斜射式超声波跨金属厚壁无线通信系统

跨金属无线传输是超声波通信的重要应用场景之一。实际应用中超声波在金属/超声波换能器界面处因反射而造成回波干扰是这类通信系统的天然缺陷。尽管利用回声消除技术能一定程度地克服回波干扰，但这需要调用大量电路硬件或计算资源。该文在超声波跨金属厚壁通信系统中摒弃传统的直射式探头而选用入射角为45°的斜射式探头作为超声波发射和接收换能器，由于斜射式探头偏转了超声波在金属信道内的反射路径，从而大幅降低换能器接收到的回波。在不进行回波消除的前提下，以STM32为主控芯片和自制信号调理电路搭建了一套斜射式超声波跨金属厚壁无线通信系统，同时将之与选用直射式探头作为超声波换能器的通信系统进行对比验证。研究表明，在接收信噪比方面斜射式系统(19.52 dB)远优于直射式系统(9.24 dB)，在穿透60 mm的厚铝板时系统实时通信速率达到1.2 Mbit/s，并可实现实时声频传输。

Through-metal wireless communication system based on oblique ultrasonic transducers

Through-metal wireless transmission is one of the important application scenarios of ultrasonic communication. In practice, echo interference caused by reflection of ultrasonic waves at the metal/ultrasonic transducer interface is a natural drawback of such communication systems. Although the echo cancellation technologies can overcome echo interference to a certain extent, this consumes a large amount of circuit hardware or computing resources. In this paper, the traditional probe with vertically incident angle is abandoned in the ultrasonic through-metal communication system and an oblique probe with an incidence angle of 45° is chosen as the ultrasonic transmitting and receiving transducers. This type of transducers deflects the reflection paths of ultrasonic waves in the metallic channel and significantly reduces the echoes received by the transducers. Without echo cancellation, one through-metal communication system based on these oblique ultrasonic transducers is built with STM32 as the main control chip, which is meanwhile compared with the system based on vertical ultrasonic transducers. The results show that signal to noise ratio (19.52 dB) of the system based on oblique ultrasonic transducers is much higher than that (9.24 dB) of the one base vertical ultrasonic transducers. When penetrating the thick 60 mm aluminum plate, the system’s communication rate reaches 1.2 Mbit/s. Moreover, it is confirmed that the system can be applied for the wireless real-time transmission of audio signal across metal.