JP2007124172A - High-frequency low pass filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-frequency low pass filter enabling good attenuation in a pass rejection region, by sufficiently grounding an earth electrode for use as a receiving electrode of a capacitor electrode. <P>SOLUTION: The high-frequency low pass filter includes a first dielectric substrate 2a having the earth electrode formed on the surface; a second dielectric substrate 2b having a first capacitor electrode 4, a second capacitor electrode 5, a third capacitor electrode 6, and a fourth capacitor electrode 7 formed on the surface; and a third dielectric substrate having a first coil electrode 10a, a second coil electrode 10b, and a third coil electrode 10c formed in series on the surface in a meander shape. Thus, a laminate is formed in the above order. The earth electrode is configured of at least two earth electrodes so as to divide an area opposite to the first capacitor electrode from an area opposite to the fourth capacitor area. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a high-frequency low-pass filter formed by laminating a dielectric substrate on which an inductor and a capacitor electrode are formed.

  Laminating a plurality of dielectric substrates to form a low-pass filter is, for example, more commonly performed as described in Patent Document 1.

  FIG. 5 is an exploded perspective view showing an embodiment of a conventional high-frequency low-pass filter formed by laminating a dielectric substrate on which an inductor and a capacitor electrode are formed. The high-frequency low-pass filter 1 is formed by laminating dielectric substrates 2a, 2b, 2c, and 2d. A ground electrode 3 is formed on the entire surface of the dielectric substrate 2a except for a part of the outer peripheral end face. Further, four capacitor electrodes 4, 5, 6, and 7 are formed with the dielectric substrate 2b interposed therebetween. The purpose of these capacitor electrodes 4 to 7 is to form a capacitance with the earth electrode 3. Further, meander-like coil electrodes 10a, 10b, 10c are formed with the dielectric layer 2c interposed therebetween. A dielectric substrate 2d is formed on the coil electrode. The capacitor electrode 5 is connected to the connection point of the coil electrodes 10a and 10b, and the capacitor electrode 6 is connected to the connection point of the coil electrodes 10b and 10c by the via-hole electrodes 8 and 9, respectively.

  A plurality of external ground electrodes and external input / output electrodes are formed on the opposite side surfaces outside the high-frequency low-pass filter 1, and lead terminals 3 a, 3 b, 3 d, 3 e, 3f is connected to the external ground electrodes 11a and 11b, and the ends of the capacitor electrodes 4 and 7 that are not connected to the lead electrodes 4a and 7a and the coil electrodes 10a and 10c are connected to the external input / output electrodes 12a and 12b. . The high-frequency low-pass filter 1 constitutes a circuit in which three inductors and four capacitors are π-connected.

  This high-frequency low-pass filter is formed by printing each electrode pattern on a dielectric ceramic green sheet, laminating and firing. The external ground electrode and the external input / output electrode are formed by printing after firing.

JP-A-5-259702

  However, in such a high-frequency low-pass filter, the ground electrode is commonly used as the receiving electrode for the four capacitor electrodes, and a large electrode is formed on the dielectric substrate, so that the grounding with the external ground electrode is not sufficient. In particular, unnecessary power transmission is performed between the capacitor electrodes 4 and 7 connected to the input / output external electrodes, and sufficient attenuation cannot be obtained in the pass-blocking region in the frequency characteristics of the high-frequency low-pass filter.

  Therefore, a main object of the present invention is to provide a high-frequency low-pass filter that sufficiently grounds an earth electrode used as a receiving electrode for a capacitor electrode and that can obtain good attenuation in a passage blocking region.

