Optimization and operation of interdigital transducer to improve signal-to-noise ratio

•The coupling mechanism between the transducer and the waveguide is analyzed for optimizing the IDT.•The structural parameters’ effects on the wavelength selection characteristics of IDT is investigated.•The IDT with unequal finger width is optimized with a genetic algorithm, to suppress harmonic components and improve the target mode SNR by at least 5 dB.•The experimental results show that the amplitude of the stray mode decreases by 94.77 % in the optimized IDT, compared with the traditional ones. This study presents a novel optimization method for Lamb wave mode selective transducers, surpassing traditional interdigital transducers (TIDT) by employing non-uniform electrode widths to suppress harmonic components. Utilizing a frequency domain finite element model (FDFEM), the coupling mechanism between the double-sided interdigital transducer (DS-IDT) and the waveguide is analyzed, forming the optimization basis. By discussing key parameters affecting wavelength selection characteristics, an optimization scheme is formulated. Employing a multi-objective genetic algorithm, the strategy focuses on minimizing the ratio of stray to target mode as the cost function, resulting in significant signal-to-noise ratio (SNR) improvements. Compared to TIDTs, SNR gains of at least 4.7 dB at 70 kHz and 8.8 dB at 400 kHz are achieved. Laboratory experiments validate the superior mode selection performance of the optimized interdigital transducer (OIDT) over ordinary piezoelectric wafer (OPW) and TIDT, demonstrating a significant reduction of 48.82 % in stray S0 mode amplitude at 70 kHz and 94.77 % in stray A2 mode amplitude at 400 kHz. This method ensures high SNR for target mode signals, simplifying feature extraction and enhancing structural health monitoring capabilities.