This paper presents an analytical method to investigate the propagation characteristics of a uniform microstrip line placed on porous substrates. The structure is periodic with a specified unit cell and the substrate is made of cascaded multi-layer dielectric slabs. The proposed method is started by solving wave equation by decomposing Helmholtz operator using appropriate eigen-functions and applying the associated boundary conditions of tangential electromagnetic fields of the unit cell. Then, using Floquet theorem, the equivalent propagation constant of a one-dimensional (1-D) periodic structure is obtained. In addition to, the proposed method is developed for two-dimensional (2-D) structures by a suitable transformation. Several practical structures are considered to verify the accuracy of the proposed method. The comparison of the proposed analytical model and measurement results and those obtained using simulation process provided by High Frequency Simulator Strctures (HFSS) are reported. It is shown that our method can be used for a wide variety of structures to quickly estimate the required parameters with a good accuracy.

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