JPH07170215A - Signal transmitting system - Google Patents

Abstract

PURPOSE:To transmit a signal in a wireless state, to reduce the power consumption of a transmitter/receiver and further to improve the sense of use of the transmitter/receiver by outputting the signal from a conductive member exposed to the outside and transmitting it through a human body to a second conductive member installed at the receiver. CONSTITUTION:At a transmitter 1, an LED is not driven on the final stage but the output of an amplifier circuit 3 is supplied to an electrode 4. In this case, the output of the amplifier circuit 3 is connected through a capacitor to the electrode 4 and disconnected in the manner of DC. On the other hand, the output level of the electrode 4 is set so as to be lower than weak power regulated by the Radio Wave Act., when the human body touches it. On the reception side, the input circuit of a high impedance is provided inside a selecting circuit 7 in place of a pin diode, and an electrode 6 is connected similarly to the transmitter 1. Then, the signal is transmitted by touching the electrode 4 on the side of the transmitter 1 and the electrode 6 on the side of a receiver 5 with a body (both the hands) 10.

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 method 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]

In order to achieve the above object, the signal transmission system according to the invention as set forth in claim 1 has a modulation means for modulating the original signal, and the final output signal is exposed to the outside. A second conductive member that has the first conductive member of the transmitter that outputs from the first conductive member and demodulation means that demodulates the received signal, and is provided with the received signal exposed to the outside. When the human body comes into contact with the second conductive member of the receiving device, the signal transmission between the transmitting device and the receiving device is performed.

According to a second aspect of the present invention, there is provided the signal transmission system according to the first aspect, wherein the receiving device has an amplifier circuit for amplifying the modulated transmission signal. A signal transmission system according to a third aspect of the present invention is the signal transmission system according to the first aspect, wherein the original signal is either a video signal or an audio signal, or both. A signal transmission system according to a fourth aspect of the present invention is the signal transmission system according to the first aspect, wherein the modulation by the modulation means is frequency modulation.

[0010]

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,
It is transmitted to the second conductive member provided in the receiving device through the human body and demodulated by the demodulating 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.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. (1) Schematic Configuration FIG. 1 is a block diagram showing the basic configuration of the entire transmitting / receiving apparatus according to the present invention. In the figure, a transmission device 1 is basically composed of an FM modulation circuit 2 for left and right audio signals and a video signal, and an amplification circuit 3 for amplifying a mixed signal thereof. The carrier frequency is the same as the infrared transmission format, and the video signal is approximately 11.5 MHz to 13.
The frequency is 5 MHz, the audio (R) signal is 2.8 MHz, and 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 guidelines 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 includes a selection circuit 7 for extracting only a necessary frequency band from the signals input to the input electrode 6, and F of left and right audio signals and video signals.
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 transmitter 1 and the receiver 5 in this embodiment will be described with reference to FIGS. 2-1. Transmission Principle FIG. 2 is a schematic conceptual diagram showing a basic configuration for explaining the transmission principle of the present embodiment. As shown in FIG. 2, in this method, one side of the signal source on the transmitting device 1 side and one side of the receiving device 5 side are connected by 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.

Next, the transfer characteristics of the human body in the alternating current are shown in FIG.
And shown in FIG. FIG. 4 shows 1 MHz to 20 MHz, and FIG.
FIG. 3 is a characteristic diagram showing the transmission characteristics (both hands) of the human body measured using a spectrum analyzer in the range of 1 MHz to 30 MHz. Both are examples in the case where a coaxial cable is connected to the tracking generator and the input terminal. The ground GNDs of the coaxial cables were connected to each other so that they would not function as an antenna. As shown in FIGS. 4 and 5, the transfer characteristic in the range of about 1 MHz to 20 MHz is substantially flat and has an attenuation characteristic of 30 dB to 40 dB. The cause of the dip around 6 MHz and 17 MHz is unknown.

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 AC,
For example, if it is 1 megohm, the attenuation is -80.
It should reach dB. 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 transmitter 1 side is considered to be a small dipole antenna as shown in FIG. 2, and the state of the electromagnetic field generated by the antenna 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.

[0018]

[Equation 1]

[0019]

[Equation 2]

As can be seen from the equations 1 and 2, the strength of the electromagnetic field is represented by the vector sum of the components inversely proportional to the distance R from the antenna, the square of the distance R, and the cube of the distance R. It is called electromagnetic field, induction electromagnetic field, and electrostatic field.
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,
It is a figure which shows the electric field strength and distance of a loop antenna of 3.4 cm (phi). 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 / 2π. They are equal in distance and increase sharply below this distance.
If 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. However, 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: It is arbitrary to use any kind of electromagnetic field for information transmission, but if the electrostatic field is mainly used, the higher this frequency is, the shorter the cover range is. Considering the range that one person holds with his / her hand, it is thought that the diameter is about 2 m. Therefore, 20 MH
It is preferably about z or less.

Radio wave usage status: 0.5 MHz to 1.6 M
AM broadcasting is in the Hz band, and FM broadcasting is in the vicinity of 80 MHz. In addition, 90MHz-217MHz is VHF of TV
The UHF band is in the band of 470 MHz to 886 MHz.
Therefore, it is desirable to avoid this range.

EMI regulation: If the electric field strength is below the following value, it will not be regulated by the Radio Law. 332 MHz or less 500 μV / 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 becomes weak 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 this embodiment, it was determined experimentally by measuring an unnecessary radiation level and confirming that it was 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 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 of the present embodiment, it is 7 W or less, but since it is used by touching the radiation source, the contact current in the pointer will be examined. In the guide, 100 kHz to 100M
It is 45 mA or less (6 minutes) at Hz.

