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© DIGITALSTOCK

Zhi Ning Chen, Max J. Ammann, Xianming Qing,

Xuan Hui Wu, Terence S.P. See, and Ailian Cai

T

tion performance are outlined. After that, the planar

he release of an extremely wide spectrum

antennas printed on PCBs are described. A directional

of 3.1­10.6 GHz for commercial applica-

antipodal Vivaldi antenna is also presented for UWB

tions has greatly spurred the research and

applications. Last, a UWB antenna for wearable appli-

development of microwave ultrawideband

cations is exemplified.

(UWB) technology for communications,

imaging, radar, and localization applications. In accor-

Introduction

dance, many techniques to broaden the impedance

bandwidth of small antennas and to optimize the char-

UWB systems are based on transmitting and receiving

acteristics of the broadband antennas have been wide-

impulses with extremely wide spectra. Recently,

ly investigated. This article reviews the state of the art

extremely broad frequency ranges have been allocated

in broadband antennas for emerging UWB applications

for UWB imaging, communications, and radar and

and addresses the important issues of the broadband

localization systems. For example, the Federal

antenna design for UWB applications. First, a variety of

Communication Commission (FCC) legalizes a 10-dB

planar monopoles with finite ground planes are

bandwidth of 7.5 GHz (3.1­10.6 GHz) with a limited

emission level (lower than -41.3 dBm/MHz) for

reviewed. Next, the roll antennas with enhanced radia-

Zhi Ning Chen (chenzn@i2r.a-star.edu.sg), Xianming Qing (qingxm@i2r.a-star.edu.sg), Xuan Hui Wu (xwu1@olemiss.edu), Terence S.P. See

(spsee@i2r.a-star.edu.sg), and Ailian Cai (alcai@i2r.a-star.edu.sg) are with Institute for Infocomm Research, 20 Science Park Road, #02-21/25

TeleTech Park, Singapore 117674. Max J. Ammann (mammann@dit.ie) is with Centre for Telecommunications Value-chain-driven Research,

School of Electronic and Communications Engineering, Faculty of Engineering, Dublin Institute of Technology, Kevin St. Dublin 8, Ireland.

December 2006

63

1527-3342/06/$20.00©2006 IEEE