Analytical Solutions and Characteristics for Shielded Asymmetrical Coplanar Stripline and Its Transition to Rectangular Waveguide

Analytical solutions and characteristic analysis for the shielded asymmetrical coplanar stripline (SACPS) are presented. The SACPS consists of a metal shielding cavity and an asymmetrical coplanar stripline with finite-boundary substrate. Analytical closed-form expressions for the quasi-TEM electrical parameters including the relative effective permittivity, phase velocity, and characteristic impedance are obtained by the conformal mapping method. The SACPS has the characteristics of supporting the quasi-TEM mode propagation, easy for shunt and series surface mounting of active and passive devices, no need for via holes, without radiation loss, and well suited for millimeter-wave applications. The transition from SACPS to rectangular waveguide is designed based on the analytical solutions and characteristics of the SACPS. The accuracy of the derived analytical formulas is verified through comparisons between the full-wave and the quasi-static analyses. Based on the experimental data analysis, differences between the full-wave and the quasi-static analysis are less than 3% and 6% for the characteristic impedance and the relative effective permittivity, respectively. The given analytical solutions are accurate, fast for calculation, and can be directly used in the computer-aided design for the SACPS.