JP2003163644A - Signal transmission system, signal transmitter, and signal receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce power consumption and to improve using feeling in the case of transmitting an AV signal wirelessly. <P>SOLUTION: After being FM-modulated by an FM modulation circuit 2 of a transmitter 1, a video signal is amplified by an amplifier circuit 3 and sent to an electrode 4. The sent signal is transmitted to an electrode 6 of a receiver 5 via a human body 10 to take out only a required frequency band by a selection circuit 7, and the signal is demodulated to the original signal by an FM demodulator circuit 8. Between the transmitter 1 and the receiver 5, the signal is transmitted by touching the electrodes with the body (both hands) 10. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to signal transmission over a short distance, and more particularly to a signal transmission system suitable for audio / video signal transmission.

[0002]

2. Description of the Related Art Conventionally, in a relatively short distance,
As a technical means for wirelessly transmitting audio / video (hereinafter referred to as AV) signals, a method using radio waves and a method using infrared rays are known. In AV equipment, if audio signals and video signals can be connected wirelessly, the usability is improved and it is very convenient. In reality, various devices are manufactured and sold for this purpose.

For example, for AV signals, infrared rays are used, and for audio signals only, infrared rays are used and weak radio waves are used. Technically, it is best to use radio waves. However, although there is a band allocation in the United States, in Japan, due to regulations of the Radio Law, a practical level output cannot be output, and transmission of a video signal is almost impossible.

Therefore, only the latter infrared method is practically used in Japan. Devices using infrared rays have been technically completed, and standardization as EIAJ (Japan Electronic Machinery Manufacturers Association) is progressing.

[0005]

By the way, in the above-mentioned infrared ray system, since light (infrared ray) is used, the directivity is sharp, and the installation position of the transmission / reception device between the transceivers is limited. The biggest drawback of the infrared method is that if there is an obstacle between the transmitter and the receiver, the optical path is blocked and transmission becomes impossible. Furthermore, it consumes a large amount of power (especially the LE on the transmission side).
D), Infrared transmission has not been put to practical use in portable devices.

On the other hand, with the widespread use of AV equipment in the world, the number of variations is increasing, and there is an increasing demand for wireless signal transmission even if the distance is very short. For example, in the case of video recording with a small camera and a small deck, if signal transmission between them can be performed wirelessly, usability is greatly improved. However, in the conventional infrared method, in such a case, even if the problem of power consumption is solved, it is not possible to exclude the possibility of blocking the light with an injured object such as the body,
The problem arises that signals cannot be transmitted between them.

The present invention has been made in view of the above circumstances, and provides a signal transmission system capable of wirelessly transmitting a signal, reducing the power consumption of a transmitting / receiving device, and improving the usability of the transmitting / receiving device. It is an object.

[0008]

The present invention has been made in consideration of the above problems, and a first aspect of the present invention is to provide a modulator for modulating an original signal and a first conductive member. ,
A signal transmitting device having an output section for outputting an output signal from the first conductive member; a second conductive member; a receiving section for receiving a signal from the second conductive member; A signal receiving device having a demodulation unit for demodulating,
In the signal transmission between the signal transmission device and the signal reception device, a human body in contact with the first conductive member and the second conductive member and a space formed between the transmission device and the reception device are formed. The signal transmission system is characterized in that an electromagnetic field is used as a transmission line.

However, the term "system" as used herein refers to a logical assembly of a plurality of devices (or functional modules that realize a specific function), and each device or functional module is a single casing. It does not matter whether it is in the body or not.

Further, a second aspect of the present invention comprises a modulator for modulating an original signal, a first conductive member, and an output unit for outputting an output signal from the first conductive member. The first conductive member is used when signal transmission is performed between a receiving device including the conductive member, the receiving unit that receives a signal from the second conductive member, and the demodulation unit that demodulates the received signal. And a human body in contact with the second conductive member and an electromagnetic field in a space formed between the transmitter and the receiver as a transmission path.

