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A wideband perforated rectangular dielectric resonator antenna (RDRA) reflectarray is presented. The array of RDRA are formed from one piece of material. Air-filled holes are drilled into the material around the RDRA. This technique of fabricating RDRA reflectarray using perforations eliminates the need to position and bond individual elements in the reflectarray and makes the fabrication of the RDRA reflectarray feasible. The ground plane below the reflectarray elements is folded to form a central rectangular concave dip so that an air-gap is formed between the RDRA elements and the ground plane in order to increase the bandwidth. Full-wave analysis using the finite integration technique is applied. Three cases are studied. In the first one, the horn antenna is placed at the focal point to illuminate the reflectarray and the main beam is in the broadside direction. In the second one, the horn antenna is placed at the focal point and the main beam is at ±30 degrees off broadside direction. In the third one, an offset feed RDRA reflectarray is considered. A variable length RDRA provides the required phase shift at each cell on the reflectarray surface. The normalized gain patterns, the frequency bandwidth, and the aperture efficiency for the above cases are calculated.

Circularly polarized graphene based transmitarray for terahertz applications is proposed. The characteristics of the graphene material is explained. The cell element of the transmitarray is made of square Quartz cell. Dual circular graphene rings are printed on both sides of the Quartz substrate. The graphene ring radius is varied to change the transmission coefficient phase and magnitude. The effect of the graphene mobility on the transmission coefficient is demonstrated. Transmitarray is composed of 9×9 unit cell elements. A circularly polarized circular horn is used to feed the transmitarray at f=6 THz. The left-and right-hand field components in the Eand H-plane are determined. The variation of the gain and the axial-ratio with the frequency are explained. The peak gain is 18.63 dB and 1-dB gain bandwidth is 6.8%. The transmitarray produces a circular polarization from 5.5 THz to 6.5 THz.

In this paper, linearly polarized transmitarray is investigated as to avoid the usage of multi-layers for improving the bandwidth of transmitarray. The transmitarray is formed from a single dielectric sheet by perforating selected areas of the material. A perforated dielectric layer is divided into square cell elements. Each cell has four holes with the same diameters. Holes with different diameters in the cell elements are used to allow continuous tuning of the transmitted signal's phase over 360 • range with a maximum loss of 3.6 dB at 10 GHz. The transmission coefficient versus the diameter of the holes is calculated by using the finite integration technique. The results are compared with those calculated with transmission line method for verification. The focal-to-diameter ratio of the transmitarray is optimized for lower side lobe level and highest transmitarray gain. A comparison between the transmitarray and the reflectarray with the same aperture area is illustrated.