Blind I/Q mismatch compensation with receiver non-linearity

摘要

Apparatus and methods disclosed herein perform gain, clipping, and phase compensation in the presence of I/Q mismatch in quadrature RF receivers. Gain and phase mismatch are exacerbated by differences in clipping between I & Q signals in low resolution ADCs. Signals in the stronger channel arm are clipped differentially more than weaker signals in the other channel arm. Embodiments herein perform clipping operations during iterations of gain mismatch calculations in order to balance clipping between the I and Q channel arms. Gain compensation coefficients are iteratively converged, clipping levels are established, and data flowing through the network is gain and clipping compensated. A compensation phase angle and phase compensation coefficients are then determined from gain and clipping compensated sample data. The resulting phase compensation coefficients are applied to the gain and clipping corrected receiver data to yield a gain, clipping, and phase compensated data stream.

主权项

1. A quadrature signal processing method comprising:
determining a clipping threshold and a gain correction value associated with data samples in an in-phase (I) arm and a quadrature (Q) arm in a channel of a quadrature receiver following frequency conversion and analog-to-digital (ADC) conversion; applying the gain correction value and clipping threshold to received and converted data in the I arm and the Q arm such as to balance a statistical distribution between data in the I arm and data in the Q arm and to enable correction of gain and phase imbalance in the I and Q arms; the determining a clipping threshold and a gain correction value including: during a first set of iterations, determining, from a gain and clipping compensated set of I data samples and Q data samples captured during a sampling period at a start of each iteration, an estimated gain compensation coefficient associated with a gain compensation function in the I arm and the Q arm and an updated clipping threshold associated with a clipping compensation function in the I arm and the Q arm of the quadrature receiver channel following frequency conversion and analog-to-digital (ADC) conversion; factoring a set of received I data samples and Q data samples using the gain compensation function to obtain a current gain compensated set of I data and Q data samples; and performing clipping operations on the current gain compensated set of I data samples and Q data samples using the updated clipping threshold outputted from the clipping compensation function to obtain a current gain and clipping compensated set of I data samples and Q data samples to use as input data to a next one of the first set of iterations.