JPH04207707A - Lc filter - Google Patents

Abstract

PURPOSE:To widen the attenuation band, and also, to sharpen the cut-off frequency characteristic by forming a coil by a spiral inductor conductor provided on one or both sides of a capacitor formed by plate-like conductors opposed by inserting and holding a dielectric layer between, and also, utilizing the floating capacity generated between them. CONSTITUTION:The LC filter consists of plate-like (solid-like) capacitor conductors 11, 12 placed on both sides of a dielectric layer 4, and a first inductor conductor 21 and a second inductor conductor 22 like a spiral placed on both sides of the capacitor conductors 11, 12 through an insulator layer 33 or 34. Also, the capacitor conductor 11 is connected in series between the inductor conductors 21, 22, and to both its ends, a signal input terminal 51 and a signal output terminal 61 being signal terminals are connected, and also, the other capacitor conductor 12 is connected to an earth terminal 71. A dielectric layer 4 is formed to a film whose thickness is about 30mum by screen printing by using composite ceramics of boro-silicated glass and lead titanate (PbTiO3).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an LC filter used in signal passing circuits, power supply circuits, etc. in electronic equipment.

[Prior art]

As shown in FIG. 7, the C filter 9 has a pair of signal line lead terminals 95 and 96 connected to one electrode portion 91 disposed on a disk-shaped capacitor 93. Also, the other electrode on the opposite side of the capacitor 93 (
(at the time of illustration), a ground terminal 94 is connected. The above LC filter 9 is.

Since it has three terminals, it is called a three-terminal LC filter.

As shown in the figure, the lead terminals 95 and 96 are provided in order to increase the inductance.

Ferrite beads 98 are inserted. Also.

The capacitor 93 and the electrode section 91 are coated with an insulating overcoat layer (not shown).

As shown in FIG. 8, the three-terminal type LC filter 9 has an equivalent circuit in which a capacitor C and a pair of inductors L1 and L2 are connected in a T-shape. The inductor L has an input terminal 5 at one end, and an output terminal 6 at the other end. Further, the capacitor C is connected to the ground terminal 7.

[Division trying to solve! ! ! ] However, the above prior art has a third problem.

That is, the conventional LC filter 9 has lead terminals 95.95
Since the ferrite bead 98 is inserted into the ferrite bead 98, it has to be manufactured using a combination of different materials, which is expensive. Also,
Since the shape becomes larger due to the insertion of the ferrite beads 98, a large mounting space is required when mounting on a circuit board or the like. Therefore, it cannot meet the demand for miniaturization of electronic components.

On the other hand, as shown in FIG. 5, the attenuation characteristic of the LC filter 9 is shown by a simple attenuation curve having one attenuation pole Z.

Further, in the LC filter 9, the $i attenuation (effective frequency region) does not increase much. Further, as shown in FIG. 6, the impedance of the LC filter 9 is low in the high frequency region. Therefore, the LC filter 9 cannot be used in a wide frequency range, for example 500M to IG.

The present invention has been made in view of such conventional problems, and aims to provide a compact LC filter that has characteristics represented by an attenuation curve consisting of two or more attenuation poles and a wide attenuation width. It is something.

[Means for solving problems]

The present invention comprises a flat capacitor conductor placed on both sides of a dielectric layer, and a spiral inductor conductor placed on one or both sides of the capacitor conductor with an insulating layer interposed therebetween. is connected in series with the inductor conductor, signal terminals are connected to both ends thereof, and the other capacitor conductor is connected to a ground terminal.

In the present invention, the inductor conductor is made of a metal such as silver, gold, copper, silver/palladium, or the like.

For example, it is formed by thick film printing using a conductor paste containing these metal powders. Alternatively, these metals can be vapor-deposited,
It is formed on an insulating layer by sputtering or the like. Also,
The capacitor conductor is formed on both sides of the dielectric layer in the same manner as the inductor conductor.

