JP3522098B2 - Multilayer dielectric filter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated dielectric filter which can be built in a circuit board for an RF module or the like and is used in a filter or a duplexer incorporated in a radio frequency radio unit of a mobile communication telephone or the like.

[0002]

2. Description of the Related Art Conventionally, a SAW filter has been used as a reception RF filter of a mobile phone which requires attenuation in the vicinity of tens of MHz of a reception pass band, because of its steep attenuation characteristic, a SAW filter is exclusively used. Is rarely used (except for cordless phones that do not require abrupt attenuation characteristics). Further, since the coaxial type dielectric filter is large in size, it is less frequently used.

By the way, with the miniaturization of mobile phones, there is a strong demand for miniaturization of electronic components, and the modularization of electronic components is progressing.
BPF, low pass filter
And a passive circuit such as a matching circuit for impedance matching,
It is required to be built in the circuit board.

In addition, dual mobile phones (for example,
Since both 900MHz band and 1800MHz band can be transmitted / received), simply two RF filters for reception and two LPFs for transmission are required. In the future, as the number of filters increases to triple and multi-system, the number of filters will increase. Is increasing. However, it is not allowed to increase the size of the mobile phone, and further downsizing is required.

Therefore, it has a steep characteristic and further
Up to 2 so that it can be built in together with F and matching circuits
A filter that can be built into a circuit board having a relative dielectric constant up to about 0 is required. Furthermore, the thickness of the filter is limited to a maximum of 1.2 mm (assuming that the mounted chip product is a maximum of 0.7 mm) so that it can be built into a circuit board used in electronic components that require a height of 2 mm or less. .

Conventionally, a coaxial dielectric filter having a steep attenuation characteristic has been realized by using the circuit diagram of FIG. 8 (OK
I Technical Review 150 Vol.60 P45 ~ P52).

[0007]

However, the size of this coaxial type dielectric filter is large, and there is a problem that it is not possible to cope with the recent downsizing and height reduction. Further, according to this circuit diagram, a large inductance L which is difficult to realize with the laminated dielectric filter is required.

It is an object of the present invention to provide a laminated dielectric filter which can be made smaller and thinner, can be integrally built in a circuit board containing a matching circuit and the like, and has a steep attenuation characteristic.

[0009]

Laminated dielectric filter of the present invention In order to achieve the above object, according to the laminate comprising a dielectric layer laminating a plurality 4
A laminated dielectric filter having a quarter-wavelength stripline resonator stages, the quarter-wavelength stripline resonator of the four-stage, four resonant electrodes formed on the same plane, Formed above the resonance electrodes on both sides,
Formation of the capacitor connected by the resonance electrode of the
Is formed below the intermediate electrode and the intermediate electrode.
For forming capacitance connected by resonance electrode and via-hole conductor
An electrode and an input / output electrode formed between the resonance electrode connected by the via-hole conductor and the capacitance forming electrode, and the resonance electrode on both sides and the intermediate resonance electrode. And are close to each other and are electromagnetically coupled. Here, the distance between the resonance electrodes on both sides and the middle resonance electrode is preferably 0.1 to 0.3 mm.

[0010]

In the laminated dielectric filter of the present invention, since the resonance electrodes on both sides and the resonance electrodes adjacent to these resonance electrodes are close to each other and are electromagnetically coupled to each other, mutual inductance is generated. A pole is formed near the high frequency side of the pass band by the inductance, a plurality of input / output capacitances generated between the input / output electrodes and the resonance electrode, and a resonance circuit including a resonator, and a steep attenuation characteristic is realized.

Further, the length of the resonance electrode can be shortened by the capacitance generated between the capacitance forming electrode connected to the resonance electrode and the ground electrode, and the filter can be miniaturized.

That is, the present invention uses the mutual inductance between the resonance electrodes as in the circuit shown in FIG. 7, instead of the inductance L of the conventional circuit shown in FIG. As a result, a steep attenuation characteristic can be realized in the laminated dielectric filter.

