# Spiral-Resonator-Based Frequency Reconfigurable Antenna Design for Sub-6 GHz Applications
## 1 Introduction
A frequency reconfigurable multiband antenna design for microwave sensing applications is presented by [PERSON] et al. in 2017 [18]. The reconfigurability has been achieved using PIN diodes to switch operating frequency range between 1.4-1.73 GHz, 4.75-5.72 GHz, 6.3-6.78 GHz, and 8.31-8.90 GHz. In the following comparison, the aspects and contributions of this paper are highlighted in comparison to the study mentioned in reference [19] titled \"A dual-band frequency reconfigurable MIMO patch-slot antenna based on reconfigurable microstrip feed-line\". This study presents a novel frequency-reconfigurable antenna design for sub-6 GHz applications. The reconfigurability is achieved by altering the electrical length and shape of the antenna using diodes or switches. In contrast, the referenced study [19] focuses on a dual-band MIMO patch-slot antenna that employs a reconfigurable microstrip feed line to achieve frequency reconfigurability. The proposed frequency reconfigurable antenna is designed specifically for sub-6 GHz applications, targeting a broader range of frequency bands relevant for modern wireless communication systems. The referenced study [19] focuses on dual-band operation, catering to specific frequency bands without the wide coverage provided by our design. Our proposed antenna utilizes a spiral-resonator-based structure, which enables versatile frequency reconfigurability for various operating states. In contrast, the referenced study employs a patch-slot antenna with a different geometry and reconfigurable feed line to achieve dual-band performance. The proposed structure employs diodes or switches to dynamically alter the electrical length and shape of the spiral resonator, allowing frequency reconfigurability over a wide range of frequencies. The referenced study [19] utilizes a reconfigurable microstrip feed line for its dual-band operation, which is different from our approach. In study, the proposed reconfigurable antenna is well suited for sub-6 GHz applications, making it highly relevant for various wireless communication systems, including 5G and IoT devices. The referenced study's dual-band MIMOantenna [19] is tailored for specific frequency bands, potentially limiting its versatility and applicability to broader frequency ranges. This study presents a novel frequency-reconfigurable antenna design based on spiral resonators for sub-6 GHz applications. The reconfigurability is achieved by dynamically altering the electrical length and shape of the antenna using diodes and switches. In contrast, the referenced study [20] focuses on a compact slot antenna with frequency reconfigurability for wireless applications. The design approach and mechanism for reconfigurability differ significantly from this study. In this paper, the frequency-reconfigurable antenna is specifically designed for sub-6 GHz applications, targeting a broader range of frequency bands relevant for modern wireless communication systems. The referenced study [20] focuses on a specific frequency band or wireless application, which could limit its versatility compared to our design. Additionally, this study employs diodes and switches to dynamically alter the electrical length and shape of the spiral resonator, allowing frequency reconfigurability over a wide range of frequencies. The reconfigurability mechanism used in the referenced study [20] has been based on different principles, such as varactor diodes or other tunable components. In addition, the PIN diodes are remotely controlled by the IoT to enable reconfigurability. In the study conducted by [PERSON] et al., frequency reconfigurability has also been applied with the NodeMCU kit based on IoT technology [21]. A suitable design has emerged for RF energy harvesting applications at resonant frequencies of 1.8 GHz, 2.4 GHz, 3.5 GHz, and 4.5 GHz. An IoT-controlled triple-band frequency reconfigurable antenna is outlined by [PERSON] et al. in 2021 [22].