There is disclosed an electromagnetic transmission line arrangement with a phase shifter, comprising at least one conductive branch line (51a,51b) extending from a junction point (51c) to an associated output port, for the propagation of electromagnetic signals in a frequency band along said branch line. The phase shifter includes at least one dielectric body (52,53,54) which is mounted so as to be movable sideways in a transverse direction into a delaying position at least partly covering said branch line (51a,51b). The longitudinal distribution of its dielectric material (∈) is adapted to cause, when being moved transversally into said delay position, a controlled phase shift but also to secure, by way of said selected longitudinal distribution of its dielectric material in conjunction with said at least one branch line, an input impedance matching of said transmission line arrangement. The transmission line arrangement can be used in the feeding network to a microwave antenna.