• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1599-1600
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• 2015

본논문은 철도의 무선통신의 링크거리 확보를 위하여 아테나의 이득을 높이는 방법을 제시한다. 안테나의 이득을 높이기 위한 방법으로 안테나 상면에 유전체층을 사용하며 유전체 상면에서 전계의 위상이 동일하도록 거리에 따른 유효유전율이 다른 구조를 사용하였다. 원하는 유효유전율을 얻기 위하여 유전체에 구멍을 뚫은 구조를 사용하였으며, 시뮬레이션 결과 안테나의 이득이 향상되는 것을 확인하였다. 동작주파수 5.8GHz에 대해서 유전체층이 없는 패치안테나의 경우 이득이 4.66dB이며 제안한 유전체층이 있는 경우 이득이 9.36으로 기존의 안테나보다 4.5dB 개선을 하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.2
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• pp.157-167
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• 2003

In this paper, to reduce the resonant length of patch, microstrip patch antenna of linear polarization which is suppressed at two radiation edges is designed and fabricated at the frequency of 1.575 GHz. The result is like that the resonant length of patch is 45 mm and the length reduction effect is 43.8 % when it is compared with that(80 mm) of plane type. The gain is 4.4 dBd and -3 dB beamwidths are 112$^{\circ}$ and 66$^{\circ}$ in the E-plane and H-plane, respectively. Also, to reduce the size of patch, microstrip patch antennas those are suppressed at four radiating comers are designed and fabricated at the same frequency in the linear and circular polarization, respectively. For linear polarization, at the 1.2 of width/length(W/L) ratio, the patch area is 53 mm $\times$ 63.6 mm and the size reduction effect is 56.1 % when compared with that(80 mm $\times$ 96 mm) of plane type. The gain is 4.3 dBd and the -3 dB beamwidths are 120$^{\circ}$ and 78$^{\circ}$ in the E-plane and H-plane, respectively. For circular polarization, the patch size(54.2 mm $\times$ 61.5 mm) is reduced by 47.2 % than that(76 mm $\times$ 83 mm) of plane type. -3 dB beamwidth of horizontal polarization in the z-x plane and vortical polarization in the y-z plane are 108$^{\circ}$ and 93$^{\circ}$, respectively and this means the increasement in both planes by 52$^{\circ}$ and 27$^{\circ}$ than those of plane type. The maximum gain is 2.5 dBd in the horizontal polarization in the z-x plane. Axial ratio is 1.5 dB at 1.575 GHz and the 2 dB axial ratio bandwidth(ARBW) is 20 MHz(1.3 %).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.9
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• pp.907-915
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• 2002

In this paper, a compact digital phase shifter to be used an active phased array antenna system for satellite communications was proposed. The even and odd mode analysis for a given reflection-type phase shifter, which uses a folded hybrid coupler as a base element, was performed and the design parameters were derived. Also, to verify experimentally the electrical performances of the proposed structure, X-band 4-bit digital phase shifter was designed and fabricated using Teflon soft substrate $({\varepsilon}_r; =\;2.17)$. Its circuit size was less than 3.5 cm $\times$ 3.0 cm, and it exhibited at least 50 % size reduction as compared with the conventional unfolded configuration. The experimental results of the fabricated phase shifter showed that the average insertion loss and insertion loss variation were less than 3.5 dB, $\pm$ 0.6 dB within the operating band, 7.9 ~ 8.4 GHz, respectively. And, input and output return loss were more than 10 dB, respectively. Also, the phase response of the phase shifter showed 4-bit operation with $\pm$3$^{\circ}$ rms phase error.

• Journal of Magnetics
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• v.18 no.2
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• pp.178-182
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• 2013

We have developed a new non-conventional electron paramagnetic resonance (EPR) spectrometer, in which no resonant cavity was used. We previously demonstrated a wide frequency range operation of an EPR spectrometer using two loop antennas, one for a microwave transmission and the other for signal detection [1]. In contrast to Ref. [1], the utilization of a microstrip antenna as a transmitter enhanced a capability of wide-band operation. The replacement of conventional capacitors with varactor diodes makes resonance condition easily reproducible without any mechanical action during tuning and matching procedure since the capacitance of the diodes is controlled electronically. The operation of the new EPR spectrometer was tested by measuring a signal of 1,1-diphenil-2-picrylhydrazyl (DPPH) sample in the frequency range of 0.8-2.5 GHz.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.11a
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• pp.139-142
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• 2002

본 논문에서는 기존의 MSA의 구조를 변형하여 용량을 장하한 변형된 MSA구조와 S자형 변형된 MSA 구조를 제안했다. 용량을 장하한 변형된 MSA는 전기력선 형성에 제한 받지 않도록 방사패치와 접지면을 접어 올린 좌ㆍ우측 평행 평판과 방사패치 사이 용량을 장하하고, S자형 변형된 MSA는 방사패치쪽과 그라운드판쪽에 용량을 장하하여 설계ㆍ제작하였다. 설계된 안테나는 2.24GHz의 중심 주파수에서 S자형 변형된 MSA가 5.7%의 대역폭을 갖고, 용량을 장하한 변형된 MSA가 8.71%의 대역폭으로 용량을 장하한 변형된 MSA가 광대역 안테나임을 확인하였다. 또한 제작된 S자형 변형된 MSA의 방사 패턴 특성은 E면과 H면의 수직ㆍ수평 편파의 특성을 측정하여 비교하였다.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.2
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• pp.18-28
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• 1989