Further, a third aspect of the present invention comprises a second conductive member, a receiving unit for receiving a signal from the second conductive member, and a demodulating unit for demodulating the received signal, and the original signal When signal transmission is performed between a signal transmitting device including a modulating unit that modulates, a first conductive member, and an output unit that outputs an output signal from the first conductive member, the first conductive member is used. A signal receiving device, wherein a human body in contact with a member and the second conductive member and an electromagnetic field in a space formed between the transmitting device and the receiving device are used as a transmission path.

Here, an electrostatic magnetic field can be used as the electromagnetic field in the space formed between the transmitter and the receiver used as a transmission path.

In the signal transmission between the transmitter and the receiver, a ground to which the transmitter and the receiver are electrostatically coupled can be further used as a transmission line.

In the present invention, the modulation signal from the modulation means of the transmitter is output from the first conductive member exposed to the outside, and is transmitted to the second conductive member provided in the receiver through the human body. It is transmitted and demodulated by the demodulation means. Therefore, in actual use, signal transmission can be performed wirelessly, and the relative position between the transmission device and the reception / transmission is free, which greatly improves the usability. Further, the transmitter and the receiver require little electric power and can be applied to portable equipment.
Further, the receiving device may include an amplifier circuit that amplifies the modulated transmission signal. The original signal may be either a video signal or an audio signal, or both. Further, the modulation method may be frequency modulation.

Still other objects, features and advantages of the present invention are as follows.
It will be apparent from the embodiments of the present invention described later and the more detailed description based on the accompanying drawings.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings.

1. Schematic Configuration FIG. 1 shows the basic configuration of the entire transmission / reception device according to an embodiment of the present invention. In the figure, the transmitter 1 is basically an FM for left and right audio signals and a video signal.
Modulation circuit 2 and amplification circuit 3 for amplifying a mixed signal of them
Composed of. The carrier frequency is the same as the infrared transmission format, and it is approximately 11.5MHz to 1 for video signals.
3.5MHz, 2.8MHz for audio (R) signal,
The audio (L) signal is 2.3 MHz.

As shown in the figure, in the transmitter 1, instead of driving the LED in the final stage, the output of the amplifier circuit 3 is supplied to the electrode 4. The output of the amplifier circuit 3 is connected to the electrode 4 via a capacitor (not shown) and is cut off in terms of direct current. This is to secure a sufficient margin for the radio wave protection guideline issued by the Ministry of Posts and Telecommunications and to protect the device when the electrode 4 is short-circuited externally. Further, the output level of the electrode 4 is a weak electric power (500 μV /
M) It is set to be the following.

Next, the receiving device 5 selects a necessary frequency band from the signals input to the input electrode 6 and a left / right audio signal and a video signal F.
And an M demodulation circuit 8. On the receiving side, a high-impedance input circuit is provided in the selection circuit 7 instead of the pin diode, and the electrode 6 is connected as in the transmitter 1. These circuits are known, and a receiving circuit for infrared transmission is used in this embodiment. In this embodiment, the electrode 4 and the receiver 5 on the transmitter 1 side
Signal transmission is performed by touching the side electrode 6 with the body (both hands) 10.

2. Principle Next, the transmission principle of the transmission device 1 and the reception device 5 according to the present embodiment will be described with reference to FIGS. 2 to 8.

2-1. Transmission Principle FIG. 2 is a schematic conceptual diagram showing the basic configuration thereof for explaining the principle of signal transmission according to the present embodiment. As shown in FIG. 2, in this system, one side of the signal source on the side of the transmitting device 1 and
The configuration is such that one side of the receiving device 5 side is connected with the human body 10. Since most of the human body 10 is considered to be a conductive container made of water containing salt, it is almost a conductor in the several MHz band. When the DC resistance between both hands is measured with a tester or the like, it shows a value of 500 kΩ to 2.3 MΩ depending on the hand state.

In the measurements shown in FIGS. 4 and 5, both the output impedance of the tracking generator and the input impedance of the spectrum analyzer are 75Ω. Therefore, if the impedance between both hands is, for example, 1 megohm in terms of alternating current, the attenuation is -80d.
It should reach B. However, in reality, the amount of attenuation is much smaller, which proves the possibility of signal transmission through the human body.

