JPH09307389A - Laminated type lc filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated LC filter of a small type which easily makes a wide range and is provided with excellent characteristic in a frequency band higher than a center frequency. SOLUTION: A band pass filter 1 is constituted by laminating a dielectric sheet 2d providing strip lines 4 and 6 on its surface, a dielectric sheet 2f providing a strip lines 5 on its surface, and a dielectric sheet providing a capacitor electrode on its surface, etc. The strip lines 4 to 6 respectively function as inductors and respectively constitute LC resonators with capacitors constituted by capacitor electrodes. At these three LC resonators, electromagnetic coupling is generated between the strip lines 4 and 5, and between the strip lines 5 and 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated LC filter, and more particularly to a laminated LC filter containing at least three LC resonators.

[0002]

2. Description of the Related Art As a conventional laminated LC filter, for example, a laminated LC filter 51 shown in FIG. 8 has been proposed. This LC filter 51 includes ground electrodes 53 and 5
A dielectric sheet 52b provided with 4, 55 and a dielectric sheet 52c provided with parallel capacitor electrodes 56, 57, 58.
A dielectric sheet 52d having input / output capacitor electrodes 59 and 60, a dielectric sheet 52f having strip lines 61, 62 and 63, a dielectric sheet 52h having a shield electrode 64, and a dummy dielectric. Seat 52e,
52g and the protective layer dielectric sheets 52a, 52i and the like.

The strip lines 61, 62 and 63 each function as an inductor, the strip lines 61 and 62 are electromagnetically coupled, and the strip lines 62 and 63 are electromagnetically coupled. The strip line 61 connects the capacitor composed of the ground electrode 53 and the capacitor electrode 56 to the LC.
It is electrically connected by an external electrode (not shown) provided on the side surface of the filter 51 to form an LC resonator. Similarly, the strip line 62 constitutes an LC resonator together with the capacitor composed of the ground electrode 54 and the capacitor electrode 57, and the strip line 63 constitutes an LC resonator together with the capacitor composed of the ground electrode 55 and the capacitor electrode 58.

[0004]

However, in the conventional laminated LC filter 51, since the three strip lines 61 to 63 are provided on the same dielectric sheet 52f, the strip is required to obtain a large inductance. When the line lengths of the lines 61 to 63 are increased, the area occupied by the strip lines 61 to 63 increases. For this reason,
The size of the dielectric sheet 52f must be increased, resulting in an increase in size of the LC filter 51.

Further, if the size increase of the LC filter 51 is suppressed, the line lengths of the strip lines 61 to 63 are restricted, so that it is difficult to widen the band of the filter and the degree of freedom in design is low. Further, since the distance between the adjacent strip lines is small, electromagnetic interference between the strip lines is likely to occur, and there is a problem that excellent attenuation characteristics cannot be obtained in a frequency range higher than the center frequency.

Therefore, an object of the present invention is to provide a small-sized laminated LC filter which can be easily widened in band and has excellent attenuation characteristics in a frequency range higher than the center frequency.

[0007]

In order to achieve the above object, in the laminated LC filter according to the present invention, at least one of the three LC resonators has a stripline disposition position. , With respect to the stacking direction of the dielectric layers,
It is characterized in that it is different from the arrangement position of the strip lines of the remaining LC resonators.

Specifically, for example, a first dielectric layer having a strip line of the first LC resonator and a strip line of the third LC resonator provided on the surface, and a strip of the second LC resonator. A second dielectric layer having a line on the surface thereof, the strip line of the first LC resonator and the strip line of the second LC resonator are electromagnetically coupled,
For example, the strip line of the second LC resonator and the strip line of the third LC resonator are electromagnetically coupled.

[0009]

With the above construction, since the strip line of at least one LC resonator is provided on the surface of the dielectric layer different from the surface of the dielectric layer on which the strip lines of the remaining LC resonators are provided, the dielectric Even if the size of the body layer is not increased, the allowable layout area of each strip line on the surface of the dielectric layer is increased. Further, the interval between the adjacent strip lines becomes large, and electromagnetic interference between the strip lines is suppressed.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a laminated LC filter according to the present invention will be described below with reference to the accompanying drawings. In the present embodiment, a band pass filter including three LC resonators will be described as an example of the laminated LC filter. As shown in FIGS. 1 and 2, a bandpass filter 1 includes a dielectric sheet 2 having a shield electrode 3 on its surface.
b, a dielectric sheet 2d having strip lines 4 and 6 on its surface, a dielectric sheet 2f having strip line 5 on its surface, and a dielectric sheet 2h having input / output capacitor electrodes 7 and 14 on its surface. , Parallel capacitor electrode 8,
Dielectric sheet 2i having 9 and 10 provided on the surface and dielectric sheet 2j having ground electrodes 11, 12 and 13 provided on the surface
And dummy dielectric sheets 2c, 2e and 2g, and protective layer dielectric sheets 2a and 2k.

