A Foreground Wide-Band Receiver I/Q Mismatch Calibration Method in FDD Transceiver

The performance of zero intermediate frequency (IF) receiver is usually limited by the frequency dependent I/Q mismatch, which gets worse with the increase of the signal bandwidth. Because the frequency dependent errors caused by the mixer and the baseband filters are difficult to eliminate, digital calibration methods are widely adopted. Among all the calibration methods, the algorithm based on the detection in frequency domain is able to extract the error at different frequencies which makes it suitable for foreground calibration. This paper proposed a receiver I/Q mismatch calibration method applied to wideband FDD transceivers, which can extract the error in frequency domain by transmitting customized signals through transmitters. A reasonable frequency plan is adopted to avoid the interference of TX image, nonlinearity and LO leakage and the wideband I/Q mismatch is compensated by a complex finite impulse response (FIR) filter. The proposed algorithm fully utilizes the existing hardware of the receiver, achieving a good balance between algorithm performance and hardware cost, which is validated on a FDD transceiver platform and the image rejection ratio (IRR) is improved from 33dB to at least 66dB in the whole baseband with a bandwidth of 245MHz.