Experimental study of the effect of ground width for millimetre-wave multilayer coplanar waveguides in ceramic multichip module technology

Abstract

This study presents the accurate characterisation and detailed experimental study of the effect of ground-plane width and suppression of higher-order parasitic modes extending the frequency of operation up to 110 GHz for multilayer conductor-backed coplanar waveguide lines, fabricated in cost-effective thick-film multichip module (MCM) technology. The coplanar waveguides (CPWs) and components have been realised on multiple layers of dielectric onto a ceramic substrate using straightforward and cost-effective photoimageable thick-film process, demonstrating a very low loss of <0.2 dB/mm at 80 GHz for a finite ground CPW and extremely low loss of <0.1 dB at 76 GHz for CPW layer transitions, which are better than many reported results for MCM technologies. Further, the effective dielectric constant (ɛeff) and characteristic impedance (Zch) are extracted from two-port S-parameters measured on a single-line and by conversion to ABCD parameters, to investigate the practical effect of ground-plane width on CPWs on a multilayer ceramic substrate and to facilitate realisation of a cost-effective millimetre-wave MCM.