• Electronics and Telecommunications Trends
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• v.30 no.3
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• pp.84-94
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• 2015

5G와 IoT로 인한 무선 트래픽 급증에 대응하기 위해서는, 무선망 성능 및 주파수효율 향상, 신규주파수할당, 주파수 공동사용 기술 개발 등이 복합적으로 적용되어야 달성 가능하다. 그의 일환으로, LTE를 비면허 대역에 사용하려는 LTE-U(Long Term Evolution-Unlicensed)라는 새로운 패러다임의 수평적 주파수 공동사용 기술을, 이동통신에 적용하려는 시도가 진행되고 있다. LTE-A의 주파수 집성기술을 활용하여, 1차 캐리어를 면허 대역 LTE 기반으로 하고, 2차 캐리어를 비면허 대역 LTE로 묶어서 고속으로 데이터를 전송하는 기술이다. 우선적으로 5GHz 비면허 대역에 적용을 검토하고 있는데, 기존에 사용하던 Wi-Fi 및 기상레이다 등과의 공정한 공존(fair coexistence)이 가장 중요하다. 따라서 각국의 5GHz 주파수 대역 규제 현황, 공존을 위한 LBT(Listen-Before-Talk)통신 메커니즘, 표준화 현황을 살펴본다. 또한 이해 당사자인 Wi-Fi, LTE, 이용자, 기술기준의 입장을 살펴보고, 구현이슈, 지적소유권 동향 등을 검토하고, 기술적 및 정책적 대응전략을 살펴본다.

• Aerospace Engineering and Technology
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• v.4 no.1
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• pp.239-246
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• 2005

This paper analyze the hazard of electromagnetic radiation to personnel (HERP) and electromagnetic interference (EMI) by C-band tracking radar. Especially, this analysis defines the safety distance for the controlled & uncontrolled personnel from high power radiation of electromagnetic wave within the main beam of 3 degrees by C-band tracking radar. In addition to HERP, the analysis of electromagnetic interference between tracking radar and weather radar was accomplished to decide the safety distance for EMI protection.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.6
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• pp.808-815
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• 2015

For performance improving of C-band radar altimeter used in a missile system, Ku-band radar altimeter is developed. To utilize the time delay devices which are used in testing C-band radar altimeter, we proposed C-band and Ku-band frequency conversion method and implemented it as a part of missile system test equipment. In this paper we present design contents, development results and test application results of radar altimeter test equipments.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.275-277
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• 2014

본 논문에서는 다양한 주파수 튜닝이 가능한 직접변환방식을 이용한 Gm-C 능동필터 회로를 설계하였다. 설계된 필터는 집적회로를 튜닝하여 요구되는 기준주파수 및 대역폭과 이득을 만족시킬 수 있다. 필터에 사용된 OTA회로는 전달 트랜스컨덕턴스 값을 외부전압으로 제어할 수 있도록 설계하여 다양한 주파수대역에서 사용할 수 있다는 장점을 가진다. 설계된 필터는 ripple 전압을 최소화 하고 이득 값을 높일 수 있는 Elliptic 필터를 사용하였다. 집적화를 위하여 수동필터를 능동필터로 변환할 수 Gyrator 방식을 이용하였다. HSPICE 시뮬레이션 결과, 외부전압을 1.0V~1.9V까지 변화를 주었을 때 1.4MHz ~ 2.8MHz의 차단주파수의 조정이 가능하였고 소비전력은 4.5mW~20mW임을 측정하였다.

• IT SoC Magazine
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• s.4
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• pp.16-19
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• 2004

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.11
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• pp.1081-1090
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• 2013

In this paper, a C-band 10 W power amplifier with internally matched input and output matching circuit is designed and fabricated. The used power transistor for the power amplifier is GaAs pHEMT bare-chip. The wire bonding analysis considering the size of the capacitor and the position of transistor pad improves the accurate design. The matching circuit design with the package effect using EM simulation is performed. To reduce the unsymmetry of IMD3 in 2-tone measurement due to the memory effect, the bias circuit minimizing the memory effect is proposed and employed. The measured $P_{1dB}$, power gain, and power added efficiency are 39.8~40.4 dBm, 9.7~10.4 dB, and 33.4~38.0 %, respectively. Adopting the proposed bias circuit, the difference between the upper and lower IMD3 is less than 0.76 dB.

• Journal of Advanced Navigation Technology
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• v.14 no.5
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• pp.587-595
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• 2010

Spectrum sharing between wireless systems becomes a critical issue clue to emerging new technologies and spectrum shortage. Recently, IMT system has been allocated in the same frequency C band (3400-4200MHz) along with FSS services on co-primary basis which means that harmful. interference probability may be inspired. In this paper, to estimate the spectrum sharing between IMT and FSS systems, I propose the minimum separation distances as a sharing criterion of I/N=-10dB using the interference to noise ratio(I/N) received at the reference FSS earth station from IMT multiple base station. Especially, same results imply that I/N values can be greatly reduced with MMO SDMA interference mitigation technique of IMT base station so that FSS and IMT systems can co-exist in the sam e frequency with appropriate separation distance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.10
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• pp.1051-1062
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• 1992

Design of a continuous-time fifth-order OTA-C Eiliptic filter for operation at 4MHz is presented. The filter has been realize by five OTAs, eight capacitors and a buffer as an OTA-C structure. To prevent decreasing of characteristics due to the parastic capacitance of OTA and loading a buffer and a capacitor have been connected to the next of second section. As the result the frequency characteristics were found to be essentially within specifications : less than 0.2dB passband attenuation, 30dB stopband attenuation and 4Mz cut-off frequency have been obtained and the characteristic of cut-off region has been improved about 7dB compared with it of the theoretical case.

• Journal of Satellite, Information and Communications
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• v.9 no.3
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• pp.104-108
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• 2014

This paper represents the effect analysis results of surface-Icing on the UHF-band antenna for Space Launch Vehicle. In order to obtain structural model of the surface-icing, Relative Permittivity of ice at $-180^{\circ}C$ was extracted. Using this surface-Icing model, UHF-band antenna simulation and comparative analysis about the antenna parameters such as resonance frequency, reflection loss and radiation pattern were performed for each case of with or without surface-icing. Simulation results show that resonance frequency is shifted out of operation frequency due to the additional ice permittivity. This resonance frequency changes cause severe affect to the antenna performance and its radiation pattern.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.3 no.2
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• pp.31-38
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• 2010

It is difficult to design accurately the bandgap of metamaterial depending on metamaterial pattern and array configuration. In this paper, we propose a design method for the wanted bandgap frequency using any metamaterial pattern in 2 dimensional array. Metamaterial structure is consisted of periodic array. Therefore the calculation area in FDTD(finite difference time domain) method can be reduced by applying the periodic boundary condition to 2-D metamaterial array. The method for design and calculation the L and C values by using 2-D is also considered. So it can be designed more accurately and rapidly. For example, we designed metamaterial square pattern array in 5 GHz, and compared with the 1-D metamaterial pattern using analysis method in microstrip line. As a result, we found that the accuracy of this proposed method can be incresed to 14.7%.