JP2003304513A - Protector for cable television - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a protector for cable television for preventing an unnecessary induced radio wave from being generated and capable of miniaturizing even when the protector has a plurality of outputs. <P>SOLUTION: The protector for cable television having signal input output terminals is characterized in that at least one of the signal input output terminals is a coaxial line type plug, cylindrical conductors electrically connected to the case are arranged around the coaxial line type plug at an interval, a guide path is formed by the cylindrical conductors and the outer conductor of the coaxial line type plug, and a magnetic substance is inserted between the cylindrical conductors and the outer conductor of the coaxial line type plug. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protector for a cable television (CATV), and more specifically, noise generated in an electronic device on the subscriber side of a cable television and induced on a power line leaks to the cable television facility side. On the contrary, the present invention relates to a cable television protector used to prevent interference from the cable television facility side, noise, and abnormal voltage from entering the subscriber side.

[0002]

2. Description of the Related Art In a cable television facility, an abnormal voltage such as a lightning surge voltage generated on the facility side is prevented from flowing into the subscriber side from the facility side, and at the same time, commercial power generated from electric equipment on the subscriber side. A cable television protector is installed between each subscriber terminal and the cable television facility so that the induced current of the frequency does not flow into the facility side through the cable television drop line.

Therefore, for the above-mentioned purpose, in the protector for the cable television, the inner and outer conductors of the coaxial line are galvanically insulated from each other between the input and the output thereof. The method is to connect the inner conductor of the coaxial line by blocking the direct current with a capacitor, while the outer conductor has a gap between the outer conductor and the chassis as a method of fixing the plug on the output side, and the insulator The output connector is fixed by turning and the outer conductor is floated from the chassis in a direct current manner, and the capacitor is also used to connect to the chassis. Therefore, in this part, the electromagnetic wave propagating through the coaxial line collapses from the propagation of the general coaxial mode, and a part of the collapsed high-frequency current leaks through the gap to the outer case or outer case of the protector. It flows to and radiates from the outer surface of the outer conductor of the connected coaxial cable.

Such unnecessary radiation due to the induced current is not limited to the protector for the cable TV, but is often found in other electronic equipments. The cause is vacant in the housing of the electronic equipment. Often located in gaps or holes. Unwanted radiation due to such induced current may interfere with other equipment,
It may cause a ghost disorder.

For example, in a cable television facility, an abnormal voltage such as a lightning surge voltage generated in equipment such as a power supply for supplying power to a head end, a main line, or an amplifier,
It may flow into the subscriber side and damage electronic devices such as the television receiver of the subscriber side. In order to prevent such troubles, high frequencies such as TV signals easily flow to the subscriber terminals, but these abnormal voltages are prevented from flowing in, and at the same time, the TV side that suffers from poor insulation, especially from the subscriber side. It is also considered that the household voltage from the TV set does not flow into the cable TV facility side via the service line of the cable TV.

[0006] The frequency of the electric current from the household equipment which gives an obstacle to the cable television facility is usually 50 Hz or 60 Hz which is a normal commercial power source frequency. In addition, there are frequencies generated from the inverter equipment and the like, but at most several hundreds. Hz
In addition, although lightning surges include considerably high frequency components, the components with large energy are direct current and extremely low frequency components, so these frequencies are significantly lower than the signals handled by cable TV facilities. Therefore, it may be treated as direct current here. Further, it is said that most of the ingress noise, which is a problem in the reverse feed of the cable TV line, is at a frequency of 30 MHz or less.

[0007] Therefore, in order to prevent as much as possible a failure due to an abnormal voltage from both the cable television facility and the subscriber, a protector is usually provided between the subscriber terminal and the facility in the cable television facility. . In order to meet the above-mentioned purpose, this protector turns the capacitor and insulates it in terms of direct current so that the current of the commercial power source and the current of the lightning surge do not flow into each other between the coaxial lines on the input and output sides. It is designed so that cable TV signals can pass through without any problems.

FIG. 1 is a sectional view showing the structural concept of a conventional protector manufactured for this purpose. In the figure, 1 is an input plug, 1-1 is an inner conductor, 1-2 is an outer conductor, 2, 3
Is an output plug, 2-1, 3-1 is an internal conductor, 2-2, 3-
2 is an outer conductor, 4 is a chassis, 5 is a conductive cover, 6 is a ceramic insulator, 7 and 7'are metal films for forming an annular capacitor through 6, 8 is an insulator, 9 is a void, and 1 is a void.
0 and 11 are annular capacitors, 12 is a grounding metal, 13 is a printed circuit board, 20 is a mounting plate, 21 is a screw hole, 22
Is a ground terminal screw screwed into 20, Cs is a DC insulating capacitor, SP is a distribution circuit, FL is a high-pass filter circuit, and Ar is an arrester. 1, 2, 4, 8, and 9, the input / output connectors are arranged in a straight line to facilitate understanding of the configuration.

In the actual structure, it is considered that two or more coaxial connectors for input / output terminals are attached to the chassis 4 in the form of a short metal brown tube, and the required parts are assembled inside the tube. Good. In the case of FIG. 1, there is one input plug 1, but there are two outputs, a data signal output plug 2 and a television signal plug 3. However, the output connectors 2 and 3 are not directly attached to the bottom surface of the cylinder, but are attached in such a manner that the outer periphery is surrounded by the insulator 8 and insulated from the chassis 4. Therefore, the distance between the output connection plugs 2 and 3 is determined by the diameter of the annular capacitors 10 and 11, and cannot be made too narrow.

