JP2009213062A - Transmitter, communication system and communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To safely maintain a high transmission gain, without having to depend on the peripheral environment of a transmitting medium or an electrode, in an electrostatic field communication. <P>SOLUTION: A transmitter is provided for carrying out a transmission by using the electrostatic filed. The transmitter includes a first electrode for outputting a carrier wave on the transmitting medium, a second electrode electrostatically coupled to the first electrode, via at least a part of the transmitting medium and an oscillating part for forming a positive feedback circuit by using the electrostatic capacity of the electrostatic coupling between the first electrode and the second electrode to make the carrier wave oscillate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention generally relates to transmitters, communication systems, and communication methods.

  In recent years, a technique called electrostatic field communication has been proposed in which a signal is transmitted by changing an electric field between a transmitter and a receiver. In electrostatic field communication, radio communication is not performed using radioactive radio waves, but radio communication is performed using electrostatic coupling between an antenna and a transmission medium.

  Patent Documents 1 to 3 below disclose technologies that use a human body as a transmission medium for electrostatic field communication. Such technology is called human body communication, and is expected to be applied to data transmission between portable devices and devices that can be worn on the human body and other devices.

  Patent Documents 4 and 5 below are not limited to a human body as a transmission medium for electrostatic field communication, and eliminate the restriction of the use environment by eliminating a route as a reference for potential difference, thereby realizing stable communication.

JP-A-10-228524 JP-A-10-229357 Special table flat 11-509380 JP 2006-324774 A JP 2006-324775 A

  Generally, in a communication system, it is required to improve transmission gain and realize better communication characteristics. In electrostatic field communication, the transfer gain is governed by the capacitance of the transmitter and receiver electrodes and the transmission medium with respect to space or ground. However, these capacitances vary greatly depending on the shape of the electrode, the distance between the electrode and the transmission medium, and other surrounding environments, and it has been difficult to stably maintain a high transmission gain.

  The present invention has been made in view of the above problems, and a purpose thereof is to provide a new and improved transmitter, communication system, and communication capable of stably maintaining a high transfer gain in electrostatic field communication. It is to provide a method.

  In order to solve the above-described problem, according to an aspect of the present invention, a transmitter that performs transmission using an electrostatic field, the first electrode that outputs a carrier wave on a transmission medium, and the first electrode A second electrode that is electrostatically coupled to at least a part of the transmission medium and a capacitance of the electrostatic coupling between the first electrode and the second electrode. There is provided a transmitter comprising: an oscillating unit that forms a feedback circuit and oscillates the carrier wave.

  According to this configuration, the capacitance of the electrostatic coupling between the first electrode and the second electrode changes according to the characteristics of the transmission medium or the surrounding environment, and the electrostatic capacitance that changes as such. The carrier wave is oscillated by the positive feedback circuit including a capacitor. At this time, the oscillation frequency of the carrier wave is a resonance frequency corresponding to the characteristic of the positive feedback circuit. Accordingly, even when the characteristics of the transmission medium or the surrounding environment changes, it is possible to oscillate the carrier wave output from the first electrode onto the transmission medium at the resonance frequency.

  The transmitter may further include a modulation unit that generates a signal modulated according to information, and the signal may be transmitted by the carrier wave. According to such a configuration, it is possible to transmit the signal modulated by the carrier wave that oscillates stably at the resonance frequency.

  The modulation unit may modulate the signal by changing an oscillation state of the carrier wave. With this configuration, it is possible to transmit information with a high transfer gain without being affected by the changing frequency of the carrier wave.

  Further, the modulation unit may change the oscillation state of the carrier wave by controlling an offset applied to the output voltage of the oscillation unit. According to such a configuration, it is possible to saturate the output voltage of the oscillating unit with an offset to stop the oscillation of the carrier wave, and to resume the oscillation by eliminating the offset.

  Instead, the modulation unit may change the oscillation state of the carrier wave by controlling one or more circuit constants of the oscillation unit. According to this configuration, the oscillation can be resumed by changing the one or more circuit constants of the oscillation unit so as not to satisfy the oscillation condition of the circuit, stopping the oscillation, and satisfying the oscillation condition again.

  The modulation unit may modulate the signal by switching a power source of the oscillation unit. According to such a configuration, information can be transmitted without being affected by the changing frequency of the carrier wave.

  The transmitter may transmit power by the carrier wave. Power can be supplied by a carrier wave that stably oscillates at a resonance frequency.

  In order to solve the above problems, according to another aspect of the present invention, there is provided a communication system in which a transmitter and a receiver perform transmission using an electrostatic field, and the transmitter transmits a carrier wave on a transmission medium. Between the first electrode that outputs, the second electrode that is electrostatically coupled between the first electrode and at least a part of the transmission medium, and between the first electrode and the second electrode An oscillation unit that forms a positive feedback circuit using the electrostatic coupling capacitance and oscillates the carrier wave.

  According to such a configuration, in a communication system that performs transmission using an electrostatic field, output is stably performed on the transmission medium between the transmitter and the receiver even when the characteristics of the transmission medium or the surrounding environment changes. The carrier wave to be oscillated can be oscillated at the resonance frequency.

