A dual band circularly polarized microstrip antenna on an EBG substrate

A common property of microstrip antennas is that the antenna element launches surface wave modes in addition to the radiated fields. Suppression or reduction of surface waves improves antenna efficiency and reduces side lobe levels. EBG materials, also known as photonic crystals, can offer a solution to the surface wave problem. A novel circularly polarized (CP), single-fed microstrip antenna on an electromagnetic bandgap (EBG) substrate is presented. The antenna consists of a stacked structure of almost square patches and an EBG substrate for the lower patch. The proposed design has a reduced antenna size as compared to the conventional CP microstrip antenna at a given operating frequency and is of light weight. The impedance and axial ratio bandwidths are large and CP radiation quality is excellent over the entire upper hemisphere. The antenna features about 11 dBi gain. The proposed antenna is suitable for Global Positioning System (GPS) applications.