The input plug 1 is a coaxial line type plug, which is usually called an F type plug, and receives data signals such as multi-channel TV signals for cable TV and cable Internet from the cable TV facility side through the subscriber's lead-in coaxial line. It is for supply. In this case, the drop coaxial line is connected to the input connector 1 by means of a connector. Here, the input connector 1 is mechanically fixed to the chassis 4 of the protector body,
And it is also electrically connected. Normally, the chassis 4 is grounded by the ground terminal screw 22.

The cable television signal thus introduced into the protector flows through the inner conductor 1-1 of the input plug 1, passes through the DC insulating capacitor Cs, and then the distribution circuit S.
It is divided into two by P, and a part of the distributed signal flows into the inner conductor 2-1 of the output connector 2, and the coaxial line type connector is used as in the input connector 1, and the cable is passed through the coaxial line for the subscriber pull-in. Even data devices such as modems. Further, the television signal in the distributed signal is output to the output connector 3 through the high-pass filter circuit FL that passes 50 MHz or more, for example, and is connected to the television receiver of the subscriber.

Here, the DC component that has flowed into the protector through the outer conductor 1-2 of the input connector 1 flows through the chassis 4, but the chassis 4 is grounded, and the outer conductor 2 of the output connector 2 is also grounded. -2 is blocked by the insulators 6 and 8 surrounding the chassis 4 and the plug, and the gap 9, so that no DC component is transmitted.

Similarly, the DC component induced in the outer conductor 2-2 of the output connector 2 is also blocked from the input connector 1 and does not flow into the input side. On the other hand, the high-frequency signal from the input plug 1 has a conductive metal 7 on both sides of the ceramic insulator 6.
It flows to the outer conductor 2-2 of the output plug 2 through the annular capacitor 10 formed by providing 7 ', and reaches the equipment of the subscriber through the coaxial line using the coaxial line type plug.

The inside of the protector which operates in this way is normally shielded by the conductive cover 5 so as not to be exposed to the outside air or the radio waves propagating in the air. Although not shown, a fuse of about 3 A is connected to the capacitor Cs.
In some cases, it is inserted in series and is cut off to protect the circuit when an overcurrent flows. In addition, as shown in the drawing, there is a gap between the DC insulating capacitor Cs and the chassis 4.
In some cases, a discharge element (alester) Ar that starts discharging at about 50 V is inserted, and measures are taken to enhance safety, such as discharging when an abnormal voltage such as a lightning surge flows inside. Further, an insulating high frequency transformer may be used instead of the capacitor Cs, but the essential operation as a protector, that is, the inner conductor and the outer conductor of the coaxial line type connector are galvanically insulated between the input and the output. There is no change.

In this way, in the conventional protector, the high frequency signal in the input connector 1 can pass between the input and the output, but the abnormal voltage from the subscriber side as described above is also transmitted from the facility side. The abnormal voltage of the capacitor Cs
In addition, when it enters the outer conductor side, the annular capacitors 10 formed of the conductive metals 7 and 7'provided on both surfaces of the insulator 6 block the direct current, so that they may flow into each other. There is no. The printed circuit board 13 on which the above-mentioned electric circuit parts are arranged is connected to the ground metal fitting 12 by soldering or the like. The earth metal fitting 12 is electrically integrated with the stainless steel chassis 4.

Further, the chassis 4 is provided with a mounting plate 20 for mounting the protector on the wall surface of the house, and has a screw hole 21 for mounting on the wall surface and a ground for connecting an electric wire for grounding the mounting plate 20. Terminal screws 22 are provided.

Not only the cable television facility, but also unnecessary electronic radiation from all electronic devices and systems must be suppressed as much as possible. This is because if the equipment emits radio waves, it may interfere with other facilities, equipment, and other radio-based navigation and control systems. In addition, it means that the device that emits unnecessary radiation is easily susceptible to interference from the outside. Recent electronic devices have to be small and lightweight, as represented by mobile phones, and must also receive very weak signals in order to save power. Interference due to unnecessary radiation must be suppressed as much as possible.

[0018] This is also because, for example, in a cable television, because of unwanted waves that have penetrated into the house, malfunctions of electronic equipment, television signals distributed via the cable television facility, and direct transmission from the broadcast antenna are possible. A so-called ghost is generated on the image receiving screen of the television due to the combination with the wave, and an image of poor quality must be received.

Recently, with regard to the transmission frequency band required for cable television, with the increase in the number of channels, the cable Internet has become popular, and a wide band system of 5 to 1,000 MHz is required. In this way, when the upper limit of the frequency is used up to a higher frequency, not only the fundamental wave but also its harmonics, the frequency of the radio wave that can be emitted becomes extremely high. . This is one of the factors that make it difficult to prevent unwanted radiation from various electronic devices, and it is greatly affected by the small gaps in the device housing and the wires that are taken out from the device. However, electric wires are indispensable for supplying power to the inside of the equipment and inputting / outputting signals, and
In many cases, these wirings are formed by making holes in the equipment casing and passing them through. Therefore, it is important to prevent unwanted radiation from this hole.

FIG. 2 is a diagram for explaining in detail how the high-frequency current flows in the conventional cable television protector shown in FIG. 1, and the reference numerals of the respective parts are the same as those in FIG. Regarding the signal flow between the input plug and the output plug, the flow from the input plug 1 to the output plug 2 and the flow from the input plug 1 to the output plug 3 are equivalent. Here, only the signal relationship between the input plug 1 and the output plug 2 will be described.

