• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.21 no.3
• /
• pp.753-762
• /
• 1996

In this paper, aperture coupled stacked microstrip array antennas are proposed and their operating characteristics are analyzed based on analytical. In order to evaluate mutual coupling between slot-coupled microstrip patches in finite array, analysis uses the reciprocity theorem and the spectral domain Green's functions for dielectric slab in a moment method solution for the unknown patches and solts current distrbution. By introducing an N-port equivalent network, the impedance matrix of an affay of N-element slot-coupled patches is evaluated directly from its network current matix of order N$^{2}$, and it can be programmed to be run on a PC. Numerical results show mutual coupling, radiation pattern, active reflection coefficient versus scan angle, radiation efficiency and active element gain pattern.

• Proceedings of the Korean Institute of Communication Sciences Conference
• /
• 2004.11a
• /
• pp.416-416
• /
• 2004

• Information and Communications Magazine
• /
• v.25 no.2
• /
• pp.32-40
• /
• 2008

본고에서는 최근 많은 연구가 진행되고 있는 분야인 WBAN(Wireless Body Area Network)과 이 에 사용되는 안테나 기술에 대해 언급하고자 한다. WBAN은 응용 분야에 따라 medical WBAN과 non-medical WBAN으로 구분할 수 있고, 디바이스 위치에 따라 wearable WBAN과 implant WBAN으로 구분 지을 수 있다. WBAN의 가장 큰 특징은 인체 내부 또는 인체와 매우 근접한 환경에서 시스템이 동작 한다는 것인데, 이 같은 경우 인체 매질에 의한 영향을 고려해야 한다. 특히 안테나는 주변 매질 특성에 의해 동작특성이 크게 좌우되므로 인체 매질 특성을 고려한 안테나 설계가 요구된다. 이를 위해 서론에서 WBAN 기술에 대해 간단히 소개하고, 본론에서는 WBAN 안테나 설계 시 고려해야할 전파 환경 특성 및 WBAN에 적합한 안테나 설계 기술에 대해 정리하고 몇 가지 사례를 들어 분석한다. 그리고 결론에서 WBAN 안테나 설계 기술에 관한 정리 및 WBAN 안테나 분야에서 향후 연구해야 할 내용에 대해 언급하기로 한다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.10 no.7
• /
• pp.1053-1064
• /
• 1999

In this paper, to transmit and receive the differently polarized signals simultaneously with a single antenna system, the dual-frequency microstrip array antenna with dual-polarization is proposed and designed. This antenna operates simultaneously at 14.25 GHz and 12.50 GHz. To extend to two dimensional array, microstrip feed line and coaxial probe through via-hole used.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.11a
• /
• pp.559-562
• /
• 2000

In this paper, coplanar waveguide fed antennas (CPWFAs) insetting two slits to boundary of the square microstrip patch are presented. These slits play roles in not only lowering a resonant frequency but also fine-tuning for the proposed antenna together with open stub of CPW feed line. The CPWFAs were designed and manufactured using microwave dielectrics (Al,Mg)TaO$_2$ having high dielectric-constant ($\varepsilon$r=20). The return loss and input impedance of the CPWFAs were investigated in terms of the slit length and open stub length of CPW feed line. It is shown that a resonant frequency decreases as the slit length increases.

• Proceedings of the KIEE Conference
• /
• 1999.07d
• /
• pp.1852-1854
• /
• 1999

In order to enhance satellite communication system performance, filters are required with the characteristics of sharp skirt, low insertion loss, and high power handling capability. But the performance of microwave passive filters is significantly declined by the conduction losses, especially in case of planar structures using film conductors. By using high temperature superconducting(HTS) film material as the conductor, higher performance could be expected. We have designed and developed narrow bandpass filters using haripin-type superconducting microstrip line for satellite communication. High quality superconducting YBCO thin films have been grown on MgO substrates by pulsed laser deposition(PLD) The deposited YBCO films were patterned by conventional wet-etching process. The transition temperatures of these films had shown 86 - 89 K. The film thicknesses were about 500 nm. Experimental results are presented for the insertion loss and return loss of the filter at 60 K.

• Proceedings of the KSME Conference
• /
• 2007.05b
• /
• pp.2303-2308
• /
• 2007

Experiments were performed to determine the thermal (or turbulent) diffusion coefficient (TDC) and to investigate the critical heat flux (CHF) performance in the 5${\times}$5 rod bundle with 5 unheated rods which are supported by Hybrid Mixing Vane. In this study, HFC-134a fluid was used as working fluid and the fluid temperature were measured in the important subchannels. To determine the TDC value, the measured fluid temperatures were compared with the predicted values obtained from the MATRA code. The best optimized value of ${\beta}$ was found to be 0.02 by considering prediction statistics, i.e., average and standard deviations of the differences between the experimental results and code calculations. Using the best optimized value of ${\beta}$ as 0.02, the MATRA code predicts the test results of the fluid temperature within ${\pm}$1.0 % of error. According to the experimental results on CHF of 5 non-heating guide tubes, the case with non-heating guide tube showed a little good performance in terms of CHF.

• Proceedings of the KSME Conference
• /
• 2001.06d
• /
• pp.821-827
• /
• 2001

As one of the advanced design features of the Korea next generation reactor, direct vessel injection (DVI) system is being considered instead of conventional cold leg injection (CLl) system. It is known that the DVI system greatly enhances the reliability of the emergency core cooling (ECC) system. However, there is still a dispute on its performance in terms of water delivery to the reactor core during the reflood period of a large-break loss-of-coolant accident (LOCA). Thus, experimental validation is under progress. In this paper, a new scaling method, using time and velocity reduced linear scaling law, is suggested for the design of a scaled-down experimental facility to investigate the direct ECC bypass phenomena in PWR downcomer.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.13 no.4
• /
• pp.342-350
• /
• 2002

In this paper, aperture coupled U-slot microstrip antenna with wideband stub is investigated. The dielectric constant of the substrate is 2.2 and the hight of the substrate is 62 mil. The impedance bandwidth (VSWR<1.5) of U-slot antenna with wideband stub is about 10 %. The bandwidth characteristic of U-slot antenna wish wideband stub is compared with that of antenna without it. And the results of parameter studies of the wideband stub provides the optimum characteristics of bandwidth and matching.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.17 no.6 s.109
• /
• pp.556-561
• /
• 2006

In this paper, a frequency reconfigurable slot antenna which has a bandwidth-enhanced characteristic is proposed. The proposed antenna consists of two parts; the wide slot and the narrow slot, to increase the bandwidth of the antenna and have the frequency reconfigurable characteristic. The wide slot has triangular shape and makes the bandwidth increased, and the narrow slot can mount PIN diodes. By changing on/off state of PIN diodes, the total length of the slot is changed. From this characteristic, the proposed antenna can finally control the center frequency and minimize variation of the impedance matching.