Noise reduction in infrasound detection

Abstract

Provided are methods, circuits and apparatuses for detecting pressure variations. The circuit can comprise at least two pressure sensors electrically coupled in parallel. At least one pressure sensor can have a differential input and a differential output. The circuit can also comprise a first switching mechanism electrically coupled to the differential input of the at least one pressure sensor. The first switching mechanism can be configured to electrically couple a first current source to the at least one pressure sensor according to a first reference signal. The circuit can also comprise a second switching mechanism electrically coupled to the differential output of the at least one pressure sensor. The second switching mechanism can be configured to electrically couple a second current source to the at least one pressure sensor according to a second reference signal.

What is claimed is: 
     
         1 . A circuit for detecting pressure variations, comprising:
 at least two pressure sensors electrically coupled in parallel, wherein at least one of the pressure sensors comprises a differential input and a differential output;   a first switching mechanism electrically coupled to the differential input of the at least one pressure sensor, the first switching mechanism is configured to electrically couple a first current source to the at least one pressure sensor according to a first reference signal; and   a second switching mechanism electrically coupled to the differential output of the at least one pressure sensor, the second switching mechanism is configured to electrically couple a second current source to the at least one pressure sensor according to a second reference signal.   
     
     
         2 . The circuit of  claim 1 , wherein the first switching mechanism is configured to increase a signal-to-noise ratio of the at least one pressure sensor by a predefined factor. 
     
     
         3 . The circuit of  claim 1 , wherein the second switching mechanism is configured to neutralize an alternating current offset voltage of the at least one pressure sensor. 
     
     
         4 . The circuit of  claim 1 , further comprising an amplifier electrically coupled to the at least two pressure sensors, the amplifier is configured to receive differential signals from the at least one pressure sensor and provide a signal proportional to a difference of voltages of the differential signals, wherein the differential signals received by the amplifier are modified by second switching mechanism. 
     
     
         5 . The circuit of  claim 4 , wherein the second switching mechanism is configured to provide feedback to null an offset directly at the at least one pressure sensor, and wherein the amplifier is optimized for high gain and low noise. 
     
     
         6 . The circuit of  claim 4 , further comprising a bandpass filter electrically coupled to the amplifier, wherein the bandpass filter is configured to receive a signal from the amplifier and provide a portion of the signal within a predefined frequency range. 
     
     
         7 . The circuit of  claim 6 , further comprising a demodulator electrically coupled to the bandpass filter, wherein the demodulator is configured to receive an alternating current (AC) signal from the bandpass filter and provide a direct current (DC) signal. 
     
     
         8 . The circuit of  claim 1 , wherein the at least two pressure sensors have a front and a back, and wherein a back of a first pressure sensor of the at least two pressure sensors faces a back of a second pressure sensor of the at least two pressure sensors. 
     
     
         9 . The circuit of  claim 1 , further comprising a resistor electrically coupled to the first switching mechanism, the resistor is configured to provide a resistance that varies based on changes in temperature. 
     
     
         10 . The circuit of  claim 1 , wherein the at least two pressure sensors comprise a set of resistors configured as a Wheatstone bridge, at least one of the resistors of the set of resistors is configured to provide a resistance that varies based on changes in pressure upon the resistor, and wherein the first reference signal and the second reference signal are phase locked. 
     
     
         11 . The circuit of  claim 1 , wherein the at least two pressure sensors are electrically coupled in parallel and in phase. 
     
     
         12 . The circuit of  claim 1 , wherein the at least two pressure sensors are connected pneumatically in parallel and in phase. 
     
     
         13 . An apparatus for detecting pressure variations, comprising:
 a sensing circuit, comprising,
 at least two pressure sensors electrically coupled in parallel, wherein at least one of the pressure sensors has a differential input and a differential output, 
 a first switching mechanism electrically coupled to the differential input of the at least one pressure sensor, the first switching mechanism is configured to electrically couple a first current source to the at least one pressure sensor according to a first reference signal, and 
 a second switching mechanism electrically coupled to the differential output of the at least one pressure sensor, the second switching mechanism is configured to electrically couple a second current source to the at least one pressure sensor according to a second reference signal; 
   a manifold configured to receive a pressure and communicate the pressure to the at least two pressure sensors; and   a reference chamber configured to provide a reference pressure to the at least two pressure sensors.   
     
