## 2 Materials and Methods  
A 3D view of the proposed superstrate rectangular microstrip patch antenna is shown in Figure 1. The patch antenna has one rectangular cut/cropped section, which helps to achieve a multiband response and a lower reflectance response (\(S_{\mathbf{11}}\)). Two substrate layers of dielectric materials are used to achieve a broader bandwidth. A novel thing introduced in the manuscript is a tooth around the split ring resonator. The design parameters of the rectangular patch antenna, include the length (\(L\)) and width (\(w\)) of the ground plane and the patch are calculated, based upon selecting the height of the substrate (\(h\)), the dielectric constant of the substrate (\(\varepsilon_{r}\)) and the resonating frequency (\(f_{r}\)) [46]. Figure 2 represents the fabricated prototype of the proposed antenna structure. Figure 2a represents a split ring resonator with the tooth. Figure 2b shows a split ring resonator without a tooth. Figure 2c displays the disconnected inner and exterior sides of the patch. Figure 2d represents the connected inner and exterior parts of the patch. Figure 2e,f show the side views of the proposed structure. Figure 2g shows the anechoic chamber during the antenna directivity measurement. Figure 2f displays the reflectance response measurement using a vector network analyzer. The side view of the designs are represented in Figure 3a. The ground layer, the patch, the split ring resonator, and the tooth thickness are 0.35 mm. The height of the substrate layer is 1.5 mm. The dimensions of the rectangular ground layer and the substrates are 66.4 mm. The patch and all of the split-ring resonators are designed in a centered position. The upper view of the antenna is represented in Figure 3b. The first (exterior), second (middle), and third (interior) split-ring resonators are positioned at 8.2 mm, 15.3 mm, and 22.2 mm, from the exterior border, respectively. The width of the SRR is 2 mm. The size of the tooth is 1.5 \(\times\) 1.5 mm\({}^{2}\). The gap between the two terminals of the SRR is 2 mm, and it is placed 32.2 mm away from the exterior border. The distance between the tooth located in the split-ring resonators is, respectively, 4.44 for the first (exterior), 3.78 mm for the second (middle) and 3.4 mm for the third (interior). The top view of the patch is shown in Figure 3c. The patch is kept 5 mm away from the exterior edge. The rectangular patch outer structure (POS) dimension is 56.4 mm. The cropped/cut section in the patch is 2 mm. The patch interior structure (PIS) is 46 mm. The connectors for shorting the PIS with the POS are 2 mm. The connectors are kept 32.2 mm from the antenna's exterior. The antenna's structure is excited by applying the input from a coaxial feed. The coaxial feed is kept 52.8 mm by 13.5 mm away from the exterior. The radius of the coaxial interior is 0.12 mm,and the exterior is 0.43 mm. The ground layer, the patch, the SRR, the tooth and coaxial's interior are made of copper. The coaxial's exterior is made of plastic. Two types of substrate materials are considered Rogers RT Duroid 5880 (E--2.2) and FR4 (E--4.4) [47]. In a SRR, the inductance effect is induced by the circular shape and the capacitance by the space is between two ring terminals. The inductance (\(Ls\)) and capacitance (\(C_{s}\)) per unit length can be calculated by Equations (1) and (2) [48]. \[Ls=\frac{\mu_{0}b}{\sqrt{\pi}}\bigg{[}\text{Log}\bigg{(}\frac{32b}{w\sqrt{\pi }}\bigg{)}-2\bigg{]} \tag{1}\]  
\[C_{s}=\varepsilon\frac{wt}{2g} \tag{2}\]  
where, \(\mu_{0}\) is the free space permittivity (\(\mu_{0}=4\)\(\pi\times 10^{-7}\) N/A\({}^{2}\)), the width of the ring is \(w\), \(g\) is a gap between two split rings, \(b\) is the ring length, the series capacitance is \(C_{s}\), \(t\) is the ring thickness. The RLC circuit of the SRR is shown in Figure 4. The resonating frequency of the proposed design can be calculated using Equation (3) [49].