Synthesis Design of a Three-Dimensional Wideband Transmissive Polarization-Rotating Structure

Abstract

This letter proposes a novel easily assembled three-dimensional (3-D) wideband transmissive polarization-rotating structure (PRS). The proposed structure is composed of stacked single-layer printed circuit boards (PCBs) patterned with simple microstrip lines and slotlines, along with several metallic supporting structures. Due to the inherently orthogonal electric-field distributions between slotlines and microstrip lines on the same single-layer PCB, the PRS realizes effective 90° polarization rotation. An equivalent circuit model (ECM) is built and synthesized using the equal-ripple Chebyshev function; multiple resonators formed by transmission lines deliver high-order broadband performance. Based on this synthesis method, a 3-D PRS prototype is designed and fabricated, attaining a fractional bandwidth (FBW) of 66.2% and a return loss (RL) of 13 dB. Its unit cell has an electrical size of only 0.1λ₀ × 0.1λ₀. Structurally, the proposed structure exhibits a compact periodic size, low PCB consumption, and a simple fabrication process. Experimental results verify its excellent angular stability and broadband working capability. The presented design strategy provides new perspectives for the development of broadband 3-D PRS.