A High Range-Accuracy Interferometry Radar for Very Small Transponder Positioning

A 24 GHz interferometry ranging radar with tenths of micro-meters accuracy is developed for positioning very small transponder. To achieve high ranging accuracy, the small target is binary-phase modulated to reject the clutter interference. However, the frequency drifting between the modulated target and the radar receiver generates considerable range error. An interferometry envelope detection and flipping method is proposed to eliminate the asynchronous error. The experiment demonstrates that a 70 μm root-mean-squared error is achieved for ranging the transponder with a small size of 2 cm2, by the developed 24 GHz radar with a 34.4 dBm EIRP.