JP2001267141A - Low-pass filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a low-pass filter to sufficiently exhibit the effect of miniatur ization resulting from the multilayered electrodes, the increased permittivity of a dielectric substrate, and so on, by eliminating the disadvantages of the multilayered electrodes, the increased permittivity of the dielectric substrate, and so on. SOLUTION: The dielectric substrate 12 is constituted by successively laminating a plurality of dielectric layers (first to fourth dielectric layers S1-S4) having low permittivity, for instance, two dielectric layers (fifth and sixth dielectric layers S5 and S6) having high permittivity, and a plurality of dielectric layers (seventh to tenth dielectric layers S7-S10) having low permittivity upon another. An input electrode 20, an output electrode 22, and an electrode 24 constituting an inductance L connected between the electrodes 20 and 22 are integrally formed on one main surface of the sixth dielectric layer S6, and first and third inner-layer earthing electrodes 40 and 44 are formed so as to sandwich the input electrode 20 between the electrodes 40 and 44. In addition, second and fourth inner-layer earthing electrodes 42 and 46 are formed so as to sandwich the output electrode 22 between the electrodes 42 and 46.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-pass filter formed on a dielectric substrate, and more particularly, to a low-pass filter suitable for use as a low-pass filter connected to a transmitting side of a transmitting / receiving apparatus.

[0002]

2. Description of the Related Art In recent mobile communications and portable telephones, transmission and reception are shared by a single antenna.

Specifically, when signals having different frequencies are used for transmission and reception, a duplexer combining a band-pass filter for passing a transmission signal and a band-pass filter for passing a reception signal is connected to an antenna. The antenna is shared.

When the same frequency is used for transmission and reception, antennas are shared by switching between transmission and reception on a time axis using a switch circuit.

In the transmitting / receiving apparatus, a low-pass filter is connected to, for example, a transmission side of a transmission / reception switch in order to improve transmission characteristics.

[0006]

By the way, as a low-pass filter connected to the transmission side of the transmission / reception device, a low-pass filter using a ceramic dielectric substrate which can be downsized is generally adopted.

In order to reduce the size of a low-pass filter using a ceramic dielectric substrate, it is necessary to reduce the size of a capacitance element (electrodes opposed to each other with a dielectric layer interposed therebetween). And a method of increasing the dielectric constant of the ceramic dielectric substrate.

However, when the method of making the dielectric substrate thinner is employed, dielectric breakdown may occur, mechanical strength may be reduced, handling may be difficult in a manufacturing process, and manufacturing costs may increase. .

Further, when the method of forming the electrodes in a multilayer structure is employed, miniaturization in the thickness direction is restricted, and
There arises a problem that a through hole and a side pattern for conducting the multilayer electrode are required, and when the side pattern is provided, there is a concern that the side electrode is likely to be affected by a shield conductor provided outside the low-pass filter.

When the method of increasing the dielectric constant of the ceramic dielectric substrate is adopted, the inductance constituting the low-pass filter is reduced. Therefore, in order to obtain a desired inductance, for example, when the electrode is formed in a coil shape, It is necessary to increase the number of turns of the coil or increase the cross-sectional area of the coil, and these increases must be performed without increasing the coil length as much as possible. Will be caused.

The present invention has been made in view of such problems, and can eliminate disadvantages caused by increasing the number of electrodes and increasing the dielectric constant of a ceramic dielectric substrate. An object of the present invention is to provide a low-pass filter capable of sufficiently exhibiting the effect of miniaturization by increasing the dielectric constant of a ceramic dielectric substrate.

[0012]

A low-pass filter according to the present invention has a dielectric substrate formed by laminating a plurality of dielectric layers having different dielectric constants from each other. Of the dielectric layers, an input electrode, an output electrode, and an electrode forming an inductance connected between these electrodes are formed on a dielectric layer having a high dielectric constant, and a capacitance is formed between the input electrode and ground. A first electrode for
A second capacitor for forming a capacitor between the output electrode and ground;
And an electrode of

As a result, first, capacitance is formed between the input electrode and the first electrode, and between the output electrode and the second electrode. The capacitance is formed between the input electrode and the first electrode, and between the output electrode and the first electrode. Since a dielectric layer having a high dielectric constant exists between the two electrodes, the capacitance can be increased.