Further, the interval between the resonance electrodes on both sides and the intermediate resonance electrodes adjacent to these resonance electrodes is 0.1.
By setting the thickness to 0.3 mm, the porcelain coupling between these resonance electrodes becomes strong, the mutual inductance increases, a pole can be reliably formed near the high frequency side of the pass band, and a steeper attenuation characteristic can be realized.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic development view of a laminated dielectric filter (hereinafter referred to as a filter) of the present invention, FIG. 2 is an external view of the filter and a perspective view in which the internal structure is omitted, and FIG. [Fig. 3] is a cross-sectional view of a filter.

In FIG. 1, reference numerals 1 to 9 are dielectric layers. Reference numerals 13A to 13D are resonance electrodes formed on one main surface of the dielectric layer 5, and reference numerals 11 and 12 are ground electrodes.
Reference numerals 14A and 14D denote capacitance forming electrodes formed on one main surface of the dielectric layer 7, which are formed above the resonance electrodes 13A and 13D, respectively, and are connected to the resonance electrodes 13A and 13D by the via hole conductors 31 and 34. There is. Similarly, reference numerals 14B and 14C are capacitance-forming electrodes formed on one main surface of the dielectric layer 2, which are formed below the resonance electrodes 13B and 13C, respectively, and are formed by the resonance electrodes 13B and 13C and the via-hole conductors 32 and 33. It is connected.

These resonance electrodes 13A to 13D, the ground electrodes 11 and 12, and the capacitance forming electrodes 14A, 14B and 14
C, 14D, via-hole conductors 31, 32, 33, 34
Thus, a four-stage quarter-wave stripline resonator is formed.

The resonance electrode 13A of the first-stage resonator and the resonance electrode 13B adjacent to the resonance electrode 13B are arranged close to each other.
Mutual inductance is formed between A and 13B.
Similarly, the resonance electrode 13C of the final stage resonator and the resonance electrode 13C adjacent to the resonance electrode 13D are also arranged close to each other.
Mutual inductance is formed between 3D. That is, the resonance electrodes 13A and 13D on both sides and the resonance electrodes 13B and 13C adjacent to the resonance electrodes 13A and 13D are arranged close to each other.

The resonance electrodes 13A and 13B and the resonance electrode 13
If the mutual inductance of C and 13D is too small, it becomes difficult to generate a pole on the high frequency side near the pass band. Therefore, the resonance electrodes 13A and 13B, and the resonance electrodes 13C and 13D.
The distance is 0.3 mm or less, and 0.15 mm or less is desirable in consideration of adjusting the characteristics of the filter.

Further, between the capacitance forming electrode 14A and the resonance electrode 13A connected by the via hole conductor 31,
The first input / output electrode 15A is formed, and the via-hole conductor 32 is formed.
Capacitance forming electrode 14B and resonance electrode 13 connected by
A second input / output electrode 16A is formed between B and B, and the capacitance forming electrode 14C is connected by a via-hole conductor 33.
A second input / output electrode 16B is formed between the resonance electrode 13C and the resonance electrode 13C, and a first input / output electrode 15B is formed between the resonance electrode 13D and the capacitance forming electrode 14D connected by the via-hole conductor 34. Has been done.

Thus, the first input / output electrodes 15A, 15
B faces the capacitance forming electrodes 14A and 14D to form a first input / output capacitance. The second input / output electrodes 16A and 16B face the capacitance forming electrodes 14B and 14C to form second input / output capacitances. The mutual inductance, the first input / output capacitance, the second input / output capacitance and the resonator constitute a resonance circuit for generating an attenuation pole.

The stray capacitance electrode 17 formed on one main surface of the dielectric layer 3 faces the resonance electrodes 13B and 13C and forms an interstage capacitance between those electrodes.

In this filter, as shown in FIG. 1, electrodes made of a conductive material are formed on one surface of a plurality of dielectric layers made of unsintered green sheets by a printing method or the like. Is produced by laminating these dielectric layers so as not to cause a contact short circuit between the dielectric layers 1 to 9 and sintering and integrating them.

