Carrier frequency offset recovery with I/Q imbalance using four-point interpolated DFT algorithm

Carrier Frequency Offset (CFO) estimation is vital for frequency synchronization, but is challenged by harmonic interference from IQ imbalance (IQI). This work presents further solutions to the problem of CFO recovery in the presence of IQI harmonic interference. By combining coarse estimation based on peak searching and fine estimation based on 4-point discrete Fourier transform (DFT) interpolation technique, the frequency of the single-tone signal is extracted with the observed data for recovering CFO. In the fine estimation, two quadratic equations considering the IQI interference structure provide the relationship between CFO and the observed DFT samples. To validate the effectiveness of the proposed method, a verification platform consisting of a vector signal generator (VSG) and a vector signal analyzer (VSA) is utilized. Results demonstrate that, at an input power of -45 dBm, the proposed algorithm outperforms traditional CFO estimators by at least 10 dB. Additionally, complexity analysis indicates that the real multiplication count of the proposed algorithm increases by as much as 3.2% compared to traditional DFT interpolation algorithms.