SAW transducers are used to measure physical, chemical, and environmental measurands. These transducers consist of a SAW delay line with two IDTs, inserted in the feedback loop of an amplifier as shown in Fig. 5.26.
|Fig 5.26 SAW oscillator.|
The SAW, in traveling between the IDTs, undergoes a phase shift _0, and when the total phase shift _T around the loop is 2nand the total attenuation is less than the amplifier loop gain, the circuit goes into oscillation around the center frequency f0 of the IDT, which is given by nVs/L. The total phaseshiftis