As described above, the transmitting device 1 side is considered to be a small dipole antenna as shown in FIG. 2, and the state of the electromagnetic field generated by this is well analyzed. According to this, the state of the electromagnetic field generated by the human body becomes an electromagnetic field generated by the small dipole antenna as shown in FIG. 3, and the electric field E and the magnetic field H at the distance R from the length L dipole antenna are These are respectively expressed by the following formulas 1 and 2.

[0024]

[Equation 1]

[0025]

[Equation 2]

As can be seen from Equations 1 and 2, the strength of the electromagnetic field is the distance R from the antenna, the square of the distance R, and the distance R.
It is represented by a vector sum of components inversely proportional to the cube of, and is called a radiation electromagnetic field, an induction electromagnetic field, and an electrostatic magnetic field, respectively. Of these, there is no 1 / R ³ term in the component of the magnetic field H.

FIG. 6 is a characteristic diagram showing the relationship between the electric field strength of each term and the distance from the antenna. The voltage level has no special meaning. Further, in FIG. 7, the frequency f =
200MHz, transmission terminal voltage = 100dBμV (75
Ω), a λ / 2.2 dipole antenna and a 3.4 cmφ loop antenna, and 8 cmφ, 3.
It is a figure which shows the electric field strength and distance of a 4 cmphi loop antenna.

As shown in FIGS. 6 and 7, the intensity of the radiated electromagnetic field (1 / R term), the induced electromagnetic field (1 / R ² term), and the electrostatic magnetic field (1 / R ³ term) is λ. They become equal at a distance of / 2π, and increase sharply when the distance is less than this. f
= 11 MHz, this distance is about 4.3 m. Therefore, this method is a transmission method that mainly uses an electrostatic magnetic field, and is characterized by using a human body and an electrostatic magnetic field described below as transmission paths. Note that in general wireless transmission, a radiated electromagnetic field (term of 1 / R) is used because a sufficient distance from the antenna is considered.

2-2. Optimum carrier frequency In this embodiment, the format of the space transmission by the LED is used as it is, but the optimum frequency of the carrier should be determined in consideration of the spatial distance that prevails in the electrostatic magnetic field, the EMI regulation, the radio wave usage situation, and the like. Is desirable.

Electrostatic field: Any kind of electromagnetic field may be used for information transmission, but if the electrostatic field is mainly used, the higher the frequency of this part, the shorter the cover range. Considering the range that one person holds with his / her hand, it is thought that the diameter is about 2 m. Therefore, 2
About 0 MHz or less is desirable.

Radio wave usage status: 0.5 MHz to 1.6 MH
AM broadcasting is in the z band, and FM broadcasting is in the vicinity of 80 MHz.
Further, 90 MHz to 217 MHz has a VHF band of television, and 470 MHz to 886 MHz has a UHF band. Therefore, it is desirable to avoid this range.

EMI regulation: If the electric field strength is equal to or less than the following value, it is not regulated by the Radio Law. 332MHz or less 500μ
V / m 332 MHz to 10 GHz 35 μV / m

Therefore, it is desirable that the frequency be 332 MHz or less. Considering these points, it is understood that the frequency of infrared transmission is also suitable for contact transmission by hand.

2-3. Carrier level In this embodiment, since the electrostatic magnetic field is used, the signal level weakens in inverse proportion to the cube of the distance between the transmitter and the receiver, and the transmission quality tends to deteriorate when both hands are fully opened. Therefore, it is desirable that the transmission level be as large as possible within the Radio Law. Moreover, it is difficult to theoretically calculate the maximum level because the equivalent circuit of the human body is unknown. Therefore, in the present embodiment, it was determined experimentally by measuring the unnecessary radiation level and confirming that it is within the Radio Law.

