Analytic and Electromagnetic Investigation of Millimeter Wave Membrane Supported CPWs Processed on High Resistivity Silicon

This paper investigates a series of membrane supported millimeter wave transmission lines up to 110 GHz. The structures were fabricated using high resistivity silicon micromachining (wet etching). Three approaches, based on full-wave electromagnetic simulations, analytic closed form equations and equivalent circuit were used in the investigation process. The results were validated by the experimental results for different test structures. The analytic equations were inserted in a Matlab routine and the effective permittivity and characteristic impedance were plotted for various geometries. These same geometries were then simulated electromagnetically in CST Microwave Studio. A comparison between the two approaches is made. The effective permittivity of a membrane supported coplanar waveguide (CPW) line was extracted from measurements and it is in very good agreement with the electromagnetically simulated data.