Axial Ratio Enhancement of a Single-Layer Microstrip Reflectarray

This letter presents a new approach for the enhancement of the axial ratio (AR) of a single-layer circularly polarized reflectarray antenna based on a circular microstrip patch with phase delay-line stubs unit cell. The AR improvement is achieved by inserting insets around the two stubs, changing the orientation of one of them and using a mirror symmetry arrangement. Two prototypes have been designed, fabricated, and tested to proof the proposed concept in K-band. A good agreement has been obtained between numerical simulations and experimental results. The measured results confirm a remarkable AR improvement with values below 1 dB and 3 dB gain and AR bandwidths larger than 23.7%.