JPH0230824Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a high frequency circuit device including a trimmer capacitor, such as an RF converter in the UHF band.

(b) Prior Art When viewing reproduced images on a video tape recorder (VTR), it is common to convert the reproduced signal into a high-frequency signal similar to a broadcast signal and then supply it to a television receiver. Therefore, the baseband video signal is converted to a high frequency signal using an RF converter. Furthermore, in PAL VTRs mainly used in Western Europe, signals are often converted to UHF band signals (30-39cH).

Therefore, the RF converter is equipped with a carrier wave signal oscillator, and there is a UHF oscillation circuit as shown in FIG. This circuit is a λ/2 type distributed constant type Colpitts circuit with a grounded base.
_T1 is a transformer coil that supplies the injection voltage of the oscillation circuit to the next stage double balance mixer (not shown). L ₁ is a pick-up,
L ₃ is a high frequency chiyoke coil, L ₂ is a resonant conductor, C ₁ ,
C ₂ is the terminal capacitance of the λ/2 distributed constant circuit.

C ₃ is a tuning capacitor for adjusting the oscillation frequency, R ₁ , R ₂ ,
R ₃ , R ₄ are bias resistors, C ₅ , C ₆ , C ₇ are bypass capacitors for high frequency grounding, Tr is a transistor,
C ₄ is the feedback capacitance.

When this type of oscillation circuit is actually constructed, it is as shown in FIG. 6 (Utility Model Application No. 58-58390). A cylinder capacitor 2, which is a tuning capacitor, is fixed to the shield case 1 by soldering, and is grounded at the same time. A resonant conductor L ₂ is connected to the cylindrical portion 2 a of the cylinder capacitor 2 . The other circuit elements of the oscillation circuit are connected by aerial wiring as shown. By attaching the lid 3, the shield case 1 completely surrounds the oscillation circuit, and is not influenced by other circuits on the printed circuit board 4, that is, other circuit parts of the RF converter.

However, when the cylinder trimmer 2 is used as a tuning capacitor as shown in Fig. 6, it is structurally necessary to fix it to the shield case 1, and the connection to the resonant conductor _L2 is also cylindrical, making the work difficult. . As a result, assembly workability was poor. Furthermore, the safety of installing the cylinder trimmer was also poor.

(c) Purpose of the invention This invention was created in view of the above points,
It is an object of the present invention to provide a high frequency circuit device having a trimmer capacitor in which workability for installing a trimmer capacitor is improved and the trimmer capacitor can be stably fixed.

(b) Structure of the invention The present invention provides a high frequency circuit device in which a circuit part including a trimmer capacitor is disposed on a part of a printed circuit board, and is provided with a shielding means for shielding the circuit part. a shaft that is rotatably supported by a substrate and has an adjustment section at its tip and a small diameter portion near the tip; a rotor electrode fixed to the shaft; and a stator fixed to the insulating substrate and opposed to the rotor electrode. an electrode; a ground terminal connected to the shaft;
a stator terminal having a connection protrusion connected to the stator electrode and connected to another circuit element;
The trimmer capacitor is fixed by connecting and fixing the ground terminal and the stator terminal to the printed circuit board, and the shield means includes at least a side surface portion that shields the circuit portion on the printed circuit board, The high frequency circuit device is characterized in that it includes a ground spring that engages one side surface and the other side surface and clamps the small diameter portion of the shaft.

(e) Examples An embodiment of the present invention will be described below with reference to the drawings.

1 and 2 are a plan view and a side sectional view showing an embodiment. A circuit constituting an RF converter is formed on the printed circuit board 10, and a portion of the circuit board 10 further has an oscillation circuit formed thereon. The oscillation circuit part is shown in a circuit diagram as shown in Figure 5 above, and Figure 1 shows the trimmer capacitor C ₃ , resonant conductor L ₂ , and pick-up loop for ease of viewing.
L ₁ is shown.

The trimmer capacitor _C3 has the shape shown in the perspective view of FIG. 11 is an insulating substrate made of alumina, and a shaft 13 to which a plurality of rotor electrodes 12 are fixed is rotatably supported perpendicularly to the substrate 11. Reference numeral 14 denotes a plurality of stator electrodes, which are fixed to the insulating substrate 11 so as to face the plurality of rotor electrodes 12 and so as not to hinder rotation of the shaft. A groove 13a is formed at the tip of the shaft 13, which is an adjustment portion that is engaged by an adjustment means such as a screwdriver when adjusting the oscillation frequency. Furthermore, a small diameter portion 13b is formed near the tip.

15 is connected to the shaft 13;
The ground terminal extends in the opposite direction.
Further, 16 is a stator terminal connected to the stator electrode 14 and also extending in the opposite direction to the shaft 13. The stator terminal 16 is provided with a pair of connection protrusions 16a to facilitate soldering with the resonant conductor _L2 .
16a is formed.

