JP3738500B2 - Antenna circuit for TV tuner device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an antenna circuit for a TV tuner device, and more particularly to an antenna circuit including a CB filter and an IF filter.
[0002]
[Prior art]
Conventionally, such an antenna circuit for a TV tuner device is configured, for example, as shown in FIG. That is, in FIG. 3, an antenna circuit 1 for a TV tuner apparatus includes an antenna terminal 2 to which a reception signal from an antenna is input, a first filter 3 to which a reception signal from the antenna terminal 2 is input, and a first filter It includes a second filter 4 to which an output signal from the filter 3 is input, and three antenna tuning circuits 5, 6, and 7 to which an output signal from the second filter 4 is input, respectively.
[0003]
The first filter 3 is a so-called CB filter, and in order to exclude a CB (civil band) radio signal, a capacitor 3a connected in series to the line, and an input side and an output side of the capacitor 3a and a ground It is configured as a high-pass filter composed of coils 3b and 3c connected in between.
Here, the circuit constants of the capacitor 3a and the coils 3b and 3c are selected so that the first filter 3 cuts a frequency of 28 MHz or less which is a frequency of CB radio.
[0004]
The second filter 4 is an IF filter, and is configured as a trap filter including a capacitor 4a and a coil 4b connected in series with each other in series in order to cut the frequency of the IF frequency.
Here, the circuit constants of the capacitor 4a and the coil 4b are selected so that the second filter 4 traps, for example, 38.9 MHz as the IF frequency.
[0005]
Further, of the three antenna tuning circuits, the first antenna tuning circuit 5 is a VHF high-band antenna tuning circuit, and the output signal from the second filter 4 is directly input thereto. ing.
The second antenna tuning circuit 6 is an antenna tuning circuit for VHF low band, and the third antenna tuning circuit 7 is an antenna tuning circuit for UHF, and each of the output signals from the second filter 4 Is input via the capacitor 8.
[0006]
According to the antenna circuit 1 for a TV tuner device having such a configuration, the signals transmitted through the first and second filters 3 and 4 are cut below the CB frequency as shown in FIG. After the vicinity is trapped, it is input to each antenna tuning circuit 5, 6, 7.
[0007]
[Problems to be solved by the invention]
However, in the antenna circuit 1 configured as described above, three coils 3b, 3c, and 4b are necessary as parts constituting the two filters 3 and 4, and the number of parts is large and the cost is increased. There was a problem.
[0008]
In addition, an unnecessary component between the CB frequency and the IF frequency is input to the antenna tuning circuits 5, 6, and 7, which causes a problem of reception failure.
[0009]
In view of the above, the present invention has an antenna circuit for a TV tuner device that has a small number of components, can reduce component costs and assembly costs, and can eliminate unnecessary components between the CB frequency and IF frequency. The purpose is to provide.
[0010]
[Means for Solving the Problems]
According to the present invention, according to the present invention, a CB filter that removes a CB frequency component, an IF filter that removes an IF frequency component, and an output signal that has passed through these filters are input from a received signal from an antenna input terminal. In an antenna circuit for a TV tuner device, including an antenna tuning circuit for a VHF high band, an antenna tuning circuit for a VHF low band, and a UHF antenna tuning circuit, the IF filter is connected in series to a line from the antenna input terminal. and a trap filter consisting of a coil connected and a capacitor in parallel with each other, wherein the CB filter, between the output line and the ground from the IF filter, trap filter comprising a capacitor and a coil connected in series with each other The VHF high-band antenna tuning circuit The output signal from the CB filter is directly input to the VHF low-band antenna tuning circuit and UHF antenna tuning circuit is characterized in that the output signal from the CB filter is inputted via the capacitor, TV tuner device This is achieved by an antenna tuning circuit.
[0011]
The antenna circuit for a TV tuner device according to the present invention is preferably configured such that the IF filter removes an IF frequency component near the video IF frequency.
[0012]
The antenna circuit for a TV tuner apparatus according to the present invention is preferably configured such that the CB filter removes a CB frequency component near the CB radio frequency.
[0013]
According to the above configuration, the IF filter that removes the IF frequency component and the CB filter that removes the CB frequency component are each configured as a trap filter including one coil, and therefore, have two coils as a whole. . Therefore, the number of coils required for constituting the filter is small, and the part cost and the assembly cost can be reduced.
[0014]
Moreover, the unnecessary component between IF frequency and CB frequency can also be removed by the combination of two trap filters.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on the embodiments shown in the drawings.
FIG. 1 shows an embodiment of the device according to the invention.
That is, in FIG. 1, an antenna circuit 10 for a TV tuner apparatus includes an antenna terminal 11 to which a reception signal from an antenna is input, a first filter 12 to which a reception signal from the antenna terminal 11 is input, and a first filter A second filter 13 to which an output signal from the filter 12 is input, and three antenna tuning circuits 14, 15 and 16 to which an output signal from the second filter 13 is input are included.
