Envisioning an Endfire Circularly Polarized Antenna: Presenting a Planar Antenna with a Wide Beamwidth and Enhanced Front-to-Back Ratio

Abstract

In this article, a novel design approach for widening the beam width and enhancing the front -to -back ratio of planar endfire CP antennas was proposed and investigated. The resulting antenna consists of a semicircular magnetic dipole and a V-shaped open loop. The tradeoff in design between the azimuthal beamwidth and the front -to -back ratio was theoretically revealed by an approximate equivalent sources model. The combination of a semicircular magnetic dipole and a rotated V-shaped open loop can successfully lead to a broadened azimuthal 3 -dB AR beamwidth of up to 115° and an enhanced average front -to -back ratio of 13.7 dB. These results imply that a nearly perfect CP, hemispherical endfire beam was satisfactorily realized. The resulting operating bandwidth of the antenna is as wide as 10.5% in fraction. The proposed antenna exhibits a relatively small size, a simple planar, nontumstile structure with 11 design parameters, and a superior hemispherical end fire beam in parallel to its plane, compared to other planar end fire CP counterparts. If a higher directivity is required, several existing techniques, such as using a thicker low -loss substrate, loading with dielectric rods and lenses [32], and introducing an additional reflector [36], can be alternatively employed. Because of a series of unique merits, especially its broad AR beamwidth, the proposed antenna is promising for use as a feeding element, an array element, or a hand-held antenna in various wireless systems such as satellite communication, navigation, RFID, and so on. The revealed design approach is believed to be useful for the development of other types of planar wide-beamwidth CP antennas.