Broadband High-Efficiency Circularly Polarized Transmitarray Using Symmetric Dual-Linearly Polarized Elements With Distinctive Excitation Mechanisms

A high aperture-efficiency circularly-polarized (CP) transmitarray (TA) is introduced, targeting wideband satellite communication applications at the millimeter-wave frequency band. The proposed TA element utilizes a pair of back-to-back cascaded substrate-integrated magneto-electric (ME) dipoles, achieving broadband transmission with low insertion loss in a compact configuration. Unlike conventional CP designs relying on geometrically asymmetric structures, this element employs a symmetrical dual-linearly polarized radiator to reduce mutual coupling variation between elements with different rotation angles, thus simultaneously improving both the element bandwidth and array efficiency. The key challenge of generating the required differential transmission phase for CP operation from a rotationally symmetric element is addressed by leveraging two distinct excitation mechanisms. Specifically, the single-ended driven and differentially driven excitation techniques are jointly exploited for the two orthogonally-polarized ME dipoles, respectively, enabling a substantial and pronounced transmission phase difference for the two polarizations despite the symmetric element outline. A 256-element TA was designed, simulated, and experimentally validated. The measured results reveal a wide 3 dB axial ratio bandwidth of 43.7%, a 3 dB gain bandwidth of 29.2%, and a peak aperture efficiency of 51.8%. These results highlight the design’s capability to generate wideband, high-purity CP beams, offering a low-cost solution for advanced satellite communication systems.