WO2022181727A1 - 電子聴診器 - Google Patents
電子聴診器 Download PDFInfo
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- WO2022181727A1 WO2022181727A1 PCT/JP2022/007751 JP2022007751W WO2022181727A1 WO 2022181727 A1 WO2022181727 A1 WO 2022181727A1 JP 2022007751 W JP2022007751 W JP 2022007751W WO 2022181727 A1 WO2022181727 A1 WO 2022181727A1
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- body sound
- preamplifier
- inverting input
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B7/00—Instruments for auscultation
- A61B7/02—Stethoscopes
- A61B7/04—Electric stethoscopes
Definitions
- the disclosed technology relates to electronic stethoscopes.
- Japanese Patent Application Laid-Open No. 10-504748 includes a vibration transducer such as a microphone, a preamplifier that performs impedance conversion, an amplifier that performs preemphasis, an analog-to-digital converter, a digital filter, and a digital-to-analog converter.
- a digital stethoscope is described that includes a unit consisting of a power amplifier and a speaker.
- analog body sound signals output from body sound sensors equipped with piezoelectric bodies, condenser microphones, etc. for detecting body sounds such as heart sounds and breathing sounds are converted into digital signals and then filtered.
- Various signal processing such as processing and equalizing processing are performed.
- the digital body sound signal that has undergone signal processing is converted into an analog signal and output as sound in an acoustic device such as headphones and earphones.
- Conventional electronic stethoscopes require digital signal processing to compensate for the sensitivity characteristics of body sound sensors.
- piezoelectric ceramics and the like that constitute conventional body sound sensors do not have sufficient sensitivity in the frequency range of 1 KHz or less, which is the main frequency range of body sounds.
- condenser microphones, piezoelectric ceramics, and piezoelectric bodies generally have small dielectric loss, sound is hardly converted into heat, and reverberation occurs.
- ambient noise has a large effect. Therefore, the conventional electronic stethoscope requires digital signal processing to compensate for the above-described sensitivity characteristics of the body sound sensor and improve sound quality.
- the body sound signal deteriorates due to sampling and quantization when converting the body sound signal into a digital signal.
- the body sounds observed by reproducing body sound signals that have been degraded by digital conversion are far from the original body sounds and the auscultatory sounds of conventional analog stethoscopes, and could adversely affect diagnosis by auscultation. .
- the disclosed technology has been made in view of the above points, and aims to provide an electronic stethoscope that can improve the sound quality of detected body sounds and auscultatory sounds.
- An electronic stethoscope includes a body sound sensor that detects body sounds and outputs body sound signals in analog form, and an analog system that processes the body sound signals without converting them into digital signals and outputs them to the outside. and a digital system that converts body sound signals into digital signals and outputs them.
- the body sound sensor may include a polymer composite piezoelectric body in which piezoelectric particles are dispersed in a viscoelastic matrix made of a polymer material having viscoelasticity at room temperature.
- the electronic stethoscope includes a first preamplifier that amplifies body sound signals and a second preamplifier that attenuates high-frequency components contained in the body sound signals. It may be distributed to a digital system.
- the first preamplifier has an input impedance Z of 50 k ⁇ Z ⁇ 10 M ⁇
- the second preamplifier has a cutoff frequency f C of 1 kHz ⁇ f C ⁇ 3 kHz and an attenuation slope A of 12 dB/oct ⁇ A ⁇ 36 dB/oct. is preferably
- the second preamplifier may include an amplifier section and a filter section.
- the amplifier section includes a first operational amplifier having a first inverting input terminal, a first non-inverting input terminal, and a first output terminal, one end connected to the output terminal of the first preamplifier, and the other end connected to the first operational amplifier. a first resistive element connected to one inverting input terminal; and a second resistive element having one end connected to the first inverting input terminal and the other end connected to the first output terminal.
- the filter section includes a second operational amplifier having a second inverting input terminal, a second non-inverting input terminal, and a second output terminal, and a third resistor having one end connected to the second non-inverting input terminal.