  In order to solve the above problems, according to still another aspect of the present invention, there is provided a communication method for performing transmission using an electrostatic field, wherein the first electrode and the second electrode are at least part of a transmission medium. The carrier wave is oscillated by a positive feedback circuit formed by using the electrostatic coupling capacitance between the first electrode and the second electrode, and the oscillated carrier wave is A communication method is provided in which transmission is performed by outputting from the first electrode.

  According to this configuration, in a communication method in which transmission is performed using an electrostatic field, the carrier wave output on the transmission medium is oscillated at the resonance frequency stably even when the characteristics of the transmission medium or the surrounding environment changes. It becomes possible.

  According to the present invention, it is possible to stably maintain a high transmission gain in electrostatic field communication.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially the same function, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  First, FIG. 1 is a conceptual diagram showing an example of an application scene of a communication system 10 according to an embodiment of the present invention. Referring to FIG. 1, the communication system 10 includes a transmitter 100 and a receiver 200. The transmitter 100 typically corresponds to a stationary device, and may be a general purpose computer such as a PC (personal computer) or a workstation, or a specific purpose communication device such as an IC card reader. Good. The receiver 200 typically corresponds to a portable device, and may be, for example, a mobile phone, a PDA (personal digital assistant), a game device having a communication function, or a music player. The transmitter 100 includes a power feeding circuit 102, a transmission electrode 110, and a transmission electrode 120. The receiver 200 includes a load circuit 202, a reception electrode 210, and a reception electrode 220.

  When communication is performed in the communication system 10 of FIG. 1, the transmission electrode 110 and the reception electrode 210, and the transmission electrode 120 and the reception electrode 220 are artificially arranged so as to face each other, as illustrated. As a result, electrostatic coupling occurs between the opposing electrodes, and a phase difference between both electrodes of the transmitter 100 is transmitted between both electrodes of the receiver 200 via the electrostatic coupling, thereby establishing communication.

  FIG. 2 is a conceptual diagram illustrating another example of an application scene of the communication system 10. The transmitter 100 and the receiver 200 shown in FIG. 2 typically correspond to portable devices as described above.

  When communication is performed in the communication system 10 of FIG. 2, as illustrated, one electrode (for example, the transmission electrode 110) of the transmitter 100 and one electrode (for example, the reception electrode 210) of the receiver 200 are relative to each other. To be placed artificially. This causes electrostatic coupling between a pair of opposing electrodes. Further, the other electrodes of the transmitter 100 and the receiver 200 (for example, the transmission electrode 120 and the reception electrode 220) both have a capacitance with respect to the space, and electrostatic coupling occurs between these electrodes through the space. Therefore, the communication system 10 forms a closed loop and communication is possible.

  FIG. 3 is a conceptual diagram showing still another example of an application scene of the communication system 10. Referring to FIG. 3, a human body as a transmission medium exists between the transmitter 100 and the receiver 200. Although a human body is shown here as a transmission medium, a conductor represented by a metal such as copper or iron, a dielectric represented by pure water or glass, or a composite thereof may be used as the transmission medium. Good. Further, as an embodiment of the present invention, a space between the transmitter 100 and the receiver 200 as shown in FIG. 1 or 2 may be used as a transmission medium.

  The transmitter 100 and the receiver 100 are artificially arranged such that one electrode (for example, the transmission electrode 110 and the reception electrode 210) is opposed to the transmission medium. As a result, electrostatic coupling occurs between the two electrodes disposed relative to the transmission medium and the transmission medium. Further, the other electrodes of the transmitter 100 and the receiver 100 (for example, the transmission electrode 120 and the reception electrode 220) are artificially arranged at positions relatively distant from the transmission medium. These two electrodes have a capacitance with respect to the space, and cause electrostatic coupling through the space. Therefore, the communication system 10 forms a closed loop and communication is possible.

  FIG. 4 is a schematic view showing the electrostatic coupling capacitance generated around each electrode as a component of the communication system described with reference to FIGS.

  The communication system 10 illustrated in FIG. 4 includes a transmitter 100 and a receiver 200 as in the above example. A transmission medium 300 exists between the transmitter 100 and the receiver 200. In FIG. 1 or FIG. 2, the transmission medium 300 is a transmission path between a pair of opposed electrodes (a part of the space between the transceiver and / or the housing of the transceiver (shown in FIG. 1 and FIG. 2). 3) corresponds to, for example, the human body in the figure. Further, there is a space 400 or a space 400 that means the ground around the transceiver.

  The transmitter 100 of the communication system 10 includes a power feeding circuit 102 and two electrodes 110 and 120. The receiver 200 includes a load circuit 202 and two electrodes 210 and 220. Of the four electrodes of the transmitter 100 and the receiver 200, the electrodes disposed near the transmission medium 300 are signal electrodes 110 and 210, and the electrodes disposed relatively far from the transmission medium 300 are reference electrodes 120, 220.

As shown by the symbol of the capacitive element in FIG. 4, two signal electrodes 110 and 210 are both transmission medium 300 attached electrostatically, with the electrostatic capacitance C _s. Further, two reference electrodes 120 and 220 are both space 400 attached electrostatically, having a capacitance _{C r.} As a result, a closed circuit passing through the power feeding circuit 102, the transmission medium 300, the load circuit 202, and the space 400 is formed, and the phase difference between both electrodes of the transmitter 100 is determined by both electrodes of the receiver 200 via electrostatic coupling. By being transmitted between them, a signal or power can be supplied from the power feeding circuit to the load circuit as will be described later. Note that the transmission medium 300 also has a capacitance C _m with respect to the space 400. This path is a loss from the viewpoint of transmission from the power supply circuit 102 to the load circuit 202. On the other hand, the electrostatic capacity of each signal electrode with respect to the space 400 and the electrostatic capacity of each reference electrode with respect to the transmission medium are not shown in the drawing, assuming that the contribution to the entire circuit is small.