2-4. Impact on the human body Even though it consumes a small amount of power, it transmits signals through the human body, so we must also consider the health effects. As a guideline for this, the Ministry of Posts and Telecommunications has issued a radio wave protection guideline. According to the radio wave protection guidelines, there are a condition P applied to a controlled electromagnetic environment and a condition G applied to an uncontrolled electromagnetic environment. The condition G expects a safety factor of about 5 times that of the condition P. .

Condition G is naturally applied to the general-purpose equipment. In addition, the guideline for low-power electromagnetic radiation sources does not require evaluation if the rated output is 7 W or less. However, caution is required when the radiation source is very close to the body.
In the case of the system according to the present embodiment, it is 7 W or less,
Since it will be used by touching the radiation source, consider the contact current in the pointer. In the guide, 100 kHz to 1
It is 45 mA or less (6 minutes) at 00 MHz.

The basis is as follows. Frequency is 1
At 00 kHz to 100 MHz, the inflow current is dominated not by the stimulating action but by the thermal action, and in this frequency band, the limit of burn injury due to contact current is said to be 200 mA.
Further, it is said that the sensing limit is set when 200 mA is 100 kHz or more. Therefore, the margin is determined with respect to this. At the commercial frequency, the inflow current is a stimulating effect, and is 1 mA or less in IEC and JIS.

Therefore, the trial calculation of the current flowing into the human body will be made below. FIG. 8 is a schematic configuration diagram showing the connection relationship between the output stage on the transmission side, the human body, and the reception side. In the figure, the GND on the transmitting side and the GND on the receiving side are electrostatically coupled. Therefore, although the electrostatic capacitance C should be taken into consideration in the current flowing through the human body, since the value cannot be determined, the inflow current was obtained assuming that the electrostatic capacitance C is infinite (that is, electrically connected).

As shown in FIG. 8, the frequency is about 13 MH.
z, and the level of the output section is 2 Vpp (0.71 Vrms). When the impedance of the human body is calculated based on the value measured in the above-mentioned item 3-1, it becomes about 7.5 kΩ. On the other hand, since a 100 pF capacitor couple is used between the driver and the human body, the impedance at 13 MHz is 120Ω even if the driver output impedance is 0Ω. That is, the current is 0.71V / 7.6.
2 kΩ = 0.093 mA. This is sufficiently smaller than the above-mentioned guideline, and there is no problem.

3. Details of Each Unit Next, detailed configurations of the above-described transmitting device and receiving device will be described with reference to FIGS. 9 and 10.

3-1. Transmission Device FIG. 9 is a block diagram showing a detailed configuration of the transmission device described above. In the figure, the buffer circuit 20 adjusts the level of the video signal V1 and supplies it to the modulation circuit 21. The modulation circuit 21 FM-modulates the level-adjusted video signal and supplies it to the bandpass filter 22. The bandpass filter is 11M for passing only the necessary carrier component.
It is a band pass filter of Hz, and supplies the mixing circuit 27 after filtering the FM modulation signal. On the other hand, the audio modulation circuits 23 and 24 FM-modulate the audio signals (L) A1 and (R) A2, respectively, and supply them to the bandpass filters 25 and 26.

The band pass filters 25 and 26 are respectively
A band-pass filter of 2.3 MHz and 2.8 MHz for passing only a necessary carrier component, which filters the FM-modulated audio signals A1 and A2 and supplies them to the mixing circuit 27. The mixing circuit 27 determines the mixing ratio of the video signal V1 and the audio signals A1 and A2 based on the resistance ratio, mixes the FM-modulated video signal V1 and the audio signals A1 and A2, and outputs the mixed signal MS to the buffer amplifier 28. Supply.

The buffer amplifier 28 corresponds to the amplifier circuit 3 shown in FIG. 1, amplifies the mixed signal MS to an appropriate level,
Deliver to electrode 4. In the case of conforming to the infrared transmission format by EIAJ, the carrier level, mixing ratio, etc. of the video / audio signal are fixed, but in the present invention, it is not necessary to comply with this.