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 MHz,
The level of the output section is set to 2Vpp (0.71Vrms). 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 1 even if the driver output impedance is 0Ω.
It is 20Ω. That is, the current is 0.71V / 7.62.
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,
It is supplied to the mixing circuit 27. The mixing circuit 27 determines the video signal V1 and the audio signals A1 and A2 depending on the resistance ratio.
The FM-modulated video signal V1 and the audio signals A1 and A2 are mixed together and supplied to the buffer amplifier 28 as a mixed signal MS. Buffer amplifier 2
Reference numeral 8 corresponds to the amplifier circuit 3 shown in FIG. 1, amplifies the mixed signal MS to an appropriate level, and sends it to the electrode 4. EI
In the case of conforming to the infrared transmission format by AJ, the carrier level, the mixing ratio, etc. of the video / audio signal are fixed, but it is not necessary to comply with this in the present invention.

3-2. Receiving Device FIG. 10 is a block diagram showing a detailed configuration of the receiving device described above. In the figure, a signal selection circuit 30 corresponds to the selection circuit 7 shown in FIG. 1, extracts a signal in a necessary frequency band from the signal supplied from the electrode 6, and supplies the signal 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 described above.
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 the same as the infrared transmission modulation circuit except that the conventional final stage LED driver for infrared transmission is removed and the electrode 4 is connected instead of being touched by hand. It is the structure of. 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. Further, the electrode 4 uses a copper foil of 2 × 3 cm in this 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 reliably coupled to the ground side and high quality images can be obtained, but this is not considered when recording on a deck while holding a video camera by hand.

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
High impedance buffer 50 and LC resonance circuit 51
Is a combination of. 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 configuration, and FIG. 15 is a spectrum when the color bar is received in the same configuration (measured at the SX-50 output terminal; It is a characteristic view showing (using a board).
As shown in FIG. 14, the frequency characteristic of the selection circuit 7 is 1M.
The characteristic is that it gradually rises from Hz to about 15 MHz, and then rapidly attenuates after that. Also, as shown in FIG. 15, the spectrum when a color bar is received is
It can be seen that the characteristic has the maximum peak around 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 configuration of the transmission path characteristic measurement 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 is like this. Also,
On the receiving side, the VW (G
V-SX50) 52 is used, and its output is supplied to a noise meter (925D / 1) 54 driven by a commercial power supply. The breadboard 50 is provided with an output electrode 51 (corresponding to the electrode 4), and similarly, the reception side VW 52 is also provided with an input electrode 52 (electrode 6). The human body 10 is between the electrode 51 and the electrode 52.
Electrically connected by.

According to this configuration, 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 Embodiment Next, the 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 the demodulation circuit 3 via the limiter 32.
3 demodulates into the original 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 embodiments, only A / V transmission has been described, but any signal having a frequency band of about several MHz can be transmitted regardless of its content. It may be used for signal transmission. At this time, the number of channels may be determined by the band occupied by the signal to be transmitted.

[0042]

As described above, according to the present invention, the final output signal is output from the first conductive member that is provided with the modulating means for modulating the original signal and is exposed to the outside. The second conductive member of the transmitting device, which has the first conductive member and demodulation means for demodulating a received signal, and which receives the received signal from a second conductive member provided exposed to the outside. When the human body comes into contact with the conductive member of
Since the signal transmission between the transmitter and the receiver is performed, the signal can be transmitted wirelessly in actual use, and the relative position between the transmitter and the receiver is free, so that the usability is significantly improved. Further, the transmitter and the receiver require little electric power and can be applied to portable equipment. 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.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a signal transmission device of the present invention.

FIG. 2 is a schematic conceptual diagram showing a basic configuration for explaining a transmission principle of the embodiment.

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 in the embodiment.

FIG. 10 is a block diagram showing a detailed configuration of a receiving device in the embodiment.

FIG. 11 is a circuit diagram showing a configuration of an amplifier circuit, which is the final stage of the transmitter in the embodiment.

FIG. 12 is an external view showing how the transmission device is attached to the video camera in the embodiment.

FIG. 13 is a circuit diagram showing a configuration of a receiving circuit of the receiving apparatus in the embodiment.

FIG. 14 is a characteristic diagram showing frequency characteristics of the receiving apparatus in the embodiment.

FIG. 15 is a characteristic diagram showing a spectrum when the receiving device in the embodiment receives a color bar.

FIG. 16 is a block diagram showing a configuration of a transmission path characteristic measurement system of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 transmitter 2 FM modulation circuit (modulation means) 3 amplifier circuit 4 electrode (first conductive member) 5 receiver 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 Mixing 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)

Claims (4)

[Claims] 1. A first conductive member of a transmitting device, which has a modulation means for modulating an original signal, and outputs a final output signal from a first conductive member which is provided so as to be exposed to the outside, and a reception device. A human body comes into contact with the second conductive member of the receiving device that has demodulation means for demodulating a signal and receives the received signal from a second conductive member that is provided to be exposed to the outside. , A signal transmission method for performing signal transmission between the transmitter and the receiver. 2. The receiving device includes an amplifier circuit that amplifies a modulated reception signal.
Described signal transmission method. 3. The signal transmission system according to claim 1, wherein the original signal is either a video signal or an audio signal, or both. 4. The signal transmission system according to claim 1, wherein the modulation by the modulation means is frequency modulation.