JPS6242600A - Video intermediate frequency circuit apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a video intermediate frequency circuit (717 circuit) device using a surface wave filter used in color television receivers, video tape recorders, and the like.

BACKGROUND OF THE INVENTION In recent years, video tape recorders have been on the market, and industry has been competing to make them thinner and smaller. For this reason, there is an extremely strong demand for miniaturization of the parts used, and printed wiring boards are becoming more densely packed due to the adoption of chip parts. Furthermore, each major circuit has been made into a back, and the width of the circuit has been reduced from the horizontal direction to the vertical direction. Of course, it is a matter of course that regulations regarding the vertical direction are also strict.

The same goes for color television receivers, with efforts being made to increase the degree of IC integration and reduce the number of peripheral circuit components, thereby reducing the size of the circuit and reducing the total cost.

The 717 circuit and its peripheral circuits are no exception.
The degree of integration of ICs has increased, and not only VIPs but also audio intermediate frequency circuits (SIF circuits), integrated parts of video circuits, and now video circuits excluding the output section that consumes a lot of current,
A single-chip IC has even been developed that includes a chroma circuit, horizontal oscillation circuit, and vertical oscillation circuit. still,
The 717 circuit uses a surface wave filter and does not require adjustment of the VIF cutting section.

Here, in general, in a circuit using a single surface wave filter, there is direct induction from the input to the output of the surface wave filter.
It is known that if this direct guidance countermeasure is not taken, various types of interference will occur, such as ghosts and weak attenuation of adjacent traps, making them vulnerable to adjacent interference.

Hereinafter, with reference to the drawings, an example of a copper foil configuration of a mounted printed wiring board and a storage device thereof will be described as a countermeasure against direct induction of a VIP circuit using a conventional surface wave filter.

Before that, an example in which direct guidance from the input to the output of the surface wave filter is not considered is shown in FIG. 5, and the principle of causing the above-mentioned direct guidance will be explained.

In FIG. 5, 1 and 2 are the output terminals of the surface wave filter, and 3 is the input terminal of the surface wave filter, which are connected to the front and rear circuits by respective copper foils 7, 8, and 9. Reference numeral 6 denotes an input terminal of the IC, which is connected to the output terminals 1 and 2 of the surface wave filter through the copper foils 7 and 8 described above. Note that the above-mentioned IC input terminal 6 is connected to a differential amplifier in the internal circuit of the IC. Here, the copper foils 7 and 8 from the output terminals 1 and 2 of the surface wave filter to the input terminal 6 of the IC have different shapes and lengths and are asymmetrical to each other.

In this case, according to Japanese Patent Publication No. 69-25624, the fifth
When the output copper foils 7 and 8 of the surface wave filter are asymmetrical to each other as shown in the figure, the direct The value of the induced voltage is different between the surface wave filter output terminal 1 and the surface wave filter output terminal 2. Therefore, since the signal is transmitted to the subsequent circuit without being canceled by the differential operation of the differential amplifier in the internal circuit of the IC connected to the IC input terminal 6, the various disturbances described above appear. One countermeasure for this is to reduce the current flowing through the grounding foil 1o running between the input terminal 3 and output terminals 1 and 2 of the surface acoustic wave filter.
The above-mentioned patent publication No. 5 shows that there is a method for suppressing the induction of unnecessary signals. In addition, in FIG. 6, numeral 4 is a surface wave filter ground terminal, and numeral 11 is a chip component. Figure 6 shows a conventional example incorporating this method, where 12 is a frame, 1
3 is a mounted printed wiring board containing a VIP circuit, one or more circuits are made into blocks, and a frame prosthesis 14 and a terminal 1 are mounted.
5 so that it can be connected to other mounted printed wiring boards. Here, the ground foil of the mounted printed wiring board 13 is connected to the frame 12 at various locations by soldering 16.

By doing so, the earth impedance of the circuit is lowered and the current flowing through the earth foil described above is suppressed.

FIG. 7 shows a countermeasure for direct induction from the input to the output of the surface wave filter described in the above patent publication, where 1 and 2 are the output terminals of the Shishimen wave filter, and 3 is the input terminal of the surface wave filter. , 6 are ICi input terminals, which are connected to a differential amplifier inside the IC. 7 and 8 are the output terminals 1 and 2 of the surface wave filter, and the IC input terminal 6.
It is copper foil that connects the two, forming a mutually symmetrical figure.

The example shown in FIG. 7 is a countermeasure for the example shown in FIG. Since the values of the output terminal 1 of the surface wave filter and the output terminal 2 of the surface wave filter are almost equal, the directly induced voltage caused by the above is canceled by the differential operation of the differential amplifier inside the IC, and is The configuration was such that it was not transmitted to the circuit.

Problems to be Solved by the Invention However, with the above configuration, it is extremely difficult to design a printed circuit board pattern in a limited space, and in order to prevent direct guidance from the input to the output of the surface wave filter. , the earth impedance of the circuit must be lowered at high frequencies. To do this, the ground pattern of the printed board must be made as wide as possible, and the ground pattern must be extended around the printed board and soldered to various parts of the frame. Therefore, the problem is that miniaturization is inevitably very difficult.

In view of the above-mentioned problems, the present invention makes it possible to sufficiently reduce the size of the parts used to the required absolute area, easily lower the earth impedance, and connect the surface wave filter from the input to the output. The purpose of the present invention is to provide a VIP circuit device that can electromagnetically cut off the direct induction of.

