Microelectromechanical correlation device and method

An apparatus for comparing a time-varying reference signal r(t) to a time-varying force, comprising:

• first and second electrically conductive plates disposed a distance d apart from each other such that points on the first plate are at least approximately distance d away from points on the second plate;
• an actuator for changing the distance d between the two plates in response to the time-varying force;
• a current source for driving a time-varying current between the first and second plates, the current being i(t) corresponding to the reference signal r(t);
• and
• a voltage output coupled to said first and second electrically conductive plates, said voltage output providing a voltage which reflects a correlation function between the time-varying reference signal and the time-varying force.

A method of comparing a first time-varying relationship to a second time-varying relationship, comprising the steps of:

• supporting a first conductive signal plate such that it is separated from a first conductive reference plate by a variable distance d;
• supporting a second conductive signal plate such that it is separated from a second conductive reference plate by a distance controlled by said variable distance d;
• applying a first electrical drive signal to said first conductive signal plate with respect to said first conductive reference plate such that said variable distance d changes as a function of said first electrical drive signal, where said first electrical drive signal is a known function of said first time-varying relationship;
• applying a second electrical drive signal to said second conductive signal plate with respect to said second conductive reference plate, said second electrical drive signal being a known function of said second time-varying relationship;
• and
• measuring a resultant electrical signal between said second conductive signal plate and said second conductive reference plate, said resultant electrical signal representing a correlation between said first and second time-varying relationships.

An apparatus for correlating a time-varying reference signal with a time-varying pressure signal, the apparatus comprising:

• a substrate;
• a first conductive pad deposited on said substrate;
• a capacitive plate deposited on said substrate;
• a plate supporting beam disposed above said capacitive plate, said plate supporting beam comprising a conductive upper plate contained with an insulating layer, said upper plate disposed a distance d above said capacitive plate, said upper plate electrically coupled to said first pad and said plate supporting beam mechanically coupled to said substrate at said first pad;
• a current source coupled to said capacitive plate and said first pad, said current source providing a current output corresponding to the time-varying reference signal;
• a diaphragm adapted to receive the time-varying pressure signal, said diaphragm disposed above said upper plate and having a perimeter sealed to said substrate;
• and
• a voltage output coupled to said first pad and said capacitive plate, said voltage output providing a voltage which reflects a correlation function between the time varying reference signal and the time-varying pressure signal.

An apparatus for correlating a time-varying reference signal with a time-varying input signal, the apparatus comprising:

• a substrate;
• a first conductive pad deposited on said substrate;
• a capacitive plate deposited on said substrate;
• a conductive anchor plate deposited on said substrate;
• a plate supporting beam disposed above said capacitive plate and said electrostatic plate, said plate supporting beam comprising a conductive upper plate contained with an insulating layer, said upper plate disposed a distance d above said capacitive plate, said upper plate electrically coupled to said first pad and said plate supporting beam mechanically coupled to said substrate at said first pad;
• a current source coupled to said capacitive plate and said first pad, said current source providing a current output corresponding to the time-varying reference signal;
• a voltage input coupled to said upper plate and said anchor plate, said anchor plate providing a voltage corresponding to the time-varying input signal;
• and
• a voltage output coupled to said first pad and said capacitive plate, said voltage output providing a voltage which reflects a correlation function between the time-varying reference signal and the time-varying input signal.