Anisotropic Circularly Polarising Graded Index Lenses Enabling High Gain CP Antennas

This paper presents the theory and design of a circularly polarising lens utilising anisotropic metamaterials. This design combines the functionality of a lens and a polarisation converter into a single device which cuts down on cost, size, weight and material losses. Theory of the design is presented along with a simulated demonstrator. Anisotropic metamaterials are utilised to create a 90° phase shift between orthogonal wave components to generate circular polarisation. The lens can be fed with a wide range on antenna sources angled at a 45° offset. An example lens was designed in the K-band (18 - 30 GHz) and was capable of achieving high directivity values, between 22.8 dBi and 23.3 dBi, with a wide circular polarisation bandwidth of 9.8 GHz.