Dual-Band CP Antenna With a Dual-Ring Cavity for Enhanced Beamwidth

A dual-band circularly polarized (CP) antenna with enhanced beamwidth is proposed in this letter. Stacked cone-patches including a small patch for upper band (1561 ± 2 MHz) and a large one for lower band (1268 ± 10 MHz) are used to achieve the dual-band operation behavior. To widen beamwidth for the two operation bands, a dual-ring cavity is employed for the proposed antenna. The dual-ring cavity is formed by a large ring and a small ring, which are used to improving the beam performance for lower and upper band, respectively. Over the dual-band of interests, the impedance bandwidth (VSWR ≤ 1.5) and the axial ratio below 3 dB are both satisfied. Wide 3 dB beamwidths of about 135 ° and 112 ° at center frequencies (1268, 1561 MHz) of the two bands are obtained, respectively. The high gains at the low elevation (θ = 80°), only about -0.03 dB and -0.57 dB at the two frequency points, are also achieved. With these good performances, the antenna is very suitable for navigation systems applications.