JP4107982B2 - coaxial cable - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coaxial cable, and more particularly to a coaxial cable in which a central conductor is used for video transmission and a conductor and a conductor outside the conductor are provided on a concentric outer periphery centering on the central conductor.
[0002]
[Prior art]
A coaxial cable having a characteristic impedance of 75Ω is generally used for video transmission. It is known that the attenuation of the video signal can be approximated by a phenomenon that is approximately 1/2 the frequency. For example, in a 3C-2V coaxial cable, the attenuation is 27 dB / Km when the frequency of the video signal is 4 MHz, the attenuation is 32 dB / Km when the frequency of the video signal is 6 MHz, and the frequency of the video signal is 8 MHz. In this case, the measured value is disclosed that the attenuation is 38 dB / Km, the frequency of the video signal is 10 MHz, and the attenuation is 42 dB / Km. From these measured values, it can be seen that, generally, the higher the video frequency, the greater the degree of attenuation. By the way, as a cause of the attenuation of the video signal, various factors can be considered in addition to the characteristic impedance of the coaxial cable. Among these factors, there is noise caused by external factors other than noise caused by the video signal itself. It is known that the noise caused by this external factor causes the attenuation of the video signal and the disturbance of the video signal. Here, it is assumed that the disturbance of the video signal due to noise caused by the external factor is included in the broad attenuation.
[0003]
Incidentally, a cable compensator is used as necessary to compensate for the attenuation of the video signal. The cable compensator is a means for amplifying the video signal, and is an indispensable means for providing an image having no influence of attenuation as much as possible or for compensating for the attenuation. The cable compensator is provided in advance for each predetermined distance according to the attenuation state of the video signal, and amplifies the video signal each time. In the case of a general coaxial cable, one cable compensator is installed at about 100 m.
[0004]
However, when a video signal attenuated by a cable compensator is amplified, a phenomenon occurs in which noise is also amplified simultaneously. In the case of noise, the amplified noise amplified by one cable compensator is further amplified by the next cable compensator, and as a result of repeating amplification from the next to the next, the attenuation of the video signal in a broad sense is accelerated. It was. Thus, a cable compensator must be used to compensate for the attenuation of the video signal, but conversely, if a large number of cable compensators are used, a clear image can no longer be obtained due to noise. It was the result.
[0005]
With respect to such a coaxial cable, the inventor of the present application first disclosed a coaxial cable in which the first cylindrical electromagnetic shielding conductor and the second cylindrical electromagnetic shielding conductor are configured to supply a device driving current. (For example, refer to Patent Document 1). In this coaxial cable, a first cylindrical electromagnetic shielding conductor is provided outside the center conductor via an insulator, and a second cylindrical electromagnetic shielding is provided outside the first cylindrical electromagnetic shielding conductor via an insulator. A shielding conductor is provided, and the outer periphery of the second cylindrical electromagnetic shielding conductor is covered with an outer sheath of an insulator, and the first cylindrical electromagnetic shielding conductor and the second cylindrical electromagnetic shielding conductor are connected to a device driving current. It is configured for feeding. According to this coaxial cable, for example, when the first cylindrical electromagnetic shielding conductor on the inner side is minus and the second cylindrical electromagnetic shielding conductor on the outside is electrified, the space in these central portions has zero magnetism. As a result, the central conductor is not disturbed by any magnetic force, and a barrier is formed by the magnetic action generated in the central conductor, so that it is possible to prevent the intrusion of disturbing radio waves from the outside. Therefore, for example, the video waveform sent from the surveillance camera is not disturbed at all, and the monitor image is not disturbed, and a clear image can be obtained.
[0006]
[Patent Document 1]
Utility Model Registration No. 3024770 (FIG. 1)
[0007]
[Problems to be solved by the invention]
However, among external noises, for example, whether it is possible to eliminate the influence of high-frequency noise having a steep waveform that occurs when the accelerator is suddenly depressed from the electric system of an engine such as a motorcycle is an issue in commercialization. It was. In addition, when transmitting video, it has been a problem in practical use whether a clear image without attenuation can be sent to a distance of a superior position without using a cable compensator.