On the other hand, the electrodes constituting the inductance are also formed on the dielectric layer having a high dielectric constant. However, due to the presence of the dielectric layer having a low dielectric constant laminated on the dielectric layer having a high dielectric constant, The electric field is concentrated on the dielectric layer having a low dielectric constant, so that a decrease in the characteristic impedance due to the electrodes constituting the inductance is suppressed. That is, the electrodes constituting the inductance are formed on the dielectric layer having a low dielectric constant in a pseudo manner, and the adverse effects caused by using the dielectric layer having a high dielectric constant can be avoided.

As described above, in the present invention, the effect of miniaturizing the low-pass filter by increasing the dielectric constant of the dielectric substrate can be sufficiently exhibited.

Preferably, the dielectric substrate has a structure in which both main surfaces of the dielectric layer having a high dielectric constant are sandwiched by dielectric layers having a low dielectric constant.

Further, the first electrode is connected to two electrode bodies which are respectively stacked on both main surfaces of the input electrode with the dielectric layer having a high dielectric constant interposed therebetween, and these electrode bodies are connected to each other. And the second electrode is constituted by:
Two electrode bodies respectively stacked on both main surfaces of the output electrode with the high dielectric constant dielectric layer interposed therebetween,
It may be constituted by connection electrodes for connecting these electrode bodies. In this case, each connection electrode in the first and second electrodes may be configured with a through hole.

According to these configurations, two electrode bodies are superposed two-dimensionally with the input electrode interposed therebetween, and two electrode main bodies are superposed two-dimensionally with the output electrode interposed therebetween. In addition, since a dielectric layer having a high dielectric constant is interposed between each two electrode bodies, a synergistic effect of increasing the capacitance by increasing the number of electrodes and increasing the capacitance by increasing the dielectric constant is achieved. Obtainable.

Further, the first and second electrodes may be directly connected to a ground electrode formed on the surface of the dielectric substrate via the through hole. in this case,
Since it is not necessary to connect the multilayered electrode to the ground electrode using a wide side pattern, it is less likely to be affected by a shield conductor provided outside the dielectric substrate, and deterioration of characteristics can be prevented.

The electrodes constituting the inductance may have a meandering shape. In this case, the inductance can be efficiently formed on the dielectric layer, and the degree of freedom in design is widened.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a low-pass filter according to the present invention will be described below with reference to FIGS.

The low-pass filter 10 according to the present embodiment
As shown in FIG. 1, has a dielectric substrate 12 formed by laminating a plurality of dielectric layers having different dielectric constants from each other. Specifically, as shown in FIG. 2, the dielectric substrate 12 includes a plurality of dielectric layers (for example, first to fourth dielectric layers S1 to S1) having a low dielectric constant (for example, dielectric constant εr = 7). S
4) and, for example, two dielectric layers (fifth and sixth dielectric layers S5) having a high dielectric constant (for example, dielectric constant εr = 85).
And S6), and a plurality of dielectric layers (for example, seventh to tenth dielectric layers S7 to S10) having a low dielectric constant (for example, dielectric constant εr = 7) are sequentially laminated. Each of the first to tenth dielectric layers S1 to S10 is 1
It is composed of one or more layers.

In the low-pass filter 10 according to this embodiment, the input electrode 20, the output electrode 22, and the electrodes 20 are formed on one main surface of the sixth dielectric layer S6.
And an input terminal 30 (see FIG. 1) formed between the input electrode 20 and one side surface of the dielectric substrate 12. Lead electrode 100 and the output electrode 2
2 and a second lead electrode 102 for electrically connecting the output terminal 32 (see FIG. 1) formed on the other side surface of the dielectric substrate 12 are integrally formed. Inductance L
Is formed in a meandering shape.

On one main surface of the fifth dielectric layer S5, which is located above the sixth dielectric layer S6, the input electrode 20 and the output electrode 22 are provided at positions corresponding to the input electrode 20 and the output electrode 22, respectively. First and second inner-layer ground electrodes 40 and 42 respectively overlapping the output electrode 22 in a plane are formed.

The input electrode 20 and the output electrode 22 are also formed on one main surface of the seventh dielectric layer S7 located below the sixth dielectric layer S6. Third and fourth inner-layer ground electrodes 44 and 46, which respectively overlap the output electrode 22 in a plane, are formed.

Further, on one principal surface of the second dielectric layer S2,
A wide inner earth electrode 104 is formed to include the first and second inner earth electrodes 40 and 42 formed on the fifth dielectric layer S5, and a tenth dielectric layer S1 is formed.
0, a wide inner earth electrode 106 is formed so as to include the third and fourth inner earth electrodes 44 and 46 formed on the seventh dielectric layer S7. As shown in FIG. 1, the ground electrodes 104 and 106 are connected to the side surface (the input terminal 30 and the output terminal 3) of the dielectric substrate 12.
2 is electrically connected to a ground electrode 52 formed on the upper surface and the other side surface.

