High-accuracy distance measurement using millimeter-wave radar

We present a method to estimate distance using millimeter-wave radar with an accuracy of around a few micro meters. With the radar operating using frequency-modulated continuous waves (FMCW), we show how both frequency and phase of radar beat signal is used to precisely determine the distance between the radar sensor and the object from which the radar signal is reflected. The method was tested using single-chip FMCW radar operating at 77 GHz employing a chirp bandwidth of 4 GHz. We compared the estimated relative distance against the true relative distance at a few different locations of the object. The estimated distance has a variance of less than 10 μm, which approaches the Cramer-Rao lower bound. We will also present a novel solution to minimize estimate bias due to reflections from neighboring objects as well as a solution to the undesired phase ambiguity problem that is associated with phase recovery during distance estimation.