The trimmer capacitor _C3 is connected and fixed to the printed circuit board 10 together with the resonant conductor _L2 and the pickup coil _L1 . That is, the ground terminal 15 and stator terminal 16 are inserted into the printed circuit board, and connected and fixed to the pattern on the back side by soldering. Regarding the resonant conductor L ₂ and pick-up loop L ₁ , and although not shown, the capacitors C ₁ , C ₂ ,
The same applies to the chiyoke coil _L3 . One end of the resonant conductor L ₂ is connected to a pair of connecting protrusions 16 as described above.
It is placed or clamped on a and soldered. Further, the resonant conductor _L2 is bent as shown in the figure in order to shorten the length in the direction of the arrow in FIG. 1, and a protrusion 20 is inserted into a hole in the printed circuit board for stability.

A ground terminal 15 of the trimmer capacitor _C3 is connected to a ground pattern on the printed circuit board 10 and a side surface 17 of a shield case, which will be described later. In the connection between the resonant conductor L ₂ and the trimmer capacitor C ₃ ,
The reason why the connection is not made through the pattern on the printed circuit board 10 is that when one end of a resonant conductor whose length is determined according to the oscillation frequency is connected to the printed circuit board, the space in the direction of the arrow in Fig. 1 is taken up by that amount. This is because it is necessary and because it is a high frequency circuit, direct connection will improve stability.

Reference numeral 17 denotes a side surface of a shield case that shields the circuit portion on the printed circuit board 10 of the oscillation circuit portion. After the side part 17 is inserted into the printed circuit board 10,
Soldered to the ground pattern. As shown in FIG. 2, a portion also protrudes from the pattern side, and by soldering a shield plate (not shown) to this portion, the pattern side of the printed circuit board 10 is shielded. Also, trimmer capacitor _C3
As in the conventional example shown in FIG.
7 will be installed. This lid has a trimmer capacitor
A through hole is provided through which the adjustment section of _C3 faces.

Other circuit elements such as the transistor Tr are connected and fixed to the pattern surface side of the printed circuit board 10 as chip components. Therefore, in this embodiment, there is no aerial wiring of circuit elements, and the work of configuring the oscillation circuit can be substantially automated. This is due to the adoption of the above structure as the shield case.

The side surface 17 of the shield case has a notch 17a and a through hole 1 in which a pair of earth springs 18, 18 engage.
7b are formed on the side surfaces 17c and 17d, respectively. This earth spring 18 is trimmer capacitor C ₃
It fits into the small diameter portion 13b of the shaft 13 and clamps the shaft 13. This allows the trimmer capacitor C ₃
is grounded to the shield case near the adjustment section, and the ground potential around the trimmer capacitor is kept uniform (shaft 13 is held in the proper position). Also, it provides an appropriate amount of friction against the rotation of shaft 13. (See Figure 4, a perspective view showing the relationship between the shaft and the earth spring shield case).

In the above-mentioned RF converter, the transmission channel is selected by adjusting the trimmer capacitor _C3 according to the area in which the VTR user uses the VTR. Therefore, trimmer capacitor _C3 can be adjusted from outside the RF converter. Since the adjustment is performed by a general user, a metal driver may be used. Even in this case, since the trimmer capacitor _C3 is grounded near the adjustment section, the oscillation frequency does not change between when adjusting and when the driver is released, resulting in stabilization of the oscillation frequency and resettability when adjusting the frequency. has been improved.

(f) Effects of the invention As described above, according to the invention, since the trimmer capacitor is fixed to the printed circuit board, and the shaft is clamped by the earth spring, the fixed state is stable, and connection protrusions with other circuit elements can be prevented. Connection is easy because stator terminals are provided.

[Brief explanation of the drawing]

Figures 1 to 5 relate to one embodiment of the present invention;
2 is a plan view, FIG. 2 is a side sectional view, FIG. 3 is a perspective view of the trimmer capacitor, FIG. 4 is a partial perspective view, and FIG. 5 is a circuit diagram. FIG. 6 is an exploded perspective view showing a conventional example. 10...Printed circuit board, _C3 ...trimmer capacitor, 11...insulating board, 12...rotor electrode,
13... Shaft, 13a... Groove, 13b... Small diameter portion, 14... Stator electrode, 15... Earth terminal, 16... Stator terminal, 17... Side part of shield case, 18... Earth spring.

Claims (1)

[Claims for Utility Model Registration] A high frequency circuit device in which a circuit part including a trimmer capacitor is disposed on a part of a printed circuit board, and a shielding means for shielding the circuit part is provided, wherein the trimmer capacitor includes an insulating substrate and the insulating substrate. a shaft that is rotatably supported by the shaft and has an adjustment section at its tip and a small diameter portion near the tip; a rotor electrode fixed to the shaft; and a stator electrode fixed to the insulating substrate and facing the rotor electrode. and a ground terminal connected to the shaft;
a stator terminal having a connection protrusion connected to the stator electrode and connected to another circuit element;
The trimmer capacitor is fixed by connecting and fixing the ground terminal and the stator terminal to the printed circuit board, and the shield means includes at least a side surface portion that shields the circuit portion on the printed circuit board, A high frequency circuit device comprising a ground spring that engages one side surface and the other side surface and clamps the small diameter portion of the shaft.