Artificial dielectric substrate for microwave applications

This paper presents a new version of an artificial dielectric substrate. The substrate is fabricated as a 2D array of metallic posts separated from the top conductor by a thin dielectric slab. This structure can show a very high effective permittivity. This permittivity depends on the dimensions of the posts, the permittivity of a dielectric material filling the space between the posts, and on the top dielectric slab thickness and permittivity. The thinner is this slab and the higher is its permittivity the higher is the effective permittivity. This artificial dielectric substrate is suitable for designing the microstrip line and circuits based on it. Due to the high effective permittivity, a substantial reduction in the dimensions of microwave circuit elements is possible. The simple analytical model of this structure is presented. The microstrip line on the proposed substrate was fabricated and measured. The measured and calculated effective permittivity is in a good accord. The 3 dB coupler was designed, fabricated and measured by applying the microstrip line on this artificial dielectric substrate