Contact and contactless differential I/O pads for chip-to-chip communication and wireless probing

Contactless differential coupling structures can be used to communicate signals between circuits located on separate chips or from one chip to a probing device. The contactless coupling structures avoid problems (breaks, erosion, corrosion) that can degrade the performance of ohmic-type contact pads. The contactless coupling structures comprise pairs of conductive pads placed in close proximity. Differential signals are applied across a first pair of differential pads, and the signals are coupled wirelessly to a mating pair of conductive pads. Circuitry for generating and receiving differential signals is described.