This paper presents the design and results of an offset feed Ultrawideband(UWB) antenna with a multiple-slotted ground plane. The antenna consists of a square shaped radiator, a feed slightly offset from the middle along the radiator side and a ground plane with multiple rectangular slots. Simulation results show that the antenna can achieve a wide bandwidth from 3.3 to 18 GHz. © 2011 IEEE.published_or_final_versionThe 2011 International Workshop on Antenna Technology (iWAT), Hong Kong, China, 7-9 March 2011. In Proceedings of iWAT, 2011, p. 432-43

Azim, R

Cheung, SW

Islam, MT

Misran, N

Sun, YY

Yuk, TI

Y. Y. Sun

M. Tariqul. Islam

S. W. Cheung

T. I. Yuk

R. Azim

N. Misran

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Offset-fed UWB antenna with multi-slotted ground plane

This paper presents the design and results of an offset feed Ultrawideband(UWB) antenna with a multiple-slotted ground plane. The antenna consists of a square shaped radiator, a feed slightly offset from the middle along the radiator side and a ground plane with multiple rectangular slots. Simulation results show that the antenna can achieve a wide bandwidth from 3.3 to 18 GHz. © 2011 IEEE.link_to_subscribed_fulltextThe 2011 International Workshop on Antenna Technology (iWAT), Hong Kong, China, 7-9 March 2011. In Proceedings of iWAT, 2011, p. 432-43

