Broad-range microstrip patch refflectarray element loaded with multiple L-shaped slots

A single-layer microstrip patch unit element, which is loaded with eight concentric L-shaped slots, is proposed for reflectarray design. In this case, the lengths of the inner and outer slots are varied concurrently to function as the phase-shifting geometrical parameters. The reflection characteristics of the element are analyzed using the waveguide method, and the simulation results have been verified with experiments. A broad reflection phase range of 631.83° with slow gradient has been successfully achieved with the use of the slotted patch with constant size. Parametric analysis has been performed and it is found that the S-curve can be easily fine-tuned by changing some of the design parameters.