  In order to achieve the above object, the present invention provides a first dielectric substrate having a ground electrode formed on the surface, a first capacitor electrode, a second capacitor electrode, a third capacitor electrode on the surface, And a second dielectric substrate having a fourth capacitor electrode formed thereon, and a third dielectric having a first coil electrode, a second coil electrode, and a third coil electrode formed in a meander shape in series on the surface And a first substrate electrode, a first coil electrode, and a first coil electrode. One end of each of the first capacitor electrode is connected to the first input / output electrode by a lead electrode, and one end of the fourth capacitor electrode and the third coil electrode is connected to the second input / output electrode by a lead electrode, respectively. And said The second capacitor electrode is connected between the first coil electrode and the second coil electrode by a via hole, and the third capacitor electrode is connected to the second coil electrode by a via hole. And the third coil electrode, wherein the ground electrode is opposed to the first capacitor electrode and the fourth capacitor electrode. The present invention provides a high-frequency low-pass filter characterized by comprising at least two ground electrodes so as to divide the region.

  The present invention also provides a fourth dielectric substrate having a first coupling electrode, a second coupling electrode, and a third coupling electrode on the surface, the second dielectric substrate and the third dielectric substrate. A high-frequency low-pass filter between the first capacitor electrode and the second capacitor electrode, wherein the first coupling electrode faces both the first capacitor electrode and the second capacitor electrode. The coupling electrode is opposed to both the second capacitor electrode and the third capacitor electrode, and the third coupling electrode comprises the third capacitor electrode and the fourth capacitor. The present invention relates to the high-frequency low-pass filter, characterized by facing both of the electrodes.

  According to the present invention, by dividing the portion of the ground electrode facing the first and fourth capacitor electrodes so as to be divided, the ground electrode is sufficiently grounded, and the low pass for high frequency with good attenuation characteristics is obtained. A filter can be obtained.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic perspective view showing a first embodiment of the high-frequency low-pass filter of the present invention. FIG. 2 is an exploded perspective view of the embodiment of FIG.

  In this embodiment, the basic structure of the filter is substantially the same as the conventional example in FIG. 5 except for the shape of the ground electrode. The high-frequency low-pass filter 1 is formed by sequentially laminating a first dielectric substrate 2a, a second dielectric substrate 2b, a third dielectric substrate 2c, and a fourth dielectric substrate 2d. On the first dielectric substrate 2a, a ground electrode that characterizes the present invention is formed except for a part of the outer peripheral end face. A first capacitor electrode 4, a second capacitor electrode 5, a third capacitor electrode 6, and a fourth capacitor electrode 7 are formed on the surface of the dielectric substrate 2b. These capacitor electrodes 4 to 7 are intended to form a capacitance with the ground electrode on the first dielectric substrate 2a. Further, three meander-shaped coil electrodes, that is, a first coil electrode 10a, a second coil electrode 10b, a third coil electrode, are formed on the surface of the third dielectric substrate 2c with the third dielectric substrate 2c interposed therebetween. The coil electrodes 10c are connected in series. A fourth dielectric substrate 2d is further formed on the coil electrode.

  The laminated dielectric substrate is preferably provided with a first input / output electrode 12a and a second input / output electrode 12b on the side surfaces, and the first capacitor electrode 4 and the first coil electrode. One end of 10a is connected to the first input / output electrode 12a by an extraction electrode, and one end of the fourth capacitor electrode 7 and the third coil electrode 10c is respectively connected to the second input electrode by the extraction electrode. It is connected to the output electrode 12b. The second capacitor electrode 5 is connected between the first coil electrode 10a and the second coil electrode 10b by a via hole, and the third capacitor electrode 6 is a via hole. Thus, the second coil electrode 10b is connected to the third coil electrode 10c.

  In the present invention, the ground electrode formed on the first dielectric substrate 2a divides the region facing the first capacitor electrode and the region facing the fourth capacitor electrode. At least two earth electrodes, that is, the embodiment shown in FIG. 2, is characterized by comprising an earth electrode 31 and an earth electrode 32. The high-frequency low-pass filter 1 of the present invention constitutes a circuit in which three inductors and four capacitors are π-connected.

