Resonance frequencies of annular microslots

Ring-shaped microslot structures have in recent years gained increasing interest as planar antenna elements. This fact, is connection with their potential use as frequency defining elements or filters in specific MIC applications, justifies the need for an efficient method to determine the resonance frequency of the dominant mode of the annular microslot as its characteristic quantity. Using a proven variational method an expression for this quantity has been derived and extensive numerical results have been produced embracing a large range of dielectric constant values (ε_r={1.00, 2.32, 9.80, 16.00}) and geometrical parameter values relevant for pertinent practical design practice. The results are presented with the azimuthal order n (ring circumference/wavelength) as the parameter. Experimental results support the numerical data