Toward Dual-band Circularly Polarized Antenna for High-precision Marine BeiDou Satellite Navigation Application — Improvements of Antenna Structure and Feed Network

In the paper, a circular polarized (CP) antenna operating at dual-band is proposed, which has the features of wide 3-dB axial ratio beamwidth (ARBW) and backward cross-polarized radiation suppression. Stacked circular patches with capacitive-coupled feeding are adopted as the primary radiators that operating at dual-band. To widen the 3-dB ARBWs and realized the suppression for backward cross-polarized radiation at the two bands, the radiation patches are surrounded by slotted ground plane, two circles of bent metal branches and four shorting pins. Besides, a modified wideband quadrature four-feed network which has amplitude imbalance less than 1dB and phase differences imbalance within ±5° is designed to provide CP excitations for the dual-band CP antenna. Measurements indicate that the fractional bandwidth for 10-dB impedance bandwidth and the 3-dB CP bandwidth are 35.5% and 47.1%, separately. The RHCP gains is over 5.6dBic at both two bands. The 3-dB ARBWs are 234° at 1.207GHz and 196° at 1.561GHz, respectively. While, the FBRs are more than 18.5dB and 20dB, separately. The proposed antenna shows attractive features including wide bandwidth, high gain, and good CP performance with anti-multipath, appearing as a good candidate for high-precision marine navigation application.