3-D Printed Millimeter-Wave Filtering Monopulse Comparator for Dual-Circularly Polarized Antenna

This letter investigates a Ka-band 3-D-printed filtering monopulse comparator tailored for a dual-circularly polarized (CP) monopulse antenna with high-frequency selectivity. The proposed monopulse comparator, consisting of four all-resonator filtering magic-Ts, achieves precise in-phase and out-of-phase excitation while integrating an enhanced filtering response simultaneously. Additionally, two identical comparators serve as feed networks for a dual CP radiator, enabling the generation of dual-CP sum and difference beams with high out-of-band suppression. Leveraging 3-D printing technology, the prototype is monolithically fabricated. The measured results demonstrate that the proposed design can achieve an impedance-matching bandwidth (return loss > 10 dB) of 27.7 GHz to 30.6 GHz and a sum gain up to 14.3 dBic. Moreover, outside the operating bandwidth, the achieved gain is reduced by over 40 dB. Characterized by high efficiency, excellent frequency selectivity, and a compact volume, the proposed filtering monopulse comparator holds significant promise for applications in millimeter-wave monopulse systems.