In this paper, we describe a pointing accuracy establishment and efficiency measurement of 13.7 m antenna for observing cosmic radio wave which is in the first stage just after finishing its installation. The initial stage of pointing model, 1 and 2 were set up with the observational data of Sun and Moon which are large in visual diameter and also strong in radio intensity. Based on this model, model 3 and 4 were established within the available operational range, i.e., 3.8" in azimuth deviation, 10.5" in elevation deviation, with the observational data of SiO maser source which is a point source and distributed in overall sky. Both apeture efficiency anhd beam efficiency were measured by observing Venus whose brightness temperature is well-known. The resulting corrected efficiencies were 35% and 50% respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.4
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• pp.491-498
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• 1998

Based on FDTD(Finite-Difference Time-Domain) method the human head absorbed power radiated from a 1.8 GHz portable phone is computed. For this computation the 7 layered media for the human head modeling and the monopole antenna attached to metallic box for the portable phone are used. To reflect the real circumstances typical sizes of human heads and portable phones are considered in the calculation. The length of monopole antenna is 4.5 cm. Under the predetermined model the distribution of SAR over the human head are calculated, and from which the place of maximum SAR is near the head skin surface, not deep places far into the head. The computation shows the maximum SAR to be 1.4 mWg somewhat less than the internationally adopted value of 1.6 mW/g.

• Journal of electromagnetic engineering and science
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• v.12 no.4
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• pp.234-239
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• 2012

This paper presents a compact K-band Doppler radar sensor for human vital signal detection that uses a radar configuration with only single coupler. The proposed radar front-end configuration can reduce the chip size and the additional RF power loss. The radar front-end IC is composed of a Lange coupler, VCO, and single balanced mixer. The oscillation frequency of the VCO is from 27.3 to 27.8 GHz. The phase noise of the VCO is -91.2 dBc/Hz at a 1 MHz offset frequency, and the output power is -4.8 dBm. The conversion gain of the mixer is about 11 dB. The chip size is $0.89{\times}1.47mm^2$. The compact Ka-band Doppler radar system was developed in order to demonstrate remote human vital signal detection. The radar system consists of a Ka-band Doppler radar module with a $2{\times}2$ patch array antenna, baseband signal conditioning block, DAQ system, and signal processing program. The front-end module size is $2.5{\times}2.5cm^2$. The proposed radar sensor can properly capture a human heartbeat and respiration rate at the distance of 50 cm.

• Proceedings of the KSRS Conference
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• v.2
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• pp.1007-1010
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• 2006

This study investigates the spatial structure of the total cloud liquid water content Q fields over the Northwest Pacific Ocean during winter monsoon. The distributions of Q have been estimated from the brightness temperatures of the ocean - atmosphere system $T_B(f)$, where f is frequency, measured by AQUA AMSR-E in January -March 2003. Marine strati (St) and stratocumuli (Sc) are typical for winter monsoon season. They were analysed using mainly high-frequency channel at f = 36.5 GHz, vertical polarisation. $T_B$ data were accompanied by the data on near surface wind speed, air temperature and humidity from the nearest meteorological stations. Tow one-dimensional spectra were computed for downwind and crosswind sections of Q fields. The AMSR-E antenna field of view (14-8 km) and the cloud field sizes (100-1000 km) restricted the spatial scales. The results of case study Jan 31 2003 are presented. Scale-invariant spectrum is typical. In the cases of extended St levels a spectral slope equals about -1.7, conforming to classical -5/3 of turbulence theory. For Sc cases the absolute magnitude of spectral slope is rather higher, as a rule. The value is about -2. In the case when cloud streets are presented, a strait line form of spectrum is less reliable with a slope being rather lower (about -1.4).

• Journal of Satellite, Information and Communications
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• v.1 no.2
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• pp.8-15
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• 2006

Under Resolution 122 (Rev. WRC-03), ITU-R is invited to study, as a matter of urgency, power limitations applicable for HAPS ground stations to facilitate sharing with space station receivers in the bands 47.2-47.5 GHz and 47.9-48.2 GHz. However, there have been no studies on this issue. Recommendation ITU-R SF.1481-1 which was developed during past study period, provides methodology and system characteristics for analyzing the sharing feasibility between systems in the FS using HAPS and systems in the FSS. System characteristics for a typical HAPS in the bands above are also given in Recommendation ITU-R F.1500. This paper provides the results on power limitations applicable for HAPS ground stations in accordance with Resolution 122 (Rev. WRC-03). As already shown in ITU-R Recommendation the results show that a sufficient separation distance is required for sharing between HAPS ground stations and FSS satellite systems. We obtain some examples of the sharing conditions considering reducing the power level of HAPS ground stations and using the antenna beam pattern with the low sidelobe to decrease the interference level affecting FSS satellite receiver.