Abstract: A wide band device is provided for coupling between the delay line of a travelling wave tube and the external circuit transmitting the energy of the tube, comprising a coupling wave guide having a single ridge, connected on one side to the delay line and on the other being extended by one of the two ridges of the output guide, the section of the coupling guide increasing progressively, with constant impedance from the line to the output guide whereas this latter has an impedance transformer providing impedance matching between its standard guide part and the coupling guide.