JP2013143675A - Stacked band-pass filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an influence of resonance phenomenon of a parasitic resonance circuit formed by conductive layers for constituting a coupling capacitor.SOLUTION: A band-pass filter 1 includes first and second inter-stage coupling capacitors and a bypass coupling capacitor. The first and the second inter-stage coupling capacitors are configured so as to include a first conductor layer 461 and a second conductor layer 451. The bypass coupling capacitor is configured so as to include a third conductor layer 511 and fourth conductor layers 521A and 521B. The dielectric constant of third dielectric layers 46 to 50 disposed between the first and second inter-stage coupling capacitor and the bypass coupling capacitor is smaller than the dielectric constant of a first dielectric layer 45 disposed between the first conductive layer 461 and the second conductive layer 451, and the dielectric constant of a second dielectric layer 51 disposed between the third conductor layer 511 and the fourth conductor layers 521A and 521B.

Description

  The present invention relates to a laminated band-pass filter including three or more resonators provided in a laminated body having a plurality of laminated dielectric layers.

  In recent years, small wireless communication devices such as cellular phones have built-in other communication devices such as Bluetooth (registered trademark) communication devices and wireless LAN (local area network) communication devices in addition to the original wireless communication device. Things to do are increasing. Therefore, there is a strong demand for downsizing and thinning of a built-in communication device, and there is also a strong demand for downsizing and thinning of electronic components used in the communication device.

  One electronic component in a communication apparatus is a band-pass filter that filters transmission signals and reception signals. This band pass filter is also required to be small and thin. As shown in Patent Documents 1 to 3, as a band-pass filter that can correspond to the frequency band used for various communication devices and can be reduced in size and thickness, it is a stacked layer having a plurality of stacked dielectric layers. A multilayer bandpass filter having a plurality of resonators provided in the body is known. In this multilayer bandpass filter, two adjacent resonators are electromagnetically coupled. Electromagnetic coupling includes inductive coupling and capacitive coupling.

  As shown in Patent Documents 1 to 3, two types of resonators that are not adjacent to each other include a laminated bandpass filter that includes three or more resonators and is configured such that two adjacent resonators are electromagnetically coupled. Some have a bypass coupling capacitor for capacitive coupling. By providing this bypass coupling capacitor, it is possible to form an attenuation pole on the lower frequency side than the pass band in the frequency characteristics of the band pass filter, and thereby the band pass filter on the lower frequency side than the pass band. The attenuation characteristic can be improved.

  Some multilayer bandpass filters include interstage coupling capacitors that capacitively couple two adjacent resonators.

JP 2006-33614 A JP 2006-54508 A JP 2008-166945 A

  In a small wireless communication device including a plurality of communication devices having different use frequency bands, it is required to prevent mutual interference between the plurality of communication devices as the size is reduced. Therefore, the multilayer bandpass filter is particularly required to have a large attenuation in a frequency band 3 to 5 times the passband.

  However, it has been found that the following problems occur in a multilayer bandpass filter including three or more resonators, a bypass coupling capacitor, and an interstage coupling capacitor. Since the conductor layer for constituting the bypass coupling capacitor has a certain size, it has a parasitic inductance. Furthermore, this conductor layer generates a parasitic capacitance between other conductor layers and between different portions of itself. Therefore, this conductor layer forms a parallel resonant circuit with parasitic inductance and parasitic capacitance. This parallel resonant circuit resonates at a frequency called the self-resonant frequency. In the present application, such a parallel resonant circuit including a parasitic inductance and a parasitic capacitance is referred to as a parasitic resonant circuit. In the multilayer bandpass filter, the self-resonant frequency of the parasitic resonance circuit is generally higher than the passband.

  Similar to the conductor layer for configuring the bypass coupling capacitor, the conductor layer for configuring the interstage coupling capacitor may generate a parasitic inductance and a parasitic capacitance, thereby forming a parasitic resonance circuit. is there. The self-resonant frequency of this parasitic resonant circuit is also generally higher than the passband.

  As described above, in a multilayer bandpass filter, when a parasitic resonance circuit is formed by a conductor layer for configuring a bypass coupling capacitor or a conductor layer for configuring an interstage coupling capacitor, Due to the resonance phenomenon, the frequency characteristics on the higher frequency side than the pass band are different from the desired frequency characteristics. As a result, there is a possibility that a desired attenuation amount cannot be obtained in a specific frequency band where a desired attenuation amount is required on the higher frequency side than the pass band.

  Note that, due to the resonance phenomenon of the parasitic resonance circuit, the attenuation amount may be larger than a desired attenuation amount in the specific frequency band. However, in that case, there arises a problem that variation in frequency characteristics between products becomes large.

  Patent Documents 1 and 2 describe a technique for reducing the influence of resonance of the connection electrode itself by providing a layer having a low dielectric constant in the vicinity of the connection electrode, which is a conductor layer for constituting a bypass coupling capacitor. ing. However, Patent Documents 1 and 2 do not describe an interstage coupling capacitor, and naturally reduce the influence of a resonance phenomenon of a parasitic resonance circuit formed by a conductor layer for constituting the interstage coupling capacitor. No means for doing this is described.

  Patent Document 3 discloses a technique for adjusting the frequency of a notch existing on a higher frequency side than the passband by connecting two adjacent resonators by a connection portion including an inductor and a capacitor connected in series. Have been described. In Patent Document 3, three resonator conductor layers are surrounded by a plurality of first dielectric layers having a first dielectric constant, and a plurality of second dielectric constants larger than the first dielectric constant are included. A technique is described in which the connection is surrounded by a second dielectric layer. However, Patent Document 3 describes the influence of the resonance phenomenon of the parasitic resonance circuit formed by the conductor layer for constituting the bypass coupling capacitor and the parasitic resonance formed by the conductor layer for constituting the interstage coupling capacitor. No means for reducing the influence of the resonance phenomenon of the circuit is described.

  The present invention has been made in view of such problems, and its object is to configure the effect of the resonance phenomenon of the parasitic resonance circuit formed by the conductor layer for constituting the bypass coupling capacitor and the interstage coupling capacitor. An object of the present invention is to provide a multilayer bandpass filter that can reduce the influence of the resonance phenomenon of a parasitic resonance circuit formed by a conductor layer.

