JPH0554234B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides a coaxial cable that is installed between a coaxial cable that transmits high-frequency signals such as CATV and a signal input section of a television receiver, cuts off abnormal voltage, and transmits high-frequency signals. The present invention relates to a protector that transmits signals without loss and prevents leakage of high-frequency signals.

[Prior Art and Its Disadvantages] Conventional protectors have been designed to block abnormal voltages such as those caused by lightning and to transmit high-frequency signals, but little consideration has been given to the leakage of high-frequency signals. However, in urban CATV and CATV in strong electric field areas, the amplification output has been increased to overcome external interference waves, and high-level high-frequency signals have been transmitted. Conventional protectors have high-pass characteristics, and the outer conductors of the connectors on the input and output sides of the coaxial cable are not installed in the same metal case, but are held through an insulator. Therefore, there was a drawback that high frequency signals leaked from this part and caused interference to others.

[Object of the Invention] The present invention has been made in view of the above-mentioned circumstances, and aims to prevent leakage while allowing high frequency signals to pass between the input side plug and the output side plug without passing direct current. Another purpose is to provide a safety device that can prevent

[Summary of the Invention] The present invention adds a ferrite element (hereinafter also referred to as a "transformer") in which two insulated wires are wound between an input side plug and an output side plug. The primary side is connected to the internal conductor and external conductor of the input side plug, respectively, and the secondary side is connected to the internal conductor and external conductor of the output side plug, respectively, and the external conductor of the output side plug is connected to the ground. A capacitor is inserted between the main body of the protector and the metal case.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings.

Figure 1 shows the circuit configuration, where 1 is the input side plug, 1a and 1b are the respective internal conductors and external conductors, and similarly 2 is the external side plug, 2a and 2b.
are the inner and outer conductors, respectively. The external conductor 1b of the input side plug 1 is directly fixed and connected to the metal case 3 of the main body of the protector, and this metal case 3 is grounded via the earth line 4. Further, the external conductor 2b of the output side plug 2 is connected to the metal case 3 via a grounding capacitor 5 at high frequency. A lightning arrester 6 is connected between the internal conductor 1a of the input side plug 1 and the metal case.

The primary side of a transformer 7 made up of two wires wound around ferrite is connected between the internal conductor 1a and the external conductor 1b of the input side plug 1, and the secondary side of the transformer 7 is connected to the inside of the output side plug 2. It is connected between the conductor 2a and the outer conductor 2b. Furthermore, a matching capacitor 8 is connected to the secondary side of the transformer 7.

As described above, the metal case 3 is connected to the ground line 4 to ground abnormal voltage.

The input side named above is a convenient name for the side where abnormal voltage occurs, and is generally connected to the CATV coaxial cable side, and conversely, the output side is connected to the TV receiver in the home. , has reversibility for high frequency signals.

Next, FIG. 2 shows its cross-sectional structure. The input side plug 1 is directly fixed to the metal case 3 with an input side plug tightening nut 11. Further, the output side plug 2 is insulated from the metal case 3 via an insulator 12, and is further fixed with an output side plug tightening nut 13 so as not to rotate mechanically. The grounding capacitor 5 has a lead wire as short as possible, and a plurality of large-capacity feed-through capacitors or ceramic capacitors are arranged at intervals. Capacitors 5 and 8 all have a withstand voltage
A voltage of 500V or higher is used, and a matching capacitor of 8
is 5 [pF], and the ground capacitor 5 is 2200
Four [pF] ones are used. Then, the entire circuit described above is covered with the metal cover 14.

In the protector configured as above,
The high frequency signal used for CATV is the input connector 1.
is transmitted to the internal conductor 1a of the transformer 7,
It is transmitted to the internal conductor 2a of the output side plug 2. On the other hand, the external conductor 1b of the input side plug 1 and the output side plug 2
The high frequency signal is conducted between the external conductor 2b and the metal case 3 and the grounded capacitor 5.

