A Differentially Fed Dual-Polarized Magnetic Dipole Antenna for Spaceborne Applications

This paper presents a novel differentially fed dual-polarized magnetic dipole antenna with stable radiation pattern, platform independence, wide bandwidth, and robust structure for spaceborne applications. The proposed antenna is formed by a dual-polarized magnetic dipole backed by a specially designed rectangular cavity. The magnetic dipole consists of two perpendicular parallel-plate waveguides with stepped edges to broaden the impedance bandwidth, providing good structural reliability which is critical to spaceborne antennas. A cross-shaped conductor fed by two pairs of capacity coupling feeding probes is utilized to drive the dual-polarized magnetic dipole antenna. The specially designed rectangular cavity has four metal plates in four corners to shape the radiation pattern at E- and H-planes. Furthermore, thanks to the cavity, the size of the conducting platform that the antenna mounted on has limited impact on antenna's electrical performances, particularly the radiation pattern. A prototype is fabricated and tested. Measured results show that the antenna achieves a fractional bandwidth of 18.5% with -10 dB reflection coefficient. The realized gain is about 8.5 dBi. A stable radiation pattern with a 3 dB beamwidth of 70° ± 3° and -4 dBi maximum beamwidth of 152° is observed. The measured cross-polarization is lower than -20 dB within ±65°. Measured results are in good agreement with simulation ones.