WO2002060215A2 - Microphone sans batterie, sans fil - Google Patents

Microphone sans batterie, sans fil Download PDF

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Publication number
WO2002060215A2
WO2002060215A2 PCT/US2002/001497 US0201497W WO02060215A2 WO 2002060215 A2 WO2002060215 A2 WO 2002060215A2 US 0201497 W US0201497 W US 0201497W WO 02060215 A2 WO02060215 A2 WO 02060215A2
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WO
WIPO (PCT)
Prior art keywords
sensor
circuit
reader
sensor circuit
passive
Prior art date
Application number
PCT/US2002/001497
Other languages
English (en)
Other versions
WO2002060215A3 (fr
Inventor
Haruhiko H. Asada
Original Assignee
Massachusetts Institute Of Technology
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Massachusetts Institute Of Technology filed Critical Massachusetts Institute Of Technology
Publication of WO2002060215A2 publication Critical patent/WO2002060215A2/fr
Publication of WO2002060215A3 publication Critical patent/WO2002060215A3/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R19/00—Electrostatic transducers
    • H04R19/04—Microphones

Definitions

  • the present invention pertains to a method and apparatus for capturing sounds and vibration with wireless and battery-less microphones.
  • Mobile telephony e.g. cellular phone and personal handy-phone system (PHS)
  • PHS personal handy-phone system
  • a patient can be connected to a service network of physicians and caretakers anywhere at any time.
  • the physicians and caretakers can monitor the patient's condition, both physiological and behavioral, remotely and continually, in the home as well as in hospitals. This would expedite and streamline the patient's recovery process, improve the quality of life, prevent disastrous and costly failures, and promote preventive and behavioral medicine.
  • Sensors for detecting vibration and acoustic signals from the body include stethoscopes and microphones.
  • Stethoscopes monitor physiological sounds at only a single location and must typically be held in place by a clinician.
  • Microphones for health monitoring typically use cables connecting the microphones to a control box, an arrangement that may be cumbersome.
  • a passive microphone and a reader there is provided a passive microphone and a reader.
  • the passive microphone has a sensor for converting vibrations into variations in a resonant frequency of a sensor circuit, while the reader remotely detects the variations in the resonant frequency of the sensor circuit and generates an electrical signal related to the variations in the resonant frequency of the sensor circuit.
  • the senor in the conversion of vibrations into variations in a resonant frequency of a sensor circuit, may vary a reactive component of the sensor circuit, and, more particularly, a capacitive component, thereby varying the resonant frequency of the sensor circuit.
  • the reader may be inductively coupled to the sensor circuit.
  • the sensor may be attached to a person, such as by coupling to the skin of the person.
  • a method for monitoring a person.
  • the method has a first step of attaching a passive microphone, either in direct or indirect contact with the patient. Indirect contact may include attachment to the clothes of the patient.
  • the method has the further steps of wirelessly coupling the passive microphone to a remotely disposed reader carried by the patient and transmitting the signal from the reader to a remote receiver.
  • a method is provided for remotely detecting vibrations. Exposure of a passive microphone sensor to vibrations alters the resonance frequency of a sensor circuit containing the passive microphone sensor. Wireless coupling of the sensor circuit to a reader circuit alters the impedance of the reader circuit. Excitation of the reader circuit over a range of frequencies encompassing the resonance frequency of the sensor circuit identifies the current resonance frequency, and, consequently, the current vibration of the passive microphone sensor.
  • FIG. 1 is a schematic description of the relationship between a passive microphone, a reader, and a remote receiver in the transmission of vibrational information remotely in accordance with embodiments of the invention.
  • FIG. 2 depicts an application of a wireless microphone in accordance with embodiments of the invention;
  • FIG. 3 contains equivalent circuit diagrams of the sensor circuit and reader circuit of FIG. 2, in accordance with an embodiment of the present invention
  • FIGS. 4a-4c depict the time variation of the frequency of the input voltage to the read circuit, the voltage generated in the read circuit in response to the read circuit input voltage, and the processed read circuit voltage;
  • FIG. 5 shows a spectrum of the voltage generated in the read circuit exhibiting a dip corresponding to the instantaneous effective capacitance of the passive microphone sensor, in accordance with an embodiment of the present invention.
  • a passive microphone captures sounds and vibrations and transmits the signals wirelessly to a reader without battery power.
  • the reader subsequently transmits the signals wirelessly to a receiver.
  • One application described without limitation, is that of hands-free mobile phone operation, where the passive microphones are attached to the clothes, or directly to the skin of the wearer, and the voice signals are wirelessly transmitted to the mobile phone of the wearer. More advanced applications include wearable health monitoring, where the microphones attached to the patient detect vital signs and other behavioral signals.
  • FIG. 1 illustrates elements of one embodiment of the invention.
  • Wireless microphone 100 comprises a passive microphone 110 and a reader 120.
