A Dual-Circularly Polarized Monofilar Helix Phased Array Antenna

This letter proposes a monofilar helical dual-circularly polarized (DCP) phased array antenna. An axial mode tapered right-hand circularly polarized helical antenna and a backfire left-hand circularly polarized helical antenna are combined and share the same helix, achieving the DCP radiation. Using the feature that the traveling-wave current distribution on the helix gradually weakens, good isolation with |S₂₁| < −15 dB over a 10.5% bandwidth is achieved. The design process and operating principle of the antenna are analyzed. An 8 × 8 array prototype with metal cavities is fabricated. Measured results demonstrate good impedance matching and isolation within 5.4 GHz to 6 GHz. The array achieves a gain loss < 3.4 dB, AR < 4 dB, and active voltage standing-wave ratio (VSWR) < 2.55 within a beam-scanning range of ±60°.