Method and apparatus for estimating and correcting gain and phase imbalance in a code division multiple access system

摘要

Gain and phase imbalance is estimated by using an IQ-swapped spreading sequence in addition to a regular spread pilot signal. The IQ-swapped spreading sequence is the spreading sequence whose real and imaginary components are the imaginary and real components of the regular spreading sequence. The gain imbalance can be estimated by a function of the difference between the real component of a regular despread pilot signal and the imaginary component of the IQ-swapped pilot signal. In a similar fashion, the phase imbalance is estimated by a function of the difference between the imaginary component of a regular despread pilot signal and the real component of the IQ-swapped despread pilot signal. A controller such as a DSP ( 102 ) uses the gain and phase imbalance estimates to control a gain and phase correction circuit ( 104 ). In one embodiment, the correction circuit ( 104 ) includes a plurality of multipliers ( 202-212 ) and a ROM look-up-table ( 202 ) in order to perform the imbalance correction.