A Broadband Circularly Polarized Filtering Magnetoelectric Dipole Antenna

This paper presents a broadband circularly polarized (CP) filtering magnetoelectric (ME) dipole antenna. Two cross-placed ME dipoles and a delay line are used to produce circularly polarized radiation properties. And a pair of identical inverted “L” type parasitic elements are placed vertically around the ME dipole in the $\mathrm{- 4 5}{ }^{\mathrm{0}}$ direction, effectively introducing another circularly polarized radiation frequency to broaden the axial ratio (AR) bandwidth. By etching grid slot in the ground plane and employing step impedance resonator (SIR) at the microstrip feeding line, two radiation nulls at the high frequency band are generated, and a radiation null at the low frequency band emerged due to the inherent characteristic of the ME dipole, then a good band-pass filtering response is produced. The simulated results show that the impedance bandwidth at $\mathrm{- 1 0} \mathrm{dB}$ is 46.2% (3.06 GHz-4.90 GHz), the AR bandwidth is 31.9% ($3.53 \mathrm{GHz}-4.87$ GHz), and the average gain in the passband is 6.95 dB.