# Hybrid Mode Reconfigurable Antenna with V-Shaped Extrudes for Cognitive Radio Applications
## 1 Introduction  
For a single application, antennas with a specified frequency range and radiation pattern may be utilised. As a result, applications requiring multiple radios use more antennas. The more antennas there are, the more space they take up, the more likely there is to be interference between neighbouring antenna elements, the more expensive the installation will be, and the more complicated the hardware platform will be. Antennas that are smaller, less complex, less expensive, and less prone to interference are needed for new wireless applications. Reconfigurable antennas are utilised to achieve these properties. Multiple reconfigurable antennas can operate as one antenna [1, 2, 3]. Reconfigurable antennas enable a variety of wireless services since they are specially crafted to work across a broad frequency spectrum. By adjusting the antenna's radiated field with the proper efficient aperture, the frequency of the device can be set [1]. The internal mechanism of reconfigurable antennas, which consists of radio-frequency (RF) switches, tuneable materials, and mechanical actuators to permit the deliberate rearrangement of RF current distribution and allow for reversible variations in the antenna characteristics, is used to provide a dynamic response [2, 3]. When changing needs must be met, this switchable capability is used to improve the performance of the radiator [3]. Compound reconfiguration, in which oneantenna can change numerous performance parameters, has recently received attention in research. A reconfigurable antenna most often has the capability to alter any of its performance factors, including frequency, polarization, and radiation pattern. The sub-6 GHz spectrum is becoming increasingly crowded due to the present rapid development of wireless communication technology. The CR system that senses the spectrum environment and distributes services to the vacant frequency channels has drawn significant consideration due to its capacity to boost spectral efficiency [4; 5]. A novel UWB antenna with switchable, notched frequency band characteristics has been designed and realized. A single p-i-n diode is used to obtain the rejection band characteristics. The designed antenna emits electromagnetic radiation between 2 and 11 GHz. The antenna may switch its emission in the 5-6 GHz range due to a single p-i-n diode located on the back [6]. A small, dual-linearly polarised 2-port antenna has the ability to change the orientation of its polarisation base from vertical to horizontal, 0 or 90 degrees, to slanted, \(\pm\)45 degrees, as discussed in [7]. Over a shared impedance bandwidth, radiation patterns for a resonant, square-spiral-shaped patch antenna are changed using the dual Radant MEMS (SPST) single-pole, single-throw switches, SPST-RMSW-100, studied in [8]. Two C-shaped monopole antennas consisted of a short line. Two RF switches were inserted to provide a reconfigurable frequency for dual-band operation with a monopole array to provide strong isolation for WLAN applications that have been explored [9]. Numerous frequency-reconfigurable antennas have been studied [10; 11; 12; 13; 14; 15; 16; 17; 18], including monopole [11] and patch antennas [12; 13; 14; 15]. Additionally, research is being conducted to determine how MEMS switches can be used to reconfigure dual-polarised antennas [15]. For cognitive radio network applications, a specific frequency-reconfigurable design has been discussed which comprises a monopole with a reconfigurable integrated filter on the ground. The antenna may be used to sense the wide band and then select the most suitable option among the four sub-bands to function in. It can be utilised in either a wideband mode or one of four sub-bands. Results from measurements and simulations have also been reported, and a reassuring degree of consistency could be shown, supporting the suggested strategy [16]. For polarization reconfiguration, a rhombus-shaped patch antenna with a Y-shaped feed structure was discussed [19].