Vortex Wave Generation With a Truncated Square-Pentagon Antenna Array

This letter presents a compact broadband antenna array with two circular loops featuring different circular-polarized elements rotated sequentially. The inner loop employs truncated square patches, while the outer utilizes truncated pentagon patches. The sequential rotation eliminates the need for phase shifters in the feeding network. The design using truncated square and pentagon elements results in a 12-element demonstration with a radius of only 0.76
λ
₀
.
X
-band simulation and measurement results show simultaneous emission of circularly polarized vortex waves of modes −1 and +2, with an impedance bandwidth of 17% and axial ratio bandwidth of 4.7%.