Interdigitated transducers

Figure 3.18 Interdigital transducer, formed by patterning electrodes on the surface of a piezoelectric crystal, for exciting surface acoustic waves (a) SAW electrical potential,...

When an array of fingers is excited, as occurs with an interdigital transducer (IDT), the wave potential for a rightward propagating wave evaluated at position z is a vector sum of the contributions from each linger ... 

Figure 3.21 The frequency response measured between a pair of interdigital transducers. (Reprinted with pemission.

In the SAW, APM, and FPW devices, the wavelength is determined by the spatial periodicity of the interdigital transducer, while the thicknesses of the APM... 

The excitation and detection of surface acoustic waves, flexural plate waves, and other plate waves on piezoelectric substrates is most readily accomplished by use of an interdigital transducer (IDT) first reported by White and Voltmer [6]. The comb-like structure of the IDT, illustrated in Figure 6.4, is typically made from a lithographically patterned thin film that has been deposited onto the surface of a piezoelectric substrate or thin film. The metal film used to make the IDT must be thick enough to offer low electrical resistance and thin enough so that it does not present an excessive mechanical load to the AW. Typical IDTs are made... 

Figure 6.4 Characteristic features of the interdigital transducer (IDT) used for acoustic wave excitation. The transducer periodicity, d, is equivalent to the acoustic wavelength.

Much of the interest has been focused on the type of device that operates as a delay line device which can be configured to monitor either changes in amplitude or velocity. The device consists of two interdigital transducers, an emitter of the SAW, and and a detector of the wave. The resonant frequency... 

An interdigital transducer on the surface of a piezoelectric material can excite and detect waves which propagate along the surface (e.g. the SAW) or through the bulk (e.g. the Lamb wave and the SH-APM) of the substrate. AW sensors typically include an input transducer to generate the wave, an interaction region in which the propagating wave is affected by its environment, and an output transducer to detect the wave. Thus, unlike the quartz crystal microbal-... 

Figure 1. Schematic of a SAW device as the feedback element of an oscillator circuit. Input and output interdigital transducers are used to excite and detect a SAW in the piezoelectric ST-cut quartz substrate.

The most efficient and widely used means of generating and detecting surface elastic waves for electronic applications is the interdigital transducer shown in Fig. 2. In its simplest form it consists of a series of parallel metal plate electrodes periodically spaced on the surface of a piezoelectric substrate. The transducer is a three-port device one electrical and two acoustic. When an alternating voltage is applied to its electrical port, time varying electric fields are set up within the substrate, and these excite alternating stress pattern via the piezoelectric effect. The electric field... 

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