Varying Slot Lengths Strip Loading Squared Dielectric Resonator Reflectarray

a new type of dielectric resonator reflectarray composed of 529 elements covering an area of 276 x 276 cm2 is constructed. The unit cell consists of squared DRA supported on a strip with variable slot length, a dielectric layer and a conducting ground plane. The full phase of 360 degree of the array elements can be obtained by superposition two slot-strip sizes. Two types of feeding were analyzed, the first is center fed reflectarray while the second is offset feed to reduce the feeder blockage and as a result the antenna efficiency is improved. The antenna has 10% bandwidth for 1 dB gain variation is obviously wider than that of conventional reflectarray antenna while the offset fed reflectarray provide better far field pattern with back lobes reduction by -5 dB and side lobe by -2 dB. A rectangular X- band pyramidal horn was used in both reflectarrays which have 23 x 23 elements of with cells separation of 12 mm that less than 15 mm (lambda/2) for avoiding grating lobes. CST microwave studio (finite integral technique) package is applied and compared with microstripes package (transmission line technique) with good agreements between them. The mutual coupling between the feeding horn and the elements of the reflectarray are considered. At 10 GHz, the antenna provides a 3-dB beamwidth of 6 degree with a gain of 28 dB. The antenna bandwidth within 1dB gain variation is found to be 13% and aperture efficiency of 59%.