A broadband dual circularly polarized u-slot patch antenna and its array

A broadband dual circularly polarized U-slot patch antenna element is proposed. By using thick substrate and dual-feed U-slot, the operating bandwidth is broadened. Dual circular polarization is realized by a feeding branch-line coupler. The element and an active phased array composed of 6 elements are simulated. Simulation results show that the bandwidth of 9-dB return loss and 6-dB axial ratio within θ < 60° is over 14% for the element with an overall size of 0.36λ0 × 0.36λ0 × 0.09λ0 without any air gap, where λ0 is the free space wavelength at the center frequency of the operating band. Scanning range of the phased array covers ±60° with gain fluctuation below 6 dB and axial ratio less than 6 dB.