US Patent 7570710 In-phase and quadrature-phase signal amplitude and phase calibration

In-phase (I) and quadrature-phase (Q) signals are corrected for both amplitude and phase imbalances by passing the I and Q signals successively through a first amplitude correction stage, a sum-difference stage, and a second amplitude correction stage. The first amplitude correction stage balances the signal levels of the I and Q signals. The sum-difference stage produce a sum of the input I and Q signals, and a difference of the input I and Q signals, resulting in ideal quadrature in the outputs produced. The second amplitude correction stage corrects the amplitude differences from the sum-difference stage. Circuit configurations are used that minimize errors produced by the signal processing stages.