  • Passive microphone 110 comprises a sensor circuit 112 that, in turn, comprises a sensor 114. Vibrations to sensor 114 alter the electrical characteristics of sensor circuit 112. These electrical characteristics are detected wirelessly and electrically by reader circuit 122 and alter its electrical performance. The electrical performance of reader circuit 122 is next communicated wirelessly to receiver 130.
  • Passive microphone sensors are passive condenser microphones embedded in a sensor circuit with wireless links to a reader. As shown in FIG. 2, one embodiment comprises passive microphones attached to the skin to detect voice sounds (210), to detect vibrations of the cartoid artery (220, 222, and 224), and to monitor the neck and chest (231, 232, 233, 234, and 235) with reader 240 hung around the neck.
  • FIG. 3 illustrates schematically the interaction between embodiments of a passive microphone 110 and a reader 120.
  • Sensor circuit 112 comprises a condenser microphone sensor 315 and a coil 330 with a small resistance 325.
  • Sensor passive microphone 110 has no battery, it is a passive device.
  • a diaphragm 355 of sensor 315 moves, thereby altering the capacitance, C m , presented by condenser microphone sensor 315 to sensor circuit 112. This causes a change in the resonant frequency of sensor circuit 112, the RLC circuit formed by coil 330 with inductance L 2 , and condenser microphone sensor 315 with capacitance C m .
  • passive microphone 110 converts the diaphragm motion to a change in the resonant frequency, f res .
  • Reader 120 hung from the neck detects this resonant frequency wirelessly through inductive coupling 375 between coil 330 in sensor circuit 112 and coil 355 in reader circuit 122.
  • Reader circuit coil 355 is placed in the near field, i.e. less than (wave length)/(2 ⁇ )) so that an inductive coupling with sensor circuit coil 330 may be formed.
  • the two coils form a type of transformer in the air with mutual inductance M.
  • Reader 120 has a voltage source 370 providing a high frequency oscillatory voltage, u 0 . Through the inductive coupling, this induces a current 265 (i ) in sensor circuit 112.
  • the impedance of sensor circuit 112 viewed from reader circuit 340 is maximum when the frequency of oscillatory voltage 370 (uo) agrees with the resonant frequency, f res , of sensor circuit 112. In turn, this changes current 360 (ii) of reader circuit 340, which is detected by the voltage drop across resistor 345 (Rj.). To increase the sensitivity of the voltage drop, reader circuit 340 is made into a resonant circuit.
  • capacitor 350 ( ) creates a resonance so that the voltage drop at coil 355 (Li) cancels with that of capacitor 350 ( ) at the resonant frequency.
  • f reS the excitation frequency of reader circuit
  • FIGS. 4a-4c show the process of reading the resonant frequency of sensor circuit 112.
  • saw- toothed waveform 410 illustrates periodic sweeping of the excitation frequency superimposed on acoustic waveform 420.
  • waveform 430 shows that when the excitation frequency of reader circuit 340 matches the resonant frequency of sensor circuit 112 f r e S) a sharp reduction in reader circuit current 360 (ii) is observed and manifests itself in a sharp drop in voltage across resistor 345 (Ri).
  • Peak detection circuit 347 in reader circuit 340 identifies this timing and converts the dips in resistor 345 voltage to diaphragm 355 displacement of the condenser microphone sensor.
  • the series of step changes in waveform 440 in FIG. 4c show the sampled data output from reader circuit 340.
  • sinusoidal current 360 (ii) of frequency -yin reader circuit coil 355 induces current 365 (i 2 ) in sensor circuit coil 330 through mutual inductance M, yielding the following relationship.
  • reader circuit 340 satisfies
  • u 0 R.- j + j ⁇ L. • i j -I j oM • i 2 j ⁇ C 1 where u 0 is the voltage of source 370.
  • the total impedance of sensor circuit 112 viewed from reader circuit 122 is given by ⁇ 2 M 2
  • This transformed sensor circuit impedance varies as the capacitance of the passive microphone sensor 315 changes and the frequency of the reader circuit excitation is varied.
  • the excitation frequency matches the sensor circuit resonant frequency
  • a sudden increase in the transformed sensor circuit impedance Z occurs.
  • FIG. 5 shows a simulation result for the above parameter selection. Gaussian noise is added to the system. Sensor condenser microphone 315 is assumed to vary its capacitance between 5.85 pF and 6.15 pF. Parameters of other circuit elements are selected from their specifications and data sheets. Observed voltage 510 across reader circuit resistor 345 is readily distinguishable above the noise.
  • the process of reading out the passive microphone output has several features. First, although the magnitude of the voltage drop varies depending on the mutual inductance M, the acquired data of the passive microphone output may not directly be influenced. Peak detection circuit 347 detects only the time at which the excitation frequency agrees with the resonant frequency of the sensor circuit. Although the magnitude of the voltage across resistor 345 (Ri) varies depending on the relative location between reader coil 355 and the sensor circuit coil 330, the timing does not change. Also, use of a saw-toothed waveform resembles the basic principle of pulse width modulation and analog to digital conversion, an inherently digital and robust process.
  • passive microphone 110 does not require a battery, making the passive microphone very simple, small, and potentially disposable.
  • a passive microphone is preferably less than a few millimeters in diameter and less than 5 mm in length.
  • a passive microphone sensor is a condenser microphone well suited for miniaturization through micro-electromechanical systems (MEMS) technology. With a diameter of less than 2mm, a passive microphone sensor can be easily attached to the skin with adhesive.
  • MEMS micro-electromechanical systems