The dielectric material constituting the dielectric layers 1 to 9 has a relative dielectric constant of about 20 at maximum, and is aMgO.b.
CaO · cTiO ₂ (25 ≦ a ≦ 35, 0.3 ≦ b ≦
7,60 ≦ c ≦ 70, a + b + c = 100 weight ratio),
It is preferable that the boron-containing compound is added in an amount of 3 to 20 parts by weight in terms of B ₂ O ₃ , and the lithium-containing compound is added in an amount of 1 to 10 parts by weight in terms of Li ₂ O _3. It becomes possible to integrally incorporate the LPF and the matching circuit.

Further, the resonance electrodes 13A to 13D, the capacitance forming electrodes 14A to 14D, the input / output electrodes 15A, 15B, 1
It is desirable that 6A, 16B, etc. be formed using a low-resistance conductor such as copper, silver, or gold. Then, each of the dielectric layers 1 to
9 is preferably co-fired with the circuit board using a low temperature firing material of about 900 to 1000 ° C., and can be efficiently manufactured by co-firing at low temperature.

The filter of the present invention alone has an external shape as shown in FIG. Input / output electrodes 15A and 16A,
External input / output electrodes 2 are provided at positions corresponding to 15B and 16B.
1, 22 are formed, and the external ground electrode 2 is formed on the remaining two side surfaces.
3, 24 are formed. Although the ground electrodes 11 and 12 are connected to the external ground electrode 23, the external ground electrode 2
Further, one end of the resonance electrodes 13A to 13D is connected to 4.

When the filter of the present invention is built in a circuit board, the structure shown in FIG. 4 is obtained. FIG. 4 is a sectional view of a circuit board having a filter built therein. In this case, vias, vertical electrodes, or the like may be used instead of the external ground electrodes 23, 24 and the external input / output electrodes 21, 22, and the filter can be installed at any location on the circuit board. Further, as shown in FIG. 4, the earth electrodes 11 and 12 may be replaced with the earth electrodes of the circuit board.

An equivalent circuit of the filter of the present invention is shown in FIG. 5, which will be described below. Resonance electrodes 13A-1
Resonant inductors 41 to 44 are configured by the 3D and via hole conductors 31 to 34, and the capacitance forming electrodes 14A to 14 are formed.
Between the D and the ground electrodes 11 and 12, a resonance capacitor 45
~ 48 are configured. Between the first input / output electrode 15A and the capacitance forming electrode 14A, the first input / output capacitor 51, the second
The second portion is provided between the input / output electrode 16A and the capacitance forming electrode 14B.
The input / output capacitor 53 is configured. Similarly, a first input / output capacitor 52 is formed between the first input / output electrode 15B and the capacitance forming electrode 14D, and a second input / output capacitor 54 is formed between the second input / output electrode 16B and the capacitance forming electrode 14C. To be done. The floating capacitance electrode 17 constitutes an interstage capacitor 55.

The resonance electrodes 13A to 13D are magnetically coupled between adjacent lines, which is represented by a mutual inductance M in an equivalent circuit. Particularly, in the filter of the present invention, the mutual inductance M ₁ between the first-stage resonance electrode 13A and the adjacent resonance electrode 13B and the last-stage resonance electrode 1
Mutual inductance M ₃ between 3D and the adjacent resonance electrode 13C is indispensable for obtaining steep attenuation characteristics.

In this equivalent circuit, matching in the pass frequency and pass band is mainly made by the resonance inductors 41 to 44.
And the resonance capacitors 45 to 48, and the ratio of the mutual inductance M ₁ to the first input / output capacitance 51 and the second input / output capacitance 53, and the mutual inductance M ₃ to the first input / output capacitance 52 and the second input / output capacitance 54. The position of the attenuation pole near the pass band is adjusted by.

The characteristics other than those in the vicinity of the pass band are adjusted by using input / output capacitors, interstage capacitors, and the like. For example, on the high frequency side of the pass band, the second input / output capacitors 53 and 54 and the resonance electrodes 13A to 13D form a 1/2 wavelength type resonance circuit, and an attenuation pole can be formed.

