was measured the phase noise -112 dBc/Hz at the 1 MHz frequency offset. The output power and the second harmonic frequency suppression were 7.81 dBm and -29.3 dBc when tuning voltage was 3V, respectively. The total size of VCO was 28.6$\times$12.14 $\textrm{mm}^2$.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.269-272
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• 2003

A low phase noise frequency synthesizer at X-Band which employs the subharmonic injection locking was designed and tested. The frequency synthesizer consists of two oscillators - master and slave : A 1.75GHz master oscillator made of PLL synthesizer produces 6th harmonic at 10.5GHz, which excites the following 10.5GHz slave oscillator. The realized frequency synthesizer has a 4.5dBm of output power, and a phase noise of -108dBc/Hz at the 100kHz offset frequency.

• 한국전자파학회논문지
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• 제9권6호
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• pp.843-849
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• 1998

24GHz 대역의 WLL 시스템용 전압제어발진기(Yca)를 설계하고 제작하였다. 위상잡음(C/N) 특성을 개선하기 위하여 품질계수가 높은 유전체 공진기를 공진부의 인덕터로 사용하였다. 5 V, 10 mA 바이어스 조건 에서 VCO를 측정한 결과 2210-2240 MHz의 주파수 대역에서 출력은 0 dBm, 위상잡음 특성은 10 kHz offset에서 100 dBc/Hz으로 매우 우수한 특성을 나타내었다. 따라서 제작된 VCO는 WLL 시스템에 적용할 수 있다고 생각된다.

• 대한전기학회논문지:시스템및제어부문D
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• 제52권4호
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• pp.205-211
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• 2003

In this paper we propose a disturbance design method to test a system's stability. It is shown that the time maximum disturbance is represented in bang-bang and state feedback form. To maximize the time severity index, the value of disturbance is determined by the associated switch curve. The original switch curve is vulnerable to model uncertainties and takes much calculation time. We propose an improved method to approximate the original switch curve. This reduces the computational time and implements sufficiently to test the stable system. Simulation results show how the approximate switch curve can be used to stress a system by driving it to oscillation along the maximum limit cycle.

• 대한전자공학회논문지
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• 제6권2호
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• pp.6-20
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• 1969

부저항소자인 턴넬다이오드와 수동선형부하로 부저항발진기를 구성하고 수동부하를 가변하여 주파수최대화에 관해서 연구했다. 이론적인 해석과 복소평면상의 임피이던스 궤적을 도시하고 병렬-RL부하와 저항부하의 두 경우의 최대발진주파수를 측정하여 두 경우의 실험결과를 보면 병렬-RL부하의 폭이 훨씬 높은 주파수를 발진하는 것을 알았다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1996년도 추계학술대회논문집; 한국과학기술회관, 8 Nov. 1996
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• pp.282-287
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• 1996

The non-linear torsional vibrations of the propulsion shafting system with viscous damper are considered. The motion is modeled by non-linear differential equations of second order. the equivalent system is modeled by two mass softening system with Duffing's oscillator. The steady state response of a equivalent system is analyzed for primary resonance only. Harmonic balance method as a non-linear vibration analysis technique is used. Jump phenomena are explained. The primary unstable region obtained by the Mathieu equation is investigated. Both theoretical and measured results of the propulsion shafting system are compared with and evaluated. As a result of comparisons with both data, it was confirmed that Duffing's oscillator can be used as a analysis method in the modeling of the propulsion shafting system attached viscous damper with non-linear stiffness.

• 소음진동
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• 제10권3호
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• pp.531-535
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• 2000

A three-parameter model of viscoelastic damper which has a non-linear spring as an element is incorporated into an oscillator. The behavior of the damper model shows non-linear hysteresis curves which is qualitatively similar to those of real viscoelastic materials. The motion is governed by get analytic solutions of the system. The frequency-response curves show that multiple solutions co-exist and that the jump phenomena can occur. In addition it is shown that separate solution branch exists and that it can merge with the primary response curve. Saddle-node bifurcation sets explain the occurences of such non-linear phenomena. A direct time intergration of the original equation of motion validifies the use of the harmonic balance method to this sort of problem.

• 한국음향학회지
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• 제13권3호
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• pp.71-77
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• 1994

수중에서 공기방울들의 선형 배열에 의해 방출된 음향의 주파수 특성을 이론 및 실험적으로 살펴보았다. 공기방울들의 상호 작용을 고전적 조화진동자의 결합으로 다루었으며, 이론적으로 공기방울들의 선형 배열을 인접한 공기방울들간의 효과만을 고려한 유효 결합 조화진동자 모델로서 제안하였다. 공기방울 중심 사이의 거리가 공기방울 직경의 두 배가 넘는 약한 결합의 경우에 대해, 제안된 유효 결합 조화진동자 모델은 실험 결과들과 잘 일치함을 보여주었다.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2002년도 종합학술발표회 논문집 Vol.12 No.1
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• pp.16-20
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• 2002

This paper describes the resistive FET mixer with low IF for the 4-Ch DBF(Digital Beam Forming) receiver with LNA(Low Noise Amplifier). This DBF receiver based on the direct conversion method is generally suitable for high-speed wireless mobile communications. A radio frequency(RF), a local oscillator(LO) and an intermediate frequency(IF) considered in this research are 2.09 ㎓, 2.08 ㎓ and 10㎒, respectively. The RF input power, LO input power and Vgs are used -10㏈m, 6㏈m and -0.4 V, respectively. In the 4-Ch resistive FET mixer with LNA, the measured IF and harmonic components of 10㎒, 20㎒, 2.09㎓ and 4.17㎓ are about -12.5 ㏈m, -57㏈m, -40㏈m and -54㏈m, respectively. The IF output power observed at each channel of 10㎒ is about -12.5㏈m and it is higher 27.5 ㏈m than the maximum harmonic component of 2.09㎓. Each IF output spectrum of the 4-Ch is observed almost same value and it shows a good agreement with the prediction.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.449-454
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• 2000

A three-parameter model of viscoelastic damper, which has a non-linear spring as an element is incorporated into an oscillator. The behavior of the damper model shows non-linear hysteresis curves which is qualitatively similar to those of real viscoelastic materials. The motion is governed by three-dimensional non-linear dynamical system of equations. The harmonic balance method is applied to get analytic solutions of the system. The frequency-response curves show that multiple solutions co-exist and that the jump phenomena can occur. In addition, it is shown that separate solution branch exists and that it can merge with the primary response curve. Saddle-node bifurcation sets explain the occurences of such non-linear phenomena. A direct time integration of the original equation of motion validifies the use of the harmonic balance method to this sort of problem.