###### Abstract
A dual-band reconfigurable terahertz patch antenna composed of microstrip and graphene backing cavity has been demonstrated by [PERSON] et al. [26]. Patch resonance is used in the proposed antenna, which is defined by interleaved graphene/Al2O3 stacks. Through electrostatic gating on the graphene stack, it can be dynamically dual resonance frequency-tuned across a broad range of frequency roughly 1 THz. The direction of the antenna main beam may be steered with a significant variation range by applying different voltages to the graphene stack. These initial findings are particularly promising for future THz applications, especially THz antenna arrays. [PERSON] et al. demonstrated a tunable THz radiation band antenna, whose resonance frequency and bandwidth can be changed by the applied voltage [27]. The proposed structure offers a wider operational bandwidth and a better match between the photomixer and the antenna. Using an array of split ring resonators (SRR), the bandwidth and radiation properties can be improved. [PERSON] et al. developed a reconfigurable adjustable graphene dipole antenna with excellent impedance stability [28]. This approach provides excellent properties in terms of frequency-reconfiguration, and stable impedance and radiation patterns upon tuning across the entire operation band. These findings hold great promise for future graphene-based monolithic integration of the antenna and THz emitter/detector. Despite the fact that all of these reconfigurable antennas have exhibited a broad range of tunability, the majority of them lack in tuning range or need somewhat sophisticated manufacturing or exotic semiconductor materials. Discrete frequency tuning is another feature of switch-based reconfigurable antennas. Although some simulation results have been reported in the THz range, no reports of actual devices have been demonstrated with tunable frequency and wide band operation. The proposed reconfigurable radiating antenna design is based on the integration of a reconfigurable fractal antenna and electro-optic  
Figure 1: Different techniques of achieving antenna reconfigurability. substrate material. The electromagnetic characteristics of the fractal antenna are manipulated at both the level of fractal geometry, electrical length and dielectric substrate. The designed antenna features multiband responses, in which the geometry and length change create a large frequency shift, whereas dielectric change using polymer dispersed liquid crystal (PDLC) creates fine and/or continuous tuning. The advantages of using PDLC also eliminated the need for LC cells for LC entrainment. This allows a simpler and integrated design because the entire antenna can be fabricated using typical microfabrication. For the future application, we intend to use this antenna design with electronic-based THz devices for a tunable transceiver system. Therefore, a fully integrated system is preferred. Various iteration stages of the fractal Hilbert curves are shown in Figure 2. It may be observed that geometry at an iteration stage can be obtained by combining four scaled down copies of the previous iteration, connected with three additional line segments. For example, the geometry of Order 2 can be thought of as four copies (nearly halved) of the geometry with Order 1 (arranged in different orientations). The design also utilizes rectangular shape patterns that can easily reconfigured by the switch on and off using the proposed transistor switch system. To design a proper structure for any antenna, it is desired to calculate the different parameters, and then their dimensions are arranged for the specific bands. For an appropriate design, we have to find the exact dimensions of different elements, such as the width and the length of the structure, top layer, ground layer and many more. The unit cell parameters are shown in Figure 3. The geometric parameters are listed in Table 1. The perturbed fourth order Hilbert curve is used to reduce the losses by shifting the large and smooth frequencies to the higher and lower band.