Resonance phenomena in conductor-backed asymmetrical coplanar strips

Abstract

The ground strip of CBACPS represents a patch antenna supporting unwanted parallelplate (PP) modes causing numerous resonances. For typical monolithic-microwave integrated circuits in finite substrates and packaging enclosures, these resonance frequencies lie within the microwave frequency region. In order to suppress coupling into these PP modes, several mode coupling suppression methods are proposed, simulated and tested in the frequency range 0.05 to 50 GHz. These methods include variation of line parameters, suspension of the substrate, application of a superstrate with a high dielectric constant and the use of slow-wave structures. It is shown that the resonance frequencies are accurately estimated by our model, which considers the excitation of the first and second PP modes. Furthermore, the mode coupling suppression schemes are verified by measuring the S-parameters of the fabricated CBACPS lines. This thesis reports the first use of slow-wave electrodes as a mode coupling suppression method for coplanar structures; it is shown that the best mode coupling suppression is achieved by the use slow-wave electrodes along with narrow-width shorted ground strip.