**Abstract**

The chapter presents a review of properties and applications of a particular category of Substrate Integrated Waveguide (SIW) named NWSIW, for NanoWire-based Substrate Integrated Waveguide. The NWSIW topology combines metallic nanowires embedded in a porous template in order to form planar compact integrated waveguides; nanowires selectively grown in the template are used for building the walls of the waveguide, but also allow to achieve microwave functionalities such as filtering, isolation. Through the chapter the comparison made with classical waveguides including SIW will lead to a discussion on future perspectives and possible improvements of this NWSIW topology. Their performances will be explained and illustrated with regards to current state-of-the art, and based on results obtained at UCLouvain.

**Keywords:** SIW, porous template, metallic nanowires, microwaves, isolator, filter, design, fabrication
