Side Effect Characterization of EBG Structures in Microstrip Patch Antenna

The unwanted side effect of EBG structures when integrated with microstrip antenna is investigated in this paper. The main goal of using EBG structures in microstrip antenna is to achieve better gain and efficiency, lower side-lobes and back-lobes levels, and better isolations among array elements, by suppressing surface wave modes. The two dominating side effects may be named as parasitic loading effect and cavity effect. The parasitic loading effect of EBG structure causes the multi resonance antenna resulting in larger bandwidth. Cavity effect on the other hand, is due to reflecting energy from EBG toward antenna and results in a larger Q value and so decreasing the bandwidth. These two side effects are characterized in this work and the EBG structure parameters and number of EBG rows is related to these effects. The design parameters of EBG structures can be managed such that the parasitic effect of EBG structure can be the dominating effect and consequently results in larger bandwidth. This parametric study is implemented in to a microstrip antenna integrated with conventional mushroom-like EBG structure in E plane. According to our results, there is an optimal design for EBG unit cell parameters and number of rows so that in addition to surface wave reduction, a larger bandwidth is achieved.