Design of Electromagnetic Bandgap (EBG) structures for polarization sensitive wireless communications

In this paper, the polarization sensitive characteristics of Electromagnetic Bandgap (EBG) structures are discussed. EBG structures are used as a ground plane in modern antenna design due to their high-impedance and in-phase reflection behavior. Some wireless communication applications (such as satellite) are polarization sensitive and require a great care in designing the ground planes of the antennas being used. If a traditional Perfect Electric Conductor (PEC) ground plane is used then communication link will fail due to the polarization inverting properties of it. In this work a special type of EBG ground plane is designed for applications which use circularly polarized antennas for communication purposes. A phase difference of approximately 180 degrees, between the orthogonal (x and y) components of the electric fields of the incident electromagnetic wave, is obtained by using a cross-sheet via in the proposed EBG. This phase condition is the basic requirement for EBG structures employed in Circular Polarization (CP) applications. The phase difference preserves the sense of polarization of the incident waves being reflected from the proposed ground plane. The relative phase angle of the x and y polarized components of the E-fields is adjusted by varying the corresponding length of the x and y-arms of via. This parametric analysis is done till the phase-difference is fine-tuned to 180 degrees. The proposed EBG structure can be used in clockwise and counter clockwise circularly polarized, low-profile antenna designs. The electromagnetic analysis of the structure is carried out using Finite Difference Time Domain (FDTD) method.