In FIG. 2, the inner conductor 2- of the output connector 2 is shown.
The high frequency current output through 1 is indicated by Iiii (in this specification, the underline indicates the complex number display),
Outer conductor 2-2 of output connector 2 whose phase is 180 degrees different from that
The current flowing on the inner surface is indicated by Iio . The current flowing on the outer surface of the outer conductor 2-2 of the output plug 2 is defined as Ios .

Now, in order to study the disturbing current induced on the cable television facility side from this protector, focusing on the current Iio flowing through the outer conductor 2-2 of the output connector 2, the coaxial mode ( The current that has normally flowed through the inner surface of the outer conductor 2-2 of the output plug 2 as the current of TEM) reaches the position of the annular capacitor 10, and the current Ioc that flows through the annular capacitor 10 to the chassis and the annular capacitor A current Ios that flows through the conductive metal 7 of 10 and further through the insulator 6 and the gap 9 to the outer wall of the outer conductor 2-2 of the output connector 2. That is, Iio = Ioc +
Ios , but the ratio is the outer conductor 2-of the output connector 2.
2 is determined by the impedance on the outer wall side and the impedance of the capacitor 10. Generally, since the impedance of the capacitor 10 is high at the lower frequency of the band of the cable TV, it is considered that the amount of Ios is larger than that at the higher frequency. In a cable TV facility, it depends on the impedance of the outer wall of the plug, so it is considered that the frequency varies greatly with the length of the coaxial line connected to the output plug.

Here, the current Ioc toward the input side is
The current Ioo flowing through the inner surface of the outer conductor 1-2 of the input plug 1 at the end surface of the input plug 1 on the inner side of the protector flows to the cable television facility side. That is, when viewed from the input-output 1-2, if the current Ios flowing through the outer wall of the outer conductor 2-2 of the output connector 2 is large, the loss between the input and the output is increased.

Further, Ios can be replaced with a surge voltage or an interfering radio wave induced in the outer conductor of the output cable.
In this case, if Ios is noise, the current Ioo flowing to the input side flows as noise to the head end,
Further, the Iio flowing due to the noise Ios can be said to be noise affecting the subscriber.

In the above description, the current from the output to the input has been described. However, due to the reversible reason, the current Ioo flowing through the inner surface of the outer conductor 1-2 of the input plug 1 follows the reverse path. Means to flow through the outer wall of the outer conductor 2-2 of the output connector 2 and radiate. That is, the current Io flowing through the inner surface of the outer conductor 1-2 of the input connector 1 of the input signal of the protector
Part of o becomes Ios , flows on the surface of the outer conductor 2-2 of the output connector 2 of the protector, and is radiated into the space by using the surface of the outer conductor of the service wire connected to it as an antenna. is there. Then, between the input and output, this Ios becomes a loss.

FIG. 3 shows an example of the actual value of the leakage amount described above in the case of the conventional protector shown in FIG. 3, the horizontal axis represents the frequency of the interfering wave induced outside the outer conductor 2-2 of the output connector 2, and the vertical axis represents the transmission amount when the level of the induced interfering wave is 0 dB. . Where I
The curve of N is the amount of the induced interference wave transmitted to the input side,
The OUT curve shows the amount of the induced interference wave transmitted to the output side.

It is clear from FIG. 3 that the interfering wave induced outside the outer conductor 2-2 of the output connector 2 passes through the gap of the annular capacitor 10 and is -80 dB to -6 compared to the induced amount.
A quantity of 0 dB is transmitted on the input side. In addition, on the output side, it passes through the gap of the annular capacitor 10,
About dB is transmitted. At the same time, this means that the input wave is at a level of -80 dB to -60 dB relative to its level, and the level of noise generated by the subscriber side being sent back to the output end. It means that the outside of the cable outer conductor is used as an antenna and is radiated in the form of unnecessary radiation at a level of approximately -40 dB.

On the other hand, Japanese Unexamined Patent Publication No. 9-283969 discloses a coaxial conductor (plug) which has inner and outer conductors, is provided so as to penetrate a chassis of electronic equipment, and is electrically insulated from the chassis. , Connected to the outer conductor of the coaxial conductor,
A conductor disk that is arranged substantially parallel to the chassis and forms a space between the chassis and the coaxial conductor so as to concentrically surround the coaxial conductor; and a conductor disk that is formed of ferrite and that is inserted in the space and is concentric with the coaxial conductor. A cable television protector having a magnetic material arranged therein has been proposed.

In the invention described in the above publication, the leakage current that causes the leakage radiation from the gap provided in the housing is guided to the waveguide to be processed, so that the leakage radiation can be effectively prevented.

However, in the technique disclosed in this publication, the conductor disc for forming the waveguide for containing the ferrite disc, which is an element for absorbing leaked radio waves, is arranged in parallel with the chassis. In a protector with multiple output terminals, the distance between adjacent output terminals must be at least as large as the radius of the disc of the waveguide, which naturally increases the chassis of the protector. As a result, the overall shape of the protector was enlarged, and there was room for further improvement in terms of downsizing the protector.

[0031]

SUMMARY OF THE INVENTION The present invention solves the problems of the prior art as described above, prevents the generation of the above-mentioned induced noise and interfering radio waves, the inflow of abnormal voltage, and the security of a plurality of outputs. It is an object of the present invention to provide a protector for a cable television, which can have a small shape even in the case of a device.

