• 전기학회논문지
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• 제65권6호
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• pp.1032-1037
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• 2016

In this paper, the method of isolation enhancement for the mobile phone MIMO antenna of LTE class 40(2300~2400MHz) was studied. Design of MIMO antenna was based on the hybrid antenna that operates both a monopole and an IFA(Inverted F Antenna). A structure for the isolation enhancement which controls induced electric field on the ground plane is located between MIMO antenna, and was not connected with the ground but apart 0.3mm. A MIMO antenna that operates on class 3~40(1710~2400MHz) of LTE service bands and a structure for the isolation enhancement at the class 10 band were designed. VSWR measurement of implemented antenna on the FR4 board showed within 3:1 at entire design bands, and isolation between antennas at the class 40 band was less than -30dB. Isolation was enhanced more than 20dB by the studied structure. ECC(Envelope Correlation Coefficient) for MIMO performance was under 0.1, and antenna average gain and efficiency measured in the anechoic chamber were -4.28~-1.40dBi and 37.32~72.36% respectively.

• Earthquakes and Structures
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• 제16권5호
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• pp.523-532
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• 2019

Different types of gas reservoir such as Liquid Natural Gas (LNG) are among the strategic infrastructures, and have great importance for any government or their private owners. To keep the tank and its contents safe during earthquakes especially if the contents are of hazardous or flammable materials; using seismic protection systems such as base isolator can be considered as an effective solution. However, the major deficiency of this system can be the large deformation in the isolation level which may lead to the failure of bearing system. In this paper, as a solution, the efficacy of an optimally designed combined vibration control system, the combined laminated rubber isolator and rotational friction damper, is investigated to evaluate the enhancement of an existing metal tank response under both far- and near-field earthquakes. Responses like impulsive and convective accelerations, base shear, and sloshing height are studied herein. The probabilistic framework is used to consider the uncertainties in the structural modeling, as well as record-to-record variability. Due to the high calculation cost of probabilistic methods, a simplified structural model is used. By using the Mont-Carlo simulation approach, it is revealed that this combined isolation system is a highly reliable system which provides considerable enhancement in the performance of reservoir, not only leads to the reduction of probability of catastrophic failure of the tank but also decrease the reservoir damage during the earthquake. Moreover, the relative displacement of the isolation level is controlled very well by this combined system.

• 한국전자파학회논문지
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• 제27권3호
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• pp.229-238
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• 2016

본 논문에서는 배열안테나의 성능개선의 한 방법으로 표면파제어를 통한 격리도 개선에 관한 연구를 진행하였다. 배열의 소자 간 격리도 개선을 위해 Perfect Magnetic Conductor(PMC)와 SOFT-표면을 도입하였으며, 접지면의 중앙부에 이들을 삽입하여 모의실험을 진행함으로써 격리도 변화와 성능개선 유무를 알아보았다. 모의실험 결과, E-plane 배열에서 PMC와 SOFT-표면 모두 최대 40 dB 이상의 격리도 향상과 더불어 최대 2.2 dBi 정도의 이득 개선을 확인하였으며, H-plane 배열의 경우, 표면파 전파를 통한 상호결합보다 공기 중의 field를 통한 상호결합이 보다 크게 작용하는 것을 확인하였다. 이 연구는 향후 소형 배열안테나 개발 및 배열안테나의 성능개선 등에 유용하게 사용될 것이다.

• Journal of Electrical Engineering and Technology
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• 제8권4호
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• pp.850-855
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• 2013

This paper proposes a novel design for a compact, high-isolation WCDMA indoor repeater antenna. The proposed antenna consists of a patch antenna and metamaterial absorber. The required WCDMA bandwidth is obtained by utilizing the coupling between the main and the parasitic patches. In addition, high isolation is achieved using the metamaterial absorber, which has an absorption of about 98% at 2.1 GHz. Overall, the proposed antenna has a gain of over 7 dBi, a Voltage Standing Wave Ratio (VSWR) of less than 2, more than 85 dB of isolation between the service and donor antennas over the WCDMA band and a total volume of the proposed antenna only $70mm{\times}70mm{\times}43.8mm$.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.903-908
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• 2006

As environmental vibration requirements on precision equipment become more stringent. use of pneumatic isolators has become more popular and their performance is subsequently required to be further improved. Dynamic performance of passive pneumatic isolators is related to various design parameters in a complicated manner and, hence, is very limited especially in low frequency range by volume of chambers. In this study, an active control technique, so called time delay control which is considered to be adequate for a low frequency or nonlinear system, is applied to a single chamber pneumatic isolator. The procedure of applying the time delay control law to the pneumatic isolator is presented and its effectiveness in enhancement of transmissibility performance is shown based on simulation and experiment. Comparison between passive and active pneumatic isolators is also presented.

