POLARIZATIONS OF CROSSED-DIPOLE ANTENNA LOADED WITH DIFFERENT NFRP ELEMENTS

In this paper, the polarizations of single-feed crossed-dipole antennas loaded with different near-field resonant parasitic (NFRP) elements are investigated. The antennas are placed above a metallic reflector for a broadside radiation pattern. Meander line with an arrowhead-shaped ending is applied in all arms of the crossed-dipole and NFRP elements for the compactness. By adjusting the ending sizes of the NFRP element, the polarization of antenna can be right-hand circularly polarized (RHCP) — linearly polarized (LP) — left-hand circularly polarized (LHCP). For validation, two antennas with RHCP and LHCP performances are implemented and measured. The RHCP antenna yields a |S11| < −10 dB bandwidth of 1.454–1.668 GHz (214 MHz) and a 3-dB axial ratio (AR) bandwidth of 1.525–1.585 GHz (60 MHz). The LHCP antenna yields a |S11| < −10 dB bandwidth of 1.475–1.702 GHz (227 MHz) and a 3-dB AR bandwidth of 1.535–1.580 GHz (45 MHz). Moreover, both antennas yield a good broadside radiation with a gain of > 6.0 dBic and a radiation efficiency of > 65% across their operational bandwidth.