Wide bandwidth measurement of complex permittivity of liquids using coplanar lines

A technique for measurement of complex permittivity of dielectric materials, using coplanar waveguide (CPW) cells is presented. A complete solution of the forward and inverse problems, based on a quasi-TEM propagation model, is given. Unlike other methods, the inverse problem can be solved without the use of iterative or graphical techniques, by simple matrix inversion. The model accounts for the various discontinuities along the line. Several advantages result from this approach. Measurement over a broad frequency range is possible, limited only by dispersive effects. It is suitable for solids not amenable to machining for cavity measurements; and there need not be any contact