Wideband circularly polarized antenna loaded with π-shaped dipole for millimeter-wave applications

This paper presents a novel wideband circularly polarized antenna that is fed by substrate-integrated waveguide. Based on the design of placing a pair of chamfered semicircular patches above a slot, a pi ${\rm{\pi }}$-shaped radiator is introduced between the semicircular patches. Multiple resonance points are generated by the combination of the entire radiating structure and a dumbbell-shaped slot, resulting in improved impedance bandwidth and axial ratio (AR) bandwidth. The proposed element exhibits a wide impedance bandwidth of 50.5% (24.5-41.1 GHz) and an AR bandwidth of 44.2% (25.1-39.3 GHz) with a 44.2% overlapped bandwidth. Then, a 4 x 4 antenna array adopting the sequential rotation technique is constructed. The measured results demonstrate that a 40.6% overlapped bandwidth and a peak gain of 19.1 dBic are achieved. The proposed antenna array shows excellent performance, making it a good candidate for applications in millimeter-wave wireless communication systems.