Direct Spread Spectrum Modulation and Dispersion Compensation for Guided Wave-based Communication Systems

Guided wave-based monitoring systems which involve multiple transmitting piezo-transducers permanently in-stalled on structures, often rely on time or frequency-division multiplexing schemes. Alternatively, strategies employing code-division are becoming increasingly popular. These techniques are beneficial since the transmitted signals can be used at the same time for probing the inspected structures and for communicating data. However, to implement effective communication mechanisms, the detrimental effects due to multipath fading and those associated to dispersion and multi-modal propagation, must be counteracted. The objective of this work is to implement an effective GW communication system capable to overcome such mentioned problems and the in-operation mutual interferences between active transmitters. Exploiting a Direct Spread Spectrum modulation scheme, packets of bits encoded by Kasami sequences were conveyed through an aluminum beam instrumented with commercial sensors. The dependency on the amplitude of the actuated pulses as well as well as the influence of the inter-communication distances were specifically evaluated, thus characterizing the performances of the proposed strategy.