JPH05347528A - Substrate lc filter - Google Patents

Abstract

PURPOSE:To improve an attenuation characteristic of the substrate LC filter. CONSTITUTION:The substrate LC filter 1 is constituted by magnetically coupling mutually LC resonance circuits theta1-theta5 in which a pair of rotation symmetrical U-shape electrode patterns 3, 3' are formed on the surface and the reverse side of a dielectric substrate 2. Electrodes 31 of the LC resonance circuits theta1-theta4 and an electrode 31' of the LC resonance circuit theta5 are grounded equivalently through a coil by lead terminals T2-T5 having an inductance portion, respectively. Also, the electrodes 31 of the LC resonance circuits theta3, theta4 are connected, and grounded equivalently by a common coil. By a ground structure of each LC resonance circuit Q1-Q5, the substrate LC filter 1 becomes a filter circuit of a polar type having equivalently an attenuation pole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention combines a plurality of capacitors formed of a pair of electrodes formed on the front and back surfaces of a dielectric substrate with a pattern coil formed on the front or back surface of the dielectric substrate. The present invention relates to a substrate LC filter in which constituent LC resonance circuits are connected in series by connecting some pattern coils of adjacent LC resonance circuits to each other.

[0002]

2. Description of the Related Art FIGS. 10A and 10B show an example of a conventional substrate LC filter. FIG. 10A is a view seen from the front side of the substrate, and FIG. 10B is a view seen from the back side of the substrate. , (C) are side views of the substrate. FIG. 11 is a circuit configuration diagram showing an equivalent circuit of the substrate LC filter.

The substrate LC filter 10 shown in FIG. 1 has four LC resonance circuits θ1 to θ1 formed by forming a pair of rotationally symmetrical U-shaped electrode patterns 3 and 3'on the front and back surfaces of a dielectric substrate 2.
It is a bandpass filter (hereinafter referred to as BPF) having a four-stage structure formed by coupling θ4 with each other. The capacitor C11 of each LC resonance circuit θ1 to θ4 is formed by the electrodes 31 and 31 ′ of the electrode patterns 3 and 3 ′ facing each other, and the coils L11 and L12 are electrodes 31 and 32, respectively.
The coil L13 is formed by the electrode 33 connecting between the electrodes and the electrode 33 'connecting between the electrodes 31' and 32 ', and the coil L13 is the electrode 3 of the electrode pattern 3 connected by the electrode 34 on the side surface 21 of the substrate.
2 and the electrode 32 'of the electrode pattern 3'.

The LC resonance circuits θ1 to θ4 are arranged with a predetermined interval S, and the electrodes 3 of one adjacent LC resonance circuit are arranged.
3 and the electrode 33 'of the other LC resonance circuit are magnetically coupled and cascaded in multiple stages. For example, the LC resonance circuit θ1 and the LC resonance circuit θ2 are the electrodes 3 of the LC resonance circuit θ1.
3 and the electrode 33 ′ of the LC resonance circuit θ2 are magnetically coupled.

Further, a pair of electrodes 4 and 5 are formed on the front and back surfaces of both ends of the dielectric substrate 2 to form external coupling capacitors C1 and C2 for output. Since the electrodes of the pair of electrodes 4 on the back surface side of the substrate are connected to the electrodes 31 'of the LC resonance circuit θ1, the electrodes 31' are expanded to a position facing the electrodes of the pair of electrodes 4 on the substrate front surface side. It has a shape. Similarly, since the electrodes of the pair of electrodes 5 on the front surface side of the substrate are also connected to the electrodes 31 of the LC resonance circuit θ5, the electrode 31 is expanded to a position facing the electrodes on the rear surface side of the substrate of the pair of electrodes 5. ing.

Input and output terminals T1 and T6 are attached to the electrode 4 forming the capacitor C1 and the electrode 5 forming the capacitor C2, respectively.
A lead terminal T for grounding is provided on each of the electrodes 31 of the C resonance circuits θ1 to θ3 and the electrode 31 ′ of the fourth stage LC resonance circuit θ4.
2 to T5 are connected.

The substrate LC filter 10 having the above structure
Equivalently has the circuit configuration shown in FIG. 11 and constitutes the BPF having the pass characteristic without the attenuation pole shown in FIG.