  The multilayer bandpass filter according to the present invention includes a multilayer body including a plurality of dielectric layers stacked, an input terminal and an output terminal disposed on an outer peripheral portion of the multilayer body, and a first provided in the multilayer body. A resonator, a second resonator, a third resonator, a first interstage coupling capacitor, a second interstage coupling capacitor, and a bypass coupling capacitor are provided. Of the first to third resonators, the first resonator is closest to the input terminal, the third resonator is closest to the output terminal, and the second resonator is the first resonator. And the third resonator. In the present application, the expression “on the circuit configuration” is used to indicate an arrangement on a circuit diagram, not an arrangement in a physical configuration.

  The first interstage coupling capacitor capacitively couples the first resonator and the second resonator. The second interstage coupling capacitor capacitively couples the second resonator and the third resonator. The bypass coupling capacitor capacitively couples the first resonator and the third resonator. The bypass coupling capacitors are arranged at different positions in the stacking direction of the plurality of dielectric layers with respect to the first and second interstage coupling capacitors. The first and second interstage coupling capacitors are configured to include first and second conductor layers arranged at different positions in the stacking direction. The bypass coupling capacitor is configured to include third and fourth conductor layers arranged at different positions in the stacking direction. The plurality of dielectric layers include: a first dielectric layer disposed between the first and second conductor layers; a second dielectric layer disposed between the third and fourth conductor layers; , And a third dielectric layer disposed between the first and second inter-stage coupling capacitors and the bypass coupling capacitor. The dielectric constant of the third dielectric layer is smaller than the dielectric constant of the first and second dielectric layers.

  In the multilayer bandpass filter of the present invention, the first conductor layer includes a first portion for constituting the first interstage coupling capacitor and a second part for constituting the second interstage coupling capacitor. And may be disposed between the first dielectric layer and the third dielectric layer. In this case, the third conductor layer is disposed between the second dielectric layer and the third dielectric layer, and the fourth conductor layer is electrically connected to the first portion of the first conductor layer. A first layer connected and opposed to a part of the third conductor layer; and a first layer electrically connected to the second part of the first conductor layer and opposed to the other part of the third conductor layer. Two layers may be included.

  The first resonator includes a first inductor and a first resonator capacitor, the second resonator includes a second inductor and a second resonator capacitor, and the third resonator includes A third inductor and a third resonator capacitor may be included. The first inductor is constituted by the first portion of the first conductor layer, the second inductor is constituted by the second conductor layer, and the third inductor is the first conductor layer of the first conductor layer. It may be constituted by two parts. In this case, no conductor layer may exist between the first conductor layer and the second conductor layer. The first to third resonator capacitors may be arranged at different positions in the stacking direction with respect to the first to third inductors. The second inductor may have a smaller inductance than the first and third inductors, and the second resonator capacitor may have a larger capacitance than the first and third resonator capacitors.

  In the multilayer bandpass filter configured as described above, the second resonator capacitor may be configured using three or more conductor layers disposed at different positions in the stacking direction. The second resonator may further include a fourth inductor connected in series to the second resonator capacitor. The multilayer bandpass filter further includes a common terminal for electrically connecting the ground terminal disposed on one end surface of the multilayer body in the stacking direction and the first to third inductors to the ground terminal. And a conductive path. The common conductive path may be configured using a through hole, or may be configured using a conductor layer disposed on the outer peripheral portion of the multilayer body.

  In the multilayer bandpass filter of the present invention, the dielectric constant of the third dielectric layer disposed between the first and second interstage coupling capacitors and the bypass coupling capacitor is the first and second The dielectric constant of the first dielectric layer disposed between the first and second conductor layers for constituting the interstage coupling capacitor and the third and fourth conductors for constituting the bypass coupling capacitor Less than the dielectric constant of the second dielectric layer disposed between the layers. As a result, according to the present invention, the parasitic resonance circuit formed by the conductor layer for constituting the bypass coupling capacitor without impairing the functions of the first and second interstage coupling capacitors and the bypass coupling capacitor. It is possible to reduce the influence of the resonance phenomenon and the resonance phenomenon of the parasitic resonance circuit formed by the conductor layer for constituting the interstage coupling capacitor.

It is a perspective view which shows the principal part of the band pass filter which concerns on the 1st Embodiment of this invention. It is a perspective view which shows a part of bandpass filter which concerns on the 1st Embodiment of this invention. It is a perspective view of the band pass filter concerning the 1st Embodiment of the present invention seen from the lower side. It is explanatory drawing which shows the principal part of the band pass filter seen from the A direction in FIG. It is a circuit diagram which shows the circuit structure of the band pass filter which concerns on the 1st Embodiment of this invention. It is explanatory drawing which shows the upper surface of the 1st layer thru | or the 4th dielectric layer of the laminated body of the band pass filter which concerns on the 1st Embodiment of this invention. It is explanatory drawing which shows the upper surface of the 5th thru | or 11th dielectric material layer of the laminated body of the band pass filter which concerns on the 1st Embodiment of this invention. It is explanatory drawing which shows the upper surface of the 12th and 13th dielectric layer of the laminated body of the bandpass filter which concerns on the 1st Embodiment of this invention, and the lower surface of the 13th dielectric layer. It is a characteristic view which shows an example of the frequency characteristic of the 1st and 2nd model in a 1st simulation. It is a characteristic view which shows an example of the frequency characteristic of the 1st and 3rd model in a 1st simulation. It is a characteristic view which shows an example of the frequency characteristic of the band pass filter which concerns on the 1st Embodiment of this invention calculated | required by 2nd simulation, and the band pass filter of a comparative example. It is explanatory drawing which shows the 4th model used by the 3rd simulation. It is explanatory drawing which shows the 5th model used by the 3rd simulation. It is a characteristic view which shows the frequency characteristic of a 4th model. It is a characteristic view which shows the frequency characteristic of a 5th model. It is a perspective view which shows the principal part of the band pass filter which concerns on the 2nd Embodiment of this invention. It is a perspective view of the band pass filter concerning the 2nd Embodiment of this invention seen from the lower side. It is explanatory drawing which shows the upper surface of the 1st layer thru | or the 4th dielectric layer of the laminated body of the band pass filter which concerns on the 2nd Embodiment of this invention. It is explanatory drawing which shows the upper surface of the 5th thru | or 11th dielectric material layer of the laminated body of the band pass filter which concerns on the 2nd Embodiment of this invention. It is explanatory drawing which shows the upper surface of the 12th and 13th dielectric layer of the laminated body of the band pass filter which concerns on the 2nd Embodiment of this invention, and the lower surface of the 13th dielectric layer.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, the circuit configuration of the multilayer bandpass filter according to the first embodiment of the present invention will be described with reference to FIG. A laminated band pass filter (hereinafter simply referred to as a band pass filter) 1 according to the present embodiment includes an input terminal 2, an output terminal 3, a first resonator 4, and a second resonator 5. The third resonator 6, the first interstage coupling capacitor 17, the second interstage coupling capacitor 18, and the bypass coupling capacitor 19 are provided.

