A bidirectional circular polarized array with the same rotation using a special substrate

A novel bidirectional circular polarized array with the same rotation is presented. The array consists of 4 pairs of crossed dipoles. The distance between adjacent elements is λ₀/4 (λ₀ is the wavelength in free space). The radiation elements are fed by the balanced parallel stripline. The adjacent horizontal/vertical dipoles need to be excited out of phase difference for the bidirectional radiation and the adjacent crossed dipoles need to be excited in phase for the circular polarization of the same rotation. To satisfy the special phase distribution, a substrate with dielectric constant of 6.0 is used, which makes the guided wavelength λ_g equals to λ₀/2. The impedance bandwidth (|S₁₁| <; -10 dB) is 9.2% (2.38 GHz to 2.61GHz) and the 3-dB axial ratio bandwidth is 700 MHz (2.05 GHz ~ 2.75 GHz). The bidirectional RHCP gain is about 7.5 dBi.