A Wideband Polarization-Reconfigurable Vivaldi Antenna Array on a Cylindrical Substrate

In this letter, a wideband polarization-reconfigurable antenna array is proposed. Unlike the traditional array, the proposed one is composed of four Vivaldi elements connected in end-to-end form, supported by a hollow cylindrical substrate manufactured by three-dimensional printing. For the determination of the optimal distribution of excitation for different polarization states, the method of maximum power transmission efficiency is used, thereby making the array be able to switch between left-handed circular polarization, right-handed circular polarization and linear polarization along any azimuthal angle. The final optimized array size is π × 47² × 36 mm³ (π × 0.60² × 0.46λ₀³ = 0.521λ₀³, where λ₀ is the wavelength in free space at 3.8 GHz). The simulation and measurement results show that the impedance bandwidth is from 2.5 GHz to 5.0 GHz (66.6%, active |S₁₁| < −10 dB) for all polarization states, and the maximum realized gain is always greater than 8.2 dBi/dBic. In addition, the axial ratio bandwidth (AR ≤ 3 dB) can cover the entire impedance bandwidth and stable gain can also be maintained within the working band. More importantly, for applications with different gain and size requirements, the number of antenna elements can be changed easily to achieve similar wideband performance and polarization reconfigurability with stable in-band gain.