[0008]
The present invention has been made to solve the above-described problems, and its purpose is to completely shut out external noise and transmit a video signal that is not affected by the noise over a long distance. Is to provide a simple coaxial cable.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a first aspect of the coaxial cable according to the present invention provides a first conductor on an outer periphery of a center conductor via an insulator, is concentrically centered on the center conductor, A second conductor is provided on the outer side of one conductor via an insulator, the outer side of the second conductor is covered with an outer covering of the insulator, and a DC voltage is applied between the first conductor and the second conductor. A configuration is provided in which a voltage source that can be applied is provided.
[0010]
In order to achieve the above object, a second aspect of the coaxial cable according to the present invention provides a first conductor on an outer periphery of a center conductor via an insulator, is concentrically centered on the center conductor, A second conductor is provided outside the first conductor via an insulator, and the outer side of the second conductor is covered with an outer covering of the insulator, so that a direct current flowing in the first conductor and the second conductor is generated. A DC voltage source capable of applying a DC voltage having a predetermined voltage value is provided between the first conductor and the second conductor so as to take a desired value, and the first conductor on the outer periphery of the center conductor A configuration is adopted in which a noise barrier zone formed by electromagnetic action by a desired current is formed in a portion surrounded by the second conductor.
[0011]
In order to achieve the above object, the third aspect of the coaxial cable of the present invention has a configuration in which, in the first or second aspect, the first conductor and / or the second conductor is a braided conductor. take.
[0012]
In order to achieve the above object, according to a fourth aspect of the coaxial cable of the present invention, in any one of the first to third aspects, the second conductor is provided on the outer periphery of the first conductor via an insulator. In addition, a configuration comprising a plurality of conductors is employed.
[0013]
In order to achieve the above object, according to a fifth aspect of the coaxial cable of the present invention, in any one of the first to third aspects, the second conductor is wound around the outer periphery of the first conductor via an insulator. The structure which consists of the conductor provided by turning is taken.
[0014]
In order to achieve the above object, according to a sixth aspect of the coaxial cable of the present invention, in any one of the first to fifth aspects, the first conductor side is positive and the second conductor side is negative. A DC voltage having a predetermined power supply voltage value is applied so as to be a voltage, and a DC current having a desired current value is passed through the first conductor and the second conductor.
[0015]
In order to achieve the above object, according to a seventh aspect of the coaxial cable of the present invention, in any one of the first to sixth aspects, the power supply voltage value of the DC voltage source is in the range of 10V to 30V. The configuration is as follows.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0017]
FIG. 1 is a schematic diagram of a coaxial cable according to an embodiment of the present invention. In FIG. 1, 1 is a coaxial cable, 2 is a central conductor for transmitting signals such as video, 3 is a first conductor on the concentric outer periphery of the central conductor 2, and 4 is an outer periphery of the first conductor on the concentric outer periphery of the central conductor 2. 2 is a first insulator made of polyvinyl chloride (PVC) or the like on the outer periphery of the center conductor 2, and 6 is a polyvinyl chloride (polyvinyl chloride) interposed between the first conductor 3 and the second conductor 4 ( A second insulator made of PVC), 7 is a third insulator made of polyvinyl chloride (PVC) or the like outside the second conductor 4, and 8 is a predetermined insulator between the first conductor 3 and the second conductor 4. This is a DC voltage source for applying a DC voltage having a voltage value to cause a DC current having a desired current value to flow through the first conductor 3 and the second conductor 4. A DC voltage source 8 for flowing a DC current of a desired current value through the first conductor 3 and the second conductor 4 is connected to one end of the first conductor 3 and the second conductor 4, and the first conductor 3 and the second conductor 4 The other end of the two conductors 4 is short-circuited.
[0018]
FIG. 2 is a cross-sectional view of a coaxial cable according to an embodiment of the present invention. In FIG. 2, the same members as those in FIG. As shown in FIG. 2, one of the first conductor 3 and the second conductor 4 is connected to the DC voltage source 8, and the other of the first conductor 3 and the second conductor 4 is short-circuited, and the DC voltage source 8 and the first conductor are connected. 3 and the second conductor 4 form a DC closed circuit. In this DC closed circuit, a constant DC current determined by the predetermined voltage value of the DC voltage source 8 and the resistance component values of the first conductor 3 and the second conductor 4 flows.
