JP2009212675A - Alternating current signal detector and receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect an alternating signal with high sensitivity. <P>SOLUTION: An alternating signal detector 1 includes an alternating current sensor 10 comprising a coil 11, a first electrode 12 arranged in close vicinity to the coil 11 and a second electrode 13 arranged in close vicinity to the coil 11. The first electrode 12 and the second electrode 13 are arranged at opposite sides in the axial direction of the coil 11 with the coil 11 sandwiched therebetween. An alternating current signal is applied to the first electrode 12. An inverting amplifier circuit 20 of the alternating signal detector 1 inverts and amplifies the alternating current signal by induced voltage of the coil 11 and applies the alternating signal to the second electrode 13 through a resistor 41 and a capacitor 42 with low capacitance. An alternating current component that is currently output from the inverting amplifier circuit 20 is extracted in a capacitor 31 to be an output OUT of the alternating current signal detector 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an AC signal detecting device applicable to a receiving device used for human body communication.

As an AC signal detecting device applicable to a receiving device used for human body communication, an AC signal applied to the coil, an electrode arranged on the coil, to which an AC signal is applied, and the induced voltage of the coil are used. An apparatus including a detection circuit for detection is known (Patent Document 1).
JP 2006-222596 A

  The present invention provides a sensitivity of an AC signal detection device including a coil, an electrode to which an AC signal is applied, and a detection circuit that detects the AC signal based on an induced voltage of the coil. It is an object to improve further.

  In order to achieve the above object, the present invention applies a phase adjustment to an AC signal generated by an induced voltage of a first electrode, a coil, a second electrode, and the coil to which an AC signal is applied. An AC signal detecting device having a feedback circuit, wherein the first electrode and the second electrode are arranged so as to be close to the coil on the opposite side to the coil in the axial direction of the coil. provide.

  Here, such an AC signal detection apparatus is provided with a first capacitor, and the feedback circuit includes an inverting amplifier circuit that inverts and amplifies an AC signal generated by the induced voltage of the coil, a resistor, and a first capacitor. The output of the inverting amplifier circuit is applied to the second electrode via the resistor and the first capacitor, and the output of the inverting amplifier circuit is applied to the alternating current via the second capacitor. You may comprise so that it may output as an output of a signal detection apparatus. In this case, the second capacitor may be formed by two closely-spaced conductor patterns formed on the substrate so as to be separated from each other.

  According to the AC signal detection devices as described above, the induced voltage generated in the coil is larger than that in the case where only the first electrode is provided and the second electrode is not provided as described in Patent Document 1. This is because the magnetic flux change of the magnetic flux generated from the first electrode by the AC signal and the magnetic flux change of the magnetic flux generated from the second electrode by the inverted AC signal are applied to the coil with an appropriate phase difference. This is considered to be due to an improvement in the Q value of the signal detection device.

  Such an AC signal detection device is provided with a receiving electrode that is in proximity to or in contact with a medium that induces an AC electric field, and a conductive wire that connects the first electrode and the receiving electrode, and is induced in the receiving electrode by the AC electric field. The AC signal may be applied to the first electrode via the conductive wire. In this case, the AC signal detection device transmits the AC signal via a transmission medium that is a human body or a living body. The present invention can be applied to a receiving device used in the system. That is, in this case, for example, an AC electric field driven by an AC signal is induced in the periphery of the transmission medium, and the reception electrode of the AC signal detection device is connected to the transmission medium by the transmission medium. It may be in proximity or contact.

  According to the present invention, an AC signal detection device including a coil, an electrode disposed on the coil to which an AC signal is applied, and a detection circuit that detects the AC signal based on an induced voltage of the coil. The sensitivity can be further improved.

Hereinafter, an embodiment of the present invention will be described.
In FIG. 1, the structure of the alternating current signal detection apparatus which concerns on this embodiment is shown.
As shown in the figure, the AC signal detection device 1 includes an AC sensor 10 including a coil 11, a first electrode 12 disposed close to the coil 11, and a second electrode 13 disposed close to the coil 11. It has. Here, the 1st electrode 12 and the 2nd electrode 13 are arrange | positioned so that the coil 11 may be pinched | interposed on the opposite side mutually about the axial direction of the coil 11. FIG. Then, an AC signal detected by the AC signal detection device 1 is applied to the input IN of the first electrode 12.

  The AC signal detection device 1 includes an inverting amplifier circuit 20 including an FET 21, a resistor 22, a resistor 23, and a frequency characteristic adjusting capacitor 24, and one end of the coil 11 is connected to the gate of the FET 21. The other end is grounded. The FET 21 changes the magnitude of the source-drain current of the FET 21 in accordance with the induced voltage of the coil 11 that is the gate voltage, and the resistance 22 and the resistance 23 increase or decrease the magnitude of the source-drain current of the FET 21. The voltage is converted into an inverted (phase inverted) voltage and used as the output of the inverting amplifier circuit 20. Then, the AC component of the output of the inverting amplifier circuit 20 is extracted by the capacitor 31 and becomes the output OUT of the AC signal detection device 1.

