A Novel Circularly Polarized Wideband Folded Fresnel Lens Antenna with Out-of-band Suppression

This paper presents a high-gain, wideband circularly polarized (CP) folded Fresnel lens antenna operating at 60 GHz. A 3D-printed dielectric polarizer is employed to convert linearly polarized (LP) waves to CP, while a Fresnel lens provides phase compensation to achieve high gain. The folded configuration in-corporates a simplistically designed filtering polarization selector and reflective polarization rotator to facilitate both structural folding and out-of-band filtering. Experimental results confirm the antenna’s exceptional performance, including an impedance bandwidth of 68.2%, a gain bandwidth of 32.9%. The measured out-of-band suppression reaches 22.0 dB for the lower sideband and 12.5 dB for the upper sideband. This research demonstrates that filtering can be effectively integrated not only through feed network elements but also via electromagnetic wave propagation mechanisms in filtering-lens antenna designs, achieving superior performance without compromising compactness or efficiency.