The above-mentioned first to fourth inner layer earth electrodes 40,
Of the 42, 44, and 46, the first and third inner-layer ground electrodes 40 and 44 on the input electrode 20 side are the first through holes 50 formed in the second to ninth dielectric layers S2 to S9.
And are electrically connected to the wide inner layer earth electrodes 104 and 106.

The first to fourth inner-layer ground electrodes 4
0, 42, 44 and 46, the second on the output electrode 22 side.
And the fourth inner layer ground electrodes 42 and 46
Are electrically connected to each other through the second through holes 54 formed in the dielectric layers S2 to S9, and are also electrically connected to the wide inner-layer ground electrodes 104 and 106.

The low-pass filter 10 according to the present embodiment
Is basically configured as above,
Here, the electrical coupling of each electrode will be described with reference to FIGS.

First, capacitances C1 and C2 are formed between the input electrode 20 electrically connected to the input terminal 30 and the first and third inner-layer ground electrodes 40 and 44, respectively.
The output electrode 22 electrically connected to the output terminal 32 and the second
Further, capacitances C3 and C4 are formed between the fourth inner-layer ground electrodes 42 and 46, respectively.

As a result, as shown in FIG.
0 and the ground, a combined capacitance C10 of the two input-side capacitances C1 and C2 is inserted and connected. Between the output terminal 32 and the ground, the two output-side capacitances C3 and C4 are connected. Is formed by inserting and connecting the combined capacitor C11. Also,
An inductance L is inserted and connected between the input terminal 30 and the output terminal 32 by the meandering electrode 24. That is, one low-pass filter 10 is constituted by the combined capacitors C10 and C11 and the inductance L.

As described above, the low-pass filter 10 according to the present embodiment comprises the input electrode 20 and the first and third inner-layer earth electrodes 40 and 44, and the output electrode 22 and the second and fourth inner-layer earth electrodes. Capacitors C1 and C2 and C3 and C4 are formed between 42 and 46, respectively.
The input electrode 20 and the first and third inner-layer ground electrodes 4
0 and 44, and between the output electrode 22 and the second and fourth inner-layer ground electrodes 42 and 46, the fifth and sixth dielectric layers S5 and S6 having a high dielectric constant exist. C1, C2, C3 and C4 can be increased.

On the other hand, the electrode 2 forming the inductance L
4 is also formed on the dielectric layers S5 and S6 having a high dielectric constant.

Here, assuming that the inductance L is constituted by a strip line, the inductance L becomes (1 / ω) · Z ₀ · sin θ [Henry]. Note that ω is the angular frequency (2πf), θ is the electrical length of the strip line, and Z ₀ is the characteristic impedance. Thus, when the dielectric constant εr increases, the characteristic impedance Z ₀ decreases, and the inductance L decreases.

Therefore, in order to obtain the required inductance L, it is necessary to increase the characteristic impedance Z ₀ , but for that purpose, it is necessary to increase the thickness of the dielectric substrate 12, and furthermore, the increase in the thickness This must be performed without increasing the line length, which makes the design difficult and increases the size of the low-pass filter.

However, the low-pass filter 10 according to the present embodiment has the fifth and sixth dielectric layers S5 having a high dielectric constant.
And the first and second layers having low dielectric constants in the upper layer and the lower layer
The fourth dielectric layers S1 to S4 and the seventh to tenth dielectric layers S7 to S10 are laminated. in this case,
According to Maxwell's equation, when the electric flux density is constant, the electric field is reduced by the dielectric layers S1 to S4 and S7 to
As a result, the inductance L does not decrease. That is, a decrease in the characteristic impedance due to the electrode 24 is suppressed.

That is, in the present embodiment, the electrode 24 constituting the inductance L is formed on the dielectric layer having a pseudo low dielectric constant, and the dielectric layers S5 and S6 having high dielectric constant are used. It is possible to avoid the adverse effects caused by this. Thus, in the present embodiment, the effect of miniaturizing the low-pass filter 10 by increasing the dielectric constant of the dielectric substrate 12 can be sufficiently exhibited.

In particular, in this embodiment, the input electrode 20
Between the first and third inner-layer ground electrodes 40 and 4
4 are superimposed two-dimensionally, and the second and fourth inner-layer earth electrodes 42 and 46 are superimposed two-dimensionally with the output electrode 22 interposed therebetween. Since the fifth and sixth dielectric layers S5 and S6 having a high dielectric constant are interposed between the electrodes 40 and 44 and between the second and fourth inner-layer ground electrodes 42 and 46, the capacitance due to the multilayered electrodes is formed. And the increase in capacitance due to the high dielectric constant can have a synergistic effect.

