A wideband circularly-polarized MIMO filtering array antenna using dual-layer circular patch

A novel wideband circularly-polarized (CP) MIMO filtering array antenna with dual-layer circular cross-slotted patch is introduced. The presented element consists of a two-way feeding structure designed with equal amplitude and 90 degrees phase difference, and a dual-layer circular cross-slotted patch structure. An aperture-couple-driven patch is positioned between a cross-slotted patch and a dual-feed structure. It facilitates magnetic coupling to achieve a high-frequency resonant mode and radiation null. Meanwhile, four arc-shaped patches are electrically coupled to the driver patch by surrounding it with four shorting vias to improve the bandwidth. In multiple-input multiple-output (MIMO) wireless systems, a two-port MIMO dual-CP filtering array antenna for the Sub-6 G band is proposed. The design utilizes four proposed CP antenna elements and a dual-port transmission structure. The dual-port transmission structure consists of two sets of T-junction power dividers that are 180 degrees phase shifted with opposite polarization. The dual-CP MIMO filtering array antenna of the impedance bandwidth is 21.8% (3.1 similar to 3.9 GHz). The AR bandwidth is 13.1% (3.3 similar to 3.7 GHz), while the gain bandwidth is 20.1%. Additionally, the isolation between the antenna elements is less than -15.0 dB. The envelope correlation coefficient between its two ports is less than 0.02.