Spectrum-Based Online Estimation of IQ Imbalance for Near Field Radar Distance Sensors

Florian Liebgott, Marvin Jandt, Mark Eberspächer, Annika Liebgott, Bin Yang

Abstract: A mismatch of the in-phase (I) and quadrature (Q) signal path of a direct-conversion receiver results in IQ imbalance, which distorts the demodulated signal. However, if the imbalance parameters can be estimated, the influence of the IQ imbalance can be compensated. We propose a novel method to estimate the parameters during normal operation of a stepped frequency continuous wave (SFCW) radar distance sensor without the need for a pilot signal. To estimate the imbalance parameters, we exploit the structure of the spectrum of the demodulated signal. Evaluating our method on real sensor data shows superior results especially for very short distances.