• Journal of Communications and Networks
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• 제10권4호
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• pp.451-454
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• 2008

Ultra-wideband (UWB) radios have attracted great interest for their potential application in short-range high-data-rate wireless communications. High received signal to noise ratio and compliance with the Federal Communications Commissions (FCC) spectral mask call for judicious design of UWB pulse shapers. In this paper, even and odd order derivatives of Gaussian pulse are used respectively as base waveforms to produce two synthesized pulses. Our method can realize high efficiency of spectral utilization in terms of normalized effective signal power (NESP). The waveform design problem can be converted into linear programming problem, which can be efficiently solved. The waveform based on even order derivatives is orthogonal to the one based on odd order derivatives.

• 한국ITS학회:학술대회논문집
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• 한국ITS학회 2010년도 춘계학술대회
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• pp.53-55
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• 2010

• Journal of electromagnetic engineering and science
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• 제8권3호
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• pp.91-95
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• 2008

This paper presents a direct-conversion I/Q up-mixer block, which supports $3{\sim}5$ GHz ultra-wideband(UWB) applications. It consists of a VI converter, a double-balanced mixer, a RF amplifier, and a differential-to-single signal converter. To achieve wideband characteristics over $3{\sim}5$ GHz frequency range, the double-balanced mixer adopts a shunt-peaking load. The proposed RF amplifier can suppress unwanted common-mode input signals with high linearity. The proposed direct-conversion I/Q up-mixer block is implemented using $0.18-{\mu}m$ CMOS technology. The measured results for three channels show a power gain of $-2{\sim}-9$ dB with a gain flatness of 1dB, a maximum output power level of $-7{\sim}-14.5$ dBm, and a output return loss of more than - 8.8 dB. The current consumption of the fabricated chip is 25.2 mA from a 1.8 V power supply.

• Journal of Communications and Networks
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• 제5권4호
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• pp.374-385
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• 2003

The growing interest towards ultra-wideband (UWB) communications stems from its unique features such as baseband operation, ample multipath diversity, and the potential of enhanced user capacity. But since UWB has to overlay existing narrowband systems, multiple access has to be achieved in the presence of narrowband interference (NBI). However, existing baseband spreading codes for UWB multiple access are not flexible in handling NBI. In this paper, we introduce two novel spreading codes that not only enable baseband UWB multiple access, but also facilitate flexible NBI cancellation. We construct our codes using a single carrier or multiple carriers (SC or MC), which can be implemented with standard discrete-cosine transform (DCT) circuits. With our SC/MC codes, NBI can be avoided by simply nulling undesired digital carriers. Being digital, these SC/MC codes give rise to multiband UWB systems, without invoking analog carriers. In addition, our SC/MC codes enable full multipath diversity, and maximum coding gains. Equally attractive is their capability to reduce the number of interfering users, with simple matched filter operations. Comprehensive simulations are also carried out to corroborate our analysis.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 D
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• pp.2069-2070
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• 2006

본 논문은 UWB(Ultra Wideband) 펄스 기반의 단일 송수신을 통한 UWB 레인징 시스템에서 거리산출의 모호성을 제거하고 그 성능을 향상시키기 위한 듀얼윈도우처리기법을 새롭게 제안한다. 일반적으로 UWB 레인징시스템은 UWB 전송펄스의 높은 시간분해능을 이용하여 거리를 산출하는데, 비가역성(Non-coherent) UWB 송수신기 구조에서는 신호가 언제 수신 될지 모르는 정보 표본값들로부터 최초도착 성분을 추출하게 되고 이로 인해 거리산출오차가 크게 발생되어 진다. 실내무선채널환경(CMI)의 UWB 레인징 시뮬레이션 결과 본 논문에서 제안된 듀얼윈도우처리기술을 적용 시 1m 거리산출 확률오차기준으로 대략 98% 정확도를 보인 반면에 그렇지 않은 경우는 75%이하의 레인징 정확도 성능을 나타낸다

• Journal of electromagnetic engineering and science
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• 제9권4호
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• pp.202-210
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• 2009

In this paper, we have analyzed the effect of interference between ultra-wideband(UWB) and intelligent transport systems(ITS). The maximum possible UWB emission power and minimum possible distance between UWB devices and ITS are found. In order to analyze the interference, we employ the Monte-Carlo(MC) method. We consider six situations, which are indoor office line-of-sight(LOS), indoor office non-line-of-sight(NLOS), indoor residential LOS, indoor residential NLOS, outdoor rural LOS, and outdoor rural NLOS environments. From the simulation results, it is confirmed that coexistence between UWB and ITS devices can be realized in accordance with the emission mask of 19.3 dB for indoor application or 19.3 dB for an image system. And in the outdoors, coexistence between UWB and ITS devices can be realized if the emission mask is at least 1.6 dB for vehicles' radar systems.

• 한국통신학회:학술대회논문집
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• 한국통신학회 2006년도 하계종합학술발표회 논문 초록집
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• pp.456-456
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• 2006

• 산업기술연구
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• 제31권A호
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• pp.109-112
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• 2011

In this paper, we proposed a planar reversed triangle monopole antenna for UWB(Ultra Wideband) communication. RF-60A substrate of 0.64 mm thickness and 6.15 relative permitivity and 0.035 mm conductor of thickness and loss tangent 0.0025 is used for implementation. We have used Ansoft $HFSS^{TM}$(High Frequency Structure Simulator) to simulate the proposed antenna. The proposed antenna showed return losses about -10 dB, nearly omni-directional radiation patterns and maximum gains are over -5 dBi at the frequency band from 3.1 GHz to 10.6 GHz for ultra wide band communication.

• Journal of electromagnetic engineering and science
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• 제6권2호
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• pp.117-122
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• 2006

This paper presents the impacts of Ultra-wideband(UWB) applied in the communication applications using frequency band from 3.1 GHz to 10.6 GHz on Broadband Wireless Access(BWA) based on orthogonal frequency division multiplexing(OFDM) using frequency band of 3.5 GHz. It proposes low duty cycle(LDC) for enabling UWB to mitigate strong interference to BWA. The effects of interference mitigation are evaluated and analyzed in the environment of UWB coexistence with BWA. UWB with LDC scheme will be given to bring higher transmit power level corresponding to Federal Communications Commission(FCC) provisional limit for enabling UWB operation at 3.5 GHz bands.

• Journal of Communications and Networks
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• 제5권4호
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• pp.365-373
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• 2003

This paper investigates the performance of M-ary pulse position modulation (PPM) multiuser ultra-wideband (UWB) communication systems in terms of symbol error rate (SER) over fading and additive white Gaussian noise (AWGN) channel. Based on Gaussian approximation for the multiple access interference, an expression for the signal-to-noise ratio (SNR) is derived for the UWB system. This expression is used to derive exact SER expressions for coherent UWB receivers. The effect of pulse selection on the SER of multiuser UWB system is studied. In addition to rectangular pulse, the 2nd derivative Gaussian waveform and Rayleigh pulses were considered. We show that the system capacity and/or SER performance can be significantly increased by using the monocycle pulse in fading channels.