[0032]

The above problems can be solved by the following technical means. (1) In a cable television security device having a signal input / output terminal, at least one of the signal input / output terminals is a coaxial line type connector, and the coaxial line type connector is electrically connected to a housing. The connected tubular conductors are arranged apart from each other, and a waveguide is formed by the tubular conductor and the outer conductor of the coaxial line type connector, and the tubular conductor and the outer conductor of the coaxial line type connector are formed. A protector for a cable TV, characterized in that a magnetic material is inserted between them. (2) In a cable television security device having a signal input / output terminal, at least one of the signal input / output terminals is a coaxial line type plug, and the coaxial line type plug is electrically connected to the housing. The connected tubular conductors are arranged apart from each other, and a waveguide is formed by the tubular conductor and the outer conductor of the coaxial line type connector, and the tubular conductor and the outer conductor of the coaxial line type connector are formed. A cable television protector characterized in that a dielectric and a magnetic material are inserted between them. (3) A void or a dielectric is inserted between the outer conductor of the coaxial line type connector and the magnetic body and / or between the tubular conductor and the magnetic body. A protector for a cable television as described in (2) above. (4) Any one of the above (1) to (3), wherein an electric capacity is added between the coaxial line type plug and the housing or between the coaxial line type plug and the chassis. The cable TV protector described in.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below. In the present invention, in order to eliminate the above-mentioned unnecessary induced radio waves, a waveguide is provided by using the outer circumference of the output connector of the cable TV protector, and a means for preventing unnecessary radiation is used. According to the present invention, when the outer conductor of the connector needs to be DC-floated from the housing like the output plug of the cable television protector described above with reference to FIGS. First, to prevent unwanted radio waves (noise) from entering through a gap provided in the housing or radiating unwanted radiation, flowing into the facility as noise or radiating signals from the facility. Guide to the waveguide and process.

Since the waveguide has a structure in which all the interfering waves induced in the service line are guided into the waveguide, the conductive sleeve (cylindrical conductor) continuously extending from the chassis to the outside of the housing and the output are provided. Consists of a coaxial line type plug. Therefore, in the conventional protector using the annular capacitor, when the output has two or more terminals, the output terminal interval is determined by the diameter of the annular capacitor, so the interval is widened and the size of the entire protector is reduced. It was difficult to do this, but by using a waveguide, the distance between the output terminals can be narrowed and the overall size can be reduced.

The tip of the sleeve of the waveguide is short-circuited to the chassis in terms of high frequency, and inside the waveguide,
Dielectric or magnetic material is inserted. In the cable television protector of the present invention thus configured, the interfering radio waves induced in the service wire and the high frequency current leaking from the gap in the chassis are absorbed by the magnetic material while propagating in the waveguide. ,
You can prevent it from propagating further. As the dielectric used in the present invention, a ceramic having a high dielectric constant is preferably used, and specific examples thereof include a high dielectric such as titanate valium. Examples of the magnetic material used in the present invention include nickel-zinc (NiZn) -based and manganese-zinc (MnZn) -based ferrite magnetic materials. Among these, the NiZn ferrite magnetic material is particularly preferable.

Conventionally, as a method for preventing unwanted radio waves entering or emitting from the outside of the housing, a method of inserting a choke coil in series with an electric wire, a method of inserting a capacitor between an electric wire and a chassis, and a method of inserting a filter. However, these methods are effective for high-frequency currents superposed on electric wires, but cannot directly prevent radiation from holes or gaps. Also, in these methods, the interference wave superposed on the electric wire is reflected by either high impedance or short circuit to prevent it from invading beyond, so the reflected interference wave is re-radiated. There was a risk that it could interfere with unexpected equipment.

On the other hand, unlike the above methods, the present invention uses the method of electromagnetic wave absorption by minimizing the opening area of the gap involved in the entry of unwanted radiation or unwanted waves, and the method of absorbing the radio wave is used. It is very effective against unwanted radiation and there is no risk of secondary interference. Further, in the cable television protector of the present invention, a gap is provided between the magnetic body to be inserted into the waveguide and the inner surface of the waveguide, so that the induction of radio waves over a wider band than in the case without this gap. Can be prevented. Further, as a method of short-circuiting the tip of the waveguide at a high frequency, it is possible to bring the tip portion of the waveguide close to the chassis to form a distributed capacitance, or another method is to use a concentrated component.

An example of the structure of the cable television protector according to the present invention is shown in FIG. 4 and its basic operation will be described below. 4, the same elements as those in FIG. 1 are designated by the same reference numerals. A cable television protector of this configuration example shown in FIG. 4,
The structural difference from the conventional protector shown in FIG. 1 is that in this structural example, a waveguide 14 extending in the axial direction is provided by using the outer circumference of the output connector, and a ferrite is provided in the waveguide 14. The arrangement of the magnetic body 15 and the waveguide 1 extending in the axial direction
That is, the capacitance portion 18 is provided at the tip portion of No. 4. Note that FIG.
In the above, the description of the output end 3 will be omitted because it has the same mechanism as the output end 2.

The waveguide 14 is composed of the outer conductor 2-2 of the coaxial line type output connector 2 and the sleeve (cylindrical conductor) 17. Specifically, the outer conductor 2-2 of the output connector 2 and the sleeve 17, which form the waveguide 14, are positioned substantially coaxially.
Inside the waveguide 14, that is, the output connector 2 and the sleeve 1
A ring 15 of ferrite magnetic material (hereinafter, also referred to as a ferrite ring) is provided between the outer conductor 2 and the outer conductor 2 of the output connector 2.
-2 is inserted so as to surround it. Further waveguide 1
A metal ring 16 is arranged at the tip of 4 (inside the protector) so as to be in electrical contact with the outer conductor 2-2, and the metal ring 16 and the sleeve 17 have a very small gap. The capacitance section 18 is configured. FIG. 5 shows an equivalent circuit for explaining the operation of the thus-configured cable television protector of the present configuration example.