  The input terminal 2 is used for signal input. The output terminal 3 is used for signal output. Of the resonators 4, 5 and 6, the resonator 4 is closest to the input terminal 2, the resonator 6 is closest to the output terminal 3, and the resonator 5 is between the resonator 4 and the resonator 6. Is located. In the present embodiment, in particular, the resonator 4 is electrically connected to the input terminal 2, and the resonator 6 is electrically connected to the output terminal 3. Adjacent resonators 4 and 5 are electromagnetically coupled to each other. Adjacent resonators 5 and 6 are also electromagnetically coupled to each other. Electromagnetic coupling includes inductive coupling and capacitive coupling.

  The first resonator 4 includes a first inductor 11 and a first resonator capacitor 14 that are electrically connected to each other. The second resonator 5 includes a second inductor 12 and a second resonator capacitor 15 that are electrically connected to each other. The third resonator 6 includes a third inductor 13 and a third resonator capacitor 16 that are electrically connected to each other. The second resonator 5 further includes a fourth inductor 20 connected in series with the second resonator capacitor 15. Inductors 11 and 12 are inductively coupled to each other. Similarly, the inductors 12 and 13 are inductively coupled to each other. In FIG. 5, the inductive coupling between the inductors 11 and 12 and the inductive coupling between the inductors 12 and 13 are represented by curves with a symbol M attached thereto.

  One end of the inductor 11 and one end of each of the capacitors 14, 17 and 19 are electrically connected to the input terminal 2. The other end of the inductor 11 and the other end of the capacitor 14 are electrically connected to the ground. One end of the inductor 12 and one end of each of the capacitors 15 and 18 are electrically connected to the other end of the capacitor 17. The other end of the inductor 12 is electrically connected to the ground. One end of the inductor 20 is electrically connected to the other end of the capacitor 15. The other end of the inductor 20 is electrically connected to the ground. One end of the inductor 13, one end of the capacitor 16, the other end of the capacitor 19, and the output terminal 3 are electrically connected to the other end of the capacitor 18. The other end of the inductor 13 and the other end of the capacitor 16 are electrically connected to the ground.

  The resonator 5 is inductively coupled to the resonator 4 by inductive coupling of the inductors 11 and 12 and is capacitively coupled to the resonator 4 via the first interstage coupling capacitor 17. The resonator 5 is inductively coupled to the resonator 6 by inductive coupling of the inductors 12 and 13 and is capacitively coupled to the resonator 6 via the second interstage coupling capacitor 18. Further, the two resonators 4 and 6 which are not adjacent to each other are capacitively coupled via the bypass coupling capacitor 19.

  Each of the resonators 4, 5, and 6 is a ¼ wavelength resonator having an open end and a short-circuited end, and the physical lengths of the inductors 11, 12, and 13 are reduced by the resonator capacitors 14, 15, and 16. This is a quarter wavelength resonator using the effect of shortening the wavelength to less than four wavelengths. In the resonator 4, the connection point between the inductor 11 and the capacitor 14 is an open end, and the ground side end of the inductor 11 and the capacitor 14 is a short-circuited end. In the resonator 5, the connection point between the inductor 12 and the capacitor 15 is an open end, and the ground-side end of the inductor 12 and the inductor 20 is a short-circuit end. In the resonator 6, the connection point between the inductor 13 and the capacitor 16 is an open end, and the ground side end of the inductor 13 and the capacitor 16 is a short-circuited end.

  The inductance of the inductor 11 and the capacitance of the capacitor 14 are set so that a desired resonance frequency can be realized in the resonator 4. The inductances of the inductors 12 and 20 and the capacitance of the capacitor 15 are set so that a desired resonance frequency can be realized in the resonator 5. The inductance of the inductor 13 and the capacitance of the capacitor 16 are set so that a desired resonance frequency can be realized in the resonator 6.

  The second inductor 12 has a smaller inductance than the first inductor 11 and the third inductor 13. The second resonator capacitor 15 has a larger capacitance than the first and third resonator capacitors 14 and 16. The inductances of the inductors 11 and 13 may be equal. The capacitances of the capacitors 14 and 16 may be equal. The fourth inductor 20 has an effect of reducing the capacitance of the second resonator capacitor 15 for realizing a desired resonance frequency in the resonator 5 as compared with the case where the fourth inductor 20 is not provided. Note that the resonator 5 may not include the inductor 20. In this case, in the resonator 5, the ground-side ends of the inductor 12 and the capacitor 15 are short-circuited ends.

  As will be described in detail later, the first and second inter-stage coupling capacitors 17 and 18 and the bypass coupling capacitor 19 are each configured to include a plurality of conductor layers. These conductor layers form a parasitic resonance circuit which is a parallel resonance circuit having a parasitic inductance and a parasitic capacitance. In FIG. 5, reference numerals 7 and 8 denote parasitic resonance circuits formed by conductor layers constituting the first and second interstage coupling capacitors 17 and 18, and reference numeral 9 denotes a bypass coupling capacitor 19. 2 shows a parasitic resonance circuit formed by a conductive layer that performs

  In the band pass filter 1 according to the present embodiment, when a signal is input to the input terminal 2, a signal having a frequency within a predetermined pass band is selectively output from the output terminal 3.

  Next, an outline of the structure of the bandpass filter 1 will be described with reference to FIGS. 1 to 4. FIG. 1 is a perspective view showing a main part of the bandpass filter 1. FIG. 2 is a perspective view showing a part of the bandpass filter 1. FIG. 3 is a perspective view of the bandpass filter 1 as viewed from below. FIG. 4 is an explanatory diagram showing the main part of the bandpass filter 1 viewed from the direction A in FIG. The bandpass filter 1 includes a laminate 30 for integrating the components of the bandpass filter 1. As will be described in detail later, the multilayer body 30 includes a plurality of laminated dielectric layers and a plurality of conductor layers. The resonators 4, 5, 6, the interstage coupling capacitors 17, 18 and the bypass coupling capacitor 19 are provided in the multilayer body 30.