The output voltage of the inverting amplifier circuit 20 is applied to the second electrode 13 through the resistor 41 and the low-capacitance capacitor 42.
In addition, the AC signal detection apparatus 1 also includes a capacitor 51 for setting the resonance frequency of the coil 11, a coil 52 for attenuating unnecessary frequency components, and the like.
Here, the entire AC signal detection apparatus 1 can be realized using a printed circuit board or an integrated circuit. Further, the AC sensor 10 of the AC signal detection device 1 can be formed as a conductor pattern of a printed board or a semiconductor substrate.
That is, when forming the AC sensor 10 as the conductor pattern of the printed circuit board, for example, the AC sensor 10 is formed as follows.
That is, the layer structure of the printed circuit board 100 as shown in FIG. 2a is used, and the printed circuit board 100 is placed on a plate-like or film-like base material 101 as shown in FIG. The second pattern layer 104, the first insulating layer 105, and the third pattern layer 106 are stacked in this order.

  Then, as shown in FIG. 2c, the second electrode 13 is formed by the conductor pattern provided on the first pattern layer 102, and the coil 11 is formed by the conductor pattern having the spiral shape provided on the second pattern layer 104. The first electrode 12 is formed by the conductor pattern provided on the third pattern layer 106.

Here, the conductor patterns of the first electrode 12 and the second electrode 13 are formed so as to cover the pattern of the coil 11 as shown in FIG.
In the AC sensor 10, the conductor patterns of the first electrode 12 and the second electrode 13 are not necessarily formed so as to cover the entire pattern of the coil 11, but only a part of the pattern of the coil 11. You may form so that it may cover, and you may form so that the part except the center part of the pattern of the coil 11 may be covered.

In addition, although FIG. 2 demonstrated the case where the alternating current sensor 10 was formed using a printed circuit board, the alternating current sensor 10 can be similarly formed on a semiconductor substrate.
The low-capacitance capacitor 42 can also be formed by two parallel conductor patterns 421 and 422 provided in the pattern layer, as shown in FIG. 2c. That is, the capacitor 42 can be formed by, for example, two conductor patterns 421 and 422 having a length of 10 mm in parallel and a distance of 0.2 mm.

Now, according to such a configuration of the AC signal detection device 1, when an AC signal is applied from the input IN to the first electrode 12, the AC signal is generated from the first electrode 12 by the AC signal in the axial direction of the coil 11. A change occurs in the magnetic flux passing through the coil 11.
On the other hand, when a change occurs in the magnetic flux passing through the coil 11, an AC signal due to the induced voltage of the coil 11 is input to the inverting amplifier circuit 20, and the input AC signal is inverted and amplified by the inverting amplifier circuit 20 and then the resistor 41. , Feedback to the second electrode 13 via the capacitor 42.
And the change of the magnetic flux which penetrates the coil 11 to the axial direction of the coil 11 which generate | occur | produces from the 2nd electrode 13 by the alternating current signal fed back to the said 2nd electrode 13 also generate | occur | produces.

The change of the magnetic flux passing through the coil 11 is caused by the change of the magnetic flux generated from the first electrode 12 and the change of the magnetic flux generated from the second electrode 13.
Further, the AC signal inverted and amplified by the inverting amplifier circuit 20 is output as an output OUT through the capacitor 31.

Here, with such a configuration, the induced voltage generated in the coil 11 is larger than that in the case where the second electrode 13 is not provided by appropriately setting the phase of the AC signal fed back to the second electrode. Become. This is because the Q value of the AC signal detection device 1 is made to act on the coil 11 with a suitable phase difference between the magnetic flux change of the magnetic flux generated from the first electrode 12 and the magnetic flux change of the magnetic flux generated from the second electrode 13. It is estimated that it is due to improvement.
Therefore, in designing the AC signal detection device 1 in consideration of this, for example, while applying a sinusoidal AC signal from the input IN to the first electrode 12, an induced voltage generated in the coil 11, that is, an output of the AC signal detection device 1 is applied. By observing OUT, the resistance value of the resistor 41 and the capacitance of the capacitor 42 are selected and set so that the gain and Q value are most improved.