In FIG. 5, to simplify the discussion, FIG.
The output plug 2 is shown in a sectional view. In FIG. 4, such a waveguide surrounds the outer circumference of the output plug. In FIG. 5, Ios is the leakage current from the gap between the chassis and the outer circumference of the coaxial plug described in FIG. 2, which is replaced by the current from one power source P.

Here, the characteristic impedance Zc of the waveguide 14 formed by the sleeve 17 and the outer conductor 2-2 has a gap go between the ferrite ring 15 and the sleeve 17, and the ferrite ring 15 and the outer conductor 2-2. Gap gi
In this case, if the outer diameter of the outer conductor 2-2 is Di and the inner diameter of the sleeve 17 is Do, the following expression (1) is given.

[Equation 1] Here, L = L1 + L2 + L3 C = 1 / C1 + 1 / C2 + 1 / C3, and L1 = (μ0 / 2π) · ln {(Di + 2gi) / (D
i)} L2 = (μ0 μr / 2π) · ln {(Do-2go) /
(Di + 2gi)} L3 = (μ0 / 2π) · ln {(Do) / (Do-2g
o)} μ0 = 4π × 10 ^ −7 (H / m) Further, C1 to C3 are represented by (Equation 2). (^ Represents a power, and so on)

[Equation 2] It can be expressed by ε0 = 8.854 × 10̂-12 (F / m). Further, μ0 and ε0 are the magnetic permeability and permittivity of air, respectively, and μr and εr are the relative permeability and relative permittivity of the ferrite ring 15, respectively.

Further, the capacitance portion 1 connected to the tip of the waveguide.
The capacity of 8 is Dso for the inner diameter of the sleeve 17, Dci for the outer diameter of the ring 16 attached to the coaxial line type connector, and sleeve 1
7 The distance between the inner diameter and the outer diameter of the ring 16 is dc, and the space between them is filled with the relative permittivity εc, and the length of the capacitance portion is lc.
Then, C is represented by the following formula (2).

[Equation 3] However, Dso = 2dc + Dci. Therefore, dc
A large capacitance can be obtained by making ε small and εc large.

On the other hand, regarding the capacitance of the annular capacitor as shown in FIG. 1, it is assumed that the outer diameter of the conductor portion is Do, the inner diameter is Di, the thickness of the insulator is dc, and the space between them is filled with the dielectric constant εc. Is represented by the following formula (3).

[Equation 4] For example, Do = 30 mm, Di = 10 mm, dc = 3 m
When m and εc = 3000, the capacity is about 55.
It will be about 60 PF.

From the above equations (2) and (3), if the thicknesses dc of the insulators are the same and the capacitances of the two are made equal, the relationship of the following equation (4) is obtained.

[Equation 5] That is, the length of the tubular capacitor in the waveguide can be made equal to the capacity of the annular capacitor by determining the length according to the equation (4). For example, with a ring capacitor Do =
30 mm, Di = 10 mm, dc = 3 mm, εc = 30
The length lc that is equal to the capacity in the case of 00 is approximately 1
It will be about 5.7 mm.

Generally, the relative permeability μr and the relative permittivity ε of a magnetic material are
r can be represented by a complex number as in the following formula (5) and has a frequency dispersion characteristic.

[Equation 6] Here, Myuaru1 the real component of relative magnetic permeability μr, μr2 represents an imaginary number component, .epsilon.r1 the real component of the relative dielectric constant .epsilon.r, the εr2 shows imaginary component. For example, the relative permeability of the NiZn-based sintered ferrite material itself is 100 K
In the value measured in Hz, the value of μr1 in the equation (5) is μr1.
= 10 to 2,500 is obtained, and the value of μr2 is also
Generally, if μr1 is large, it is large, but in any case, both values change depending on the frequency. Of the relative permittivity of NiZn sintered ferrite material,
The value of εr1 is about 10 to 15 depending on the material, and may be regarded as substantially constant with respect to frequency. The value of εr2 is usually very small.

In the following description, the expressions of relative permeability and relative permittivity respectively represent the real part of the equation (5), that is, μr1 and εr1, and unless otherwise specified, 1
It is a measured value at 00 KHz. Naturally, the equivalent relative permeability μer and εer calculated based on these also have frequency dispersion.

Based on these conditions, the impedance seen from the current source P of FIG. 5 to the magnetic material side is normalized by Zc ,
When the value is Zd , it is obtained as the following formula (6).

[Equation 7] Where γ is the propagation constant of the medium, and γ = jω√ (μr · ε
In r), ω is the angular frequency. Further, Zl is a load impedance, and in this case, it is represented by the capacitance at the tip, that is, the above equation (2).

If this Zc is 1, the leakage current Io
s propagates through the waveguide 14 without reflection,
It is absorbed inside and converted into heat by the magnetic loss of the ferrite magnetic body, so it is not leaked and radiated to the outside of the housing.

In the cable television protector of this configuration example, the thickness of the ferrite ring 15 inserted in the waveguide 14 needs to be the same from the side closer to the chassis 4 of the housing to the capacitance section 18. Absent. Rather, by gradually increasing the thickness from the thickness closer to the plug to the edge of the chassis, and stacking it in multiple stages,
That is, it is possible to make the absorption frequency in a wide band rather than forming the same thickness.

By the way, when an interfering wave invades through a gap in the chassis of the cable television protector or, on the contrary, performs unnecessary radiation, it is considered that the amount is determined by the impedance looking into the housing through the gap. Generally, it is considered that the larger the gap, the larger the amount.

