Bias analysis of a gain/phase/DC-offset estimation technique for direct frequency conversion modulators

This paper studies a least-square-based technique for compensation of gain and phase imbalances and DC-offsets in a direct frequency conversion quadrature modulator. The technique requires the instantaneous power measurement at the transmitter to calculate the gain/phase/DC-offset compensation coefficients. The biases of the estimated coefficients are analyzed when there exist various distortions in the power measurement circuit including circuit noise, quantization error, DC-offset, power detector modeling error, and filtering. A numerical method is used to validate these analyses.