# Compact Broadband Antenna with Vicsek Fractal Slots for WLAN and WiMAX Applications
## 1 Introduction  
With fast progress in wireless technology systems, there is a strong request for antennas with low profiles, compact dimensions, planar geometry and especially the ability to provide a large impedance bandwidth for WLAN and WiMAX applications in several bands, such as 2.4-2.5/3.6/4.9-5.9 GHz and 2.3/2.5/3.3/3.5/5/5.5 GHz, respectively [1; 2; 3]. Microstrip antennas are the best type of antennas that meet these requirements due to their low weight, easy miniaturization, portability, installation flexibility, good performance and low manufacturing costs [4; 5]. In the literature, various structures of microstrip antennas are suggested to shield WLAN and WiMAX applications. Most of these antennas are slotted patch antennas fed bya coplanar waveguide (CPW) technique, such as CPW-fed monopole antennas, or a fractal antenna approach. A monopole antenna with a slot and dual ring resonator in the ground plane was proposed in [6] to achieve a triple band at 2.5, 3.7 and 4.6 GHz for WLAN and WiMAX applications. According to [7], a CPW-fed hexagonal shaped patch antenna was designed to achieve three bands i.e., 0.4, 1.2 and 1.75 GHz. These bands were obtained by inserting H-tree fractal slots in the radiating elements. Similarly, in [8], a Hilbert fractal slot was inserted in an octagonal radiator to operate in WLAN and WiMAX applications, and it offered a dual band at 2.48 and 5.68 GHz with a bandwidth of about 0.7 and 3.55 GHz, respectively. A novel CPW rectangular antenna with a cantor fractal slot was developed in [9]; it shielded two bands of about 1 and 1.7 GHz at resonant frequencies 3 and 5.1 GHz. Likewise, in [10], a compact antenna for UWB notched applications was developed; it covered a bandwidth from 3.1 to 10.6 GHz, with a rejected band from 2.4 to 2.484 GHz, for WLAN applications. On the other hand, the defected ground structure DGS approach can be applied. A monopole antenna consisting of a rectangular ring and a fork-shaped strip with a defected ground plane was developed in [11] to generate three bands for WLAN and WiMAX applications at 2.5, 3.5 and 5.5 GHz. Thereafter in [12], a rectangular radiator with defected ground structure was suggested, offering three resonant frequencies of 2.40, 3.5 and 5.8 GHz which shield the WLAN and WiMAX bands. References [13; 14; 15] additionally propose antennas for WLAN and WiMAX applications using an asymmetrical feed line. In ref. [13], a compact antenna consisting of three monopoles with different lengths and an asymmetrical feed line was suggested to achieve four bands of about 0.17, 0.16, 0.17 and 0.15 GHz for WLAN and WiMAX applications. [PERSON], in [14], developed an asymmetric CPW antenna with a split ring for two bands for WLAN and WiMAX at 2.46 and 3.51 GHz with bandwidths of about 0.17 and 0.15 GHz, respectively. An inverted L- shaped strip in the radiator, fed by an asymmetric CPW, was proposed in [15]; it offered a wide bandwidth of about 3.3 GHz which covers the WLAN and WiMAX bands at 5.725-5.85 GHz and 3.3-3.7 GHz, respectively. Furthermore, antennas for WLAN and WiMAX applications based on the metamaterial approach are presented in references [16; 17; 18]. In ref. [16], a compact antenna consisted of a utilizing complementary split ring resonators (CSRRs) placed in the radiator to reject four bands for WLAN and WiMAX applications at 3.4, 4.1, 4.8 and 5.6 GHz. [PERSON] proposed, in [17], a broadband antenna composed of two interspaced ring resonators as radiator elements printed on FR-4 substrate, and the overall size of the antenna was 60 \(\times\) 90 \(\times\) 1.6 mm\({}^{3}\). The antenna offered two bands of about 0.7 and 1.3 GHz at 2.4 and 5.8 GHz. A CPW-fed metamaterial antenna was proposed in [18] to support WLAN and WiMAX applications at 2.4/5.5 GHz and 3.5 GHz bands, respectively. The authors in [19] developed a MIMO antenna comprised of two spider-shaped radiators printed on FR-4 substrate sized 50 \(\times\) 37 mm\({}^{2}\) to shield WLAN and WiMAX bands at 2.43, 3.83, 4.4 and 5.8 GHz.