[0016]
The first filter 12 is an IF filter, and is configured as a trap filter composed of a coil 12a and a capacitor 12b connected in series to each other and in parallel to each other in order to trap the frequency of the IF frequency. Yes.
Here, the circuit constants of the coil 12a and the capacitor 12b are selected so that the first filter 12 traps, for example, a frequency component around 38.9 MHz as the IF frequency.
[0017]
The second filter 13 is a so-called CB filter, and is a trap filter composed of a capacitor 13a and a coil 13b connected in series between the line and ground in order to eliminate CB (civil band) radio signals. It is configured as.
Here, the circuit constants of the capacitor 13a and the coil 13b are selected so that the second filter 13 traps a frequency component in the vicinity of 28 MHz, which is the frequency of the CB radio.
[0018]
Of the three antenna tuning circuits, the first antenna tuning circuit 14 is a VHF high-band antenna tuning circuit, and the output signal from the second filter 13 is directly input thereto. .
The second antenna tuning circuit 15 is a VHF low-band antenna tuning circuit, and the third antenna tuning circuit 16 is a UHF antenna tuning circuit, and each outputs an output signal from the second filter 13. Is input via the capacitor 17.
[0019]
The antenna circuit 10 for a TV tuner device according to the embodiment of the present invention is configured as described above, and signals transmitted through the first and second filters 12 and 13 are, as shown in FIG. The vicinity of the CB frequency is trapped by the first and second filters 12 and 13 and then input to the antenna tuning circuits 14, 15 and 16.
[0020]
In this case, since the second filter 13 is composed of the capacitor 13a and the coil 13b, only one coil is required. Therefore, compared with the CB filter 3 in the conventional antenna circuit 1 shown in FIG. One coil is reduced. Thus, the number of parts can be reduced, the part cost and the assembly cost can be reduced, and the apparatus can be made compact.
[0021]
Further, as shown in FIG. 2, the received signals that have passed through the first and second filters 12 and 13 can also remove unnecessary components between the CB frequency and the IF frequency. , 16 can also be avoided.
[0022]
【The invention's effect】
As described above, according to the present invention, the IF filter that removes the IF frequency component and the CB filter that removes the CB frequency component are each configured as a trap filter including one coil. A coil will be provided. Therefore, the number of coils required for constituting the filter is small, and the parts cost and assembly cost can be reduced.
[0023]
Moreover, the unnecessary component between IF frequency and CB frequency can also be removed by the combination of two trap filters.
[0024]
Thus, according to the present invention, an extremely excellent antenna for a TV tuner device that has a small number of components, can reduce component costs and assembly costs, and can eliminate unnecessary components between the CB frequency and the IF frequency. A circuit could be provided.
[Brief description of the drawings]
FIG. 1 is a block circuit diagram showing an embodiment of an antenna circuit for a TV tuner device according to the present invention.
FIG. 2 is a graph showing frequency characteristics after passing through a filter in the antenna circuit of FIG. 1;
FIG. 3 is a block circuit diagram showing an example of a conventional antenna circuit for a TV tuner device.
4 is a graph showing frequency characteristics after passing through a filter in the antenna circuit of FIG. 3;
[Explanation of symbols]
10 Antenna circuit for TV tuner device 11 Antenna input terminal 12 First filter (IF filter)
12a Coil 12b Capacitor 13 Second filter (CB filter)
13a Capacitor 13b Coil 14 VHF high band antenna tuning circuit (antenna tuning circuit)
15 VHF low band antenna tuning circuit (antenna tuning circuit)
16 UHF antenna tuning circuit (antenna tuning circuit)
17 Capacitor

Claims (3)

A CB filter for removing CB frequency components from the received signal from the antenna input terminal; an IF filter for removing IF frequency components; a VHF high-band antenna tuning circuit to which an output signal that has passed through these filters is input ; and VHF In an antenna circuit for a TV tuner device, including a low-band antenna tuning circuit and a UHF antenna tuning circuit ,
The IF filter is a trap filter composed of a coil and a capacitor connected in series with each other in series with a line from an antenna input terminal;
The CB filter, the between the output line and the ground from the IF filter, a trap filter comprising a capacitor and a coil connected in series with each other,
The output signal from the CB filter is directly input to the VHF high band antenna tuning circuit, and the output signal from the CB filter is input to the VHF low band antenna tuning circuit and the UHF antenna tuning circuit via a capacitor. characterized in that, TV tuner device antenna tuning circuit.   The antenna tuning circuit for a TV tuner device according to claim 1, wherein the IF filter is configured to remove an IF frequency component in the vicinity of the video IF frequency.   The antenna tuning circuit for a TV tuner device according to claim 1, wherein the CB filter is configured to remove a CB frequency component in the vicinity of a CB radio frequency.

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