• 한국전자파학회논문지
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• 제22권12호
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• pp.1184-1187
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• 2011

본 논문에서는 이중 대역 저지 기능을 갖는 평판형 모노폴 UWB 안테나를 제안하였다. 제안된 안테나의 대역 저지 특성은 패치 상의 1차와 3차의 힐버트 곡선 슬롯들에 의하여 구현되었다. 각 힐버트 곡선 슬롯의 크기를 조절함으로써, 3.3에서 3.7 GHz 그리고 5.3에서 6 GHz에 걸친 저지 대역을 쉽게 구현할 수 있었다. 제작된 안테나의 VSWR과 방사 패턴을 측정하였으며, 이 결과로부터 설계된 안테나가 UWB 통신에서 사용될 수 있음을 알 수 있었다.

• ETRI Journal
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• 제35권3호
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• pp.534-537
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• 2013

A compact monopole antenna excited by a conductor-backed coplanar waveguide (CBCPW) is developed for wireless USB dongle applications. The proposed antenna has a compact dimension of $14mm{\times}47.4mm{\times}3.5mm$, which is suitable for a USB dongle housing. A slotted elliptical patch and a CBCPW with vertical vias are employed to achieve a further size reduction and an improved impedance bandwidth. The measurement result demonstrates that the fabricated antenna resonates from 2.25 GHz to 10.9 GHz, which covers all of the important wireless communication bands, including WiBro (2.3 GHz to 2.4 GHz), Bluetooth (2.4 GHz to 2.484 GHz), WiMAX (2.5 GHz to 2.7 GHz and 3.4 GHz to 3.6 GHz), satellite DMB (2.605 GHz to 2.655 GHz), 802.11b/g/a WLAN (2.4 GHz to 2.485 GHz and 5.15 GHz to 5.825 GHz), and ultra-wideband (3.1 GHz to 10.6 GHz) services. The radiation characteristics of the proposed antenna when attached to a laptop are tested to investigate the influence of the keypad and the LCD panel of the laptop.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.820-824
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• 2004

Personal Robot System in developing, have a module architecture, each module are connected through heterogeneors network systems like Ethernet, WLAN (802.11), IEEE1394 (Firewire), Bluetooth, USB, CAN, or RS-232C. In developing personal robot system we think that the key of robot performance is interoperability among modules. Each network protocol are well connected in the view of network system for the interoperability. So we make a bridging architecture that can routing, converting, transporting data packets with matcing each network's properties. Furthermore we suggest a advanced design scheme for realtime / non-realtime and control signal (short, requiring hard-realtime) / multimedia data (large, requiring soft-realtime). By some application systems, we could test performance, interoperability and stability. In this paper, we show our design concept, middleware architecture, and some applications systems using this middleware.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2005년도 추계종합학술대회
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• pp.261-264
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• 2005

This paper presents the design of a down-conversion mixer with built-in active balun integrated in a $0.25\;{\mu}m$ pHEMT process. The active balun consists of series-connected common-gate FET and common-source FET. The designed balun achieved broadband characteristics by optimizing gate-width and bias condition for the reduction in parasitic effect. From DC to more than 6GHz, the active balun shows the phase error of less than 3 degree and the gain error of less than 0.4 dB. A single-balanced down-conversion mixer with built-in broadband active balun has been designed with optimum width, load resistor and bias for conversion gain and without any matching component for broadband operating. The designed mixer whose size of including on-chip bias circuit is $1\;mm{\times}1\;mm$ shows the conversion gain of better than 7 dB from 2 GHz to 6 GHz and $P_{1dB}$ of -10 dBm at 5.8 GHz

• 제어로봇시스템학회논문지
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• 제21권4호
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• pp.378-384
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• 2015

Indoor localization is becoming one of the most important technologies for smart mobile applications with different requirements from conventional outdoor location estimation algorithms. Fingerprinting location estimation techniques based on neural networks have gained increasing attention from academia due to their good generalization properties. In this paper, we propose a novel location estimation algorithm based on an ensemble of multiple neural networks. The neural network ensemble has drawn much attention in various areas where one neural network fails to resolve and classify the given data due to its' inaccuracy, incompleteness, and ambiguity. To the best of our knowledge, this work is the first to enhance the location estimation accuracy in indoor wireless environments based on a neural network ensemble using fingerprinting training data. To evaluate the effectiveness of our proposed location estimation method, we conduct the numerical experiments using the TGn channel model that was developed by the 802.11n task group for evaluating high capacity WLAN technologies in indoor environments with multiple transmit and multiple receive antennas. The numerical results show that the proposed method based on the NNE technique outperforms the conventional methods and achieves very accurate estimation results even in environments with a low number of APs.

• Journal of Electrical Engineering and Technology
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• 제12권4호
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• pp.1611-1618
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• 2017

This paper presents a compact reconfigurable printed monopole antenna, operating in three different frequency bands (2.45 GHz, 3 GHz and 5.2 GHz), depending upon the state of the lumped element switch. The proposed multiband reconfigurable antenna is designed and fabricated on a 1.6 mm thicker FR-4 substrate having a relative permittivity of 4.4. When the switch is turned ON, the antenna operates in a dual band frequency mode, i.e. WiFi at 2.45 GHz (2.06-3.14 GHz) and WLAN at 5.4 GHz (5.11-5.66 GHz). When the switch is turned OFF, it operates only at 3 GHz (2.44-3.66 GHz). The antenna radiates omni-directionally in these bands with an adequate, bandwidth (>10 %), efficiency (>90 %), gain (>1.2 dB), directivity (>1.7 dBi) and VSWR (<2). The fabricated antenna is tested in the laboratory to validate the simulated results. The antenna, due to its reasonably compact size ($39{\times}37mm^2$), can be used in portable devices such as laptops and iPads.

• 한국항행학회논문지
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• 제13권5호
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• pp.714-719
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• 2009

본 논문에서는 Ultra-Wideband(UWB) 통신을 위한 새로운 저지대역 안테나를 설계하였다. 설계된 안테나는 광대역 특성을 가지며, IEEE 802.11a와 HIPERLAN/2에 의해 사용이 제한된 5.15~5.825GHz에서 주파수 대역 저지 특성을 갖는다. 광대역 특성을 얻기 위하여 부분 그라운드와 notch cut 구조를 사용하였고 저지 대역 특성을 얻기 위해 패치면에 U-slot을 삽입하였다. 설계된 안테나는 4.90~5.92GHz 대역을 저지하며 3.1~10.6GHz 대역에서 정재파비 2이하를 만족하는 광대역 특성을 나타낸다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권8호
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• pp.3657-3682
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• 2018

This paper presents a Bluetooth and pedestrian dead reckoning (PDR)-based indoor fusion localization approach (BtPDR) using smartphones. A Bluetooth and PDR-based indoor fusion localization approach can localize the initial position of a smartphone with the received signal strength (RSS) of Bluetooth. While a smartphone is moving, BtPDR can track its position by fusing the localization results of PDR and Bluetooth RSS. In addition, BtPDR can adaptively modify the parameters of PDR. The contributions of BtPDR include: a Bluetooth RSS-based Probabilistic Voting (BRPV) localization mechanism, a probabilistic voting-based Bluetooth RSS and PDR fusion method, and a heuristic search approach for reducing the complexity of BRPV. The experiment results in a real scene show that the average positioning error is < 2m, which is considered adequate for indoor location-based service applications. Moreover, compared to the traditional PDR method, BtPDR improves the location accuracy by 42.6%, on average. Compared to state-of-the-art Wireless Local Area Network (WLAN) fingerprint + PDR-based fusion indoor localization approaches, BtPDR has better positioning accuracy and does not need the same offline workload as a fingerprint algorithm.

• 한국정보통신학회논문지
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• 제9권8호
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• pp.1676-1682
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• 2005

IEEE 802.11 MAC 프로토콜의 PCF(Point Coordination Function)는 일반적으로 부하가 높은 네트워크에서 DCF 보다 더 나은 성능을 보이는 매체 접근 방식이다. 뿐 만 아니라 PCF는 시간 제한적인 응용의 전송에 적절하다. 본 논문에서는 IEEE 802.11 무선 랜에서 노드의 수 변화에 따르는 QoS 향상 방법에 대하여 고려한다. 무선 랜에는 QoS를 자원 받는 노드들과 그렇지 않은 노드들도 구성되어 있다고 가정한다 여기서 QoS 노드란 QoS를 지원하는 메커니즘을 가지는 노드를 의미한다. 본 논문에서는 많은 시뮬레이션을 통하여 네트워크의 적절한 파라미터들을 구하며, 노드의 수가 변함에 따르는 네트워크 현상에 대하여 고찰이 이루어진다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2005년도 추계종합학술대회
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• pp.589-592
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• 2005

미래의 유비쿼터스 환경은 사용자에게 보장된 품질로서 유용한 서비스를 제공하기 위해 여러 가지의 무선통신 시스템들과 다른 엑세스 기술들로 인한 다수의 연결성 대안들을 제시해야 한다. 새로운 어플리케이션들은 시간과 장소에 제한 없이 다른 휴대용 디바이스들로부터 정보를 엑세스할 수 있는 유비쿼터스 환경을 요구함으로써 셀룰러망, WLNA, 그리고 MANET 등과 같은 다양한 무선 플랫폼들을 통합하도록 한다. 다른 성능과 기능을 갖는 기술들의 통합은 매우 복잡하며, 프로토콜 스택의 모든 계층에 대해 이슈화된다. 이 논문에서는 SDR 기반 무선 통합망을 위한 연결성 대안 및 네트워크 계층에서의 통합 아키텍쳐를 비교 검토한다.