3-2. Receiving Device FIG. 10 is a block diagram showing a detailed configuration of the receiving device described above. In the figure, the signal selection circuit 30 is shown in FIG.
Which corresponds to the selection circuit 7 shown in FIG. 1 and takes out a signal in a required frequency band from the signal supplied from the electrode 6 and supplies it to the bandpass filter 31 and the amplifier 35. The band pass filter 31 filters the signal extracted by the signal selection circuit 30 to pass only the carrier component of the video signal and supplies it to the limiter circuit 32. The limiter circuit 32 determines the signal level (amplitude).
Is suppressed to a constant value and supplied to the demodulation circuit 33. Demodulation circuit 3
3 outputs a video signal from the output signal of the limiter circuit and supplies it to the buffer amplifier 34. Buffer amplifier 3
Reference numeral 4 amplifies the video signal to a predetermined level and outputs it to the circuit in the subsequent stage.

On the other hand, the amplifier 35 includes the signal selection circuit 3
The signal extracted by 0 is amplified, and the band pass filters 36 and 3 corresponding to the audio signals (L) and (R) are amplified.
Supply to each of 7. Band pass filter 36, 37
Respectively filter the signal from the amplifier 35 to pass only the carrier component of the audio signal and supply it to the demodulation circuits 38 and 39. The demodulation circuits 38 and 39 respectively suppress the level (amplitude) of the signal to a constant value, take out the audio signals A1 and A2, and supply them to the buffer amplifiers 40 and 41. The buffer amplifiers 40 and 41 respectively amplify the audio signals A1 and A2 to a predetermined level and output them to the circuit in the subsequent stage.

4. Specific configuration example 4-1. Amplifier Circuit of Transmitter FIG. 11 shows an amplifier circuit 3 (2 which is the final stage of the transmitter 1.
It is a circuit diagram which shows the structure of 8). In the figure, the amplifier circuit 3 (28) is a conventional last stage LED for infrared transmission.
The configuration is similar to that of the modulation circuit for infrared transmission, except that the driver is removed and the electrode 4 is connected instead of being touched by hand. The operational amplifier OP1 is used as a normal inverting amplifier, and capacitors C1 (22 μF) and C2 (0.1 μ) are connected between the non-inverting input terminal and the ground.
F) and the resistor R1 (2.7 kΩ) are connected in parallel.
Further, the inverting input terminal (-) is connected to the other end of the feedback resistor R2 (10 kΩ), one end of which is connected to the output end, and the output end is connected to the resistor R3 (470 Ω) between the grounds. Has been done. Further, the output of the operational amplifier OP1 is connected to the electrode 4 via the capacitor C3 (10 pF) and is cut off in terms of direct current, as described above. Moreover, the electrode 4 uses a copper foil of 2 × 3 cm in the present embodiment.

The transmitter 1 is housed in a shielded plastic case, and is attached to the lower part of the video camera (CCD-G1) 30 as shown in FIG. 12, so that the whole can be driven by a battery (power supply) 31. In this way, by making the entire structure independent, it is possible to couple the ground portions on the transmitting side and the receiving side only by the electrostatic magnetic field in space. The electrode 4 is provided so as to be exposed on the main body of the video camera which is just touched by the hand when the video camera 30 is held by the hand. The video signal output from the video camera 30 is output to the camera connector 32.
It is adapted to be supplied to the transmission device 1 via a cable connected to.

It should be noted that when both the transmitting and receiving sides are operated by an AC adapter or the like, they can be surely coupled to the ground side, and high quality images can be obtained. However, it is necessary to consider when recording on the deck while holding the video camera by hand. I won't.

4-2. Selection Circuit of Receiving Device FIG. 13 is a circuit diagram showing the configuration of the selection circuit 7 (30) of the receiving device 5. In the figure, the selection circuit 7 (30)
Is a combination of the high impedance buffer 50 and the LC resonance circuit 51. Further, the electrode 6 uses a copper foil of 1 × 1 cm in this embodiment. Other than these, the configuration is the same as that of the infrared transmission circuit using LEDs, like the amplification circuit 3 of the transmission device 1, and therefore description thereof is omitted. The receiving device 5 is built in a tuner case for the GV-SX50 and outputs an image with the SX-50.

