Sonar micro-Doppler effect induced by ship oscillatory motion in waves: Phenomenon, model, and experimentation

Traditional research attributes the modulated sidebands of ship radiation line-spectrum signals to reflections off rough ocean surfaces, but the Doppler effect caused by vessel motion may also contribute. This study establishes a micro-Doppler signal model based on wave-induced ship swaying, explaining that this phenomenon arises from the ship oscillatory motion in waves. The sea trial results demonstrate that the peak wave frequency, the frequency of ship micro-motions, and the micro-Doppler characteristic frequency recorded by the beacon exhibit a sudden frequency shift occurring synchronously from 0.075 to 0.115 Hz, thereby verifying the validity of the proposed model.