A Study on Laser-Induced Acoustic Water-to-Air Cross-Medium Communication Method Based on PWM Modulation
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摘要: 面对海空天一体化通信组网的发展需求, 激光致声通信作为实现空中平台与水下目标之间无节点通信的关键技术, 其研究和应用日益受到关注。传统的基于单脉冲识别的调制解调方法在低重复频率下实现了良好的通信效果, 而在高重频条件下, 基于单脉冲识别的调制解调方式由于脉冲间相互干扰加剧, 对码元判定造成明显干扰进而导致误码率较高无法正常通信的问题。本研究针对这一问题, 提出了一种采用PWM调制的新型激光致声通信方法, 实验中采用最大重复频率为500 Hz的Nd: YAG脉冲激光器, 通过调整激光脉冲数量产生不同宽度的PWM调制信号, 然后在接收端通过脉冲宽度进行码元识别。实验结果表明, 采用PWM调制的通信方式可以有效降低脉冲之间干扰带来的译码错误, 在最高400 Hz重复频率下实现了良好的通信效果(误码率仅为8%), 提升了高重复频率下激光致声通信的可靠性和有效性。Abstract: In light of the demand for integrated communication networks spanning sea, air, and space, laser-induced acoustic communication has emerged as a critical technology for facilitating nodeless communication between airborne platforms and underwater targets, garnering increasing attention in research and application. Traditional modulation and demodulation techniques based on single-pulse recognition have achieved satisfactory communication outcomes at low repetition frequencies. However, at higher repetition rates, these techniques face challenges due to exacerbated interference among pulses, significantly disrupting bit determination and leading to high error rates that impede effective communication. Addressing this issue, this study introduces a novel laser-induced acoustic communication method employing Pulse Width Modulation (PWM). Experiments utilized an Nd:YAG pulsed laser with a maximum repetition rate of 500 Hz, adjusting the number of laser pulses to generate PWM signals of varying widths, with bit recognition at the receiving end based on pulse width. The PWM-based communication method effectively minimizes decoding errors due to inter-pulse interference, achieving commendable performance at the highest repetition rate of 400 Hz with an error rate of just 8%. This improvement significantly enhances the reliability and effectiveness of laser-induced acoustic communication at high repetition frequencies.
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图 1 基于激光致声的空水跨介质通信
Figure 1. Laser-induced acoustic cross-media communication between air and water
图 2 DFB-FL水听器结构组成
注: PGC为相位产生载波(phase generated carrier); PZT为压电陶瓷(piezoelectric ceramics)
Figure 2. Structure composition of DFB-FL hydrophone
图 4 激光致声通信实验系统的结构示意图
Figure 4. Schematic diagram of laser-induced acoustic communication experimental system
图 5 接收端信号检测处理流程图
Figure 5. Signal detection and processing flowchart at the receiver end
图 6 滑动窗口激光致声信号检测算法
注: MFCC为梅尔频率倒谱系数(Mel frequency cepstrum coefficient)
Figure 6. Detection algorithm of sliding window laser acoustic signal
图 7 不同重复频率的激光声信号
Figure 7. Laser acoustic signals with different repetition frequencies
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