# Implications of Metamaterial on Ultra-Wide Band Microstrip Antenna Performance
## 1 Introduction  
Antennas are considered significant elements of any wireless communication system. An antenna is defined as a metallic structure used for transmitting and receiving signals or radio waves [1, 2]. One of the most popular and utilized antenna types is the microstrip antenna that was first presented in 1950. The microstrip antenna is very prominent due to its small size, low price, simple structure, ease of fabrication and its capability to operate on multiple bands of frequencies; contrarily, it has some significant impediments such as very narrow frequency bandwidth, low efficiency, low power, false feed radiation and poor polarization purity [2, 3]. With the high number of wireless devices in information epoch which depends on information transmission with higher data rate, provision security to consumers and business, increase the number of users, the importance of wideband wireless communication technology has increased rapidly [4, 5]. UWB is defined as the technology of transmitting data over a broad bandwidth; with wireless transmission of \(-10\) dB bandwidth is more than 25% of a center frequency or \(-10\) dB bandwidth equal or larger than 1.5 GHz [6, 7, 8]. In 2002, the Federal Communication Commission (FCC) declared the authorization of using the unlicensed frequency band between 3.1 GHz to 10.6 GHz for commercial communication applications. FCC reserved bandwidth of 7.5 GHz for UWB due to its importance [8, 9]. Due to the necessity of a low-cost solution for microwave communication systems and the growth in wireless applications, the idea of UWB microstrip antennas was getting noticed by researchers. Antenna researchers and designers have focused on variety of challenges in order to overcome the disadvantages of microstrip antennas. [PERSON] et al. [10] presented a hexagonal-shaped patch antenna of added two capacitive loaded line resonators (CLLRs) on the ground plane to achieve UWB bandwidth between 1.1 GHz to 10.69 GHz. Their antenna covers the UWB band from 3.1 GHz to 10.6 GHz and frequencies 2.4 GHz and 9.1 GHz for Bluetooth and radar applications. The designed antenna hasan omnidirectional radiation pattern. [PERSON] et al. (2011) introduced a multiband circular microstrip antenna; their antenna consists of a circular patch and a microstrip feeding line with a notch that produces the multiple bands. A U-shaped slot was embedded onto the antenna patch to achieve band-stop filtering over the frequency range. The antenna has three bands from 1.5 GHz to 2.8 GHz, 3.3 GHz to 4.7 GHz and ultra-wideband characteristics from 6 GHz to 16.10 GHz. The antenna's maximum gain is 4.58 dB, and radiation efficiency is around 86.17%. Furthermore, in ([PERSON] et al., 2011), [PERSON] et al. introduced a double notched self-complementary UWB antenna. It consists of semi-ring with tapered section, T-shaped slot etched in the radiating patch and two C-shaped close to the microstrip feed line. Antenna's frequency bandwidth is between 2.2 GHz and 12 GHz, and the maximum gain is 3.5 dB; with radiation efficiency of 70%. New composite materials were introduced in the microwave and optics applications, known as a metamaterial, having unnatural properties ([PERSON] et al., 2011). Electromagnetic metamaterials are defined as efficient homogenous structures that have properties not found in nature ([PERSON] et al., 2011). In the late 60 s, [PERSON] proposed the idea of the metamaterial existence that had both negative electric permittivity \(\varepsilon\) and negative magnetic permeability \(\mu\) simultaneously. In 1999, split-ring resonators (SRRs) were studied to provide negative magnetic permeability \(\mu\) by [PERSON] (1999). SRR is defined as a sub-wavelength metamaterial structure that displays negative permeability \(\mu\) over a narrow frequency band around its resonance frequency ([PERSON] et al., 2011). A double-ring SRR is another form of SRR, it is made of two concentric rings separated by a gap with splits at opposite sides; in this case, a resonant structure can be obtained ([PERSON] et al., 2011).