A Wideband Circularly Polarized Filtering Array Antenna Using Dual-Layer Circular Cross Slotted Patch

The array element consists of a feeding structure designed as a 2-way power division with a 90° phase difference and a dual-layer patch structure. An aperture-couple driven patch spatially placed between the parasitic patch and feeding structure is used to introduce magnetic coupling with parasitic patch for a resonant mode at high frequency and a radiation null. Meanwhile, four arc-shaped patches fitted with four shorting via surround the driven patch to generate electric coupling with it. It allows to achieve a resonant mode at low frequencies and a radiation null to improve the bandwidth. Then, a four-way sequential rotation feed network is designed with the same amplitude and a 90° clockwise incremental phase, which is fed a 2×2-element circularly polarized filtering array antenna. The results demonstrate that the array achieves a 3 dB gain bandwidth of 22.9% and the axial ratio bandwidth of 22.0%.