Anti-aliasing heterogeneous chirp modulation in FMCW LiDAR systems for simultaneous range-velocity sensing

Frequency Modulated Continuous Wave (FMCW) LiDAR achieves simultaneous high-precision target measurement, offering inherent anti-interference capability and sub-millimeter stability for mission-critical applications. However, spectral aliasing caused by Doppler–range coupling in high-speed or short-range scenarios limits dynamic target detection and constrains measurable velocities. This work proposes a heterogeneous chirp modulation-based FMCW LiDAR system for simultaneous and unambiguous range and velocity measurement. It employs two independent lasers that generate a wideband triangular-chirp and a narrowband sawtooth-chirp optical signal, respectively. This modulation strategy produces multiple beat signals with distinct spectral separation, which establishes a deterministic mapping between range- and velocity-dependent components and enables their decoupling. As a result, the heterogeneous chirp architecture effectively resolves spectral aliasing and achieves robust, unambiguous sensing in high-dynamic scenarios. The system is first validated through MATLAB-based frequency-domain simulation and optical system modeling, followed by experimental evaluation under both typical and high-dynamic (short-range vibration and AOM-based high-speed simulation) motion. Under typical motion conditions, it achieves a range error below

and a velocity error below

across all tested conditions. In a near-range vibration experiment, it measures a distance of

and a velocity of

. By emulating Doppler shifts with an acousto-optic modulator (AOM), the system is further demonstrated to be capable of tracking high-speed motion up to

within a range of

, corresponding to approximately 20 times the upper velocity limit of conventional FMCW LiDAR under similar short-range conditions.