An electrical connector with a frequency-tuned groundplane is disclosed. The connector includes a signal medium to communicate an electrical signal and a frequency-tuned groundplane medium to communicate a reference voltage (i.e., ground). The groundplane medium differentially supplies the reference voltage to the groundplane second end, responsive to the frequency of the electrical signal. In one aspect, the first groundplane layer conductive trace includes a transmission line pattern, and the second groundplane layer conductive trace is connected to the first groundplane layer conductive trace through a plurality of conductive vias. For example, the first groundplane layer may include a plurality of conductive patches, some of which have a via connection to the second groundplane layer conductive trace.