  The laminated body 30 has a rectangular parallelepiped shape having an outer peripheral portion. The outer peripheral portion of the stacked body 30 includes an upper surface 30A, a bottom surface 30B, and four side surfaces 30C to 30F. The upper surface 30A and the bottom surface 30B face opposite sides, the side surfaces 30C and 30D also face opposite sides, and the side surfaces 30E and 30F also face opposite sides. The side surfaces 30C to 30F are perpendicular to the top surface 30A and the bottom surface 30B. In the multilayer body 30, the direction perpendicular to the top surface 30A and the bottom surface 30B is the stacking direction of the plurality of dielectric layers and the plurality of conductor layers. 1 and 2, this stacking direction is indicated by an arrow with a symbol T. The top surface 30 </ b> A and the bottom surface 30 </ b> B are end surfaces on both sides in the stacking direction T in the stacked body 30. The bottom surface 30B corresponds to “one end surface in the stacking direction of the stacked body” in the present invention.

  The band pass filter 1 further includes a ground terminal 31 disposed on the bottom surface 30 </ b> B of the multilayer body 30. The input terminal 2 and the output terminal 3 are disposed at a position sandwiching the ground terminal 31 on the bottom surface 30B. An input conductor layer, an output conductor layer, and a ground conductor layer are formed on the top surface of the mounting substrate on which the bandpass filter 1 is mounted. In the band pass filter 1, the input terminal 2 is electrically connected to the input conductor layer, the output terminal 3 is electrically connected to the output conductor layer, and the ground terminal 31 is electrically connected to the ground conductor layer. As shown, the bottom surface 30 </ b> B is mounted on the mounting substrate in a posture facing the upper surface of the mounting substrate. The input conductor layer transmits an input signal input to the input terminal 2. The output conductor layer transmits the output signal output from the output terminal 3. The ground conductor layer is electrically connected to the ground.

  Next, the stacked body 30 will be described in detail with reference to FIGS. 6 to 8. 6A to 6D respectively show the top surfaces of the first to fourth dielectric layers from the top. 7A and 7B show the top surfaces of the fifth and sixth dielectric layers from the top, respectively, and FIG. 7C shows the seventh to tenth dielectric layers from the top. (D) shows the top surface of the eleventh dielectric layer from the top. 8A and 8B show the top surfaces of the twelfth and thirteenth dielectric layers from the top, respectively, and FIG. 8C shows the bottom surface of the thirteenth dielectric layer. .

  No conductor layer is formed on the top surface of the first dielectric layer 41 shown in FIG. A conductor layer 421 is formed on the upper surface of the second dielectric layer 42 shown in FIG. 6B. The conductor layer 421 includes a first portion 421a, a second portion 421b connected to the first portion 421a, and a third portion 421c. The portions 421b and 421c are connected to the portion 421a at the center of the upper surface of the dielectric layer 42. In FIG. 6B, the boundaries of the portions 421a, 421b, and 421c are indicated by broken lines. The first portion 421a extends upward and downward in FIG. 6B from the center of the upper surface of the dielectric layer 42, and has a lower end 421a1. The second portion 421b extends from the center of the top surface of the dielectric layer 42 to the left side in FIG. 6B, and the third portion 421c extends from the center of the top surface of the dielectric layer 42 to the right side in FIG. 6B. It extends. The dielectric layer 42 is formed with a through hole 424 that is electrically connected to the first portion 421a in the vicinity of the lower end 421a1.

  A conductor layer 431 is formed on the top surface of the third dielectric layer 43 shown in FIG. The conductor layer 431 includes a first portion 431a, a second portion 431b connected to the first portion 431a, and a third portion 431c. The parts 431 b and 431 c are connected to the part 431 a at the center of the upper surface of the dielectric layer 43. In FIG. 6C, the boundaries of the portions 431a, 431b, and 431c are indicated by broken lines. The first portion 431a extends upward from the center of the upper surface of the dielectric layer 43 in FIG. 6C and has an upper end 431a1. The second portion 431b extends from the center of the top surface of the dielectric layer 43 to the left side in FIG. 6C, and the third portion 431c extends from the center of the top surface of the dielectric layer 43 to the right side in FIG. It extends.

  The second portion 431b faces the second portion 421b of the conductor layer 421 with the dielectric layer 42 interposed therebetween. The third portion 431 c faces the third portion 421 c of the conductor layer 421 with the dielectric layer 42 interposed therebetween.

  The dielectric layer 43 has three through holes 432, 433, and 434 formed therein. The through holes 432 and 433 are electrically connected to the first portion 431a in the vicinity of the upper end 431a1. The through hole 434 is disposed below the conductor layer 431 in FIG.

  A conductor layer 441 is formed on the upper surface of the fourth dielectric layer 44 shown in FIG. The conductor layer 441 includes a first portion 441a, a second portion 441b and a third portion 441c connected to the first portion 441a. The portions 441 b and 441 c are connected to the portion 441 a at the center of the upper surface of the dielectric layer 44. In FIG. 6D, the boundaries of the portions 441a, 441b, and 441c are indicated by broken lines. The first portion 441a extends downward from the center of the upper surface of the dielectric layer 44 in FIG. 6D, and has a lower end 441a1. The second portion 441b extends from the center of the top surface of the dielectric layer 44 to the left side in FIG. 6D, and the third portion 441c extends from the center of the top surface of the dielectric layer 44 to the right side in FIG. It extends.

  The second portion 441b is opposed to the second portion 431b of the conductor layer 431 with the dielectric layer 43 interposed therebetween. The third portion 441 c faces the third portion 431 c of the conductor layer 431 with the dielectric layer 43 interposed therebetween.

  The dielectric layer 44 has through holes 442, 443, 444 arranged at positions corresponding to the through holes 432, 433, 434 formed in the dielectric layer 43. The through holes 442 and 443 are disposed above the conductor layer 441 in FIG. The through hole 444 is electrically connected to the first portion 441a in the vicinity of the lower end 441a1.