In order to improve the communication characteristics of the communication system 10, it is desirable to increase the transmission gain. The transfer gain of the communication system 10 is governed by the aforementioned capacitances C _s and C _r , and these capacitances are the electrode shape, the distance between the signal electrode and the transmission medium, the distance between the reference electrode and the space, and the like. Fluctuates and is not stable. In the low frequency band, the transmission gain also decreases in proportion to the decrease in frequency.

  Therefore, as shown in FIG. 4, an inductive element L is mounted on the power supply circuit 102 and the load circuit 202, and LC resonance is generated between the transmitter 100 and the receiver 200 by impedance matching to improve the transfer gain. It is effective to make it.

  The transmission characteristic of the circuit when no inductive element is mounted on the power feeding circuit 102 and the load circuit 202 is expressed by Expression (1).

In Expression (1), it is assumed that the transmission medium 300 is a perfect conductor, and the signal source impedance r1 of the power feeding circuit 102 and the load impedance r2 of the load circuit 202 are both r (r1 = r2 = r). . Here C _p is the capacitance C _s and the reference electrode each signal electrode has to the transmission medium 300 is a series combined capacitance of the capacitance C _m with respect to the space 400, the formula (2) It is represented by

FIG. 5 is a plot of the transmission characteristic of equation (1). The horizontal axis represents the frequency [MHz] of the carrier used for communication, and the vertical axis represents the transfer gain [dB] between the transmitter and the receiver with respect to the frequency. Here, the signal source impedance r1 of the power feeding circuit 102 and the load impedance r2 of the load circuit 202 are set to r1 = r2 = 50Ω. Also, the electrostatic capacitance _C s = 7 pF between the transmission medium 300 and the signal electrodes. This numerical value is equal to the capacitance when two conductive disks having a radius of 5 cm are opposed in parallel with an interval of 1 cm. The capacitance C _r between each reference electrode and the space 400 was set to 3.5 pF. This value is equal to the capacitance of a conductor disk having a radius of 5 cm with respect to the space (or a sufficiently separated ground). Furthermore, the capacitance between the transmission medium 300 and the space 400 is C _m = 150 pF. This value is a value based on the fact that the human body has a capacitance of about 100 pF with respect to space. Referring to FIG. 5, it can be seen that the transmission gain when communication is performed using a carrier of 50 MHz, for example, is about −60 dB.

  On the other hand, assuming that the transmission medium 300 is a perfect conductor, the transmission characteristics of the circuit when the inductive element L is mounted on the power feeding circuit 102 and the load circuit 202 in FIG.

  Here, the transmission characteristic of Expression (3) is based on the assumption that LC resonance occurs. The resonance frequency of the LC resonance in Expression (3) is expressed by Expression (4).

  FIG. 6 is a plot of the transmission characteristic of equation (3). Here, the magnitude of the inductance to be mounted is L = 4000 μH. Referring to FIG. 6, the carrier wave causes LC resonance in the vicinity of 50 MHz, and the peak value of the transfer gain is about −5 dB. Therefore, by mounting the inductive element L on the power supply circuit 102 and the load circuit 202 of the communication system 10, the transmission efficiency in a certain frequency band (in the case of FIG. 6, around 50 MHz) is higher than when the inductive element L is not mounted. It can be seen that can be greatly improved.

However, in FIG. 6, a frequency band with good transmission efficiency (that is, a frequency band showing a high transfer gain) is limited to a narrow band around 50 MHz. This means that the transmission efficiency is drastically reduced even if the parameters (for example, C _p , C _m, etc.) that determine the transmission characteristics of Equation (3) slightly change. Then, these parameters that determine the transmission characteristics of Equation (3) can vary greatly depending on the electrode arrangement and the like as described above. Therefore, assuming various application scenes of the communication system 10 illustrated in FIGS. 1 to 3, communication with high transmission efficiency can be achieved simply by appropriately setting the inductance value of the inductive element in the circuit configuration of FIG. 4. It is understood that it is difficult to do.

  Therefore, as will be described in more detail below as an embodiment of the present invention, in the transmitter 100 of the communication system 10, electrostatic coupling between the signal electrode 110 and the reference electrode 120 via at least part of the transmission medium 300 is performed. An oscillation circuit is configured using electrostatic capacitance. In this way, it is possible to oscillate the carrier wave between the transmitter and the receiver at the impedance-matched resonance frequency and stably maintain a high transfer gain. Hereinafter, six embodiments according to the detailed configuration of the transmitter 100 will be described with reference to FIGS.

[First embodiment]
FIG. 7 shows the configuration of the transmitter 100 in the first embodiment. Referring to FIG. 7, the transmitter 100 includes a signal electrode 110, a reference electrode 120, an oscillation unit 130, and a modulation unit 140. Among these, the oscillation unit 130 and the modulation unit 140 correspond to the power feeding circuit 102 in FIG. 4. The oscillating unit 130 includes an amplifier 132, a resistor r, and an inductive element L arranged as shown in FIG. The modulation unit 140 includes a modulator 142, a field effect transistor (FET) 144, and a resistor R.