Further, in this embodiment, the first and third inner-layer ground electrodes 40 and 44 are connected to the first through-hole 50.
Is directly connected to the ground electrode 52 formed on the lower surface of the dielectric substrate 12 through the second and fourth inner-layer ground electrodes 42.
And 46 are directly connected to a ground electrode 52 formed on the lower surface of the dielectric substrate 12 via a second through hole 54.

In this case, the multilayered inner earth electrode 4
Since it is not necessary to connect 0, 42, 44 and 46 to the ground electrode 52 using a wide side pattern, the influence of a shield conductor provided outside the dielectric substrate 12 is reduced, and deterioration of characteristics is prevented. Can be.

In the present embodiment, since the electrodes 24 forming the inductance L have a meandering shape, the inductance L can be efficiently formed on the dielectric layer S6, and the degree of freedom in design can be increased. Can be.

The low-pass filter according to the present invention is not limited to the above-described embodiment, but can adopt various configurations without departing from the gist of the present invention.

[0043]

As described above, according to the low-pass filter according to the present invention, it is possible to eliminate the drawbacks caused by increasing the number of electrodes and increasing the dielectric constant of the dielectric substrate. The effect of miniaturization by increasing the dielectric constant of the dielectric substrate can be sufficiently exerted.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a low-pass filter according to an embodiment.

FIG. 2 is an exploded perspective view illustrating a configuration of a low-pass filter according to the present embodiment.

FIG. 3 is a longitudinal sectional view illustrating a configuration of a low-pass filter according to the present embodiment.

FIG. 4 is an equivalent circuit diagram of the low-pass filter according to the present embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Low-pass filter 12 ... Dielectric substrate 20 ... Input electrode 22 ... Output electrode 24 ... Electrode which comprises inductance 30 ... Input terminal 32 ... Output terminal 40 ... 1st inner-layer earth electrode 42 ... 2nd inner-layer earth electrode 44 ... Third inner-layer ground electrode 46 Fourth inner-layer ground electrode 50 First through-hole 52 Ground electrode 54 Second through-hole S1 to S4, S7 to S10 Dielectric layers S5 and S6 having a low dielectric constant ... Dielectric layer with high dielectric constant

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kazuyuki Mizuno 2-56, Suda-cho, Mizuho-ku, Nagoya-shi, Aichi Japan F Co., Ltd. F-term (reference) 5E070 AA05 AB01 CB03 CB12 CB17 CB18 EA01 5E082 AA01 AB03 BB02 BC39 DD08 EE04 EE17 FF05 FG06 FG26 GG10 GG28 JJ02 KK08 LL15 5J024 AA01 BA02 DA00 DA04 DA29 DA35 EA01 FA03

Claims (6)

[Claims] 1. A dielectric substrate comprising a plurality of dielectric layers having different dielectric constants stacked on each other, wherein the plurality of dielectric layers constituting the dielectric substrate include:
An input electrode, an output electrode, and an electrode forming an inductance connected between these electrodes are formed on a dielectric layer having a high dielectric constant, and a first electrode for forming a capacitance between the input electrode and ground is formed.
And a second electrode for forming a capacitor between the output electrode and the ground. 2. The low-pass filter according to claim 1, wherein said dielectric substrate has a structure in which both main surfaces of said dielectric layer having a high dielectric constant are sandwiched by dielectric layers each having a low dielectric constant. Characteristic low-pass filter. 3. The low-pass filter according to claim 1, wherein the first electrode is overlapped on both main surfaces of the input electrode with the dielectric layer having a high dielectric constant interposed therebetween. It is composed of two electrode bodies and connection electrodes for connecting these electrode bodies, and the second electrode has the dielectric layer having a high dielectric constant interposed between both main surfaces of the output electrode. A low-pass filter comprising two electrode bodies superposed on each other and a connection electrode for connecting these electrode bodies. 4. The low-pass filter according to claim 3, wherein each of the connection electrodes in the first and second electrodes is constituted by a through hole. 5. The low-pass filter according to claim 4, wherein said first and second electrodes are directly connected to a ground electrode formed on a surface of said dielectric substrate via said through hole. And a low pass filter. 6. The low-pass filter according to claim 1, wherein an electrode forming the inductance has a meandering shape.