• Earthquakes and Structures
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• 제23권1호
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• pp.87-100
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• 2022

Limiting the displacement of seismic isolators causes a pounding phenomenon under severe earthquakes. Therefore, the ASCE 7-16 has provided minimum criteria for the design of the isolated building. In this research the seismic response of isolated buildings by Triple Friction Pendulum Isolator (TFPI) under the impact, expected, and unexpected mass eccentricity was evaluated. Also, the effect of different design parameters on the seismic behavior of structural and nonstructural elements was found. For this, a special steel moment frame structure with a surrounding moat wall was designed according to the criteria, by considering different response modification coefficients (RI), and 20% mass eccentricity in one direction. Then, different values of these parameters and the damping of the base isolation were evaluated. The results show that the structural elements have acceptable behavior after impact, but the nonstructural components are placed in a moderate damage range after impact and the used improved methods could not ameliorate the level of damage. The reduction in the RI and the enhancement of the isolator's damping are beneficial up to a certain point for improving the seismic response after impact. The moat wall reduces torque and maximum absolute acceleration (MAA) due to unexpected enhancement of mass eccentricity. However, drifts of some stories increase. Also, the difference between the response of story drift by expected and unexpected mass eccentricity is less. This indicates that the minimum requirement displacement according to ASCE 7-16 criteria lead to acceptable results under the unexpected enhancement of mass eccentricity.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2003년도 하계학술연구발표회 및 한.일 공동심포지엄
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• pp.134-135
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• 2003

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2008년도 정보통신설비 학술대회
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• pp.459-462
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• 2008

This paper describes the design of single body type repeater antenna for isolation enhancement between donor and receptor antennas. The antenna system consists of cavity, triangular patch antenna and cavity reflector. The antenna satisfies return-loss and isolation specifications in the desired band while the broadside gain is a little bit short from the spec.

• 한국구조물진단유지관리공학회 논문집
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• 제11권3호
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• pp.185-191
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• 2007

본 연구에서는 주거용 무량판구조의 내진성능을 개선하기 위한 면진적용 가능성을 평가하였으며, 시간이력 해석을 위한 지진기록 사용에 대한 문제점을 제시하였다. 면진층 강성 및 주기 평가 및 포락해석법을 적용하여 면진전 비틀림 모드가 강한 구조물을 면진시스템 적용으로 내진성능을 개선하였다. 지진기록 사용 및 크기 조절효과의 적정성을 평가하기 위하여 DBE, MCE, ASCE 7-05의 1.4DBE 의해 크기를 조정한 시간이력 해석결과를 비교한 결과, 구조물의 지반조건과 유사한 조건에서 관측된 지진기록 및 지진기록의 응답이 설계규준 응답스펙트럼의 평균${\pm}$표준편차 범위 안에 있는 기록을 사용하는 것이 적절한 것으로 판단된다.

• 전기전자학회논문지
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• 제17권3호
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• pp.385-392
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• 2013

본 논문에서는 근접물체에 둔감하도록 평면 안테나의 송신단과 수신단 사이의 분리도를 개선하는 회로구조를 제안하였으며 5.8GHz ISM 대역에서 생체신호를 검출하는 도플러 레이다 센서에 적용하였다. 방사패치를 중심으로 2개의 3dB $90^{\circ}$ 전력분배기 들을 송신경로와 수신경로에 배치하여 평형회로 구조를 구성하였다. 이는 안테나에 근접된 물체가 있어도 높은 송수신 분리도 및 우수한 입출력 반사계수를 제공한다. 제안된 회로구조에 대한 이론 전개와 시뮬레이션을 통해 타당성을 확인하였고 제작된 시제품을 측정하여 입증하였다. 인체가 2mm까지 접근하여도 ISM대역에 걸쳐 송신단과 수신단에서 16dB 이상의 반사손실과 최소 30dB 이상의 분리도가 측정되었다.