  In this embodiment, an LC series resonance circuit is applied. In this embodiment, as shown in the figure, the resistor r, the inductive element L, and the signal electrode 110 are connected in series in order from the output terminal of the amplifier 132. The reference electrode 120 is connected to the input terminal of the amplifier 132. In an ordinary LC series resonance circuit, a capacitive element is arranged in place of the signal electrode 110 and the reference electrode 120. In this embodiment, both electrodes are arranged to increase the parasitic capacitance, and the transmission medium 300 and the space are arranged. This is electrostatically coupled via 400 and used for oscillation of a carrier wave. Thus, on the equivalent circuit, a positive feedback circuit that makes a circuit with the signal electrode 110, the reference electrode 120, the amplifier 132, the resistor r, and the inductive element L is formed.

When the electrostatic coupling capacitance reaching through the transmission medium 300 and the space 400 from the signal electrode 110 to the reference electrode 120 and _{C x, C x} corresponds to the series combined capacitance of _{C s, C m, C r} in FIG. 4 . Using this C _x, loop transfer function H of the LC series resonance circuit according to the present embodiment (omega) is expressed by Equation (5). Note that k in the equation is an amplification factor of the amplifier 132.

  At this time, the oscillation frequency ω is expressed by Expression (6).

  The oscillation condition is expressed by equation (7).

  Here, when the values of k, r, and R are set so as to satisfy the oscillation condition of Expression (7), the carrier wave output from the signal electrode 110 to the transmission medium 300 oscillates at the frequency of Expression (6). The frequency of Expression (6) matches the resonance frequency of Expression (4). Therefore, it can be seen that the carrier wave oscillated in the transmitter 100 according to the present embodiment can oscillate at the resonance frequency regardless of the capacitance between the signal electrode 110 and the reference electrode 120. In order to oscillate the carrier wave, it is sufficient to set each circuit constant so that the left side of Equation (7) is equal to 1. However, when there is a delay in the positive feedback circuit, the circuit transfer function of Equation (5) changes, so that the influence of the delay is taken into consideration so that the left side of Equation (7) becomes larger than 1. It is preferable to set a constant. The consideration of the delay in the positive feedback circuit is the same for other embodiments described later.

  On the other hand, the input terminal of the amplifier 132 shown in FIG. 7 is connected to the FET 144 of the modulation unit 140 in addition to the reference electrode 120. The modulator 142 can switch the FET 144 according to the signal to be transmitted. As a result of this switching, when the input voltage level of the amplifier 132 changes, an offset corresponding to the signal to be transmitted occurs in the output voltage of the amplifier 132. When this offset is increased to a level equivalent to the power supply voltage (not shown) of the oscillation unit 130, for example, the output voltage is saturated and becomes constant, and oscillation stops. When the offset is eliminated, the output voltage returns to the original level and oscillation occurs again. Using such a principle, the oscillation and stop of the LC series oscillation circuit configured by the oscillation unit 130, the signal electrode 110, and the reference electrode 120 are controlled, and the signal is modulated and transmitted in the oscillation state (oscillation / stop). It becomes possible.

  Note that the method of controlling the oscillation state of the carrier wave is not limited to the method of switching the FET 144. For example, the power supply of the oscillation unit 130 may be switched instead of the FET 144. In addition, the oscillation state may be controlled by changing one or more circuit constants (r, L, R, etc.) according to the signal so as not to satisfy the oscillation condition of Expression (7).

  It should be noted that the frequency of the carrier wave oscillated by the oscillation circuit according to the present embodiment (the same applies to other embodiments described later in this specification) is changed according to the change in the characteristics of the application environment and is constant. Not. Therefore, in the load circuit of the receiver 200 illustrated in FIG. 4, it is desirable that the input impedance is increased and an inductance is not mounted on the load circuit 202 so that a carrier wave having a wide frequency range can be received.

  In addition, in order to leave room for adjusting the frequency of the carrier wave, a capacitive element is arranged in a part of the circuit to narrow the range in which the resonant frequency changes, or a variable capacitive element is arranged to control and stabilize the resonant frequency. You may make it. The stabilization of the resonance frequency will be described in more detail in connection with a third embodiment to be described later.

  With the configuration of the transmitter 100 according to the first embodiment described above, it is possible to perform electrostatic field communication while stably maintaining a high transfer gain by placing a signal on a carrier wave oscillating at a resonance frequency.

  It should be noted that the effect of the present invention that a high transmission gain can be stably maintained between the transceivers can be applied not only to communication for transmitting information signals but also to transmission of power between the transceivers. As an example, when power is supplied from a PC to a portable device in an application situation as shown in FIG. 1, the present invention is applied and a high transmission gain is obtained without requiring a cable for connecting the devices. Power can be supplied in the state.