[0019]
FIG. 3 is a diagram showing a simple experimental example for viewing the external noise blocking effect according to the embodiment of the present invention. Since the same reference numerals as those in FIG. 1 represent the same members, the description thereof is omitted. In FIG. 3, 9 is a television receiver and 10 is a television camera. Reference numeral 11 denotes a pulse noise generator. If the central conductor 2 is connected to a noise measuring circuit, the television receiver 9 may be a noise level measuring device. The first insulator on the outer periphery of the center conductor 2, the second insulator interposed between the first conductor 3 and the second conductor 4, and the third insulator outside the second conductor 4 are not shown. It is.
[0020]
As shown in FIG. 3, a constant desired current with a predetermined DC voltage value flows in the closed circuit constituted by the first conductor 3, the second conductor 4, and the DC voltage source 8. The current flowing through the first conductor 3 and the current flowing through the second conductor 4 have the same current value and are in opposite directions. The magnetic field generated by the current flowing in the first conductor 3 and the magnetic field generated by the current flowing in the second conductor 4 have the same magnetic field strength, and the magnetic field of the first conductor 3 is the same as that of the first conductor 3. Are perpendicular to the longitudinal direction of the first conductor 3 and radiate from all over the first conductor 3. The magnetic field of the second conductor 4 is perpendicular to the longitudinal direction of the second conductor 4 and radiates from everywhere in the second conductor 4. Regarding the part surrounded by the first conductor 3 and the second conductor 4, the directions of the magnetic fields are opposite to each other. Accordingly, in the portion surrounded by the first conductor 3 and the second conductor 4, the magnetic fields cancel each other, and the magnetic field is apparently zero. However, strictly speaking, it can be considered that the first conductor 3 and the second conductor 4 constantly generate magnetic fields opposite to each other and simultaneously cancel each other. Therefore, even if the magnetic field is apparently zero, the portion surrounded by the first conductor 3 and the second conductor 4 generates a very active field in which the magnetic fields always cancel each other out.
[0021]
Generally, when transmitting a video, it is necessary to provide a cable compensator every about 100 m in order to compensate for the attenuation of the video signal. Therefore, if a clear image can be transmitted to a television receiver at least 400 m away by using only the coaxial cable according to the present invention without using this cable compensator, or forced by a pulse noise generator. If the noise level is reduced in the coaxial cable of the present application in comparison with the conventional coaxial cable, the noise level of the noise level measuring instrument does not increase and the noise level of the noise level measuring instrument does not increase. You may judge that there is.
[0022]
In the experiment, first, for example, a target distance for video transmission of a coaxial cable is set, and the total length of the coaxial cable is set. In the case of this experiment, the total length of the cable was 400 m. Then, the variable DC voltage source 8 and the first conductor and the second conductor of the coaxial cable were connected in series to form a closed circuit. Next, noise was generated by the pulse noise generator 11 while transmitting the video signal of the television camera 10 to the television receiver via the coaxial cable. The DC voltage source 8 is varied to vary the value of the DC current flowing in the closed circuit in which the variable DC voltage source 8 and the first conductor and the second conductor of the coaxial cable are connected in series. By varying the voltage value of the DC voltage source 8, the DC current value in the closed circuit can be varied, and a desired current value can be found and set. In this state, the voltage level indicating the optimum state with no attenuation or disturbance of the image of the television receiver or the lowest noise level can be obtained while watching the image of the television receiver or by the noise level measuring device. I searched while measuring.
[0023]
Since the direct current value in the closed circuit is determined by the resistance component in the closed circuit, the desired current value differs depending on the value of the resistance component in the closed circuit. In determining the current value of the coaxial cable, the contribution ratio of the resistance component depending on the distance is the highest. Then, when searching for a distance of 400 m, an approximate power supply voltage value capable of flowing a desired current value was confirmed by experiments. The DC voltage value ranges from about 12V to about 24V. Therefore, in order to set the power supply voltage value for obtaining and flowing a direct current of a desired value, a direct current power supply capable of setting a direct current power supply voltage value from 10 V to 30 V is prepared at most. I knew it would be good.
