US Patent 7928788 Double-balanced sinusoidal mixing phase interpolator circuit and method

A double-balanced sinusoidal mixing phase interpolator circuit comprises: a double-balanced gain stage having a first input for receiving a first phasor clock, a second input for receiving a second phasor clock, and a phase interpolator (PI) output, wherein the double-balance gain stage includes (i) a first gain stage having a positive input side and a negative input side for the first phasor clock and (ii) a second gain stage having a positive input side and a negative input side for the second phasor clock; and a sinusoidal digital-to-analog (DAC) stage coupled to the double-balanced gain stage and configured to implement sinusoidal weighting of positive and negative sides of differential DAC current for the first phasor clock and positive and negative sides of differential DAC current for the second phasor clock, wherein the sinusoidal weighting provides uniformly spaced phase steps in the phase interpolator (PI) output.