JPH0738827A - Structure of if substrate incorporating tuner - Google Patents

Abstract

PURPOSE:To prevent the leakage of spurious radiation to the IF substrate of the IF substrate incorporating tuner. CONSTITUTION:A tuner substrate arranged at a tuner part 1a and the IF substrate arranged at an IF part 1b are arranged in a single shield case 1 and integrated, the tuner substrate and IF substrate are shielded from each other by a shield plate 1c, and the tuner substrate and IF substrate are connected via through capacitor Ca and Cb provided on the shield substrate 1c. Further, the through capacity Cb which leads out an IF output is a part of a dedouble- tuned circuit 10 on the IF substrate side and is supplied with electric power through IF lines 2b and 3b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an IF board integrated tuner in which an IF board and a tuner board are arranged in a single shield case.

[0002]

2. Description of the Related Art For example, a television tuner provided for receiving VHF is usually shielded by a shield case, and the tuner board is manufactured by reflow soldering. The IF unit that amplifies the intermediate frequency in this tuner portion is manufactured by dip soldering. Therefore, R of receiver etc.
The F circuit and the IF circuit are separate circuit boards, and are conventionally configured to be shielded and used separately. However, because of space saving and other problems
It is considered that they are arranged in individual shield cases and are connected via a shield plate in the cases.

FIG. 4 is a block diagram showing an outline of a case where a tuner board and an IF unit are connected and integrated. In this figure, 1 is a shield case, 1a is a tuner section in which a tuner board 2 for selecting broadcast waves received by an antenna A is arranged, and 1b is an IF board 3 for amplifying an intermediate frequency (IF) converted in the tuner section 1a. Shows the IF section in which is arranged. The tuner section 1a and the IF section 1b are wholly disposed inside the shield case 1, and adjacent portions are shielded by a shield plate 1c indicated by a dotted line. Reference numeral 4 denotes a connector which is arranged by opening a part of the shield plate 1c and which connects the tuner board 2 and the IF board 3 to each other.

As shown in FIG. 5, this connector 4 includes AGC (auto gain control) lines 2a and 3a, IF lines 2b and 3b, a power supply line 2c, and a tuner board 2 and an IF board 3, respectively. It has a pair of connection terminals for connecting 3c with 3 pins, and these lines are connected so as to penetrate through the shield plate 1c in the shield case 1.

[0005]

By the way, when the tuner board 2 and the IF board 3 are connected by the connector 4 and used as an integrated unit, if a normal connector is used for the connection, it is not necessary to release the tuner board 2. The radiated radio waves leak to the IF substrate 3 and are emitted from the IF substrate 3 to the outside, which causes deterioration of radiation (radiation of unnecessary radio waves). Therefore, when the FCC standard cannot be cleared due to the deterioration of the radiation, the IF lines 2b and 3b and the AGC line 2a,
For example, a filter is inserted in 3a so that a high-frequency signal component does not leak, and a bypass capacitor or the like is arranged.

However, by disposing the bypass capacitors and the line filters on both substrates 2 and 3, there is a problem that the number of elements mounted on each substrate 2 and 3 increases and the cost increases.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve such problems, and a tuner section substrate and an IF board are arranged and integrated in a single shield case, and the tuner section described above is integrated. The board and the IF board are mutually shielded by a shield plate, and an IF board integrated tuner is formed so that the tuner board and the IF board are connected to each other through a feedthrough capacitor provided on the shield board. .

The feedthrough capacitor for deriving the IF output is a part of the tuning circuit on the IF substrate side, and
Power is supplied through the IF output line.

[0009]

By using the feedthrough capacitor as the connector, the tuner board can be shielded almost completely, the leakage of the oscillator to the IF board can be prevented, and the deterioration of the radiation can be avoided.

[0010]

EXAMPLES Examples of the structure of the IF substrate integrated tuner of the present invention will be described below. FIG. 1 is an external perspective view of a shield case having a structure of an IF substrate integrated tuner of the present invention. Similar to FIG. 4, 1 is a shield case, 1a is a tuner section, and 1b is an IF section. Reference numeral 5 denotes a connection portion of an antenna cable through which a reception signal is transmitted from an antenna that receives broadcast radio waves, and 6a and 6b denote attachment pieces on a board of an electronic device that are provided so as to project from the bottom side portion of the shield case 1. . Reference numeral 7a indicates an external connection terminal of the tuner board 2 arranged inside the tuner section 1a, and 7b indicates an external connection terminal of the IF board 3 arranged inside the IF section 1b.

Also in this embodiment, the tuner section 1a and the IF section 1b are internally shielded by the shield plate 1c. The tuner board 2 and the IF board 3 inside are connected by a feedthrough capacitor arranged so as to pass through the shield plate 1c as described below.

FIG. 2A is a view showing the external appearance of the feedthrough capacitor, and FIG. 2B is a perspective view showing the connection state of the tuner substrate 2 and the IF substrate 3 using the feedthrough capacitor. In these drawings, C (C _a , C _b , C _c ) represents a feedthrough capacitor, which is inserted into a through hole provided in the shield plate 1c, and the flange portion F is soldered to the shield plate 1c. ing. 2a and 3 shown in FIG.
a is an AGC line, 2b and 3b are IF lines, 2c and 3
c indicates a power supply line.

