Novel Frequency-Reconfigurable Antennas with Ring Resonators and RF Switches: Enhancing Versatility and Adaptability in Wireless Communication Systems  
[PERSON]  
1 Electrical-Electronics Engineering Department, Adana Alparslan Turkes Science and Technology University, Adana 01250, Turkey; [EMAIL_ADDRESS]
2 Electrical-Electronics Engineering Department, Izmir Katip Celebi University, Izmir 35620, Turkey; [EMAIL_ADDRESS] or [EMAIL_ADDRESS]  
[PERSON]  
2 Electrical-Electronics Engineering Department, Izmir Katip Celebi University, Izmir 35620, Turkey; [EMAIL_ADDRESS] or [EMAIL_ADDRESS]  
[PERSON]  
1 Electrical-Electronics Engineering Department, Adana Alparslan Turkes Science and Technology University, Adana 01250, Turkey; [EMAIL_ADDRESS]  
requires changing its internal structure using various techniques [9; 10]. Several critical parameters must be carefully considered, such as gain, efficiency, radiation pattern, and impedance matching for all states. Reconfigurable antennas can be classified according to their functional characteristics, such as operating frequency, radiation pattern, and polarization [11]. Frequency-reconfigurable antennas play a crucial role in sub-6 GHz and wireless applications due to their ability to adapt to different frequency bands and communication standards. These antennas provide precise frequency control, which allows them to adjust their resonant frequencies accordingly [12]. This ability is important in wireless communication systems that require antennas to operate at different frequency bands. The importance of frequency-reconfigurable antennas in sub-6 GHz and wireless applications is highlighted by several research studies. For example, [PERSON] et al. [13] presented a cactus-shaped frequency-reconfigurable antenna for sub-10 GHz wireless applications. The antenna utilizes PIN diodes as electrical switches to achieve reconfigurability, enabling operation in four different frequency ranges [13]. This demonstrates the potential for frequency-reconfigurable antennas to adapt to various wireless applications. In the context of 5G technology, frequency-reconfigurable antennas have gained significant attention. [PERSON] et al. [14] reports the design of a multiband compound reconfigurable 5G antenna for sub-6 GHz wireless applications. The antenna can operate in multiple frequency bands, including ISM, WLAN, Wi-Fi, and Airport Surveillance Radar (ASR) bands [14]. Furthermore, the use of frequency-reconfigurable antennas can improve the working flexibility and space utilization of terminal equipment [15]. By utilizing a single antenna module that can cover multiple sub-6 GHz working bands, the need for multiple antennas can be eliminated, leading to more efficient and compact wireless devices [15]. The potential for frequency-reconfigurable antennas to address the spectrum crunch at microwave frequencies is also worth noting. The underutilized millimeter wave (mm Wave) frequencies, typically ranging from 30 to 300 GHz, can be explored for cellular applications [16]. However, mm Wave frequencies face challenges such as severe path loss and absorption/scattering by gases. Frequency-reconfigurable antennas offer a solution by allowing for the efficient utilization of available frequency bands, including sub-6 GHz bands [16]. [PERSON] et al. makes significant contributions to 5G sub-6 GHz applications and wireless communications [17]. They propose a novel antenna design that achieves dual-band operation and dual-circular polarization. The antenna's ability to operate in multiple frequency bands allows for compatibility with different 5G frequency bands, ensuring wide coverage and flexibility in wireless communication systems [17]. The antenna design utilizes a single-fed configuration, which simplifies the feeding network and reduces the complexity of the antenna system. Furthermore, the study demonstrates the use of a dielectric resonator antenna (DRA) in the proposed design.