Novel Dual-band CPW-fed Monopole Slot Antenna for WLAN/WiMAX Applications

Davinder Parkash1, Dr. Rajesh Khanna2, Vikas Kumar1, Ankit Chaudhary1

1Haryana College of Technology and Management, Kaithal2Thapar University, Patiala

E-mail : devinder@ieee.org , vikas_rs97@yahoo.com

Abstract : A novel dual-band design of a finite ground coplanar waveguide (CPW)-fed monopole antenna is presented for simultaneously satisfying wireless local area network (WLAN) and worldwide interoperability for Microwave Access (WiMAX) applications. The proposed antenna, comprising a rectangular planar patch element embedded with two L shaped slots and stair shape slot in the middle of the patch element. The simulated -10 dB bandwidth for return loss is from 3.34 to 4.056 GHz and 4.736 to 5.432 GHz, covering some of the WiMAX and WLAN bands. Prototypes of the obtained optimized antenna have been designed and constructed. The parametric study is performed to understand the characteristics of the proposed antenna. Also, good antenna performances such as radiation patterns and antenna gains over the operating bands have been observed and simulated peak gain of the antenna is 4.88 dBi at 4.3 GHz.

Index Terms : Dual-band antennas, Monopole antennas, WiMAX and WLAN

I. IntroductionMultiband printed monopole antennas have aroused widespread applications, especially in low power wireless communication gadgets. In the era of modern wireless communication systems, dual-band or multiband antennas with omni-directional radiation characteristics play a vital role [1, 2]. Advances in wireless communication technologies are placing greater demands on higher antenna impedance bandwidth and smaller antenna size. The design of broadband antennas has received the attention of many antenna researchers due to their various applications [3]. The currently popular designs suitable for WLAN operation in the 2.4 GHz (2.4–2.484 GHz) and 5.2/5.8 GHz (5.15–5.35 GHz/5.725–5.825GHz) bands and WiMAX operation in the 2.5/3.5/5.5 GHz bands have been reported in [1-14]. The planar monopole antenna has received much more interest than others, due to its potential in providing the various radiation features required for dual-band or multi-band, wide bandwidth, low profile communication systems. However, these kinds of antennas mostly need a large ground plane, which is often printed on the opposite side of the substrate from the radiating plane. Thus a via-hole connection is always necessary for feeding the signal, and this increases the manufacturing difficulty and cost. Recently, the coplanar waveguide (CPW)-fed monopole antenna has become very popular in WLAN and WiMAX systems, owing to its many attractive features such as, wider bandwidth, low radiation loss, a simple structure of a single metallic layer and easy integration with WLAN integrated circuits [8]. In this paper, a proposed antenna design with CPW-feed technology has been used to achieve dual-band operation for both WLAN and WiMAX bands. The proposed dual band antenna consists of a rectangular shaped patch element embedded with two L shaped slots and stair-shape slot in the middle of the patch element, capable of generating two separate bands with

good impedance matching conditions. This way, the antenna can achieve a dual-band performance to simultaneously cover the most commonly used 5.2 GHz WLAN and 3.5 GHz WiMAX bands. Details of the proposed antenna design are described in the paper, and simulated results are presented and discussed in the following sections.

II. Antenna DesignFig.1 shows the geometry of the proposed finite ground coplanar waveguide (CPW) fed dual-band monopole antenna. The proposed antenna was fabricated on FR4 substrate with dielectric constant 4.4 and thickness 1.6 mm. The basis of the antenna structure is chosen to be a rectangular patch element with dimensions of width W and length L, and with a vertical spacing of ‘d’ away from the ground plane. A conventional CPW-fed line designed with a fixed signal strip thickness Wf and a gap distance of ‘g’ between the signal strip and the coplanar ground plane is used for exciting the radiating patch element. Two finite ground planes with the same size of width Wg and length Lg, are situated symmetrically on each side of the CPW feeding line.

