INTERFACE CIRCUITS

An interface circuit, comprising: a signal line having signal, auxiliary and connection nodes defined therealong, the connection node for connection to a transmission line; signal-handling circuitry connected to the signal line at the signal node so that an effective capacitance of the signal-handling circuitry is experienced at the signal node; an auxiliary circuit connected to the signal line at the auxiliary node so that an effective capacitance of the auxiliary circuit is experienced at the auxiliary node; a signal pair of inductors connected in series along the signal line adjacent to and either side of the signal node; and an auxiliary pair of inductors connected in series along the signal line adjacent to and either side of the auxiliary node, wherein: the signal pair of inductors are configured to have a mutual coupling defined by a coupling coefficient kS; the auxiliary pair of inductors are configured to have a mutual coupling defined by a coupling coefficient kA; for each said pair of inductors, the inductors of the pair are arranged such that a current flowing along the signal line in a given direction through one of those inductors induces a current in the other one of those inductors and flowing in the same direction along the signal line given a positive coupling coefficient; and kS has a positive value and kA has a negative value.