A broadband planar antenna employing waveguide parallel feed circuit

Planar antennas with a relatively high gain of about 30 dBi have drawn increasing attention due to their ease of installation and aesthetical appearance. The planar antenna comprises of multiple radiators arrayed on a plane. They are roughly classified by the feed method into a series feed type and a parallel feed type. The series feed planar antennas have a simple feed circuit construction. The parallel feed planar antennas mostly use strip lines to constitute a parallel feed circuit. This type of construction has made it possible to realize a very thin antenna for X-band. However, the strip lines, use a dielectric, which provides large dielectric and radiating losses, so they are not suitable to large-scale array structures required at the higher frequency bands. Similarly, they are not suitable for high-power applications, such as transmission antennas, either. We investigate a highly efficient, broadband planar antenna that uses low loss rectangular waveguides with a parallel feed circuit. The antenna is thus compatible with a large array structure while having a high manufacturability and wideband impedance characteristics.