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Transmitters (AREA)
  • Measuring And Recording Apparatus For Diagnosis (AREA)

Abstract

La présente invention concerne un microphone sans batterie, sans fil. Un microphone passif contenant un circuit détecteur de résonance et un détecteur réactif sensible à la vibration peut être couplé à distance à un circuit récepteur sensible à la résonance du circuit détecteur. La surveillance de la variation de fréquence du circuit récepteur peut révéler jusqu'à quel point le détecteur est sujet aux vibrations. Dans un mode de réalisation, le détecteur est un microphone à condensateur passif incorporé dans un circuit RLC, à son tour relié par couplage inductif à un circuit récepteur. La vibration du diaphragme du microphone à condensateur modifie la capacité du condensateur et la fréquence de résonance du circuit détecteur de résonance. Le circuit récepteur est sensible aux changements de son impédance induite par le changement d'impédance du circuit détecteur de résonance. L'invention concerne également, dans un mode de réalisation, un procédé de surveillance d'une personne, un microphone passif étant directement ou indirectement fixé à la personne. Le microphone passif est couplé à un lecteur disposé à distance porté par la personne et est ensuite transmis à un récepteur éloigné. Dans un dernier mode de réalisation, l'invention concerne un procédé permettant de détecter à distance des vibrations, un détecteur à microphone passif exposé à des vibrations modifiant la fréquence de résonance d'un circuit détecteur contenant ledit détecteur. Le couplage sans fil du circuit détecteur à un circuit lecteur change l'impédance du circuit lecteur qui est détectable lors de l'excitation séquentielle du circuit lecteur sur une plage de fréquences qui comprend la fréquence de résonance.
PCT/US2002/001497 2001-01-26 2002-01-17 Microphone sans batterie, sans fil WO2002060215A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US26453001P 2001-01-26 2001-01-26
US60/264,530 2001-01-26

