uwb bluetooth antenna

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PIERS ONLINE, VOL. 7, NO. 7, 2011 621

An Integrated UWB and Bluetooth Antenna with Dual

Band-notched Characteristic

K. C. Law, S. W. Cheung, and T. I. Yuk

Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, China

Abstract— This paper presents the design of an integrated Ultrawideband (UWB) and Blue-tooth microstrip monopole antenna with a dual band-notched characteristic. The antenna con-sists of an elliptical ring as the radiator to cover the frequency bands for both the Bluetooth(2.4–2.5 GHz) and UWB (3.1–10.6 GHz) applications. A triangular resonator and a meanderdefected-ground structure (DGS) are used to generate two notches at the centre frequencies of 2.856 and 5.5 GHz. The return loss, radiation pattern, peak gain and efficiency of the antennaare studied using computer simulation.

1. INTRODUCTION

Since the Federal Communication Commission (FCC) assigned 3.1–10.6 GHz frequency band of Ultrawideband (UWB) systems in February 2002 [1], UWB technology has been attracting consid-erable interests in both the academic and commercial domains due to the potentially high data rate(more than 110 Mbits/s) for short range, low power consumptions and easy connections to differentdevices such as wireless USB, PCs, high-definition TVs, etc.

In 2006 [2], the Bluetooth Special Interest Group (SIG) selected the WiMedia Alliance multi-band orthogonal-frequency-division multiplexing (MB-OFDM) version of UWB, which could beintegrated with the current Bluetooth wireless technology. Nowadays, some portable devices areequipped with the Bluetooth antenna and WLAN antenna. It will be a difficult task to put anadditional UWB antenna in the same portable devices due to the limited space available. Oneof the possible solutions is to use an antenna that can operate in both the UWB and Bluetoothfrequency bands.

The current IEEE802.11a/n WLAN systems are occupying a small portion of the UWB. Thus

there will be interference between the UWB systems and the IEEE802.11a/n systems. To reducethis interference, the antenna can be designed to have a band-notched characteristic. Differenttechniques have been studied to produce the band-notched features [3–11]. However, in thesedesigns, the suppressed gains and efficiencies of the antennas at the notched frequency bands werequite limited and far from zero.

In this paper, we propose a planar-monopole antenna using an elliptical ring as the radiator tocover both the UWB and Bluetooth frequency bands with a dual-band notch. As there are otherwireless communication systems between the Bluetooth and UWB bands, for example: 3GPP (2.57–2.62 GHz), CDMA2000 (US 2.5 GHz Band) and CMMB (2.635–2.66 GHz), a triangular resonatoris placed at the centre of the elliptical-ring radiator to create a notch at 2.856 GHz to reduceinterference between the Bluetooth system and these wireless systems. The centre frequency of the notch can be controlled by adjusting the dimensions of the triangular resonator. To reduce

interference between the UWB system and the IEEE802.11a/n WLAN system (5.15–5.825 GHz),a meander-DGS is employed to create another notched band at 5.5 GHz. Results show that thepeak gain can be suppressed by more than 12 dB at the frequency of around 5.5 GHz, which isdeeper than the notches designed for other integrated UWB and Bluetooth antennas [8–11], andthe efficiency is close to zero.

2. STRUCTURE OF ANTENNA, MODELING OF MEANDER-DGS AND DESIGN OF

ANTENNA

2.1. Structure of Antenna

Our proposed dual band-notched UWB antenna is shown in Fig. 1. In this design, we use theplanar-monopole technology to achieve a compact antenna size for applications in small wirelessdevices. The antenna has an area of 31.5× 39.75mm2 and is designed on a Roger PCB, RO4350B,

with a relative permittivity of 3.48, thickness of 0.762 mm and loss tangent of 0.0037. The antennaconsists of an elliptical-ring radiator fed by a 50-Ω microstrip line printed on one side of the




(a) (b) (c)

Figure 1: Configuration of proposed antenna: (a) top view, (b) side view and (c) bottom view.

Table 1: Optimized parameters of antenna (mm).