- a ratio R2/R1 between the resistance value R1 of the first resistor and the resistance value R2 of the second resistor is 1 ⁇ R2/R1 ⁇ 10, and the electrostatic capacitance C1 of the first capacitor and the second capacitor
- a ratio C2/C1 to the capacitance C2 of the capacitor is preferably 3 ⁇ C2/C1 ⁇ 15.
- the second preamp includes a third operational amplifier having a third inverting input terminal, a third non-inverting input terminal, and a third output terminal, and a fifth operational amplifier having one end connected to the third inverting input terminal.
- a resistor element, a sixth resistor element having one end connected to the other end of the fifth resistor element, and a fifth resistor element having one end connected to the third output terminal and having the other end connected to the sixth resistor element a seventh resistance element connected to the connection portion with the third capacitor having one end connected to the third inverting input terminal and the other end connected to the third output terminal; and one end connected to the fifth a fourth capacitor connected to a connecting portion between the resistive element and the sixth resistive element and having the other end connected to the ground potential.
- a ratio R7/R6 between the resistance value R6 of the sixth resistance element and the resistance value R7 of the seventh resistance element is 1 ⁇ R7/R6 ⁇ 10, and the electrostatic capacitance C3 of the third capacitor and the fourth capacitor is preferably 5 ⁇ C4/C3 ⁇ 35.
- the analog system may include an analog output terminal to which the body sound signal in analog form is output and to which an acoustic device that converts the body sound signal into sound waves is connected, and the digital system converts the body sound signal into a digital signal.
- the analog system may include an analog-to-digital converter for
- the analog system may include an adjustment circuit that adjusts the amplitude of the body sound signal
- the digital system may include a communication circuit that transmits the digital signal to the outside by wire or wirelessly.
- an electronic stethoscope that can improve the sound quality of detected body sounds and auscultatory sounds.
- FIG. 1 is a circuit block diagram showing an example of a configuration of an electronic stethoscope according to an embodiment of technology disclosed herein;
- FIG. 1 is a cross-sectional view showing an example of a configuration of a body sound sensor according to an embodiment of technology disclosed herein;
- FIG. 1 is a circuit diagram of an example of a configuration of a first preamplifier according to an embodiment of technology disclosed herein;
- FIG. 4 is a circuit diagram of an example of a configuration of a second preamplifier according to an embodiment of technology disclosed herein;
- FIG. 4 is a diagram schematically showing frequency characteristics of a filter unit according to an embodiment of technology disclosed herein;
- FIG. 4 is a circuit diagram of an example of a configuration of a second preamplifier according to an embodiment of technology disclosed herein;
- FIG. 1 is a circuit block diagram showing an example of the configuration of an electronic stethoscope 10 according to an embodiment of technology disclosed herein.
- the electronic stethoscope 10 includes a body sound sensor 20 that detects body sounds and outputs body sound signals in analog format, an analog system 50 that processes the body sound signals without converting them into digital signals and outputs them to the outside, and a digital system 60 for converting body sound signals into digital signals and outputting them to the outside.
- the electronic stethoscope 10 also includes a first preamplifier 30 that amplifies body sound signals and a second preamplifier 40 that attenuates high frequency components contained in the body sound signals. The output signal is distributed to both analog chain 50 and digital chain 60 .
- the analog system 50 includes a volume control circuit 51, an automatic level control circuit 52, an output amplifier 53 and an analog output terminal 54.
- the analog output terminal 54 is connected to an acoustic device 100 such as a headphone or an earphone that converts body sound signals into sound waves.
- a digital system 60 includes a tone control circuit 61 , an analog/digital converter 62 and a communication circuit 63 .
- the body sound sensor 20 detects body sounds such as heart sounds and breathing sounds of the subject and outputs body sound signals, which are analog electric signals.
- FIG. 2 is a cross-sectional view showing an example of the configuration of the body sound sensor 20.
- the body sound sensor 20 includes a piezoelectric film 21 that converts vibrations into electrical signals and a protective layer 27 .
- the layered body composed of the piezoelectric film 21 and the protective layer 27 is in contact with the skin of the subject 200 .
- a laminate composed of the piezoelectric film 21 and the protective layer 27 has flexibility and can be brought into close contact with the skin of the subject 200 . As a result, the detection sensitivity of body sounds can be enhanced.
