Frequency Control of a Frequency-to-voltage Converter for Distance Resolution Improvement of an FMCW LiDAR

Abstract

Frequency-modulated continuous-wave light detection and ranging (FMCW LiDAR) is a sensor that uses light interference to measure distance. FMCW LiDARs have recently gained attention because the wave nature of laser makes it resistant to harsh environmental conditions. FMCW LiDAR transmits and receives a linearly modulated beam to obtain an interference frequency which is proportional to distance. Fast Fourier transform (FFT) is mainly used to measure interference frequency. FFT has the problem that it takes a long time to acquire the interference frequency. In this study, the interference frequency is obtained using a frequency-to-voltage converter (FVC) which is capable of high-speed frequency measurement. FVC converts the interference frequency into a voltage signal using the one-shot conversion. However, FVC has the disadvantage that ripple noise generated in the process of averaging one-shot signals included in the output signal. To solve this problem, we propose a high-resolution frequency measurement method that uses frequency control to shift the frequency to a high frequency band where ripple noise can be minimized and indirectly measures the frequency through the controller output. In this paper, the principle of frequency control is mathematically analyzed and the performance of frequency control is confirmed through experiments. © ICROS, KIEE and Springer 2024.