# Spiral-Resonator-Based Frequency Reconfigurable Antenna Design for Sub-6 GHz Applications
## 1 Introduction
The proposed antenna structure is designed for ISM band, X band, and microwave sensing applications by altering the PIN diode states. Furthermore, an IoT-based NodeMCU unit is used for controlling the PIN diode conditions. On the other hand, [PERSON] et al., is depicted an IoT-based novel reconfigurable bandpass filtering antenna structure in 2019 [24]. In that study, the proposed antenna has three different operating frequency bands by changing the PIN diode states. The IoT-based CDAC Cmote device is utilized to transmit data from the fabricated antenna and CDAC Cmote device. The proposed spiral resonator loaded reconfigurable antenna differs from the radiating structure presented in [28]. Firstly, the proposed antenna is more compact in size compared to the one in [28]. Additionally, although [28] demonstrates good agreement between the measured and simulated results, discrepancies can arise due to the soldering process and measurement circuitry. To overcome this limitation, the biasing circuitry is eliminated through the utilization of SPDT switch. As a result, the proposed antenna offers broader operating frequency band compared to [28]. Moreover, the proposed structure exhibits the frequency reconfigurability feature by incorporating the split ring resonators and spiral resonators, as compared with the conventional structures. In 2016, a U-shaped patch antenna was presented and analyzed by [PERSON] et al. [34]. The radiation pattern of the antenna was reconfigured via a stepper motor and Arduino microcontroller. As seen from the literature survey, IoT-controlled reconfigurable antenna structures have been designed and analyzed for various applications in recent years. The primary contribution of this study lies in the design and implementation of a remotely controlled compact frequency-reconfigurable antenna structure, utilizing spiral resonator loaded split-ring resonators, specifically for sub-6 GHz applications. This approach of incorporating spiral resonators and split-ring resonators, along with the utilization of Single Pole Double Throw (SPDT) switches controlled via Arduino, enables dynamic frequency reconfigurability over a wide range of frequencies. To the best of our knowledge, such a combination of spiral resonators, split-ring resonators, and remote control using SPDT switches and Arduino for sub-6 GHz applications has not been explored or addressed in existing literature. This novel design fills a significant research gap, providing a compact and versatile antenna solution suitable for various IoT and modern wireless communication systems operating within the sub-6 GHz frequency range. By introducing this cutting-edge technology and methodology, we aim to pave the way for new possibilities in the field of frequency-reconfigurable antennas, particularly in the context of sub-6 GHz and IoT applications. The remote-control capability offered by Arduino enhances the practicality and ease of use, making the proposed antenna highly relevant and applicable to a wide range of scenarios where adaptability to different frequency bands is essential. In this study, a novel frequency reconfigurable antenna is designed to meet multi-access network integration in a single device. Two different switches are used in the antenna to provide frequency agility features. Moreover, a DC biasing network is applied to isolate DC switching signal from the input RF signal. To obtain better numerical calculation and measurement results, PIN diodes are numerically calculated by touchstone file including one-port S parameters information. Then, how to control and monitor IoT-based frequency reconfigurable antenna remotely is also depicted. The simulation and measurement results of the antenna performance parameters are addressed to highlight the contribution of this study. Hence, the proposed novel antenna is also compared with previous studies published in the literature for frequency reconfigurability feature in the frequency range of sub-6 GHz. Finally, the proposed and future works are discussed.