Micromachined acoustic transducer and method of operating the same
View Patent ↗This invention relates generally to a micromachined acoustic transducer that has a scalable array of sealed cavities and perforated members forming capacitive cells that convert the electrical signal to acoustic signal or vice versa. It also relates to the method and more particularly to a micromachined acoustic transducer which includes a plurality of micromachined membranes and perforated members forming capacitive cells and more particularly to an acoustic transducer in which the capacitive cells are connected in a scalable array whereby electrical signals are applied to the said array and converted to acoustic signals. The transducer can either be used as an acoustic actuator or a microphone.
1. A micromachined capacitive acoustic transducer including
a plurality of micromachined cells each including a membrane supporting a conductive electrode for movement therewith whereby each electrode forms with perforated members a capacitor whose capacitance varies with movement of the membrane relative to the perforated members;
a cavity region formed by said membrane and a substrate;
a front chamber formed by said membrane and said perforated member; and
conductive lines interconnecting conductive electrodes of adjacent capacitors.
2. A micromachined capacitive acoustic transducer as in claim 1 in which the cells are arranged in a plurality of two-dimensional matrix.
3. A micromachined capacitive acoustic transducer as in claim 1 in which the cells have vacuum evacuated cavities formed by said membranes and the said substrate.
4. A micromachined capacitive acoustic transducer as in claim 1 in which the said membrane and the said perforated members form front chambers.
5. A micromachined capacitive acoustic transducer as in claim 1 in which said perforated members have regular perforation to allow acoustic pressure radiation from said front chambers responsive to the deflection of said membranes.
6. The method of operating a micromachined capacitive acoustic transducer of the type which includes a plurality of micromachined cells arranged in a two-dimensional matrix over a broad frequency band, said cells each comprising a membrane supported by an insulating support above a substrate with a conductive electrode on each of said membrane to form with said perforated member a capacitor, said method comprising:
connecting said cells in series with conductive connecting lines whereby said connecting lines and said capacitors form a capacitive transducer whose capacitance changes with applied electrical signal to the said capacitors;
applying a bias voltage to the said capacitors such that the deflection of said membranes is close to the mid point of the pull-in hysteresis curve;
applying an alternating electrical signal to the said capacitors; and
generating the deflection of said membranes responsive to the said applied electrical signal to provide an acoustic pressure output;
means of connecting to said capacitors for generating acoustic pressure signal.
7. A micromachined capacitive acoustic transducer as in claim 6 in which the cells are arranged in a plurality of two-dimensional matrix.
8. A micromachined capacitive acoustic transducer as in claim 6 in which the cells have vacuum evacuated cavities formed by said membranes and the said substrate.
9. A micromachined capacitive acoustic transducer as in claim 6 in which the said membrane and the said perforated members form front chambers.
10. A micromachined capacitive acoustic transducer as in claim 6 in which said perforated members have regular perforation to allow acoustic pressure radiation from the said front chambers responsive to the deflection of said membrane.
11. The method of operating a micromachined capacitive acoustic transducer of the type which includes a plurality of micromachined cells arranged in a two-dimensional matrix over a broad frequency band, said cells each comprising a membrane supported by an insulating support above a substrate with a conductive electrode on each of said membrane to form with said perforated member a capacitor, said method comprising:
connecting said cells and said perforated members in series with conductive connecting lines;
applying a bias voltage to said capacitors;
determining the change in capacitance of said cells in responsive to a received acoustic pressure signal to provide an output signal representative of the acoustic pressure signal; and
means of connecting to said capacitors for generating electrical signal.
12. A micromachined capacitive acoustic transducer as in claim 11 in which the cells are arranged in a plurality of two-dimensional matrix.
13. A micromachined capacitive acoustic transducer as in claim 11 in which the cells have vacuum evacuated cavities formed by said membranes and the said substrate.
14. A micromachined capacitive acoustic transducer as in claim 11 in which the said membrane and the said perforated members form front chambers.
15. A micromachined capacitive acoustic transducer as in claim 11 in which said perforated members have regular perforation to allow the passage of acoustic pressure impinging on said membrane.
16. A micromachined capacitive acoustic transducer as in claim 1 or 6 or 11 in which the membranes and perforated members are circular or rectangular or square.