Low-power ultrasonic front-end for cargo container monitoring

A low-power ultrasonic communication system conceived for cargo container monitoring is presented. Two piezoelectric transducers operating at 40 kHz are used for generating and acquiring an ultrasonic signal through the metallic wall, thus establishing a non-invasive inside-outside communication that preserves the container integrity. Both transducers are fixed by means of a novel magnetic case designed for optimizing data transmission. The acoustic and electrical characteristics of the ultrasonic channel are analyzed. An experimental measurement setup based on FPGA has been implemented for comparing some basic modulation and detection schemes in terms of Bit Error Rate (BER), also considering their robustness against undesired mechanical and electromagnetic perturbations. On this basis, a compact digital DBPSK modulator using a square carrier signal is proposed. Frequency and amplitude tracking algorithms are designed for optimizing the quality and robustness of the data transmission. Finally, a low-power low-rate (up to few kbps) architecture based on the previous elements is presented. All the proposed contributions are experimentally validated.This work was supported in part by Spanish Agencia Estatal de Investigación and Fondo Europeo de Desarrollo Regional under Grant TEC2016-80396-C2-1-R, and in part by the Obra Social La Caixa, Fundación Caja Navarra (Convocatoria 2018 de Captación de Talento)