L L1 L2 L3 L4

39.75 13 2.1 1.5 4.58

L5 L6 gl t1 t2

0.63 3.68 14.5 17.25 5.25

W w1 w2 w3 w4

31.5 1.7 0.8 0.23 0.2

rh1 rh2 rv1 rv2

9.7 12.8 9.1 12

substrate. A triangular resonator is printed inside the elliptical-ring radiator to create a notchedfrequency band at 2.856 GHz next to the Bluetooth band. The other side of the substrate is aground plane where a meander-DGS is etched under the feed line and acts as an LC resonator tocreate another notched frequency band centered at 5.5 GHz. To achieve good impedance matching,the distance, gap, between the radiator and the ground plane is set to 0.6 mm and the width of thefeed line is tapered, changing gradually from w1 = 1.7 mm to w2 = 0.8 mm as shown in Fig. 1. Thedimensions of the antenna are optimized using computer simulation, with detailed values listed inTable 1.

2.2. Design of Antenna

The meander-DGS etched on the ground plane behaves like a parallel LC resonant [12, 13]. Atresonance, the signal from the feed line will be coupled into the meander-DGS, producing a notchedcharacteristic for the antenna. The inductance and capacitance of the LC resonant circuit can

be changed by using the dimensions of the meander-DGS and hence used to adjust the notchedfrequency. As an illustration, Fig. 2(a) shows the simulated notched frequency versus length L4 of the meander-DGS. To create a notch at a particular frequency, we can simply select the requiredvalue from Fig. 2(a).

There is no exact method to design a general microstrip triangular resonator, except for equi-lateral and isosceles right-angled triangular resonators [14, 15]. Usually, curve fitting is used as aguideline to design the triangular resonators, which is used in our studies here. We first studythe effects of the base t2 and height t1 of the triangular resonator on the resonant frequency bycomputer simulation. Fig. 2(b) shows the simulated resonant frequency versus t1 for different t2. Itcan be seen that t2 has an insignificant effect on the resonant frequency, but the resonant frequencyhas a linear relationship with the height t1. From these results, we can use linear interpolation torelate the centre frequency in GHz to t1 by the following equation:

f = −0.1893× t1 + 6.122 (1)




(a) (b)

Figure 2: Simulated resonant frequency versus (a) length L4 and (b) height t1 for different bases t2.

(a) (b) (c)

Figure 3: Simulated (a) return losses, (b) peak gain and (c) efficiency with or without notches.

Figure 4: Simulated radiation pattern of proposed antenna.

3. RESULTS AND DISCUSSIONS

The antenna has been designed with two notches, centered at 2.856 and 5.5 GHz, on a RO4350Bsubstrate using computer simulation. The simulated return losses of the antenna, with a singlenotch and dual notch are shown in Fig. 3(a). The return loss of the antenna without notch is alsoshown in the same figure for comparison. It can be seen that, in all these conditions, our proposedantenna has the bandwidths (for return loss > 10 dB) from 2.31 to over 12 GHz, fully satisfying thebandwidth requirement for UWB applications (3.1–10.6 GHz). For the antenna without any notch,the bandwidth is from 2.44 to over 12 GHz. With the triangular resonator, the lower operatingfrequency extends to 2.36 GHz and the notch at 2.856 GHz has a bandwidth (for return loss < 10dB)from 2.66 to 3.08 GHz. With the meander DGS, the notch is centered at 5.5 GHz with a bandwidthfrom 5.11 to 6.21 GHz, which can suppress interference to/from the WLAN systems operating inthe frequency band from 5.15–5.825 GHz. It should be noted that the triangular resonator and the

meander-DGS do not affect each other.The simulated peak gain and efficiency of our proposed antenna with two notches are shown in




Figs. 3(b) and 3(c), respectively. At the notched frequency of 5.5 GHz, the gain and efficiency aresignificantly dropped by more than 12 dB and to about 1.4%, respectively. Such large drops are dueto the high attenuation characteristic of the meander-DGS. At the notched frequency of 2.856 GHz,the gain and efficiency are dropped by about 5.4 dB and to about 16.8%, respectively. Across thefrequency band from 2.5–12 GHz, the gain varies from 2 to 5.5 dB and the antenna efficiency isabove 95%.

