JP2006140567A - Multilayer dielectric filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a multilayer dielectric filter exhibiting excellent passing characteristics in which the size can be reduced. <P>SOLUTION: In the multilayer dielectric filter where a pair of electromagnetically coupled quarter-wavelength strip line resonators are provided in a multilayer block 14 produced by integrating a plurality of dielectric sheets laid in layers, the pair of quarter-wavelength strip line resonators comprise a pair of resonance electrodes 1 and 2 consisting of short-circuited end strip lines formed on the same plane, capacitor forming electrodes 3 and 4 provided under the resonance electrodes 1 and 2 in correspondence thereto, and via hole conductor portions 5 and 6 provided between the resonance electrodes 1, 2 and the capacitor forming electrodes 3, 4 in order to connect them. The capacitor forming electrodes 3 and 4 are connected, respectively, with I/O electrodes 10 and 11 and a strip line 7 corresponding to half-wavelength is provided above the pair of resonance electrodes 1 and 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a multilayer dielectric filter in which a resonator is formed in a multilayer block in which a plurality of dielectric sheets are stacked and integrated.

  In recent years, with the diversification of wireless communication systems such as mobile phones, there has been a demand for miniaturization and high performance of multilayer dielectric filters.

  In particular, in a reception filter such as a band-pass filter for a high-frequency circuit of a cellular phone, a steep attenuation characteristic is required on the high-frequency side of the pass band.

  FIG. 13 is a perspective view showing a conventional multilayer dielectric filter. The multilayer dielectric filter shown in FIG. 13 has a 1/4 wavelength strip line (where 1/4 wavelength is the center of the passband) in the multilayer block 29 in which a plurality of dielectric sheets are stacked and integrated. The first and second resonance electrodes 21 and 22 are provided. The first and second resonance electrodes 21 and 22 are each a wavelength corresponding to ¼ of the wavelength at the frequency. An interstage coupling conductor layer 24 is provided below the first and second resonance electrodes 21 and 22. A lower shield electrode 26 is provided below the interstage coupling conductor layer 24.

  Above the first and second resonance electrodes 21 and 22, a capacitance forming electrode 23 for forming a capacitance with these electrodes is provided. An upper shield electrode 25 is provided on the capacitance forming electrode 23. On the side surface of the laminate block 29, an input / output electrode 27 connected to the resonance electrode 21 and an input / output electrode 28 connected to the resonance electrode 22 are provided.

  The capacitance forming electrode 23 is a ground electrode formed on the back surface of the multilayer block 29, and the first and second resonance electrodes 21 and 22 are an upper portion and a ground electrode formed on the front surface of the multilayer block 29. The lower shield electrodes 25, 26 are connected to both the back and front surfaces of the laminate block 29.

FIG. 14 is an equivalent circuit diagram of the conventional multilayer dielectric filter shown in FIG. As shown in FIG. 14, the resonator formed by the first and second resonance electrodes 21 and 22 is shown as LC parallel resonators L1 and L2. As shown in FIG. 14, the LC parallel resonator L1 composed of the first resonance electrode and the LC parallel resonator L2 composed of the second resonance electrode are electromagnetically coupled to each other. An inductance L _in is formed from the conductor portion 21 a of the resonance electrode 21, and an inductance L _out is formed from the conductor portion 22 a of the resonance electrode 22. An interstage capacitor CS is formed between the first resonance electrode 21 and the interstage coupling conductor layer 24 and between the second resonance electrode 22 and the interstage coupling conductor layer 24. A capacitor CR is formed between the first resonance electrode 21 and the capacitance forming electrode 23 and between the second resonance electrode 22 and the capacitance forming electrode 23.

FIG. 15 is a diagram showing frequency characteristics of the conventional multilayer dielectric filter shown in FIG. Here, S ₂₁ is the amount of passage from the input / output electrode 27 (input terminal 1) to the input / output electrode 28 (output terminal 2), and S ₁₁ is the amount of reflection at the input / output electrode 27 (input terminal 1). As shown in FIG. 15, this conventional multilayer dielectric filter has a pass band in the vicinity of 2.4 GHz, but the passage amount S ₂₁ is large in the portion shown in the region A on the higher frequency side than this pass band. It can be seen that the attenuation is not sufficient.