FIG. 14 is a characteristic diagram showing the frequency characteristic of the selection circuit 7 having the above-described structure, and FIG. 15 is a spectrum when the color bar is received in the same structure (measured at the SX-50 output terminal; The side is a characteristic diagram showing (using a breadboard). As shown in FIG. 14, the frequency characteristic of the selection circuit 7 has a characteristic that the frequency gradually rises from 1 MHz to about 15 MHz and then sharply attenuates thereafter. Further, as shown in FIG. 15, it can be seen that the spectrum when the color bar is received has a characteristic having a maximum peak near 15 MHz.

4-3. Characteristic Measurement In the above-described configuration shown in FIG. 12, it is difficult to measure the characteristic because both the video camera on the transmission side and the VW on the reception side are battery-driven. Therefore, the transmitting side uses a breadboard (commercial power source drive) for studying infrared transmission, and only the receiving side has a battery-driven VW.

FIG. 16 is a block diagram showing the structure of the transmission path characteristic measuring system in this case. In the figure, a breadboard 50 is used on the transmitting side, and the breadboard 50 is supplied with a video signal from a video signal generator (TG-7 / 1) 51 which is also driven by a commercial power source. It has become so. A VW (GV-SX50) 52 driven by a battery 53 is used on the receiving side, and its output is supplied to a noise meter (925D / 1) 54 driven by a commercial power source. The breadboard 50 has an output electrode 51 (corresponding to the electrode 4).
Similarly, the VW 52 on the receiving side is also provided with an electrode 52 (electrode 6) for input. The electrode 51 and the electrode 52 are electrically connected by the human body 10.

According to this structure, since the receiving side also connects the video out to the measuring instrument, it is equivalent to connecting the GND loops on the transmitting side and the receiving side. Therefore, the transmission conditions are better than the case where the video camera and the VW are used alone, and are considered as a rough guide. Below, the measured value measured by the said structure is shown. These were measured by the video characteristic measuring method of a VCR. Y S
/ N 47.5 dB Chroma AM 43 dB Chroma PM
44 dB

5. Operation of the present embodiment Next, an operation when the transmitting / receiving apparatus shown in FIGS. 9 and 10 described above is used will be described. The input video signal V1 is FM-modulated by the modulation circuit 21 after the level is adjusted in the buffer circuit. The audio signals A1 and A2 are also FM-modulated by the modulation circuits 23 and 24 after passing through a simple buffer circuit (not shown). After passing through the band-pass filters 22, 25, and 26 that pass only the necessary carrier components, the modulated outputs are mixed in the mixing circuit 27 according to the resistance ratio thereof,
It is amplified to an appropriate level by an amplifier and output from the electrode 4.

The signal transmitted from the electrode 4 is transmitted to the electrode 6 of the receiving device via the human body 10. The signal supplied to the electrode 6 is taken out by the signal selection circuit 30 in the required frequency band, and the carrier of the video signal V1 passes through the bandpass filter 31 and then passes through the limiter 32 and is demodulated by the demodulation circuit 33 to the original signal. Is demodulated to a video signal V1. On the other hand, the carriers of the audio signals A1 and A2 are amplified by the amplifier 35 and, after passing through the band pass filters 36 and 37, respectively, are demodulated into the original audio signals A1 and A2 by the demodulation circuits 38 and 39. It

6. Modification 6-1. Example in which carrier frequency is increased to provide multiple channels When an electrostatic magnetic field is used as in the present invention, the transmission distance is inversely proportional to the frequency. If the practical distance is 2 m, the carrier frequency will be about 20 MHz. Considering the use up to this band, a video signal of about 2 channels can be taken. There is ample room for audio channels. Therefore, the configuration described above may be used for multi-channel A / V transmission.

6-2. Multi-Channel, General-Purpose Signal Transmission In the above-described embodiment of the present invention, only A / V transmission has been described. However, a signal having a frequency band of about several MHz can be transmitted regardless of its contents, and the above-described configuration is used. May be used for other signal transmission. At this time, the number of channels may be determined by the band occupied by the signal to be transmitted.