- the piezoelectric film 21 includes a piezoelectric layer 22 , a first electrode 25 and a second electrode 26 .
- the piezoelectric layer 22 is sandwiched between a first electrode 25 and a second electrode 26 .
- the piezoelectric layer 22 expands and contracts in the in-plane direction due to body sounds emitted from the subject 200 . This creates a voltage between the first electrode 25 and the second electrode 26 .
- the piezoelectric layer 22 is composed of a polymeric composite piezoelectric body in which piezoelectric particles 24 are dispersed in a viscoelastic matrix 23 made of a polymeric material having viscoelasticity at room temperature.
- the piezoelectric particles 24 may be uniformly dispersed in the viscoelastic matrix 23 with regularity, or may be dispersed irregularly.
- viscoelastic matrix 23 examples include polymers such as cyanoethylated polyvinyl alcohol (cyanoethylated PVA), polyvinyl acetate, polyvinylidene chloride core acrylonitrile, polystyrene-vinylpolyisoprene block copolymer, polyvinyl methyl ketone, and polybutyl methacrylate. It is possible to use materials suitably.
- polymers such as cyanoethylated polyvinyl alcohol (cyanoethylated PVA), polyvinyl acetate, polyvinylidene chloride core acrylonitrile, polystyrene-vinylpolyisoprene block copolymer, polyvinyl methyl ketone, and polybutyl methacrylate. It is possible to use materials suitably.
- the piezoelectric particles 24 may be, for example, ceramic particles having a perovskite crystal structure.
- the thickness of the first electrode 25 and the second electrode 26 is not particularly limited, it is preferably thinner in order to ensure the flexibility of the piezoelectric film 21. For example, 1 ⁇ m or less is preferable.
- the thickness of the first electrode 25 and the thickness of the second electrode 26 may be the same or different.
- the protective layer 27 has the function of protecting the piezoelectric film 21 .
- the protective layer 27 also functions as a buffer layer that reduces the difference in acoustic impedance between the piezoelectric film 21 and the subject 200 . That is, the protective layer 27 has an acoustic impedance intermediate between the acoustic impedance of the piezoelectric film 21 and the acoustic impedance of the subject 200 . This makes it possible to detect body sounds with high sound quality.
- Suitable materials for the protective layer 27 include, for example, elastomer materials, silicone resins, silicone rubbers, urethane rubbers, natural rubbers, styrene-butadiene rubbers, chloroprene rubbers, acrylonitrile rubbers, butyl rubbers, ethylene-propylene rubbers, fluorine rubbers, and chlorosulfonated polyethylene rubbers.
- elastomer materials silicone resins, silicone rubbers, urethane rubbers, natural rubbers, styrene-butadiene rubbers, chloroprene rubbers, acrylonitrile rubbers, butyl rubbers, ethylene-propylene rubbers, fluorine rubbers, and chlorosulfonated polyethylene rubbers.
- the body sound sensor 20 includes a polymer composite piezoelectric body in which piezoelectric particles are dispersed in a viscoelastic matrix made of a polymer material having viscoelasticity at room temperature. , has flexibility, so that it can be brought into close contact with the skin of the subject 200 .
- the detection sensitivity in the body sound frequency range (for example, 1 KHz or less) is higher than that of a device including non-flexible piezoelectric ceramics.
- the dielectric loss can be increased by about 5 to 10 times as compared with the sensor including piezoelectric ceramics.
- body sounds can be detected with higher sound quality than those configured including piezoelectric ceramics, so digital signal processing is unnecessary for improving sound quality. becomes. That is, even if the body sound signal output from the body sound sensor 20 is reproduced by performing only analog signal processing, it is possible to obtain a body sound with high sound quality.
- a body sound signal output from the body sound sensor 20 is supplied to the first preamplifier.
- FIG. 3 is a circuit diagram of an example of the configuration of the first preamplifier 30.
- the first preamplifier 30 has a function of amplifying body sound signals output from the body sound sensor 20 .
- the first preamplifier 30 includes transistors 301 and 305 , resistor elements 302 , 303 , 306 and 307 and capacitors 304 , 308 and 309 .
