Optimization of capactive microphone and pressure sensor performance by capacitor-electrode shaping

Abstract

In many designs of capacitive microphones or pressure sensors the electrode size is chosen to be equal to the diaphragm size. In this paper it will be discussed whether an electrode size or shape that differs from that of the diaphragm is attractive for obtaining a maximum value for the sensor sensitivity and the signal-to-noise ratio. A theoretical analysis will be given for circular diaphragms and electrodes, from which it can be shown that for maximum sensitivity the electrode should be located at the centre of the diaphragm, with a radius depending on the value of the amplifier input capacitance.

Theory and analysis of electrode size optimization for capacitive microfabricated ultrasonic transducers

“…Hence, the undeflected Z a is still valid, and DC and AC displacements can be computed separately and summed to yield the overall movement of the membrane. In other words, if T (r, t) = T DC (r) + T AC (r) sin ωt (15) with…”

“…Although electrode patterning has been used for selective mode excitation of resonators [14] and in the optimization of capacitive pressure transducers and microphones [15], no group, to our knowledge, has used electrode patterning to optimize the performance of capacitive microfabricated ultrasonic transducers (cMUTs). In this paper, we present optimization criteria, analyses, and simulations that demonstrate that electrode patterning can be used to enhance the performance of cMUTs significantly.…”

Chemical and physical FET-based sensors or variations on an equation

“…These edges do not add to the signal and can be considered as parasitic capacitances. This offers an interesting possibility for optimizing the sensitivity: it turns out that providing the elastic material only partly with a conducting gate offers maximal sensitivity [3].…”