Patent ID: 7512188

Claim:
A system for communicating between two integrated circuits, comprising: a first integrated circuit having an output circuit for converting digital data into a phase modulated analog signal, the first integrated circuit positioned on a first printed circuit board; and a second integrated having an input circuit for converting the phase modulated analog signal back to the digital data, the second integrated circuit positioned on the first printed circuit board or on a second printed circuit board, wherein the second printed circuit board is connected to the first printed circuit board via a common backplane; wherein the phase modulated analog signal comprises an amplitude phase shift keying signal; wherein the output circuit comprises: a ring oscillator for generating a plurality of phase shifted clock signals; and a converter circuit for receiving the digital data and at least one of the plurality of phase shifted clock signals and for generating the amplitude phase shift keying signal, the converter circuit including: a switch for passing through a signal of the plurality of phase shifted clock signals when a first bit of the digital data is asserted; an amplifier connected to the switch for amplifying the signal; and a multiplexer connected to the amplifier for selecting an amplitude of a plurality of amplitudes for the signal, the multiplexer controlled by a second bit of the digital data.