Monitoring displacement of a membrane in an electrostatic acoustic device
AssigneeWaves Audio Ltd.
InventorsGabriel Zeltzer, Meir Shaashua
Life of this patent
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Abstract
Monitoring time-dependent displacement of a membrane in an electrostatic acoustic device. An oscillator is configured to produce a probe signal varying at radio frequency. The probe signal is symmetrically coupled into the first and second electrodes. DC bias voltages are symmetrically applied to the first and second electrodes. A voltage signal from the membrane is sensed and input at a high pass filter input. A multiplier is configured to input the filtered signal modulated at radio frequency and portion of the probe signal. The multiplier is configured to output a multiplied signal which is demodulated to produce therefrom an audio output signal responsive to the time-dependent displacement of the membrane.
Claims17
A method for monitoring time-dependent displacement of a membrane in an electrostatic acoustic device, including the membrane, a first electrode and a second electrode, wherein the first electrode is disposed parallel to the membrane, wherein the membrane is configured to respond mechanically to a varying first electric field in accordance with respective electric potentials applied between the first electrode and the membrane, wherein the second electrode is disposed parallel to the membrane opposite from the first electrode, wherein the membrane is configured to respond mechanically to a varying second electric field in accordance with respective electric potentials applied between the second electrode and the membrane, the method comprising:
- producing a probe signal varying at radio frequency;
- first coupling a portion of the probe signal into the first electrode;
- second coupling a transformed portion of the probe signal into the second electrode;
- first applying a first DC bias voltage to the first electrode;
- second applying a second DC bias voltage to the second electrode, wherein the second DC bias voltage has an opposite polarity from the first DC bias voltage;
- inputting an audio voltage to the membrane;
- sensing a voltage signal from the membrane;
- inputting at a high pass filter input the voltage signal from the membrane, the high pass filter selectively passing at least a portion of the radio frequency of the probe signal and selectively blocking at least a portion of audio frequency to produce a filtered signal modulated at the radio frequency;
- inputting at a first multiplier input at least a portion of the filtered signal modulated at the radio frequency;
- inputting at a second multiplier input, at least a portion of the probe signal;
- outputting a multiplied signal proportional to a multiplication of the filtered signal and the probe signal at the first multiplier input and second multiplier input;
- and
- demodulating the multiplied signal thereby producing an audio output signal responsive to time-dependent displacement of the membrane.
A circuit for time-dependent monitoring displacement of a membrane in an electrostatic acoustic device, including the membrane, a first electrode and a second electrode, wherein the first electrode is disposed parallel to the membrane, wherein the membrane is configured to respond mechanically to a varying first electric field in accordance with respective electric potentials applied between the first electrode and the membrane, wherein the second electrode is disposed parallel to the membrane opposite from the first electrode;
- wherein the membrane is configured to respond mechanically to a varying second electric field in accordance with respective electric potentials between the second electrode and the membrane, the circuit comprising:
- an oscillator configured to produce a probe signal varying at radio frequency;
- a first coupler configured to couple a portion of the probe signal into the first electrode;
- a second coupler configured to couple a transformed portion of the probe signal into the second electrode;
- a first direct current (DC) bias supply configured to apply a first DC bias voltage to the first electrode;
- a second direct current (DC) bias supply configured to apply a second DC bias voltage to the second electrode, wherein the second DC bias voltage has an opposite polarity from the first DC bias voltage;
- an audio voltage input configured to input an audio voltage to the membrane;
- a voltage signal output from the membrane;
- a high pass filter input connectable to the voltage signal output from the membrane, the high pass filter configured selectively pass at least a portion of radio frequency and to selectively block at least a portion of audio frequency to produce a filtered signal modulated at radio frequency;
- a multiplier configured to input at a first multiplier input at least a portion of the filtered signal modulated at radio frequency and to input at a second multiplier input at least a portion of either the probe signal or an inverted probe signal, wherein the multiplier is configured to output a multiplied signal proportional to a multiplication of signals at the first multiplier input and second multiplier input;
- a demodulator configured to input the multiplied signal output from the multiplier and demodulate therefrom an audio output signal responsive to the time-dependent displacement of the membrane.
Dependencies are inferred from the claim text.