Novel rectangular‐to‐circular waveguide mode converter based on using one‐step double‐cruciform waveguide for millimetre‐wave applications

Abstract A novel design for a TE10‐mode rectangular waveguide to a TE11‐mode circular waveguide mode converter based on the use of an intermediate one‐step double‐cruciform section is proposed. The converter achieves compactness and broadband by employing the one‐step double‐cruciform transition instead of the conventional multi‐step transitions or smooth transitions. Due to the one‐step structure, the converter achieves an extremely short‐length (around 0.3λ, where λ is the wavelength at the centre frequency), which makes it suitable for highly compact systems. For verification purpose, a back‐to‐back connection rectangular‐to‐circular mode converter was fabricated and measured. The measured results show that the return loss is around 15 dB and the insertion loss is around 0.4 dB in the operating frequency band. Thus, we can infer that the return loss and insertion loss of a single mode converter are around 19 and 0.2 dB, respectively. The experimental results reasonably agree with the simulated results.