JP2012194114A - Chemical sensibility sensor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To convert the frequency of sensor signals to a frequency band where the influence of noise decreases, and further to perform bandwidth-limited ΔΣ modulation to reduce the influence of leaking noise from electric light wires thereby to enhance the S/N ratio.SOLUTION: A sensor device comprises a signal processing circuit that processes electric signals from each sensor, a radio circuit that subjects output signals from the signal processing circuit to radio modulation and outputs the modulated signals, and a power supply circuit that receives electromagnetic waves from outside to generate and supply electric power. The signal processing circuit further comprises a circuit that subjects baseband signals, which are electric signals from the sensors, to frequency conversion, and a bandwidth-limited ΔΣ modulator circuit that subjects the frequency-converted signals to A/D conversion. The radio circuit subjects digital signals resulting from the A/D conversion and clock signals used by the bandwidth-limited ΔΣ modulator circuit to quadrature modulation, and transmits the modulated signals as radio signals via an antenna.

Description

  The present invention relates to a chemosensory sensor device that processes an electrical signal from a sensor that generates a potential in response to ions and chemical substances such as salty taste, sweet taste, bitter taste, sour taste, and umami taste, and transmits the potential wirelessly.

  A chemosensory sensor such as a taste sensor that measures a taste that is one of the five human senses is known as a known technique. “Chemical sensory ability” means a function that can accept the properties of a chemical substance dissolved or mixed in an aqueous solution. For example, a function capable of sensing an aqueous solution in which a water-soluble chemical substance is dissolved as a taste, that is, a salty taste, sweet taste, bitter taste, sour taste, umami taste, a function of measuring the hydrogen ion concentration of the aqueous solution, and the like are applicable. The chemosensory sensor is a membrane potential measurement type sensor developed by applying ion selective electrode technology. In other words, the chemosensory sensor uses various types of lipid polymer membranes that mimic biological membranes of living organisms as the working electrode, so that various membranes can be used for the basic tastes of salty taste, sweet taste, bitter taste, sour taste, and umami taste. A potential can be generated.

  A chemosensory sensor such as a taste sensor is a known technology, but a conventional taste sensor is a large-sized device and has a desktop size. For this reason, the sensor portion as shown in Patent Document 1 is first miniaturized, and the measuring device itself is also downsized to the extent shown in Non-Patent Document 1. However, it was still about the size of a lunch box and was not portable.

  In addition, the electrical signal from the taste sensor unit is a signal whose main component is a low frequency component and whose frequency band is several hundred Hz or less. When such a low frequency electric signal is processed by a CMOS integrated circuit, flicker noise (1 / f noise) of the MOS transistor becomes a problem particularly in a front-end amplifier that amplifies the signal from the taste sensor unit. It is known that in a MOS transistor, 1 / f noise that is inversely proportional to frequency is dominant. 1 / f noise is generated when carriers are trapped irregularly at the energy level at the boundary between the gate oxide film and the silicon substrate.

FIG. 8A shows the configuration of a signal processing circuit that reduces flicker noise based on the prior art, and FIG. 8B shows a signal and amplifier noise components. FIG. 9 is a spectrum diagram for explaining the operation. An input signal Vin having a signal component as illustrated in FIG. 8B is input from the sensor to the first frequency conversion circuit (mixer). The local oscillation (local oscillation) signal _VLC is input to another input of the first frequency conversion circuit (mixer). When a local oscillation (local oscillation) signal having a frequency f _C is applied to the first frequency conversion circuit (mixer), the sensor signal (baseband signal) is frequency converted into a frequency region that is an integral multiple of f _C (FIG. 9). (See (1)). As a result, the output signal V _A is up-converted to a high frequency region that is not affected by flicker noise.

The output signal V _A of the first frequency conversion circuit is applied to the input of the amplifier, and a noise signal V _U having an amplifier noise component as illustrated in FIG. 8B is added to the amplifier. It is shown as a thing. Both signals are amplified by an amplifier, but the frequency bands of both signals are different as shown in (2) of FIG.

