Design of dual-band wide-angle RF/IR beam combiner based on impedance matching

A radiofrequency (RF)/infrared (IR) beam combiner is used to combine IR signals and RF signals into a common transmission axis. In this study, a dual-band wide-angle RF/IR beam combiner with high RF transmission and IR reflection was proposed. Based on the impedance matching principle, the RF/IR beam combiner consisted of a high reflective IR film, an IR substrate, and two RF matching layers. Multi-objective particle swarm algorithm was applied to optimise the relative permittivity and the thicknesses of the IR substrate and the RF matching layers. A higher than 75% RF transmittance was obtained in both 8–12 GHz and 34–36 GHz bands when the RF incident angle was varied from 30° to 62°. At the same time, the reflectance in 8–12 μm was as high as 96%. It could be used in the hardware-in-the-loop simulation systems to test and evaluate the detecting and tracing performances of the RF/IR dual-mode guidance devices.