Then, one of the capacitor conductors is connected in series with the inductor conductor, and signal terminals are connected to both ends thereof. In this case, the capacitor conductor is connected in series to only one side of the inductor conductor (Figs. 3 and 4), and the capacitor conductor is connected in series between the inductor conductors (Fig. 1, 2, 2). Figure). Also, the other capacitor conductor is connected to the ground terminal.

Furthermore, the inductor conductor is formed in a spiral shape. On the other hand, the conductor for capacitors is flat (hetagonal).
to form. Then, an insulating layer is interposed between the inductor conductor and the capacitor conductor. Further, a pair of capacitor conductors are provided on both sides of the dielectric layer.

Next, the dielectric layer is made of borosilicate glass and lead titanate (P).
It is preferable to use a composite ceramic consisting of bT i Ox ).

Further, the dielectric layer is preferably a film formed by screen printing and having a thickness of 20 to 80 μm.

Further, the insulator layer is made of Ca OA, which is a low temperature firing material.
It is preferable to use a composite ceramic made of l1zOxSiOx-BzO*-based glass and alumina (Alzo). Since this material can be fired at a low temperature, a low resistance conductor such as silver or copper can be used for the internal conductor. Further, L (reactance) can be increased by mixing ferrite powder into these insulating layers. Moreover, it is preferable that the said insulating layer is comprised by the ceramic green sheet for low temperature firing board|substrates with a thickness of 0.05-0.3 m. This has the effect of having practical strength as a flat chip.

In addition, the above ceramic green sheet is heated at 1000°C.
Ceramic and crystal glass that can be fired with:

It is made of a material containing one or more types of insulator layer materials such as alumina.

[Operations and Effects] In the LC filter according to the present invention, a capacitor is formed by both of the above-mentioned flat capacitor conductors facing each other with a dielectric layer in between, and a spiral inductor conductor provided on one or both sides of the capacitor forms a capacitor. It forms a coil and actively utilizes the stray capacitance generated during this time. This forms two or more attenuation poles and widens the attenuation band.

Moreover, the cutoff frequency characteristic can be made sharp (FIG. 5, solid line).

Further, the inductor conductor and the capacitor conductor are laminated with a dielectric layer and an insulator layer interposed therebetween, as described above. Therefore, by changing the thickness and material of the dielectric layer and the insulating layer, the capacitance can be increased or decreased, and the capacitance and attenuation characteristics of the entire LC filter can be arbitrarily set.

In one aspect of the present invention, a thin dielectric layer is used.

Since an insulating layer is used and the dielectric material is also formed by thin thick film printing, the overall thickness of the LC filter can be reduced. Therefore.

The LC filter can be easily made compact.

As described above, according to the present invention, inductance, which could not be obtained freely due to the small size of the conventional device, can be increased.

It has large insertion loss and wide attenuation band. A compact LC filter with sharp cutoff frequency characteristics can be provided.

〔Example] First example Regarding the LC filter according to the embodiment of the present invention.

This will be explained using FIGS. 1 and 2.

That is, in the three LC filters, as shown in FIG. 2, the first inductor conductor 21. an inductor L, L, consisting of a second inductor conductor 22, and a capacitor conductor 11.
12 of the capacitor C1 form a T-shaped equivalent circuit.

As shown in FIG. 1, the LC filter includes flat plate-shaped (hetagonal) capacitor conductors 11.12 arranged on both sides of the dielectric layer 4, and the capacitor conductors 11.12.
It consists of a spiral-shaped first inductor conductor 21 and a second inductor conductor 22 arranged on both sides of the inductor with an insulating layer 33 or 34 in between.

The capacitor conductor 11 is connected in series between the inductor conductors 21 and 22, and has a signal input terminal 51 as a signal terminal and a signal output terminal 6 at both ends.
1 and the other capacitor conductor 12 is connected to the ground terminal 71.

Further, the dielectric layer 4 is made of borosilicate glass and lead titanate (
A film having a thickness of approximately 30 μm is formed by screen printing using composite ceramics with PbTi03), and is formed on the insulating layer 34 on which the conductor 12 for the capacitor is formed. Then, the dielectric layer 4
By thick film printing using a conductive paste containing Ag powder on top of the .

