Mutual coupling reduction in waveguide-slot-array antennas using electromagnetic bandgap (EBG) structures

The application of an electromagnetic bandgap (EBG) structure as a tool for reduction of mutual coupling in planar waveguide-slot-array antennas (WSAA) is investigated for the first time. First, surface-wave suppression was demonstrated by placing an EBG array over the ground plane of a linear 1 × 4 waveguide-slot-array antenna. Two 1 × 4 waveguide-slot-array antennas were then put next to each other, with the EBG array over the conducting plane separating them, and up to 10 dB reduction in mutual coupling was observed. Based on these achievements, a planar 2 × 4 waveguide-slot-array antenna was designed using the EBG array to reduce mutual coupling. The EBG array compensated for the undesired frequency shift due to mutual coupling through surface-wave suppression. In addition, the radiation patterns of the EBG-loaded antenna remained almost the same as for the unloaded antenna, with a 1 dB increase in antenna gain. Finally, EBG-loaded and simple 2 × 4 waveguide-slot-array antennas were fabricated, and simulation results were compared with measurements, with good agreement. As a key feature of this approach, a planar waveguide-slot-array antenna could be constructed by designing a linear antenna and then forming an array from multiples of the antenna, without the need for any new design, by imposing the EBG structure to reduce the mutual coupling between the adjacent waveguides.