Wideband microstrip patch antenna with planar PBG structure

Microstrip antenna technology has found applications in a wide variety of military and commercial applications due to its many advantages (e.g. low profile, light weight, ease of fabrication, low cost). However, a narrow impedance bandwidth is a major drawback for this type of antenna. Thus, much of the research on microstrip antennas has been devoted to various techniques for increasing the impedance bandwidth. An electrically thick substrate with a low dielectric constant increases the bandwidth, but the impedance locus becomes increasingly inductive, making impedance matching difficult. In addition, surface waves are excited that lower the antenna efficiency. One technique used to suppress surface wave propagation in the antenna substrate to achieve better performance is photonic band gap (PBG). We describe a square patch with a wide impedance bandwidth. The multiple resonance technique has been used to obtain wider the bandwidth for this single feed antenna. The antenna also provides circular polarization within the bandwidth with a good axial ratio (AR). This patch has further been investigated by integrating it with a planar PBG structure; a significant improvement has been observed in both impedance and AR bandwidth. Antennas and the PBG structure are modeled with the finite-difference time-domain (FDTD) method.