• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.272-275
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• 2001

본 논문에서는 안테나의 위치를 원격에서 제어하고 안테나의 상태를 실시간으로 모니터링할 수 있는 안테나 구동 시스템을 설계하였다. 안테나 구동 시스템은 안테나 포시셔너와 호스트 컴퓨터에서 운용되는 종합관리 소프트웨어로 구성된다. 일반적으로 안테나 포지셔너와 호스트컴퓨터는 멀리 떨어져서 설치가되며 모뎀을 통하여 데이터를 전송하므로, 데이터의 신뢰성을 높이기 위하여 안테나 포지셔너와 호스트컴퓨터간에 주기적인 통신이 이루어지도록 설계하였으며 또한, 데이터 전송 프레임에 오류 검사 바이트를 추가하였다. 종합관리 소프트웨어는 사용자의 편리성을 높이기 위하여 윈도우즈 환경에서 운용되도록 설계하였으며 전자지도에 표시되는 위도, 경도정보를 이용하여 안테나 포지셔너의 구동명령을 계산하고, 사용된 정보를 데이터베이스에 저장할 수 있도록 설계하였다.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2001.11a
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• pp.101-105
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• 2001

본 논문에서는 전력증폭기를 슬롯이 적재된 삼각형 마이크로스트립 패치 안테나와 동일 평면의 기판에 집적화하여 전력증폭기 출력단의 제 3 고조파 튜닝을 안테나가 수행함으로써 전력효율을 향상시키는 효과에 대해 고찰하였다. 또한 실제 집적화에 따른 송\ulcorner수신 신호의 분리 문제를 위해 이중공진 특성을 이용한 inset 마이크로스트립 급전과 coax 급전의 이중급전 방식을 사용하였고, 이에 따라 두 ports 사이에 높은 격리 특성을 갖도록 능동 집적 안테나를 설계하였다. 선형성을 증대시키기 위해 제 3 고조파 튜닝 효과를 갖도록 안테나에 슬롯을 적재시켜 제 3 고조파에서 방사를 억제 구조를 갖게 함으로써 고조파 튜닝회로를 축소시킨 능동 집적 안테나를 설계, 제작하여 측정한 결과, B급 전력증폭기와 안테나를 각각 제작하여 결합한 형태보다 약 5%의 전력 효율 개선 효과를 얻을 수 있었다. 그리고 능동 집적 안테나의 큰 문제점이었던 송\ulcorner수신 분리에 대하여서도, IMT-2000 주파수 대역의 수신 port에서 송신 주파수의 신호를 -35dB 이하로 격리시키는 특성을 나타냄을 관찰할 수 있었다.

• ETRI Journal
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• v.36 no.4
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• pp.625-634
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• 2014

This paper studies a dual-hop multiple-access relay network where two independent source nodes transmit information to a common destination node with the aid of multiple single-antenna amplify-and-forward relays. Each relay node is subject to an individual power constraint. We focus on the design of distributed beamforming schemes for the relays to support the transmission rate requirements of the two sources. To this end, we first characterize the achievable rate region for this network via solving a sequence of corner point optimization problems proposed in this paper. We also develop several low-complexity suboptimal schemes in closed form. Two inner bounds of the achievable rate region are theoretically shown to be approximately optimal in two special scenarios. Finally, numerical results demonstrate the effectiveness of our proposed approaches.

• Structural Engineering and Mechanics
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• v.12 no.5
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• pp.491-506
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• 2001

In this paper, a new three-dimensional piezoelectric thin shell element containing an integrated distributed piezoelectric sensor and actuator is proposed. The distributed piezoelectric sensor layer monitors the structural shape deformation due to the direct effect and the distributed actuator layer suppresses the deflection via the converse piezoelectric effect. A finite element formulation is presented for static response of laminated shell with piezoelectric sensors/actuators. An eight-node and forty-DOF shell element is built. The performance of the shell elements is improved by reduced integration technique. The static shape control of structure is derived. The shell element is verified by calculating piezoelectric polymeric PVDF bimorph beam. The results agreed with those obtained by theoretical analysis, Tzou and Tseng (1990) and Hwang and Park (1993) fairly well. At last, the static shape control of a paraboloidal antenna is presented.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2019.05a
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• pp.300-302
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• 2019

The mast, which is the highest structure in warships, as well as merchant ships, is mainly equipped with radars and navigation lights. Especially, due to the nature of the naval vessels that operate many communication equipment, various kinds of antennas such as communication antennas and TACAN for aircraft guiding are installed in the naval mast. In addition to the complex structure of the mast itself, the installed antenna is a factor that greatly increases the RCS. Therefore, the mast technology for reducing the RCS is being developed and applied in the United States and Europe.

