A Coherent CZT-Based Algorithm for High-Accuracy Ranging With FMCW Radar

The essence of frequency-modulated continuous wave (FMCW) radar-ranging is to estimate the frequency of the beat signal, and the frequency’s accuracy determines the range accuracy. This article introduces a coherent spectral model based on the correlation between the phase and frequency of the FMCW radar beat signal. A coherent chirp $z$ transform (CCZT) algorithm is proposed by applying the coherent spectral model to the CZT algorithm. The simulation results proved that the ranging accuracy of the CCZT algorithm is better than other algorithms. Generally, there are two Crámer–Rao bounds (CRBs) in range estimation. The first CRB assumes that the phase is unknown, and the second CRB assumes that the phase is known. Most existing ranging algorithms can only reach the first CRB, while the CCZT algorithm can reach the second CRB. The efficiency of the CCZT algorithm has been confirmed in three radar-ranging experiments with targets of various sizes and shapes. The experimental results also showed that the CCZT algorithm has a higher accuracy than $50 \mu \text{m}$ , and its root-mean-squared error (RMSE) is significantly lower than other algorithms.