Software-defined Calibration for FMCW Phased-Array Radar

This paper addresses the problem of calibrating a FMCW phased-array radar to meet design specifications both in slant-range and beam pattern. The software-defined method presented here, while generally applicable, is implemented on an S-band phased-array radar which uses low-cost commercial-off-the-shelf (COTS) components designed for Wi-Fi communications. Calibration is performed on the receive array outputs in both fast-time to compensate for the non-linearity of the transmitter VCO and across antenna elements account for non-uniform inter-channel phases, amplitudes, and time delays. Fast-time calibration is achieved using a digital closed-loop correction while spatial calibration involves operations to adjust the de-chirped frequency, phase, and amplitude of each channel. The calibration method is evaluated using a low-power wideband S-band linear FMCW radar with an 8-element receive array operating between 2.1 to 2.7 GHz. Results are presented which demonstrate the system achieves close to theoretically predicted 1 foot range and 16 degree azimuthal resolution, which is not achieved by the uncalibrated system.