1990 Volume 11 Issue 6 Pages 335-341
A wide range ceramic microphone using a round flat type diaphragm is described in this research report. Use of the ceramic electrode diameter as the parameter is proposed for setting of the upper frequency limit. A concentric mode of vibration will appearin the vicinity of the secondary and tertiary resonance frequencies in the range above the primary resonance frequency of the diaphragm. Since the generated voltagewill be the highest at this center (inside the inflection point), the maximum power can be obtained by determining the electrode diameter according to the frequency. When high voltage obtained from this maximum power is supplied to the FET, a large output voltage can be obtained with the optimum signal-to-noise ratio. The performancecharacteristics which were realized by this prototype capsule of ∅23.77 are Sensitivity:-40.2 dB/Pa. 1 kHz; Electrostatic capacity: 118 pF, and Frequency response:±2.5dB at 20Hz to 20kHz.