[Second Embodiment]
Next, a second embodiment will be described. FIG. 8 shows the configuration of the transmitter 100 in the second embodiment. Also in the present embodiment, the transmitter 100 includes the signal electrode 110, the reference electrode 120, the oscillation unit 130, and the modulation unit 140. Among these, the oscillation unit 130 and the modulation unit 140 correspond to the power feeding circuit 102 in FIG. 4. The oscillation unit 130 includes an amplifier 132, an inductive element L, and resistors r, R, R1, and R2, which are arranged as shown in FIG. The modulation unit 140 includes a modulator 142 and a field effect transistor (FET) 144.

  In this embodiment, an LC series oscillation circuit is applied as in the first embodiment, and an operational amplifier is used as an amplifier. In this embodiment, as shown in the figure, the resistor r, the inductive element L, and the signal electrode 110 are connected in series in order from the output terminal of the amplifier 132. The reference electrode 120 is connected to the non-inverting input terminal of the amplifier 132 and the resistor R. The signal electrode 110 and the reference electrode 120 are further electrostatically coupled via the transmission medium 300 and the space 400. Thereby, on the equivalent circuit, a positive feedback circuit that makes a circuit with the signal electrode 110, the reference electrode 120, the amplifier 132, the resistor R, and the inductive element L is formed. The resistor R is connected to a reference potential point (hereinafter referred to as circuit GND) on the other side, and the input potential of the amplifier 132, that is, the operational amplifier is determined. The inverting input terminal of the amplifier 132 is connected to the resistors R1 and R2. On the other hand, the resistor R1 is connected to the FET 144 of the modulation unit 140, and the resistor R2 is connected to the output terminal of the amplifier 132, thereby realizing voltage amplification using an operational amplifier.

  The loop transfer function of the oscillation circuit according to the present embodiment is expressed by Expression (5) as in the first embodiment. Here, the amplification ratio k in equation (5) is represented by equation (8) in the case of the present embodiment.

  Therefore, in the case of the present embodiment, by setting the values of r, R, R1, and R2 so that the oscillation condition of Expression (7) is satisfied, the carrier wave oscillated in the transmitter 100 is converted into the signal electrode 110 and the reference electrode. It can be seen that it can oscillate at the resonance frequency regardless of the capacitance between 120. In the present embodiment, a case where a non-inverting amplifier circuit is configured using the amplifier 132 is illustrated. However, if the delay in the positive feedback circuit is π or more in terms of phase, an inverting amplifier circuit is used instead of a non-inverting amplifier circuit as necessary so that the amplification ratio k is 0 or less. You may comprise using 132.

  The role of the modulation unit 140 according to the present embodiment is the same as that in the first embodiment. That is, the modulator 142 switches the FET 144 according to the signal to be transmitted, controls the oscillation and stop of the LC series oscillation circuit constituted by the oscillation unit 130, the signal electrode 110, and the reference electrode 120, and the oscillation state (oscillation) / Stop), the signal can be modulated and transmitted. Instead, the power supply of the oscillation unit 130 is switched instead of the FET 144, or one or more circuit constants (r, R, R1, R2, etc.) are used as signals so as not to satisfy the oscillation condition of Equation (7). The oscillation state may be controlled by changing it accordingly.

  With the configuration of the transmitter 100 according to the second embodiment described above, it is possible to perform electrostatic field communication while stably maintaining a high transfer gain by placing a signal on a carrier wave oscillating at a resonance frequency.

[Third embodiment]
Next, a third embodiment will be described. FIG. 9 shows the configuration of the transmitter 100 in the third embodiment. Referring to FIG. 9, the transmitter 100 includes a signal electrode 110, a reference electrode 120, an oscillation unit 130, and a modulation unit 140. Among these, the oscillation unit 130 and the modulation unit 140 correspond to the power feeding circuit 102 in FIG. 4. Oscillator 130 comprises an amplifier 132 arranged as in FIG. 9, the resistor R, R1, R2, inductor L, and a capacitor _{C v.} The modulation unit 140 includes a modulator 142 and a field effect transistor (FET) 144.

The present embodiment is an application of a Colpitts type oscillation circuit known as one form of an LC oscillation circuit. In general, a Colpitts type oscillation circuit includes a positive feedback circuit including an inductive element and a capacitive element, and an amplifier circuit. In this embodiment, the signal electrode 110 is connected to the inductive element L and the resistor R as shown. Moreover, to connect the reference electrode 120 between the circuit GND and the capacitor _{C v.} The signal electrode 110 and the reference electrode 120 are further electrostatically coupled via the transmission medium 300 and the space 400. Thus, on the equivalent circuit, a positive feedback circuit that makes a circuit with the signal electrode 110, the reference electrode 120, the capacitive element C _v , and the inductive element L is configured.

  On the other hand, the amplifier 132 and the resistors R, R1, and R2 are used to configure an amplifier circuit. In this embodiment, the inverting input terminal of the amplifier 132 is connected between the resistors R1 and R2, the non-inverting input terminal is connected to the FET 144 of the modulator 140, and the output terminal is connected between the resistors R and R2. The amplifier circuit configured as described above amplifies the input voltage from the modulation unit 140 and transmits the amplified voltage to the positive feedback circuit. The carrier wave can be oscillated by the time difference from the voltage fed back by the positive feedback circuit.

With electrostatic coupling capacitance C _x extending through the transmission medium 300 and the space 400 from the signal electrode 110 to the reference electrode 120, the loop transfer function H of the oscillator circuit according to the present embodiment (omega) is the formula (9) expressed.

