  Electromagnetic metamaterials, made from arrangements of subwavelength sized
structures, can be used to manipulate radiation. Designing metamaterials that
have a positive refractive index along one axis and a negative refractive index
along the orthogonal axis can result in birefringences, $\Delta n>1$. The
effect can be used to create wave plates with subwavelength thicknesses.
Previous attempts at making wave plates in this way have resulted in very
narrow usable bandwidths. In this paper, we use the Pancharatnam method to
increase the usable bandwidth. A combination of Finite Element Method and
Transmission Line models were used to optimise the final design. Experimental
results are compared to the modelled data.
