JP3099668B2 - Electronic tuner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic tuner used for broadband reception.

[0002]

2. Description of the Related Art As shown in FIG. 5, a conventional electronic tuner has an input terminal 1, a filter circuit 2 connected to the input terminal 1, and an output of the filter circuit 2 connected to one input. A mixer 4 to which the output of the local oscillation circuit 3 is connected to the other input, and an output terminal 5 to which the output of the mixer 4 is supplied are mounted on a printed circuit board in a frame (not shown). Was. In the filter circuit 2, three filters, a VHF band low band filter 2a, a VHF band high band filter 2b, and a UHF band filter 2c, are connected in parallel. Then, as shown in FIG. 6, the VHF band low band filter 2a and the VHF band
Band high band filter 2b and UHF band filter 2c
Are mounted on the same surface of the printed circuit board 6.

[0003]

However, in such a conventional configuration, as shown in FIG. 7A, the trap 82a of the VHF band low band filter 81a and the trap
82b and UH of the band high band filter 81b
The trap 82c of the F-band filter 81c interferes with a different filter band, and the entire band characteristic does not become a flat band characteristic as shown in FIG.

An object of the present invention is to provide an electronic tuner having a flat band characteristic without any interference between filters and eliminating the adverse effects of mutual filter traps. It is.

[0005]

In order to achieve this object, an electronic tuner according to the present invention connects three filter circuits of a VHF band low band filter, a VHF band high band filter and a UHF band filter in parallel. At the same time, the VHF band high band filter is mounted on one side of the printed circuit board in the frame, and the VHF band low band filter and the UHF band filter are mounted on the other side of the printed circuit board. .

[0006]

According to this structure, since the filters in the adjacent bands have different mounting surfaces on the printed circuit board, there is no interference between the filters, and there is no adverse effect due to mutual filter traps, and a flat band characteristic is obtained. be able to.

[0007]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a block diagram of an electronic tuner according to one embodiment of the present invention. An electronic tuner according to the present invention includes an input terminal 7, a filter circuit 8 connected to the input terminal 7, a first mixer connected to an output of the filter circuit 8 and an output of the first local oscillation circuit 9. And an intermediate frequency circuit 11 to which the output of the mixer 10 is connected.
And the output of the intermediate frequency circuit 11 is connected to one input, and the other input is connected to the second local oscillation circuit 1.
2 and the second mixer 13 having the output of
And an output terminal 14 to which the output is connected is mounted on a printed circuit board in a frame (not shown). The filter circuit 8 includes a VHF band low band filter 8a,
Three filters, a VHF band high band filter 8b and a UHF band filter 8c, are connected in parallel. Only the VHF band high band filter 8b has the V
The filter is provided on the printed circuit board on a different surface from the HF band low band filter 8a or the UHF band filter 8c. That is, as shown in FIG. 1, the VHF band high band filter 8b is mounted on one side of the printed circuit board 15 in the frame, and the VHF band low band filter 8a and the UHF band filter 8c are mounted on the other side of the printed circuit board 15. Has been implemented.

An input terminal 7 is provided near the UHF band filter 8c. As described above, since the UHF band has a high frequency, it is important to bring the UHF band as close as possible to the input terminal 7.

The operation of the electronic tuner configured as described above will be described below with reference to FIG. The high frequency signal input from the input terminal 7 is input to the first mixer 10 through the VHF band low band filter 8a, the VHF band high band filter 8b, and the UHF band filter 8c depending on the frequency. Mixer 1
At 0, it is mixed with the frequency output from the first local oscillator 9 to obtain an intermediate frequency. The output of the mixer 10 passes only the frequency determined by the intermediate frequency circuit 11. That is, the frequency is selected by changing the frequency of the first local oscillator 9. This output signal is input to the second mixer 13 and mixed with the output of the second local oscillator 12 to be converted to a predetermined constant frequency, and output to the output terminal 14.
Output from Then, the filter circuit 8 mounts the VHF band high band filter 8b on one surface side of the printed circuit board 15, and the VHF band low band filter 8a and the UHF band.
Since the band filter 8c is mounted on the other surface of the printed circuit board 15, between the VHF band low band filter 8a and the VHF band high band filter 8b as shown in FIG.
A ground pattern 16 is provided on the printed circuit board 17 between the VHF band high band filter 8b and the UHF band filter 8c to further increase the VHF band.
The band low band filter characteristics, the VHF band high band filter characteristics, and the UHF band filter characteristics can be separated.

Further, as shown in FIG. 1, a UHF band filter 8c is mounted at a position closest to the input terminal 7, a VHF band high band filter 8b is mounted at a position next to the input terminal 7, and a UHF band filter 8b is mounted at a position farthest. By mounting the VHF band low band filter 8a, loss in a high frequency band can be reduced.

[0012]

As described above, according to the electronic tuner of the present invention, the three filter circuits of the VHF band low band filter, the VHF band high band filter, and the UHF band filter are connected in parallel, and the VHF band filter is connected. The high band filter is mounted on one side of the printed circuit board in the frame, and the VHF band low band filter and the UHF band filter are mounted on the other side of the printed circuit board. Since the mounting surface on the substrate is different, there is no interference between the filters, and the adverse effects of the mutual filter traps are eliminated, and a flat band characteristic can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an electronic tuner according to an embodiment of the present invention.

FIG. 2 is a sectional view of a main part of an electronic tuner according to another example of the present invention.

FIG. 3 is a block diagram of an electronic tuner according to one embodiment of the present invention.

FIG. 4 is a characteristic diagram of a filter according to an embodiment of the present invention.

FIG. 5 is a block diagram of a conventional electronic tuner.

FIG. 6 is a sectional view of a main part of FIG. 5;

7A is an individual characteristic diagram of a conventional filter, and FIG. 7B is an overall characteristic diagram of a conventional filter.

[Explanation of symbols]

 7 Input Terminal 8 Filter Circuit 8a VHF Band Low Band Filter 8b VHF Band High Band Filter 8c UHF Band Filter 9 First Local Oscillator 10 First Mixer 12 Second Local Oscillator 13 Second Mixer 14 Output Terminal 15 Printed circuit board 17 Printed circuit board

────────────────────────────────────────────────── (5) References JP-A-4-35305 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 1/08-1/18 H04N 5 / 44

Claims (3)

(57) [Claims] 1. An input terminal, a filter circuit connected to the input terminal, a mixer connected to an output of the filter circuit and an output of a local oscillation circuit, and an output terminal to which an output of the mixer is supplied. And the filter circuit has VH
For F band low band, VHF band high band, UHF
Three filters for a band are connected in parallel, and
An electronic tuner in which a HF band high band filter is mounted on one side of a printed circuit board in a frame, and the VHF band low band filter and the UHF band filter are mounted on the other side of the printed circuit board. 2. The electronic tuner according to claim 1, wherein an input terminal is provided near the UHF band filter on the printed circuit board. 3. A VHF band low band filter and a VHF band
2. A printed circuit board having an earth pattern provided between the band high band filter and between the VHF band high band filter and the UHF band filter.
Electronic tuner according to 1.