Narrow-band transducer

The oldest techmque for obtaining the ultrasonic transmission characteristic of a material as a function of the frequency is manual tuning of a conventional pulse echo measuring instrument. Of course, tunable and wide-band transmitter and receiver are required to carry out this technique. However, a narrow-band transducer had to be selected according to the test frequency and consequently this techmque is clumsy and rarely used outside the laboratory. 

Compared with conventional heavily damped piezoelectric ceramic transducers, PVDF transmitters show lower efficiency however, the lower transmitting efficiency is fully adequate for narrow-band measurement systems such as time-delay spectrometry. Furthermore, the frequency response of the PVDF transmitters well exceeds the 40 MHz tested here and as such provide a very broadband alternative to traditional ceramic transmitters [19]. 

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