The above-mentioned conductor 11 for the capacitor is formed.

The first inductor conductor 21 has Ag on the insulator layer 33.
It is formed by thick film printing using conductor paste containing powder. Further; the insulator layer 33 is made of CaOAlz Oy S
iO□-B20. system glass and AN20. A ceramic green sheet made of composite ceramics with a thickness of approximately 0.
．． It is formed on a 25° substrate.

Further, the second inductor conductor 22 is formed on the insulator layer 35 in the same manner as the first inductor conductor 21. The rest of the structure is the same as that of the insulator layer 33.

Further, on the insulator layer 33, insulator layers 32 and 31 similar to this are laminated. On the other hand, a similar insulator layer 36 is laminated below the insulator layer 35 as well. And these insulator layers 31-36.

A signal input terminal 51 and a signal output terminal 61 each made of a conductor are provided at both ends. In addition, 2 the insulators Fi31-3
6 is provided with a ground terminal 71 made of a conductor at one end in the center.

Further, the capacitor conductor 11 and the first and second inductor conductors 21.22 are connected to the signal circuit 41°211.22.
1 and connected in series by a signal conductor 24. Also,
The capacitor conductor 12 is as follows.

One end 121 thereof is connected to the ground terminal 71. Moreover, the center terminal 212 of the first inductor conductor 21 is.

Through hole 23. A signal circuit 321 formed on the insulator layer 32. It is connected to the signal input terminal 51 via the signal conductor 55.

Further, the center terminal 222 of the second inductor conductor 22 is connected to the signal circuit 3 formed on the insulator layer 36 laminated below.
61 through a through hole 26. Further, the signal circuit 361 is connected to the signal output terminal 6I via the signal conductor 65.

The insulator layers 31 to 36 are laminated into an integral layer,
They are integrated by firing at a low temperature of about 900°C.

Thereby, a plate-shaped LC filter in which the insulator layers 31 to 36 are integrally fired at a low temperature is obtained. Also.

As shown in FIG. 2, the LC filter includes an inductor Ls consisting of the first and second inductor conductors 21 and 22,
A T-shaped equivalent circuit is formed by a capacitor C1 consisting of L- and two capacitor conductors 11 and 12 connected to the ground terminal 71.

Next, nine effects will be explained.

In the LC filter according to this example, the dielectric layer 4
Capacitor conductors 11 and 12 in the shape of capacitors facing each other with
The side conductors form a capacitor, and a spiral first conductor is formed on both sides of the capacitor. The second inductor conductors 21 and 22 are arranged to form an inductor, and the distributed capacitance generated between them is actively utilized.

Thereby, as shown by the solid line in FIG. 5, two or more attenuation poles can be formed and the attenuation band can be widened.

Also, the impedance curve measured with the network analyzer HP8753C 50Ω system.

In FIG. 6, it is shown by a solid line. In the figure, the vertical axis is the reflection coefficient (''), the horizontal axis is the frequency, and one reflection coefficient is expressed by the following formula: r = (Zr - 2o) / (Zr + Zo).
In the above equation, Zo is the characteristic impedance and Zr is the impedance of the element. As is known from FIG. 6, high inductance can be obtained in the high frequency band 5, for example, 100 MH2 or higher. Furthermore, the frequency band in which 5 can be removed can be widened. This characteristic has not been found in conventional LC filters.

Also, the above 1. The second inductor conductor 21.22 and the capacitor conductor 11.12 are dielectric layers.

It is formed by laminating layers with an insulating layer interposed therebetween. Therefore.

By changing the thickness and material of the dielectric layer and the insulating layer, the capacitance can be increased and the capacitance and attenuation characteristics of the entire LC filter can be set arbitrarily.

In the two examples, the dielectric layer is thin.

Since the insulating layer is used and the side conductor is also formed by thin thick film printing, the thickness of the LC filter can be reduced. Therefore, the entire LC filter can be made more compact. Also.