  A conductor layer 451 is formed on the upper surface of the fifth dielectric layer 45 shown in FIG. The conductor layer 451 includes a first portion 451a, a second portion 451b connected to the first portion 451a, and a third portion 451c. The portions 451 b and 451 c are connected to the portion 451 a at the center of the upper surface of the dielectric layer 45. In FIG. 7A, the boundaries of the portions 451a, 451b, and 451c are indicated by broken lines. The first portion 451a extends upward from the center of the upper surface of the dielectric layer 45 in FIG. 7A and has an upper end 451a1. The second portion 451b extends from the center of the top surface of the dielectric layer 45 to the left side in FIG. 7A, and the third portion 451c extends from the center of the top surface of the dielectric layer 45 to the right side in FIG. It extends.

  The second portion 451b is opposed to the second portion 441b of the conductor layer 441 with the dielectric layer 44 interposed therebetween. The third portion 451c is opposed to the third portion 441c of the conductor layer 441 with the dielectric layer 44 interposed therebetween.

  The dielectric layer 45 has through holes 452, 453, and 454 arranged at positions corresponding to the through holes 442, 443, and 444 formed in the dielectric layer 44. The through holes 452 and 453 are electrically connected to the first portion 451a in the vicinity of the upper end 451a1. The through hole 454 is disposed below the conductor layer 451 in FIG.

  A conductor layer 461 is formed on the top surface of the sixth dielectric layer 46 shown in FIG. The conductor layer 461 constitutes the first portion 461a for constituting the first inductor 11 and the first interstage coupling capacitor 17, and the third inductor 13 and the second interstage coupling capacitor 18. And a second portion 461b. The first and second portions 461a and 461b are connected to each other at the center position in the left-right direction above the center in the vertical direction in FIG. In FIG. 7B, the boundary between the first and second portions 461a and 461b is indicated by a broken line. The first portion 461a extends from the boundary so as to rotate counterclockwise. The second portion 461b extends from the boundary so as to rotate in the clockwise direction.

  The second portion 451b of the conductor layer 451 is opposed to a part of the first portion 461a with the dielectric layer 45 interposed therebetween. The third portion 451c of the conductor layer 451 is opposed to a part of the second portion 461b with the dielectric layer 45 interposed therebetween.

  In addition, five through holes 462 to 466 are formed in the dielectric layer 46. The through holes 462 and 463 are electrically connected to the first and second portions 461a and 461b, respectively, in the vicinity of the boundary. The through hole 464 is disposed at a position corresponding to the through hole 454 formed in the dielectric layer 45. The through hole 465 is electrically connected to the first portion 461a in the vicinity of the end of the first portion 461a opposite to the boundary. The through hole 466 is electrically connected to the second portion 461b in the vicinity of the end of the second portion 461b opposite to the boundary.

  Each of the seventh to tenth dielectric layers 47 to 50 shown in FIG. 7C has the following five through holes. That is, the seventh dielectric layer 47 is formed with through holes 472 to 476 arranged at positions corresponding to the through holes 462 to 466 formed in the dielectric layer 46. The eighth dielectric layer 48 has through holes 482 to 486 arranged at positions corresponding to the through holes 472 to 476. The ninth dielectric layer 49 is formed with through holes 492 to 496 arranged at positions corresponding to the through holes 482 to 486. The tenth dielectric layer 50 is formed with through holes 502 to 506 arranged at positions corresponding to the through holes 492 to 496.

  A conductor layer 511 is formed on the top surface of the eleventh dielectric layer 51 shown in FIG. The dielectric layer 51 has through holes 512 to 516 arranged at positions corresponding to the through holes 502 to 506 formed in the dielectric layer 50.

  A conductor layer 521 is formed on the top surface of the twelfth dielectric layer 52 shown in FIG. The conductor layer 521 includes a first layer 521A that faces a part of the conductor layer 511, and a second layer 521B that faces another part of the conductor layer 511. The first layer 521A is disposed on the left side of the center in the left-right direction in FIG. The second layer 521B is disposed on the right side of the center in the left-right direction in FIG.

  Further, five through holes 522 to 526 are formed in the dielectric layer 52. The through holes 522 to 524 are arranged at positions corresponding to the through holes 512 to 514 formed in the dielectric layer 51. The through hole 525 is electrically connected to the first layer 521A in the vicinity of the left end of the first layer 521A in FIG. 8A. The through hole 526 is electrically connected to the second layer 521B in the vicinity of the right end of the second layer 521B in FIG. 8A.

  A ground conductor layer 531 is formed on the top surface of the thirteenth dielectric layer 53 shown in FIG. The dielectric layer 53 has six through holes 532, 533, 535 to 538 formed therein. The through holes 532, 533, 535, and 536 are disposed at positions corresponding to the through holes 522, 523, 525, and 526 formed in the dielectric layer 52. The through holes 532 and 533 are electrically connected to the ground conductor layer 531 in the vicinity of the upper end of the ground conductor layer 531 in FIG. The through holes 537 and 538 are electrically connected to the ground conductor layer 531 in the vicinity of the lower end of the ground conductor layer 531 in FIG. 8B.

  An input terminal 2, an output terminal 3, and a ground terminal 31 are formed on the lower surface of the thirteenth dielectric layer 53 shown in FIG. FIG. 8C shows the dielectric layer 53 and the terminals 2, 3 and 31 as viewed from above. The through holes 532, 533, 537, and 538 are electrically connected to the ground terminal 31. The through hole 535 is electrically connected to the input terminal 2. The through hole 536 is electrically connected to the output terminal 3. The lower surface of the dielectric layer 53 constitutes the bottom surface 30 </ b> B of the stacked body 30.

As the material for the dielectric layer, various materials such as resin, ceramic, or a composite material of both can be used. In particular, the laminate 30 is preferably made of a plurality of dielectric layers made of ceramic by a low-temperature co-firing method because of excellent high-frequency characteristics. In the present embodiment, the dielectric constants of the dielectric layers 46 to 50 are smaller than the dielectric constants of the dielectric layers 45 and 51. The dielectric layers 41 to 44, 52, and 53 preferably have a large dielectric constant, and the dielectric layers 45 and 51 may have the same dielectric constant as that of the dielectric layers 41 to 44, 52, and 53. For example, the relative dielectric constants of the dielectric layers 41 to 45 and 51 to 53 are in the range of 60 to 80, and the relative dielectric constants of the dielectric layers 46 to 50 are in the range of 5 to 11. As an example, the dielectric layers 41 to 45 and 51 to 53 have a relative dielectric constant of 75, and the dielectric layers 46 to 50 have a relative dielectric constant of 7. As a material of the dielectric layers 41 to 45 and 51 to 53, for example, a BaO—Nd ₂ O ₃ —TiO ₂ based ceramic is used. As a material of the dielectric layers 46 to 50, for example, an MgO—SiO ₂ ceramic is used. The dielectric layers 46 to 50 correspond to the “third dielectric layer” in the present invention.

