Waveguides and transmission lines in gaps between parallel conducting surfaces

A microwave device, such as a waveguide, transmission line, waveguide circuit, transmission line circuit or radio frequency (RF) part of an antenna system, is disclosed. The microwave device comprises two conducting layers arranged with a gap there between, and a set of periodically or quasi-periodically arranged protruding elements fixedly connected to at least one of said conducting layers, thereby forming a texture to stop wave propagation in a frequency band of operation in other directions than along intended wave guiding paths, thus forming a so-called gap waveguide. All protruding elements are connected electrically to each other at their bases at least via the conductive layer on which they are fixedly connected, and some or all of the protruding elements are in conductive or non-conductive contact also with the other conducting layer.A corresponding manufacturing method is also disclosed.