[0024]
When applied to a general 6ψ 3C-5V coaxial cable, the transmission distance of a clear image without disturbance or attenuation due to noise was 500 m. In addition, the transmission distance of clear video without disturbance or attenuation due to noise in the 4ψ coaxial cable was 450 m. Therefore, in general, in the case of a coaxial cable, a distance of at least 400 m includes any influence including high-frequency noise having a steep waveform that is generated when an accelerator is suddenly depressed from an electric system of an engine such as a motorcycle. An effect of being able to block external noise is also produced. Therefore, the goal of reaching a distance of 400 m without passing through the cable compensator has been achieved with respect to transmission of a clear image free from disturbance and attenuation caused by noise in the coaxial cable.
[0025]
According to the coaxial cable of the present invention, the direct current having a predetermined voltage value between the first conductor and the second conductor so that the direct current flowing in the first conductor and the second conductor takes a desired value. Since a DC voltage source capable of applying a voltage is provided, a clear image can be transmitted over a distance of at least 400 m without interposing a cable compensator.
[0026]
FIG. 4 is a schematic view of a coaxial cable according to the second embodiment of the present invention. In FIG. 4, the same members as those in FIG. As shown in FIG. 4, 31 is a first conductor on the concentric outer periphery of the center conductor 2, 41 is a second conductor located outside the first conductor 31 on the concentric outer periphery of the center conductor 2, and 8 is the first conductor 31. This is a DC voltage source for applying a predetermined DC voltage between the first conductor 31 and the second conductor 41 and causing a DC current having a desired current value to flow through the first conductor 31 and the second conductor 41. The first insulator on the outer periphery of the central conductor 2, the second insulator interposed between the first conductor 32 and the second conductor 42, and the third insulator outside the second conductor 42 are not shown. .
[0027]
As a result of conducting an experiment similar to the above-described experiment using the coaxial cable according to the second embodiment, the same effect was obtained under the desired current value of the present embodiment.
[0028]
FIG. 5 is a schematic view of a coaxial cable according to the third embodiment of the present invention. In FIG. 5, the same members as those in FIG. As shown in FIG. 5, 32 is a plurality of first conductors on the concentric outer periphery of the center conductor 2, 42 is a plurality of second conductors located outside the first conductor on the concentric outer periphery of the center conductor 2, and 8 is the first conductor This is a DC voltage source for applying a predetermined DC voltage between the first conductor 32 and the second conductor 42 and causing a DC current of a desired current value to flow through the first conductor 32 and the second conductor 42. The first insulator on the outer periphery of the central conductor 2, the second insulator interposed between the first conductor 32 and the second conductor 42, and the third insulator outside the second conductor 42 are not shown. .
[0029]
As a result of conducting an experiment similar to the above-described experiment using the coaxial cable according to the third embodiment, the same effect was obtained under the desired current value of the third embodiment.
[0030]
FIG. 6 is a schematic view of a coaxial cable according to the fourth embodiment of the present invention. In FIG. 6, the same members as those in FIG. 33 is a first conductor wound around the concentric outer periphery of the center conductor 2, 43 is a second conductor wound around the concentric outer periphery of the center conductor 2 and outside the first conductor 33, and 8 is the first conductor 33 and the second conductor. This is a DC voltage source for applying a DC voltage between the two conductors 43 and causing a DC current of a desired current value to flow through the first conductor 33 and the second conductor 43. The first insulator on the outer periphery of the center conductor 2, the second insulator interposed between the first conductor 33 and the second conductor 43, and the third insulator outside the second conductor 43 are not shown. .
[0031]
As a result of conducting an experiment similar to the above-described experiment using the coaxial cable according to the fourth embodiment, the same effect was obtained under the desired current value of the fourth embodiment.