Means for Solving the Problems In order to solve the above problems, the VIP circuit device of the present invention includes:
A mounted printed wiring board on which a VIP circuit using a surface wave filter is mounted, an outer frame framed so that the mounted printed wiring board can be incorporated inside, and an input section for the surface wave filter located inside the frame. The present invention is characterized by having an inner frame that shields and crosses between the output section and the output section, and is electrically connected to the ground foil on the printed wiring board.

Effects of the present invention With the above-described configuration, the legs can be attached to the necessary parts of the inner frame so as to touch the grounding foil of the wiring board, so that even if the grounding foil is interrupted, the connection can be made at the inner frame, so that the printed wiring board can be easily connected. The pattern design is easy, and direct guidance from the input to the output of the surface wave filter can be easily prevented by extending a wide leg of the inner frame in the center of the surface wave filter so as to separate the input section and the output section.

It also fully contributes to miniaturization.

Embodiment Hereinafter, a VIP circuit device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a plan view of essential parts showing an embodiment of the present invention. 1st
In the figure, 1 and 2 are the output terminals of the surface wave filter, 3
is the input terminal of the surface wave filter, and 8 and 9 are copper foils for connecting the respective terminals of the surface wave filter to the circuits before and after.

2o is a part of the inner frame, which crosses the center of the surface acoustic wave filter so as to separate the input section and the output section of the surface acoustic wave filter, and is soldered to the ground copper foil 10.

FIG. 2 is a perspective view of a VIP circuit storage device showing one embodiment of the present invention, in which 21 is an outer frame, 2° is an inner frame,
3 is an output terminal of the surface wave filter, 4 is an input terminal of the surface wave filter, and 22 is a mounted printed wiring board. Here, the inner frame 2o is made of metal that can be soldered, and is designed so that it can be freely assembled into an integral structure using a press method. In addition, legs can be protruded from various parts of the inner frame 20 and soldered to the ground copper foil of the mounted printed wiring board 22. Furthermore, the legs of the inner frame 20 are extended laterally across between the output terminal 3 of the surface wave filter and the input terminal 4 of the surface wave filter, so that they can be soldered to the ground copper foil of the mounted printed wiring board 22. (shaded area in Figure 2).

As described above, according to this embodiment, the surface wave filter is mounted in the center of the surface wave filter in order to reduce the ground impedance of the circuit by extending the legs so that it can be soldered to the ground copper foil of the printed wiring board mounted on the inner frame. By extending the legs of the inner frame wide enough to cross between the input and output terminals of the filter and soldering them to ground foil, the so-called shielding effect that cuts off the direct induction from the input to the output of the surface wave filter can be achieved. You can have it. Therefore, in FIG. 4, the overall characteristics of vIF according to this embodiment are shown as a curved line.
It is possible to prevent ghosts and adjacent disturbances that occur when receiving direct guidance as shown in curve B.

FIG. 3 is a plan view of another embodiment, in which the tuner and VIP
This is a VIP circuit device with integrated circuits.

In FIG. 3, 30 is a tuner section, 31 is a VIF section,
Reference numeral 21 indicates an outer frame, and 20 indicates an inner frame (shaded portion), which are inserted into the outer frame 21 in close contact with each other.

Further, as described in FIG. 2, the inner frame 2o has legs extending in various places so as to be connected to the ground copper foil of the mounted printed wiring board 22 by soldering. Originally, a tuner would have a partition for each circuit to lower the ground impedance and provide shielding. In FIG. 3, the above-mentioned partition is extended to the vIF side, and the same method as that described in FIG. 2 is used to achieve the same effect as the embodiment shown in FIG.

The embodiment shown in FIG. 3 also has the advantage of being low in cost since it is not necessary to create a special inner frame only on the vIF side and it can be integrally constructed by pressing at the same time as the chewing side.

Effects of the Invention As described above, the present invention provides a V
The mounted printed wiring board on which the IP circuit is mounted is fixed to the framed outer frame, inserted so as to fit tightly inside the outer frame, and soldered to any copper T3 (copper foil for grounding) on the mounted printed wiring board. The inner frame is designed to cross between the input and output terminals of the surface wave filter, and it can also be soldered to the ground copper foil of the mounted printed wiring board, so the VIF input circuit It is possible to eliminate direct guidance from the input to the output of the surface wave filter used in the system, and it is possible to prevent ghosting and adjacent channel interference.

[Brief explanation of the drawing]

FIG. 1 is a plan view of essential parts of one embodiment of the VIP circuit device of the present invention, FIG. 2 is a perspective view of one embodiment of the VIP circuit device of the present invention, and FIG. 3 is a plan view of another embodiment of the VIP circuit device of the present invention. Plan view, Figure 4 is V
Figures 5 and 7 showing the IP total waveform are the conventional V
FIG. 6 is a plan view of the main parts of the IP circuit device, and a side view of the conventional VIP circuit device. 1.2...Output terminal, 3...Input terminal, 4...Earth terminal, 7, 8, 9...Copper foil,
10...Ground copper foil, 20...Inner frame. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Fig. t, -*ty* to 3-11

Claims (1)

[Claims] A printed circuit board on which a video intermediate frequency circuit using a surface wave filter is mounted, an outer frame assembled to fix the printed circuit board, and an input circuit mounted inside the outer frame, and an input circuit for the surface wave filter. A video intermediate frequency circuit device comprising: an inner frame that extends shieldingly between the output section and the output section, and is electrically connected to a ground foil on the printed wiring board.