Objective Frequencymodulated continuouswave (FMCW) lidar has the ability to measure ranges and velocities of moving targets simultaneously with high precision, and thus it has great potential in numerous applications such as space debris detection and space situational awareness. The conventional measuring method is to perform fast Fourier transform (FFT) to the intermediate frequency signal, and then the peakvalue frequency is used as the intermediate frequency to calculate the target range and velocity. However, this method cannot achieve highprecision measurement of highspeed targets. The highspeed movements of targets could causeThis shows that our method can effectively correct the measurement error caused by the highspeed movement of the target.Moreover, we also conduct a numerical simulation of multitarget measurement (Table 2). The results show that the proposed method can realize accurate range and velocity measurements of multiple targets (Fig. 8).Conclusions In this paper, the measurement of highspeed targets with FMCW lidar is studied. A novel algorithm for analyzing the intermediate frequency spectrum is proposed to correct the measurement error caused by highspeedmovementinduced spectral broadening of the intermediate frequency signal. Firstly, with theoretical analysis, we derive the theoretical expression of the intermediate frequency spectrum, and we study the variation of the intermediate frequency spectral structure with the increase of target velocity. Based on the symmetry characteristics of the intermediate frequency spectrum , the center frequency of the spectrum can be found by searching the peak value of the selfconvolution function of the spectrum amplitude. With this algorithm applied to the doublesideband FMCW lidar, the target distance and velocity can be calculated. Then, the validity of the theoretical analysis and the effectiveness of the algorithm in correcting the measurement error of highspeed targets are verified by numerical simulation.Compared with the traditional method, the proposed method can improve the measurement precision by more than three orders of magnitude under the same SNR. The advantages of the proposed method also include the small computation burden and strong antinoise ability. The research work in this paper provides a feasible approach for highprecision range and velocity measurement of highspeed targets, and we believe it will promote the application of FMCW lidar in space technologies.