- the transistor 301 is a MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) having a source connected to a power supply potential, a drain connected to one end of the resistance element 303, and a gate connected to one end of the resistance element 302. The other end of the resistance element 303 and the drain of the transistor 301 are each connected to the ground potential.
- a so-called source follower circuit is configured by the transistor 301 and the resistance elements 302 and 303 .
- the gate of the transistor 301 is an input terminal to which the body sound signal from the body sound sensor 20 is input, that is, the input terminal of the first preamplifier 30 .
- the input impedance at this input terminal is preferably high. This is because if the input impedance becomes excessively low, the electric charge is dissipated and the amplitude of the body sound signal becomes small. If the signal is amplified to compensate for this, the noise component is also amplified, resulting in a decrease in the SN ratio. be.
- the input impedance Z of the first preamplifier 30 is preferably 50 k ⁇ Z ⁇ 10 M ⁇ .
- the input impedance of the first preamplifier 30 is determined by the input impedance of the transistor 301 and the resistance value of the resistance element 302 . Therefore, transistor 301 is preferably a MOSFET with high input impedance.
- a body sound signal impedance-converted by a source follower circuit including a transistor 301 and resistor elements 302 and 303 is amplified by an amplifier circuit including a transistor 305, resistor elements 306 and 307, and capacitors 304 and 308.
- the transistor 305 is a bipolar NPN transistor, and has a collector connected to a power supply potential via a CR parallel circuit in which a resistance element 307 and a capacitor 308 are connected in parallel, and a base connected to the drain of the transistor 301 via a capacitor 304 . and the emitter is connected to ground potential.
- the resistance element 306 has one end connected to the collector of the transistor 305 and the other end connected to the base of the transistor 305 .
- the capacitor 309 has one end connected to the collector of the transistor 305 and the other end serving as the output end of the first preamplifier 30 .
- Capacitors 304 and 309 function as coupling capacitors that block DC components.
- FIG. 4 is a circuit diagram of an example of the configuration of the second preamplifier 40.
- the second preamplifier 40 has a function of further amplifying the body sound signal supplied from the first preamplifier 30 and attenuating high frequency components contained in the body sound signal.
- the second preamplifier 40 includes an amplifier section 41 that has a signal amplification function and a filter section 42 that has a function of attenuating high frequency components.
- the amplifier section 41 includes an operational amplifier 402 and resistance elements 403, 404, and 405.
- the resistance element 403 has one end connected to the reference voltage Vref and the other end connected to the non-inverting input terminal of the operational amplifier 402 .
- the resistive element 404 has one end connected to the output end of the first preamplifier 30 and the other end connected to the inverting input terminal of the operational amplifier 402 .
- the resistive element 405 has one end connected to the inverting input terminal of the operational amplifier 402 and the other end connected to the output terminal of the operational amplifier 402 .
- the operational amplifier 402 and resistor elements 403, 404 and 405 constitute a so-called inverting amplifier circuit. Note that the operational amplifier 402 is an example of a first operational amplifier in technology disclosed herein.
- the resistance element 404 is an example of a first resistance element in technology disclosed herein.
- the resistance element 405 is an example of a second resistance element in technology disclosed herein.
- the amplification factor of the amplification section 41 is appropriately set according to the amplification factor of the first preamplifier 30 .
- the amplification factor of the amplifying section 41 corresponds to the ratio R2/R1 of the resistance value R1 of the resistance element 404 and the resistance value R2 of the resistance element 405 .
- the ratio R2/R1 is preferably 1 ⁇ R2/R1 ⁇ 10.
- the body sound signal amplified by the amplification section 41 is supplied to the filter section 42 .
- the filter section 42 includes an operational amplifier 406 , resistance elements 407 , 408 and 409 and capacitors 410 , 411 , 412 and 413 .
- One end of the resistance element 407 is connected to the non-inverting input terminal of the operational amplifier 406 .
- One end of the resistance element 408 is connected to the other end of the resistance element 407 .
- the resistance element 409 has one end connected to the other end of the resistance element 408 and the other end connected to the output terminal of the operational amplifier 402 .