The output signal V _B amplified by the amplifier is frequency converted again by a second frequency conversion circuit (mixer) whose local oscillation (local oscillation) signal is f _C. As a result, the sensor signal is down-converted to a baseband signal, while the noise signal V _U is up-converted to a frequency region that is an integral multiple of f _C ((3) in FIG. 9). reference). After returning to the signal V _C having the original frequency component, the sensor signal is converted into a digital signal by the analog / digital conversion circuit ADC. Then, it modulates with a radio | wireless circuit and transmits as a radio signal.

  In this way, the conventional technique passes through the frequency conversion circuit (mixer) twice, increasing the circuit scale, and also generating noise in the frequency conversion circuit (mixer), increasing the influence of the noise.

JP 2007-057459

S. Etoh et al., “Fabrication of Taste Sensor Chip and Portable Taste Sensor System” TA6, 2006 International Conference on Microtechnologies in Medicine and Biology, May 2006. S. Etoh et al., “Taste Sensor Chip for Portable Taste Sensor System” Sensors and Materials, Vol.20, No.4, pp.151-160, 2008.

  Therefore, the present invention forms a chemosensory sensor and a signal processing circuit for processing an electric signal from the sensor on a single semiconductor substrate in order to reduce the size, and receives power from external electromagnetic waves. It has a circuit to generate and operates wirelessly. However, when transmitting information wirelessly, it is necessary to reduce transmission power in order to reduce power consumption, which places a burden on signal processing such as data extraction on the reception side. Chemosensory sensors have very high output impedance and are vulnerable to leakage noise from the power line. In addition, since the sensory sensor has a main signal component at a low frequency, the influence of 1 / f noise (flicker noise) of the CMOS circuit is large, and the signal-to-noise ratio (S / N) can be ensured. It becomes a problem. For this reason, there is a problem that the reliability of data transmission is reduced or the power consumption is increased.

  Therefore, in order to reduce the influence of 1 / f noise (flicker noise) of the CMOS circuit, the present invention converts the frequency of the baseband signal to a frequency band where the influence of 1 / f noise is reduced, and further leaks from the power line. The purpose is to improve the S / N by performing band-limited ΔΣ modulation to reduce the influence of noise.

  The chemosensory sensor device of the present invention includes a plurality of sensors that generate an electric potential in response to ions or chemical substances, a signal processing circuit that processes an electric signal from each sensor, and an output signal from the signal processing circuit. And a power supply circuit that generates power by receiving electromagnetic waves from the outside and supplies the power to each circuit in the apparatus. The signal processing circuit includes a circuit that converts the frequency of a baseband signal that is an electrical signal from the sensor, and a band-limited ΔΣ modulation circuit that A / D converts the frequency-converted signal. The radio circuit orthogonally modulates the A / D converted digital signal and the clock signal used in the band-limited ΔΣ modulation circuit, and transmits the result as a radio signal via the antenna.

  A multiplexer that switches the output of each sensor and selects one signal may be provided. The output signal of this multiplexer is input to the frequency conversion circuit. Alternatively, a signal processing circuit and a radio circuit may be individually provided for each of the plurality of sensors. Alternatively, a signal processing circuit is provided corresponding to each of the plurality of sensors, and a multiplexer for switching signals of the signal processing circuit is provided, so that signals from the plurality of signal processing circuits are switched and output to the radio circuit. It may be configured. The band-limited ΔΣ modulation circuit is a bandpass filter type ΔΣ modulation circuit or a high-pass filter type ΔΣ modulation circuit.

  According to the present invention, it is possible to provide a low-power wireless small-sized chemosensory sensor device with improved data transmission reliability. The present invention reduces the influence of 1 / f noise (flicker noise) of a CMOS circuit by frequency-converting a baseband signal to a frequency band where the influence of 1 / f noise is reduced and further performing band-limited ΔΣ modulation. In addition, the S / N can be improved by reducing the influence of leakage noise from the power line. Clock and data extraction (CDR; Clock Data Recovery) can be facilitated on the receiving side by orthogonally modulating the obtained signal with the clock signal.

