4. CONCLUSIONS A new type of microstrip-fed small size monopole antenna has been proposed for UWB applications. To achieve wide impedance bandwidth, a pair of wide stubs is employed at the lower sides of a triangular patch and the upper edges of the partial ground plane on the backside are linearly tapered. The experimental results exhibit that the return loss is better than -9 dB from 2.9 to 12 GHz and the radiation pattern is nearly omnidirectional over the entire UWB band. The variation of the measured group delay between two identical antennas is less than 1.6 ns. The proposed antenna has features of small size and independence of the impedance bandwidth on the length of the ground plane, making it easy to integrate with other RF circuits. ACKNOWLEDGMENT The authors acknowledge Dr. H. Sawada, National Institute of Information and Communications Technology (NICT), Japan, for his help in manufacturing and measurement of the antenna. REFERENCES 1. S. Roy, J.R. Foerster, V.S. Somayazulu, and D.G. Leeper, Ultrawide- band radio design: The promise of high-speed, short-range wireless connectivity, Proc IEEE 92 (2004), 295–311. 2. M.A. Peyrot-Solis, G.M. Galvan-Tejada, and H. Jordan-Aguilar, State of the art in ultra-wideband antennas, Electr Electron Eng Conf (2005), 101–105. 3. H.K. Kan, W.S.T. Rowe, and A.M. Abbosh, Compact coplanar waveguide-fed ultra-wideband antenna, Electron Lett 43 (2007), 654 – 656. 4. P. Li, J. Liang, and X. Chen, Study of printed elliptical/circular slot antennas for ultrawideband applications, IEEE Trans Antennas Propag 54 (2006), 383–388. 5. Z.N. Chen, T.S.P. See, and X. Qing, Small printed ultrawideband antenna with reduced ground plane effect, IEEE Trans Antennas Propag 55 (2007), 1670 –1675. 6. C.-C. Lin, Y.-C. Kan, L.-C. Kuo, and H.-R. Chuang, A planar triangular monopole antenna for UWB communication, IEEE Microwave Wire- less Compon Lett 15 (2005), 624 – 626. 7. J.R. Verbiest and G.A.E. Vandenbosch, Small-size planar triangular monopole antenna for UWB WBAN applications, Electron Lett 42 (2006), 566 –567. 8. K.P. Ray and Y. Ranga, Ultra-wideband printed modified triangular monopole antenna, Electron Lett 42 (2006), 1081–1082. © 2008 Wiley Periodicals, Inc. 2.45 GHz INTER-/INTRABOARD WIRELESS COMMUNICATION USING A CPW-FED VERTICAL BOW TIE ANTENNA J. K. Kim, S. Y. Cha, T. S. Yun, and Y. K. Yoon University at Buffalo, The State University of New York, Buffalo, NY 14260; Corresponding author: jkkim5@buffalo.edu Received 22 May 2008 ABSTRACT: Coplanar waveguide (CPW)-fed vertically standing bow- tie antennas for 2.45 GHz ISM band applications for inter-/intraboard wireless communication are presented. The vertical antenna scheme provides wave propagation in the horizontal direction parallel to the substrate, allowing effective in-plane board-to-board communication. The monopole bow-tie antenna is implemented in an air-lifted fashion, resulting in high efficiency, broad bandwidth, and small footprint com- pared with the conventional surface mounted patch type antenna. The vertical bow-tie antenna with a height of 22.4 mm and a flare angle of 43° shows a 10-dB bandwidth of 20.4%, a footprint of 1 mm 2 , and a height reduction of 33% compared with a cylindrical monopole counter- part. A numerical analysis has been performed between 1 and 4 GHz and the transmission characteristics using two identical antennas have been performed at 2.45 GHz with a network analyzer. The numerical results are in good agreement with experimental data. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 266 –269, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23988 Key words: bow-tie antenna; vertically standing; interboard communi- cation; intraboard communication; in-plane board-to-board communica- tion 1. INTRODUCTION During the last decade, the integration and packaging technologies for radio frequency (RF) systems have been rapidly advanced in both board and chip levels. System-on-package/system-on-pack- age (SOP or SIP) and system-on-chip (SOC) technologies are proposed [1, 2], but there is no predominant one and rather all the technologies are coexisting these days. Technology selection thus is determined by various factors such as overall system perfor- mance, size, cost, and connectivity with other systems, etc. From the SOC point of view, both active and passive compo- nents including inductors and capacitors are integrated on a single chip [3] and further attempts to integrate an antenna module on a chip have been reported for an application of wireless chip-to-chip communication [4, 5]. Although this approach provides a mono- lithic fabrication advantage, those passive components and anten- nas on the Si substrate experience relatively large RF loss associ- ated with the conductive Si substrate. To reduce the substrate effects, advanced surface micromachining processes have been developed and high-Q inductors and high efficiency integrable vertical air-lifted millimeter wave antennas have been successfully demonstrated [6, 7]. The air-lifted architecture is not dependent on a substrate type and loss and thus considered as a good candidate 3 4 5 6 7 8 9 10 11 12 -2 -1 0 1 2 3 4 5 6 Gain (dBi) Frequency (GHz) Figure 5 Simulated peak gain of the proposed antenna 3 4 5 6 7 8 9 10 11 12 0 1 2 3 Group delay (ns) Frequency (GHz) Figure 6 Measured antenna group delay 266 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 51, No. 1, January 2009 DOI 10.1002/mop