Analysis and Design of Shielded Suspended and Inverted Microstrip Lines for Microwave Applications

Based on a numerical solution of Laplace's equation by the finite element method (FEM), we present the electromagnetic (EM) analysis of shielded, suspended and inverted microstrip lines. This technique is adapted to study the complex configuration of the line's system which does not have a simple analytical solution. The EM parameters are evaluated, and design curves are presented. The obtained results are compared with the available published data and good agreement is found. As an application, the design results of two 20 dB directional couplers are presented using coupled shielded suspended and inverted microstrip lines. Our numerical model remains valid to all configurations of structures that propagate the fundamental TEM mode or quasi-TEM mode.