  At this time, the oscillation frequency ω of the oscillation circuit is expressed by Expression (10). The symbol // represents a parallel combined capacity.

  The oscillation condition of Equation (9) is expressed by Equation (11).

  Therefore, by configuring the circuit shown in FIG. 9 to satisfy this oscillation condition, the transmitter 100 according to the present embodiment can oscillate the carrier wave at the resonance frequency.

  On the other hand, as described above, the non-inverting input terminal of the amplifier 132 illustrated in FIG. 9 is connected to the FET 144 of the modulation unit 140. Thus, using the principle described in relation to the first embodiment, the FET 142 is switched by the modulator 142 in accordance with the signal to be transmitted, and the oscillation circuit is controlled to oscillate and stop, and the oscillation state is signaled. Can be modulated and transmitted. The method of controlling the oscillation state of the carrier wave is not limited to the method of switching the FET 144 described above, and the power source (not shown) of the oscillation unit 130 may be switched instead of the FET 144. Further, the oscillation state may be controlled by changing one or more circuit constants (R1, R2, etc.) according to the signal so that the oscillation condition of Expression (11) is not satisfied.

  With the configuration of the transmitter 100 according to the third embodiment described above, it is possible to perform electrostatic field communication while stably maintaining a high transfer gain by placing a signal on a carrier wave oscillating at a resonance frequency.

Here, it may adjust the frequency of the carrier using an electrostatic capacitance C _v shown in FIG. The oscillation frequency in this case is determined by the combined capacitance of the capacitance between the electrostatic capacitance C _v and the electrode. Further, the frequency of the carrier wave may be stabilized by making the capacitance _Cv variable and controlling the combined capacitance to be constant. For example, a local oscillator, a phase comparator for detecting a phase difference between the output frequency of the output frequency and the signal electrodes 110 of the local oscillator, and a variable capacitance C _v the voltage across the on the basis of the phase difference that oscillates at a predetermined frequency By further including a loop filter that changes the oscillation frequency, a feedback loop can be configured to stabilize the oscillation frequency.

[Fourth embodiment]
Next, a fourth embodiment will be described. FIG. 10 shows the configuration of the transmitter 100 in the fourth embodiment. Also in the present embodiment, the transmitter 100 includes the signal electrode 110, the reference electrode 120, the oscillation unit 130, and the modulation unit 140. Among these, the oscillation unit 130 and the modulation unit 140 correspond to the power feeding circuit 102 in FIG. 4. Oscillation unit 130 includes transistor 134, a power supply 136 arranged as in FIG. 10, inductor L, and capacitor element C, and _{C v.} The modulation unit 140 includes a modulator 142 and a field effect transistor (FET) 144.

This embodiment applies a Colpitts oscillation circuit as in the third embodiment, but differs from the third embodiment in that a transistor 134 is used as an amplifier circuit. In this embodiment, as shown in the drawing, the signal electrode 110 is connected between the emitter of the transistor 134 and the capacitive element _Cv . The reference electrode 120 is connected between the circuit GND and the induction element L and the circuit GND. The signal electrode 110 and the reference electrode 120 are further electrostatically coupled via the transmission medium 300 and the space 400. Accordingly, in the equivalent circuit, the signal electrode 110, reference electrode 120, the positive feedback circuit to cycle the inductor L, and capacitor element C _v is the configured.

The base of the transistor 134 is provided between the inductor L and the capacitance element C _v, the emitter between the capacitive element C _v and the signal electrode 110, and the collector is connected to the power source 136. As a result, the input voltage from the modulation unit 140 is amplified and transmitted to the positive feedback circuit described above. The carrier wave can be oscillated by the time difference from the voltage fed back by the positive feedback circuit.

Capacitive element C _v in FIG. 10 is assumed to have a smaller capacitance than the electrostatic coupling capacitance C _x leading to the reference electrode 120 via the transmission medium 300 and the space 400 from the signal electrode 110. Similar to the third embodiment, the transfer function of the oscillation circuit of this embodiment is expressed by equation (9), and the oscillation frequency is expressed by equation (10). Therefore, by configuring the circuit shown in FIG. 10 so as to satisfy the oscillation condition of Expression (11), the carrier wave can be oscillated at the resonance frequency in the transmitter 100 according to the present embodiment.

  In the present embodiment, unlike the third embodiment, the FET 144 of the modulation section 140 is connected to the power source 136 of the oscillation section 130. Then, by controlling the output of the FET 144 by the modulator 142 according to the signal to be transmitted, the power supply from the power source 136 to the oscillation unit can be switched. Thereby, it is possible to control oscillation and stop of the oscillation circuit configured in this embodiment, and to modulate and transmit the signal to the oscillation state.

  With the configuration of the transmitter 100 according to the fourth embodiment described above, it is possible to perform electrostatic field communication while stably maintaining a high transfer gain by placing a signal on a carrier wave oscillating at a resonance frequency.

[Fifth embodiment]
Next, a fifth embodiment will be described. FIG. 11 shows the configuration of the transmitter 100 in the fifth embodiment. Referring to FIG. 11, the transmitter 100 includes a signal electrode 110, a reference electrode 120, an oscillation unit 130, and a modulation unit 140. Among these, the oscillation unit 130 and the modulation unit 140 correspond to the power feeding circuit 102 in FIG. 4. The oscillating unit 130 includes an amplifier 132, resistors R, R1, and R2 and inductive elements L1 and L2 that are arranged as shown in FIG. The modulation unit 140 includes a modulator 142 and a field effect transistor (FET) 144.