The materials for the dielectric sheets 2a-2k are:
A resin such as epoxy or a ceramic dielectric is used. In the present embodiment, as the material of the dielectric sheets 2a to 2k, a sheet-shaped material obtained by kneading the dielectric ceramic powder with a binder or the like is used. Shield electrode 3
Is provided in a wide area in the central portion of the sheet 2b and has two drawer portions 3a and 3b. The drawer portion 3a is exposed at a position on the right side of the front side of the sheet 2b, and the drawer portion 3b is exposed.
Is exposed at a position on the left side of the back side of the sheet 2b.
The shield electrode 3 is for preventing electromagnetic waves from radiating to the outside of the filter 1 and preventing unwanted waves from entering the filter 1.

The strip line 4 has a linear shape, and one end 4a is exposed on the left side of the front side of the sheet 2d, and the other end 4b is exposed on the left side of the back side. There is. The strip line 6 has a linear shape, and one end 6a is exposed on the right side of the front side of the sheet 2d, and the other end 6b is exposed on the right side of the back side. The strip line 5 has a substantially linear shape with a bent portion,
One end 5a is exposed at a position closer to the center right of the front side of the sheet 2f, and the other end 5b is exposed at a position closer left of the center of the back side of the sheet 2f. These strip lines 4 to 6 respectively function as inductors, and the strip lines 4 and 5 and the strip lines 5 and 6 are electromagnetically coupled with the sheets 2d and 2e sandwiched therebetween.

The input / output capacitor electrodes 7 and 14 are provided on the left side and right side of the seat 2h, respectively, and the lead-out portions 7a and 14a are exposed on the left and right sides of the seat 2h, respectively. The parallel capacitor electrode 8 is provided on the left side portion of the sheet 2i, and the lead-out portion 8a is exposed on the left side of the back side of the sheet 2i. The parallel capacitor electrode 9 is provided in the center of the sheet 2i, and the lead-out portion 9a is exposed to the right of the center of the front side of the sheet 2i. The parallel capacitor electrode 10 is provided on the right side of the sheet 2i, and the lead-out portion 10a is exposed on the right side of the front side of the sheet 2i.

The ground electrode 11 is provided on the left side of the sheet 2j, and its lead-out portion 11a is exposed on the left side of the front side of the sheet 2j. The ground electrode 12 is the sheet 2
It is provided in the central part of j and the drawer part 12a is the sheet 2
It is exposed to the left of the center of the back side of j. The ground electrode 13 is provided on the right side of the sheet 2j, and its lead-out portion 13a is exposed on the right side of the back side of the sheet 2j.

The parallel capacitor electrodes 8, 9 and 10 are respectively connected to the ground electrodes 11, 12 and 13 with the sheet 2i interposed therebetween.
Are formed so as to face each other, one capacitor is formed by the parallel capacitor electrode 8 and the ground electrode 11, and one capacitor is formed by the parallel capacitor electrode 9 and the ground electrode 12.
The individual capacitors are formed, and the parallel capacitor electrode 10 and the ground electrode 13 form one capacitor.

The dummy dielectric sheet 2g is for ensuring a sufficient distance between the capacitor electrodes 7 to 10 and 14 and the strip lines 4 to 6, whereby the inductivity of the desired strip lines 4 to 6 is achieved. The impedance can be reliably obtained. Also, the dummy dielectric sheet 2e
Is for controlling the pass band width by adjusting the distance between the strip lines 4 and 6 and the strip line 5.

Shield electrode 3, strip line 4 to
6, capacitor electrodes 7 to 10, 14 and ground electrode 1
1 to 13 are made of a material such as Ag-Pd, Ag, Pd, and Cu, and are formed by a method such as a sputtering method, a vacuum vapor deposition method, a printing method or the like. The sheets 2a to 2k are stacked and integrally sintered to form a laminated body as shown in FIGS. 3 and 4. Input / output external electrodes 21, 22 are formed on the left and right side surfaces of the laminated body, and a ground external electrode 23, a dummy external electrode 24, and relay external electrodes 25, 26 are formed on the front side surface, and a back side surface. The relay external electrodes 27, 28, the dummy external electrode 29, and the ground external electrode 30 are formed on the. The external electrodes 21 to 30 are formed by a method such as a sputtering method, a vacuum vapor deposition method, or a printing method, and are made of a material such as Ag-Pd, Ag, Pd, Cu.

