Design of dual-band substrate-integrated waveguide E-plane directional couplers

Dual-band substrate-integrated waveguide (SIW) couplers for operation in the 20/30 GHz bands are presented. Initial design guidelines follow substrate selection and aperture coupling theory as known from standard air-filled waveguide components. The results demonstrate that this design approach is sufficient for many applications. All-dielectric waveguide ports as well as microstrip ports are used as interfaces to the SIW couplers. Designs are analyzed within an Ansoft HFSS environment, and the approach is verified by comparison with results obtained from CST Microwave Studio. Performances of several prototype designs are presented for dual-band coupling values between 6 dB and 20 dB. All coupler dimensions are specified.