JPS5924222Y2 - TenVision receiver antenna input device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an antenna input device for a television receiver, and in particular, to countermeasures against lightning strikes.

Generally, the antenna input device of a television receiver includes a DC blocking capacitor, an impedance conversion circuit for matching with a feeder line, and sometimes a VHF/UHF
The duplexer is composed of all HF.

In such an antenna input device, especially the above-mentioned VHF/UH
F duplexer All HF, but in the case of a duplexer that uses a wire-wound coil or copper foil pattern for its coil and a titanium conductor for its capacitor, it is called an Istarite type or a printed board type. Since the coil and capacitor have a sufficient margin in the withstand current characteristics, this can be achieved with the duplexer described above without any special consideration given to lightning strikes, and the tuner will not be destroyed. There wasn't.

However, in recent years, high-frequency component technology has improved and monolithic structure duplexers based on mica have been developed, but such duplexers have an extremely small current capacity, so they are susceptible to surge currents during lightning strikes. There is almost no effect to protect the tuner.

Therefore, television receivers that use such a duplexer or television receivers that do not have a VHF/UHF duplexer full HF require some kind of protection device against surge currents during lightning strikes. Various protection devices of this kind have been proposed, but all of them require special parts and are expensive.

However, the present invention proposes an antenna input device for a television receiver that does not require any special parts or the like and can block surge currents during lightning strikes with an extremely simple configuration.

Figure 1 shows an antenna input circuit implementing the present invention.
2 is an antenna input terminal of a television receiver to which a high frequency input signal is supplied via a coaxial cable with a characteristic impedance of 75Ω, 2 is an unbalanced-unbalanced matching transformer shown in FIG. 2, 3 is a bypass filter 4 and The VHF/UHF splitter HF7 consisting of the low-pass filter 5 is a UHF tuner and a VHF tuner, respectively.

In this configuration, the matching transformer 2 is the most distinctive feature of the present invention, and is different from the conventional unbalanced-unbalanced matching transformer used for noise prevention as shown in FIG. caution is required.

In other words, matching 1 to run in FIG.
The coil L shown in FIG.
1. L2 and L3. A first parallel line 11 and a second parallel line 1 each having a characteristic impedance of 150 g and forming L4.
2 to 2 to 3 times each.

This parallel line is conventionally used in the balloons described above.

and grounding both ends of the first parallel wire coil L1,
A second parallel wire coil L3 . One end of L4 is connected to each other, and this coil L3. The other end of L4 is commonly grounded.

The unbalanced-unbalanced transformer thus constructed has the first,
Since the characteristic impedance of the second parallel line is 150Ω, the terminals PI, PI' and P2. The characteristic impedances seen from P2' are considered to be equal to each other and about 75Q, and the terminals P1. P2 is the coil L3. It is DC grounded by L4.

Therefore, the terminals P1. of the transformer 2. P2 is the input/output terminal on the hotline side, and the grounded terminal P1
If ', P2' are connected as cold-side input/output terminals between the antenna input terminal 1 and the input terminal of the VHF/UHF splitter 3 as shown in FIG. 1, the following effects occur.

That is, both ends of the coil L1 are grounded, and the terminal P
1. P2 and P2. Since each impedance seen from P2' is approximately 75 g and equal to each other, this transformer itself can be considered to be approximately equivalent to a 75Q coaxial cable in terms of impedance. Therefore, signal loss in this transformer is small and mismatching is prevented. Does not occur.

In addition, in a television receiver not equipped with the duplexer 3, it is sufficient to connect it between the antenna input terminal and the input terminal of the tuner.

As described above, according to the present invention, surge currents during lightning strikes can be effectively blocked, and the unbalanced-unbalanced transformer used therein is fabricated using components that have been widely used in antenna input circuits. It can be realized at an extremely low cost, and there is no loss due to mismatching in this transformer.
Therefore, it can be directly connected between the antenna input terminal and the tuner input terminal without using a separate impedance matching circuit or the like, and is suitable as an antenna input device for a television receiver.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing the antenna input circuit of the present invention, Figure 2 is a circuit diagram showing the antenna input circuit of the present invention.
The figure is a wiring diagram showing an unbalanced-unbalanced matching transformer used therein, FIG. 3 is a wiring diagram showing a conventional transformer of this kind, and FIG. 4 is a model diagram showing the structure of the transformer shown in FIG. 2. 1... Antenna input terminal, 2... Unbalanced-unbalanced transformer, 3... VHF/UHF duplexer, 6, 7... Tuner, 8... Glasses-shaped core, 9, 10... Through hole for winding, 11.
12...First and second parallel lines.

Claims (1)

[Scope of utility model registration request] Characteristic impedance 1 constituting a pair of coils disposed close to each other in each of the pair of winding holes of the glasses-shaped core.
50g of first and second parallel wires are wound and inserted, both ends of one coil of the first parallel wire are grounded, and each of the second parallel wires is connected to both ends of the other coil of the first parallel wire. An unbalanced-unbalanced matching transformer is provided in which one end of each coil is connected and the other end of each coil is grounded, and both ends of the other coil of the first parallel line of this transformer are connected to the hot line side. An antenna input device for a television receiver, which is connected between an antenna input terminal and a tuner input terminal as an input/output terminal.