- Capacitor 410 has one end connected to the non-inverting input terminal of operational amplifier 406 and the other end connected to the ground potential.
- the capacitor 411 has one end connected to the connecting portion between the resistance elements 407 and 408 and the other end connected to the inverting input terminal and the output terminal of the operational amplifier 406 .
- One end of the capacitor 412 is connected to the connecting portion between the resistance element 408 and the resistance element 409 .
- the capacitor 413 has one end connected to the output terminal of the operational amplifier 406 and the other end connected to the output terminal of the second preamplifier 40 .
- the operational amplifier 406, resistor elements 407 and 408, and capacitors 410 and 411 constitute a secondary voltage-controlled voltage source type (VCVS type) active low-pass filter.
- the resistive element 409 and capacitor 412 form a first-order passive low-pass filter.
- the operational amplifier 406 is an example of a second operational amplifier in technology disclosed herein.
- the resistance element 407 is an example of a third resistance element in technology disclosed herein.
- the resistance element 408 is an example of a fourth resistance element in technology disclosed herein.
- Capacitor 410 is an example of a first capacitor in technology disclosed herein.
- Capacitor 411 is an example of a second capacitor in technology disclosed herein.
- FIG. 5 is a diagram schematically showing frequency characteristics of the filter section 42.
- the horizontal axis represents the frequency of the signal input to the filter section 42 and the vertical axis represents the gain in the filter section 42 .
- the filter section 42 attenuates high frequency components of the input signal.
- the cutoff frequency f C in the filter section 42 is preferably 1 kHz ⁇ f C ⁇ 3 kHz. As a result, components other than the body sound contained in the body sound signal can be removed.
- the frequency characteristic of the filter section 42 it is ideal that the gain changes rapidly around the cutoff frequency fC . That is, it is preferable that the angle of the shoulder portion of the frequency characteristic be 90° and that the attenuation slope A be large.
- the attenuation slope A of the filter unit 42 is preferably 12 dB/oct ⁇ A ⁇ 36 dB/oct.
- the attenuation slope A of the filter section 42 can be controlled by the order of the low-pass filter.
- the filter section 42 is composed of a first-order low-pass filter composed of a resistance element 409 and a capacitor 412, and a second-order low-pass filter composed of an operational amplifier 406, resistance elements 407 and 408, and capacitors 410 and 411.
- a tertiary low-pass filter is configured by using a multi-stage configuration of the filter. According to this configuration, the attenuation slope A is 18 dB/oct.
- the filter unit 42 may be composed only of a secondary low-pass filter. According to this configuration, the attenuation slope A is 12 dB/oct. Further, a fifth-order low-pass filter may be configured by configuring the filter unit 42 into a multi-stage configuration including one first-order low-pass filter and two second-order low-pass filters. According to this configuration, the attenuation gradient A is 30 dB/oct. Further, the filter unit 42 may be configured to have a multi-stage configuration of two stages of primary low-pass filters and two stages of secondary low-pass filters, thereby configuring a sixth-order low-pass filter. According to this configuration, the attenuation slope A is 36 dB/oct.
- the angle of the shoulder portion of the frequency characteristic of the filter section 42 can be brought close to 90° by increasing the ratio C2/C1 between the capacitance C1 of the capacitor 410 and the capacitance C2 of the capacitor 411.
- the ratio C2/C1 is preferably 3 ⁇ C2/C1 ⁇ 15, more preferably 3 ⁇ C2/C1 ⁇ 10.
- the body sound signal output from the body sound sensor 20 is subjected to preprocessing including amplification and filtering in the first preamplifier 30 and the second preamplifier 40 .
- the preprocessed body sound signal, that is, the output signal of the second preamplifier 40 is distributed to both the analog system 50 and the digital system 60 .
- the volume adjustment circuit 51 has a function of adjusting the amplitude of the body sound signal based on the user's operation on the volume adjustment input section (not shown) of the electronic stethoscope 10 . That is, the volume adjustment circuit 51 adjusts the volume of body sounds emitted from the acoustic device 100 .