[0008]

In the structure of the conventional substrate LC filter described above, it is difficult to obtain a desired attenuation characteristic because the circuit structure equivalently has no attenuation poles on both sides of the pass band. ..

The present invention has been made in view of the above problems, and an object of the present invention is to provide a substrate LC filter having an equivalent circuit configuration having attenuation poles and capable of obtaining suitable attenuation characteristics.

[0010]

In order to solve the above-mentioned problems, the present invention provides a capacitor comprising a plurality of electrodes formed on the front and back surfaces of a dielectric substrate, and the front or back surface of the dielectric substrate. A substrate LC filter in which the LC resonance circuits configured by combining the pattern coils formed in the above are connected in cascade by coupling the pattern coils of the adjacent LC resonance circuits to each other. The grounded end is grounded via a coil, and at least one set of adjacent LC resonant circuits share a common coil.

[0011]

According to the present invention, in a substrate LC filter in which a plurality of LC resonance circuits are magnetically coupled to each other and connected in cascade, a ground end of each LC resonance circuit is grounded via a coil, and Since at least one pair of adjacent LC resonance circuits share a common coil, they are equivalently polar filter circuits having at least one pair of attenuation poles, and the attenuation characteristics are improved.

[0012]

FIG. 1 shows the structure of an embodiment of a substrate LC filter according to the present invention. (A) is a view from the front side of the substrate, (b) is a view from the back side of the substrate. FIG. 1C is a side view of the substrate.

In the substrate LC filter 1 shown in the figure, a pair of rotationally symmetrical U-shaped electrode patterns 3 and 3'shown in FIG. 2 are formed on the front and back surfaces of the dielectric substrate 2, and both electrode patterns 3 and 3 are formed. 'Is connected by the side surface electrode 34 of the one side surface 21 to form a five-stage bandpass filter (hereinafter, referred to as B
PF), and equivalently has the circuit configuration shown in FIG.

The U-shaped electrode pattern 3 on the substrate surface includes an electrode (hereinafter, referred to as a capacitor electrode) 31 that constitutes one electrode of a capacitor, and an electrode (hereinafter, referred to as a coil electrode) 32 that equivalently forms a pattern coil, 33, and the U-shaped electrode pattern 3'on the back surface of the substrate is composed of the capacitor electrode 31 and the coil electrodes 32 'and 33' which form the other electrode of the capacitor. A capacitor C11 is formed by the capacitor electrodes 31 and 31 'arranged on the front and back surfaces of the dielectric substrate 2 so as to face each other.
2, 32 'and the electrode 34 on the side surface 21 of the substrate connecting the electrodes 32, 32' form a coil L13, and the coil electrodes 33, 33 'form a coil L11 and a coil L12, respectively. Therefore, one LC resonance circuit θ equivalently has the circuit configuration shown in FIG.

Five LC resonance circuits θ1 to θ5 having the above-mentioned configuration
Is the coil electrodes 33, 33 'of the adjacent LC resonance circuit θ.
Are arranged on the dielectric substrate 2 with an appropriate interval S so as to be magnetically coupled to each other. Further, a pair of electrodes 4 and 5 are formed on the front and back surfaces of both ends of the dielectric substrate 2 to form external coupling capacitors C1 and C2 for output.

Since the electrode on the back surface side of the substrate which constitutes the external coupling capacitor C1 is connected to the capacitor electrode 31 'which constitutes the capacitor C11 of the first-stage LC resonant circuit θ1, the capacitor electrode 31' is externally coupled. The shape is expanded to a position facing the electrode 4 on the front surface side of the substrate forming the capacitor C1. Similarly, the electrode on the front surface side of the substrate forming the external coupling capacitor C2 is also the capacitor electrode 3 forming the capacitor C11 of the fifth-stage LC resonant circuit θ5.
Since it is connected to No. 1, the capacitor electrode 31 is expanded to a position facing the electrode 5 on the back surface side of the substrate forming the external coupling capacitor C1.

The electrode patterns 3 and 3'and the electrodes 4 and 5 of the LC resonance circuits .theta.1 to .theta.5 are formed by printing a conductive paste such as silver or copper on the front and back surfaces of the dielectric substrate 2 by screen printing, for example. However, it is more preferable to form the film by thick film etching.