  In this embodiment, a Hartree type oscillation circuit, which is known as one form of an LC oscillation circuit, is applied. In general, the Hartree-type oscillation circuit has a configuration in which a part of the voltage is positively fed back from the middle of the inductive element connected in parallel with the capacitive element of the Colpitts-type oscillation circuit. In this embodiment, one end of each of the inductive elements L1 and L2 is connected to the circuit GND, and this is an intermediate point where a part of the voltage is fed back. The signal electrode 110 is connected between the inductive element L2 and the resistor R. The reference electrode 120 is connected to the wiring between the induction element L1 and the resistor R1 and the circuit GND. The signal electrode 110 and the reference electrode 120 are further electrostatically coupled via the transmission medium 300 and the space 400, and serve as a capacitive element connected in parallel with the induction elements L1 and L2.

  On the other hand, the amplifier 132 and the resistors R, R1, and R2 are used to configure an amplifier circuit as in the third embodiment. Also in this embodiment, the inverting input terminal of the amplifier 132 is connected between the resistors R1 and R2, the non-inverting input terminal is connected to the FET 144 of the modulator 140, and the output terminal is connected between the resistors R and R2. The input voltage from the modulation unit 140 is amplified by the amplifier circuit configured as described above, and the carrier wave can be oscillated by the time difference between the input and output of the positive feedback voltage.

Using an electrostatic coupling capacitance C _x extending through the transmission medium 300 and the space 400 from the signal electrode 110 to the reference electrode 120, in the open loop transfer function H of the oscillator circuit according to the present embodiment (omega) is the formula (12) expressed.

  At this time, the oscillation frequency ω is expressed by Expression (13).

  The oscillation condition of Expression (12) is expressed by Expression (14).

Here, when the inductive elements L1 and L2 are regarded as one inductive element having the circuit GND as an intermediate point (inductance is L ₁ + L ₂ ), the oscillation frequency ω represented by the equation (13) is expressed by the equation (4). It is equivalent to the resonance frequency of. Therefore, by configuring the circuit shown in FIG. 11 so as to satisfy the oscillation condition of Expression (14), the carrier wave can be oscillated at the resonance frequency in the transmitter 100 according to the present embodiment.

  Also in the present embodiment, as in the third embodiment, the non-inverting input terminal of the amplifier 132 of the oscillation unit 130 is connected to the FET 144 of the modulation unit 140. Thus, using the principle described in relation to the first embodiment, the FET 142 is switched by the modulator 142 in accordance with the signal to be transmitted, and the oscillation circuit is controlled to oscillate and stop, and the oscillation state is signaled. Can be modulated and transmitted. The method of controlling the oscillation state of the carrier wave is not limited to the method of switching the above-described FET 144, and the power supply of the oscillation circuit may be switched instead of the FET 144. In addition, the oscillation state may be controlled by changing one or more circuit constants (R1, R2, L1, L2, etc.) according to the signal so as not to satisfy the oscillation condition of Expression (14).

Further, in order to adjust the frequency of the carrier wave, a capacitance C _v (not shown) that connects the wiring between L1 and R1 and the wiring between L2 and R2 may be additionally provided. In this case, the oscillation frequency is determined by the parallel combined capacitance of the electrostatic coupling capacitance C _x between the electrostatic capacitance C _v and the signal electrodes 110 - a reference electrode 120. However, in order to maintain the communication that oscillates at the resonance frequency, it is desirable that the added capacitance C _v be smaller than C _x . In addition, in order to stabilize the resonance frequency, the electrostatic capacity _Cv is variable, and a local oscillator, a phase comparator, and a loop filter are further provided as in the above description related to the third embodiment. The capacity _Cv may be controlled.

  With the configuration of the transmitter 100 according to the fifth embodiment described above, it is possible to perform electrostatic field communication while stably maintaining a high transfer gain by placing a signal on a carrier wave oscillating at a resonance frequency.

[Sixth embodiment]
Next, a sixth embodiment will be described. FIG. 12 shows the configuration of the transmitter 100 in the sixth embodiment. As in the previous embodiment, the transmitter 100 includes a signal electrode 110, a reference electrode 120, an oscillation unit 130, and a modulation unit 140. Among these, the oscillation unit 130 and the modulation unit 140 correspond to the power feeding circuit 102 in FIG. 4. Oscillation unit 130 includes a transistor 134, a power supply 136, inductive element L1, L2, and a capacitor _{C v} arranged as in FIG. 12. The modulation unit 140 includes a modulator 142 and a field effect transistor (FET) 144.

This embodiment applies a Hartree type oscillation circuit as in the fifth embodiment, but differs from the fifth embodiment in that a transistor 134 is used as an amplifier circuit. In this embodiment, an intermediate point between the inductive elements L1 and L2 is connected to the emitter of the transistor 134 to feed back a part of the voltage. The signal electrode 110 is connected to the base and the capacitive element _{C v} of the transistor 134. The reference electrode 120 is connected circuit GND, and the capacitor _{C v} and the inductive element L2. The signal electrode 110 and the reference electrode 120 are further electrostatically coupled via the transmission medium 300 and the space 400, and serve as a capacitive element connected in parallel with the induction elements L1 and L2.

