Micro-Doppler Analysis and I&Q Imbalance Correction

INTRODUCTION TO I&Q IMBALANCE CORRECTION

In the homodyne or direct down-conversion receiver (zero-IF), especially in cases of wide-bandwidth signals, the I/Q amplitude and phase imbalance makes the received complex signal improper and results in an image sideband of its spectrum. Even after a careful design of the receiver, it may at best achieve 30-40 dB image rejection rate (IRR).

For correction of the I&Q imbalance, a correction algorithm must be applied while processing the I&Q signal. The algorithm can be either implemented in the onboard FPGA processor, or applied in off-line signal processing. The algorithm corrects both I&Q phase and amplitude and restores a certain respected level of I&Q balancing.

Especially for micro-Doppler radar, which must be a coherent Doppler radar system with CW or wide-band modulated CW (such as FMCW), to extract respected micro-Doppler signatures, the I&Q must be balanced or at least the IRR must be more than 30-40 dB.

(An example of MATLAB source code for I&Q imbalance correction algorithm and sample MATLAB source codes for extraction of micro-Doppler signature using real radar data (CW and FMCW) will be included in every kit purchased.)