# A New Low-Cost Compact Antenna for the 2.45 and 5.8 GHz ISM Bands
## 2 Dual-Band Antenna Design
### Antenna Design Methodology  
To size the antenna, a frequency of 2.45 GHz is initially chosen. In fact, an antenna whose dimensions are obtained from a given frequency is capable of operating in higher frequency bands. As with any antenna, there is not just one resonant frequency but many multiples of it. From [31], considering the previous parameters and the low frequency (i.e., 2.45 GHz), the dimensions of the patch (Lp \(\times\) Wp) and the ground plane (Ls \(\times\) Ws), here identical to those of the substrate, are equal to 37.23 mm \(\times\) 28.81 mm and 46.23 mm \(\times\) 38.41 mm, respectively. One technique for making other main resonances appear (which can also be repeated on even and odd multiples) and minimizing the antenna size would be to insert slots on the antenna. Our aim is to introduce the second 5.8 GHz frequency band and optimize the antenna's performance. The optimization objective was constrained by the conditions (i) to (iii) set out above. Figure 2 shows the four different steps in the antenna design process. Initially, in step 1 (Figure 2a), the ground plane is modified by reducing its length, followed by the insertion of a pair of 1 mm \(\times\) 1 mm square notches at the intersection of the patch and the supply line. These notches and the partial ground plane are proposed to improve \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Antenna** & **Values** & **Antenna** & **Values** & **Antenna** & **Values** \\
**Parameters** & **(mm)** & **Parameters** & **(mm)** & **Parameters** & **(mm)** \\ \hline Lsu & 40 & Lp1 & 9.2 & Lf3 & 0.5 \\ Wsu & 24 & Lp2 & 16 & Lf4 & 1 \\ Lpa & 33 & LS1 & 2.5 & Wf1 & 3.4 \\ Wpa & 18.5 & Wf4 & 2.8 & Wf2 & 0.5 \\ Lgr & 26 & Wp1 & 6.8 & Wf3 & 0.3 \\ C1 & 3 & Wp2 & 10.3 & Wf5 & 1 \\ C2 & 1 & Ws1 & 3 & Lg1 & 2 \\ C3 & 1 & Ws2 & 2.1 & Wg1 & 3 \\ R1 & 9 & Lf1 & 3 & Wg2 & 1 \\ R2 & 5 & Lf2 & 1 & Wg3 & 2 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Dimensions of antenna geometrical. the antenna's reflection parameters and minimize its size, always inspired by the authors' work in [30]. In step 2, a circular ring is introduced (Figure 2b) on the patch, and a second pair of 1 mm \(\times\) 0.5 mm rectangular notches is then inserted in the lower part of the feed line. Three 2 mm \(\times\) 2 mm square slots and two circular slots are inserted in the upper part of the ground plane and symmetrical to the central ring in the third step, respectively, in Figure 2c. The final antenna is obtained by adding three slots to the patch, two of which are rectangular (Figure 2d). The ground plane is also modified by creating four other square slots in its upper part. The idea behind the shape of the ground plane is to extend its upper edge to enhance the electromagnetic diffraction effects of its boundaries, which will contribute to increasing the electromagnetic radiation of the patch. The slots are inserted on the patch to prevent or reduce the propagation of surface waves (that affect the antenna's bandwidth and radiation efficiency) and to create a new current distribution that would influence frequencies in terms of reflection coefficient levels and improve the antenna's bandwidth. The circular and rectangular slots are inserted to considerably increase the distance that the surface current would travel across the patch. Indeed, a current flowing from one end of the patch to the other is generally blocked by the slots. To bypass them, it will have to take a longer path than the one without the slots inserted, which would increase the length covered by the current. The result would be a lengthening of the wavelength or a reduction in the antenna's operating frequency. This technique can be used to reduce operating frequencies or shift the frequency of resonance points. Figure 2: The design evolution of the proposed dual-band antenna in four steps.