  FIG. 1 shows all the conductor layers in the multilayer body 30. 2 omits the conductor layers 421, 431, 441, and 451 of FIG. The through holes 432, 442, 452, 462, 472, 482, 492, 502, 512, 522, and 532 are connected in series to form the through hole row 62 shown in FIGS. The through holes 433, 443, 453, 463, 473, 483, 493, 503, 513, 523 and 533 are connected in series to form the through hole row 63 shown in FIGS. 1 and 2. The conductor layers 431, 451, 461, 531 and the ground terminal 31 are electrically connected to each other through the through-hole rows 62, 63.

  Of the through-hole rows 62 and 63, a portion from the conductor layer 451 to the ground terminal 31 is a common conductive for electrically connecting the first to third inductors 11, 12, and 13 to the ground terminal 31. Constitutes the road. This common conductive path is configured using a through hole.

  The through holes 424, 434, 444, 454, 464, 474, 484, 494, 504, 514, and 524 are connected in series to form the through hole row 64 shown in FIGS. The conductor layers 421, 441, and 531 are electrically connected to each other through the through-hole row 64. The conductor layer 531 and the ground terminal 31 are electrically connected to each other through through holes 532, 533, 537, and 538.

  The through holes 465, 475, 485, 495, 505, and 515 are connected in series to form the through hole row 65 shown in FIGS. 1 and 2. The first portion 461a of the conductor layer 461 and the first layer 521A are electrically connected to each other through the through-hole row 65. The through holes 525 and 535 are connected in series. The first layer 521A and the input terminal 2 are electrically connected to each other through through holes 525 and 535.

  The through holes 466, 476, 486, 496, 506, and 516 are connected in series to form the through hole row 66 shown in FIGS. The second portion 461b of the conductor layer 461 and the second layer 521B are electrically connected to each other through the through-hole row 66. The through holes 526 and 536 are connected in series. The second layer 521B and the output terminal 3 are electrically connected to each other through through holes 526 and 536.

  The first layer 521A of the conductor layer 521 is opposed to a part of the conductor layer 531 with the dielectric layer 52 interposed therebetween. The first resonator capacitor 14 shown in FIG. 5 includes a first layer 521A, a conductor layer 531 and a dielectric layer 52.

  The second layer 521B of the conductor layer 521 faces the other part of the conductor layer 531 with the dielectric layer 52 interposed therebetween. The third resonator capacitor 16 shown in FIG. 5 includes a second layer 521 </ b> B, a conductor layer 531, and a dielectric layer 52.

  The first layer 521A faces a part of the conductor layer 511 with the dielectric layer 51 interposed therebetween. The second layer 521B faces the other part of the conductor layer 511 with the dielectric layer 51 interposed therebetween. The bypass coupling capacitor 19 shown in FIG. 5 includes a conductor layer 511, a first layer 521A, a second layer 521B, and a dielectric layer 51.

  The conductor layer 511 corresponds to the “third conductor layer” in the present invention. The conductor layer 521 corresponds to the “fourth conductor layer” in the present invention. The dielectric layer 51 corresponds to the “second dielectric layer” in the present invention.

  The second portion 451b of the conductor layer 451 is opposed to a part of the first portion 461a of the conductor layer 461 with the dielectric layer 45 interposed therebetween. The first inter-stage coupling capacitor 17 shown in FIG. 5 includes a second portion 451 b of the conductor layer 451, a first portion 461 a of the conductor layer 461, and the dielectric layer 45.

  The third portion 451c of the conductor layer 451 is opposed to a part of the second portion 461b of the conductor layer 461 with the dielectric layer 45 interposed therebetween. The second inter-stage coupling capacitor 18 shown in FIG. 5 includes a third portion 451 c of the conductor layer 451, a second portion 461 b of the conductor layer 461, and the dielectric layer 45.

  The first inductor 11 is constituted by a first portion 461 a of the conductor layer 461. The second inductor 12 is composed of a conductor layer 451. The third inductor 13 is configured by the second portion 461 b of the conductor layer 461. Since the conductor layer 451 and the first portion 461a of the conductor layer 461 are close to each other, inductive coupling between the inductors 11 and 12 is realized. In addition, since the conductor layer 451 and the second portion 461b of the conductor layer 461 are close to each other, inductive coupling between the inductors 12 and 13 is realized.

  The conductor layer 451 corresponds to the “second conductor layer” in the present invention. The conductor layer 461 corresponds to the “first conductor layer” in the present invention. The dielectric layer 45 corresponds to the “first dielectric layer” in the present invention.

  The second resonator capacitor 15 shown in FIG. 5 is configured using three or more conductor layers disposed at different positions in the stacking direction T. In the present embodiment, in particular, the capacitor 15 is configured using four conductor layers 421, 431, 441, and 451 arranged at different positions in the stacking direction T. More specifically, the capacitor 15 includes the two conductor layers 421, 431, 441, and 451 that are adjacent to each other in any two conductor layers adjacent to each other, and the dielectric layers 42 and 43 between them. , 44.

  The fourth inductor 20 includes a first portion 421a of the conductor layer 421 and a first portion 441a of the conductor layer 441.

  As described above, the bandpass filter 1 according to the present embodiment includes the stacked body 30 including a plurality of stacked dielectric layers and the input terminal disposed on the bottom surface 30B of the outer peripheral portion of the stacked body 30. 2, the output terminal 3 and the ground terminal 31, the first resonator 4, the second resonator 5, the third resonator 6, the first interstage coupling capacitor 17 provided in the multilayer body 30, A second inter-stage coupling capacitor 18 and a bypass coupling capacitor 19 are provided. Of the first to third resonators 4, 5, 6, the first resonator 4 is closest to the input terminal 2, the third resonator 6 is closest to the output terminal 3, and the second The resonator 5 is located between the first resonator 4 and the third resonator 6.

