Adjusting Detectable Velocity Range in FMCW Radar Systems Through Selective Sampling

In a frequency-modulated continuous wave (FMCW) radar system, a series of waveforms with frequencies that increase linearly over time is transmitted. Once the transmitted signal reaches the target and returns, sampling is applied to the received signal, followed by the Fourier transform for distance and velocity estimation. In general, the detectable velocity range depends on the duration of a single waveform in the FMCW radar systems. If the target moves at a velocity that exceeds the detectable velocity of the radar, accurate velocity estimation is impossible due to Doppler ambiguity. Therefore, in this article, we propose a method for adjusting the detectable velocity range using a selective sampling method. In the proposed method, velocity ambiguity can be resolved by dual processing the samples obtained along the time axis at different rates. When the proposed method is applied to targets beyond the detectable velocity range of a conventional FMCW radar system, it effectively resolves Doppler ambiguity, enabling efficient velocity estimation. Our method has been verified to be well-applicable to data obtained from both simulation and real-world measurements. The comparison of the estimated velocity using our method with the ground truth in real-world measurements indicates an error of 0.07 m/s. We expect our proposed method to contribute to resolving the issue of velocity estimation ambiguity in the FMCW radar systems.