干涉测量低频水下声源频率的改进算法

为了实现低频段水下发生目标频率的准确识别,搭建了一套激光干涉测量系统。在相位生成载波解调技术的基础上,提出了一种改进的基于相位生成载波反正切算法的解调方式。在光学暗室下利用分立光学元件搭建了一套干涉实验系统,在参考光路引入水面波动作为高频载波,利用水表面漫反射的主反光与参考光干涉获得干涉信号。以相位生成载波解调技术的反正切算法为基础,引入高频载波信号的一倍和二倍正弦混频。通过功率比较的算法在两组正交信号当中筛选功率较强的一组进行解调,避免了载波初相位导致的正交信号消隐引起的解调失真。最后,在模拟的低频大幅度海浪扰动情况下进行了探测实验,取得了良好的解调效果。实验结果表明:水下声源的低频探测下限约为30 Hz;100Hz以上频段的频率探测精度优于1Hz。改进的反正切解调算法能够避免解调失真,具有很强的抗干扰能力。

Improved algorithm for interferometric measurement of low-frequency underwater acoustics

A laser interferometry system was built to accurately realize the frequency identification of low-frequency underwater targets. An improved algorithm was proposed based on the Phase-Generated Carrier (PGC) demodulation technology using the arctangent demodulation algorithm. First, a set of interference experiment systems was built using discrete optical elements under an optical darkroom. Water surface waves were introduced into the reference optical path as a high-frequency carrier, and the interference signal was obtained by interference with the main reflector of measuring and reference light. Next, sine mixing of the carrier signal is introduced based on the arctangent algorithm of the PGC demodulation technique. Using the power comparison algorithm, the group with stronger power was selected between two groups of orthogonal signals for demodulation, so as to avoid demodulation distortion caused by the initial carrier phase. Finally, the anti-interference ability was demonstrated by experiments under substantial mechanical disturbance. Experimental results show that the lower detection limit of the underwater sound source is approximately 30 Hz, and the frequency detection accuracy obtained by multiple detections is better than 1 Hz at frequencies above 100 Hz. The improved arctangent demodulation algorithm can effectively avoid demodulation distortion and has a strong anti-interference ability.