Here, since the gap (opening area) related to the radio wave leakage of the CATV protector shown in FIG. 1 using the ring-shaped capacitor can be considered as the area of the insulator between the conductors of the capacitor 10, the area is defined as follows. Sd is represented by the following formula (7).

[Equation 8] For example, in the case of Do = 30 mm and dc = 3 mm shown above, Sd = 282.7 mm ^ 2.

On the other hand, in the cable television protector of this configuration example shown in FIG. 4, the gap (opening area) involved in radio wave leakage is considered to be the area formed by the inner wall of the sleeve 17 and the outer wall of the metal ring 16. Therefore, assuming that area is Ss, Ss is expressed by the following equation (8).

[Equation 9] Here, since Do = Di + 2dc, the following formula (9)
Is obtained.

[Equation 10] For example, as shown above, Dci = 10 mm, dc = 3 mm
Then, Ss = 125.5mm ^ 2, and when the same thickness is obtained with the same thickness of the insulator, the opening area is greatly different between the ring type capacitor and the waveguide type capacitor. Becomes smaller.

That is, in the conventional cable television protector shown in FIG. 1, if the capacity of the annular capacitor is increased, the outer diameter of the annular capacitor must be increased, and therefore the opening is increased. In the cable television protector according to the present invention, the length lc of the waveguide 14 is lengthened even though the area is increased and unnecessary waves are radiated or penetrated much. The opening area related to unwanted radiation can be made constant by varying the inner diameter of the sleeve 17 and the outer diameter of the ring 16,
The opening area can be greatly reduced compared to a ring capacitor.

[0054]

EXAMPLES The present invention will be described in more detail with reference to examples.

(Embodiment 1) An embodiment of the cable television protector according to the present invention has the structure shown in FIG.
In FIG. 4, the chassis 4 is a stainless steel cylinder having a thickness of 0.8 mm and a diameter of about 60 mm, and an outer diameter of about 10 mm.
The output connectors 2 and 3 of the high-frequency connector are arranged apart from each other by about 30 mm. The input plug 1 is directly attached to the chassis 4 at a distance of 24 mm from the output plug 2. A sleeve 17 squeezed from the chassis 4 is surrounded by the output plugs 2 and 3 by the outer conductors 2-2 and 3-2 to form the waveguide 1.
It is provided to compose 4 and its diameter is 20.0 m.
In m, the distance d between the outer conductors 2-2 and 3-2 is set to 5 mm. Furthermore, the length lc is 15.7 m at its tip.
The m capacity part 18 is concentric with the output connectors 2 and 3.
In the capacity portion 18, the distance dc from the sleeve 17 is 3 m.
Since it is m, the outer diameter of the outer conductors 2-2 and 3-2 is 14.0 m.
The length of the metal ring 16 having an inner diameter of 10.0 mm and a length of 15.7
Mounted in the range of mm, metal ring 16 and sleeve 17
The space is filled with titanic acid valueme with a relative dielectric constant of 3000. Therefore, the capacity of the capacity unit 18 is about 5600.
0 pF is obtained. The material of the ferrite ring 15 is N
The iZn-based sintered ferrite has a relative magnetic permeability μr of 2,100 and a relative dielectric constant εr of 14. Waveguide 14
The ferrite ring 15 inserted inside has a thickness tm of 4
mm, the outer diameter is 19.0 mm, and a hole of about 11.0 mm is formed at the center. The height lm of the ferrite ring 15 is 8.0 mm. Also, the ferrite ring 15
Between the inner surface of the sleeve 17 and the inner surface of the sleeve 17, and between the ferrite ring 15 and the outer conductors 2-2 and 3-2.
There are gaps go and gi of 5 mm. An insulator 19 for fixing the capacity portion 18 and the sleeve 17 is arranged inside the chassis 4 and fixed by a nut. With this structure,
The equivalent relative permeability μer in the waveguide 14 is about 1,650,
The equivalent relative permittivity εer is about 3. because there are gaps go and gi.
It is as low as 9. The reflection characteristic of the cable television protector according to the present embodiment thus constructed is as shown in FIG. Attenuation 2
Cover 0 dB or more in the range of 30 to 2,500 MHz
is doing. Further, when the measured value of the radiation amount from the cable television protector of this embodiment is shown in comparison with the radiation amount from the conventional cable television protector shown in FIG. 3, it is as shown in FIG. It becomes 10d at 5-50MHz at low frequency
Improvement of B or more is seen, 100 MHz to 1000 MHz
Shows that at high frequencies, it is improved by 25 dB or more.