Since the insulator layer uses a material for a low-temperature fired substrate, it can be simultaneously fired (integrated firing) at a relatively low temperature, for example 800°C to 1000°C, and is easy to manufacture.

As described above, according to this example, we have increased the inductance that could not be obtained freely due to the small size, and created a compact LC filter with sharp power cut-off frequency characteristics, large insertion loss, and wide attenuation band. Obtainable.

Second Embodiment As shown in FIGS. 3 and 4, the L'C filter of this embodiment has an inductor conductor on only one side, instead of the LC filter that forms a T-shaped equivalent circuit in the first embodiment. This is an L-shaped equivalent circuit. That is, flat capacitor conductors 11 and 12 are provided on both sides of the dielectric layer 40.
A spiral inductor conductor 27 is placed on the capacitor conductor 11 with an insulating layer 38 interposed therebetween.

Further, - the inductor conductor 27 has a central terminal 212 formed at its center connected in series with the capacitor conductor II via the through hole 28 .

Further, the capacitor conductor 11 connects a signal circuit 42 formed at one end thereof to a conductor circuit 391 on the insulating layer 39 via the signal conductor 29. and.

The capacitor conductor 12 is formed on an insulator layer 39, and a conductor circuit 121 formed at one end thereof is connected to a ground terminal 71.
Connect to.

Moreover, one insulator layer 3 is provided above the inductor conductor 27.
Layer 1. The insulating layer 31 has a signal input terminal 51 and a signal output terminal 61 at both ends thereof. Signal input terminals 51 formed at both ends of the insulator layers 37, 38, 39
and the signal output terminal 61 are connected in series through signal conductors 55 and 65.The other configuration is the same as that of the first embodiment.

The LC filter forms an L-shaped equivalent circuit, as shown in FIG. do.

According to this example, effects similar to those of the first example can be obtained.

[Brief explanation of the drawing]

1 and 2 show the LC filter according to the first embodiment, FIG. 1 is an exploded perspective view thereof, FIG. 2 is an equivalent circuit diagram thereof, and FIGS. 3 and 4 are the LC filter according to the second embodiment. Such an LC filter is shown; FIG. 3 is a developed perspective view thereof, FIG. 4 is an equivalent circuit diagram thereof, FIG. 5 is an insertion loss curve diagram of the LC filter, and FIG.
The figure shows an impedance curve diagram of an LC filter, FIGS. 7 and 8 show conventional examples, FIG. 7 is a front view of a three-terminal type LC filter, and FIG. 8 is an equivalent circuit diagram of the LC filter. 11.12. ,,conductor for capacitors. 2+, , first inductor conductor. 22, second inductor conductor. 27,,inductor conductor. 31-39. ,,insulator layer. 411. dielectric layer. 51, signal input terminal. 61,, signal output terminal. 71, , Ground terminal.

Claims (5)

[Claims] (1) Consists of a flat capacitor conductor placed on both sides of a dielectric layer, and a spiral inductor conductor placed on one or both sides of the capacitor conductor with an insulating layer interposed between the capacitor conductors. An LC filter characterized in that one of the inductor conductors is connected in series with the inductor conductor, signal terminals are connected to both ends thereof, and the other capacitor conductor is connected to a ground terminal. (2) The LC filter according to claim 1, wherein the dielectric layer is a composite ceramic made of borosilicate glass and lead titanate. (3) In the first claim, the dielectric layer has a thickness of 20 to 8
An LC filter characterized in that it is a film formed by screen printing with a thickness of 0 μm. (4) In the first claim, the insulating layer is a low temperature fired material CaO-Al_2O_3-SiO_2-B_2O_
An LC filter characterized by being made of composite ceramics consisting of type 3 glass and alumina. (5) In the first claim, the insulating layer has a thickness of 0.05
An LC filter characterized in that it is constructed using a ceramic green sheet for low-temperature firing substrates of ~0.3 mm.