JPH0526870Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field of the invention] This invention is a cable that is installed between a coaxial cable that transmits high-frequency signals such as CATV and a terminal such as a television receiver, cuts off abnormal voltage, and is grounded. The present invention relates to a ferrite transformer for a protector used in a protector that transmits high frequency signals without loss.

[Prior Art and Its Disadvantages] Conventional protectors have considered blocking abnormal voltages such as those caused by lightning strikes and transmitting high-frequency signals, but little consideration has been given to leakage of high-frequency signals. However, in urban CATV and CATV in strong electrolytic areas, in order to overcome external interference waves, the amplification output has been increased and high-level radio 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. There was a drawback that high-frequency signals leaked from this part and caused interference to others.

[Purpose of the invention] This invention was made in view of the above-mentioned circumstances, and is designed to prevent leakage while allowing high-frequency signals to pass without passing direct current between the input and output plugs of the coaxial cable. The purpose of the present invention is to provide a ferrite transformer for a protector that can

[Summary of the invention] This invention adds a ferrite element in which two insulated wires are wound and a correction circuit between the input side plug and the output side plug of the protector.

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

FIG. 1 shows the circuit configuration, and the input side plug is composed of an inner conductor 1 and an outer conductor 2, and the outer conductor 2 is fixed to a metal case 14 (not shown). Similarly, the output side plug also has internal conductor 3.
and an external conductor 4, and the external conductor 4 is connected to an earth line 15 via a grounding capacitor 12. In addition, the side to the left of I indicated by the two-dot chain line in the figure is the lightning arrester of the protector, which is the same as the conventional configuration.
The circuit on the right is the circuit of the present invention. The input side plug internal conductor 1 is connected to the two wire-wound ferrite 7 via the fuse 13.
This double wire-wound ferrite 7 is connected to the primary side of the
The other primary side is connected to the output side plug internal conductor 3 via a coupling capacitor 9. Furthermore, a choke coil 5 and a lightning arrester 6 are connected to the metal case 14 in parallel. One of the secondary sides of the two-wire-wound ferrite 7 is grounded together with the input-side connector inner conductor 2, and the other side is connected to the output-side connector outer conductor 4 via the coupling capacitor 10, and connected to the metal case 14 by the grounding coil 8.
It is grounded through an earth line 15.
A matching capacitor 11 provides matching on the output side of the two-winding ferrite 7.

As described above, the metal case 14 is grounded via the ground line 15.

The input side explained above is a convenient name for the abnormal voltage generation side, and is generally
Connected to the CATV coaxial cable side. On the other hand, the output side is the terminal side, which is connected to the television receiver in the home. These input side and output side have reversibility with respect to high frequency signals.

Next, FIG. 2 shows its main configuration. The input side plugs 1 and 2 are directly fixed to the metal case 14 with an input side tightening nut 24. In addition, output side plugs 3 and 4
is insulated from the metal case 14 via an insulator 23,
Furthermore, it is fixed with an output side plug tightening nut 25 so as not to rotate mechanically. A lightning arrester 6, a choke coil 5, a two-wire wound ferrite 7, etc. are connected between the input side plugs 1, 2 and the output side plugs 3, 4 via coupling capacitors 9, 10. Furthermore, a matching capacitor 11 is connected between the coupling capacitors 9 and 10, and a grounding capacitor 1 is connected between the external conductor 4 and the metal case 14.
Connect 2, 12... Then, the entire circuit described above is covered with a metal cover 22. The capacitors 9 to 12 used here each have a withstand voltage of 500 V or more, the coupling capacitors 9 and 10 each have a capacitance of 1000 pF, the matching capacitor 11 has a capacitance of 5 pF, and the grounding capacitor 12 has a capacitance of 2200 pF. It is set as two connected in parallel.

In the protector configured as above,
A high frequency signal used for CATV is transmitted to the input-side plug internal conductor 1, and then to the output-side plug internal conductor 3 through the fuse 13, the double-wire-wound ferrite 7, and the coupling capacitor 9. On the other hand, between the input side connector outer conductor 2 and the output side connector outer conductor 4,
The high frequency signal is conducted by the grounded capacitor 12.

If an abnormal voltage due to a lightning strike or a current leakage is applied to the input side plug inner conductor 1 and outer conductor 2, a short circuit is caused by the chiyoke coil 5 and the voltage decreases. The high voltage with a steep waveform at this time causes an arc in the lightning arrester 6 and short-circuits with the outer conductor 2, but is blocked by the coupling capacitor 9 and is not transmitted to the output inner conductor 3. Especially when the current due to abnormal voltage is large, the fuse 13 blows and protects the connected coaxial cable. In addition, if an abnormal voltage is applied between the input side external conductor 2 and the internal conductor 1, the abnormal voltage will not be transmitted because the output side plug external conductor 4 is cut off by the grounding capacitor 12. ,
The television receiver connected to the output side plugs 3 and 4 can be protected.