It is a schematic circuit diagram of the 1st example of the chemosensory sensor apparatus comprised based on this invention. It is a schematic circuit diagram of the 2nd example of the chemosensory sensor apparatus comprised based on this invention. It is a schematic circuit diagram of the 3rd example of the chemosensory sensor apparatus comprised based on this invention. (A) is a figure which shows the more concrete circuit structural example of the amplifier part in FIG.1 and FIG.2, a signal processing circuit, and a radio | wireless circuit, (B) is a figure which shows a signal and an amplifier noise component. FIG. 6 is a spectrum diagram for explaining an operation when a bandpass filter type (BPF) is used as a band-limited ΔΣ modulator. It is a spectrum figure for demonstrating operation | movement at the time of using a high-pass filter type (HPF). It is a figure for demonstrating operation | movement of the orthogonal modulation circuit in a radio | wireless circuit. (A) shows the configuration of a signal processing circuit in which flicker noise is reduced based on the prior art, and (B) is a diagram showing signals and amplifier noise components. It is a spectrum figure for demonstrating operation | movement of a signal processing circuit.

  Hereinafter, the present invention will be described based on examples. FIG. 1 is a schematic circuit diagram of a first example of a chemosensory sensor device constructed according to the present invention. The illustrated sensor device generates one or more potentials (here, three) with reference electrodes (reference electrodes, not shown) in response to ions or chemical substances such as salty taste, sweet taste, bitter taste, sour taste, and umami taste. Sensor (working electrodes) A to C, a multiplexer, an analog front-end circuit including an amplifier unit and a signal processing circuit, a radio circuit, an antenna, and a power supply circuit. The power supply circuit rectifies the current from the antenna and supplies necessary power to each circuit in the apparatus.

  Each sensor AC generates a potential in response to salty taste, sweet taste, bitter taste, sour taste, and umami taste, respectively. As these sensors A to C, for example, those disclosed in Patent Document 1 can be used. The reference electrode (reference electrode) is obtained by solidifying the internal liquid of a conventional liquid membrane type reference electrode, and the sensors A, B, and C are various types of lipid polymer membranes imitating biological biological membranes. Is a working electrode.

  The multiplexer is a circuit that selects one signal by switching the outputs of the sensors A to C. A timer circuit (not shown) is preferably used for switching the multiplexer, but switching may be performed using an external signal, for example. As described above, since the output timing from each of the sensors A to C can be shifted by using the multiplexer, the output from each of the sensors A to C is compared with the case where the outputs from the sensors A to C are simultaneously performed (see FIG. 2). It is possible to reduce the amount of power required for this.

  The analog front end circuit includes an amplifier unit and a signal processing circuit. As will be described in detail later, the amplifier unit frequency-converts the electrical signal (baseband signal) that has passed through the multiplexer to a frequency band where the influence of 1 / f noise is reduced, and then amplifies it using the amplifier. This amplified signal is A / D converted by a signal processing circuit using a band-limited ΔΣ modulator. The output is wirelessly transmitted via a wireless circuit and an antenna.

  The radio circuit is a circuit that orthogonally modulates the digital signal that has been A / D converted by the signal processing circuit to generate a radio signal (radio frequency). When a timer circuit is used for switching the multiplexer described above, it is preferable to wirelessly output the timer circuit switching signal to the outside through this wireless circuit. You can also

  The output of the radio circuit is output to the outside via the antenna. The antenna receives external radio waves and supplies them to the power supply circuit. While the radio wave is not received, the circuit is stopped (sleep state), and the radio wave having sufficient energy necessary for starting the circuit (only the carrier signal or modulated) is applied. The power supply circuit rectifies the current (electromagnetic wave) from the antenna and supplies necessary power to the circuits (multiplexer, analog front-end circuit, wireless circuit) in the apparatus. As a result, a necessary amount of power can be covered by the power supply circuit without incorporating an operating battery on the substrate.

  Each circuit excluding the sensors A to C as described above, that is, a multiplexer, an analog front-end circuit, a radio circuit, an antenna, and a power supply circuit are assembled on one substrate (for example, a semiconductor substrate) and covered with resin. It is sealed against the outside air. On the other hand, in each sensor A to C, adjacent adjacent sensors are partitioned by resin, and the surface of each sensor A to C is exposed and arranged on the substrate.

