Investigation of large directivity bandwidth in multilayer resonant cavity antennas

This paper presents results of an investigation carried out on the large directivity bandwidth of a multi-layer all-dielectric resonant cavity antenna (RCA). This RCA comprises of a multi-layer all-dielectric superstructure, which exhibits a measured broadside directivity of 18.1 dBi with an extremely large 3-dB directivity bandwidth of 51%. Unit cell model of the superstructure is studied by employing superstructure reflection model (SRM) and defect cavity model (DCM). This study reveals that by optimising the frequency separation between two positive phase gradients bands generated by resonant cavities, significant improvement in the directivity bandwidth can be achieved.