The effect of metal load material and impedance matching on EMAT performance

摘要

The terminal impedance of a flat spiral coil EMAT is simulated by means of a simple two-port transformer model from which the expected transmission and reception sensitivities can be derived. It extends earlier work by comparing those properties between operation into ferritic steel or aluminium loads. The analysis is further developed for the case when the EMAT coil is tuned to a specific frequency by means of a series capacitor and matched to transmitter, receiver and cable impedances, typically 50 Ω. A signal-to-noise performance measure is derived as a product of transmission sensitivity and a reciprocal noise figure for signal reception.