A tunable electromagnetic delay line, comprising a first conductor with a first main direction of extension. The first conductor is arranged on top of a non-conducting substrate. The delay line additionally comprises a layer of a ferroelectric material with first and second main surfaces. The layer separates the first conductor and the substrate. The delay line also comprises a second conductor with a second main direction of extension, with the first and second main directions of extensions essentially coinciding with each other, and with the first and second conductors being each other's mirror image with respect to an imagined line in the center of the delay line along the first and second main directions of extension. The tuning is accomplished by applying a voltage between said first and second conductors.