In the case of screen printing, the edge portion of the electrode pattern D becomes round as shown by the solid line in FIG.
In the thick film etching, the edge portion of the electrode pattern D is better cut than in screen printing, and the edge portion can be formed at an acute angle as shown by the dotted line in FIG. In the case of screen printing, as shown in FIG.
Although it is difficult to obtain sufficient linearity of the edge portion due to unevenness in the edge portion of the electrode pattern D due to printing bleeding or the like, the thick film etching makes it possible to obtain an electrode pattern having highly accurate edge linearity. D can be formed. As a result, an LC resonant circuit having a high Q, for example, an LC resonant circuit having a Q that is 10% to 20% higher than that of a screen-printed one can be obtained, and the variation in the coupling coefficient with the adjacent electrode is small, so that the characteristics of the substrate LC filter are improved and stable. Can be planned.

Further, as shown in FIG. 2, for example, the electrode pattern 3'on the back surface of the substrate may be made slightly smaller in area so as to be included in the electrode pattern 3 on the front surface of the substrate. For example, the dimensional difference t between the electrode pattern 3 and the electrode pattern 3 ′ may be set to an appropriate value such as 0.1 mm depending on the alignment accuracy when forming the electrode pattern. By doing so, even when a positional deviation occurs during the formation of the electrode pattern, the change in the area of the electrodes to be opposed on the front and back surfaces, that is, the change in the capacitance value of the capacitor C11 is small, and the initial characteristics (adjustment) of the substrate LC filter 1 are reduced. The former characteristic), for example, the frequency characteristic is stabilized, and the workability and productivity of the subsequent assembling process are improved.

Returning to FIG. 1, input / output terminals T1 and T6 are attached to the electrode 4 forming the capacitor C1 and the electrode 5 forming the capacitor C2, respectively.
Further, the capacitor electrode 31 forming the capacitor C11 of the first and second stage LC resonance circuits θ1 and θ2 and the capacitor electrode 31 ′ forming the capacitor C11 of the fifth stage LC resonance circuit θ5 are respectively grounded. Lead terminal T
2, T3 and T5 are connected. Also, 3rd and 4th
The capacitor electrodes 31 forming the capacitors C11 of the LC resonance circuits θ3 and θ4 of the stage are connected by an electrode pattern, and the common lead terminal T4 for grounding is connected to the capacitor electrodes 31.

The lead terminals T2 to T5 are constructed to have an appropriate inductance, and each LC resonance circuit θ1
The grounding ends (points a, b, c, d, and e in FIG. 4) of .about..theta.5 are grounded via an inductance. This inductance is equivalent to the coil L1 of the equivalent circuit shown in FIG.
.About.L4, the grounding ends d and e of the third-stage LC resonant circuit .theta.3 and the fourth-stage LC resonant circuit .theta.4 are grounded by the common coil L3 having the above configuration.

FIG. 6 is a schematic diagram showing the pass characteristic of the BPF 1 having the above structure. As described above, each LC resonance circuit θ1
Grounding ends a to e of θ5 are grounded via lead terminals T2 to T5 having an inductance, coils L1 to L4 are equivalently provided between the grounding ends a to e and ground, and the LC resonance circuits θ3 and θ4 are grounded. A coil L is provided between the ends d and e and the ground.
Since 3 is shared, a pair of attenuation poles P is formed on both sides of the pass band, and it is possible to obtain a larger attenuation characteristic than the conventional substrate LC filter having no attenuation pole.

In the above embodiment, an example in which the pair of attenuation poles P is formed on both sides of the pass band is shown.
The number of the attenuation poles P can be increased by increasing the number of shared coils provided between the ground ends a to e of θ5 and the ground.

FIG. 7 shows a substrate LC in which the number of shared coils provided between the ground end of the LC resonance circuit and the ground is two.
It is a figure which shows the block diagram of an example of a filter, (a) is the figure seen from the front surface side of a board | substrate, (b) is the figure seen from the back surface side of a board | substrate, (c) is a side view of a board | substrate.

This figure shows the LC resonance circuit θ3 in FIG.
Is connected to the capacitor electrode 31 of the LC resonance circuit θ4, and the capacitor electrode 31
The configuration in which the lead terminal T4 is connected to is replaced with the following configuration.