- the volume adjustment circuit 51 is configured by an analog circuit that processes the body sound signal as an analog signal. Note that the volume adjustment circuit 51 is an example of an adjustment circuit in technology disclosed herein.
- the automatic level control circuit 52 has a function of suppressing the amplitude of the body sound signal when the amplitude of the body sound signal exceeds a certain level. As a result, it is possible to prevent an excessively loud sound that is suddenly generated from being reproduced.
- the automatic level control circuit 52 is composed of an analog circuit that processes the body sound signal as it is, and includes, for example, a transistor whose gate receives the output signal of the amplification section 41 of the second preamplifier 40. may
- the output amplifier 53 amplifies the body sound signal to power suitable for outputting as sound.
- the output amplifier 53 is composed of an analog circuit that processes the body sound signal as an analog signal.
- An output signal from the output amplifier 53 is supplied to the acoustic device 100 connected to the analog output terminal 54 .
- the acoustic device 100 is a device such as headphones and earphones that converts body sound signals into sound waves. Body sounds detected by the electronic stethoscope 10 are observed by the user through the acoustic device 100 .
- the tone control circuit 61 has a function of controlling the balance between the high frequency components and the low frequency components of the body sound signal based on the user's operation of the tone adjustment input section (not shown) of the electronic stethoscope 10 .
- the analog/digital converter 62 converts the analog body sound signal into a digital signal and outputs it.
- the communication circuit 63 transmits the digital body sound signal to an external device by at least one of wired communication and wireless communication.
- the wireless communication method may be, for example, Bluetooth (registered trademark).
- the communication circuit 63 may have a communication port for transmitting the body sound signal in digital format by wired communication.
- the communication port may be, for example, a USB (Universal Serial Bus) port.
- the body sound signal in digital format transmitted from the communication circuit 63 can be reproduced as sound or an image (signal waveform) in an external device.
- the electronic stethoscope 10 includes the analog system 50 that processes the body sound signal output from the body sound sensor 20 without converting it into a digital signal and outputs the digital signal to the outside, and a digital system 60 that converts body sound signals into digital signals and outputs them.
- the body sound sensor 20 includes a polymer composite piezoelectric body in which piezoelectric particles are dispersed in a viscoelastic matrix made of a polymer material having viscoelasticity at room temperature.
- body sounds can be detected with higher sound quality than those configured including piezoelectric ceramics, so digital signal processing is unnecessary for improving sound quality. becomes.
- the analog system 50 processes body sound signals as they are without converting them into digital signals, and supplies them to the acoustic device 100 . Therefore, deterioration of body sound signals due to sampling and quantization is avoided, and natural body sounds can be reproduced in the acoustic device 100 without discomfort. That is, the electronic stethoscope 10 according to the present embodiment can improve the sound quality of detected body sounds and auscultatory sounds. Further, since the electronic stethoscope 10 includes not only the analog system 50 but also the digital system 60, various processes such as storage, transfer, visualization, processing, and analysis of body sound signals are facilitated.
- preprocessing including amplification processing and filtering processing performed on the body sound signal output from the body sound sensor 20 is performed by the first preamplifier 30 and the second preamplifier. performed by the preamplifier 40;
- a preamplifier that performs preprocessing of body sound signals is required to receive body sound signals with high input impedance in order to increase the SN ratio. , is not easy to implement with a single amplifier circuit.
- the first preamplifier 30 has a function of receiving body sound signals with high input impedance
- the second preamplifier 40 has a function of filtering
- the first preamplifier 30 and the second preamplifier 40 have a function of filtering.
- 2 preamplifiers 40 serve the signal amplification function. This enables desired signal processing while ensuring high input impedance.
- FIG. 6 is a circuit diagram showing an example of the configuration of the second preamplifier 40 according to the second embodiment of the disclosed technology.
- the second preamplifier 40 according to this embodiment includes an operational amplifier 421 , resistance elements 422 , 423 , 424 and 425 and capacitors 426 , 427 and 428 .
- the resistance element 422 is connected to the inverting input terminal of the operational amplifier 421 .
- the resistance element 423 has one end connected to the other end of the resistance element 422 and the other end connected to the output terminal of the first preamplifier 30 .
