Theoretical and experimental study of the electrostatic transducer with a nonplanar back plate
Jan Skvor · The Journal of the Acoustical Society of America · 1999
Usually the electrostatic transducer as a microphone or pressure sensor is formed by a circular or rectangular membrane and a planar back electrode with holes. The number, the diameter, and the position of the holes in the back electrode determine the acoustic impedance of the air-gap and especially the damping of the transducer. The aim of this contribution is to show the possibility of the realization of a transducer with a thin diaphragm and a back electrode of convex shape and without holes. The convex shape of the back electrode, because of the nonuniform displacement distribution over the membrane, has a small influence on the transducer sensitivity, but a very high influence on the membrane damping. In the contribution is shown the application of the theory of this type of transducer with a circular membrane vibrating in the fundamental mode with approximate parabolic distribution of membrane displacement and a paraboloidal back electrode without the holes. This transducer modification is applicable for classical and silicon micro-mechanical technologies [Z. Skvor and J. Skvor, Proc. 4th Congress on Acoust., SFA, Marseille (1997), Vol. 1, pp. 63–66].