These absorbers exhibit high sensitivity and can operate in the terahertz frequency range. Additionally, the study explores the use of different resonator structures, such as Jerusalem crosses [29], T-shaped gaps [30], and ring-strip resonators [31], to achieve the desired absorption characteristics. The research also investigates the impact of substrate etching on the sensitivity of metamaterial absorbers [32]. Overall, the study provides valuable insights and design guidelines for the development of metamaterial-based antennas with enhanced sensing capabilities. The study in [33] explores the use of metamaterials (MMs) in antenna design and highlights their potential contributions and implications. It also discusses various applications of metamaterials in antennas, such as achieving high efficiency in amorphous silicon solar cells [34], overcoming the diffraction limit in super lenses [35], and designing hepta-band and multi-band metamaterial absorbers for sensing applications [26; 36]. Furthermore, the study presents several examples of metamaterial absorbers with specific characteristics, such as polarization insensitivity [37; 38], wide-angle absorption [38], high Q-factors [39], and multiple absorption bands [31; 40]. These examples demonstrate the potential of metamaterials in designing antennas with desired properties and functionalities. Taking everything into account, the switching element is of utmost importance in the design of frequency-reconfigurable antennas. It enables the antenna to adapt to different frequencies, improves spectrum efficiency, enhances system flexibility, and allows for compact and integrated designs [41]. The selection of the appropriate switching element is crucial for achieving optimal antenna performance and meeting the requirements of the target wireless communication systems. PIN diodes are commonly used for frequency reconfigurability in antennas due to their fast switching speed and low power consumption [42; 43]. One approach is to place the PIN diodes in proximity to the ring resonators. By controlling the biasing states of the PIN diodes, the electromagnetic coupling between the ring resonator and the antenna can be adjusted, thereby changing the antenna's resonant frequency. The PIN diodes can be connected in series or parallel with the ring resonators, allowing for different configurations and switching behaviors. By selectively biasing the PIN diodes, the coupling between the ring resonators and the antenna can be modified, resulting in different resonant frequencies and frequency reconfigurability. In addition to this, RF switches provide fast switching capabilities and are compatible with high-frequency applications [8]. In this approach, RF switches are used to control the coupling between the ring resonators and the antenna. By activating or deactivating specific RF switches, the electromagnetic coupling can be modified, resulting in frequency reconfiguration. The RF switches can be connected in series or parallel with the ring resonators to achieve the desired switching behavior. By controlling the state of the RF switches, the coupling strength between the ring resonators and the antenna can be adjusted, enabling the antenna to operate at different frequencies. In both cases, the ring resonators act as frequency-selective components, allowing for frequency reconfigurability in the antenna design. The specific configuration and placement of the ring resonators, PIN diodes, and RF switches depend on the desired performance objectives, the antenna structure, and the targeted frequency bands. Hence, it is worth noting that the choice between PIN diodes and RF switches depends on various factors such as switching speed requirements, power consumption limitations, reliability considerations, and integration compatibility with the antenna design. Designers need to carefully evaluate these factors to select the most suitable combination of ring resonators and switching elements for achieving frequency reconfigurability in antenna designs.