Single-element transducer

The piezoceramics can be fabricated in a number of ways to perform B-mode imaging. In its simplest form, the B-mode transducer is a circular single-element transducer with a fixed geometric focus. To a large degree this type of a transducer has been replaced today by more sophisticated multielement transducers however, there are still commercial systems where single-element transducers are used. The next more complicated designs are annular arrays, which are also circular but. 

Mechanical Steering. The simplest method of beam steering is to use a mechanism to reorient a transducer (usually a circular aperture) to a predetermined set of orientations so as to capture the required two-dimensional data set. This approach was dominant at first however, in the last 15 years, electronically steered systems have become, by far, the most popular. Mechanical systems usually use either a single-element transducer or an annular array transducer (Fig. 25.8). Tlie former will have a fixed focus while the latter does allow the focal point to be moved electronically. This will be discussed more fiilly later. 

Single element transducer fabrication PZTfibers by spinning... 

Figure 6.16 features the electric parallel connection and the mechanical series connection of the stack. Its displacement is the smn of the single element elongations A/. The applied field and the achieved elongation are in line with the polarization, that is, the piezo constant dss is used (longitudinal effect). The transducer can also handle tensile forces, if prestressed with a slotted cylinder casing as shown in Fig. 6.16 or with an anti-fatigue bolt, as is commonly done. 

Foster F, Zhang Y, Zhou YQ et al. (2002) A new ultrasound instrument for in vivo imaging of mice. Ultrasound Med Biol 28 1165-1172. Cannata J, Ritter T, Chen W, et al. (2003) Design of efficient broadband single element (20-80 MHz) ultrasonic transducers for medical imaging. IEEE Trans Ultras Ferroelect Freq Cont 50 1548-1557. 

The Champ-Sons model is a most effieient tool allowing quantitative predictions of the field radiated by arbitrary transducers and possibly complex interfaces. It allows one to easily define the complete set of transducer characteristics (shape of the piezoelectric element, planar or focused lens, contact or immersion, single or multi-element), the excitation pulse (possibly an experimentally measured signal), to define the characteristics of the testing configuration (geometry of the piece, transducer position relatively to the piece, characteristics of both the coupling medium and the piece), and finally to define the calculation to run (field-points position, acoustical quantity considered). 

This system consists of a symmetrical pair of lens elements connected by a small volume of liquid. Each lens consists of a single spherical interface between the liquid and a lens rod. The lens element is formed by polishing a small concave spherical surface in the end of a sapphire rod. At the opposite end of the rod, a thin film piezoelectric transducer is centered on the axis of the lens surface. 

Fig. 1. (a) Structure of eui ion-sensitive FET transducer with single FET element, (b) Structure of an ion-sensitive FET with metal oxide semiconductor FET. D, drain S, source IG, ion-sensitive gate CP, contact pad G, gate RE, reference electrode AS, analyte solution MOSFET, metal oxide semiconductor FET ISFET, ion-sensitive FET. 

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