Next, the two-wire wound ferrite 7, which is the main part of the present invention, will be explained with reference to FIGS. 3 and 4. Third
The figure shows the basic configuration of the ferrite bar.
3, and the input terminal and output terminal on the secondary side are 32, 3.
Wind the two wires marked 4. The input/output terminals 32 and 34 on the secondary side are each grounded. The two-wire wound ferrite 7 with such a configuration becomes an all-band pass circuit. That is, balanced transmission in a high frequency band results in a large inductance, and unbalanced transmission such as coaxial cable transmission is hardly attenuated, making it possible to prevent leakage. However, in a circuit in which the capacitance is set to be large, such as the output side circuit elements 9 to 12 in FIG. 1, such a configuration cannot completely prevent leakage.

In FIG. 4, as shown in FIG. 1 above, an inductance 8 is provided between the secondary output terminal 34 and the ground. By adopting such a configuration, the double-wire-wound ferrite 7 is given a reduced-passage type characteristic, making it compatible with circuits with large capacitances such as the output-side circuit elements 9 to 12 in FIG. 1 above, and completely preventing leakage. It was designed to prevent this.

The following FIGS. 5a and 5b show specific structures of the two-wire wound ferrite 7 and the ground coil 8, respectively. As shown in FIG. 5a, the two wire-wound ferrite bar 7 corresponds to high frequency signals of 10 to 500 MHz used in CATV. Holes 7b and 7c are formed in the same direction, and conducting wires 7d and 7e are wound one to three times around the holes 7b and 7c. In this case, it seems appropriate for the conductors 7d and 7e to be copper wires with a thickness of about 0.25 mm coated and insulated with formal or polyethylene.

FIG. 5b shows a specific configuration of the grounding coil 8. For example, a cylindrical ferrite bar 8a with a diameter of 3 mm and a length of 5 mm is formed with an axial hole 8b, and a conductive wire 8c is inserted into the hole 8b by 0.5 mm. It is composed of ~3 turns.

As the above-mentioned ferrite, a material that has a large μ at low frequencies, decreases as the frequency increases, and exhibits low loss in the high frequency band is suitable.

As described above, when the double-wire-wound ferrite 7 is added and a correction circuit for the double-wire-wound ferrite 7 is further added, the amount of leakage with respect to the input frequency of the protector becomes as shown by the broken line B in FIG. For reference, add only the two wire-wound ferrite 7, and
The amount of leakage with respect to the input frequency of the protector when the correction circuit for the main wire-wound ferrite 7 is not added is shown by a solid line A in FIG. 10dB when frequency is below 300MHz
The above improvements have been made, and it can be seen that the grounded coil 8, which is a correction circuit added to the double wire-wound ferrite 7, has a great effect. If the amount of leakage is -40 dB, it will not affect other devices in the vicinity and will not cause interference, so it can be understood that this protector has a sufficient leakage prevention function.

Further, since this circuit has reversibility, the same effect can be obtained even if the input side and the output side are switched, which is advantageous in terms of handling.

In addition, in areas with strong TV signal electric fields, the direct wave of the TV signal may pass through the coaxial cable, mix with the TV receiver, and cause interference with the CATV signal.
This may cause the so-called pre-ghost phenomenon,
By using the circuit on the right side of the circuit shown in FIG. 1 from which the lightning arrester on the left side of the two-dot chain line I is removed, the above-mentioned trouble can be easily eliminated.

[Effects of the invention] As detailed above, this invention prevents the passage of direct current between the input and output plugs of the coaxial cable, allowing only high-frequency signals to pass, while preventing leakage of the same high-frequency signals. It is possible to provide a ferrite transformer for a protector that can prevent this.

[Brief explanation of the drawing]

The drawing shows one embodiment of this invention.
The figure shows the circuit configuration of the protector, Figure 2 shows the mounting structure of Figure 1, Figure 3 shows the basic configuration of the two-wire wound ferrite, and Figure 4 shows the circuit configuration of the protector. A diagram showing the structure of main wire-wound ferrite, Figure 5a
is a diagram showing a specific structure example of the same double wire-wound ferrite,
FIG. 5b is a diagram showing a specific structural example of a grounding coil, and FIG. 6 is a diagram showing the relationship between frequency and leakage amount in the present invention. DESCRIPTION OF SYMBOLS 1...Input side connector internal conductor, 2...Input side connector outer conductor, 3...Output side connector internal conductor, 4...Output side connector outer conductor, 5...Chiyoke coil, 6...
...Surge arrester, 7...2 wire-wound ferrite, 7a, 8
a... Ferrite bar, 7b, 7c, 8b...
Hole, 7d, 7e, 8c... Conductor wire, 8... Grounding coil, 9, 10... Coupling capacitor, 11... Matching capacitor, 12... Grounding capacitor 2, 13...
...Fuse, 14...Metal case, 22...Metal cover, 23...Insulator, 24...Input side connector tightening nut, 25...Output side connector tightener,
31...Primary input side terminal, 32...Secondary input side terminal, 33...Primary output side terminal, 34...Secondary output side terminal.

Claims (1)

[Scope of utility model registration request] In an all-band pass circuit, two wires are wound around a ferrite core in a metal case, the primary winding is connected to the input and output center conductors of the coaxial cable via a capacitor, and the secondary side is grounded. , an inductance element is added to one end of the secondary side, connected to the outer conductor of the coaxial cable on the output side via a capacitor, and further grounded between the outer conductor and the metal case via the capacitor. Ferrite transformer for safety device.