  In Patent Document 1, a multilayer dielectric filter is proposed in which four resonant electrodes are formed on the same plane and have four-stage quarter-wavelength stripline resonators. In such a multilayer dielectric filter, the resonant electrodes on both sides and the resonant electrodes adjacent to the resonant electrodes are close to each other and electromagnetically coupled to form an attenuation pole near the high frequency side of the passband. A steep attenuation characteristic is realized.

  However, such a multilayer dielectric filter has a problem that it cannot be downsized because it is necessary to provide a four-stage quarter-wave stripline resonator.

In Patent Document 2, an LC series resonance circuit is configured by an inductance formed by a via hole conductor and a capacitance of the strip line capacitively coupled conductor layer by coupling the stripline conductor layer and the stripline capacitively coupled conductor layer via a via hole. Then, it has been proposed to shift the position of the resonance peak generated in the high frequency region, thereby attenuating the harmonic component of a specific frequency. However, even with such a method, there is a problem that the attenuation on the high frequency side near the passband is not sufficient when the interval between the plurality of stripline conductor layers is further reduced in order to reduce the size of the multilayer dielectric filter. there were.
JP-A-11-191702 JP-A-11-195901

  An object of the present invention is to provide a multilayer dielectric filter in which a pair of quarter-wave stripline resonators electromagnetically coupled to each other are provided in a multilayer block in which a plurality of dielectric sheets are laminated and integrated. It is an object of the present invention to provide a multilayer dielectric filter that can be miniaturized and has excellent pass characteristics.

  The multilayer dielectric filter of the present invention is a multilayer type in which a pair of quarter-wave stripline resonators electromagnetically coupled to each other are provided in a multilayer block in which a plurality of dielectric sheets are stacked and integrated. A dielectric filter, and a pair of quarter-wave stripline resonators are provided corresponding to a pair of resonant electrodes composed of short-circuited short-circuited striplines formed in the same plane and below the resonant electrodes And a via-hole conductor provided between the resonance electrode and the capacitance forming electrode, and an input / output electrode is connected to the capacitance forming electrode. A strip line corresponding to ½ wavelength is provided above the resonance electrode. Here, the ½ wavelength is a wavelength corresponding to ½ of the wavelength at the center frequency of the passband. Further, no electrode other than the half-wavelength equivalent strip line is formed between the resonance electrode and the upper shield electrode.

  In the present invention, the strip line corresponding to ½ wavelength provided above the resonant electrode is electromagnetically coupled to each of the resonators formed from the lower resonant electrode. For this reason, an attenuation pole is formed in a region having a frequency about twice as high as the pass band, which is on the high frequency side of the pass band, by a resonator composed of a strip line corresponding to ½ wavelength. For this reason, it can be set as the filter excellent in the passage characteristic.

  In the present invention, the quarter-wavelength stripline resonator is composed of a resonance electrode, a capacitor forming electrode, and a via-hole conductor portion connecting between them, and enters the capacitor forming electrode. The output electrode is connected. For this reason, it is possible to control the shift of the peak of the spurious resonance due to the LC series resonance by changing the value of the inductance by the via-hole conductor without changing the degree of the capacitive coupling between the strip lines. Therefore, a bandpass filter having a wide pass bandwidth that can be reduced in size or thickness can be obtained.

  In the present invention, the input / output electrodes are preferably formed as side via conductors in the laminate block. Moreover, it is preferable that the uppermost part of the input / output electrode is formed at a position lower than the resonance electrode. In the present invention, since the input / output electrodes are connected to the capacitance forming electrodes connected to the resonance electrodes via the side via conductor portions, the input / output electrodes can be formed as side via conductors inside the multilayer block. it can. For this reason, it is not necessary to form the input / output electrodes on the outer peripheral surface of the laminate block, and the size can be further reduced.

