Effect of placing mushroom electromagnetic bandgap structures at the inset feedline of microstrip patches

Abstract

Placement of mushroom electromagnetic bandgap (EBG) structures at the inset feedline of patch antenna operating at 4.8 GHz is analysed in this study. Proposed design for (i) single patch and (ii) two-element patch array exhibits significant improvement in return loss, bandwidth and mutual coupling loss. Parametric analysis confirms that the optimal position of EBG structures is at a distance of 1.5 mm on both sides of the feedline. It is established that the return loss increases by 8 dB and bandwidth increases by 3.2% for single patch with EBG structures at the feedline. A 6% reduction in antenna size is realised when compared with conventional placing of EBG. Likewise in double patch, placing the EBG structures on either side of the corporate feedline improves the return loss by 2.5 dB and a 12% reduction in size is achieved when compared with customary positioning of EBG. Bandwidth improves by 4.82%. The superior reduction of mutual coupling of double patch with inset edge feed having EBG structures at feedline, in addition to single-column mushroom EBG structures placed between the patches is demonstrated. The mutual coupling loss increases by 3.5 dB and a size reduction of 20% is accomplished. In antenna arrays, EBG structures at the feedline considerably reduce side lobe level and back lobe level and improve directivity, because of optimal radiation patterns. Simulations are validated experimentally.