Ultra-Wideband Vertically Polarized Long-Slot Circular Phased Array

An ultra-wideband (UWB) vertically-polarized (VP) long-slot circular phased array with compact size is presented. The design realizes a quasi-magnetic current sheet array. It consists of just one circular array instead of a typical cylindrical system, which employs multiple circular arrays to achieve radiated fields with the same properties. A 16-element array was fabricated and measured to demonstrate its azimuthally invariant radiating capabilities. Measurement results show that the developed array achieves a wider impedance bandwidth, commendable cross-polarization discrimination (XPD), and a significantly more compact design than previously reported systems. In its omnidirectional mode, the array exhibits a 107.07% bandwidth (VSWR ≤ 2.0) with an XPD level better than 19.5 dB. In its directional mode, the array operates over 100% bandwidth with an XPD level better than 20.9 dB. The prototype exhibits exceptional azimuthal out-of-roundness values - better than 1.3 dB in its omnidirectional mode - and scan-invariant radiation with a maximum deviation of only 0.8 dB in its directional mode.