• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.39A no.2
• /
• pp.77-85
• /
• 2014

Recently, utilization of MIMO(Multi-Input Multi-Output) system using array antennas is evaluated significantly according to the extension of high-capacity and high-speed communication services. However, MIMO system has disadvantages such as high-complexity and high-power-consumption, because RF(Radio Frequency) chain is required as antenna number, and several array antenna is used in conventional MIMO system. In order to solve these problems, research about beamspace MIMO system using ESPAR(Electronically Steerable Parasitic Array Radiator) antenna that has single RF chain by using one active antenna and several parasitic elements has been studied actively. Beamspace MIMO system using ESPAR antenna is possible to solve the problems of conventional MIMO system, because this system is composed by single RF chain. In this paper, in order to improve the system security, chaos communication algorithm that has characteristics such as non-periodic, non-predictability, easy implementation and initial condition is applied to QPSK (Quadrature Phase Shift Keying) modulated beamspace MIMO system. We design the chaos QPSK modulated beamspace MIMO system, and evaluate SER performance of this system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.15 no.9
• /
• pp.872-879
• /
• 2004

The TX/RX broadband L-type circular polarization antenna using LTCC(Low Temperature Co-fired Ceramic) for satellite communication at K, Ka band(20～21 GHz/30～31 GHz) has been presented. This antenna has been analyzed in compensation for LTCC with relative permittivity 5.2 and could have been integrated with RF component. Also antennas on LTCC enable :o reduce loss of RF system due to integrate with RF circuits and to light weight, and thus, generally one can reduce size of the RF system. As the geometry of this antenna presented is made simple by L type of monopole antenna, it is easily manufactured by LTCC progress and enables to reduce loss.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.3 no.1 s.4
• /
• pp.21-30
• /
• 2004

This paper describes the design of RF link between RSE and OBU of ETCS and the analysis of the antenna beam pattern to get a proper communication area in the cross direction and traveling direction of lanes. This stage should be performed prior to determination of system requirements of ITS service based on active DSRC. This study is important and fundamental technical analysis to design and implement base station of ETCS.

• Nuclear Engineering and Technology
• /
• v.34 no.3
• /
• pp.211-217
• /
• 2002

A 1-MW vacuum feedthrough for the KSTAR ICRF antenna is fabricated and high power RF test is performed. It is designed to have two alumina $(Al_2O_3)$ ceramic cylinders and O-ring seal instead of a brazed seal for good mechanical and thermal strength, which is important in long pulse or steady state operation. For cooling of the ceramics, dry air is circulated in a space between the two cylinders and the outer conductor. Independent cooling water channels are installed to cool the inner conductor of the feedthrough. RF high voltage test is performed using two kinds of ceramics with the purities of 99.7% and 97%. Stable operation is possible with the RF voltage of 30 kVp at long pulse of 300 sec without any severe damage.

• Journal of Advanced Navigation Technology
• /
• v.28 no.2
• /
• pp.225-231
• /
• 2024

In this article, a new approach is presented to improve the unchangeable function of a ready-made millimeter-wave antenna system. By designing a metamaterial surface appropriate for the given geometry and fixed electrical characteristics of the device, the properties of the radiated fields of the RF product are changed to have directivity and higher antenna gain. Unlike other designs using periodic metamaterials for a single patch, an aperiodic metasurface is developed to handle two patches. For a higher received signal strength and a longer RF path in the 24 GHz-radio link, an aperiodic metasurface enhances the radiated fields by 10 dB.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.33A no.6
• /
• pp.99-107
• /
• 1996

When GPS (global positioning system) is used as synchronous signal in CDMA digital cellular base station system and high speed digital synchronous communication network, antenna cable length is increased, comparing with other GPS application such as positioning or car navigation. In this paper, it is proposed that a type of new GPS antenna system including RF stage for reduction of cable loss in case of long cable.The antenna system with TMPA(truncated-corners microstrip patch antenna) is designed and fabricated because GPS signal has RHCP (right-hand circular polarization), consequently antenna size can be made small size. LNA (low noise amplifier) is designed by using HEMT(high electron mobility transistor)which has lower noise figurae and better AGC characteristics at low voltage than GaAs FET, and we equiped mixer, in GPS antenna unit, which converts from 1575.42MHz to 75.42MHz. As result of comparing between typical system and proposed system when cable length is 60m, 63dB, 55dB and 25dB gain are obtained for RG-316/U, RG-58C/U and RG-213/U, and better characteristics are achieved than typical system as far as cable length is longer.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.12 no.5
• /
• pp.46-51
• /
• 2013

