JPH0753300Y2 - Substrate LC filter - Google Patents

Description

[Detailed Description of the Invention] Industrial Application The present invention relates to an LC filter using a dielectric substrate, and more specifically, a plurality of LC resonance circuits formed by combining a capacitor and a coil pattern on the dielectric substrate arranged in a line on the substrate. The present invention relates to a substrate LC filter in which adjacent resonance circuits are coupled by a conductive pattern of a part of the resonance circuits which are adjacent to each other via a dielectric substrate.

Prior Art FIG. 3 shows an example of a conventional substrate LC filter. Figure (a)
Is a view from the front side of the substrate, and FIG. 6B is a view from the back side of the substrate. This filter has a structure in which a plurality of U-shaped conductive patterns 2, 3, 4, ... Each U-shaped pattern 2,3,4 ... is a pattern in which two capacitor electrode patterns 21,22,31,32,41,42 ... 91,92 are connected by a coil pattern 23,33,43, ... 93. The capacitor electrode patterns 21, 22 ... Are opposed to each other between the U-shaped patterns on the front and back sides to form a capacitor. The coil patterns 23, 33 ... Function as coils for connecting two capacitors. Therefore, another capacitor is connected in parallel to the LC series circuit in which a coil is connected to both ends of one capacitor by a pair of U-shaped patterns (2 and 3), (4 and 5) ... Configure the LC resonant circuit of the configuration.

Further, since the coil patterns 23, 33 ... Of each resonance circuit are close to the coil pattern of the adjacent resonance circuit via the substrate,
The two resonance circuits are magnetically coupled by the two coil patterns adjacent to each other. Therefore, the substrate LC filter having the above structure constitutes a filter having an equivalent circuit shown in FIG.

Problems to be Solved by the Invention By the way, the distance t between the coil patterns 23, 33 ... Of the adjacent resonance circuits determines the coupling coefficient between the resonance circuits, which is important in filter characteristics. I don't want to change much. However, the U-shaped patterns 2, 3, 4, ... Are formed by screen-printing the front and back surfaces of the substrate.
It is unavoidable in manufacturing that screen printing on the front surface and the back surface of the substrate deviates slightly in the lateral direction. Therefore, there is a problem that the coupling coefficient between the resonance circuits is sensitively affected. For example, the interval t between two coil patterns
If the design value of is 0.5mm but it actually becomes 0.4mm, the coupling coefficient will change from 7.4% to 8%,
Variations in filter characteristics increase.

Even if the capacitor is composed of discrete parts, such a structure can be expected if adjacent resonance circuits are connected by a part of the conductive pattern of the resonance circuit that is adjacent via the dielectric substrate. I can say.

In view of these problems, the present invention has a novel structure that does not significantly affect the coupling coefficient even if the conductive patterns on the front and back surfaces of the substrate are laterally displaced due to manufacturing errors.
The purpose is to provide an LC filter.

Means for Solving the Problems In order to achieve the above-mentioned object, the present invention provides a plurality of LC resonant circuits formed on a dielectric substrate by combining a capacitor and a coil pattern on the substrate, and adjacent resonant circuits are made of a dielectric material. In a substrate LC filter that is magnetically coupled by a conductive pattern of a part of a resonance circuit that is close to the substrate, at least one surface of a dielectric substrate and adjacent two
It is characterized in that a coupling electrode is formed so as to be isolated at a position magnetically coupled to any of the conductive patterns of one resonator.

Operation The operation of the present invention will be described with reference to FIG. In the figure, S is a dielectric substrate, α and β are parts of adjacent resonance circuits, respectively, and a conductive pattern γ that is adjacent to connect both resonance circuits is a coupling electrode newly provided by the present invention. As described in the section of the prior art, since the pattern is formed on the front and back surfaces of the substrate by screen printing or the like, the distance between the two conductive patterns α and β may be larger or smaller than the design value. However, for the reason described below, the coupling coefficient of the two resonance circuits does not change much to the left due to the presence of the coupling electrode. Hereinafter, the cases will be described separately.

(A) When the interval between α and β is larger than the design value.