  Further, by forming the input / output electrode so that the uppermost portion of the input / output electrode is positioned lower than the resonance electrode, it is not necessary to provide a space for forming the input / output electrode on the surface on which the resonance electrode is formed. Miniaturization can be achieved.

  In the present invention, the length of the resonant electrode in the quarter-wavelength stripline resonator (the length from the short-circuited end surface of the short-circuited stripline to the tail of the quarter-wavelength stripline resonator) When the length of the strip line corresponding to X and ½ wavelength is 2Y (here, the length in the longitudinal direction of the laminated body of the ½ wavelength equivalent strip line is Y), 1.6 ≦ 2Y / It is preferable that a strip line corresponding to ½ wavelength is formed so as to satisfy the relationship of X ≦ 2.0. By setting the value of 2Y / X to 1.6 or more, it is possible to effectively increase the attenuation at a frequency that is approximately twice the passband. On the other hand, if the value of 2Y / X is larger than 2, the space for providing the half-wave strip line becomes large, and the size may not be sufficiently reduced.

  According to the present invention, a multilayer dielectric filter that can be downsized and has excellent pass characteristics can be obtained.

  FIG. 1 is a perspective view showing a multilayer dielectric filter according to an embodiment of the present invention. The multilayer dielectric filter shown in FIG. 1 is configured by forming a conductor layer in a multilayer block 14 in which a plurality of dielectric sheets are laminated and integrated. A laminated dielectric filter as shown in FIG. 1 can be produced by forming a conductor layer on the surface of the dielectric sheet and laminating and integrating the dielectric sheets on which the conductor layer is formed.

  Referring to FIG. 1, in laminated body block 14, a first resonant electrode 1 made of a quarter-wave strip line and a second resonant electrode 2 made of a quarter-wave strip line are in the same plane. Is formed. A first capacitance forming electrode 3 is provided below the first resonance electrode 1, and a second capacitance forming electrode 4 is provided below the second resonance electrode 2. A via hole conductor portion 5 is provided between the first resonance electrode 1 and the first capacitance forming electrode 3, and the first resonance electrode and the first capacitance forming electrode are provided by the via hole conductor portion 5. It is connected.

  Similarly, a second via-hole conductor portion 6 is provided between the first resonant electrode 2 and the second capacitance forming electrode 4, and the second via-hole conductor portion 6 allows the second resonant electrode 2 to be connected to the second resonant electrode 2. The second capacitance forming electrode 4 is connected.

  The input / output electrode 10 is formed as a side via conductor in the multilayer block 14 so as to be connected to the first capacitance forming electrode 3. Similarly, the input / output electrode 11 is formed as a side via conductor in the dielectric block 14 so as to be connected to the second capacitance forming electrode 4.

  A lower shield electrode 8 is provided below the first capacitor forming electrode 3 and the second capacitor forming electrode 4.

  Above the first resonance electrode 1 and the second resonance electrode 2, a strip line 7 corresponding to ½ wavelength is provided. An upper shield electrode 9 is provided above the strip line 7 corresponding to ½ wavelength. Here, no electrode structure other than the strip line 7 corresponding to ½ wavelength is formed between the resonance electrodes 1 and 2 and the upper shield electrode 9.

  One of the input electrodes 10 and 11 can be an input electrode, and the other can be an output electrode. In addition, ground terminal electrodes (not shown) are formed on the side surfaces 14 a and 14 b of the laminate block 14. The upper shield electrode 9 and the lower shield electrode 8 are connected to the ground terminal electrode, and the resonance electrodes 1 and 2 are connected to one of the ground terminals (in FIG. 1, connected to the surface 14b).

  FIG. 2 is a transverse cross-sectional view of the multilayer dielectric filter shown in FIG. As shown in FIG. 2, the input / output electrodes 10 and 11 are connected to the first capacitor forming electrode 3 and the second capacitor forming electrode 4, respectively, but the uppermost portions thereof are the first and second electrodes. The resonance electrodes 1 and 2 are formed to be lower than the position.