[Supplement] The present invention has been described in detail with reference to the specific embodiments. However, it is obvious that those skilled in the art can modify or substitute the embodiments without departing from the scope of the present invention. That is, the present invention has been disclosed in the form of exemplification, and the contents of this specification should not be construed in a limited manner. In order to determine the gist of the present invention, the section of the claims described at the beginning should be taken into consideration.

[0059]

As described above in detail, according to the present invention,
The first conductive member of the transmitting device, which has a modulating unit that modulates the original signal, and outputs the final output signal from the first conductive member that is provided to be exposed to the outside, and demodulation that demodulates the received signal And a second receiving device that receives the received signal from a second conductive member that is exposed to the outside.
Since the signal transmission between the transmitting device and the receiving device is performed by the contact of the human body with the conductive member, the signal transmission can be performed wirelessly in actual use, and the transmitting device and the receiving device are connected. Since the relative position is free, the usability is greatly improved. Further, according to the present invention, the electric power required for the transmitting device and the receiving device is small, and it can be applied to a portable device. Further, there is an advantage that it is possible to improve the usability of a device that is worn on the body and used like a visortron.

In the communication system using the human body induced electric field, it is necessary to form at least one signal path between the transmitter and the receiver in addition to the human body. According to the signal transmission system of the present invention, the signal path other than the human body is transmitted by the transmitter-
The electromagnetic field in the space formed between the receivers is used.

On the other hand, for example, Japanese Patent Laid-Open No. 61-4663.
No. 7 and Japanese Patent Laid-Open No. 61-46639 disclose a contact unit capable of contacting a living body and a host unit equipped with a transmission circuit for transmitting and receiving a transmission signal of information via the contact electrode, and a host unit in contact with the surface of the living body. An information transmission device including a portable sub-unit provided with a biological electrode to be obtained and a transmission circuit for transmitting and receiving a transmission signal of information via the biological electrode is disclosed. Further, Japanese Patent Application Laid-Open No. 4-217086 discloses that information is transferred between an IC card reader and an IC card external device via a human body. However, in these conventional techniques, the ground is used as a signal path other than the human body. This is easily conceived by a person skilled in the art, because the respective publications make no mention of the spatial electromagnetic field or assume that the transmitter / receiver is grounded.

In other words, according to the signal transmission system of the present invention, the electromagnetic field in the space is used as a signal path other than the human body, so that it is not always necessary to ground the transceiver. That is, both the transmitter and the receiver can be configured as a portable device. On the other hand, in the above-mentioned conventional technique, since the ground is used for the signal path other than the human body,
At least one of the transceivers shall be configured as a grounded device.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of an entire transmission / reception device according to an embodiment of the present invention.

FIG. 2 is a schematic conceptual diagram showing the basic configuration of the signal transmission system for explaining the principle of signal transmission according to an embodiment of the present invention.

FIG. 3 is a conceptual diagram showing a state of an electromagnetic field generated by a small dipole antenna.

[Fig. 4] Transmission characteristics of the human body (between both hands) measured with a spectrum analyzer in the range of 1 MHz to 20 MHz.
FIG.

FIG. 5: Transmission characteristics of the human body (both hands) measured with a spectrum analyzer in the range of 1 MHz to 30 MHz
FIG.

FIG. 6 is a characteristic diagram showing the relationship between the electric field strength and the distance from the antenna.

FIG. 7 is a λ / 2.2 dipole antenna and 3.4 cm.
It is a characteristic view which shows the relationship between the electric field strength of the loop antenna of (phi), and the loop antenna of 8 cm (phi) and 3.4 cm (phi), and the distance from an antenna.

FIG. 8 is a schematic configuration diagram showing a connection relationship between an output stage on a transmitting side, a human body, and a receiving side for explaining how much current flows into a human body.

FIG. 9 is a block diagram showing a detailed configuration of a transmission device according to an embodiment of the present invention.

