Single-layer substrate integrated waveguide directional couplers

Novel single-layer planar directional couplers based on substrate integrated waveguide (SIW) technology are presented. These proposed couplers are totally realised in single-layer dielectric substrate with metallicvias, and fabricated using a standard PCB process. Prototypes of −3 dB, −6 dB and −10 dB SIW directional couplers are designed, fabricated and measured. It is concluded from the simulated and measured results that these couplers show good performances with broad operation bandwidth, low insertion loss, low return loss and high isolation etc. The characteristics of compact size and planar form make such SIW directional couplers can be easily integrated in microwave and millimetre-wave planar circuits.