Abstract: A device facilitating the design and adjustment of millimeter wave sources comprising an active component of quasi-microscopic dimensions which has to be coupled with extreme accuracy to the input of a directional antenna having relatively large dimensions. In various embodiments the device exhibits the following common features: an assembly incorporating a solid-state active component, a resonant cavity, means for coupling said cavity to a directional antenna, adjusting means and a directional antenna, said assembly being fitted in such a manner that a simultaneous adjustment of the position of said component in said cavity and of said coupling means, is made possible by acting upon said adjusting means.