Analysis of Electrical Impedance Matching Effect of Phased Array Ultrasonic Transducers

In phased array ultrasonic testing(PAUT) that acquires S-scan images, a phased array ultrasonic transducer with high sensitivity, high resolution and wide bandwidth is required to effectively distinguish between defect and non-defect signals. To address this, studies have recently been conducted on the design factors of the transducers such as the characteristics of piezoelectric elements, front matching layers, backing materials, and electrical impedance tuning have been recently conducted. Among them, the electrical impedance tuning is one of the most important design factors that control the sensitivity and bandwidth of ultrasonic transducers. In the current study, to improve the resolution and sensitivity of a phased array ultrasonic transducer, an electrical impedance tunning method was suggested. For this, the waveforms of ultrasonic transducers between before and after electrical impedance matching were simulated by applying L-matching or LC-matching circuits coupled with the Krimholtz-Leedom-Matthaei model. Then, the simulated waveforms were compared and analyzed each other. Consequently, based on the simulation outcome, the A-scan waveforms of the fabricated phased array ultrasonic transducer were obtained and its amplitude was increased up to 6 dB. This result demonstrated that the developed method has a great potential to improve the performance of phased array ultrasonic transducers.