A TM0 surface wave launcher by microstrip and substrate integrated waveguide technology

In this article, a simple surface wave launcher (SWL) in substrate integrated waveguide (SIW) technology is proposed. The launcher utilizes a conventional microstrip to SIW transition with the motivation of transferring power into the dominant TM
₀
surface wave (SW) mode of a grounded dielectric slab (GDS). Moreover, by appropriate design of the SIW section and by applying field matching techniques using sub-wavelength microstrip patches while also conveniently separating some of the via conducting posts for one of the SIW side-walls, power can leak into the GDS with minimal losses for the generation of a bound and guided TM SW with a uniform phase front. The design approach is confirmed by numerical calculations and full-wave simulations for two feed systems which operate at 15 GHz, with and without the matching section. Our new approach for simple, microstrip-fed SW launching at microwave frequencies can also be useful for other SW-based guides, novel low-cost transitions, and new compact dividing/combing circuits for antenna feed systems as well as other SW structures which employ a common substrate.