  Further, the strip line 7 corresponding to ½ wavelength is provided so as to overlap with the first and second resonance electrodes 1 and 2, respectively.

  3 is a longitudinal sectional view of the multilayer dielectric filter shown in FIG. As shown in FIG. 3, the input / output electrode 10 is provided substantially at the center of the laminated body block 14. Although not shown in FIG. 3, the input / output electrode 11 is also provided substantially at the center of the multilayer block 14.

  A to G shown in FIG. 3 indicate portions corresponding to the surface of each dielectric sheet constituting the laminated body block 14. Since the laminate block 14 is formed by laminating and integrating dielectric sheets, such a surface cannot be recognized in the laminate block, but is displayed as a virtual plane.

  FIG. 4A is a plan view showing a portion corresponding to the surface A shown in FIG. In this portion, a marker 14e for identifying the laminated dielectric filter is displayed.

  FIG. 4B is a plan view showing portions corresponding to the surface B and the surface F shown in FIG. As shown in FIG. 4B, both ends of the lower shield electrode 8 and the upper shield electrode 9 are connected to the ground terminal electrodes 12 and 13, respectively.

  FIG. 4C is a plan view showing a portion corresponding to the surface C shown in FIG. As shown in FIG. 4C, the strip line 7 corresponding to ½ wavelength is not connected to the ground terminal electrodes 12 and 13.

  FIG.5 (d) is a top view which shows the part corresponded to the surface D shown in FIG. As shown in FIG. 5 (d), one end of the first and second resonance electrodes is exposed on the side surface of the multilayer block and is connected to the external electrode 13. Accordingly, the quarter-wave strip line constituting the resonant electrodes 1 and 2 is a short-circuited strip line. Further, the other ends of the first and second resonance electrodes 1 and 2 are slightly widened, and via-hole conductor portions 5 and 6 are formed in the wide region.

  FIG. 5E is a plan view showing a portion corresponding to the surface E shown in FIG. As shown in FIG. 5E, the first and second capacitance forming electrodes 3 and 4 are not connected to the ground terminal electrodes 12 and 13. Via hole conductor portions 5 and 6 are connected to the other ends of the first and second capacitance forming electrodes 3 and 4, respectively. An input / output electrode 10 is connected to the first capacitance forming electrode 3, and an input / output electrode 11 is connected to the second capacitance forming electrode 4.

  FIG. 5F is a plan view showing a portion corresponding to the surface G shown in FIG. As shown in FIG. 5 (f), the input / output electrodes 10 and 11 and the ground terminal electrodes 12 and 13 are exposed at the bottom of the multilayer dielectric filter so that they can be soldered to the substrate. It has become.

FIG. 6 is an equivalent circuit diagram of the multilayer dielectric filter of the embodiment shown in FIG. In FIG. 6, the resonator composed of the resonance electrodes 1 and 2, the capacitance forming electrodes 3 and 4, and the via-hole conductor portions 5 and 6 are illustrated as LC parallel resonators L1 and L2. These resonators are electromagnetically coupled to each other as indicated by M. As shown in FIG. 6, the input / output electrodes 10 and 11 constitute an inductance L _in on the input side and L _out on the output side.

  A capacitor CR is formed between the capacitance forming electrodes 3 and 4 and the lower shield electrode 8. A capacitor CS is formed between the resonance electrodes 1 and 2 and the strip line 7 corresponding to a half wavelength. A capacitor C3 is formed between the strip line 7 and the upper shield electrode 9 corresponding to ½ wavelength.

  In FIG. 6, a resonance circuit (portion surrounded by a dotted line) composed of a strip line 7 corresponding to ½ wavelength is shown as an LC parallel resonator, which is the resonance of the first resonance electrode. As indicated by M, the resonator L1 and the resonator L2 of the second resonance electrode are electromagnetically coupled.

