Metamaterials (MMs) are sub-wavelength periodic resonant structures that exhibits unusual properties such as backward wave propagation, reverse Doppler effect, negative refractive index [11,12].
The demand for low-cost, high gain compact antennas that can be designed for electronic and radio-frequency components has made patch antennas an innovative and attractive alternative option in modern wireless communication. In wireless communication technology, everyone wants to reduce the traffic of the channel and try to give as much high speed as they provide to their customers. The reason is to develop this technology because in previous technologies there is narrow bandwidth, high losses, low gain. In this paper, the authors designed a millimeter-wave reconfigurable Vivaldi antenna using a power divider and achieved a gain of around 4.725dB − 7.987dB [1].
However, a microstrip patch antenna by using truncated textured ceramic substrate is designed with a gain of 5.5 dB [2]. The polarization technique is an orientation of the electric field, by tracing the electric field vector, we can identify the polarization of EM waves. Similarly, the author presents an idea by which an antenna can be developed by cross-polarization suppression at a low elevation angle for a compact circularly polarized (CP) microstrip antenna. At the outer of the CP antenna, a meander line ring cavity (MLRC) structure was introduced by the author, and the magnitude of gain 5.3dB was obtained [3]. The other principal was introduced by so many researchers using to simulate the microstrip antenna is PSOAM waves generation using Yagi CAA. The author designed a 1–8 Wilkinson power divider and the result of peak gain achieved is 1.9db [4]. In some designs two pairs of compact microstrip patch antenna were fabricated by the developer for a dual unit retinal prosthesis operating multiple frequencies and after fabrication 4dB peak gain was obtained [5]. For high gain, an array antenna introduced the main advantage to array antenna is the value of gain is measured w.r.t to other technologies. In some research papers a dual-band 2x1 microstrip antenna was designed by the author with a rectangular slot defected to the ground substrate with two different substrates and the peak gain was measured is 4.26–5.52 dB [6]. The symmetrical structure (DGS) in the form of L was implemented in a circular and some different patch antenna with resonant at the second WLAN band. This is used to achieve lower frequency band applications such that Bluetooth etc. The peak gain of 4.4 dB by using this implementation was measured [7]. Dielectric resonator fabricated which helps to increase gain and efficiency in this simulation two cylindrical holes were inserted over the antenna into the dielectric resonator thus 4.79 dB gain was the peak gain was measured by the author [8].
STRUCTURE DESIGN OF THE UNIT CELL
The proposed unit cell consists of one modified square-shaped closed-loop resonators (CLRs) printed on top of the dielectric surface while bottom is backed by copper layer. The used substrate is FR4 Epoxy (εr = 4.4, tanδ = 0.02) with thickness of 2.8 mm as shown in Fig. 1(a). The thickness of the bottom and top layers are 0.018mm with a conductivity of 5.8×107 S/m, the thickness of the substrate layer is 2.8mm. And the total thickness of the metamaterial absorber is 2.836mm. Figure 1(b) shows the 3-D perspective view of the unit cell of the proposed structure.
Dimensions of the proposed metamaterial absorber are given below: Top view of unit cell structure with dimensions: a = 35, b = 32, c = 7, w = 2.5, g = 1.5 (unit: mm).