978-1-4799-2174-4/13/$31.00 ©2013 IEEE A compact quad-band planar monopole antenna for Bluetooth/WiMAX/WLAN applications Suvadeep Choudhury Radionics Laboratory, Department of Physics The University of Burdwan, Bardhaman West Bengal, INDIA. e-mail: suvadeepchoudhury@gmail.com Santasri Koley Radionics Laboratory, Department of Physics The University of Burdwan, Bardhaman West Bengal, INDIA. e-mail: santasrikoley27@gmail.com Abstract— A small size, low profile planar monopole antenna which operates in four frequency bands is proposed. The overall dimensions of the antenna are ) ( L W × 45 28 × mm 2 . A rectangular ‘C’ shaped slot is cut on the radiating element and rectangular open loop resonators are embedded in the ground section of the antenna structure. The antenna operates in 2.45 GHz (IEEE 802.15.1-Bluetooth), 3.5GHz (IEEE 802.16-WiMAX), 5.2GHz and 5.8GHz (IEEE 802.11a-WLAN) frequencies. Taconic TLY 5 (ε r =2.2) has been used as substrate. Keywords—Bluetooth, Worldwide Interoperability for Microwave Access (WiMAX), Wireless Local Area Network (WLAN), Microstrip ring resonator I. INTRODUCTION With the development of modern wireless communications, there is an increasing demand of compact, low profile, multi- band monopole antennas. Recently, Wireless Local Area Networks (WLANs) and Worldwide Interoperability for Microwave Access (WiMAX) is extensively being used in commercial, medical and industrial sectors. Bluetooth, on the other hand is very successful in handheld and portable devices. To cover all the frequency bands, broadband antennas can be used. In order to avoid potential interference between nearby communication systems, antennas need to be designed that would work in only the desired frequency bands. Many planar antennas have been reported, but they operate mostly in dual and triple frequency bands [1]-[6]. Thus for quadruple frequency band operation, one possible way is to use two dual- or triple- band antennas to achieve the four operating bands. But the effective antenna size increases. One possible solution is to use a single antenna system which would work in all the four frequency bands without compromising on performance and notching the undesired frequency bands. This paper presents such an antenna system which operates in four frequency bands; 2.369 – 2.485 GHz, 3.113 – 3.938 GHz, 4.714 – 5.392 GHz and 5.658 – 6.386 GHz. II. STRUCTURE AND DESIGN OF ANTENNA The geometry of the proposed microstrip fed monopole antenna is illustrated in Figure 1. The antenna is fed with 50Ω microstrip line and is designed on a Taconic TLY 5 substrate, dual layered PCB. The substrate has relative dielectric constant ε r =2.2 and height h=0.787mm. The thickness of PEC metal on both the surfaces is 0.0035mm. Microstrip Feeding Technique is easy to fabricate, simple to match by controlling the thickness of the transmission line width and rather easy to model. The required width (w f ) of the microstrip feeding line is calculated for a characteristic impedance Z0=50Ω [7], }] 61 . 0 39 . 0 ) 1 {ln( 2 1 ) 1 2 ln( 1 [ 2 r r r f B B B h w ε ε ε π − + − − + − − − = (1) where r Z B ε π 0 2 377 = W L wf Wo Lo Wi Li Ts Ts Wj Lg gap RLi RWi RLo RWo Wr Wrr Fig. 1: Proposed antenna geometry (a) Top view, (b) Bottom view Microstrip Ring Resonators, integrated in a planar monopole antenna can be used as band-stop filters [8]. The notched frequency in a loop resonator can be approximated by eff eff g r L L nc nc f ε ε λ ) ( Δ + = = (2) where 2 1 + ≈ r eff ε ε = Effective relative dielectric constant , n= Mode Number, λ g = guided wavelength, c= Speed of Light in Free Space, L= Perimeter of the rectangular ring. ΔL has been considered due to the coupling effect between the two ring structures and the ring to ground. Figure 2 shows a typical geometry of a dual open loop rectangular ring.