That is, the capacitor electrode 31 of the LC resonance circuit θ2 is connected to the capacitor electrode 31 of the LC resonance circuit θ3, the lead terminal T3 is connected to the capacitor electrode 31, and the capacitor electrode 3 of the LC resonance circuit θ4 is connected.
1'is connected to the capacitor electrode 31 'of the LC resonance circuit .theta.5, the lead terminal T4 is connected to the capacitor electrode 31', and the ground lead terminal T5 is removed. As an equivalent circuit, as shown in FIG. 8, the ground ends b and c ′ of the LC resonant circuits θ2 and θ3 of the second and third stages are used.
Is grounded via a common coil L2, and the grounding ends d ', e of the fourth and fifth stage LC resonant circuits θ4, θ5 are grounded.
And the ground are grounded via a common coil L4. By thus sharing two coils provided between the ground end of the LC resonance circuit and the ground, it is possible to form two attenuation poles P on both sides of the pass band as shown in FIG.

The combination of the LC resonance circuits sharing the coil is not limited to the above-mentioned embodiment, and any two sets of adjacent L resonance circuits can be used.
By sharing the coil provided between the ground end of the C resonance circuit and the ground, two attenuation poles P can be formed on both sides of the pass band. Although the coils L1 to L4 are formed by the lead terminals T2 to T5 in the above embodiment, they may be formed by pattern coils on the front and back surfaces of the dielectric substrate 2.

In addition, although the BPF having a five-stage structure has been described in the above embodiment, the present invention is applicable to a plurality of substrates L having an arbitrary number of stages.
Substrate L other than BPF that can be applied to C filter
It can also be applied to a C filter.

[0029]

As described above, according to the present invention,
A substrate LC filter in which a plurality of LC resonance circuits are connected in series, wherein a ground end of each LC resonance circuit is grounded via a coil, and at least one set of adjacent LC resonance circuits share a coil. By doing so, a filter circuit having at least a pair of attenuation poles is equivalently configured, and the attenuation characteristics of the substrate LC filter can be improved.

[Brief description of drawings]

1A and 1B show an embodiment of a substrate LC filter according to the present invention, in which FIG. 1A is a view seen from the front surface of the substrate, FIG. 1B is a view seen from the back surface of the substrate, and FIG. Is.

FIG. 2 is a diagram showing a structure of an LC resonance circuit.

FIG. 3 is a diagram showing an equivalent circuit of an LC resonance circuit.

FIG. 4 is a diagram showing an equivalent circuit of a substrate LC filter according to the present invention.

5A and 5B show a shape of an electrode pattern formed on a dielectric substrate, wherein FIG. 5A is a sectional view and FIG. 5B is a plan view.

FIG. 6 is a schematic diagram showing pass characteristics of a substrate LC filter according to the present invention.

7A and 7B show another embodiment of the substrate LC filter according to the present invention, in which FIG. 7A is a view seen from the front surface of the substrate, FIG. 7B is a view seen from the back surface of the substrate, and FIG. It is a figure.

FIG. 8 is a diagram showing an equivalent circuit of another embodiment of the substrate LC filter according to the present invention.

FIG. 9 is a schematic diagram showing characteristics of another embodiment of the substrate LC filter according to the present invention.

FIG. 10 shows a structure of a conventional substrate L filter,
7A is a view seen from the front surface of the substrate, FIG. 8B is a view seen from the back surface of the substrate, and FIG.

FIG. 11 is a diagram showing an equivalent circuit of a conventional substrate LC filter.

FIG. 12 is a schematic diagram showing pass characteristics of a conventional substrate LC filter.

[Explanation of symbols]

 1, 1'Substrate LC filter 2 Dielectric substrate 3, 3 ', D Electrode pattern 4, 5 Electrode 31, 31', 32, 32 'Capacitor electrode 33, 33', 34 Coil electrode T1, T6 Input / output terminal T2 To T5 lead terminals C1, C2, C11 capacitors L1 to L4, L11, L12 coils θ, θ1 to θ5 LC resonant circuit P attenuation pole

Claims (1)

[Claims] 1. An LC resonance circuit configured by combining a plurality of capacitors, each of which includes a pair of electrodes formed on the front and back surfaces of a dielectric substrate, and a pattern coil formed on the front or back surface of the dielectric substrate. Is a substrate LC filter in which pattern coils of adjacent LC resonance circuits are coupled to each other and are connected in cascade, wherein the ground end of each LC resonance circuit is grounded via the coil, and at least one set of A substrate LC filter, wherein adjacent LC resonance circuits share a common coil.