Fig. 1 Geometry of the proposed dual-band antenna

The final optimized dimensions of proposed antenna are: length of the rectangular patch L=19.3mm, width of the rectangular patch W=19.27mm, width of ground plane Wg=10.2 mm, length of ground plane Lg=16.2 mm. Slot length are: L1=5.7mm, L2=7.5mm, L3=10.2mm, L4=14.6 mm, L5=9.41mm and having slot width of Ws=1mm. The space between the rectangular patch and ground plane g=3mm and the feed line width of the feeding port is Wf = 3mm and vertical spacing between feed-line and ground plane d=1mm. The optimum parameters are obtained with the aid of IE3D software. Total volume of the proposed antenna is 0.6 cm3. Photograph of the fabricated prototype is shown in Fig.2.

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Fig. 2 Photograph of the proposed antenna

III. Results And DiscussionThe simulated parametric study results and return losses for the proposed monopole antenna are obtained. The simulated return losses are presented for the optimized set of antenna parameters in Fig.3.The simulated impedance bandwidth of the proposed antenna covers two impedance bandwidths, 3.34 to 4.056 GHz as the lower band and 4.736 to 5.432 GHz as the upper band, respectively. It can cover the 5.15–5.35 GHz WLAN band, and 3.4–3.69 GHz WiMAX band of wireless communication system.

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The parametric study is carried out by simulating the antenna with one geometry parameter slightly changed from the reference design while all the other parameters are fixed. Fig. 4 shows the variation on the return losses due to change in gap between the patch element and ground plane i.e. g.

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Fig. 4 Effect of variaition of gap between patch and ground on return loss

It is observed from the simulation results study that by decreasing the gap from the optimum value, the impedance bandwidth decreases in both the bands. It is also observed from simulation result that by increasing the gap from optimum value, the bandwidth in lower-band increases whiles the bandwidth decreases in upper frequency band. The optimal performance is obtained for g = 3 mm. The current distribution of the proposed antenna using IE3D simulator is shown in Fig. 5. The surface currents mainly flow along the lower edges of patch and over the lower edges of the slot L1, L2 and L5 and along the signal strip line.

Fig. 5 Simulated current distribution of the proposed antenna.

The simulated radiation patterns of the proposed CPW-fed monopole antenna are presented in Fig. 6-7 for different frequencies at 3.5 GHz and 5.2 GHz. The simulated radiation patterns cut in the azimuthal plane (x-y) is shown in Fig. 6(a) and cut in the elevation plane (y-z) is shown in Fig. 6(b) for the proposed antenna at the lower frequency band of 3.5 GHz is presented and respectively radiation pattern at 5.2 GHz frequency is shown in Fig.7.

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Fig. 6 : Simulated radiation pattern at frequency 3.5 GHz

The radiation pattern obtained in the x-y plane is nearly omni-directional, and that in the elevation plane is similar to monopole kind of antenna. Radiation performance of the antenna is acceptable at all the frequency bands.

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Fig. 7 : Simulated radiation patterns at frequency 5.2 GHz

The simulated gain of the proposed antenna is depicted in Fig.8. In lower band 3.34 to 4.056 GHz the gain is 2.67 dBi with variation in gain less than 1dBi. In upper band the gain varies from 2.72 dBi to 4.04 dBi.

IV. ConclusionA dual-band monopole antenna covering WiMAX and WLAN bands is proposed. The various parameters of the proposed antenna are optimized through simulation. Prototype of the proposed antenna has been designed, simulated and fabricated. The simulated return loss bandwidths are observed to be 3.34 to 4.056 GHz and 4.736 to 5.432 GHz in the lower and upper frequency bands respectively. The proposed antenna provides nearly omni-directional radiation characteristics with moderate gain and efficiency which is suitable for the next generation wireless communication gadgets.

Fig. 8 Simulated peak gain of the antenna against frequency

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monopole antenna for GSM/DCS/PCS/WLAN operation”. Microwave Optical Technol. Letters, vol. 36, 2003, p. 350–352.

[2] Lee, L.S.; Hall, P.S.; and Gardner, P, “Compact wideband planar monopole antenna”. Electronics Letters, vol. 35, 1999, p. 2157–2158.