- the resistance element 424 has one end connected to the output terminal of the operational amplifier 421 and the other end connected to the connecting portion between the resistance elements 422 and 423 .
- the resistance element 425 has one end connected to the output terminal of the operational amplifier 421 and the other end serving as the output terminal of the second preamplifier 40 .
- the capacitor 426 has one end connected to the inverting input terminal of the operational amplifier 421 and the other end connected to the output terminal of the operational amplifier 421 .
- the capacitor 427 has one end connected to the connecting portion between the resistance elements 422 and 423 and the other end connected to the ground potential.
- the capacitor 428 has one end connected to the other end of the resistance element 425 and the other end connected to the ground potential.
- a non-inverting input terminal of the operational amplifier 421 is connected to the reference voltage Vref.
- the operational amplifier 421, resistance elements 422, 423, 424, and capacitors 426, 427 constitute a secondary multiple feedback active low-pass filter.
- the resistive element 425 and capacitor 428 form a first-order passive low-pass filter.
- the operational amplifier 421 is an example of a third operational amplifier in technology disclosed herein.
- the resistance element 422 is an example of a fifth resistance element in technology disclosed herein.
- the resistance element 423 is an example of a sixth resistance element in technology disclosed herein.
- the resistance element 424 is an example of a seventh resistance element in technology disclosed herein.
- Capacitor 426 is an example of a third capacitor in technology disclosed herein.
- Capacitor 427 is an example of a fourth capacitor in technology disclosed herein.
- the amplification factor of the second preamplifier 40 according to the present embodiment corresponds to the ratio R7/R6 between the resistance value R6 of the resistance element 423 and the resistance value R7 of the resistance element 424.
- the ratio R7/R6 is preferably 1 ⁇ R7/R6 ⁇ 10.
- the angle of the shoulder portion of the frequency characteristic of the second preamplifier 40 according to the present embodiment is set to 90° by increasing the ratio C4/C3 between the capacitance C3 of the capacitor 426 and the capacitance C4 of the capacitor 427. can get closer.
- the ratio C4/C3 is preferably 5 ⁇ C4/C3 ⁇ 35, more preferably 20 ⁇ C4/C3 ⁇ 30.
- the second preamplifier 40 according to the present embodiment can exhibit the same function as the second preamplifier 40 (see FIG. 4) according to the first embodiment.
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Abstract