  In the embodiment of the high-frequency low-pass filter of the present invention shown in FIG. 1, a plurality of external ground electrodes are formed on opposite side surfaces of the high-frequency low-pass filter, and external input / output electrodes are formed on other opposite side surfaces. . The ground electrodes 31 and 32 are connected to the external ground electrodes 11a and 11b by lead electrodes.

  In the high-frequency low-pass filter of the present invention, the ground electrode formed on the first dielectric substrate 2a is divided into a region facing the first capacitor electrode and a region facing the fourth capacitor electrode. Since it is configured by at least two ground electrodes so as to be divided, it is possible to obtain a high-frequency low-pass filter having satisfactory attenuation characteristics by sufficiently grounding each ground electrode.

  FIG. 4 shows attenuation characteristics of an embodiment of the high-frequency low-pass filter of the present invention. The horizontal axis represents frequency, and the vertical axis represents attenuation. The passband of the filter in the present embodiment is 3.4 GHz to 3.8 GHz. The attenuation characteristics normally required for a low-pass filter are twice and three times the frequency of the passband. Therefore, it can be seen that the attenuation characteristics from 6.8 GHz to 7.6 GHz at 2 × f and from 10.2 GHz to 11.4 GHz at 3 × f are about −50 dB.

  On the other hand, FIG. 6 shows the attenuation characteristics of the conventional high-frequency low-pass filter shown in FIG. The basic configuration of the filter in FIG. 5 is substantially the same as that of this embodiment except for the shape of the ground electrode. FIG. 6 shows that the attenuation characteristics of 2xf and 3xf are only about -35 dB to -30 dB. Therefore, a good attenuation characteristic can be obtained by dividing the ground electrode of the present embodiment so as to divide the portions facing the first and fourth capacitor electrodes.

  The ground electrode of the present invention may be formed so as to be divided into a region opposed to the first capacitor electrode and a region opposed to the fourth capacitor electrode, as shown in FIG. One earth electrode 31 may be further composed of a plurality of earth electrodes, and the second earth electrode 31 may be further composed of a plurality of earth electrodes. Moreover, it is good also as a form divided into two, the earth electrode formed in the area | region facing the said 1st-3rd capacitor electrode, and the earth electrode formed in the area | region facing the said 4th capacitor electrode. Furthermore, it is good also as a form divided into two, the earth electrode formed in the area | region facing the said 1st electrode for capacitors, and the earth electrode formed in the area | region facing the said 2nd-4th capacitor electrode.

  FIG. 3 is an exploded perspective view showing a second embodiment of the high-frequency low-pass filter of the present invention. In the present embodiment, in addition to the configuration of the high-frequency low-pass filter shown in FIG. 2, a fourth dielectric substrate 2e is further provided between the second dielectric substrate 2b and the third dielectric substrate 2c. It becomes the composition. The surface of the fourth dielectric substrate 2e has a first coupling electrode 20, a second coupling electrode 21, and a third coupling electrode 22, and the first coupling electrode 20 The first capacitor electrode 4 and the second capacitor electrode 5 are opposed to each other, and the second coupling electrode 21 is connected to the second capacitor electrode 5 and the third capacitor electrode 6. The third coupling electrode 22 is opposed to both the third capacitor electrode 6 and the fourth capacitor electrode 7.

  Here, the first coupling electrode 20 constitutes a parallel resonator with the first coil electrode 10a, and the second coupling electrode 21 constitutes a parallel resonator with the second coil electrode 10b. Further, the third coupling electrode 22 forms a parallel resonator with the third coil electrode 10c. These parallel resonators can further improve the attenuation characteristics of the target frequency band by arbitrarily setting each resonance frequency, and can constitute a low-pass filter with higher attenuation.

  The divided ground electrodes are not limited to the shapes shown in FIGS. 2 and 3 and can be arbitrarily set depending on the capacitor electrode shape or the electrical characteristics.

  The high-frequency low-pass filter of the present invention can be obtained by changing the electrode print pattern in the same manner as the known conventional multilayer dielectric filter manufacturing method using the green sheet method.

