JPH043509A - Filter - Google Patents

Abstract

PURPOSE:To attain impedance matching with a pre-stage circuit after a package is inserted in an electronic circuit by providing a semi-fixed resistor in interlocking with an adjustment knob for impedance matching into a same package as an LC filter. CONSTITUTION:An adjustment knob 15 provided to an upper face of a package 11 is used to adjust a semi-fixed resistor in the inside of a filter externally. A semi-fixed resistor 21 connected between an input terminal lead 12 and an input coil 12a is constituted so as to be able to vary by the knob 15. Then a signal from a pre-stage circuit is inputted from the input terminal lead 12 and passes through the semi-fixed resistor 23 and an undesired signal component is eliminated by coils 21a, 21b and a capacitor 22. When impedance mis-matching takes place between the pre-stage circuit and the LC filter in the inside of the filter in the process as above, the adjustment knob 15 is turned externally to apply fine-adjustment to the semi-fixed resistor 23 to take impedance matching. Thus, the impedance matching with respect to the pre-stage circuit is easily implemented by using one component.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a filter that can be effectively used in electronic circuits in electronic equipment.

2. Description of the Related Art In recent years, filters have been widely used in electronic circuits in electronic devices to process unnecessary components of signals.

A conventional filter will be explained below.

FIG. 3 is an external view of a conventional filter, and FIG. 4 is an internal equivalent circuit of the conventional filter.

In FIG. 3, 11 is a package. Reference numeral 12 is an input terminal lead, 13 is a ground terminal lead, and 14 is an output terminal lead, which are fixed to the printed board and connected to the electronic circuit of the board.

In FIG. 4, 21a and 21b are coils, and n is a connecting lead 13 and an output terminal 14, forming an LC type filter.

The operation of the filter configured in this manner will be described above. First, it is inserted into an electronic circuit, and the signal from the previous stage circuit is inputted from the input terminal board 12 shown in FIG.
Unnecessary signal components are removed by the coil 21a 521b and capacitor η inside the filter, and only the signals necessary for the subsequent circuit are output from the output terminal lead 14.
Input the signal to the subsequent circuit.

Problems to be Solved by the Invention However, in the conventional configuration described above, impedance mismatch occurs between the front-stage circuit and the filter, and the desired signal processing cannot be performed. There was a problem in that a matching resistor had to be provided between the pre-stage circuit and the filter.

The present invention solves the above-mentioned conventional problems.

The object of the present invention is to provide an excellent filter that has a simple configuration, allows fine adjustment of the impedance with the preceding circuit, does not cause mismatch, and can be housed in a small package.

Means to solve problems The filter of the present invention solves this problem.

Just before the input side coil of a conventional LC type filter.

A semi-fixed resistor is provided that is linked to an adjustment knob for impedance matching with the previous stage circuit, and the adjustment knob and semi-fixed resistor are housed in the same cage, and the adjustment knob can be operated from the outside. This is what I did.

With this configuration, even if an impedance mismatch occurs between the pre-stage circuit and the filter when the package is inserted into an electronic circuit, the semi-fixed resistance can be adjusted by changing the adjustment knob on the package from the outside. By doing so, impedance matching can be achieved.

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

FIG. 1 is an external view of a filter in an embodiment of the present invention;
FIG. 2 shows the internal equivalent circuit of the same filter. In FIG. 1, 11 is a package. 12 is an input terminal lead, 13 is a ground terminal lead, and 14 is an output terminal lead, which are fixed to the printed circuit board and connected to other electronic circuits at the same time. 15 is package 11
An adjustment knob provided on the top surface of the filter is used to adjust the semi-fixed resistance inside the filter from the outside. In FIG. 2, 21a21b is a coil, 22 is a capacitor, and an LC type filter is formed between the input terminal lead 12, the ground terminal lead 13, and the output terminal lead 14.

Reference numeral 21 denotes a semi-fixed resistor connected between the input terminal lead 12 and the input side coil 21a, and is configured so that it can be changed by aJ using the adjustment knob 15 shown in FIG.

The operation of the filter configured in this manner will be described below. First, insert it into the electronic circuit.

A signal from the previous stage circuit is inputted from the input terminal lead 12.

The coils 21a and 2 pass through the semi-fixed resistor inside the filter.
1b and capacitor 4 remove unnecessary signal components. In the process up to this point, if an impedance mismatch occurs between the front stage circuit and the LC type filter inside the filter, the adjustment knob 15 is moved from the outside to finely adjust the semi-fixed resistor n to achieve impedance matching. Then, within the filter, only the signals necessary for the subsequent stage circuit are outputted from the output terminal lead 14 and inputted to the subsequent stage circuit.

In this way, according to this embodiment, immediately before the LC type filter,
By providing a semi-fixed resistor linked to the adjustment knob that can be adjusted from 4 parts in the same package, it is possible to
Impedance matching with the preceding circuit can be easily achieved, and unnecessary signal components can be processed.

Effects of the Invention As described above, according to the present invention, by providing a semi-fixed resistor that is linked to an adjustment knob for impedance matching in the same package as the LC type filter, after the package is inserted into an electronic circuit, the previous input - When impedance matching with the stage circuit occurs, impedance matching can be easily performed externally, and fine adjustment is possible, so it is possible to prevent deterioration of the filter effect due to impedance mismatching, and at the same time, Since no matching resistor is required, the number of components can be reduced, and
This makes it possible to realize an excellent filter that eliminates the need to attach a matching resistor after insertion.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a filter according to an embodiment of the present invention;
FIG. 2 is an internal equivalent circuit diagram of the same filter, FIG. 3 is a perspective view of a conventional filter, and FIG. 4 is an internal equivalent circuit diagram of the conventional filter. 11...Package, 12...Input terminal lead, 1
3...Ground terminal lead, 14-...Output terminal lead, 15...Adjustment knob, 21a, 21b...Coil, 22...Capacitor, 23...Semi-fixed resistor. Agent Yoshihiro Morimoto Diagram/40. Girokutachō) ')-)' A, -Threshold Flea 7 Torture Diagram

Claims (1)

[Claims] 1. A filter used in an electronic circuit, comprising an externally variable adjustment knob and an impedance matching circuit that works with the adjustment knob in the same package, and a pre-stage circuit after the package is inserted into the electronic circuit. A filter that enables impedance matching with.