A planar plasma antenna with a dielectric coat

Subject and Purpose. The coefficients of surface wave energy transformation to radiation and the radiation patterns are calculated for an open structure like a planar longitudinally inhomogeneous plasma layer located in between a metal layer and a dielectric layer.

Methods and Methodology. Using the spectral decomposition method, the field of the considered open structure is decomposed in a set of functions descriptive of surface and spatial waves, ending up with a system of integral equations for the decomposition coefficients which determine amplitudes of the transmitted, reflected and scattered waves and, also, radiation patterns. The system of equations is solved in the case that the plasma density changes fast. The coefficients of energy transformation to radiation are found depending on the plasma density gradient for different electric lengths of the plasma inhomogeneity sections, various electric thicknesses of the plasma layer and various thicknesses of the dielectric coat.

Results. Examples are presented when the surface wave energy fraction transformed to radiation reaches 40…45%.This value increases with increasing permittivity of the dielectric coat and decreases as the dielectric coat reduces in thickness. The typical radiation pattern represents a single narrow lobe at an acute angle. As the plasma density gradient at the end of the plasma column rises, the radiation pattern maximum moves towards the surface wave propagation direction and the beam width decreases.

Conclusion. A planar plasma antenna model like a longitudinally heterogeneous plasma layer in between a conducting plate and a dielectric plate has been studied. A high efficiency is observed for the surface wave energy transformation to radiation at mainly an acute angle direction.