• Journal of the Korean Society for Railway
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• v.18 no.2
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• pp.105-110
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• 2015

This paper presents a $4{\times}1$ beam-forming reader antenna system for a new type of RFID based train position detection technology. The required beamwidth of the reader antenna is analytically expressed for different train speeds. The proposed antenna system consists of four rectangular patch elements and two switching couplers which are designed, without any impedance matching networks, for two different antenna modes. The switching coupler is a rectangular quadrature coupler with Pin diodes connecting its center line and the ground plane. The beamwidth of the antenna when the diodes are off and on is $18^{\circ}$ and $39^{\circ}$, respectively. The proposed antenna system will be used for a real train test in the near future.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.648-650
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• 2015

In this research, we investigate an influence of a reader antenna location in Passive UHF RFID system based Object localization. When the localization system uses stationary RFID reader system, the performances of the system are significantly varied depending on the deployed antenna conditions due to its external environment such as reflection by the ground and obstacles. In this research we deeply study the RF conditions and differentiation with various antenna location. According to the empirical results, the localization system shows the best performance, where the reader antenna locates 1.5m from the target area of interest.

• The Journal of the Korea Contents Association
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• v.9 no.10
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• pp.40-50
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• 2009

Incorrect deployment of RFID readers occurs reader-to-reader interferences in many applications using RFID technologies. Reader-to-reader interference occurs when a reader transmits a signal that interferes with the operation of another reader, thus preventing the second reader from communicating with tags in its interrogation zone. Interference detected by one reader and caused by another reader is referred to as a reader collision. In RFID systems, the reader collision problem is considered to be the bottleneck for the system throughput and reading efficiency. In this paper, we propose a novel RFID reader anti-collision algorithm based on evolutionary algorithm(EA). First, we analyze characteristics of RFID antennas and build database. Also, we propose EA encoding algorithm, fitness algorithm and genetic operators to deploy antennas efficiently. To show superiority of our proposed algorithm, we simulated our proposed algorithm. In the result, our proposed algorithm obtains 95.45% coverage rate and 10.29% interference rate after about 100 generations.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.1
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• pp.23-30
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• 2010

In this paper, a design for the 900MHz bandwidth RFID reader antenna with circular polarization is proposed and experimentally investigated. The 900MHz bandwidth RFID reader antenna is proposed as a simple radiator with loading capacitor to generate LHCP(Left Hand Circular Polarization). Also, the design and fabrication of antenna has the returnloss of -32.28dB at the center frequency of 1010MHz and Bandwidth of 12.5% at 905Hz~1030MHz. Proposed LHCP antenna of maximum gain is 6dBi and satisfy axial ratio based on 2. From the measured result, axial ratios based on 2 are observed at the operating frequencies. The proposed antenna is suitable for RFID applications in wireless communications.

• Proceedings of the Korea Contents Association Conference
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• 2009.05a
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• pp.715-719
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• 2009

Incorrect deployment of RFID readers occurs reader-to-reader interferences in many applications using RFID technologies. Reader-to-reader interference occurs when a reader transmits a signal that interferes with the operation of another reader, thus preventing the second reader from communicating with tags in its interrogation zone. Interference detected by one reader and caused by another reader is referred to as a reader collision. In RFID systems, the reader collision problem is considered to be the bottleneck for the system throughput and reading efficiency. In this paper, we propose a novel RFID reader anti-collision algorithm based on evolutionary algorithm(EA). First, we analyze characteristics of RFID antennas and build database. Also, we propose EA encoding algorithm, fitness algorithm and genetic operators to deploy antennas efficiently. To show superiority of our proposed algorithm, we simulated our proposed algorithm. In the result, our proposed algorithm obtains 95.45% coverage rate and 10.29% interference rate after about 100 generations.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.11
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• pp.1211-1216
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• 2007