Now, such an AC signal detection device 1 can be applied to a communication system that performs communication via a human body, for example.
That is, in this case, as shown in FIG. 3 a, the communication system is configured by a transmitter 200 and a receiver 400 that perform communication via the human body 300.
Further, the transmitter 200 generates a communication information that is communication information to be transmitted to the receiver 400, a modulator 202 that modulates the communication information and outputs it as a transmission signal, and applies the transmission signal to the human body 300. A transmission electrode 203 that induces an electric field around the human body is included.
In addition, the receiver 400 includes a receiving electrode 401 placed in an electric field induced around a human body during communication, the AC signal detection device 1 described in the above embodiment, a demodulator 402, and a receiving side data processing unit 403. And including. Then, the receiving electrode 401 and the input IN of the AC sensor 10 of the AC signal detecting device 1 are connected by a conducting wire so that the AC signal induced in the receiving electrode 401 by the electric field around the human body is guided to the first electrode 12 by the conducting wire. To do. Then, in the AC signal detection device 1, the AC signal guided to the first electrode 12 is detected and output as a received signal to the demodulator 402 by the output OUT, and the demodulator 402 demodulates the communication information from the received signal and receives it. The communication information demodulated in the side data processing unit 403 is processed.

Here, the transmitter 200 is, for example, a card-like device, and when the transmitter 2 is carried in a pocket or when the transmitter 200 is carried in a bag, the transmission electrode 203 and the human body 300 are connected to each other. It is configured to be capacitively coupled.
Further, as shown in FIG. 3b, the receiving electrode 401 of the receiver 4 is provided in a form covered with a non-conductive cover 410 so that a human hand can be brought close to the receiving electrode 401. With such a structure, when the hand of the human body 300 carrying the transmitter 200 is held over the receiving electrode 401 or the human hand touches the non-conductive cover 410, the receiving electrode 401 is surrounded by the surroundings of the human body. Of the electric field.

Here, FIG. 4 shows test data of the AC signal detection device 1 according to the present embodiment.
In the test, as shown in FIG. 4, a 3.0 Vpp, 10.7 MHz sine wave output from the signal generator 500 is applied to the transmission electrode 502 via a -40 dB attenuator (ATT) 501, and the transmission electrode 502 An alternating electric field by a sine wave was applied to the human body 300 from the right knee. Then, the hand of the human body 300 is placed on a non-conductive cover placed on the reception electrode 511, and the output of the AC signal detection device 1 in which the first electrode 12 is connected to the reception electrode 511 via a conducting wire is used with the oscilloscope 512. Observed.

As a result, according to the AC signal detection apparatus 1 shown in FIG. 1, a sine wave of 10.7 MHz and 538 mVpp could be observed. On the other hand, when the second electrode 13 was removed from the AC signal detection device 1 shown in FIG. 1, a sine wave of 10.7 MHz and 88 mVpp was observed.
Thereby, according to the AC signal detection device 1 provided with the second electrode 13 shown in FIG. 1, the AC signal detection device 1 is more than the AC signal detection device 1 described in Patent Document 1 that does not include the second electrode 13. It was confirmed that the sensitivity of can be improved.

It is a figure which shows the structure of the alternating current signal detection apparatus which concerns on embodiment of this invention. It is a figure which shows the structural example of the alternating current sensor which concerns on embodiment of this invention. It is a figure which shows the example of application of the alternating current signal detection apparatus which concerns on embodiment of this invention. It is a figure which shows the experimental data of the alternating current signal detection apparatus which concerns on embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... AC signal detection apparatus, 10 ... AC sensor, 11 ... Coil, 12 ... 1st electrode, 13 ... 2nd electrode, 20 ... Inversion amplification circuit, 21 ... FET.

Claims (5)

A first electrode to which an AC signal is applied;
Coils,
A second electrode;
A feedback circuit that adjusts the phase of an alternating current signal generated by the induced voltage of the coil and applies it to the second electrode;
The AC signal detecting device according to claim 1, wherein the first electrode and the second electrode are arranged so as to be close to the coil on opposite sides of the coil in the axial direction of the coil.
The AC signal detection device according to claim 1,
The AC signal detection device has a first capacitor,
The feedback circuit includes an inverting amplifier circuit that inverts and amplifies an AC signal due to the induced voltage of the coil, a resistor, and a first capacitor.
An output of the inverting amplifier circuit is applied to the second electrode via the resistor and the first capacitor;
An AC signal detection device, wherein an output of the inverting amplifier circuit is output as an output of the AC signal detection device via the second capacitor.
The AC signal detection device according to claim 2,
2. The AC signal detecting device according to claim 1, wherein the second capacitor is formed by two closely-spaced conductor patterns formed on the substrate so as to be separated from each other.
The AC signal detection device according to claim 1, 2, or 3,
A receiving electrode that is in close proximity to or in contact with a medium that induces an alternating electric field;
A conductive wire connecting the first electrode and the receiving electrode;
An AC signal detecting device, wherein an AC signal induced in a receiving electrode by the AC electric field is applied to the first electrode through the conducting wire.
A receiving device used in a transmission system that transmits an AC signal via a transmission medium that is a human body or a living body,
The AC signal detection device according to claim 4,
The transmission medium induces an AC electric field driven by an AC signal around the transmission medium,
The receiving apparatus, wherein the transmission medium is close to or in contact with the receiving electrode of the AC signal detecting apparatus.