A study of the effect of dielectric materials on a two-dimensional near-field antenna-array probe for sub-wavelength microwave imaging

The effect of a dielectric body on the performance of a near-field antenna-array probe designed for sub-wavelength focusing is presented by computing the fields inside the dielectric using CST Microwave Studio 2010. Simulations were conducted considering an array composed of a centrally fed monopole surrounded by parasitic secondary monopoles (placed less than half a wavelength away) and a dielectric body placed in the proximity of the array. It was found that the dielectric permittivity plays an important role in the two-dimensional sub-wavelength-focused imaging of this array. A comparison with a dielectric-free case for the same geometry is also included to bring out the impact of the presence of the dielectric body. The effect of the dielectric losses is also studied. Results are shown based on rigorous parametric studies that lead to useful guidelines and optimised designs for sub-wavelength focusing inside the dielectric body.