The input / output external electrode 21 is electrically connected to the lead portion 7a of the input / output capacitor electrode 7, and the input / output external electrode 22 is the lead portion 14a of the input / output capacitor electrode 14.
, The ground external electrode 23 is electrically connected to the end 4a of the strip line 4 and the lead-out portion 11a of the ground electrode 11, and the relay external electrode 25 is electrically connected to the end 5a of the strip line 5. The relay external electrode 26 is electrically connected to the end 6a of the strip line 6, the lead-out portion 3a of the shield electrode 3, and the lead-out portion 10a of the parallel capacitor electrode 10.

Further, the relay external electrode 27 is electrically connected to the lead-out portion 3b of the shield electrode 3, the end portion 4b of the strip line 4 and the lead-out portion 8a of the parallel capacitor 8,
The relay external electrode 28 is electrically connected to the end portion 5b of the strip line 5 and the lead portion 12a of the ground electrode 12, and the ground external electrode 30 is electrically connected to the end portion 6b of the strip line 6 and the lead portion 13a of the ground electrode 13. It is connected to the.

As shown in FIG. 5, the strip line 4
Is electrically connected in parallel to the capacitor composed of the parallel capacitor electrode 8 and the ground electrode 11 by the ground external electrode 23 and the relay external electrode 27 to form the first-stage LC resonator R1. The strip line 5 is electrically connected in parallel to the capacitor composed of the parallel capacitor electrode 9 and the ground electrode 12 by the relay external electrodes 25 and 28 to form the second-stage LC resonator R2. The strip line 6 is electrically connected in parallel to the capacitor composed of the parallel capacitor electrode 10 and the ground electrode 13 by the relay external electrode 26 and the ground external electrode 30 to form a third-stage LC resonator R3. further,
The input / output capacitor electrode 7 and the parallel capacitor electrode 8 are capacitively coupled, and the input / output capacitor electrode 14 and the parallel capacitor electrode 10 are capacitively coupled.

Bandpass filter 1 having the above configuration
As shown in FIG. 4, when mounted on the printed wiring board 32 or the like, the mounting is performed with the side on which the ground electrodes 11 to 13 are provided being the mounting surface side. In the filter 1, the arrangement position of the strip lines 5 is different from the arrangement positions of the other strip lines 4 and 6 in the stacking direction of the dielectric sheets 2a to 2k. That is, the strip lines 4 and 6 of the first-stage and third-stage LC resonators R1 and R3 are provided on the same dielectric sheet 2d, and the second-stage LC resonator R2.
Since the strip line 5 is provided on another dielectric sheet 2f, it is possible to widen the disposition allowable area of each strip line 4 to 6 on the dielectric sheet without increasing the size of the dielectric sheet. it can.

As a result, the line length of the strip lines 4 to 6 can be increased to obtain a large inductance without increasing the size of the filter 1, and the band of the filter 1 can be widened. FIG. 6 shows the attenuation characteristic of the filter 1 (see the solid line 35) and the reflection loss characteristic (the solid line 3).
6) is shown. FIG. 6 shows the attenuation characteristics of the conventional filter 51 shown in FIG. 8 for comparison (see the dotted line 37).
In addition, the reflection loss characteristic (see the dotted line 38) is also displayed. In FIG. 6, the pass band width of the filter 1 is
It can be seen that it is wider than conventional filters.

Further, since the strip lines 4 and 6 are provided on the same dielectric sheet 2d, the pole P is formed at a position higher than the center frequency by adjusting the distance between the strip lines 4 and 6. It is possible to improve the spurious on the high frequency side. Also,
The distance between the adjacent strip lines 4 and 5 or 5 and 6 is increased, and electromagnetic interference between the strip lines can be suppressed.

Further, since the filter 1 has the input / output capacitor electrodes 7 and 14, the parallel capacitor electrodes 8 to 10 and the ground electrodes 11 to 13 arranged on the mounting surface side of the filter 1, the parasitic inductance is not generated. It can be suppressed, and the spurious characteristics in the high frequency range can be improved. FIG. 7 shows the attenuation characteristics of the filter 1 in the high frequency range (solid line 41
Reference) and reflection loss characteristics (solid line 42). For comparison, FIG. 7 also shows the attenuation characteristic (see dotted line 43) and the reflection loss characteristic (see dotted line 44) of the conventional filter 51 shown in FIG. 8 together.

