A Small Quad-Band Monopole Antenna with Folded Strip Lines for WiMAX / WLAN and ITU Applications

In this article, a small Quad-Band microstrip patch antenna with folded strip lines for WiMAX/WLAN and ITU Applications is presented. This antenna consists eight symmetrical rectangular folded strip lines with 2 PIN diodes, ground plane and dimensions of 15×20×1.6mm 3 . Using PIN diodes integrated within the antenna configuration, the antenna would be able to operate in two modes. The operational frequency bands of antenna are WLAN (2.4/5.2/5.8GHz), WiMAX (3.5/5.5GHz) and ITU-Region 1 allocation (4.3GHz) when diodes=on. In this design approach of antenna, omnidirectional radiation pattern and S11-10dB bandwidths are obtained for all frequency bands. This antenna is fabricated on FR4 substrate with permittivity of 4.4 and loss tangent of 0.024.


I. INTRODUCTION
Recently, the demand for the design of an antenna with triple or multiband operation has increased since such an antenna is vital for integrating more than one communication standards in a single compact system to effectively promote the portability of a modern personal communication system [1].For this demand, the developed antenna must not only be with a triple/multiband operation but also have a simple structure, compact size, and easy integration with the circuit [1].In modern wireless communication systems, multiband antenna has been playing a very important role for wireless service requirements.Wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) have been widely applied in mobile devices, such as handheld computers and intelligent phones [2].Also many efforts in UWB antenna fields have been reported that more descriptions come in [3][4][5][6][7][8][9][10][11].
To design a multiband antenna for multimode wireless communication system, various methods have been explored [12][13][14][15][16].A compact zigzag-shaped-slit rectangular microstrip patch antenna with circular defected ground structure (DGS) is designed for wireless applications [17].A simple microstrip antenna for the radio frequency identification (RFID) applications and WLAN with two operating bands at 2.45 and 5.8GHz [18].A triple-band metamaterial (MTM)-inspired antenna consists of two L-dumbbell-shaped unit cells, feed and partial ground plane for WLAN and WiMAX applications [19].Compact metamaterial inspired triple band antenna for the frequency bands 2.4, 3.5      The radiation patch of the antenna is fed by 50Ω microstrip feeding line.In the fed line an inverted U shape slot is added to better impedance matching.The ground plane of this antenna is designed with the length L g =3mm with the same width of the substrate (W sub ).The radiation pattern in φ=0 ᴼ &90 ᴼ (H-plane) and θ=0 ᴼ &90 ᴼ (E-plane) for 3.5GHz and 5.5GHz frequency bands and D 1 &D 2 =off in Figure (8) indicate the omnidirectionality if the antenna.Also, the simulated H-plane and E-plane radiation patterns for 2.4GHz, 3.5GHz, 4.3GHz and 5.5GHz are shown in Figure (9).These figures illustrate both, co-polarization and cross polarization.Figure (10) represents currents distribution of the antenna for four frequency bands when the diodes are on.
Table 2 presents the comparison between the designed antenna in this article and references [17] to [21].This comparison presents the smallest dimensions and most applications of the antenna designed in this paper compared to the mentioned papers.IV.CONCLUSION In this paper a small Quad-Band monopole antenna with using eight symmetrical rectangular folded strip lines is analyzed for WiMAX/WLAN and ITU applications.In this antenna using two PIN diodes in antenna structure, two modes of operation were obtained.By turning the diodes off the Dual-Band frequency antenna with 3.5/5.5GHzfor WiMAX application and single band frequency of 5.8GHz covers WLAN that the results of reflection coefficient were studied.Also be turning the diodes on, the antenna can be used for WiMAX applications with frequencies 3.5/5.5GHz,WLAN with frequencies 2.4/5.2/5.8GHz and ITU-Region1 allocation with the frequency 4.3GHz that the results of reflection coefficient are presented for this mode.The advantages of this antenna include the simultaneous function of WiMAX/WLAN and ITU with ability to operate in two different modes through the diodes, small dimensions and simple design and fabrication.

( 3 . 5 / 5 .
5GHz) is presented based on IEEE 802.11b/g and IEEE 802.11a standards and also 4.3GHz for ITU-Region1 allocation applications.This design with using two diodes can operate in two different modes, Antenna performance with Quad-Band frequency when diodes are turned on and the performance of antennas in Dual-Band frequency when diodes are turned off.This antenna with a simple design and the use of eight symmetrical rectangular folded strip lines is fabricated on FR4 substrate with small dimensions.

Fig. 1 .
Fig. 1.(a) Top view and (b) bottom view of proposed antenna Using two diodes at the distance of L D in the second strip lines of the patch it is possible to work in two frequency modes, The performance in the frequency bands 3.5/5.5GHzfor WiMAX and the performance in the frequency band 5.8GHz for third band of WLAN when the diodes are off; also the frequency coverage of 2.4/5.2/5.8GHz for WLAN and 4.3GHz for ITU-Region1 allocation when diodes are on.

Figure ( 3 1015 Fig. 3 .
Fig. 3. (a) Side view of the proposed antenna and (b) top and bottom view of fabricated antenna

Fig. 8 .Fig. 9 .
Fig. 8. Simulated radiation pattern of the proposed antenna for D 1 &D 2 =off In the third step presented as step 3 in Figure(2-c), it can be observed that finally by adding two other symmetrical rectangular folded strip lines to patch layer the antenna operate in four frequency bands for WiMAX, WLAN and ITU applications.Optimum dimensions of antenna are presented in Table1.
This step has six symmetrical rectangular folded strip lines obtained by adding two strip lines with the same width and length to the step 1.In this step, a frequency band is added to the antenna performance.