FIG. 7 is a diagram showing frequency characteristics of the multilayer dielectric filter of the example of the present invention. Here, S ₂₁ is the amount of passage from the input terminal 1 (input / output electrode 10) to the output terminal 2 (input / output electrode 11), and S ₁₁ is the amount of reflection at the input terminal 1 (input / output electrode 10). . The multilayer dielectric filter has a size of 1.6 mm × 0.8 mm and a pass band of 2.4 GHz.

As shown in FIG. 7, in the frequency region (4 GHz to 5.5 GHz) which is about twice the pass band of 2.4 GHz, the value of the passing amount S ₂₁ is rapidly attenuated (−50 dB or less at 4 GHz). It can be seen that an attenuation pole is formed. It can be seen that the formation of the attenuation pole can attenuate the pass on the high frequency side of the pass band, and can provide a filter having excellent pass characteristics.

  FIG. 10 shows the length in the longitudinal direction of the laminate 14 of the strip line 7 corresponding to ½ wavelength with respect to the length X of the resonant electrodes 1 and 2 in the ¼ wavelength strip line resonator in the embodiment of the present invention. The frequency characteristics when Y is changed are shown. Specifically, the length X of the resonant electrodes 1 and 2 in the quarter-wavelength stripline resonator is 1.5 mm, and the length in the longitudinal direction of the laminate 14 of the stripline 7 corresponding to the half-wavelength is The thickness was changed to 1.1 mm, 1.2 mm, 1.3 mm, and 1.4 mm. In addition, the length of the resonant electrodes 1 and 2 in the quarter-wavelength stripline resonator is X shown in FIG. Y shown in FIG. The size of the multilayer dielectric filter is 1.6 mm × 0.8 mm as described above, and the dielectric constant of the dielectric is 90.

As shown in FIG. 10, the passing amount S ₂₁ at 5GHz vicinity is about twice the frequency of the pass band to or less -25dB is longitudinal in the laminate 14 of 1/2-wavelength correspondence stripline 7 It can be seen that the length Y in the direction needs to be 1.2 mm or more. If the value of 2Y / X is larger than 2, a large space is required as a space for providing the strip line 7 corresponding to ½ wavelength. For this reason, the value of 2Y / X is preferably 2 or less.

  From the above, it is preferable that the strip line 7 corresponding to ½ wavelength is formed so that the value of 2Y / X satisfies the relationship of 1.6 ≦ 2Y / X ≦ 2.0. Recognize.

  In FIG. 11, the distance D between the strip line 7 corresponding to the half wavelength shown in FIG. 3 and the first and second resonant electrodes 1 and 2 in the quarter wavelength strip line type resonator is changed. The frequency characteristics are shown. The size of the multilayer dielectric filter is 1.6 mm × 0.8 mm as described above, and the dielectric constant of the dielectric is 90.

  As shown in FIG. 11, when D is 0.03 mm or less, it can be seen that the passband is widened and ripples are generated. This is because the electromagnetic coupling between the strip line 7 corresponding to 1/2 wavelength and the resonance electrodes 1 and 2 in the 1/4 wavelength strip line type resonator is too strong.

It can also be seen that when D is 0.06 mm or more, S ₂₁ becomes smaller than −3 dB at 2.4 GHz, and the insertion loss increases. This is because the electromagnetic coupling between the strip line 7 corresponding to ½ wavelength and the resonance electrodes 1 and 2 in the ¼ wavelength strip line type resonator is too weak.

  From the above, it is understood that when the dielectric constant is 90, D is preferably 0.04 mm or more and 0.05 mm or less. When the dielectric constant was 60, simulation was performed in the same manner as described above. As a result, it was found that D is preferably 0.03 mm or more and 0.05 mm or less.

  Accordingly, it is generally understood that D is preferably 0.05 mm or less.

  FIG. 12 is a chart showing a process for producing a multilayer dielectric filter in an example of the present invention. As shown in FIG. 12, a green sheet is first produced. When producing a green sheet, the sheet thickness is set in consideration of the shrinkage rate in the thickness direction during firing.

  Next, the produced green sheet is cut into a size of, for example, 100 mm × 100 mm.

