# A Compact Triple Band Antenna Based on Multiple Split-Ring Resonators for Wireless Applications
## 3 Results and Discussion
Figure 10 illustrates the radiation patterns of the proposed multi SRR-Based antenna at frequencies of 2.6 GHz, 3.5 GHz and 6.2 GHz. As can be seen, the radiation patterns are omnidirectional in the E and H planes, with the antenna achieving a maximum gain of 3.2 dB at 6.2 GHz. The radiation patterns of the proposed antenna with multi SRRs were simulated with CST Studio Suite 2019 software and validated with HFSS 15.0 software. A strong correlation was observed, highlighting the design's reliability. Figures 11 and 12 and the corresponding Tables 4 and 5 show the effects of the variation of the geometrical parameters W2 and W4 on parameter S11 of the proposed  
Figure 10: Comparison of simulated HFSS and CST radiation pattern distributions of the proposed multi-SRR-based antenna at (**a**) 2.65 GHz, (**b**) 3.5 GHz and (**c**) 6.2 GHz. Table 6 presents a comparative analysis between a conventional rectangular patch antenna (Figure 3a) and the proposed compact multiband antenna (Figure 3e), evaluating size, operating frequency, bandwidth, gain and efficiency. A key advantage of the proposed design is its significant miniaturization--from 60 \(\times\) 50 \(\times\) 1.6 mm\({}^{3}\) in the conventional antenna to just 23 \(\times\) 24 \(\times\) 1.6 mm\({}^{3}\), achieving an 81.6% size reduction. Despite its compact form, the proposed antenna supports multiband operation at 2.5 GHz, 3.5 GHz and 4.5-7.84 GHz, making it suitable for a range of wireless communication standards, whereas the conventional design is limited to a single band centered at 2.5 GHz. In terms of bandwidth, the proposed antenna demonstrates substantial improvements, achieving 14.55% at 2.5 GHz, 14.28% at 3.5 GHz and 54.13% across the 4.5-7.84 GHz range. This contrasts sharply with the conventional antenna's narrow 2.41% bandwidth, which restricts its applicability in wideband or dynamic environments. The proposed multi-SRR-based antenna also achieves acceptable gain levels of 1.5 dBi, 2 dBi and 3.1 dBi across its resonant bands. Although there is a slight reduction in peak gain and a more noticeable drop in directivity due to the smaller radiating aperture, these limitations are offset by a substantial increase in radiation efficiency--from 35.7% in the conventional design to over 70% across all bands in the proposed antenna. This performance enhancement is largely attributed to the integration of split-ring resonator (SRR) structures, which effectively increase the current path without enlarging the antenna's footprint. Additionally, SRRs help suppress substrate losses--a common issue with FR4 as a material--thereby enabling high efficiency and robust performance in compact, multiband configurations. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Parameter**} & **Conventional Patch** & \multirow{2}{*}{**Proposed Antenna**} & \multirow{2}{*}{**Trade-Off Analysis**} \\  & **Antenna** & & \\ \hline
**Antenna dimension (mm\({}^{3}\))** & 60 \(\times\) 50 \(\times\) 1.6 & 23 \(\times\) 24 \(\times\) 1.6 & Significant size reduction \\ \hline
**Electrical size (\(\lambda^{3}\))** & 0.5 \(\times\) 0.4 \(\times\) 0.01 & 0.19 \(\times\) 0.2 \(\times\) 0.01 & \\ \hline
**Miniaturization in (\%)** & - & 81.6 &
\begin{tabular}{c} Achieved via proposed \\ Multi SRR technique \\ \end{tabular} \\ \hline
**Operating Frequency** & 2.5 & 2.5, 3.5, 4.5\(-\)7.84 & Multiband functionality \\ \hline
**Bandwidth in (\%)** & 2.41 & 14.55, 14.28, 54.13 &
\begin{tabular}{c} Improved bandwidth in all \\ bands \\ \end{tabular} \\ \hline
**Peak Gain in (dBi)** & 1.87 & 1.5/2/3.1 & Slightly reduced gain \\ \hline
**Directivity (dBi)** & 6.35 & 3.11, 3.2, 4.52 &
\begin{tabular}{c} Significant reduced \\ directivity \\ \end{tabular} \\ \hline
**Radiation efficiency in (\%)** & 37.7 & 69.1, 75.9, 72.1 &
\begin{tabular}{c} Higher radiation efficiency \\ despite FR4 losses \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table}