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Title Offset-fed UWB antenna with multi-slotted ground planeAuthor(s) Sun, YY; Islam, MT; Cheung, SW; Yuk, TI; Azim, R; Misran, NCitationThe 2011 International Workshop on Antenna Technology(iWAT), Hong Kong, China, 7-9 March 2011. In Proceedings ofiWAT, 2011, p. 432-436Issued Date 2011URL http://hdl.handle.net/10722/140291Rights International Workshop on Antenna Technology Small Antennasand Novel Metamaterials (iWAT) Proceedings. Copyright © IEEE.Offset-fed UWB Antenna with Multi-slotted Ground PlaneY.Y. Sun*(1), M. Tariqul. Islam(2), S.W. Cheung(1), T.I. Yuk(1), R. Azim(2),(3) and N. Misran(2),(3)(1) Department of Electrical & Electronic Engineering, The University of Hong Kong, Pokfulam Road,Hong KongEmail: [yysun, swcheung, tiyuk]@eee.hku.hk(2) Institute of Space Science (ANGKASA), Faculty of Engineering and Built EnvironmentUniversiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, MalaysiaEmail: titareq@yahoo.com(3) Department Electrical, Electronics and Systems Engineering, Faculty of Engineering and BuiltEnvironmentUniversiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, MalaysiaABSTRACT: This paper presents the design and results of an offset feed Ultrawideband(UWB) antenna witha multiple-slotted ground plane. The antenna consists of a square shaped radiator, a feed slightly offset fromthe middle along the radiator side and a ground plane with multiple rectangular slots. Simulation results showthat the antenna can achieve a wide bandwidth from 3.3 to 18 GHz.1. INTRODUCTIONBroadband and multiband antennas play strong roles in the wireless communications world becauseof the increasing demand of high data transmitting rates. Ultra-wideband (UWB) technology, due to theadvantages of low cost, low complexity, low spectral power density, high precision ranging, low interferencesand extremely high data rates, has attracted much attention. Since the Federal Communications Commission(FCC) allocated 7.5 GHz spectrum from 3.1 to 10.6 GHz for UWB radio applications in 2002 [1], UWBantennas, as a key component in UWB system, have been widely investigated by many researchers [2-9].However, the design of efficient and compact size antennas for wideband applications is still a majorchallenge. Many microstrip-fed and coplanar waveguide-fed antennas have been reported for UWBapplications [2-9]. These antennas employed either the monopole configuration with different shapes (circularring, ellipse, annual ring, triangle, pentagon or hexagon) or the dipole configuration (e.g. the bow-tie antennas)[2-9]. Some of these UWB antennas did not have planar structures (i.e., their ground planes wereperpendicular to the radiators). As a result, these antennas cannot be easily integrated with the printed circuitboards.Numerous methods can be used to increase the bandwidth of UWB antennas, e.g. using thickersubstrate or substrates with lower dielectric constants, employing various feeding techniques and using slotantenna geometry [10,11]. However, the bandwidth and the size of an antenna are generally mutuallyconflicting. Improving one characteristic normally results in degrading the other.Different techniques can be used to increase the impedance bandwidths of the circular and ellipticalplanar monopole antennas, e.g. inserting an additional stub to the one side of the circular patch [12],increasing the elliptically ratio of ellipse-shaped patch [4], adding slot to one side of the radiating element [13]and adding steps to the lower edge of the patch [14]. The square shaped antenna fed by a microstrip line,which has the planar configuration, is a good candidate for wideband applications.In this paper, a wideband antenna that consists of a square shaped radiator, a feed line slightly offsetfrom the middle along the side of the radiator and a ground plane with rectangular slots is proposed. Resultsshow that the proposed antenna can achieve a bandwidth from 3.3 GHz to 18 GHz with Voltage-Standing-Wave Ratio (VSWR)  2 and nearly omnidirectional radiation patterns almost over the entire UWB band.2. ANTENNA STRUCTUREThe geometry of the proposed antenna is shown in Fig. 1. It consists of a square shaped radiator withan offset feed line and a partial ground plane with rectangular slots. The antenna is fabricated on a low costFR4-substrate with a thickness of 1.6 mm, a relative permittivity of 4.6 and a total size of W × L. The squareshaped radiator has an area of WP × LP and the microstrip-fed line is printed on one side of the substrate. Thewidth of the microstrip-fed line is fixed at wm to achieve 50Ω characteristics impedance. A SMA connector isconnected to the port of the microstrip-fed line. The partial-ground plane with a length of lm is printed on theother side of the substrate. Some rectangular slots with dimensions 2mm× 1mm and 6mm × 1mm are added to432978-1-4244-9134-6/11/$26.00 ©2011 IEEEthe top side of the finite-ground plane to adjust the input impedance characteristics. The antenna has thefollowing parameters: W = 30 mm, L = 22 mm, WP = 14.5 mm, LP = 14.75 mm, D = 6mm, d = 3mm, wm = 2.6mm and lm = 7.25 mm. The geometric parameters of this structure can be adjusted to tune the return loss andbandwidth over a wide range of frequency. The square-shaped radiator is capable of supporting multipleresonant modes and hence to provide a wider impedance bandwidth. The slots on the partial-ground plane canbe used for improving matching, e.g. by increasing the gap between the radiating element and ground plane.As a result, the bandwidth is increased and the size of the ground plane is reduced.