In this case, the direct magnetic coupling coefficient Kαβ between α and β becomes small, but as the distance between α and β increases, the broken line connecting α and β approaches the horizontal line, and γ relatively approaches the broken line (in other words, , Γ and the distance between the broken lines become shorter), the magnetic coupling (Kαγ, Kγβ) between α and β via γ becomes stronger,
As a whole, the degree of magnetic coupling between α and β is suppressed.

(B) When the interval between α and β becomes smaller than the design value.

In this case, Kαβ becomes large contrary to the case of (a), but since the broken line connecting α and β approaches the vertical line, the distance between γ and the broken line becomes long, and between α and β via γ Magnetic coupling weakens. Therefore, the degree of magnetic coupling between α and β as a whole is suppressed.

Embodiment FIG. 1 shows an example of a substrate LC filter of the present invention. The basic structure of this filter is the same as that of the conventional example shown in FIG. 3, and a U-shaped conductive pattern is formed on both sides of the dielectric substrate 1.
Two, three, four ... 9 are formed. And, the U-shaped conductive patterns 2 to 9 are two capacitor electrode patterns 2
1,22,31,32 ... 91,92 are connected by one coil pattern 23, ... 93, and a pair of U-shaped conductive patterns (2 and 3) (4 and 5) facing each other on the front and back surfaces of the substrate. ... equivalently constitute a resonant circuit in which another capacitor is connected in parallel to an LC series circuit in which coils are connected to both sides of one capacitor.

The coil patterns 23, ... 93 of each resonance circuit are close to the coil pattern of the adjacent resonance circuit via the substrate 1 and magnetically couple the two resonance circuits. Further, on one surface of the substrate 1, coupling electrodes 11 ... Which are magnetically coupled to the coil patterns 23, 33 ... Are provided. Each coupling electrode 11 ... is an isolated electrode having an appropriate size, and is a position that is magnetically coupled to both coil patterns (23, 53) (43, 73) (63, 93) that are adjacent to each other between two resonance circuits. Is selected. In the embodiment, one coil pattern 53, 73, 93 and the substrate 1 are sandwiched between the two positions so that they face each other, and a rectangular coupling electrode is formed there. The coupling electrode is formed by screen printing and is formed simultaneously with the U-shaped conductive pattern. In the figure, 101 and 102 are electrodes for extracting input / output terminals, and these are capacitively coupled to the extended electrode portions of the capacitor patterns 32, 82 closest to the input and output via the substrate. Also 103-108
Is a lead terminal, of which 104 to 107 are ground lead terminals, 103 is an input lead terminal, and 108 is an output lead terminal.

Although the coupling electrode 11 is formed only on one surface of the substrate 1 in this embodiment, it may be formed on the other surface.

The configuration of each resonance circuit in the filter is not limited to that of the embodiment, and it goes without saying that various known resonance circuits can be used.

Effect of the Invention Since the substrate LC filter according to the present invention is configured as described above, even if the formation positions of the conductive patterns on the front and back surfaces of the substrate deviate from the design values, the magnetic coupling coefficient between adjacent resonant circuits is The presence of the electrodes results in a filter whose variation is suppressed and thus the coupling coefficient is less affected by fabrication accuracy.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a substrate LC filter of the present invention,
FIG. 2 is a diagram for explaining the operation of the present invention, FIG. 3 is a diagram showing a conventional substrate LC filter, and FIG. 4 is an equivalent circuit diagram thereof. 1 …… Dielectric substrate, 2,3,4 …… U-shaped conductive pattern, 2
1,22,31,32 …… 91,92 …… Capacitor electrode pattern, 23,
33 …… 93 …… Coil pattern, 11 …… Coupling electrode.

Claims (1)

[Scope of utility model registration request] 1. An LC resonance circuit formed by combining a capacitor and a coil pattern on a dielectric substrate is provided in a plurality of rows on the substrate, and adjacent resonance circuits are part of a resonance circuit that are adjacent to each other via a dielectric substrate. In a substrate LC filter that is magnetically coupled by a conductive pattern, at least one surface of a dielectric substrate is isolated and coupled to a position that is magnetically coupled to any of the conductive patterns of two adjacent resonators. A substrate LC filter having electrodes formed thereon.