Yagi-Uda UHF RFID(Radio Frequency Identification) tag antennas with long reading range have been designed. According to ISO-18000, EIRP(Effective Isotropic Radiation Power) of reader and reader antenna is limited as 36 dBm. Therefore, the gain of a tag antenna should be high enough to extend the reading range. Yagi-Uda antenna has been applied to a UHF RFID tag antenna, and high gain and long reading range have been achieved. Three different of Yagi-Uda UHF antennas have been optimized to achieve the small size with low back-lobe patterns. The sizes, reading ranges and return loss of Yagi-Uda tag antennas are compared and measured.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1585_1586
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• 2009

본 논문에서는 다구찌 기법을 사용하여 최적설계 한 중심 주파수가 920MHz인 휴대용 RFID 리더안테나를 제안한다. 제안한 안테나는 모서리가 절단되고 정사각형 마이크로스트립 패치에 네 변으로부터 슬롯을 갖는 구조이다. 이러한 슬롯구조는 마이크로스트립 패치안테나를 소형화 시킬 수 있으며, 슬롯이 없는 구조에 비해서 약 18%의 안테나 크기 감소가 가능함을 실험을 통해 확인 하였다. 슬롯의 구조를 갖게 되는 소형의 안테나는 복잡한 설계변수에 따라 변화하므로 최적의 안테나 설계를 위해서는 해석 및 시험단계에 수많은 반복이 요구된다. 본 연구에서는 해석 및 실험 횟수를 최소화할 수 있는 실험계획법인 다구찌법의 직교배열 표를 도입하여 설계할 때의 주요 요소들의 민감도 해석을 수행하고 그 영향성을 분석하여 해석결과를 바탕으로 설계반복을 최소화 하면서 최적의 구조를 갖는 안테나를 설계 하였으며 유전율이 4.4이고, 두께가 3.2mm 인 Epoxy 1.6T의 기판상에 제작한 안테나 특성에 대한 실험 결과를 제시하였다.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.3
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• pp.23-30
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• 2012

In this paper, we propose a new near-field reader antenna for 900 MHz RFID. The proposed antenna consists the micro-strip antenna with the periodic structure. The overall dimension of the antenna is $313mm{\times}152mm{\times}14mm$. The antenna has the uniform E-field distribution in near field region and the heart-shaped radiation beam pattern (Peak gain=-2 dBi). The transmitted power range is from 17 dBm to 23 dBm. We focus on minimizing the detected error by suppressing the reflected power from the metal, which is attached to the surface by tag, and by reducing the transmitted power from tag.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.6 no.3
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• pp.101-110
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• 2007

This study has designed a circular polarization antenna for UHF bandwidth RFID reader. As a result of performance test of the antenna designed it is found that return loss (S11) is about -45.529dB at 914MHz, which is relatively small, and antenna gain is about 6.09dBi. It has also been confirmed that $50{\Omega}$ impedance matching is about $50.48{$\Omega}$ and it can be applied to every RFID reader. Therefore, the antenna is designed to have higher gain of circular polarization by improving reception, which is one of the most important parameters of RFID reader and is expected to be extensively used to recognize multi-tag in the distance.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.1 s.343
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• pp.1-8
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• 2006

In this paper, we suggested a new antenna structure for the RFID(Radio Frequency IDentification) reader. The conventional RFID reader uses a loop antenna. The central area of a loop antenna shows a low magnetic field strength, especially for the case of a large loop antenna diameter. We proposed a parallel-fed multiple loop antenna. Simulation and measurement were carried out for a single loop antenna, series-fed and parallel-fed multiple loop antennas. Simulation results show that we can obtain 0.40A/m, 0.68A/m, 1.98A/m of magnetic field strengths at the central point of a reader antenna for a single loop antenna, series-fed and parallel-fed multiple loop antennas, respectively. We measured the $79mm{\time}48mm$ tag area averaged induced voltages with applying 20Vp-p same source signals to reader antennas through the resistors. Measured tag area averaged induced voltages at the central point of a reader antennas were 0.76V, 1.45V, 4.04V for a single loop antenna series-fed and parallel-fed multiple loop antennas, respectively. The results show that we can get high induced voltage which can grantee a longer reading distance with a proposed parallel-fed multiple loop antenna.