A New Dual-Band Dual-Circularly Polarized mmWave Planar Array Antenna Based on Novel Compact Diplexing Double-C-Shaped Elements

A novel dual-band dual-circularly polarized (CP) array antenna is presented, capable of achieving right-hand circular polarization (RHCP) in the K band and left-hand circular polarization (LHCP) in the Ka band, making it an excellent candidate for satellite communication and other diplexing communication systems. The antenna’s radiating element features a double-C-shaped strip design fed through a metallic via. S-shaped slits are precisely etched onto the strips to ensure isolation between segments operating at different frequency bands. The whole array design incorporates a microstrip line feeding network, resulting in a compact and efficient structure. An 8 × 8 array based on the proposed radiating elements and feeding network was designed, fabricated, and measured. The measurement results indicate the impedance bandwidths (|S₁₁| < −10 dB) of 17 − 24.7 GHz (36.9%) and 28.5 − 33.4 GHz (15.8%), as well as the 3-dB axial ratio (AR) bandwidths of 18.5 − 24.0 GHz (25.9%) and 28.8 − 34.3 GHz (17.4%), over the K and Ka bands respectively. Therefore, the array achieves the impedance-AR combined bandwidths of 18.5 − 24 GHz (25.9%) in the K band and 28.8 − 33.4 GHz (14.8%) in the Ka band, with peak gains of 17.9 dBic and 19.3 dBic, respectively. The relative sidelobe levels remain below −13 dB for both bands, with the antenna efficiency exceeding 62% and 40% within the combined bandwidths of the K band and Ka band, respectively. The proposed dual-CP antenna successfully combines wideband performance across the K- and Ka-bands with a low-profile and structurally simple design, offering a practical and cost-efficient solution.