Abstract: This paper contains, developing and employing methods to reduce the mutual coupling between elements of an antenna array. The utilization of electromagnetic band-gap (EBG) structures is an attractive way to reduce surface wave excitation in printed antenna geometries so to mitigate the mutual coupling problem. This paper investigates the performance of a microstrip antenna phased array embedded in an EBG. The band-gap feature of surface-wave suppression is demonstrated by plotting variations of the transmission coefficient S12 with frequency and dispersion diagram. The antenna design is verified by High Frequency Structural Simulator (HFSS), the simulating results show that the EBG design approach is a good candidate for a reduction in mutual coupling at certain frequencies between radiator elements, which in turn increases antenna directivity. Its band-gap feature of surface-wave suppression is demonstrated by exhibiting the near field distributions of the electromagnetic waves. The mutual coupling of microstrip antennas is parametrically investigated, including the E and H coupling directions, different substrate thickness, and various dielectric constants. It is observed that the E-plane coupled microstrip antenna array on a thick and high permittivity substrate has a strong mutual coupling due to the pronounced surface waves. Therefore, an EBG structure is inserted between array elements to reduce the mutual coupling.

Keywords: Electromagnetic band-gap (EBG), High Frequency Structural Simulator (HFSS), microstrip antennas, mutual coupling, surface wave.