Cut-Off-Less Coplanar Waveguide Connector with Mode-Selectable Filter

Herein, we study a novel coplanar waveguide and its connector structure that allows all three waveguide propagation modes: transverse-electric (TE), transverse-magnetic (TM), and transverse electromagnetic (TEM). With a split structure and appropriate connectors, the waveguide can be used both over and below the cutoff frequency. This study presents a design for such a capped coplanar waveguide that is easily assembled. The cap is insulated from the waveguide body to allow TEM-mode trans-mission. The TEM mode allows transmission below the wave-guide`s cutoff frequency, and waves can propagate in the TE and TM modes similar to a typical inner waveguide with low loss. Furthermore, by adding a low-pass filter to the waveguide-coaxial conversion, the transmission mode can be selected for each frequency, which weakens the coupling between the modes. Transmission both under and over the cutoff frequencies was confirmed in simulations of the proposed waveguide. We also discuss the waveguide structure and the connectors required for practical use.