In this paper, a dual-band antenna is proposed for the RF power harvester system as well as RFID tag. The proposed antenna operates as the passive and active RFID tag antenna in the UHF and microwave band, respectively. In addition, to charge the battery of an active RFID tag in the microwave band, it harvest the RF signal for tagging from the passive RFID tag antenna in the UHF band. The proposed antenna operates in the UHF band (917~923.5 MHz) and microwave band (2.4~2.45 GHz). In order to obtain the dual-band operation, the dipole structure and meander parasitic elements are proposed as the ${\lambda}/2$ and $1{\lambda}$ dipole antenna, respectively. The radiating dipole structure in the microwave band acts as the coupled feed for the meander parasitic elements in the UHF band. The impedance bandwidth (VSWR < 2) of the proposed antenna covers 917~923.5 MHz (UHF band) and 2.4~2.45 GHz (Microwave band). Measured total efficiencies are over 45 % in the UHF band and over 70 % in the microwave band. Peak gains are over 0.18 dBi and 2.8 dBi in the UHF and microwave band with an omni-directional radiation pattern, respectively.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
• /
• v.14 no.2
• /
• pp.55-67
• /
• 2003

본 고에서는 차세대 무선통신용 초소형 단말기 구현에서 RF 시스템의 성능 개선에 크게 기여하게 될 RF 집적형 안테나 기술 현황과 향후 발전 방향이 제시된다. 고성능을 유지하면서 초소형 RF 전치단을 실현하기 위한 능동소자와 안테나가 결합하여 복합 기능을 하는 능동 집적 안테나(AIA, Active Integrated Antenna) 기술 현황, RF 시스템 단일 패키지(RF-SOP, System On Package) 형태에 집적 가능한 안테나 및 미래의 꿈인 RF 시스템 단일 칩 (RF-SOC, System On Chip)을 향한 단일 칩 안테나 (AOC, antenna on chip) 기술 동향 등이 기술된다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.25 no.7
• /
• pp.737-746
• /
• 2014

Recently, researches about MIMO(Multi-Input Multi-Output) system are being studied actively due to high-capacity and high-speed communication. However, MIMO system has many RF(Radio Frequency) chains according to many array antennas. So, MIMO system has disadvantages such as high-complexity and high-power-consumption. Also, it is impossible to miniaturize the antenna dimension. In order to solve these problems, beamspace MIMO system using ESPAR(Electronically Steerable Parasitic Array Radiator) antenna was proposed. It is possible to reduce the complexity and the power-consumption, because it has single RF chain by using one active antenna and several parasitic elements. In this paper, in order to improve the security, for the first time, chaos communication algorithm is applied to QPSK modulated beamspace MIMO system using ESPAR antenna. We define as chaos QPSK beamspace MIMO system, and evaluate the SER performance. Also, we confirm that QPSK symbols can be made by changing the reactance values of parasitic elements, and evaluate the SER performance of this system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.24 no.10
• /
• pp.979-986
• /
• 2013

In this paper, a TVS diode which is commonly used as a ESD protector in wireless communication devices could cause antenna wireless sensitivity to decrease has been analyzed. When a smartphone doesn't have enough space to place many components, there would be its speaker near antenna area. In order to protect ESD coming through the speaker there also could be a TVS within antenna GND area. Digital audio signal which was sent to speaker and CDMA RF communication signal coupled from antenna was mixed by TVS. And this leakage current running through TVS resulted in decrease of antenna wireless sensitivity. The results of various experiments can be explained using circuit simulation. Following works will give us some insights that can reduce unwanted summation of digital and RF signal due to nonlinearity of ESD protectors.