concept
In addition to the overall movement of the target, the relative movement of any structural part of the target is called fretting. The Doppler effect caused by micro-motion will produce a small and fine frequency modulation phenomenon in the joint time-frequency of the sensor echo.
Classification
刚体微多普勒效应
A rigid body cannot be deformed, that is, the distance between any two points that constitute a rigid body remains constant during motion. Typically, the target geometry is described by its position and orientation. The position is determined by the position of a reference point (such as the center of mass) within its object, and the orientation is determined by its angular position. The motion of a rigid body can be described by its dynamic quantities, such as linear velocity and angular velocity, linear acceleration and angular acceleration, linear momentum and angular momentum, and kinetic energy. As a rigid body moves, its position and orientation change over time. Common rigid-body targets include missiles, vehicles, and drones.
非刚体微多普勒效应
A non-rigid body is deformable, that is, the distance between any two points that constitute a non-rigid body can change during motion. When studying radar scattering caused by non-rigid body motion, the target can be modeled as a multi-rigid body combination connected by nodes, so the non-rigid body motion is regarded as multi-rigid body combination motion. Human behavior falls under the category of non-rigid body motion, and common human behavioral micro-Doppler targets include gait, gestures, and other everyday human behaviors.