Figure 4 shows the simulated radiation patterns of the antenna at the notched frequencies of 2.856 and 5.5 and at 8 GHz. The radiation patterns in the H -plane at these frequencies are omni-directional. Radiation is substantially smaller at 5.5 GHz. At 8 GHz, the radiation pattern in theE -plane at 8 GHz shows two nulls in the z-direction which is typical for a monopole antenna. At2.858 and 5.5 GHz, the radiation patterns are smaller and distorted.

4. CONCLUSION

The design of an integrated UWB and Bluetooth antenna with a dual band-notched characteristichas been presented. The size of the antenna is only 31.5×39.75×0.832mm3. A triangular resonatorand meander-DGS have been employed to produce a dual-band notch centered at 2.856 and 5.5 GHz,with the corresponding peak gains dropping by about 5.4 dB and 12 dB and efficiencies to about16.8% and 1.4%.

REFERENCES

1. First Report and Order, Federal Communications Commission (FCC), Feb. 14, 2002.2. Specifications of Bluetooth System, Profiles, Version 1.1 [Online] Available: http://www.blue-

tooth.com.3. Abdollahvand, M., H. R. Hassani, and G. R. Dadashzadeh, “Novel modified monopole an-

tenna with band-notch characteristic for UWB application,” IEICE Electronics Express, Vol. 7,No. 16, 1207–1213, Aug. 2010.

4. Kim, K. H., Y. J. Chao, S. H. Hwang, and S. O. Park, “Band-notched UWB planar monopoleantenna with two parasitic patches,” Electron. Letters, Vol. 41, No. 14, 783–785, Jul. 2005.

5. Li, W. T., X. W., Shi, and Y. Q. Hei, “Novel planar UWB monopole antenna with triple band-notched characteristics,” IEEE Antennas and Wireless Propagation Letters, Vol. 8, 1094–1098,Oct. 2009.

6. Zhao, Y. L., Y. C. Jiao, G. Zhao, L. Zhang, Y. Song, and Z. B. Wong, “Compact pla-nar monopole UWB antenna with band-notched characteristic,” Microw. Opt. Technol. Lett.,Vol. 50, No. 10, 2656–2658, Oct. 2008.

7. Weng, Y. F., W. J. Lu, S. W. Cheung, and T. I. Yuk, “UWB antenna with single or dual-band notched characteristic for WLAN band using meandered ground stubs,” Loughborough Antennas & Propagation Conference, 767–760, Nov. 2009.

8. Kim, C., H. Ahn, J. Kim, X. Cheng, and Y.-K. Yoon, “A compact 5 GHz WLAN notchedbluetooth/UWB antenna,” Antennas and Propagation Society International Symposium , 1–4,Jul. 2010.

9. Zhan, K., Q. Quo, and K. Huang, “A novel kind of bluetooth and UWB antenna,” International Conference on Microwave and Millimeter Wave Technology (ICMMT), 1038–1041, May 2010.

10. Li, Z.-Q. and C.-L. Ruan, “A small integrated bluetooth and UWB antenna with WLANband-notched characteristic,” International Symposium on Signals, Systems and Electronics,

Vol. 1, 1–4, Sep. 2010.11. Weng, Y. F., S. W. Cheung, and T. I. Yuk, “An antenna for UWB and bluetooth standards with

band-notched characteristic,” International Conference on Ultra-wideband , 170–174, Sep. 2009.12. Weng, L. H., Y. C. Guo, X. W. Shi, and X. Q. Chen, “An overview on defected ground

structure,” Progress In Electromagnetic Research B , Vol. 7, 173–189, 2008.13. El Dein, A. Z., A. B. Abdel-Rahman, R. E. Fat-Helbary, and A. M. Montaser, “Tunable-

compact bandstop defected ground structure (DGS) with lumped element,” International Multi-conference on Systems Signals and Devices (SSD), 1–3, Jun. 2010.

14. Zhao, L.-P., X.-W. Dai, Z.-X Chen, and C.-H. Liang, “Novel design of dual-mode dual-bandbandpass filter with triangular resonators,” Progress In Electromagnetic Research , Vol. 77,417–424, 2007.

15. Hong, J. S. and S. Li, “Theory and experiment of dual-mode microstrip triangular-patchresonators and filters,” IEEE Trans. Microwave Theory and Techniques, Vol. 52, 1237–1243,Apr. 2004.

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