When an abnormal voltage due to a lightning strike or an electric leak is applied to the inner conductor 1a and outer conductor 1b of the input side plug 1, the transformer 7 short-circuits them and the voltage drops. The high voltage with the steep waveform at this time is short-circuited by the lightning arrester 6, and the voltage drops. On the other hand, the output side plug 2 is insulated by the transformer 7, and no abnormal voltage is transmitted.

In addition, when a voltage is applied to the external conductor 1b of the input side connector 1 and the ground line 4, the external conductor 2b of the output side connector 2 is in a DC-blocked state by the grounding capacitor 5, so the abnormal voltage is also applied. is not transmitted and protects the television receiver connected to the output connector 2.

Next, even if an abnormal voltage occurs on the output side, such as a reverse flash during a lightning strike, or if the TV receiver malfunctions and abnormal voltage is applied from the receiver to the output side plug 2, the DC blocking Because the grounding capacitor 5 is interposed, abnormal voltage is not transmitted to the input connector 1, and the CATV circuit can be protected.

Next, an example of the configuration of the transformer 7, which is the main part of the present invention, is shown in FIG.

FIG. 3a shows a short ferrite rod in which two sets of insulated conducting wires 72 and 73 are wound around a spectacle-shaped ferrite 71 with two holes bored in the axial direction.
In FIG. 3b, a pair of insulated conductive wires 75 and 76 are wound around the ring portion of a ring-shaped ferrite 74. In this case, the appropriate number of turns is 1 to 2 times.

In any of the above cases, ferrite 71, 74
If the wires 72, 73, 75, 76 are damaged by A material with high magnetic permeability in low loss and low frequency bands is suitable.

As mentioned above, when transformer 7 is added,
The amount of leakage with respect to the input frequency of the protector is as shown by the broken line in FIG. For reference, the same characteristics of a conventional protector without the transformer 7 are shown by a solid line A. As shown in the figure, the leakage amount is less than -40 [dB] in the frequency band 50 to 300 [MH ₂ ], which is a level that does not affect other devices in the vicinity and does not cause interference.

Furthermore, according to the circuit configuration shown in FIG. 1 above,
It also has the advantage of being able to reduce the number of parts because it is possible to remove the choke, coupling capacitor, etc. as parts of the CATV protector.

[Effects of the Invention] As detailed above, according to the present invention, a ferrite element in which two insulated wires are wound is added between the input side plug and the output side plug, and the primary side of the two wires is are connected to the internal conductor and external conductor of the input side plug, and the secondary side is connected to the internal conductor and external conductor of the output side plug, respectively, and the external conductor of the output side plug and the main body of the protector are grounded. Since a capacitor is inserted between the metal case and the input side plug, it is possible to block the passage of direct current between the input side plug and the output side plug while allowing high frequency signals to pass through, and to reduce the leakage of high frequency signals to a sufficiently small level. It is possible to provide a leak-proof protector that can be used as a protector.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; Fig. 1 shows the circuit configuration, Fig. 2 is a vertical cross-sectional view showing the mounting structure, and Fig. 3 shows the specific structure of a two-wire wound ferrite (transformer). An illustrative diagram, FIG. 4, is a diagram showing the relationship between frequency and leakage amount in the present invention. 1... Input side connector, 1a... Input side connector inner conductor, 1b... Input side connector outer conductor, 2... Output side connector, 2a... Output side connector inner conductor, 2b... Output Side plug external conductor, 3... Metal case, 4... Earth line, 5... Grounding capacitor, 6... Lightning arrester, 7... Transformer, 8... Matching capacitor, 1
1...Input side connector tightening nut, 12...Insulator, 13...Output side connector tightening nut, 14...
...Metal cover, 71...Glasses-shaped ferrite, 7
2, 73, 75, 76...Conducting wire, 74...Ring type ferrite.

Claims (1)

[Claims] 1. In a protector that fixes the input side plug directly to a metal case and blocks the passage of direct current between the input and output of a coaxial cable but allows high frequency signals to pass, two wires insulated with ferrite are used. The primary side is connected to the internal conductor and external conductor of the input side plug, and the secondary side is connected to the internal and external conductor of the output side plug, and the A leak-proof protector characterized by having a plurality of capacitors inserted between an external conductor and the metal case.