• Journal of electromagnetic engineering and science
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• v.13 no.2
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• pp.63-72
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• 2013

The ultra-wideband (UWB) spectrum available for commercial applications has offered us an opportunity to achieve high-speed wireless communications and high-accuracy location applications. As one of key research areas in UWB technology, a lot of innovative broadband and miniaturization techniques for UWB antennas have been greatly invented and developed for years. This paper reviews the development of UWB antenna design in the past decade. Starting with a brief introduction of the specific requirements and promising applications of UWB systems, the unique design challenges of UWB antennas are highlighted. Next, the important milestones of UWB antenna designs are briefed. After that, a variety of planar UWB antennas invented for broadband operation, miniaturization, and multiple functions are introduced. Last, the comments on the development of UWB antennas in future are shared.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.4
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• pp.603-610
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• 2008

In this paper, analytical methods for calculating the average probability of bit error of direct sequence pulse amplitude modulation ultra wideband (DS-PAM UWB) system and time hopping pulse position modulation ultra wideband (TH-PPM UWB) system are given. For the multi-user DS-PAM UWB system, the bipolar pulse amplitude modulation is used in order to achieve better performance. As we know, more attention is paid to the TH-PPM UWB systems recently. In this paper. we first introduce the accurate BER calculation methods of the multi-user DS-PAM UWB and TH-PPM UWB systems and then give the performance analysis over the ideal AWGN channel and a correlation receiver. Furthermore, we also introduce their applications in image transmission and data transmission and give the simulation results. The analytical method yields simple and exact formulas relating the performance to the system parameters.

• Journal of Communications and Networks
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• v.5 no.4
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• pp.344-353
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• 2003

Ultra-wideband (UWB) technology is gaining increasing interest for its potential application to short-range indoor wireless communications. Utilizing ultra-short pulses, UWB baseband transmissions enable rich multipath diversity, and can be demodulated with low complexity receivers. Compliance with the FCC spectral mask, and interference avoidance to, and from, co-existing narrow-band services, calls for judicious design of UWB pulse shapers. This paper introduces pulse shaper designs for UWB radios, which optimally utilize the bandwidth and power allowed by the FCC spectral mask. The resulting baseband UWB systems can be either single-band, or, multi-band. More important, the novel pulse shapers can support dynamic avoidance of narrow-band interference, as well as efficient implementation of fast frequency hopping, without invoking analog carriers.

• Journal of Communications and Networks
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• v.8 no.2
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• pp.151-157
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• 2006

In a continuously expanding wireless world, the number of radio systems increases every day and efficient spectrum usage becomes a more significant requirement. Ultra-wideband (UWB) and cognitive radio are two exciting technologies that offer new approaches to the spectrum usage. The main objective of this paper is to shed the first light on the marriage of these two important approaches. The strength of orthogonal frequency division multiplexing (OFDM) based UWB in co-existing with licensed systems is investigated. The opportunity concept is defined, and the requirements of the opportunistic spectrum usage are explained. It is proposed to take the UWB-OFDM from the current underlay implementation, and evolve it to a combined underlay and opportunistic spectrum usage technology, leading to cognitive UWB-OFDM. This way, we aim at making UWB more competitive in the wireless market with extended range, higher capacity, better performance, and a wide variety of applications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.3C
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• pp.368-373
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• 2004

Extremely fine tine resolution of ultra-wideband (UWB) signal poses a new problems to the system designer. A reasonable accuracy of the system clock is necessary to process signals with such a high space resolution. A useful way of illustrating the time resolution of a signal is to evaluate the ambiguity function. The ambiguity function for carrierless UWB defined using the time mismatch and time scaling factor as its two parameters. The UWB ambiguity function is evaluated for various signaling schemes of impulse radio.

• Information and Communications Magazine
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• v.20 no.2
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• pp.109-117
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• 2003

UWB 기술은 주파수 영역에서 광대역을 갖는 임펄스를 사용하므로 목표물로부터 많은 정보를 얻어, 고해상도 레이더 개발이 가능하다. 이러한 UWB 레이더의 특성을 이용하여 한국전기연구원에서는 지중 금속 물체를 탐지하기 위한 지반 탐사 레이더를 개발하였다. 개발된 레이더는 실제환경에서 금속 물체를 탐지하기 위해서 시험되었다. 개발된 레이더는 물체의 깊이에 대해 고해상도를 가졌고, 동작 파장보다 훨씬 작은 금속 물체까지도 탐지가 가능함을 보였다. 본 논문에서는 개발된 지반 탐사 UWB 레이더 시스템을 소개하고, UWB 레이더의 특성 및 UWB 기술에 대해 기술하고자 한다.

• ETRI Journal
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• v.29 no.4
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• pp.518-520
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• 2007

In this letter, we propose an impulse series for an ultra-wideband-based cognitive radio system which can utilize the spectrum dynamically by controlling the impulse positions and thus reduce the system complexity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.8A
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• pp.836-846
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• 2007

Wireless Communication is playing a key role in implementing the ubiquitous society. However, due to the increasing wireless and mobile devices occupying the spectrum, the frequency resources are believed to become more and more limited. In order to deal with the problem, coexistence is considered to be a effective method to improve the efficiency of spectrum utilization between several different systems. Here, we utilize the UWB system to realize the coexistence, because it is an ultra wide band system which can co-exist with other narrow band systems. On the other hand, Cognitive Radio technology is an intelligent technology which can sense the spectrum environment and adaptively adjust the parameters for wireless transmission. In this paper, by using Cognitive UWB, the spectrum efficiency of the transmission channels is largely improved; Furthermore, the interference to other systems can be effectively avoided.

• Journal of electromagnetic engineering and science
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• v.6 no.1
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• pp.76-81
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• 2006

Ultra wideband(UWB) technologies have been developed to exploit a new spectrum resource in substances and to realize ultra-high-speed communication, high precision geo-location, and other applications. The energy of UWB signal is extremely spread from near DC to a few GHz. This means that the interference between conventional narrowband systems and UWB systems is inevitable. However, the interference effects had not previously been studied from UWB wireless systems to conventional wireless systems sharing the frequency bands such as Broadcasting system. This paper experimentally evaluates the interference from two kinds of UWB sources, namely a orthogonal frequency division Multiplex UWB source and an impulse radio UWB source, to a Broadcasting transmission system. The receive power degradations of broadcasting system are presented. From these experimental results, we show that in all practical cases UWB system can coexist 35 m distance in-band broadcasting network.

• Journal of Advanced Navigation Technology
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• v.11 no.3
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• pp.274-280
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• 2007

An ultra-wideband signal is characterized by a radiated spectrum with wide bandwidth around a relatively low center frequency. In this paper, the bit error rate (BER), packet error rate (PER), and data throughput performance for an ultra-wideband system with M-ary correlation receiver are analyze in additive white Gaussian noise (AWGN) and co-channel interference channel. To evaluate the performance of UWB system, a set of UWB communication waveform as pulse position modulated (PPM) signals consisting of more than one UWB pulse is used. The M-ary PPM signals are defined to be equally correlated in order to simplify the system performance analysis. The analysis for system performance shows that the wireless channel error significantly degrades throughput performance and can be effectively increased by hybrid ARQ scheme. Also, an attempt for comparing the data throughput of ultra-wideband system on different performance improvement schemes and parameters has been made. From the performance evaluation process, it is shown that the effects of wireless channel and hybrid ARQ scheme for ultra wideband M-ary PPM system can be evaluated by means of a suitable combination of the PER, throughput vs. signal-to-noise power ratio per bit.