CHARACTERIZING ULTRASONIC TRANSDUCERS USING RADIATION EFFICIENCY AND RECEPTION NOISE-FIGURE

Transducer performance is considered separately for transmission and r eception operations. The transmission operation is traditionally chara cterized by its traditional transfer function. Using a Thevenin source , the transfer function may be scaled to become the absolute radiation efficiency. Transmission lines are accurately modeled, and a matched impedance design is recommended. The reception operation also is chara cterized by its traditional transfer function. However, reception sens itivity is defined as the signal-to-noise ratio achieved by the combin ed transducer, transmission line, and preamplifier. The thermal noise arises from the media and other noise sources contributed by the trans ducer, transmission line, and preamplifier. An absolute sensitivity me asure is defined as the acoustic noise figure, which is the sum of ind ividual transducer and preamplifier noise figures. The transducer nois e figure is independent of the receiver load impedance and depends cri tically on dissipative loss. Preamplifier noise figure performance req uires noise matching to the transducer. High performance design method s are presented that incorporate transmission lines, which include los s. Modeled examples are used to demonstrate performance.