Further, by changing the thickness of the dielectric sheet 2e,
The gap d between the strip lines 4, 6 and the strip line 5 (see FIG. 4) can be changed to adjust the electromagnetic coupling between the strip lines 4 and 5 or the strip line 5 and 6. it can. By adjusting the electromagnetic coupling between the strip lines, the pass band width of the filter 1 can be easily controlled,
The degree of freedom in design can be increased. Table 1 shows the results of measuring the 3 dB bandwidths of filters 1 having different gaps d.

[0026]

[Table 1]

[Other Embodiments] The laminated LC filter according to the present invention is not limited to the above-mentioned embodiment, but can be variously modified within the scope of the invention.
The laminated LC filter has a first dielectric layer provided with a strip line of a first resonator on its surface, a second dielectric layer provided with a strip line of a second resonator on its surface, and a third dielectric layer.
And a third dielectric layer having a strip line of the resonator provided on its surface, the strip line of the first resonator and the strip line of the second resonator are electromagnetically coupled to each other, and the second resonance The strip line of the resonator and the strip line of the third resonator may be electromagnetically coupled.

The shape of the strip line is arbitrary, and besides the straight line shape, it may be a meandering shape or a spiral shape, and it is necessary that all the strip lines have the same line width. Absent. Further, although the above embodiment has been described by taking the case of an individual product as an example, in the case of mass production, the product may be manufactured by using a mother substrate having a plurality of LC filters and cut into a desired size. it can.

Further, in the above embodiment, the sheets are stacked and then integrally sintered, but the present invention is not limited thereto. The sheet may be a sheet sintered in advance. Alternatively, an LC filter having a laminated structure may be obtained by sequentially applying a paste-like dielectric material or a conductive material by a method such as printing, drying, and recoating.

[0030]

As is apparent from the above description, according to the present invention, the arrangement position of the strip line of at least one LC resonator is set so that the remaining LC resonances with respect to the stacking direction of the dielectric layers. Since the position is different from the position where the strip line of the container is arranged, the allowable area for disposing individual strip lines on the surface of the dielectric layer is increased without increasing the size of the dielectric layer, and the line length of the strip line is increased. Can be long. Therefore, a large inductance can be obtained,
The band of the filter can be widened. Further, the interval between the adjacent strip lines becomes large, and electromagnetic interference between the strip lines can be suppressed. Also, the electromagnetic coupling between the strip lines can be adjusted by changing the thickness of the dielectric, and the pass band width of the filter can be easily controlled.

Further, the first dielectric layer having the strip line of the first LC resonator and the strip line of the third LC resonator provided on the surface, and the strip line of the second LC resonator provided on the surface. A second dielectric layer, and a stripline of the first LC resonator and the second LC resonator.
By electromagnetically coupling the stripline of the resonator and electromagnetically coupling the stripline of the second LC resonator and the stripline of the third LC resonator,
By adjusting the distance between the strip line of the LC resonator and the strip line of the third LC resonator, a pole can be formed at a position on the high frequency side of the center frequency, and spurious on the high frequency side can be improved.

[Brief description of drawings]

FIG. 1 is a partially exploded perspective view showing an embodiment of a laminated LC filter according to the present invention.

FIG. 2 is a partially exploded perspective view of the remaining part of the laminated LC filter shown in FIG.

FIG. 3 is a perspective view showing the appearance of the laminated LC filter shown in FIGS. 1 and 2.

4 is a sectional view taken along line IV-IV in FIG.

5 is an electrical equivalent circuit diagram of the laminated LC filter shown in FIG.

6 is a graph showing attenuation characteristics and reflection loss characteristics of the laminated LC filter shown in FIG.

7 is a graph showing attenuation characteristics and reflection loss characteristics in a high frequency range of the laminated LC filter shown in FIG.

FIG. 8 is an exploded perspective view showing a conventional laminated LC filter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Band pass filter 2a-2k ... Dielectric sheet 4, 5, 6 ... Strip line 7, 14 ... Input / output capacitor electrode 8-10 ... Parallel capacitor electrode 11-13 ... Ground electrode R1, R2, R3 ... LC resonator

Claims (2)

[Claims] 1. A laminated LC filter having at least three LC resonators built-in, wherein at least one of the three LC resonators has a stripline disposed at a dielectric layer. A laminated LC filter, which is different from the stacking direction in the arrangement position of the strip lines of the remaining LC resonators. 2. A laminated LC filter having at least three LC resonators built-in, wherein a first dielectric strip having a first LC resonator strip line and a third LC resonator strip line provided on a surface thereof. Layer and a second dielectric layer having a stripline of the second LC resonator provided on the surface thereof, wherein the stripline of the first LC resonator and the stripline of the second LC resonator are electromagnetic. A laminated LC filter, wherein the strip lines of the second LC resonator and the strip lines of the third LC resonator are electromagnetically coupled to each other.