  The first interstage coupling capacitor 17 capacitively couples the first resonator 4 and the second resonator 5. The second interstage coupling capacitor 18 capacitively couples the second resonator 5 and the third resonator 6. The bypass coupling capacitor 19 capacitively couples the first resonator 4 and the third resonator 6. The bypass coupling capacitors 19 are arranged at different positions in the stacking direction T of the plurality of dielectric layers with respect to the first and second interstage coupling capacitors 17 and 18. Specifically, the bypass coupling capacitor 19 is disposed closer to the bottom surface 30B than the first and second interstage coupling capacitors 17 and 18 are. The first and second inter-stage coupling capacitors 17 and 18 are configured to include first and second conductor layers 461 and 451 arranged at different positions in the stacking direction T. The bypass coupling capacitor 19 is configured to include third and fourth conductor layers 511 and 521 arranged at different positions in the stacking direction T.

  As shown in FIG. 7B, a part of the first portion 461 a of the conductor layer 461 that constitutes the first interstage coupling capacitor 17 facing the second portion 451 b of the conductor layer 451. Has a certain size and thus has parasitic inductance and generates parasitic capacitance. Therefore, as shown in FIG. 5, the part of the first portion 461a is a parasitic resonance circuit that is a parallel resonant circuit including the parasitic inductance and the parasitic capacitance on the signal path including the first interstage coupling capacitor 17. A resonance circuit 7 is formed.

  Similarly, a part of the second portion 461b of the conductor layer 461 that constitutes the second interstage coupling capacitor 18 facing the third portion 451c of the conductor layer 451 also has a parasitic inductance and is parasitic. Generate capacity. Therefore, as shown in FIG. 5, the part of the second portion 461b is a parasitic resonance circuit that is a parallel resonant circuit including the parasitic inductance and the parasitic capacitance on the signal path including the second interstage coupling capacitor 18. A resonance circuit 8 is formed.

  Further, as shown in FIG. 7D, since the conductor layer 511 also has a certain size, it has a parasitic inductance and generates a parasitic capacitance. Therefore, as shown in FIG. 5, the conductor layer 511 forms a parasitic resonance circuit 9 which is a parallel resonance circuit using the parasitic inductance and the parasitic capacitance on the signal path including the bypass coupling capacitor 19.

  The parasitic resonance circuits 7, 8, and 9 resonate at the respective self-resonance frequencies. The self-resonant frequency is generally a frequency higher than the passband. As will be described later, unless special measures are taken, the resonance phenomenon of the parasitic resonance circuits 7, 8, 9 may adversely affect the frequency characteristics of the bandpass filter 1.

  In the present embodiment, the plurality of dielectric layers include the first dielectric layer 45 disposed between the first and second conductor layers 461 and 451, and the third and fourth conductor layers 511 and 521. A second dielectric layer 51 disposed between the first and second interstage coupling capacitors 17, 18 and the bypass coupling capacitor 19. 50. The dielectric constants of the third dielectric layers 46 to 50 are smaller than the dielectric constants of the first and second dielectric layers 45 and 51. Thereby, according to this Embodiment, the influence of the resonance phenomenon of the parasitic resonance circuits 7, 8, and 9 can be reduced. This will be described in detail below.

  The band-pass filter 1 according to the present embodiment may be used for a communication device in a small wireless communication device including a plurality of communication devices having different use frequency bands. In such a small wireless communication device, it is required to prevent mutual interference between a plurality of communication devices with downsizing. For this reason, a multilayer bandpass filter used in a communication apparatus in such a small wireless communication device is required to have a large attenuation particularly in a frequency band of 3 to 5 times the passband.

  Increasing the dielectric constant of the multiple dielectric layers that make up the multilayer bandpass filter stack can reduce the size of the inductors and capacitors that are components of the multilayer bandpass filter. For this purpose, it is preferable to increase the dielectric constant of the plurality of dielectric layers. However, when the parasitic resonance circuits 7, 8, 9 are formed as in the band-pass filter 1 according to the present embodiment, the parasitic resonance circuits 7, 8 are increased by increasing the dielectric constant of all the dielectric layers. , 9 approaches the passband, respectively. As a result, the desired attenuation may not be obtained in a specific frequency band on the high frequency side of the pass band where a desired attenuation is required, for example, a frequency band 3 to 5 times the pass band.

  On the other hand, when the dielectric constants of all the dielectric layers are reduced, the first and second conductor layers 461 and 451 that constitute the first and second interstage coupling capacitors 17 and 18 are arranged. The dielectric constant of the dielectric layer 45 and the dielectric constant of the second dielectric layer 51 disposed between the third and fourth conductor layers 511 and 521 constituting the bypass coupling capacitor 19 are also reduced. As a result, a sufficiently large capacitance cannot be obtained in the first and second interstage coupling capacitors 17 and 18 and the bypass coupling capacitor 19, and the first and second interstage coupling capacitors 17 and 18 The function of the bypass coupling capacitor 19 is impaired. In this case, the desired frequency characteristic of the bandpass filter 1 cannot be obtained.

  On the other hand, according to the present embodiment, the dielectric constants of the first and second dielectric layers 45 and 51 are changed between the first and second interstage coupling capacitors 17 and 18 and the bypass coupling capacitor 19. By making the dielectric constant of the third dielectric layers 46 to 50 smaller than the dielectric constants of the first and second dielectric layers 45 and 51 while making the capacitance to obtain a sufficiently large capacitance, The self-resonant frequencies of the parasitic resonance circuits 7, 8, 9 can be moved away from the pass band to the high frequency side without impairing the functions of the first and second interstage coupling capacitors 17, 18 and the bypass coupling capacitor 19. it can. Thereby, according to this Embodiment, it becomes possible to reduce the influence of the resonance phenomenon of the parasitic resonance circuit 7,8,9. The reason why the self-resonant frequencies of the parasitic resonance circuits 7, 8, and 9 can be moved away from the pass band to the high frequency side by reducing the dielectric constant of the third dielectric layers 46 to 50 will be described later. explain in detail.

  In the present embodiment, the third dielectric layers 46 to 50 are disposed between the first and second interstage coupling capacitors 17 and 18 and the bypass coupling capacitor 19. Therefore, by reducing the dielectric constants of the third dielectric layers 46 to 50, the parasitics formed by the first conductor layer 461 for configuring the first and second interstage coupling capacitors 17 and 18 are reduced. Both the influence of the resonance phenomenon of the resonance circuits 7 and 8 and the influence of the resonance phenomenon of the parasitic resonance circuit 9 formed by the third conductor layer 511 for constituting the bypass coupling capacitor 19 can be reduced at the same time. . Therefore, according to the present embodiment, the configuration of the bandpass filter 1 can be simplified, and the bandpass filter 1 can be reduced in size and thickness.

