## 2 Antenna Design and Configuration  
The antenna described in this paper was designed on a Roger 5880 substrate having permittivity (\(\epsilon_{\mathrm{r}}=2.2\)), tangent loss 0.0009, and a thickness of 1.57 mm. A perfect electric conductor (PEC) having 0.035 mm thickness was used to simulate the radiator element, microstrip line, and ground of the antenna. The proposed design of the antenna with front, side, and back views is shown in Figure 1a-c. A 3D view of the proposed antenna is shown in Figure 2. According to the monopole antenna configuration, the length and width were calculated with the help of \(\lambda\)/4 and \(\lambda\)/100 respectively [8], where \"\(\lambda\)\" is the wavelength of the antenna at the center frequency. Table 1 shows the dimensions of all the parts of the antenna. The proposed structure is different from that of simple meander lines. Every rod of the antenna operates at different frequencies because the frequency of the antenna depends on the corresponding wavelength. When the wavelength is small, the frequency will be higher, so the dimensions of the antenna rods are optimized according to the corresponding frequencies. In proposed structure, length \"e\" is different from lengths \"z\", \"q\", and \"x\"; width \"n\" is different from widths \"i\", \"k\", and \"f\", and the space between the meander lines are not same, but rather, are optimized to get a wide bandwidth. The meander line rod with length \"e\" and width \"f\" operates at higher frequencies. Length \"z\" and width \"i\" operate at the middle frequencies, and lengths \"q\" and \"x\" and widths \"n\" and \"k\" operate at lower frequencies. Spaces \"m\", \"j\", and \"g\" play an important role, i.e., mutual coupling at lower and higher bands to get a wide bandwidth. A special type of microstrip line was used, known as a quarter-wave transformer, where the feeding line is divided into two parts, as shown in Figure 1a. In this figure, line d is known as the transition line, which connects the radiating meander lines with an impedance of \(\text{Z}_{\text{L}}=115.74\)\(\Omega\), with a Zo = 70 \(\Omega\) microstrip line. The transition line impedance \"Zr\", transition line width \"c\", and length \"a\" calculations are explained in [27] and [28]. The length of the transition line at the center frequency (21.65 GHz) is 5.2 mm. The impedance of the transition line is 90.01 \(\Omega\) and width c = 1.6 mm. The proposed width of the transition line is the optimized value. In the proposed work, two designing steps were used to get a super wideband result. In the first step, a simple meander line antenna (Antenna 1) without DGS was designed and simulated with the same dimensions as those shown in Table 1. The return loss (dB) at this step is shown in Figure 3a, which operates in frequency range of 2. 95 GHz to 21.15 GHz. This antenna covers the S/C/X and Ku frequency bands. To obtain the K-band and Ka-band frequencies ranges, a defected ground structure was used in the second step of antenna design, which is the proposed antenna (Antenna 2), as shown in Figure 3a. The slot in the ground was etched into the backside of the quarter-wave transformer microstrip line. Due to the use of DGS, the antenna now operates above 30 GHz, as shown in Figure 3a. Figure 1: Proposed antenna (**a**) front view (**b**) side view (**c**) back view. Figure 2: 3D view of the proposed antenna. The physics behind the DGS is as follows: with the help of DGS, the ground plane current distribution will be disturbed. This disturbance will change the transmission line characteristics by including some of the parameters of the slot (capacitance, inductance, and resistance) in the parameters of the transmission line (capacitance, inductance, and resistance). In other words, when the ground plane under the microstrip line is defect, then the microstrip line effective inductance and capacitance will be changed by adding the slot capacitance, inductance, and resistance; therefore, resonance will occur at a certain frequency.