Capacitive element C _v in FIG. 12 is assumed to have a smaller capacitance than the electrostatic coupling capacitance C _x leading to the reference electrode 120 via the transmission medium 300 and the space 400 from the signal electrode 110. As in the fifth embodiment, the oscillation frequency of the oscillation circuit configured in this embodiment is determined by Expression (13). Therefore, by configuring the circuit shown in FIG. 12 so as to satisfy the oscillation condition of Expression (14), the carrier wave can be oscillated at the resonance frequency in the transmitter 100 according to the present embodiment.

  In the present embodiment, unlike the fifth embodiment, the FET 144 of the modulation section 140 is connected to the power source 136 of the oscillation section 130. Then, by controlling the output of the FET 144 by the modulator 142 according to the signal to be transmitted, the power supply from the power source 136 to the oscillation unit can be switched. Thereby, it is possible to control oscillation and stop of the oscillation circuit configured in this embodiment, and to modulate and transmit the signal to the oscillation state.

  With the configuration of the transmitter 100 according to the sixth embodiment described above, it is possible to perform electrostatic field communication while stably maintaining a high transfer gain by placing a signal on a carrier wave oscillating at a resonance frequency.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention belongs can come up with various changes or modifications within the scope of the technical idea described in the claims. . And it is understood that such modified examples also belong to the technical scope of the present invention.

  For example, in general, a transmitter, a communication system, and a communication method that actively increase the floating capacitance of a wiring portion in an oscillation circuit by connecting an electrode or the like and actively utilize this for oscillation Should be understood as belonging to the technical scope of the present invention.

  Further, for example, as a method of modulating a carrier wave, (i) changing the input voltage level of the amplifier of the oscillating unit according to the signal, (ii) switching the power source of the oscillating unit, (iii) changing one or more circuit constants Although the three methods of making them have been described, a part of the wiring of the oscillation circuit may be switched instead.

  Furthermore, as described above, the present invention may be applied to supply of power from a transmitter to a receiver instead of being applied to transmission of an information signal by electrostatic field communication.

It is the schematic which shows the example of application of the communication system which concerns on one Embodiment of this invention. It is the schematic which shows another example of application of the communication system which concerns on one Embodiment of this invention. It is the schematic which shows another example of application of the communication system which concerns on one Embodiment of this invention. It is a block diagram which shows the structure of the communication system which concerns on one Embodiment. It is the characteristic view which plotted the communication characteristic when not introducing an inductance to a transceiver. It is the characteristic view which plotted the communication characteristic in case inductance can be introduce | transduced into a transmitter / receiver and LC resonance can be produced. It is a block diagram which shows the structure of the transmitting apparatus which concerns on a 1st Example. It is a block diagram which shows the structure of the transmitting apparatus which concerns on a 2nd Example. It is a block diagram which shows the structure of the transmitting apparatus which concerns on a 3rd Example. It is a block diagram which shows the structure of the transmitting apparatus which concerns on a 4th Example. It is a block diagram which shows the structure of the transmitting apparatus which concerns on a 5th Example. It is a block diagram which shows the structure of the transmitter which concerns on a 6th Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Communication system 100 Transmitter 110 Signal electrode 120 Reference electrode 130 Oscillator 140 Modulator 200 Receiver 300 Transmission medium 400 Space

Claims (9)

A transmitter that performs transmission using an electrostatic field,
A first electrode for outputting a carrier wave on a transmission medium;
A second electrode electrostatically coupled to the first electrode via at least a part of the transmission medium;
An oscillation unit that forms a positive feedback circuit using the electrostatic coupling capacitance between the first electrode and the second electrode to oscillate the carrier wave;
Transmitter.   The transmitter according to claim 1, further comprising a modulation unit that generates a signal modulated according to information, and transmits the signal using the carrier wave.   The transmitter according to claim 2, wherein the modulation unit modulates the signal by changing an oscillation state of the carrier wave.   The transmitter according to claim 3, wherein the modulation unit changes the oscillation state of the carrier wave by controlling an offset applied to an output voltage of the oscillation unit.   The transmitter according to claim 3, wherein the modulation unit changes the oscillation state of the carrier wave by controlling one or more circuit constants of the oscillation unit.   The transmitter according to claim 2, wherein the modulation unit modulates the signal by switching a power source of the oscillation unit.   The transmitter according to claim 1, wherein the transmitter transmits power using the carrier wave. A communication system in which a transmitter and a receiver perform transmission using an electrostatic field,
The transmitter is
A first electrode for outputting a carrier wave on a transmission medium;
A second electrode electrostatically coupled to the first electrode via at least a part of the transmission medium;
An oscillation unit that oscillates the carrier wave by forming a positive feedback circuit using a capacitance of the electrostatic coupling between the first electrode and the second electrode;
A communication system comprising: A communication method for performing transmission using an electrostatic field,
Electrostatically coupling the first electrode and the second electrode through at least part of the transmission medium;
A carrier wave is oscillated by a positive feedback circuit formed using a capacitance of the electrostatic coupling between the first electrode and the second electrode;
The oscillated carrier wave is output from the first electrode and transmitted.
Communication method.

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