Compact Ultra-Wideband Circularly Polarized Crossed-Dipole Antenna with Wide Angle Coverage

This letter presents a compact ultra-wideband circularly polarized (CP) crossed-dipole antenna with enhanced axial-ratio beamwidth (ARBW) and half-power beamwidth (HPBW). It consists of four modified arms which are fed by vacant-quarter phase delay rings to excite CP radiation. Four parasitic elements are utilized rotationally between the dipoles and the reflector. Not only does inducing vertical currents on the parasitic patches excite additional impedance resonance to realize an ultrawideband operating, but also reinforced radiation is obtained to improve the ARBW and HPBW. The experimental results show that the proposed antenna realizes a dB impedance bandwidth of 134.3% and a 3 dB axial-ratio (AR) bandwidth of 115.0%, while holding a compact volume of 0.25 lambda(L) x 0.25 lambda(L) x 0.09 lambda(L) (lambda(L): wavelength at the lowest operating frequency). Furthermore, an HPBW and ARBW of more than 110 degrees and 160 degrees are realized within a broad operating band of 67.5% and 55.0%, respectively.