  Next, a via hole is formed in a necessary portion of each green sheet. The via hole is formed using, for example, an NC puncher.

  Next, a conductor is embedded in the formed via hole using Ag paste or the like.

  Next, wiring is printed on the surface of the green sheet by screen printing or the like. Green sheets printed with wiring are stacked, pressed by a method such as isostatic pressing, and then cut. For cutting, a dicing saw or the like is used to cut the device size.

  Next, external electrodes are formed on the device-sized laminate by a method such as screen printing.

  Next, it is fired by placing it in a box-type electric furnace or the like. Firing is performed at 900 ° C. for about 5 hours, for example.

  The process shown in FIG. 12 shows an example of a manufacturing process, and the laminated dielectric filter of the present invention is not limited to such a manufacturing process.

1 is a perspective view showing a multilayer dielectric filter according to an embodiment of the present invention. 1 is a transverse cross-sectional view showing a multilayer dielectric filter according to an embodiment of the present invention. 1 is a longitudinal sectional view showing a multilayer dielectric filter according to an embodiment of the present invention. The top view which shows the part corresponded to the surface A (a), the surface B, the surface F (b), and the surface C (c) shown in FIG. The top view which shows the part corresponded to the surface D (d), surface E (e), and surface G (f) shown in FIG. FIG. 2 is an equivalent circuit diagram of the multilayer dielectric filter of the embodiment shown in FIG. 1. The figure which shows the frequency characteristic of the laminated dielectric filter of the Example of this invention. The top view which shows the length X of the resonant electrode in a quarter wavelength stripline type | mold resonator. The figure which shows the length Y of the longitudinal direction of the laminated body of the stripline corresponded to 1/2 wavelength. The figure which shows the frequency characteristic when the length Y of the longitudinal direction of the laminated body of the stripline equivalent to 1/2 wavelength is changed. The figure which shows a frequency characteristic when the distance D between the stripline equivalent to 1/2 wavelength and the 1st and 2nd resonance electrode is changed. The figure which shows the process which produces the laminated dielectric filter in the Example of this invention. The perspective view which shows the conventional laminated dielectric filter. FIG. 14 is an equivalent circuit diagram of the conventional multilayer dielectric filter shown in FIG. 13. The figure which shows the frequency characteristic of the conventional laminated dielectric filter shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 ... Resonant electrode which consists of 1/4 wavelength strip line 3, 4 ... Electrode for capacity | capacitance formation 5, 6 ... Via-hole conductor part 7 ... Strip line equivalent to 1/2 wavelength 8 ... Lower shield electrode 9 ... Upper shield electrode 10 , 11 ... Input / output electrodes 12, 13 ... Ground terminal electrodes 14 ... Laminated body blocks 14a to 14d ... Side surfaces of the laminated body block

Claims (3)

A laminated dielectric filter in which a pair of quarter-wave stripline resonators electromagnetically coupled to each other is provided in a laminated body block in which a plurality of dielectric sheets are laminated and integrated,
The pair of quarter-wave stripline resonators is provided for a capacitance formation provided corresponding to a pair of resonant electrodes formed of short-circuited short-circuited striplines formed in the same plane and below the resonant electrodes, respectively. An electrode and a via-hole conductor provided between the resonance electrode and the capacitance forming electrode, and an input / output electrode is connected to the capacitance forming electrode;
A laminated dielectric filter, wherein a strip line corresponding to ½ wavelength is provided above the pair of resonance electrodes.   The input / output electrode is formed as a side via conductor in the multilayer block, and the input / output electrode is formed so that the uppermost portion of the input / output electrode is positioned lower than the resonance electrode. The multilayer dielectric filter according to claim 1. When the resonator length of the ¼ wavelength stripline resonator is X and the length of the stripline corresponding to the ½ wavelength is 2Y,
1.6 ≦ 2Y / X ≦ 2.0
The multilayer dielectric filter according to claim 1, wherein a strip line corresponding to the ½ wavelength is formed so as to satisfy the above relationship.

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