     
         14 . The apparatus of  claim 13 , wherein the first switching mechanism is configured to increase a signal-to-noise ratio of the at least one pressure sensor by a predefined factor. 
     
     
         15 . The apparatus of  claim 13 , wherein the second switching mechanism is configured to neutralize an alternating current offset voltage of the at least one pressure sensor. 
     
     
         16 . The apparatus of  claim 13 , wherein the sensing circuit further comprises an amplifier electrically coupled to the at least two pressure sensors, the amplifier is configured to receive differential signals from the at least one pressure sensor and provide a signal proportional to a difference of voltages of the differential signals, wherein the differential signals received by the amplifier are modified by the second switching mechanism. 
     
     
         17 . The apparatus of  claim 13 , wherein the at least two pressure sensors are electrically coupled in parallel and in phase, and wherein the at least two pressure sensors are connected pneumatically in parallel and in phase. 
     
     
         18 . A method for detecting pressure variations, comprising:
 providing a power supply to at least two pressure sensors based on a first reference signal, wherein the at least two pressure sensors are electrically coupled in parallel;   receiving a differential signal from the at least two pressure sensors;   neutralizing, based on a second reference signal, an alternating current offset voltage of the differential signal; and   amplifying the neutralized differential signal.   
     
     
         19 . The method of  claim 18 , wherein amplifying the neutralized differential signal comprises:
 receiving the neutralized differential signal from the at least two pressure sensors; and   amplifying a difference between a voltage of a first signal of the neutralized differential signal and a voltage of a second signal of the neutralized differential signal.   
     
     
         20 . The method of  claim 18 , wherein providing a power supply to the at least two pressure sensors comprises increasing a signal-to-noise ratio of the differential signal by a predefined factor. 
     
     
         21 . The method of  claim 18 , wherein neutralizing the alternating current offset voltage of the differential signal comprises alternating, based on the second reference signal, between providing a current source to a first differential output of the at least two pressure sensors and providing the current source to a second differential input of the at least two pressure sensors. 
     
     
         22 . The method of  claim 18 , wherein the at least two pressure sensors have a front and a back, and wherein a back of a first pressure sensor of the at least two pressure sensors faces a back of a second pressure sensor of the at least two pressure sensors. 
     
     
         23 . The method of  claim 18 , wherein providing a power supply to the at least two pressure sensors comprises alternating, based on the first reference signal, between providing a current source to a first differential input of the at least two pressure sensors and providing the current source to a second differential input of the at least two pressure sensors. 
     
     
         24 . The method of  claim 18 , further comprising filtering the amplified signal within a predefined frequency range. 
     
     
         25 . The method of  claim 24 , wherein the filtered signal is an alternating current (AC) signal, further comprising converting the filtered signal to a direct current (DC) signal. 
     
     
         26 . The method of  claim 18 , wherein providing a power supply to at least two pressure sensors comprises providing a temperature compensating power supply based on a resistor configured to change resistance based on a change in temperature. 
     
     
         27 . The method of  claim 18 , wherein the at least two pressure sensors comprise a set of resistors configured as a Wheatstone bridge, at least one of the resistors of the set of resistors is configured to provide a resistance that varies based on changes in pressure upon the resistor, and wherein the first reference signal and the second reference signal are phase locked. 
     
     
         28 . The method of  claim 18 , wherein neutralizing, based on a second reference signal, an alternating current offset voltage of the differential signal comprises providing feedback to null an offset directly at the at least two pressure sensors, and wherein amplifying the neutralized differential signal is optimized for high gain and low noise. 
     
     
         29 . The method of  claim 18 , wherein the at least two pressure sensors are electrically coupled in parallel and in phase. 
     
     
         30 . The method of  claim 18 , wherein the at least two pressure sensors are connected pneumatically in parallel and in phase.