Publications (2)

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WO2002060215A2 true WO2002060215A2 (fr) 2002-08-01
WO2002060215A3 WO2002060215A3 (fr) 2003-04-17

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008018069A3 (fr) * 2006-08-07 2008-03-20 Deepbreeze Ltd matrice de microphones pour enregistrer des bruits corporels
US9774086B2 (en) 2007-03-02 2017-09-26 Qualcomm Incorporated Wireless power apparatus and methods

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9130602B2 (en) 2006-01-18 2015-09-08 Qualcomm Incorporated Method and apparatus for delivering energy to an electrical or electronic device via a wireless link
US9124120B2 (en) 2007-06-11 2015-09-01 Qualcomm Incorporated Wireless power system and proximity effects
US9601267B2 (en) 2013-07-03 2017-03-21 Qualcomm Incorporated Wireless power transmitter with a plurality of magnetic oscillators

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3561430A (en) * 1967-07-20 1971-02-09 William W Filler Jr Fetal heartbeat rate instrument for monitoring fetal distress
US4323999A (en) * 1980-02-29 1982-04-06 Pilot Mannenhitsu Kabushi Kaisha Automatic transmission or recording or transmission and reception control system
US4591668A (en) * 1984-05-08 1986-05-27 Iwata Electric Co., Ltd. Vibration-detecting type microphone
US5109863A (en) * 1989-10-26 1992-05-05 Rutgers, The State University Of New Jersey Noninvasive diagnostic system for coronary artery disease
US5425104A (en) * 1991-04-01 1995-06-13 Resound Corporation Inconspicuous communication method utilizing remote electromagnetic drive
US5793875A (en) * 1996-04-22 1998-08-11 Cardinal Sound Labs, Inc. Directional hearing system
US6084516A (en) * 1998-02-06 2000-07-04 Pioneer Electronic Corporation Audio apparatus
US6368283B1 (en) * 2000-09-08 2002-04-09 Institut De Recherches Cliniques De Montreal Method and apparatus for estimating systolic and mean pulmonary artery pressures of a patient
US6415033B1 (en) * 1999-09-15 2002-07-02 Ilife Systems, Inc. Physiological condition monitors utilizing very low frequency acoustic signals

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3561430A (en) * 1967-07-20 1971-02-09 William W Filler Jr Fetal heartbeat rate instrument for monitoring fetal distress
US4323999A (en) * 1980-02-29 1982-04-06 Pilot Mannenhitsu Kabushi Kaisha Automatic transmission or recording or transmission and reception control system
US4591668A (en) * 1984-05-08 1986-05-27 Iwata Electric Co., Ltd. Vibration-detecting type microphone
US5109863A (en) * 1989-10-26 1992-05-05 Rutgers, The State University Of New Jersey Noninvasive diagnostic system for coronary artery disease
US5425104A (en) * 1991-04-01 1995-06-13 Resound Corporation Inconspicuous communication method utilizing remote electromagnetic drive
US5793875A (en) * 1996-04-22 1998-08-11 Cardinal Sound Labs, Inc. Directional hearing system
US6084516A (en) * 1998-02-06 2000-07-04 Pioneer Electronic Corporation Audio apparatus
US6415033B1 (en) * 1999-09-15 2002-07-02 Ilife Systems, Inc. Physiological condition monitors utilizing very low frequency acoustic signals
US6368283B1 (en) * 2000-09-08 2002-04-09 Institut De Recherches Cliniques De Montreal Method and apparatus for estimating systolic and mean pulmonary artery pressures of a patient

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008018069A3 (fr) * 2006-08-07 2008-03-20 Deepbreeze Ltd matrice de microphones pour enregistrer des bruits corporels
US9774086B2 (en) 2007-03-02 2017-09-26 Qualcomm Incorporated Wireless power apparatus and methods

Also Published As

Publication number Publication date
WO2002060215A3 (fr) 2003-04-17

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