(Embodiment 2) FIG. 8 shows another embodiment of the cable television protector according to the present invention. In FIG.
Elements similar to those are labeled with similar reference numerals. In this embodiment, the capacitance section 18 shown in the first embodiment is replaced with the fixed capacitor 1.
It is replaced by 8 '. In FIG. 8, the chassis 4 is a stainless steel cylinder having a thickness of 0.8 mm and a diameter of about 60 mm, and output connectors 2 and 3 of high-frequency connectors having an outer diameter of about 10 mm are arranged at a distance of about 30 mm from each other. The input plug 1 is directly attached to the chassis 4 at a distance of 24 mm from the output plug. A sleeve 17 squeezed from the chassis 4 is provided around the output connectors 2 and 3 coaxially with the output connectors 2 and 3 to form the waveguide 14 with the outer conductors 2-2 and 3-2. Its diameter is 20.0 mm. Therefore, the distance d between the outer walls of the outer conductors 2-2 and 3-2 and the inner wall of the sleeve 17 is set to 5 mm. Further, four ceramic capacitors 18 ′ are connected to the chassis 4 at one end thereof at substantially equal intervals around the outer wall tips of the outer conductors 2-2 and 3-2. Therefore, the total capacitance of the capacitance section 18 'is set to about 4000 pF.
By doing so, the length lc of the capacitance portion 18 between the sleeve 17 and the outer conductors 2-2 and 3-2 in the first embodiment can be omitted, so that the length of 17 is only the ferrite portion as compared with the first embodiment. It is good and can be shortened. The material of the ferrite ring 15 is NiZn-based sintered ferrite, and its relative magnetic permeability μr is 2,100 and its relative dielectric constant εr is 14. Ferrite ring 15 inserted in the waveguide 14
Has a thickness tm of 4 mm, an outer diameter of 19.0 mm, and a central portion of 1
There is a 1.0 mm hole. The height lm of the ferrite ring 15 is 8.0 mm. In addition, between the ferrite ring 15 and the inner surface of the sleeve 17, and between the ferrite ring 15 and the outer conductors 2-2, 3-2,
There is a gap of 0.5 mm each. In the case of this structure, the equivalent relative permeability μer in the waveguide 14 is about 1,650, and the equivalent relative permittivity εer is about 3.9 because of the gaps go and gi.
It is as low as 0. The absorption characteristic of the cable television protector according to the present embodiment thus constructed is that power is supplied between the outer conductors 2-2 and 3-2 and the sleeve 17 as shown in FIG. With respect to the electromagnetic wave propagating in the direction of, the reflection characteristic covers a return loss of 20 dB or more in the range of 30 to 2,500 MHz,
The characteristics thereof are substantially the same as those shown in FIG.

(Embodiment 3) FIG. 9 shows still another embodiment of the cable television protector according to the present invention. 9, the same elements as those in FIG. 4 are designated by the same reference numerals. Note that FIG. 10 shows the details of one output terminal. Also in this embodiment, a fixed capacitor is used for the capacitance section shown in the first embodiment as shown in the second embodiment. In FIG. 9, the chassis 4 has a thickness of 0.8 mm and a diameter of about 60 mm.
In a stainless steel cylinder of mm, output connectors 2 and 3 of high-frequency connector having an outer diameter of about 10 mm are arranged apart from each other by about 30 mm. The input plug 1 is 24m from the output plug.
Mounted directly on the chassis at a distance of m. Around the output connectors 2 and 3, the outer conductors 2-2 and 3-2 and the waveguide 14 are provided.
The sleeve 1 squeezed from the chassis 4 to configure the
7 is provided, the diameter of which is 20.0 mm, and the outer conductor 2
-The distance d between the outer wall of 2-3 and the inner wall of the sleeve 17 is 5 m
It is set to m. Further, four so-called ceramic capacitors 18 'are connected between the output connectors 2 and 3 and the chassis 4 at substantially equal intervals around the tip end thereof, and the total capacitance is about 4000 pF. In FIG. 9, a ferrite ring 15-1 having a thickness tm1 and a thickness tm2 and a ferrite ring 15 having a different thickness are inserted in the waveguide 14, and the ferrite ring 15-1 near the tip has a thickness larger than that of the ferrite ring 15-2. Is thinning. Also, regarding the length of the ferrite ring, the height of 15-1 lm1 and 15
The height lm2 of -2 is different. The present embodiment is a case suitable for a cable television protector having a wider frequency band than the second embodiment. In FIG. 9, the ferrite ring 1
The materials 5-1 and 15-2 are the same NiZn-based sintered ferrite, the relative permeability μr of which is 2,100, and the relative permittivity εr of which is 14.
1, the thickness tm1 is 3.0 mm, the outer diameter is 18.0 mm, the inner diameter is 12.0 mm, and the height lm is 6.0 mm, and the ring shape is arranged in the waveguide 14 with a gap of 1.0 mm from the inner wall of the sleeve 17. ing. At this time, there is also a gap of 1.0 mm between the output connectors 2 and 3. In the ferrite ring 15-2, the thickness tm2 is 5.0 mm, the outer diameter is 20.0 mm, the inner diameter is 10.0 mm, and the height lm2 is 4.
The distance between the sleeve 17 and the outer conductors 2-2, 3-2 is set to 0 mm. In the case of this structure, the equivalent relative permeability μer of the ferrite magnetic body 15-1 in the waveguide 14 is reduced to about 1230 due to the gap, and the equivalent relative permittivity εe
r is about 2.23, and the ferrite magnetic material 15-
The equivalent relative permeability μer of the portion 2 is the same as the relative permeability of the material because there is no gap, and is 2,100, and the equivalent relative permittivity εer
Is 14.0 for the same reason. The absorption characteristics in the waveguide portion of the cable television protector of the present embodiment thus constructed are shown in FIG.
-2, 3-2, and the sleeve 17 are fed with electric power, and the capacitor section 1 passes through the two-stage ferrite rings 15-1, 15-2.
As shown in FIG. 11, with respect to the electromagnetic wave propagating in the 8 ′ direction, the return loss showing the absorption characteristic is −8 at 5 MHz.
-13 dB at 10 MHz, 27 to 5000 MHz
Shows a very wide band characteristic of -22 dB or less. This covers not only frequencies used in cable TV but also microwave frequencies, mobile phone frequencies, and bluetooth frequency bands. It shows that it covers the frequency band that is absorbed even if induced in the outer conductor of the main line.

