• 한국전자파학회논문지
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• 제10권7호
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• pp.1022-1032
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• 1999

X 대역에서 동작하는 마이크로스트립 원형 편파 개구연-패치 $8\times8$ 배열 안테나의 방사 특성에 대한 연구가 수행되었다. 복사 소자는 접지변에 모서리가 잘린 정사각형 개구면과 그 안에 기울어진 패치로 구성했고, 접지변 의 반대편에서 마이크로스트립 라인으로 coupling 시켰다. 상호결합을 최소화 하고, gam을 최대화 하기 위하여 소자 간의 간격은 $0.8\lambda_0$로 선택하였다. 급전구조는 병렬 형태로 구성하여 각 소자에 4개의 Wilkinson 분배기와 2개의 T - junction 분배기를 거쳐 전력을 공급한다. $8\times8$ 배열 안테나를 lOGHz에서 측정한 결과directivity는 26.3 d dBi, gain은 22.2 dBi, axial ratio는 2.97 dB, side lobe level은 12.7 dB로 나타났다. 배열의 크기가 커짐에 따라 d directivity는 증가하는 반면 효율은 감소하는 것을 확인하였다.

• 한국소음진동공학회논문집
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• 제12권11호
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• pp.833-839
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• 2002

As the demand for slim laptops requires low-height optical disc drives, vibration problems of optical disc drives are of great concern. Additionally, with the decrease of a track width and a depth of focus in high density drives, studies on vibration resonance between mechanical parts become more important. From the vibration point of view, the performance of optical disc drives is closely related with the relative displacement between a disc and an objective lens which is controlled by servo mechanism. In other words, to read and write data properly, the relative displacement between an optical disc and an objective lens should be within a certain limit. The relative displacement is dependent on not only an anti-vibration mechanism design but also servo control capability. Good servo controls can make compensation for poor mechanisms, and vice versa. In a usual development process, robustness of the anti-vibration mechanism is always verified with the servo control of an objective lens. Engineers partially modify servo gain margin in case of a data reading error. This modification cannot correct the data reading error occasionally and the mechanism should be redesigned more robustly. Therefore it is necessary to verify a mechanism with respect to the possible servo gain plot. In this study we propose the experimental verification method for anti-vibration mechanism with respect to the existing servo gain plot. Thismethod verifies axial vibration characteristics of optical disc drives on the basis of transmissibility. Using this method, we verified our mechanism and modified the mechanism for better anti-vibration characteristics.

• ETRI Journal
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• 제40권5호
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• pp.561-569
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• 2018

Modern communication systems employ wideband antennas with circular polarization (CP) radiation. In this work, asymmetric modified bow-tie (ABT) and symmetric modified bow-tie (SBT) slotted circularly polarized single-point probe-fed circular patch antennas with dimensions of $40mm{\times}40mm$ for wideband applications are proposed. A 10 dB RL bandwidth of 350 MHz with CP, 3 dB axial ratio (AR) bandwidth of 100 MHz, peak gain of 4.9 dBic, and 10 dB RL bandwidth of 530 MHz with CP, 3 dB AR bandwidth of 140 MHz, peak gain of 5 dBic are obtained for ABT and SBT slotted circular patch antennas, respectively. The proposed SBT slotted patch is scaled up and down to $50mm{\times}50mm$ and $30mm{\times}30mm$, respectively. The proposed scaled-up version offers 10 dB RL and 3 dB AR bandwidths of 340 MHz and 80 MHz, with a peak gain of 5 dBic. The scaled-down version offers 10 dB RL and 3 dB AR bandwidths of 710 MHz and 180 MHz, with a peak gain of 5.25 dBic. These prototypes are suitable to work in IEEE 802.11a WLAN, ISM, and IEEE 802.11ac applications. The measured and simulated results are then discussed and compared.

• 한국전자파학회논문지
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• 제13권4호
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• pp.393-400
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• 2002

본 논문에서는 원형편파를 발생시키기 위한 여러 가지 방법 중 단일 급전 십자개구 결합 방식이 가지는 협대역의 축비 대역폭을 개선하기 위해 단일 급전으로 하이브리드 급전의 효과를 가져을 수 있는 직렬 급전 십자개구 결합 마이크로스트립 안테나를 제안하고, 기존에 발표된 단일 급전 십자개구 결합 안테나와의 축비 대역폭, 이득, 방사패턴, 그리고 임피던스 대역폭 등과 비교하여 개선된 축비 대역폭 특성을 제시하여 제안된 안테나의 타당성을 보였다. 또한 제안된 단일 안테나를 이용해 2$\times$2 배열 안테나로 확장하는 과정에서 시퀀셜 로테이션 기법을 적용함으로써 더욱 넓은 축비 대역폭을 화보할 수 있도록 하였다. 직렬급전 단일 안테나와 2$\times$2 배열 안테나의 측정된 축비 대역폭은 110 MHz(4.6 %)와 420 MHz(17.5 %)를 보였고, 측정된 임피던스 대역폭 (VSWR<1.5)은 240 MHz(10%)와 500 MHz(20.8%)출 가졌으며, 이득 측정결과에서는 단일 안테나와 2$\times$2 배열 안테나 모두 3 dB 이득 대역폭에서 400 MHz(16.7%) 이상의 평탄 특성을 가지며 최대이득에서는 8.2 ㏈i와 12.5 ㏈i의 이득특성을 보여주었다.

