Dispersion characteristics of coplanar waveguides on a cylindrical substrate

Due to their major advantage of conformability to curved surfaces, many studies of printed circuits and antennas on a cylindrical substrate have been reported. We extend the study of conformal printed circuits to two novel types of cylindrical coplanar waveguides (CPWs). The configurations of the outside and inside cylindrical CPWs, which can be applied in the design of conformal microstrip circuits or in feeding cylindrical printed antennas, are shown. For the study a full-wave approach is applied, and accurate expressions of the dyadic Green´s functions for the two different structures shown are derived and used in a Galerkin´s moment-method calculation. Theoretical results of the frequency-dependent effective dielectric constant of the cylindrical CPW with various curvatures are calculated and analyzed, and the curvature effect on the effective dielectric constant is discussed. To verify the accuracy of the theoretical results, several cylindrical CPWs were fabricated and measured.