Parametric study of PBG ground planes in microstrip transmission lines

Photonic bandgap structures (PBG) are periodic structures in 1, 2, or 3 dimensions which, can prevent the propagation of electromagnetic waves in certain directions for certain frequencies [1]. The properties of these structures are defined by their type of symmetry, material, and by the shape and period of the structure. These periodic structures can be drilled through the dielectric or etched in the ground plane. Etching of holes in the ground plane makes the design much simpler to fabricate. It has been shown that by etching circular holes in the ground plane of a transmission line, a filter can be created with a stopband that is a function of the period of the holes [2]. In this paper, the properties of PBG ground planes in microstrip transmission lines is studied in detail. The effective epsilon values are calculated and compared with simulated values. Finally, a new PBG filter with a wide stopband is shown along with the measurement results.