A Consistent-Orthogonal Correction Method for I/Q Imbalance With Attenuation Modulation and Multiple Reflections Using CW Doppler Radar

Continuous wave (CW) Doppler radar is a highly sensitive sensor widely used for measuring micromotions of workpieces, blade tip clearance (BTC), and monitoring human vital signs. However, conventional correction methods are often inadequate, as they primarily focus on amplitude–phase imbalance and direct current (DC) offsets, while neglecting the effects of amplitude attenuation and multipath reflections in the reflected wave. To address these limitations, this article proposes an I/Q consistent-orthogonal correction (COC) method. The approach first constructs a Hilbert-based correction factor to preliminarily compensate for amplitude-phase imbalance and restore channel orthogonality. An I/Q calibration objective function is then formulated to optimize the imbalance parameters more precisely. Additionally, the Gram-Schmidt orthogonalization procedure (GSOP) is applied to further mitigate residual imbalance errors introduced by the inverse Hilbert transform. Theoretical analysis demonstrates that the parameter optimization in the COC method is robust against attenuation modulation and multipath effects. The effectiveness of the proposed method is validated through both simulation and experimental studies, demonstrating its potential for high-accuracy displacement measurements using CW Doppler radar.