• ETRI Journal
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• 제32권2호
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• pp.312-318
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• 2010

A small reconfigurable patch antenna is proposed to achieve polarization diversity for digital multimedia broadcasting systems at 2.6 GHz. To obtain polarization diversity, a pair of on-slit PIN diodes is inserted in each diagonal of a cross-shaped patch. Thus, four PIN-diodes on these slits are utilized to change the connection of the slits and thus achieve polarization. Bias circuits for the diodes are allocated in the cutting corner of the cross-shaped patch to minimize the antenna size. The antenna produces left-hand circular polarization, right-hand circular polarization, or linear polarization, depending on the PIN-diode status. Analysis of circular polarization operation is explicated. Measurements show a gain of about 1.5 dB, a cross polarization of about -20 dB, and an axial ratio of about 2.5 dB.

• ETRI Journal
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• 제37권1호
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• pp.26-31
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• 2015

Axial-ratio (AR) bandwidth enhancement is achieved for a circularly polarized (CP) cylindrical dielectric resonator antenna (DRA) using a wideband hybrid coupler (WHC) combined with dual probe feed. The presented WHC, comprised of a Wilkinson power divider and a wideband $90^{\circ}$ shifter, delivers good characteristics in terms of 3 dB power splitting and consistent $90^{\circ}$ (${\pm}5^{\circ}$) phase shifting over a wide bandwidth. In turn, the proposed CP DRA, for the employment of the WHC, in place of conventional designs, provides a significant enhancement on AR bandwidth and impedance matching. The antenna prototype with the WHC exhibits a 3 dB AR bandwidth of 48.66%, an impedance bandwidth of 52.5% for voltage standing wave ratio (VSWR) ${\leq}2$, and a bandwidth of 44.66% for a gain of no less than 3 dBi. Experiments demonstrate that the proposed WHC is suitable for broadband CP DRA design.

• 설비공학논문집
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• 제3권2호
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• pp.131-141
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• 1991

A method of optimum design of an axial rotary sensible heat exchanger for the heat recovery of exhaust gas from the air conditioning space was developed in consideration of economics of investment cost and profit according to the installation of heat exchangers. Leakage rate of exhaust gas was calculated and the correlation for the pressure drop due to leakage of exhaust gas was proposed. Heat transfer between the matrix and exhaust and intake gas was analysed to calculate the effectiveness of heat exchanger, which was used for the optimum design of rotary heat exchanger. The results show that optimum rotational speed increases as the length of rotor increases and there exists optimum NTU which maximizes the gain of total cost according to the installation of rotary heat exchanger.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2005년도 종합학술발표회 논문집 Vol.15 No.1
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• pp.297-302
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• 2005

Right hand circularly polarized Ka band microstrip patch array antenna was designed, manufacture and measurement were carried out. In order to lower axial ratio performance sequential rotation array technique was used. With mono-pulse feed There are sum and delta channel. Waveguide to microstrip transition was used. The 512 array antenna was performed which axial ratio is about 1.ldB in the half power beam width and also 1.ldB at the normal direction. Directivity gain of designed antenna is 32dB.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2005년도 종합학술발표회 논문집 Vol.15 No.1
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• pp.231-234
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• 2005

In this paper, Dual-polarized Tx/Rx antenna for RFID reader is designed and fabricated to apply to RFID reader. Each feeding network of Tx/Rx is designed to improve the port-isolation and cross-polarization, and sequential rotation feeding scheme has been applied to increase of axial ratio bandwidth. Measured results show that 2.35dBi of antenna gain in 900MHz$\sim$928MHz, 150MHz of 3dB axial ratio bandwidth, -38dB$\sim$-40dB of port-isolation, and -30dB$\sim$-40dB of cross-polarization.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1115-1119
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• 2007

Five control methods (Speed Control, PID Gain Scheduling, Loop Time Control, Simple PID, Switching Control) have been applied to the control of an Inline Co-axial valve by the simulation of AMESim. The simulation results have shown that the speed control method is the most stable and the fastest way to reach to the set point in the simulation of the flow control. Moreover, It has been found that the five control methods have the almost same characteristics in the power consumption, the counter electromotive force, and the motor angular velocity. According to the analysis results, the fast and stable control characteristics of the speed control method is the most suitable for the flow control using a inline co-axial valve with a DC(BLCD) motor.