High resolution LFMCW radar system using model-based beat frequency estimation in cable fault localization

A linear frequency modulated continuous wave (LFMCW) radar is introduced to localize the impedance discontinuities on the instrument cable used in nuclear plants. The LFMCW reflectometry uses a phenomenon that electromagnetic pulses are reflected at the impedance discontinuities to localize impedance discontinuity points on the cable. For localizing impedance discontinuities, time delays between the incident signal and the reflected signals from the impedance discontinuities have to be measured. The LFMCW is modeled by timevarying auto-regressive (AR) model. From the coefficients of the AR model, instantaneous frequency is estimated by the Kalman filtering to calculate the time delays. The performance of the proposed method is verified by experiments.