## 5aEA7. DK model for electrostatic ultrasonic transducers with V-grooved backplates.

### Session: Friday Morning, December 6

### Time: 9:30

**Author: Li-Feng Ge**

**Location: Anhui Inst. of Metrology and Measurement, 30 Ma An Shan Rd., ABTS, Hefei, Anhui 230001, China**

**Abstract:**

A new model for electrostatic ultrasonic transducers with V-grooved
backplates is developed. The model treats the diaphragm of the transducer as a
plate supported by an air spring. Since the tension is usually not used and
unnecessary, only the bending stiffness of the diaphragm, D, and the air-gap
spring stiffness, K, are taken into account. It is revealed by the DK model that
the first resonant frequency of the transducer stems from the air-gap spring,
like a Helmholtz resonator, and the second resonant frequency corresponds to the
first mode frequency of the diaphragm vibrating as a thin plate. The motion of
the diaphragm can be described approximately by the combined contributions of
the two parts. According to the theory, a wider bandwidth can be obtained by
designing the second resonant frequency to be near the first one with an
appropriate selection of geometric dimensions and material parameters. For a
typical V-grooved transducer with an 8-(mu)m-thick Mylar diaphragm and a 0.5-mm
pitch air gap, the first resonant frequency predicted by the model is 50.9 kHz,
and the second one is 78.6 kHz. The prediction is consistent with experimental
results. [Work supported by Anhui Natural Science Foundation of China.]

ASA 132nd meeting - Hawaii, December 1996