This invention is about a novel microstrip patch antenna which is capable of operating in two different frequency bands. The antenna provides a broad beam serving a hemispherical coverage. The antenna consists of 3 layers: metal-dielectric-metal (ground-substrate-patch). The dielectric layer is a few hundred mils thick sitting on top of a thin metallic square ground plane. The patch can be of a circular or a square shape. A thin parasitic ring surrounds the patch and plays an important role of generating the second frequency band. There is no direct metal contact between the ring and the patch itself. The patch can be fed by two orthogonal probes to generate circular polarization (CP) or a single probe to generate linear polarization (LP). Although circular and square patches are demonstrated here, the shape of the patch is not limited to these two particular shapes. This is also the case of the shape of the ground plane which can take other shapes than square. The patch can work as a stand alone radiator or as an element of a multi-element array. The performance of the ringed patches can be described by 1) the return loss and 2) the radiation pattern. The circular patch operates at 1.575 GHz and 1.227 GHz. The square patch operates at 1.679 GHz and 1.365 GHz. The operating frequency bands are controlled by the geometry of the ringed patch. Other frequency bands may be obtained by optimizing the patch dimensions. A 3.274 dB gain is achieved at 1.575 GHz and a 1.897 dB gain is achieved at 1.227 GHz. A 4.28 dB gain is achieved at 1.679 GHz and a 1.944 dB gain is achieved at 1.365 GHz. Both right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP) were recorded. The cross-polarization (LHCP) component is at least 10 dB smaller than the co-polarized component (RHCP) at the boresight direction.
Patent Number: 7,385,555
Date Issued: June 10 2008