A comprehensive least squares calibration method for sideband separation receivers

This paper presents a novel comprehensive least squares calibration method based on digital sideband separation receivers. Addressing the issue encountered in existing traditional calibration methods, which necessitate measurements of both amplitude and phase at intermediate frequencies (IF), the proposed comprehensive least squares calibration method requires only the measurement of the amplitude and phase of the digital backend output for calibration. During digital signal processing of analog IF sampled outputs at the digital backend, a calibration coefficient matrix generated by the algorithm is introduced, and the amplitude and phase of the digital backend output signals are recorded. Amplitude and phase imbalances are solved using the least squares method, while the condition number of the calibration coefficient matrix is employed to determine whether preconditioning of ill-conditioned matrices is necessary. This process yields the amplitude and phase imbalances of the In-phase (I) and Quadrature-phase (Q) channels, which are utilized to compute compensation coefficients for calibration. Through MATLAB simulation, the feasibility of the comprehensive least squares algorithm is verified. Results demonstrate that sideband rejection ratios (SRR) of over 50 dB are achieved when amplitude imbalances range from -2.21 dB to 3.62 dB and phase imbalances range from 5° to 70°. This approach provides a promising pathway to enhance the operational performance of digital sideband separation receivers in practical applications.