Dual matched filter for FMCW lidar: Enabling better range and velocity measurements

Frequency modulated continuous wave lidar, as an important tool to measure velocity and distance, has shown promising prospects in many applications. To address the shortcomings of conventional signal processing methods applied to this type of lidar, a dual matched filter method is proposed in this article. One matched filter is used to derive the velocity of moving target by analyzing the range difference over distinct time intervals, the other one is employed for range measurement by processing the local reference and down-coverted reflected signal. The theoretical analysis demonstrates that the proposed method offers significant advantages over conventional method. Firstly, it doubles the distance measurement range, effectively addressing the inherent range limitations of traditional method. Secondly, it overcomes the critical challenge of close-range high-speed measurement, which remains a persistent drawback in conventional systems. Furthermore, the method maintains distance and velocity measurement precision and resolution at levels comparable to or better than those of traditional method. Crucially, the proposed method achieves a 9.5 dB improvement in signal-to-noise ratio. Additionally, under nonlinear frequency modulation errors of 19.8 MHz, 198 MHz, and 396 MHz, the proposed method consistently delivers superior spectral resolution compared to the conventional method. This study can provide technical guidance and new ideas for researchers in this field.