The present invention provides improved non-contacting rotary joints for the transmission of electrical signals across an interface defined between two relatively-movable members. The improved non-contacting rotary joints broadly include: a signal source (A) operatively arranged to provide a high-speed digital data output signal; a controlled-impedance differential transmission line (C) having a source gap (D) and a termination gap (E); a power divider (B) operatively arranged to receive the high-speed digital data output signal from the signal source, and to supply it to the source gap of the controlled-impedance differential line; a near-field probe (G) arranged in spaced relation to the transmission line for receiving a signal transmitted across the interface; and receiving electronics (H) operatively arranged to receive the signal received by the probe; and wherein the rotary joint exhibits an ultra-wide bandwidth frequency response capability up to 40 GHz.