All-Metal Dual-Band Miniaturized Linear-to-Circular Polarizer With Low Profile and Angle Stability

This article presents an innovative dual-band linear-to-circular polarization converter designed for the K/Ka band with orthogonal handedness. The converter features a sophisticated double-layer all-metal structure with two asymmetric folded cross slots of the same size engraved on both metal layers, ensuring minimal insertion loss and making it highly suitable for high-frequency communication. Additionally, traditional bending techniques are employed to miniaturize the cell, enhancing bandwidth and angle stability. A physical prototype comprising 20 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\rm{ \times }}$</tex-math></inline-formula> 20 units was fabricated using a cost-effective chemical etching process and rigorously measured in an absorbing environment. The results demonstrate that the converter maintains an axial ratio of less than 3 dB and an insertion loss of less than 1 dB at 19.15 GHz to 20.38 GHz and 28.86 GHz to 30.06 GHz under normal incidence. Furthermore, the performance under oblique incidence was evaluated. Even at an incidence angle of 30°, the operating bandwidth exhibits slight deterioration but still covers the nominal satellite communication frequency band.