[0032]
FIG. 7 is a schematic view of a coaxial cable according to the fifth embodiment of the present invention. In FIG. 7, the same members as those in FIG. As shown in FIG. 7, 34 is a braided conductor outside the center conductor 2, 44 is a second conductor located outside the braided conductor 34 that is the first conductor on the concentric outer periphery of the center conductor 2, and 8 is a braided conductor 34. The DC voltage source applies a predetermined DC voltage between the second conductor 44 and the second conductor 44 so as to cause a DC current having a desired current value to flow through the braided conductor 34 and the second conductor 44. The first insulator on the outer periphery of the center conductor 2, the second insulator interposed between the braided conductor 34 and the second conductor 44, and the third insulator outside the second conductor 44 are not shown.
[0033]
As a result of conducting an experiment similar to the above-described experiment using the coaxial cable according to the fifth embodiment, the same effect was obtained under the desired current value of the fifth embodiment.
[0034]
【The invention's effect】
According to the present invention, with the configuration described above, the portion surrounded by the first conductor on the concentric circle centering on the central conductor of the coaxial cable and the second conductor on the outer side always cancels out other magnetic fields from each other. A noise barrier zone which is an active field is formed, and the noise blocking effect of the original shield itself is synergized to produce a very strong noise blocking effect. Therefore, according to the coaxial cable of the present invention, external noise can be completely shut out, cable compensators and the like for preventing attenuation of video signals can be reduced, and a simple system configuration can be realized. The video signal which is not affected by noise can be transmitted over a long distance. In addition, a great economic effect is produced.
[Brief description of the drawings]
FIG. 1 is a schematic view of a coaxial cable according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a coaxial cable according to an embodiment of the present invention.
FIG. 3 is a diagram showing a simple experimental example for seeing an external noise blocking effect according to an embodiment of the present invention.
FIG. 4 is a schematic diagram of a coaxial cable according to a second embodiment of the present invention.
FIG. 5 is a schematic diagram of a coaxial cable according to a third embodiment of the present invention.
FIG. 6 is a schematic diagram of a coaxial cable according to a fourth embodiment of the present invention.
FIG. 7 is a schematic diagram of a coaxial cable according to a fifth embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Coaxial cable 2 Center conductor 3, 31, 32, 33 1st conductor 34 1st braided conductor 4, 41, 42, 43, 44 2nd conductor 5 1st insulator 6 2nd insulator 7 3rd insulator 8 DC voltage source

Claims (7)

A first conductor is provided on the outer periphery of the center conductor via an insulator, and a second conductor is provided on the outer side of the first conductor via an insulator on a concentric circle centered on the center conductor. A voltage source capable of applying a DC voltage between the first conductor and the second conductor is provided by covering the outer side of the second conductor with an outer sheath of an insulator. Coaxial cable. A first conductor is provided on the outer periphery of the central conductor via an insulator, and a second conductor is provided on the outer side of the first conductor via an insulator on a concentric circle centered on the central conductor. The outer side of the second conductor is covered with an outer sheath of an insulator, and the first conductor and the second conductor are set so that a direct current flowing in the first conductor and the second conductor takes a desired value. A direct-current voltage source capable of applying a direct-current voltage having a predetermined voltage value is provided between the first conductor and the second conductor, and a portion surrounded by the first conductor and the second conductor A coaxial cable having a noise barrier zone formed by electromagnetic action by the desired current. The coaxial cable according to claim 1, wherein the first conductor and / or the second conductor is a braided conductor. 4. The coaxial cable according to claim 1, wherein the second conductor includes a plurality of conductors provided on an outer periphery of the first conductor via an insulator. 5. The coaxial cable according to any one of claims 1 to 3, wherein the second conductor is a conductor provided by being wound around an outer periphery of the first conductor via an insulator. The direct current voltage having a predetermined power supply voltage value is applied so that the first conductor side is a positive voltage and the second conductor side is a negative voltage, and the direct current having the desired current value is The coaxial cable according to claim 1, wherein the coaxial cable is configured to flow through the first conductor and the second conductor. The coaxial cable according to any one of claims 1 to 6, wherein a power supply voltage value of the DC voltage source is in a range of 10V to 30V.

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