  By comprising as mentioned above, even if a chemical sensory sensor device is immersed in the aqueous solution which is a measuring object, only the surface of each sensor AC contacts the aqueous solution, and saltiness, sweetness, bitterness which are basic tastes Various membrane potentials can be generated for sourness and umami.

  Next, a method for measuring the taste of an aqueous solution to be measured using an exemplary chemosensory sensor device will be described. First, the apparatus is immersed in an aqueous solution. In addition, as a method of immersing the chemosensory sensor device in an aqueous solution, a method of attaching the chemosensory sensor device to the tip of a portable measuring device that can be carried and immersing it in an aqueous solution, or the bottom of the container There is a method in which a chemosensory sensor device is attached to the container and an aqueous solution is supplied into the container.

  In this manner, by immersing the chemosensory sensor device in an aqueous solution, membrane potentials are generated from the reference electrode (reference electrode) and the sensors A, B, and C that are working electrodes, respectively. Note that one of the membrane potentials of each of the sensors A to C is selected by switching the multiplexer, and after the signal processing is performed as described above, the radio signal modulated by the radio circuit is transmitted via an antenna, for example, Send it to a computer, memory, etc. for storage.

  FIG. 2 is a schematic circuit diagram of a second example of the chemosensory sensor device constructed according to the present invention. As described above, this apparatus includes one reference electrode (reference electrode) and at least one working electrode as another sensor. This second example includes a plurality of sensors A to C, respectively. In addition, it is different from the above-described first example in which a multiplexer is provided to perform switching processing of signals from a plurality of sensors in that individual circuits (amplifier unit, signal processing circuit, and radio circuit) are associated. is doing.

  FIG. 3 is a schematic circuit diagram of a third example of the chemosensory sensor device constructed according to the present invention. In the third example, an amplifier unit and a signal processing circuit are associated with each of the plurality of sensors A to C. However, a multiplexer is provided at the subsequent stage of the plurality of signal processing circuits so that signals from the plurality of signal processing circuits are provided. Is different from the first or second example described above in that it is configured to output the signal to the radio circuit.

  The detailed configuration and operation of each circuit in the second example or the third example are the same as those in the first example. This will be described below.

4A is a diagram illustrating a more specific circuit configuration example of the amplifier unit, the signal processing circuit, and the wireless circuit in FIGS. 1 and 2, and FIG. 4B is a diagram illustrating a signal and an amplifier noise component. is there. FIG. 5 is a spectrum diagram for explaining the operation when a bandpass filter type (BPF) is used as a band-limited ΔΣ modulator, and FIG. 6 is a diagram when a high-pass filter type (HPF) is used. It is a spectrum figure for demonstrating operation | movement. The amplifier unit includes a frequency conversion circuit and an amplifier. The input signal Vin that has passed through the multiplexer is frequency-converted using a frequency conversion circuit (mixer) and then amplified using an amplifier. The mixer constituting the frequency conversion circuit may be a passive mixer using a simple switch or an active mixer. From the sensor, an input signal Vin having a signal component as illustrated in FIG. 4B is input to a frequency conversion circuit (mixer) directly or via a buffer (not shown). A local oscillation (local oscillation) signal _VLC is input to another input of the frequency conversion circuit (mixer). As a result, the output signal V _A is up-converted to a high frequency region that is not affected by flicker noise. Here, when a local oscillation (local oscillation) signal having a frequency f _LC is applied to the frequency conversion circuit (mixer), the sensor signal (baseband signal) is frequency converted into a frequency region that is an integral multiple of f _LC (FIG. 5). (See (1)).

An output signal V _A from the frequency conversion circuit (mixer) is applied to the input of the amplifier and amplified by the amplifier. At this time, noise such as flicker noise (1 / f noise) is generated particularly from the MOS transistors constituting the amplifier. A noise signal V _U having an amplifier noise component as illustrated in FIG. 4B is illustrated as being applied to the amplifier in FIG. 4A. However, as shown in (2) of FIG. 5, in the amplifier output signal V _B , the frequency band of the sensor signal and the noise signal V _U that have been frequency-converted to a frequency region that is an integral multiple of f _LC as described above is Is different. The output signal V _{B of the} amplifier is converted from analog to digital by a signal processing circuit (ADC) at the next stage.