FIG. 10 is a block diagram showing a detailed configuration of a receiving device according to an embodiment of the present invention.

FIG. 11 is a circuit diagram showing a configuration of an amplifier circuit 3 (28) which is a final stage of the transmission device 1 according to the embodiment of the present invention.

FIG. 12 is an external view showing how the transmission device according to the embodiment of the present invention is attached to a video camera.

FIG. 13 is a circuit diagram showing a configuration of a selection circuit 7 (30) of the reception device 5 according to the embodiment of the present invention.

FIG. 14 is a characteristic diagram showing frequency characteristics of the receiving device according to the embodiment of the present invention.

FIG. 15 is a characteristic diagram showing a spectrum when the receiving apparatus according to the embodiment of the present invention receives a color bar.

FIG. 16 is a block diagram showing a configuration of a transmission path characteristic measurement system according to an embodiment of the present invention.

[Explanation of symbols]

1 ... Transmitting device 2 ... FM modulation circuit (modulation means) 3 ... Amplifying circuit 4 ... Electrode (first conductive member) 5 ... Receiving device 6 ... Electrode (second conductive member) 7 ... Selection circuit 8 ... FM demodulation circuit 33, 38, 39 ... Demodulation circuit 10 ... Human body 20 ... Buffer circuit 21, 23, 24 ... Modulation circuit 22, 31, 36, 37 ... Bandpass filter 27 ... Mixed circuit 28, 34, 40, 41 ... Buffer amplifier 30 ... Signal selection circuit 32 ... Limiter 35 ... Amplifier (amplification circuit) V1 ... Video signal (original signal) A1, A2 ... Audio signal (original signal)

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[Procedure amendment]

[Submission date] October 22, 2002 (2002.10.
22)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

7. The signal transmission between the transmission device and the reception device further uses as a transmission line a ground to which the transmission device and the reception device are electrostatically coupled. The signal receiving device described. ─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] December 5, 2002 (2002.12.
5)

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

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FIG. 16

Claims (7)

[Claims] 1. A signal transmitting device having a modulator for modulating an original signal, a first conductive member, and an output unit for outputting an output signal from the first conductive member, and a second conductive member. A signal receiving device that includes a member, a receiving unit that receives a signal from the second conductive member, and a demodulating unit that demodulates a received signal, and signal transmission between the signal transmitting device and the signal receiving device Then, a human body in contact with the first conductive member and the second conductive member, and an electromagnetic field in a space formed between the transmitter and the receiver are used as a transmission path. Signal transmission system. 2. A modulation unit that modulates an original signal, a first conductive member, and an output unit that outputs an output signal from the first conductive member, and a second conductive member and the second conductive member. When signal transmission is performed between a receiving device including a receiving unit that receives a signal from a conductive member and a demodulating unit that demodulates the received signal, the first conductive member and the second conductive member are The human body that comes into contact,
A signal transmitting device, wherein an electromagnetic field in a space formed between the transmitting device and the receiving device is used as a transmission path. 3. The signal transmitting apparatus according to claim 2, wherein an electrostatic magnetic field is used as the electromagnetic field. 4. The signal transmission between the transmission device and the reception device further uses a ground to which the transmission device and the reception device are electrostatically coupled as a transmission path. The signal transmission device described. 5. A modulation unit for modulating an original signal, and a first conductive unit, comprising a second conductive member, a receiving unit for receiving a signal from the second conductive member, and a demodulation unit for demodulating the received signal. Member and the first
A human body with which the first conductive member and the second conductive member come into contact when performing signal transmission with a signal transmitting device that includes an output unit that outputs an output signal from the conductive member of A signal receiving device, wherein an electromagnetic field in a space formed between the transmitting device and the receiving device is used as a transmission path. 6. The signal receiving apparatus according to claim 5, wherein an electrostatic magnetic field is used as the electromagnetic field. 7. The signal transmission between the transmission device and the reception device further uses as a transmission line a ground to which the transmission device and the reception device are electrostatically coupled. The signal receiving device described.