Ultra-wide band CPW to substrate integrated waveguide (SIW) transition based on a U-shaped slot antenna

A mm-wave transition from coplanar waveguide (CPW) to substrate integrated waveguide (SIW) is presented based on a U-shaped coplanar slot antenna. Using 3D FEM simulations the input impedance exhibited by the structure is analyzed, and simple equations are extracted to design an ultra-wide band transition once the substrate material and the waveguide cut-off frequency are chosen. As an example, a W-band transition on a high resistivity silicon-filled waveguide is implemented: an input matching better than −14.5 dB from 79 to 110 GHz and insertion loss of 0.6 dB at 110 GHz are measured.