  In the circuit illustrated in FIG. 4, the sensor signal component is directly converted from analog to digital by the band-limited ΔΣ modulation circuit without using the second frequency conversion circuit (mixer) as described with reference to FIG. To get the digital value. At this time, by limiting the band with the band limiting ΔΣ modulation circuit, it is possible to obtain only the necessary sensor signal component not including noise (see (3) in FIG. 5). Thus, the number of frequency conversion circuits (mixers) can be reduced as compared with the prior art. Here, the band-limited ΔΣ modulator corresponds to a filter disposed after the ΔΣ modulator, but normally, the signal transfer function (STF) of the band-limited filter is changed by changing the circuit configuration of the ΔΣ modulator. ; Signal Transfer Function). In the present invention, a bandpass filter type (BPF) or a high-pass filter type (HPF) can be used as the band limiting filter. The pass band and the stop band when the band pass filter type (BPF) is used are as shown in (3) of FIG. Further, the pass band and the stop band when the high pass filter type (HPF) is used are as shown in (3) of FIG.

  Regardless of the filter type, the band-limited ΔΣ modulation circuit outputs a digital 1-bit signal string (bit stream). This bit stream is modulated by a radio circuit and transmitted as a radio signal.

FIG. 7 is a diagram for explaining the operation of the quadrature modulation circuit in the radio circuit. Since the bit stream is a data string of “1” and “0”, data delimiter information is required. However, for normal modulation, for example, amplitude modulation, frequency modulation, or phase modulation, one carrier signal is used. Only one signal can be modulated, and data break information cannot be modulated simultaneously. Therefore, in the present invention, as shown in the figure, quadrature modulation is performed using two carrier signals (sine wave (sin) and cosine wave (cos)) having a phase difference of 90 degrees. In other words, the data signal is modulated using a sine wave (sin) (or cosine wave (cos)), while the clock signal of the band-limited ΔΣ modulation circuit serving as data delimiter information is converted to a cosine wave (cos) (or sine wave (sin)). ) Can be used to simultaneously transmit two signals wirelessly. By simultaneously transmitting clock signals, there is also an advantage that a circuit for clock data recovery (CDR) on the receiving side is simplified. In addition, since the clock signal is transmitted together, it is possible to prevent the deterioration of the bit error rate (BER) even if the transmission power is reduced. In other words, low power consumption can be achieved with the same bit error rate BER.

Claims (6)

A plurality of sensors that generate potentials in response to ions and chemical substances, a signal processing circuit that processes electrical signals from each sensor, and a wireless circuit that wirelessly modulates and outputs an output signal from the signal processing circuit; In the chemosensory sensor device having a power supply circuit that receives electromagnetic waves from the outside and generates power to supply each circuit in the device,
The signal processing circuit includes a circuit that frequency-converts a baseband signal that is an electrical signal from the sensor, and a band-limited ΔΣ modulation circuit that A / D converts the frequency-converted signal,
The radio circuit is a sensory sensory sensor device comprising: orthogonally modulating the A / D converted digital signal and a clock signal used in the band-limited ΔΣ modulation circuit and transmitting the radio signal via an antenna . The chemosensory sensor device according to claim 1, further comprising a multiplexer that switches an output of each sensor to select one signal, and an output signal of the multiplexer is input to the frequency conversion circuit. The sensory sensory sensor device according to claim 1, wherein a signal processing circuit and a radio circuit are individually provided for each of the plurality of sensors. A signal processing circuit is provided corresponding to each of the plurality of sensors, and a multiplexer for switching signals of the signal processing circuit is provided, and the signals from the plurality of signal processing circuits are switched and output to the radio circuit The chemosensory sensor device according to claim 1. The chemosensory sensor device according to claim 1, wherein the band-limited ΔΣ modulation circuit is a bandpass filter type ΔΣ modulation circuit. The chemosensory sensor device according to claim 1, wherein the band-limited ΔΣ modulation circuit is a high-pass filter type ΔΣ modulation circuit.

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