• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.7
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• pp.1509-1513
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• 2009

A semicircle antenna is presented for wideband communication system. The proposed antenna radiates linear polarized wave omnidirectionally in wide frequency band from 1.5 GHz to more than 5 GHz (110%). The frequency bands of the proposed antenna are investigated from the variable current path lengths by tilting angles. The overall radiation gain of the proposed antenna is 2-3 dBi.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.338-338
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• 2012

사파이어 ($Al_2O_3$)는 높은 밴드갭 에너지 (~19.5 eV)를 가진 물질로서 우수한 내마모성, 강도, 전기 절연성 및 안정한 화학적 특성을 갖고 발광다이오드 기판, 보석재료 등 각종 산업 및 기술적 분야에서 널리 사용되고 있다. 특히, 플립칩 발광다이오드 구조의 경우 광추출효율을 향상시키기 위해 높은 투과도를 갖는 사파이어 기판이 요구되어 왔으며, 지금까지 건식/습식식각방법을 이용한 사파이어 표면에 마이크로 크기의 심한 거칠기 또는 요철이 형성된 나노크기의 격자구조를 형성시키는 연구가 진행되어 오고 있다. 그 중, 나노 크기의 격자구조는 공기에서 반도체 기판까지 선형적인 유효굴절률 분포를 갖기 때문에 표면에서 생기는 Fresnel 반사 손실을 줄일 수 있다. 이러한 구조를 형성하기 위해서는 식각 마스크가 필요한데, 형성 방법으로 레이저 간섭 리소그래피, 전자빔 리소그래피, 나노임프린트 리소그래피 등이 있으나, 비싼 가격과 복잡한 공정 절차 등의 단점을 지니고 있다. 따라서 본 연구에서는 식각 마스크 패턴을 위해, 보다 저렴하고 간단한 실리카 나노구 및 열적응집 금 나노 입자를 이용하였다. 양면 폴리싱 c-plane 사파이어 기판을 사용하였고, 단일 층의 주기적인 실리카 나노구를 기판 표면에 스핀코팅에 의해 도포한 후 유도결합플라즈마 식각 장비를 이용하여 식각하여 주기적인 패턴을 갖는 렌즈모양의 격자구조를 형성하였다. 그리고 주기적으로 형성된 격자 위에 열 증착기를 이용하여 금 박막을 증착한 후 급속열적어닐닝(rapid thermal annealing)을 이용하여 열처리함으로써 비주기적인 금 나노입자를 형성시켰다. 형성된 금 나노패턴을 이용하여 동일한 조건으로 식각함으로써 광대역 및 전방향성 높은 투과도를 갖는 원뿔 모양의 사파이어 나노구조를 제작하였다. 제작된 샘플의 패턴 및 식각 형상은 전자현미경을 사용하여 관찰하였으며, UV-vis-NIR 분광광도계 (spectrophotometer)를 사용하여 투과율을 측정하였다. 렌즈 모양 표면 위에 원뿔모양의 나노구조를 갖는 사파이어 기판은 일반적인 사파이어 기판보다 향상된 투과율 특성을 보였다.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.13 no.1
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• pp.61-66
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• 2014

This paper describes the design, fabrication, and measurement of a compact hexa-band coupling antenna for 4G mobile handset using a small element with two slots. In order to obtain sufficient bandwidth (LTE700, GSM850, GSM900, GSM1800, GSM1900, UMTS) with a Voltage Standing Wave Ratio $(VSWR){\leq}3:1$, two slots are inserted in the small element, and coupling patch is used. The measured result of the fabricated antenna provides 410MHz bandwidth form 0.688 to 1.098GHz and 643 MHz bandwidth form 1.607 to 2.250GHz (${\leq}VSWR 3:1$) with the gain ranging from -0.52 to 4.68 dBi. Also, a good radiation pattern is achieved within the hexa-band (0.698-0.960GHz and 1.710-2.170GHz) range.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.5
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• pp.206-213
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• 2015

An omni-directional, graded-index and textured ZnO nanorods with $MgF_2$ anti-reflective(AR) coating films for the electro optical tracking system(EOTS) by e-beam evaporation method are presented. we achieved that the graded index structure can minimize image tracking interference of EOTS which is comparable to a general AR coating films. Optimized ZnO nanorods with $MgF_2$ AR coating films lead to decreasing Fresnel reflection by gradient refractive index. According to our experiment results, ZnO nanorods with $MgF_2$ AR coating films can be used for various electro optical system to improve the optical performance.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.6 s.97
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• pp.632-643
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• 2005