One end of the feedthrough capacitor C _a has an AGC line 2a on the tuner board 2, and the other end has an AGC line on the IF board 3.
On the line, one end of the feedthrough capacitor C _b is the tuner board 2
IF line 2b, the other end to the IF line 3b of the IF substrate 3, one end of the feedthrough capacitor C _c to the power source line 2c of the tuner substrate 2, the other end to the power source line 3c of the IF substrate 3, and solder H or the like. It is connected.

The capacitances of the feedthrough capacitor C _a used for connecting the AGC lines 2a and 3a and the feedthrough capacitor C _b used for the power supply lines 2c and 3c are about 1000 pF, and IF.
The capacitance of the feedthrough capacitor C _c used for the lines 2b and 3b is set to several pF to 10 pF.

As shown in FIG. 2B, the AGC
Line 2a, 3a, IF line 2b, 3b, the power supply line 2c, and 3c, by connecting to a feedthrough capacitor C _a -C _c that is fixed through the shield plate 1c, almost completely shielded tuner portion 1a Will be done.
Therefore, it is possible to suppress leakage of, for example, a local oscillator or unnecessary sideband frequency emitted from the tuner substrate 2 and prevent deterioration of radiation.

Next, in the case of the present invention, the IF line 2b,
The feedthrough capacitor C _b to derive 3b, by a part of the tuning circuit of the IF substrate 3, IF line 2b, 3
Power can be supplied via b. FIG. 3 is a diagram showing an example of a coupling circuit of the tuner section and the IF section when the feedthrough capacitor C _b is part of the tuning circuit.
In this figure, 10 is an IF double-tuned circuit consisting of a feedthrough capacitor C _b penetrating the shield plate 1c, a coil L ₂ , and a capacitor C ₂ and a coil L ₃ , and 11 is an IF preamplifier.

As shown in the drawing, when the IF double-tuned circuit 10 is arranged between the output line of the transistor Q ₁ for a mixer provided on the tuner substrate 2 and the input line of the IF substrate 3, A tuning circuit (coil L ₃ and capacitor C ₂ ) is arranged on the IF substrate 3 side, and a DC voltage is superposed from the cold side, that is, the coil L ₄ and capacitor C ₃ sides, and the IF circuit 2b, 3b It becomes possible to apply to the tuner substrate 2. Q ₂ is I
The first-stage amplification transistor of the F-amplifier 11 is shown. C ₄ is a coupling capacitor, and R ₁ , R ₂ , R ₃ , and C ₅ are resistors and capacitors for bias measurement.

When the tuner board 2 and the IF board 3 are connected in this way, the IF lines 2b and 3b can also be used as the power supply lines 2c and 3c.
The power supply lines 2c and 3c can be omitted. Further, by setting the ground capacitance of the feed-through capacitor C _b and a portion of the output tuning circuit of the tuner board 2, as well as simplify the circuit, the tuner board 2 and the IF board 3, IF
Feedthrough capacitors _Cb , AGC for line and power line
Connection is possible with two feedthrough capacitors C _a for lines.

[0019]

As described above, according to the structure of the tuner integrated with the IF board of the present invention, the tuner is constructed by using the feedthrough capacitor in the connector portion connecting the tuner board and the IF board in the single shield case. The board can be almost completely shielded, the leakage of the oscillator to the IF board can be prevented, and the deterioration of the radiation can be avoided. Moreover, since it is possible to prevent leakage of RF radiation without mounting a bypass capacitor, a line filter, or the like on the IF board,
There are advantages that the number of parts on the board can be reduced and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is an external perspective view of a shield case having a structure of an IF substrate integrated tuner of the present invention.

FIG. 2 is a perspective view showing an appearance of a feedthrough capacitor and a connection state of a tuner substrate and an IF substrate using the feedthrough capacitor.

FIG. 3 is a diagram showing an example of a circuit when a feedthrough capacitor is part of a tuning circuit.

FIG. 4 is a block diagram showing an outline of a case where a tuner board and an IF unit are connected and integrated.

FIG. 5 is a diagram showing an outline of a case where a tuner board and an IF board are connected using a connector.

[Explanation of symbols]

1 the shield case 2 tuner board 3 IF substrate 2a, 3a AGC line 2b, 3b IF line 2c, 3c supply line 4 connector _{C (C a, C b,} C c) through capacitor 10 IF double-tuned circuit 11 IF preamplifier

Claims (2)

[Claims] 1. A tuner section substrate and an IF board are arranged and integrated in a single shield case, the tuner section board and the IF board are mutually shielded by a shield plate, and the tuner section board and the IF board are integrated. A structure of an IF substrate integrated tuner, wherein the connection is made through a feedthrough capacitor provided on the shield plate. 2. The feedthrough capacitor for deriving an IF output is a part of a tuning circuit on the IF substrate side, and I
The structure of the IF substrate integrated tuner according to claim 1, wherein power is supplied through the F output line.