[3] Mazinani, S. M.; Hassani, H. R., “A novel omni-directional broadband planar monopole antenna with various loading

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plate shapes”. Progress In Electromagnetics Research, PIER, vol. 97, 2009, p. 241-257.

[4] Dakeya, Y., Suesada, T., Asakura, K., Nakajima, N., and Mandai., H.; “Chip multiplayer antenna for 2.45 GHz-band application using LTCC technology”. Proc. Int. IEEE MTT-S Microwave Symposium Dig, vol. 3, June 2000, p. 1693–1696.

[5] Kuo, Y.L.; and Wong, K.L, “Printed double-T monopole antenna for 2.4/5.2 GHz dual-band WLAN operations”. IEEE Trans. Antennas Propagation, vol. 51, 2003, p. 2187–2192.

[6] Chen, H.D.; Chen, J.S.; and Cheng, Y., “Modified inverted-L monopole antenna for 2.4/5 GHz dual-band operations”. Electronics Letters, vol. 39, 2003, p. 1567–1568.

[7] Chung, K.; Yun, T.; and Choi, J., “Wideband CPW-fed monopole antenna with parasitic elements and slots”. Electronics Letters, vol. 40, 2004, p. 1038–1040.

[8] Liu, W.C, “Broadband dual-frequency cross-shaped slot CPW-fed monopole antenna for WLAN operation”. Microwave Optical Technol. Letters, vol. 46, 2004, p. 353–355.

[9] Liu, W.C.; and Hsu, C.F, “Dual-band CPW-fed Y-shaped monopole antenna for PCS/WLAN application”. Electronics Letters, vol. 41, 2005, p. 390–391.

[10] Chen, H.D.,; and Chen, H.T, “A CPW-fed dual-frequency monopole antenna”. IEEE Trans. Antennas Propagation, vol. 52, 2004, p. 978–982.

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Davinder Parkash was born in Haryana, India in 1976. He received B.Tech. and M.Tech. degree from the Deptt. of Electronics and Communication Engineering at Kurukshetra University, Kurukshetra and NIT, Kurukshetra in 1999 and 2007 respectively. He is currently working toward a P.hD. degree at Thapar University, Patiala. He is currently working as Assoc. Prof. and M.Tech. Coordinator at

Department of Electronics and Communication Engineering in Haryana College of Technology and Management, Haryana (India). He received the ‘Young Scientist Award’ from the Governor of Punjab (India) for his research work in the field of Antenna design. He has published 15 papers in national and international journal/ conferences. His main research interest

includes the analysis and design of microstrip antennas, RFID application, application of metamaterials and Wireless communication.Ankit Chaudhary was born in Haryana, India in 1988. He received B.Tech. degree from the Deptt. of Electronics and Communication Engineering at Kurukshetra University, Kurukshetra in 2010. His main research interest includes the analysis and design of multiband antennas, application of metamaterials and Wireless Communication.

Dr. Rajesh Khanna was born in Ambala, India. He received B.Sc. (Engg.) Degree in Electronics & Communication in 1988 from Regional Engineering College, Kurukshetra and M.E. degree in 1998 from Indian Institute of Sciences, Bangalore. He was with Hartron R&D centre till 1993. Until 1999, he was in All India Radio as Assistant Station Engineer. Presently he is working as Professor in the

Department of Electronics & Communication at Thapar Institute of Engineering & Technology, Patiala. He has published 80 papers in national and International journal/conferences. He has worth Rs 1.5 crore projects to his credits. His main research interest includes the analysis and design of antennas, Wireless Communication, MIMO and Fractional Fourier transform based wireless systems.

Vikas Kumar is a student of B.Tech., Elecronics and Communication Engineeing, H.C.T.M. Kaithal, Haryana, India. He has carried out a project on Dual BAND MONOPOLE ANTENNA FOR WLAN/WIMAX APPLICATIONS using IE3D software.

Ankit Chaudhary was born in Haryana, India in 1988. He received B.Tech. degree from the Deptt. of Electronics and Communication Engineering at Kurukshetra University, Kurukshetra in 2010. His main research interest includes the analysis and design of multiband antennas, application of metamaterials and Wireless Communication.

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