• Journal of IKEEE
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• v.25 no.1
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• pp.76-82
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• 2021

In this paper, the compressed sensing basic pursuit denoise algorithm adopted to synthetic aperture radar imaging is investigated to improve the object recognition. From the incomplete data sets for image processing, the compressed sensing algorithm had been integrated to recover the data before the conventional back- projection algorithm was involved to obtain the synthetic aperture radar images. This method can lead to the reduction of measurement events while scanning the objects. An ultra-wideband radar scheme using a stripmap synthetic aperture radar algorithm was utilized to detect objects hidden behind the box. The Ultra-Wideband radar system with 3.1~4.8 GHz broadband and UWB antenna were implemented to transmit and receive signal data of two conductive cylinders located inside the paper box. The results confirmed that the images can be reconstructed by using a 30% randomly selected dataset without noticeable distortion compared to the images generated by full data using the conventional back-projection algorithm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.1
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• pp.171-175
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• 2006

In this paper, we have developed a retrodirective active array operating in the 2 GHz LS band. The retrodirective array has the property of redirecting any electromagnetic wave back to the incoming direction without any priory informations. The system is integrated with phase conjugators and antenna array. Microwave phase conjugators can be implemented by microwave mixers. In this research, 2-port gate mixers using pHEMT and $1{\times}4$ monopole array have been used to achieve the retrodirectivity. The measured results have been compared with the theoretical prediction, and it has been shown that there exists a reasonable agreement between them. The monopole array can be used easily in many areas for simplicity and cost-effective property, and the retrodirective array developed in this research can be applied directly in the base station facilities for the wireless mobile communications. indoor wireless LAN and RFID transponders.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.3
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• pp.527-536
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• 2000

This paper discusses the design of self-oscillating mixer type low noise down converter using the microwave field effect transistor. The mixer is consists of local oscillator in which high stability dielectric resonator and band pass filter to get rid of spurious oscillation at intermediate frequency stage. The microstrip antenna was integrated in the same substrate which generate 12.3GHz and low noise amplifier was also added after antenna using 3 stage of high electron mobility transistors. The output frequency from the local oscillator was chosen as 11.3GHz for the Ku-band application. The measured phase noise was -804dBc/Hz at 100kHz offset frequency, and the gain was 7～12dB in frequency range from 12.0GHz to 12.7GHz. The noise figure at intermediate frequency stage was 64H. The designed model shows less conversion loss than previous diode type mixer. The proposed mixer can be used in digital satellite broadcasting and communication system and expected to use in next generation low noise block design.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.9
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• pp.955-964
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• 2010

In this paper, a compensation method of the amplitude and phase errors from the T/R(Transmit/Receive) modules in an active SAR(Synthetic Aperture Radar) system is introduced. The errors are defined and classified, and characterized by analyzing the measurement data acquired from the pilot test. To compensate these errors, a control methodology of T/R modules output is proposed. Before the compensation is applied, 16 T/R modules integrated on the active SAR antenna show the amplitude in 28.2~29.0 dBm and the phase in $101.7^{\circ}{\sim}165.2^{\circ}$. After the compensation, the amplitude and phase are distributed in 27.4~28.0 dBm and $116.1^{\circ}{\sim}120.0^{\circ}$ respectively. The antenna beam patterns generated by the array theory with the distributions are compared, and the proposed method is verified as good to apply for the active SAR system.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.5
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• pp.423-432
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• 2023

With the increasing demand for mobile devices featuring multi-touch operation, extensive research is being conducted on touch screen panel (TSP) Readout ICs (ROICs) that should possess low power consumption, compact chip size, and immunity to external noise. Therefore, this paper discusses capacitive touch sensors and their readout circuits, and it introduces research trends in various circuit designs that are robust against external noise sources. The recent state-of-the-art TSP ROICs have primarily focused on minimizing the impact of parasitic capacitance (Cp) caused by thin panel thickness. The large Cp can be effectively compensated using an area-efficient current compensator and Current Conveyor (CC), while a display noise reduction scheme utilizing a noise-antenna (NA) electrode significantly improves the signal-to-noise ratio (SNR). Based on these achievements, it is expected that future TSP ROICs will be capable of stable operation with thinner and flexible Touch Screen Panels (TSPs).