DFT-Based Method for Accurate I/Q Imbalance Estimation

This brief presents a new all-digital blind algorithm based on three-point Discrete Fourier Transform (DFT) interpolation algorithm for the accurate calibration of in-phase (I) and quadrature (Q) imbalance in the direct-conversion transceivers. The subject of the algorithm can be a wireless local area network (WLAN) 802.11a/b/g/j/p/n/ac/ax/be test application. The proposed three-point DFT interpolation algorithm can calculate system frequency of the received signals to achieve the unbiased estimation, and it can be extended to calculate each subcarrier frequency offset of the orthogonal frequency division multiplexing (OFDM) signal. In the signal-to-noise ratio test, the signal-to-noise ratio (SNR) is set to 40 dB, the simulation results show that the image rejection ratio (IRR) of the received signals calibrated by the proposed algorithm can always reach to more than 60 dB under various test environments, and the mean square error (MSE) of the baseband frequency estimation is always below -85 dB. The proposed algorithm can exhibit the better performance in the vast majority of cases compared with some existing algorithms. In addition, the proposed algorithm can maintain good performance in RF conformance testing.