Force balance microphone
AssigneeBorealis Technical Limited
InventorsJonathan Sidney Edelson, Nicholas Paul Ward
Life of this patent
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Abstract
The present invention is a microphone that applies the principle of negative feedback directly to the diaphragm, greatly reducing the non-linearity of the diaphragm. In a further embodiment, digital negative feedback is used, incorporating the diaphragm into the digitization loop of a sigma-delta converter, creating a direct sound pressure to digital electrical output converter. In one embodiment, positive feedback is used in an analog circuit, causing a negative feedback response on the diaphragm.
Claims15
A microphone system for the detection of pressure variations in a medium, comprising:
- transduction means for the conversion of said pressure variations into displacement of said transduction means;
- detection means for the conversion of said displacement into variations of an electrical output;
- feedback means for the cancellation of said displacement, whereby nonlinearities of said transduction means or said detection means are reduced or eliminated from the output of said microphone system;
- wherein said transduction means is a metal ribbon, wherein said detection means is a tunneling current detector arranged proximally to said metal ribbon, said tunneling current detector consisting of a probe and a transimpedance amplifier, a suitable bias voltage being applied between said metal ribbon and said tunneling current detector, wherein said feedback means is analog electromagnetic feedback, said analog electromagnetic feedback consisting of a comparator taking as input the output of said tunneling current detector and a reference voltage, said comparator charging an integrating capacitor, said integrated comparison result controlling a variable current source supplying current to said metal ribbon, said metal ribbon mounted in a magnetic field transverse to the plane of said ribbon, whereby displacements in the position of said ribbon will be detected, causing the production of a current through said ribbon which will cause a restoring force to be developed in said ribbon.
A microphone system for the detection of pressure variations in a medium, comprising:
- transduction means for the conversion of said pressure variations into displacement of said transduction means;
- detection means for the conversion of said displacement into variations of an electrical output;
- feedback means for the cancellation of said displacement, whereby nonlinearities of said transduction means or said detection means are reduced or eliminated from the output of said microphone system;
- wherein said transduction means is a conductive diaphragm, wherein said detection means is a tunneling current detector arranged proximally to the center of said conductive diaphragm, said tunneling current detector consisting of a probe and a transresistance amplifier, a suitable bias voltage being applied between said conductive diaphragm and said tunneling current detector, wherein said feedback means is digital electrostatic feedback, said digital electrostatic feedback consisting of a latching comparator taking as input the output of said tunneling current detector and a reference voltage, said comparator further receiving as input a sampling clock, said comparator producing a binary output which is fed to a one bit digital to analog converter, said output of said one bit digital to analog converter varying the potential on a backplate, said backplate being proximal to said conductive diaphragm, whereby displacements in the position of said conductive diaphragm will be detected, causing a change in potential of said backplate, resulting in a restoring force applied to said conductive diaphragm.
A microphone system as in claim 7, wherein said pressure variations in a medium are acoustic pressure variations in air.
A method for converting sound to an output signal, comprising:
- allowing said sound to displace a transduction means;
- detecting the movement of said transduction means, thereby creating an initial signal;
- generating a feedback signal from said initial signal;
- restoring said transduction means to an equilibrium position using said feedback signal;
- forming said output signal;
- and
- altering said output signal using inverting amplification to decrease apparent transducer impedance and increase transducer current flow.
The method of claim 8, wherein said output signal is selected from the group consisting of said input signal, said feedback signal, a combination of said input signal and said feedback signal, whereby nonlinearities of said transduction means are reduced or eliminated from said output signal.
The method of claim 9, wherein said inverting amplification is selected from the group consisting of operational amplifiers, discrete transistors, MOSFETs, FETs, valves, and unijunction transistors.
A microphone system for the detection of a pressure variation in a medium, comprising:
- transduction means for converting said pressure variation into a displacement of a conductor in a magnetic field;
- said conductor connected electrically, in series, to a negative impedance circuit, wherein the impedance of said conductor and said negative impedance circuit is minimized;
- and
- wherein the displacement of said conductor causes a high current to flow in said conductor which reacts with said magnetic field causing a magnetic reaction force acting against said displacement.
Dependencies are inferred from the claim text.