# Spiral-Resonator-Based Frequency Reconfigurable Antenna Design for Sub-6 GHz Applications
## 4 Conclusions  
In this study, a novel frequency reconfigurable antenna design for sub-6 GHz applications is proposed, featuring a unique combination of antenna elements and control mechanisms. The antenna consists of an outer split-ring resonator loaded with an inner spiral resonator, and its reconfigurability is achieved through the remote control of the PIN diode or SPDT switches. Experimental measurements and numerical computations validate the antenna's performance, highlighting its superiority over existing alternatives in terms of compactness, wide operating frequency range, and cost-effectiveness. Compared to the existing literature, the proposed antenna design offers several significant advancements. Firstly, the antenna operates in broadband or tri-band mode, allowing for versatile applications. The utilization of PIN diodes or SPDT switches as RF switches provide efficient frequency reconfigurability. Furthermore, the omnidirectional radiation pattern of the antenna enhances its suitability for wireless communication systems. The experimental results demonstrate the antenna's effectiveness on an FR-4 substrate, confirming its performance and validating the numerical calculations. The antenna's compact \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Ref.** & **Dimension (mm\({}^{2}\))** & **Operational** & **Reconfigurable** & **Components** & **Frequency Range** \\
**(mm\({}^{2}\))** & **Mode** & **Technique (\#)** & **Control Method** & **(GHz)** \\ \hline
[19] & \(120\times 60\) & Dual-band & Varactor diode (1) & Manually & 1.3–2.6 \\ \hline  & & & & & 2.29–2.39, \\
[20] & \(27\times 25\) & Single-band, dual-band & PIN diode (3) & Manually & 4.40–4.52, \\  & & & & 4.29–4.57, \\  & & & & 5.71–5.93, 2.3–2.4, \\  & & & & 5.64–5.96 \\ \hline
[21] & \(50\times 50\) & Single-band & PIN diodes (2) & IoT-based & 2–5, 2–3.7, \\  & & & & NodemCU Unit & 1.8–3.4, 1–3.7 \\ \hline
[22] & \(25\times 32\) & Single-band, Tri-band & Utilizing slots in the radiating patch & Manually & 2.85–5.35, 3.18–3.82, \\  & & & & 4.15–5.42 \\ \hline
[23] & \(70\times 70\) & Single-band & Varactor diode (2) & Manually & 2.45–3.55 \\ \hline
[25] & \(36\times 14\) & Single-band & PIN diode (2) & Manually & 2.03–2.17, \\  & & & & 2.37–2.51 \\ \hline
[26] & \(50\times 45\) & Dual-band, triple-band & PIN diode (2) & Manually & 2.2–6 \\ \hline
[27] & \(30\times 28\) & Dual- and quad-band & PIN diode (1) & Manually & 1.7–1.9, 2.7–3, \\  & & & quad-band & PIN diode (1) & 5.7–5.9, 8.8–9.5, \\  & & & & 5.6–6.1, 9.3–9.6 \\ \hline
[28] & \(30\times 30\) & Wide-, dual-, and tri-band & PIN diode (2) & Manually & 1.8–4.5 \\ \hline
[29] & \(48.19\times 38.36\) & Single-band & Variable capacitance (6) & Manually & 2.41–5.27 \\ \hline
[30] & \(33\times 16\) & Single and dual-band & PIN diodes (3) & Manually & 2.1–5.2 \\ \hline  & & & & 2.01–2.16, \\
[31] & \(15.5\times 32\) & Dual-band & PIN diodes (3) & Microsoft-based IoT & 3.18–3.589, \\  & & single-band & & device & 2.97–3.54, \\  & & & & 2.81–3.18, 2.59–2.99 \\ \hline
**This work** & **22 \(\times\) 16** & **Broadband or triple-Band** & **PIN diodes (2)** & **Manually or** & \\  & & & **orRF switch (2)** & **Arduino** & **2.08–5.53** \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Comparison of the proposed antenna with other frequency reconfigurable antenna studies in the literature. size and easy control mechanism make it highly suitable for integration into various devices such as access points, gateways, smartphones, and IoT kits. In terms of application potential, the proposed design shows promise in a wide range of areas, including Wi-Fi (IEEE 802.11 a/n/ac), Bluetooth (5 GHz), ISM (5 GHz), 3G (UMTS), 4G (LTE), wireless backhaul (4G and 5G networks), WLAN (IEEE 802.11a/n/ac/ax), and 5G NR n1 band. Its versatility and compatibility with different wireless communication standards open up new opportunities for deployment in various scenarios.