A frequency converter (1) for generating an output signal (5a) from an input signal (5), the output signal (5a) having different frequency than the input signal (5), the frequency converter (1) including: an input (7) for receiving an input signal (5); a transmission line (3) formed of a non-linear medium (3a), the medium (3a) arranged such that when the input signal (5) propagates along the line (3), one or more harmonics (5a,5b) of the input signal (5) are generated; a plurality of dispersion control elements (13), the dispersion control elements (13) arranged to control the dispersion relationship of the medium (3a), to phase match the input signal (5) and the one or more harmonics (5a,5b), such that energy is transferred from the input signal (5) to the one or more harmonics (5a,5b); and an output (9) for providing the one or more harmonics (5a, 5b) as an output signal.