[0031]

EXAMPLE The attenuation amount and the generation of poles were determined by simulation for the laminated dielectric filter shown in FIG.
The size of the filter is 3.5 x 3.5 x 1.2 mm,
The size of the resonance electrodes 13A to 13D is 0.5 mm × 3 mm
And the distance d between the resonance electrode 13A and the resonance electrode 13B and the distance d between the resonance electrode 13C and the resonance electrode 13D are changed as shown in Table 1 to find the attenuation amount and the generation of the pole at +40 MHz. It was

For the attenuation amount at +40 MHz, when matching is performed in the pass band, the pole position is adjusted by the input / output capacitance, and the frequency on the high frequency side when the insertion loss is 3 dB is deviated by +40 MHz on the high frequency side. Find the attenuation of
The steepness of the damping characteristics was evaluated. The larger the attenuation amount, the steeper the attenuation characteristic.

[0033]

[Table 1]

From this table, when the distance d is 0.3 mm or less, particularly 0.15 mm or less, the mutual inductance generated between the resonance electrodes is large, a pole is generated, and a steep attenuation is generated. It can be seen that it has characteristics.

FIG. 6 shows the transmission characteristics by the electromagnetic field simulation when the distance d is 0.1 mm. From FIG. 6, in the pass frequency bands 1805 to 1880 MHz, the insertion loss was 3 dB or less, the attenuation amount was 9 dB at -40 MHz, and the attenuation amount was 14 dB at +40 MHz.

[0036]

In the laminated dielectric filter of the present invention, the resonance electrode length can be shortened and the miniaturization can be achieved by the capacitance between the capacitance forming electrode connected to the resonance electrode and the ground electrode. Further, a resonance circuit is configured by the mutual inductance, the input / output capacitance, and the resonator that are generated when the resonance electrodes are close to each other, and a pole is generated on the high frequency side near the pass band. As a result, a steep attenuation characteristic of the filter is realized. Further, the filter of the present invention has a radius of 1.2 mm or less and R
It can be manufactured integrally with the circuit board for the F module.

[Brief description of drawings]

FIG. 1 is a schematic exploded perspective view of a laminated dielectric filter of the present invention.

FIG. 2 is a perspective view showing an appearance of a laminated dielectric filter of the present invention.

FIG. 3 is a cross-sectional view of a laminated dielectric filter of the present invention.

FIG. 4 is a cross-sectional view of the case where the laminated dielectric filter of the present invention is built in a circuit board.

FIG. 5 is an equivalent circuit diagram of the laminated dielectric filter of the present invention.

FIG. 6 is a transmission characteristic diagram of an electromagnetic field simulation of the laminated dielectric filter of the present invention.

FIG. 7 is a resonance circuit diagram of the present invention.

FIG. 8 is a circuit diagram of a conventional coaxial dielectric filter.

[Explanation of symbols]

1-9 ... Dielectric layer 11, 12 ... Earth electrode 13A to 13D ... Resonant electrodes 14A to 14D ... Capacitance forming electrodes 15A, 15B ... First input / output electrode 16A, 16B ... second input / output electrodes 17 ... Floating capacitance electrode 21, 22 ... External input / output electrodes 23, 24 ... External earth electrode 31-34 ... Via-hole conductor 41-44 ... Resonant inductor 45-48 ... Resonant capacitor 51, 52 ... First input / output capacitor 53, 54 ... Second input / output capacitor 55 ... Inter-stage capacitor

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Claims (2)

(57) [Claims] 1. A laminated body formed by laminating a plurality of dielectric layers,
A laminated dielectric filter having a quarter wavelength stripline resonators 4 stages, a quarter wavelength stripline resonator of the four stages, four are formed on the same plane <br/> Is formed above the resonance electrodes and the resonance electrodes on both sides.
Capacitive type connected by the side resonance electrode and via-hole conductor
Formed between the production electrode and the intermediate resonance electrode, and the intermediate electrode
Formation of the capacitor connected by the resonance electrode of the
And a resonance electrode on both sides of the resonance electrode and the intermediate resonance electrode, and an input / output electrode is formed between the resonance electrode connected by the via-hole conductor and the capacitance forming electrode. A laminated dielectric filter characterized in that the electrodes are close to each other and electromagnetically coupled. 2. The laminated dielectric filter according to claim 1, wherein the distance between the resonance electrodes on both sides and the middle resonance electrode is 0.1 to 0.3 mm.