Although the present invention has been described based on the embodiments, the present invention is not limited to these embodiments, and various modifications and changes can be made. For example, the first embodiment shown above,
In Nos. 2 and 3, sintered ferrite is used as the magnetic material, but a magnetic material in which ferrite powder is mixed with plastic can also be used depending on the frequency band for preventing induction. However, generally, by increasing the equivalent magnetic permeability, the blocking ability can be obtained from a low frequency, and the width of the magnetic body can be narrowed. Further, in Example 3, the equivalent magnetic permeability of the first stage is set to about 1,260, which is lower than that of the second stage. In the case of such a multi-stage configuration, the equivalent magnetic permeability of the first stage is
By making the thickness smaller than the first step, the operable frequency becomes higher than that when the thickness of the magnetic material is made constant in the waveguide. A wider band CATV protector can be constructed by increasing the equivalent magnetic permeability in such a manner that the second step is closer to the second step, the second step is the third step, and so on. Further, in the above description, the coaxial line type plug, the ferrite ring, and the like are described as having a circular shape, but it is not necessary to limit the shape to a circular shape, and other shapes may be used. Further, in order to further reduce the shape of the cable television protector of the present invention, a fixed capacitor may be arranged on the outer periphery of the coaxial line type connector instead of the high dielectric constant material inserted in the capacitor portion. further,
In the embodiment of the present invention, one input plug and two output plugs are shown as examples, but one input plug and one output plug may be used, and a plurality of combinations other than the above may be used. The present invention can be applied to the input / output plug, and the same effect can be obtained. Although the input plug 1 and the output plugs 2 and 3 are shown in plan in FIGS. 4, 8 and 9, they are actually arranged in substantially triangular positions as shown in FIG.

[0059]

As described above in detail, according to the present invention, the cylindrical conductor (sleeve) is arranged around the coaxial line type plug so as to be spaced apart from the outer conductor of the coaxial line type plug and the cylindrical shape. Since a waveguide extending in the axial direction is formed by the conductor and a magnetic substance such as ferrite or a magnetic substance and a dielectric substance are inserted between the outer conductor of the coaxial line type connector and the tubular conductor, the coaxial line Even if the interfering wave induced in the outer conductor of the mold connector enters through the gap between the chassis and the coaxial line connector, it can be prevented from further entering by blocking and absorbing it.
It is also possible to prevent unnecessary radiation leaking through the gap between the chassis and the coaxial line type stopper from the inside of the cable television protector. Moreover, since the waveguide is formed so as to extend in the axial direction, it is sufficient to increase the length of the waveguide even when the capacitance is increased, and the aperture area related to unwanted radiation can be significantly reduced. You can do it.

[Brief description of drawings]

FIG. 1 is a structural conceptual diagram of a conventional cable television protector.

FIG. 2 is a diagram for explaining a current state of the conventional cable television protector shown in FIG.

FIG. 3 is a diagram showing measured values of unwanted radiation of a conventional cable television protector.

FIG. 4 is a structural example (example) of a CATV protector of the present invention.
Figure explaining

FIG. 5 is a diagram for explaining unnecessary wave absorption in the waveguide of the configuration example (embodiment) of FIG. 4;

6 is an actual measurement diagram of the reflection characteristic of the embodiment of FIG.

FIG. 7 is a diagram showing unnecessary radiation characteristics of the embodiment of FIG.

FIG. 8 is a diagram showing another embodiment of the cable television protector according to the present invention.

FIG. 9 is a view showing still another embodiment of the cable television protector according to the present invention.

FIG. 10 is a diagram for explaining unnecessary wave absorption in the waveguide according to the embodiment of the present invention.

11 is a diagram showing the reflection characteristics of the embodiment shown in FIG.

FIG. 12 is a diagram showing an actual arrangement of input connectors and output connectors.

[Explanation of symbols]

1 input plug 1-1 Inner conductor 1-2 Outer conductor 2 output plug 2-1 Inner conductor 2-2 Outer conductor 3 output conductors 3-1 Inner conductor 3-2 Outer conductor 4 chassis 8 insulation 12 Earth metal fittings 13 printed circuit boards 14 Waveguide 15 Ferrite ring 16 metal ring 17 Sleeve (cylindrical conductor) 18, 18 'capacity part 19 Insulator P current source

Claims (4)

[Claims] 1. A cable television protector having a signal input / output terminal, wherein at least one of the signal input / output terminals is a coaxial line type connector, and a housing and an electric device are provided around the coaxial line type connector. Tubular conductors that are electrically connected to each other are separated from each other, and a waveguide is formed by the tubular conductor and the outer conductor of the coaxial line type plug, and the tubular conductor and the outer conductor of the coaxial line type plug A protector for a cable TV, in which a magnetic material is inserted between and. 2. A cable television protector having a signal input / output terminal, wherein at least one of the signal input / output terminals is a coaxial line type connector, and a housing and an electric device are provided around the coaxial line type connector. Tubular conductors that are electrically connected to each other are separated from each other, and a waveguide is formed by the tubular conductor and the outer conductor of the coaxial line type plug, and the tubular conductor and the outer conductor of the coaxial line type plug A cable television protector characterized in that a dielectric and a magnetic material are inserted between and. 3. An air gap or a dielectric is inserted between the outer conductor of the coaxial line type connector and the magnetic body, and / or between the cylindrical conductor and the magnetic body. The cable television protector according to claim 2. 4. An electric capacity is added between the coaxial line type plug and the housing or between the coaxial line type plug and the chassis. The protector for the cable TV described.