Virtual ground return for reduction of radiated emissions

A digital apparatus having a cable comprising a plurality of high-speed and low-speed signal carrying conductors, the conductors carrying the low-speed signals are bypassed to a signal ground with selected values of capacitance so as to become virtual signal ground return conductors for the high-speed signal conductors. The selected values of capacitance have a lower impedance then the characteristic impedance of the conductors in the cable. The cable may be a multi conductor cable, a ribbon cable, a flex cable, a twisted pair cable, etc. In a similar fashion, signal conductors on a printed circuit board, not having a separate ground plane layer, may create virtual signal ground returns from the low-speed signal carrying conductors that are proximate to the high-speed signal carrying conductors for reduction of radiated electromagnetic radio frequency interference.