Example 1
A high-frequency low-pass filter having the shape and electrode pattern shown in FIG. 2 was produced by a conventional method of printing and firing an electrode pattern on a green sheet. The frequency characteristics are shown in FIG. The design passband of the filter is 3.4 GHz to 3.8 GHz. The attenuation characteristics normally required of a low-pass filter are twice and three times the frequency of the passband, and see the attenuation characteristics from 2xf 6.8 GHz to 7.6 GHz and 3xf 10.2 GHz to 11.4 GHz. And about -50 dB. It turns out that it is excellent in the attenuation | damping characteristic compared with the comparative example shown next.

(Comparative Example 1)
A high-frequency low-pass filter as shown in FIG. 5 different from Example 1 only in the shape of the ground electrode was produced, and the frequency characteristics thereof were measured. The results are shown in FIG. It can be seen that the attenuation characteristics of 2xf and 3xf are only about -35 dB to -30 dB. Therefore, it can be seen that a good attenuation characteristic can be obtained by dividing the ground electrode so as to divide the portions of the ground electrode facing the first and fourth capacitor electrodes as in the present invention.

1 is an external perspective view of an embodiment of a high-frequency low-pass filter according to the present invention. It is a disassembled perspective view of one Embodiment of the low-pass filter for high frequencies of this invention. It is a disassembled perspective view of other embodiment of the low-pass filter for high frequencies of this invention. FIG. 3 is a frequency characteristic diagram of the high-frequency low-pass filter of the present invention obtained in Example 1. It is a disassembled perspective view of the conventional high frequency low pass filter. 6 is a frequency characteristic diagram of a conventional high-frequency low-pass filter obtained in Comparative Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 High frequency low pass filter 2a 1st dielectric substrate 2b 2nd dielectric substrate 2c 3rd dielectric substrate 2d Dielectric substrate 2e laminated | stacked on the 2nd dielectric substrate 4th dielectric substrate 3 Ground electrode 4 First capacitor electrode 5 Second capacitor electrode 6 Third capacitor electrode 7 Fourth capacitor electrode 8, 9 Via hole 10a First coil electrode 10b Second coil electrode 10c Third Coil electrodes 11a, 11b External ground electrode 12a First input / output electrode 12b Second input / output electrode 20 First coupling electrode 21 Second coupling electrode 22 Third coupling electrode 31 Ground electrode 32 Ground electrode

Claims (2)

A first dielectric substrate having a ground electrode formed on the surface;
A second dielectric substrate having a first capacitor electrode, a second capacitor electrode, a third capacitor electrode, and a fourth capacitor electrode formed on the surface;
A first dielectric electrode, a second coil electrode, and a third dielectric substrate in which a third coil electrode is formed in a meander shape are stacked in order on the surface,
A laminated dielectric substrate having a first input / output electrode and a second input / output electrode;
One end of each of the first capacitor electrode and the first coil electrode is connected to the first input / output electrode by a lead electrode, and one end of each of the fourth capacitor electrode and the third coil electrode is , Each connected to the second input / output electrode by a lead electrode,
The second capacitor electrode is connected between the first coil electrode and the second coil electrode by a via hole,
The third capacitor electrode is a high-frequency low-pass filter connected between the second coil electrode and the third coil electrode by a via hole,
The high-frequency electrode is characterized in that the ground electrode includes at least two ground electrodes so as to divide a region facing the first capacitor electrode and a region facing the fourth capacitor electrode. Low pass filter. A fourth dielectric substrate having a first coupling electrode, a second coupling electrode, and a third coupling electrode on the surface is interposed between the second dielectric substrate and the third dielectric substrate. The high-frequency low-pass filter has the first coupling electrode facing both the first capacitor electrode and the second capacitor electrode, and the second coupling electrode is Opposing both the second capacitor electrode and the third capacitor electrode, the third coupling electrode is provided on both the third capacitor electrode and the fourth capacitor electrode. The high-frequency low-pass filter according to claim 1, which faces each other.

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