(a) Top View (b) Bottom View  (c)Side ViewFig. 1 Geometry of antenna3. RESULTS AND DISCUSSIONSThe geometry of proposed antenna has been optimized using the EM simulation tool, CST MS 2009[15]. The antenna has also been prototyped for verification. Fig. 2 shows the simulated and measured returnlosses of the antenna. The proposed antenna has an impedance bandwidth from 3.3 to 18 GHz. Thediscrepancy between simulation and measurement is mainly due to the solder and inaccuracies duringfabrication. Fig. 3 shows the peak gain of the antenna in the frequency range from 1 to 18 GHz. The antennahas a maximum gain of 5.2 dBi at 10.1 GHz with an average gain of 2.96 dBi. The radiation efficiency of theproposed antenna is shown in Fig. 4. The antenna has a maximum radiation efficiency of 91.3% with anaverage of 61.7% through the whole bandwidth. At low frequency, the low radiation efficiency of the antennais due to the high return loss as shown in Fig. 2. At high frequency, the low readiation efficiency is due to thehigh losses in FR4 substrates.Fig. 5 shows the radiation patterns of the proposed antenna at three frequencies, 4.5, 10.2 and 18GHz. It can be seen that the H-plane radiation patterns are almost omnidirectional. The E-planes radiationpatterns at 4.5, 10.2 and 18 GHz do not have obvious null which is very different from a normal monopoleantenna. This is due to the antenna being offset fed.4. CONCLUSIONSAn offset-fed antenna with a multiple-slotted ground plane has been designed and proposed for UWBapplications. The antenna has a compact size of 30 mm × 22 mm and is simple and very easy to be integratedwith microwave circuitry for low manufacturing costs. The use of rectangular slots on the top side of thepartial-ground plane not only improves the impedance matching but also the radiation characteristics in thehigh frequency band. The antenna can achieve an impedance bandwidth from 3.3 to 18 GHz with nearly aconstant peak gain. The radiation patterns in the H-plane are almost omnidirectional over the entire frequencyband. There is no obvious null observed in the radiation patterns in the E-plane. The stable radiation patternsand constant peak gain make the proposed antenna suitable for use in UWB communication systems.Fig. 2 Simulated and measured return losses433Fig. 3 Peak gain      Fig. 4 Radiation efficiency(a)434(b)E-plane   (c) H-planeFig. 5 Radiation pattern at (a) 4.5 GHz, (b) 10.2 GHz, and (c) 18 GHz435References[1] Federal Communications Commission, Revision of Part 15 of the Commission’s Rules Regarding Ultra-Wideband Transmission System from 3.1 to 10.6 GHz, in Federal Communications Commission,Washington, DC: ET-Docket, pp: 98–153, 2002.[2] D.B. Lin, I. T. Tang, and M. Y. Tsou, “A compact UWB antenna with CPW-fed,” Microw. Opt. Technol.Lett., vol. 49, pp. 372–375, 2007.[3] Y. J. Ren and K. Chang, “Ultra-wideband planar elliptical ring antenna,” Electron. Lett., vol. 42, no. 8, pp.447- 449, 2006.[4] J. Liang, C. C. Chiau, X. Chen, and C. G. Parini, “Printed circular ring monopole antennas,” Microw. Opt.Technol. Lett., vol. 45, pp. 372–375, 2005.[5] Y. J, Ren YJ and K. Chang, “An Annual Ring Antenna for UWB Communications,” IEEE AntennasWireless Propag. Lett., vol. 5, no. 1, pp. 274–276, 2006.[6] J.X. Xiao, M. F. Wang, and G. J. Li, “A ring monopole antenna for UWB application,” Microw. Opt.Technol. Lett., vol. 48, no. 1, pp. 179–182, 2010.[7] J. Jung, W. Choi, and J. Choi, “A small wideband microstrip-fed monopole antenna,” IEEE Microw.Wireless Compon. Lett., vol. 15, no. 10, pp. 703–705, 2005.[8] J. S. Zhang and F. J. Wang, “Study of a double printed UWB dipole antenna,” Microw. Opt. Technol.Lett., vol. 50, pp. 3179–3181, 2008.[9] K. Kiminami, A. Hirata, and T. Shiozawa, “Double-sided printed bow-tie antenna for UWBcommunications,” IEEE Antennas Wireless Propag. Lett., vol. 3, no. 1, pp. 152–153, 2004.[10] M. M. Matin, B.S. Sharif, and C.C. Tsimenidis, “Probe fed stacked patch antenna for widebandapplications,” IEEE Trans. Antennas  Propag., vol. 55, no. 8. pp. 2385-2388, 2007.[11] S.H. Wi, Y. B. Sun, I. S. Song, et al., “Package-Level integrated antennas based on LTCC technology,”IEEE Trans. Antennas  Propag., vol. 54, no. 8, pp. 2190–2197, 2006.[12] K. Ray and Y. Ranga, “Ultrawideband printed elliptical monopole antennas,” IEEE Trans. AntennasPropag., vol. 55, no. 4, pp. 1189-1192, 2007.[13] K. Kim and S. Park, “Analysis of the small band-rejected antenna with the parasitic strip for UWB,”IEEE Trans. Antennas Propag., vol. 54, no. 6, pp. 1688-1692, 2006.[14] J. Choi, K. Chung, and Y. Roh, “Parametric analysis of a band-rejected antenna for UWB applications,”Microw. Opt. Technol. Lett., vol. 47, pp. 287-290, 2005.[15] http://www.cst.com.436

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Offset-fed UWB antenna with multi-slotted ground plane

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