Mixed-Mode I/Q mismatches compensation in low-IF quadrature receivers

The performance of the quadrature receivers are degraded due to the gain and phase mismatch in I and Q channels. In this paper we develop a mixed-mode technique for self calibration in quadrature receivers. A novel mismatch measurement and estimation scheme using an RF amplitude detector and the IC´s digital core is shown. Then, digital and digitally-assisted analog correction is employed to remove phase and gain mismatches in the quadrature channels. The mixed-mode configuration is shown to be of low complexity and overhead. Test cases for QAM-16 demonstrate the effectiveness of the proposed approach in suppressing quadrature mismatch and enhancing image rejection.