Description
図1は、開示の技術の実施形態に係る電子聴診器10の構成の一例を示す回路ブロック図である。電子聴診器10は、生体音を検出してアナログ形式の生体音信号を出力する生体音センサ20と、生体音信号をデジタル信号に変換することなく処理して外部に出力するアナログ系統50と、生体音信号をデジタル信号に変換して外部に出力するデジタル系統60と、を備えている。また、電子聴診器10は、生体音信号を増幅する第1のプリアンプ30と、生体音信号に含まれる高周波成分を減衰させる第2のプリアンプ40と、を備えており、第2のプリアンプ40の出力信号が、アナログ系統50及びデジタル系統60の双方に分配される。
図6は、開示の技術の第2の実施形態に係る第2のプリアンプ40の構成の一例を示す回路図である。本実施形態に係る第2のプリアンプ40は、演算増幅器421、抵抗素子422、423、424、425及びキャパシタ426、427、428を含んで構成されている。
Claims (10)
- 生体音を検出してアナログ形式の生体音信号を出力する生体音センサと、
前記生体音信号をデジタル信号に変換することなく処理して外部に出力するアナログ系統と、
前記生体音信号をデジタル信号に変換して出力するデジタル系統と、
を含む電子聴診器。 - 前記生体音センサは、常温で粘弾性を有する高分子材料からなる粘弾性マトリックス中に圧電体粒子を分散してなる高分子複合圧電体を含んで構成されている
請求項1に記載の電子聴診器。 - 前記生体音信号を増幅させる第1のプリアンプと、
前記生体音信号に含まれる高周波成分を減衰させる第2のプリアンプと、を含み、
前記第2のプリアンプの出力信号が、前記アナログ系統と、前記デジタル系統とに分配される
請求項1又は請求項2に記載の電子聴診器。 - 前記第1のプリアンプは、入力インピーダンスZが50kΩ≦Z≦10MΩであり、
前記第2のプリアンプは、カットオフ周波数fCが1kHz≦fC≦3kHz且つ減衰傾度Aが12dB/oct≦A≦36dB/octである
請求項3に記載の電子聴診器。 - 前記第2のプリアンプは、増幅部と、フィルタ部とを含み、
前記増幅部は、
第1の反転入力端子、第1の非反転入力端子及び第1の出力端子を有する第1の演算増幅器と、
一端が前記第1のプリアンプの出力端に接続され、他端が前記第1の反転入力端子に接続された第1の抵抗素子と、
一端が前記第1の反転入力端子に接続され、他端が前記第1の出力端子に接続された第2の抵抗素子と、を含み、
前記フィルタ部は、
第2の反転入力端子、第2の非反転入力端子及び第2の出力端子を有する第2の演算増幅器と、
一端が前記第2の非反転入力端子に接続された第3の抵抗素子と、
一端が前記非反転入力端子に接続され、他端が接地電位に接続された第1のキャパシタと、
一端が前記第3の抵抗素子の他端に接続された第4の抵抗素子と、
一端が前記第3の抵抗素子と前記第4の抵抗素子との接続部に接続され、他端が前記第2の反転入力端子及び前記第2の出力端子に接続された第2のキャパシタと、
を含む請求項3又は請求項4に記載の電子聴診器。 - 前記第1の抵抗素子の抵抗値R1と前記第2の抵抗素子の抵抗値R2との比R2/R1が1≦R2/R1≦10であり、
前記第1のキャパシタの静電容量C1と、前記第2のキャパシタの静電容量C2との比C2/C1が、3≦C2/C1≦15である
請求項5に記載の電子聴診器。 - 前記第2のプリアンプは、
第3の反転入力端子、第3の非反転入力端子及び第3の出力端子を有する第3の演算増幅器と、
一端が前記第3の反転入力端子に接続された第5の抵抗素子と、
一端が前記第5の抵抗素子の他端に接続された第6の抵抗素子と、
一端が前記第3の出力端子に接続され、他端が前記第5の抵抗素子と前記第6の抵抗素子との接続部に接続された第7の抵抗素子と、
一端が前記第3の反転入力端子に接続され、他端が前記第3の出力端子に接続された第3のキャパシタと、
一端が前記第5の抵抗素子と前記第6の抵抗素子との接続部に接続され、他端が接地電位に接続された第4のキャパシタと、
を含む請求項3又は請求項4に記載の電子聴診器。 - 前記第6の抵抗素子の抵抗値R6と前記第7の抵抗素子の抵抗値R7との比R7/R6が1≦R7/R6≦10であり、
前記第3のキャパシタの静電容量C3と前記第4のキャパシタの静電容量C4との比C4/C3が、5≦C4/C3≦35である
請求項7に記載の電子聴診器。 - 前記アナログ系統は、アナログ形式の前記生体音信号が出力され且つ前記生体音信号を音波に変換する音響デバイスが接続されるアナログ出力端子を含み、
前記デジタル系統は、前記生体音信号をデジタル信号に変換するアナログ・デジタル変換器を含む
請求項1から請求項8のいずれか1項に記載の電子聴診器。 - 前記アナログ系統は、前記生体音信号の振幅を調整する調整回路を含み、
前記デジタル系統は、前記デジタル信号を有線又は無線により外部に送信する通信回路を含む
請求項9に記載の電子聴診器。
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JP2023502508A JPWO2022181727A1 (ja) | 2021-02-26 | 2022-02-24 | |
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- 2022-02-24 CN CN202280016049.9A patent/CN116867438A/zh not_active Withdrawn
- 2022-02-24 JP JP2023502508A patent/JPWO2022181727A1/ja not_active Abandoned
- 2022-02-24 WO PCT/JP2022/007751 patent/WO2022181727A1/ja active Application Filing
- 2022-02-24 EP EP22759762.2A patent/EP4299009A1/en not_active Withdrawn
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