JPH04142798A - High frequency device - Google Patents

Abstract

PURPOSE:To improve a high frequency device in signal-to-noise ratio (S/N) by a method wherein a power feed lead terminal exposed outside of a shield case and a wiring material connected to the terminal concerned are reduced to a minimum. CONSTITUTION:A secondary circuit board 1 is mounted on a shield case 3 vertical to a primary circuit board 7. A lead terminal 4 is horizontally connected to the secondary circuit board 1 penetrating the base of the shield case 3 in contact with the primary circuit board 7. The lead terminal 4 is connected to a conductor pattern 13 formed on the rear of the primary circuit board 7 passing through a through-hole 8 provided to the primary circuit board 7. A feed-through capacitor 5 is provided to the through-hole provided to the base of the shield case 3 so as to prevent the penetration of induction noises caused by an adventitious magnetic field 9 from penetrating through the intermediary of a lead terminal 4. A bypass capacitor 12 is connected between the conductor pattern 13 and a grounding conductor so as to remove noises which overlap a power supply voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) This invention relates to a high frequency device used in an optical repeater or the like.

(Prior Art) Generally, in an optical repeater, a high frequency section for transmitting and receiving optical signals is separated from other circuit sections, and a shielded high frequency device is mounted on a main circuit board.

Mounting High Frequency Circuit Components FIG. 2 shows a conventional high frequency optical receiving device mounted on a main circuit board.

A signal output end of a light receiving element (photodiode, etc.) 2 is connected to an input end of the sub-circuit board 1 .

The sub-circuit board 1 is equipped with a preamplifier circuit device 11 that amplifies a minute signal of several millivolts output from the light-receiving element 2 . A core wire of a coaxial connector 6 is connected to the signal output end of the sub-circuit board 1 so that the output from the preamplifier circuit device 11 is supplied.

The sub-circuit board 1 is housed in a shield case 3 to prevent intrusion of induced noise due to an external magnetic field 9, and the light-receiving element 2 and coaxial connector 6 are respectively attached to opposing sides of the shield case 3 and grounded to each other.

The sub circuit board 1 covered with the shield case 3 in this way is
It is mounted horizontally to the main circuit board 7 together with other circuit components.

Here, a plurality of lead terminals 4 for supplying power to the preamplifier circuit device 11 are connected to the sub-circuit board 1 . These lead terminals 4 penetrate the side surface of the shield case 3 and are exposed to the outside, and the tip ends are connected to the power supply on the back side through the through holes 8 of the main circuit board 7 through the wiring material 10. It is connected to the supply conductor pattern 13. A feedthrough capacitor 5 is provided in a penetration portion on the side surface of the shield case 3. This is to prevent intrusion of induced noise due to the external magnetic field 9 etc. transmitted via the lead terminal 4.

Although not shown in detail, a bypass capacitor 12 is connected between the conductive pattern 13 and the ground conductor, thereby eliminating noise superimposed on the power supply voltage.

(Problem to be solved by the invention) However, according to the above-mentioned conventional high-frequency device, the sub-circuit board 1 is mounted horizontally, so although the height of the device can be kept relatively low, the sub-circuit board 1 is mounted horizontally. The sub circuit board 1 is connected to the conductor pattern 13 of the main circuit board 7.
One end of the lead terminal 4 connected horizontally to the terminal had to be pulled out and connected to the terminal using a wiring material, or the lead terminal had to be bent at right angles and inserted into a through hole and soldered.

In this case, since the exposed portion of the lead terminal acts as an antenna, induced noise due to the external magnetic field will enter the shielding case via the lead terminal.

Conventionally, the filtering effect of feedthrough capacitors has been used to reduce the induced noise entering the shield case to some extent, or the signal-to-noise ratio (S/N ) was markedly reduced.

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-frequency device with a good signal-to-noise ratio (S/N) even when the intensity of an external noise electromagnetic field is large.

[Structure of the Invention] (Means for Solving the Problem) The present invention provides a main circuit board for the sub-circuit board so that a group of lead terminals connected to the sub-circuit board protrudes from the bottom surface of the shield case that is in contact with the main circuit board. The shield case is mounted perpendicularly to the bottom surface in contact with the circuit board.

(Function) In the high frequency processing with the above configuration, the sub circuit board and the main circuit board mounting surface are built into the shield case so that they are perpendicular to each other, and the lead terminals are made to protrude vertically from the bottom of the case, and the exposed parts of the lead terminals are This is done to minimize the noise caused by external magnetic fields that enter the shield case through the lead terminals.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the invention.

Note that the same parts as in FIG. 2 will be described with the same reference numerals.

The sub-circuit board 1 described above in FIG. 2 is attached to the shield case 3 so as to be perpendicular to the main circuit board 7.

The lead terminals 4 connected horizontally to the sub circuit board 1 penetrate the bottom surface of the shield case 3 in contact with the main circuit board 7, pass through the through holes 8 of the main circuit board 7, and connect to the main circuit board 7.
It is connected to a conductor turn 13 formed on the back surface of the .

A feedthrough capacitor 5 is provided in a penetration portion of the bottom surface of the shield case 3 in order to prevent intrusion of induced noise due to an external magnetic field 9 and the like transmitted via the lead terminal 4. Furthermore, a bypass capacitor 12 is connected between the conductor pattern 13 and a ground conductor (not shown) in order to remove noise superimposed on the power supply voltage.

According to the above configuration, the lead wire 4 connected to the sub-circuit board 1 can be led directly to the through hole 8 without being exposed to the outside. Therefore, the portion of the lead terminal 3 exposed to the outside of the shield case 3 can be minimized, and the intrusion of induced noise due to external magnetic fields etc. can be prevented.

In addition, due to the synergistic effect with the effect of the feedthrough capacitor 5 described above, it is possible to completely prevent induced noise from entering the shield case 3, thereby preventing a decrease in the signal-to-noise ratio (S/N).

[Effects of the Invention] As explained above, according to the present invention, by minimizing the power supply lead terminal exposed outside the shield case and the wiring material connected thereto, the intensity of external noise electromagnetic field can be reduced. Even when large, the signal-to-noise ratio (S/
N) A good high frequency device can be provided.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a high frequency device according to the present invention, and FIG. 2 is a diagram showing a conventional high frequency device. DESCRIPTION OF SYMBOLS 1... Sub circuit board, 2... Light receiving element, 3... Shield case, 4... Lead terminal, 5... Feedthrough capacitor, 6... Coaxial connector, 7... Main circuit board, 8・
...Through hole, 9...External magnetic field, 10...Wiring material, 11...Amplification circuit, 12...Bypass capacitor,
13... Conductor pattern. Applicant's agent Patent attorney Takehiko Suzue Figure (b) Figure (b)

Claims (2)

[Claims] (1) A sub-circuit board on which high-frequency circuit components are mounted, a shield case that houses this sub-circuit board and shields it from magnetism;
A group of lead terminals having one end connected to the sub-circuit board and protruding horizontally from the board to the outside of the shield case are mounted on the main circuit board, and the other end of the lead terminal group is connected to the main circuit board. In a high frequency device connected to a wiring section, the sub circuit board is mounted on the shield case with the sub circuit board perpendicular to the bottom surface so that the lead terminal group protrudes from the bottom surface of the shield case in contact with the main circuit board. A high frequency device characterized by: (2) In the high frequency device, a light receiving element that receives an external optical signal is attached to the side surface of the shield case, and a preamplifier circuit device that amplifies the output signal from the light receiving element is attached to the sub circuit board. The high frequency device according to claim 1, characterized in that: