JP3676885B2 - Chip type multilayer filter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a chip-type multilayer filter, and more particularly to a chip-type multilayer filter having two passbands as one element used in mobile communication equipment such as a mobile phone.
[0002]
[Prior art]
Due to the explosive spread of mobile phones and the like in recent years, the frequency band used (for example, 800 MHz band in the PDC system (transmission is 810 to 826 MHz, reception is 940 to 956 MHz), 1.5 GHz band (transmission is 1.429 to 1. 453 GHz, reception 1.477 to 1.501 GHz), and 1.9 GHz band (1.895 to 1.918 GHz for both transmission and reception) in the PHS system) and the frequency band of two systems with one mobile communication terminal (For example, as described above, the 800 MHz band used in the PDC system and the 1.9 GHz band used in the PHS system) are required, and conventionally, two filters corresponding to each frequency band are used. ing.
[0003]
In addition, dielectric filters using TEM mode resonance are mainly used as RF filters used in conventional mobile phones and the like. By the way, a filter using TEM mode resonance has not only one pass band set to a predetermined specification value, but also a pass band having a frequency that is substantially an odd multiple of that frequency. This is a problem because unnecessary radiation (mainly three times the frequency) generated by amplifier distortion is passed as it is. In order to solve such a problem, for example, as described in Japanese Examined Patent Publication No. 1-33402, an LPF for shifting an approximately odd multiple pass band to a high frequency range or removing an approximately odd multiple frequency ( This is addressed by incorporating a low-pass filter.
[0004]
On the other hand, in recent years, mobile communication devices such as mobile phones have been reduced in size and weight, and dielectric filters have also been reduced in size. In particular, a chip-type filter in which dielectrics and electrodes are alternately stacked can be particularly downsized and is currently in practical use.
[0005]
[Problems to be solved by the invention]
However, the conventional dielectric filter as described above has the following problems.
[0006]
(1) In order to support two systems, two filters are required, which hinders the downsizing of the set, and impedance matching means is further required to connect the two filters to each other.
[0007]
(2) If necessary, some means for suppressing a frequency band that is approximately an odd multiple of the desired frequency is separately required.
[0008]
Therefore, the present invention provides a novel multilayer chip type that has two passbands used in a mobile phone with one element, suppresses a frequency band that is approximately an odd multiple of a desired frequency, and is advantageous for surface mounting and miniaturization. A dielectric filter is provided.
[0009]
[Means for Solving the Problems]
Specifically, it is achieved by the following configurations (1) to (3).
[0010]
(1) In a chip-type multilayer filter in which a center conductor serving as a resonator is formed in at least two layers inside a dielectric, and an internal ground electrode is provided between conductors of each layer, and an external ground electrode is provided on an external surface.
Arbitrary frequency band lower than three times the fundamental wave and fundamental wave by narrowing the distance between the ground electrodes sandwiching the short-circuit-end-side conductor as compared with the distance between the ground electrodes sandwiching another conductor parallel to the laminated surface A chip-type multilayer filter characterized by having two pass bands.
[0011]
(2) In a chip-type multilayer filter in which a central conductor serving as a resonator is formed in at least two layers inside a dielectric, an internal ground electrode is provided between conductors of each layer, and an external ground electrode is provided on an external surface.
By making the width of the conductor on the short-circuited end side wider than the width of other conductors parallel to the laminated surface, it has any two passbands consisting of a fundamental wave and a frequency band lower than three times the fundamental wave. A chip-type multilayer filter characterized by the above.
[0012]
With the configurations (1) and (2), it is possible to shift a frequency that is approximately three times the set frequency in question to the low frequency side, and it is possible to obtain a filter having any two pass bands.
[0013]
(3) The chip-type multilayer filter according to (1), wherein the width of the conductor on the short-circuit end side is made wider than the width of another conductor parallel to the laminated surface.
[0014]
As compared with (1) and (2), the frequency about three times the set frequency can be further shifted to the low frequency side, and a filter having two closer passbands can be obtained.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
The chip-type multilayer filter according to the present invention will be specifically described below with reference to FIGS.
[0016]
FIG. 1A is a perspective view schematically showing the configuration of the center conductor and internal electrodes of the chip-type multilayer filter according to the present invention. A central conductor serving as a resonator includes a conductor 11, a conductor 12, and a conductor 13 connecting the conductors. The conductor 11 is configured in parallel to the laminated surface, and is short-circuited (hereinafter referred to as a short-circuit side conductor) connected to the external ground electrode (FIG. 1B) 22 as shown below. The conductor 12 is configured in parallel to the laminated surface and has an open end (hereinafter referred to as an open end side conductor). The conductor is further connected to a signal input / output via a signal input / output lead electrode 31. It is configured to be connected to the terminal electrode (FIG. 1 (b) 32), and is adjusted to have a shape in which capacitive coupling occurs to form mutual resonator coupling. Here, in the figure, the signal input / output lead electrode 31 is formed so as to pass through the conductor 12 and the capacitor on the open end side, but the lead electrode may be formed directly from the center conductor. When directly pulling out, it is not always necessary to pull out from the conductor on the open end side, and it may be pulled out from a conductor other than the conductor on the open end side due to design restrictions such as the width of the passband and impedance. The conductor 13 is configured to be perpendicular to the laminated surface and connects the conductors formed parallel to the laminated surface. An internal ground electrode 21 is provided between the conductor 11 and the conductor 12 so as to be parallel to the conductors. When the central conductor is formed over three layers, an internal ground electrode is further required. Therefore, a ground electrode is always provided between the layers of the conductor parallel to the laminated surface. FIG. 1B shows an external perspective view of the chip-type multilayer filter according to FIG. Externally, the signal input / output terminal electrode 32 connected to the signal input / output lead electrode, the internal ground electrode 21 and the conductor 11 are connected, and the external ground electrode 22 not connected to the signal input / output terminal electrode 32 covers the element body. Formed. Here, the signal input / output terminal electrode 32 may have any shape as long as it is formed so as not to be electrically connected to the external ground electrode 22. For example, as shown in FIG. 3 or FIG. 3B, the signal input / output lead electrode is drawn out to a portion not covered by the external ground electrode, and the signal input / output terminal electrode is formed so as not to be connected to the external ground electrode. As shown in FIG. 2B, a convex portion may be provided in a portion where the signal input / output lead electrode is drawn, and a signal input / output terminal electrode may be provided in a part of the convex portion so as not to be connected to the external ground electrode. .
[0017]
The chip type multilayer filter according to the present invention further has the following characteristics in the above chip type multilayer filter.
[0018]
FIG. 1C shows a cross-sectional view taken along line AA ′ of FIG. The distance between the ground electrodes sandwiching the conductor 11, that is, the distance t ₁ between the internal ground electrode 21 and the external ground electrode surface 22 b adjacent to and facing the conductor 11 on the short-circuit end side is the distance between the ground electrodes sandwiching the conductor 12. That is, a configuration that is narrower than the interval t ₂ between the internal ground electrode 21 and the external ground electrode surface 22a that is adjacent to and faces the conductor 12 that is a conductor other than the short-circuit-end-side conductor and is parallel to the laminated surface. It has become. Accordingly, the filter according to the present invention has a low characteristic impedance in the conductor 11, that is, the short-circuit end side conductor among the central conductors constituting the resonator, and in the conductor 12, that is, the open-end side conductor among the center conductors. Can increase its characteristic impedance, and can have a greater wavelength shortening effect for the 3/4 wavelength, which is the higher order mode of the fundamental wave, than for the 1/4 wavelength of the fundamental wave. Can be set to a frequency significantly lower than three times the fundamental wave. Therefore, it is possible to set the resonance of the higher order mode, which is about three times the fundamental wave, which should be a problem as an unnecessary resonance, to a frequency around twice.
[0019]
In particular, when the center conductor is formed of two layers, when the distance between the ground electrodes on the short-circuit end side is t _a and the distance between the ground electrodes on the open end side is t _b , t _a / t _b is 1 / It is preferable that it exists in 10-1 / 2. This is because when the value of t _a / t _b is less than 1/10, there is a restriction on the external design value of the filter (currently miniaturization has progressed, and the size needs to be about 3 to 5 mm × 3 to 5 mm × 2 mm. 1), it is necessary to reduce the thickness of the dielectric forming t ₁ in FIG. 1C, which causes problems in electrical characteristics such as the Q value and in manufacturing. On the other hand, if t _a / t _b exceeds ½, the wavelength shortening effect on the higher-order mode resonance hardly appears, and there arises a problem of passing unnecessary radiation generated by amplifier distortion.
[0020]
The same effect can be obtained with the central conductor constituting the resonator as shown in FIG. That is, in this figure, the width w ₃ of the conductor 14 on the short-circuit end side is the width w ₄ of the conductor 15 that is a conductor other than the conductor on the short-circuit end side and is parallel to the laminated surface (however, in a shape that causes capacitive coupling to occur). It is wider than the adjusted part. This also means that the characteristic impedance of the conductor on the short-circuited end side with a large conductor width is low, so that the characteristic impedance can be changed by changing the distance between the ground conductors sandwiching the conductor. The narrower open end side conductor has a higher characteristic impedance. As a result, the wavelength shortening effect for the 3/4 wavelength, which is the higher order mode of the fundamental wave, can be made larger than that for the 1/4 wavelength of the fundamental wave, so the higher order mode is significantly larger than 3 times the fundamental wave. It is possible to set a low frequency. Here, FIG. 2B shows an external perspective view of the chip-type multilayer filter according to FIG. 2A, and FIG. 2C shows a cross-sectional view taken along line BB ′ of FIG. In the figure, 16 is a conductor, 23 is an internal ground electrode, 24 is an external ground electrode, 33 is a signal input / output lead electrode, and 34 is a signal input / output terminal electrode.
[0021]
In particular, when the central conductor is composed of two layers, w _a / w _b is 2 to 3 when the conductor width on the short-circuit end side is w _a and the conductor width on the open end side is w _b. Is preferred. This causes a problem that when w _a / w _b is less than 2, the wavelength shortening effect on the resonance of the higher-order mode hardly appears, and unnecessary radiation generated by amplifier distortion is allowed to pass. Also, when w _a / w _b exceeds 3, the width of the conductor due to restrictions such as the external design value of the filter (currently downsizing is required and the size needs to be about 3-5 mm × 3-5 mm × 2 mm) This is because it is necessary to make the thickness extremely small, which causes problems in electrical characteristics such as the Q value and manufacturing.
[0022]
Further, as shown in FIG. 3, the two structures are combined, that is, the distance between the ground electrodes sandwiching the conductor on the short-circuit end side (FIG. 3 (c) t ₅ ) is a conductor other than the conductor on the short-circuit end side. distance of the ground electrodes sandwiching the parallel conductors to the stacking surface smaller than in the (FIG. 3 (c) t _6), and the width of the conductor 17 of the short-circuit end side, the laminated surface of a conductor other than the conductor of the short-circuit end side By setting the width to be wider than the width of the conductor 18 which is a parallel conductor, two frequency bands can be made closer to those of the above configuration. Here, FIG. 3B is an external perspective view of the chip-type multilayer filter according to FIG. 3A, and FIG. 3C is a cross-sectional view taken along the line CC ′ of FIG. In the figure, 19 is a conductor, 25 is an internal ground electrode, 26 is an external ground electrode, 35 is a signal input / output lead electrode, and 36 is a signal input / output terminal electrode.
[0023]
Next, the manufacturing method of the present invention will be described with reference to the exploded perspective view of FIG.
[0024]
On the dielectric sheet molded to a predetermined thickness by a doctor blade method or the like, an electrode paste is printed by a screen printing method so as to have a predetermined shape as shown in FIG. 4, for example, 11, 12, 21, 31 in FIG. The dielectric sheet and the dielectric sheet printed with the electrode paste are laminated so as to have a predetermined configuration. Here, the uppermost sheet in the figure is thicker than the other sheets, but as shown in FIG. 4, a predetermined number of dielectric sheets are laminated so as to have the desired thickness. It was produced. The conductor 13 perpendicular to the laminated surface is formed by previously providing a through hole in the dielectric sheet and injecting an electrode paste after the lamination. Then, after cutting to a predetermined size, an electrode paste is formed as an external ground electrode so as to have a predetermined shape on an external surface parallel to the laminated surface and an external surface perpendicular to the laminated surface. Is printed at a predetermined position. Further, the external ground electrode parallel to the laminated surface may be constituted by laminating dielectric sheets on which electrodes are printed, like the internal ground electrode. Further, the signal input / output terminal electrode 32 may be baked by applying an electrode paste by rubber transfer or the like after printing and baking the external ground electrode. Here, although it demonstrated in the sheet construction method, it cannot be overemphasized that it can manufacture also in a printing construction method.
[0025]
The dielectric used is not particularly limited as long as it is a general high-frequency dielectric (having a high dielectric constant and Q value and good temperature characteristics). For example, BaTiO ₃ type. However, it must be possible to sinter at a lower temperature than the conductor material in order to co-fire with the electrode. The conductive material of the electrode paste for forming the central conductor and the electrode is not particularly limited as long as it is a general high-frequency material. For example, Ag, Au, Cu, Ag-Pd, etc. are used. The dielectric layer constituting the chip type filter is not limited to ceramic, but may be a high-frequency resin-based substrate. In this case, the conductor and the electrode are formed of copper foil or the like.
[0026]
Although the center electrode has been described as having two layers as described above, other conductors in which the gap between the ground electrodes sandwiching the conductor on the short-circuited end side is parallel to the laminated surface also for those having three or more layers. The frequency band is lower than three times the fundamental wave and the fundamental wave by narrowing the gap between the ground electrodes sandwiching the gap, or by making the width of the conductor on the short-circuited end side wider than the width of the other conductors. Needless to say, any two passbands can be set.
[0027]
【Example】
Specific examples of the present invention will be described below.
[0028]
(Example 1)
As a sample of Example 1, a chip-type filter having the configuration shown in FIG. 1 was produced by the sheet method as described above. The shape of the obtained chip-type multilayer filter is 5 mm × 5 mm × 1.8 mm, and the dielectric constant εr of the dielectric used is 92. Further, Ag was used as the conductive material for forming the central conductor and the electrode. The distance between the ground electrodes positioned above and below the conductor forming the resonator is 0.2 mm on the short-circuit end side (FIG. 1 (c) t ₁ ) and 1.6 mm on the open end side (FIG. 1 (c) t ₂ ). It is. The conductor width is 0.5 mm on both the short-circuit end side (FIG. 1 (a) w ₁ ) and the open end side (FIG. 1 (a) w ₂ ). Further, as a comparative example, the same configuration as in Example 1 except that the distance between the ground electrodes positioned above and below the conductor forming the resonator is the same distance (0.9 mm) on the open end side and the short-circuit end side. Also made.
[0029]
FIG. 5 shows the electrical characteristics of this example, and FIG. 10 shows the electrical characteristics of the comparative example. In each graph, the X axis represents frequency and the Y axis represents attenuation. Thus, in the comparative example, the second passband is at about 2800 MHz, which is about three times the 930 MHz of the first passband, but in this example, the second passband is about 1950 MHz, It can be seen that the passband is about twice as high as about 950 MHz. Thus, the 3/4 wavelength which is a higher order mode of the fundamental wave than the quarter wavelength of the fundamental wave is obtained only by making the distance between the ground electrodes on the short-circuit end side smaller than the distance between the ground electrodes on the open end side. It can be seen that the effect of shortening the wavelength can be greatly increased. In addition, the configuration of this embodiment can support two systems of the PDC system and the PHS system.
[0030]
(Example 2)
Further, as a sample of Example 2, a chip-type laminate having the same configuration as Example 1 except that the ratio of the distance between the ground electrodes on the short-circuit end side and the distance between the ground electrodes on the open end side was set to 1: 2. A filter is produced and its electrical characteristics are shown in FIG. As a result, the second passband is about 2.7 times as high as 2150 MHz and about 800 MHz of the first passband, and the 3/4 wavelength which is the higher order mode of the fundamental wave than to the 1/4 wavelength of the fundamental wave. It can be seen that the effect of shortening the wavelength can be greatly increased.
[0031]
Example 3
As a sample of Example 3, a chip type filter having the configuration shown in FIG. 2 was produced by the sheet method as described above. Of the conductors forming the resonator, the conductor width on the short-circuit end side (FIG. 2 (a) w ₃ ) is 1.1 mm and the conductor width on the open end side (FIG. 2 (a) w ₄ ) is 0.5 mm. . The distance between the ground electrodes located above and below each conductor is the same (0.9 mm) on both the short-circuited end side (FIG. 2 (c) t ₃ ) and the open end side (FIG. 2 (c) t ₄ ). . The manufacturing method, materials used, and the like are the same as in Example 1.
[0032]
FIG. 7 shows the electrical characteristics of this example. As a result, the first passband is about 830 MHz and the second passband is about 2150 MHz, so that the triple resonance frequency can be shifted to about 2.6 times, and a sufficient effect is obtained.
[0033]
(Example 4)
Further, as a sample of Example 4, a chip-type multilayer filter having the same configuration as that of Example 3 except that the ratio of the conductor width on the short-circuit end side and the conductor width on the open end side was set to 2: 1 was manufactured. The electrical characteristics are shown in FIG. As a result, the second passband is 2700 MHz, which is about 2.7 times as high as the first passband, about 1000 MHz, and the 3/4 wavelength which is the higher order mode of the fundamental wave than the 1/4 wavelength of the fundamental wave. It can be seen that the effect of shortening the wavelength can be greatly increased.
[0034]
(Example 5)
As a sample of Example 5, a chip-type filter having the configuration shown in FIG. 3 was produced by the sheet method as described above. This is a combination of the first and second embodiments. That is, the distance between the ground electrodes sandwiching the conductor constituting the resonator is set differently on the open end side and the short-circuit end side as in the first and second embodiments, and the conductor on the short-circuit end side as in the third and fourth embodiments. Is formed wider than the open end side. Specifically, the distance between the ground electrodes located above and below the conductor forming the resonator is 0.2 mm on the short-circuited end side (FIG. 3 (c) t ₅ ), and the open end side (FIG. 3 (c) t ₆ ) 1.6 mm, the conductor width on the short-circuit end side (FIG. 3 (a) w ₅ ) is 1.1 mm, and the conductor width on the open end side (FIG. 3 (a) w ₆ ) is 0.5 mm. is there. The manufacturing method, materials used, and the like are the same as those in the above embodiments.
[0035]
FIG. 9 shows the electrical characteristics of this example. From this, it can be seen that the first passband is at about 900 MHz and the second passband is at about 1500 MHz. Since the wavelength shortening effect for the 3/4 wavelength, which is the higher order mode of the fundamental wave, can be increased as compared with the two embodiments, two frequency bands used in the PDC method can be provided.
[0036]
【The invention's effect】
The chip type multilayer filter according to the present invention described above has the following effects.
[0037]
(1) Since one element can be used for two types of systems, only one filter is required for two conventional filters, so the set can be downsized.
[0038]
(2) Since one element functions as two filters, a matching circuit for connecting two filters becomes unnecessary.
[0039]
(3) The frequency of the second pass band is set to about twice the frequency of the first pass band, and there is no pass band in about three times the first pass band. Since there is no pass band as much as about 3 times, it is not necessary to take measures against 3rd harmonics.
[Brief description of the drawings]
FIG. 1A is a transparent perspective view showing an example of a schematic configuration of a center conductor and internal electrodes of a chip-type multilayer filter according to the present invention. (B) is an external perspective view of the chip-type multilayer filter according to FIG. (C) is the sectional view on the AA 'line of the same figure (a).
FIG. 2A is a transparent perspective view showing an example of a schematic configuration of a central conductor and internal electrodes of a chip-type multilayer filter according to the present invention. (B) is an external perspective view of the chip-type multilayer filter according to FIG. (C) is the BB 'sectional view taken on the line of the figure (a).
FIG. 3A is a transparent perspective view showing an example of a schematic configuration of a center conductor and internal electrodes of a chip-type multilayer filter according to the present invention. (B) is an external perspective view of the chip-type multilayer filter according to FIG. (C) is CC 'sectional view taken on the line of the figure (a).
FIG. 4 is an exploded perspective view of a chip-type multilayer filter according to the present invention.
5 is a graph showing electrical characteristics of the chip-type multilayer filter according to Example 1. FIG.
6 is a graph showing electrical characteristics of the chip-type multilayer filter according to Example 2. FIG.
7 is a graph showing electrical characteristics of the chip-type multilayer filter according to Example 3. FIG.
8 is a graph showing electrical characteristics of the chip-type multilayer filter according to Example 4. FIG.
9 is a graph showing electrical characteristics of the chip-type multilayer filter according to Example 5. FIG.
FIG. 10 is a diagram showing electrical characteristics of a chip-type multilayer filter according to a comparative example.
[Explanation of symbols]
11, 14, 17: Short-circuit end side conductors 12, 15, 18; Open end-side conductor (conductor other than short-circuit end side)
13, 16, 19; conductor (conductor perpendicular to the laminated surface)
21, 23, 25; internal ground electrodes 22, 24, 26, 22a, 22b; external ground electrodes 31, 33, 35; signal input / output lead electrodes 32, 34, 36; signal input / output terminal electrodes 4;

Claims (2)

In a chip-type multilayer filter in which a central conductor serving as a resonator is formed in at least two layers inside a dielectric, and an internal ground electrode is provided between conductors of each layer, and an external ground electrode is provided on an external surface.
Chip type laminated filter, wherein a distance between the ground electrodes sandwiching the conductor of the short-circuit end side, and narrower than the distance between the ground electrodes sandwiching the other conductors parallel to the stacking plane. Chip type laminated filter according to claim 1, characterized in that the width of the conductor of the short-circuit end side, and wider than the width of the parallel other conductor to the laminated surface.

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