This paper presents a folded stripline-fed small broadband disk-loaded monopole antenna with vertical ground plane. The bandwidth of the proposed antenna can be enhanced by electromagnetic coupling between the shorted rectangular disk and the probe with folded strip line. The measured impedance bandwidth of the proposed antenna is $37.6\%$ for $VSWR\leq2$ with the center frequency at 2.313 GHz and has the physical dimensions of only $11mm\times11mm\times11mm$ which corresponds to the electrical length of $0.085\lambda_0\times0.085\lambda_0\times0.085\lambda_0$. For improving the radiation pattern characteristics, rectangular slits are inserted in the vertical ground plane. Rectangular slits affect the currents distribution on the ground plane, so that the antenna radiation in the direction of the ground plane is reduced more than 3 dBi. Gain of the antenna is approximately 2.6 dBi within the bandwidth.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.9
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• pp.987-992
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• 2015

In this paper, neutralization line structure have been employed to improve the isolation between the MIMO antenna system. The proposed MIMO antenna size is $116mm{\times}64mm{\times}5mm$ and designed on FR-4(${\varepsilon}r=4.4$) ground substrate. Neutralization line was applied to enhance isolation between the each antenna elements. The fabricated antenna satisfied a VSWR below 3 in LTE band B13 and the isolation between the MIMO antenna system is presented below -15dB. On the H-plane, antenna shows an omnidirectional pattern. In LTE band B13, the antenna presents a gain of a -2.6dBi ~-1.18dBi and radiation efficiency of 33.49% ~ 46.45%. Comparing measurement result with the outcome of simulation, the proposed MIMO antenna is expected to be applied for mobile application.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.11
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• pp.91-96
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• 2010

In this paper, an internal USB dongle antenna with a circular hook-shaped patch is proposed. The proposed antenna comprises of a circular hook-shaped patch and a monopole stub. The proposed antenna with the dimension of $10mm{\times}50mm{\times}0.8mm$ was fabricated on commercial FR-4 substrate with a dielectric constant of 4.6 and tangent loss of 0.025. The designed antenna exhibits three different resonant bandwidths, 2.4 GHz-2.5 GHz, 3.4 GHz-3.6 GHz, and 5.15 GHz-5.825 GHz. The measured radiation patterns are omni-directional at measured frequencies. Therefore, the proposed antenna is suitable for wireless USB dongle antenna that can support multiband wireless services such as WLAN, WiMAX and Bluetooth.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.5
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• pp.475-483
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• 2013

In this paper, a coupled-fed monopole antenna for LTE/WWAN mobile handset applications is presented. The antenna consists of a monopole, a coupling strip, a feeding pad, a stub, and a shorting strip. The basic resonance of the monopole combines with the resonance formed by the coupling that occurs between the coupling strip and the feeding pad to include LTE700(698~787 MHz), GSM850(824~894 MHz), and GSM900(890~960 MHz) bands. The resonance of the stub combines with the harmonics of the monopole to include GSM1800(1,710~1,880 MHz), GSM1900(1,850~1,990 MHz), and UMTS(1,920~2,170 MHz) bands. Therefore, the proposed antenna is suitable as antenna for hexa-band mobile handset applications, covering LTE700, GSM850, GSM900, GSM1800, GSM1900, and UMTS bands. A stable and omni-directional radiation pattern with reasonable gains is observed within the operating bandwidth.

• Journal of Satellite, Information and Communications
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• v.12 no.1
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• pp.94-100
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• 2017

In this paper, we suggest a design method of a metamaterial-based low-profile antenna working at 425 MHz for LEO/Cube satellites. Satellites play an important role in linking th remote nodes in a wireless communication network and covering wide areas of the globe. Especially, an increasing number of universities or individuals aspire having their own satellites and build low-budget structures such as cube satellites in LEO and the ways to reduce the sizes of their satellites. Since the antenna occupies a major portion of the satellite surface, the antenna should be miniaturized for lighter weight. The proposed metamaterial low-profile antenna, unlike the conventional patch antenna, produces such a zeroth-order resonance to create an omnidirectional radiation pattern. Also, it is connected to a UHF waveguide bandpass filter as the feeding system to examine the possible change in the situation that the antenna is combined with the system. The performances of the monopole and proposed metamaterial antennas are compared to one another.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.2
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• pp.75-79
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• 2015

In this paper, a dual band antenna with the operating frequency in HF and UHF band was proposed. The antenna structure consists of three spiral turns coil in the bottom side to generate the HF frequency of 13.56 MHz. In the top of the antenna, an inverted-spiral dipole structure is used to create the UHF frequency of 922 MHz. The dual band antenna was optimized to reduce size with $80mm{\times}40mm{\times}0.8mm$ dimension. The antenna presents the omnidirectional characteristic with high gain. To validate the theoretical design, the antenna was simulated using FR-4 substrate and verified the simulation results.