  Further, in the present embodiment, the first conductor layer 461 is used to configure the first portion 461 a for configuring the first interstage coupling capacitor 17 and the second interstage coupling capacitor 18. A second portion 461b and disposed between the first dielectric layer 45 and the third dielectric layers 46-50. The third conductor layer 511 is disposed between the second dielectric layer 51 and the third dielectric layers 46-50. The fourth conductor layer 521 is electrically connected to the first portion 461a of the first conductor layer 461 through the through-hole row 65, and is opposed to a part of the third conductor layer 511. And a second layer 521B that is electrically connected to the second portion 461b of the first conductor layer 461 through the through-hole row 66 and faces the other part of the third conductor layer 511. Yes. With such a configuration, the parasitic resonance circuit 7 can be reduced by a simple method of reducing the dielectric constant of the third dielectric layers 46 to 50 disposed between the first conductor layer 461 and the third conductor layer 511. , 8 and 9 can be reduced.

  In the present embodiment, the first inductor 11 is constituted by the first portion 461 a of the first conductor layer 461. The second inductor 12 is configured by the second conductor layer 451. The third inductor 13 is configured by the second portion 461 b of the first conductor layer 461. There is no conductor layer between the first conductor layer 461 and the second conductor layer 451.

  The first to third resonator capacitors 14, 15, and 16 are arranged at different positions in the stacking direction T with respect to the first to third inductors 11, 12, and 13. Specifically, the capacitors 14 and 16 are disposed closer to the bottom surface 30 </ b> B than the inductors 11, 12, and 13. Further, the capacitor 15 is disposed at a position closer to the upper surface 30 </ b> A with respect to the inductors 11, 12, and 13.

  The second inductor 12 has a smaller inductance than the first inductor 11 and the third inductor 13. The second resonator capacitor 15 has a larger capacitance than the first and third resonator capacitors 14 and 16.

  In the bandpass filter 1 according to the present embodiment, the second inductor 12 has a smaller inductance than the first and third inductors 11 and 13, so that the shape of the second inductor 12 can be reduced. it can. As a result, the band-pass filter 1 can be downsized. If the shapes of the first and third inductors 11 and 13 are reduced, their inductances are reduced, and the input / output impedance of the bandpass filter 1 may be lower than a desired value. Therefore, it is not preferable to reduce the shapes of the first and third inductors 11 and 13. On the other hand, when the inductance of the second inductor 12 is reduced, the bandpass filter 1 can be downsized without making the input / output impedance of the bandpass filter 1 smaller than a desired value.

  By the way, there is a possibility that the resonance frequency of the second resonator 5 cannot be adjusted to a desired frequency only by reducing the inductance of the second inductor 12 as compared with the first and third inductors 11 and 13. . In contrast, in the present embodiment, the second inductor 12 has a smaller inductance than the first and third inductors 11 and 13, and the second resonator capacitor 15 has the first and third capacitors. Since the capacitance is larger than that of the resonator capacitors 14 and 16, the resonance frequency of the second resonator 5 can be adjusted to a desired frequency.

  In the present embodiment, the second resonator capacitor 15 is configured by using three or more conductor layers arranged at different positions in the stacking direction T. Thereby, compared with the case where the capacitor 15 is comprised using two conductor layers, it becomes possible to enlarge the capacitance of the capacitor 15 easily.

  In the present embodiment, the second resonator 5 includes the fourth inductor 20 connected in series to the second resonator capacitor 15, so that the fourth inductor 20 is not provided. The capacitance of the second resonator capacitor 15 for realizing a desired resonance frequency in the resonator 5 can be reduced. This eliminates the need for extremely increasing the capacitance of the second resonator capacitor 15 compared to the first and third resonator capacitors 14 and 16. As a result, the second resonator capacitor 15 can be easily formed.

  In the present embodiment, since the second inductor 12 has a smaller inductance than the first and third inductors 11 and 13, the second inductor 12 and the first inductor 11 are close to each other. Even if the inductor 12 and the third inductor 13 are close to each other, the inductive coupling between the second inductor 12 and the first inductor 11 and the inductive coupling between the second inductor 12 and the third inductor 13 are respectively It can prevent becoming too strong. As a result, the band-pass filter 1 can be downsized.

  In the present embodiment, a conductor layer is provided between the first conductor layer 461 constituting the first and third inductors 11 and 13 and the second conductor layer 451 constituting the second inductor 12. Does not exist. Therefore, the magnetic field generated by the inductors 11, 12 and 13 and contributing to inductive coupling between adjacent resonators is not hindered by the conductor layer. Thereby, it is possible to prevent the Q of each of the first to third resonators 4, 5, and 6 from being lowered.

  From the above, according to the bandpass filter 1 according to the present embodiment, it is possible to reduce the size while preventing the Q of the resonators 4, 5 and 6 from being lowered.

  By the way, in general, in a multilayer bandpass filter, it is necessary to electrically connect an end portion on the ground side of an inductor in each resonator to a ground terminal provided on an outer surface of the multilayer body. There are mainly two methods for electrically connecting the end of the inductor on the ground side to the ground terminal. The first method is a method in which a ground terminal is provided on the side surface of the multilayer body, and a conductor portion for connecting the end portion on the ground side of the inductor to the ground terminal is provided in the multilayer body. The second method is a method in which a ground terminal is provided on the bottom surface of the multilayer body, and a through hole for connecting an end portion on the ground side of the inductor to the ground terminal is provided in the multilayer body. In order to reduce the mounting area of the multilayer bandpass filter, the second method is more advantageous. However, particularly in a multilayer bandpass filter having three or more resonators, the number of through holes increases when the second method is used, and the number of steps for manufacturing the multilayer bandpass filter increases. And the problem of reducing the quality such as cracks in the laminate.

  In contrast, the band-pass filter 1 according to the present embodiment has a common conductive path (through-hole array) for electrically connecting the first to third inductors 11, 12, and 13 to the ground terminal 31. 62, 63). This common conductive path includes a through hole. According to the present embodiment, the number of through-holes can be reduced as compared with the case where three through-hole rows for connecting the ground-side ends of the three inductors to the ground terminal are provided. As a result, according to the present embodiment, the number of steps for manufacturing the bandpass filter 1 is increased, and the quality of the bandpass filter 1 is deteriorated such that a crack is generated in the laminate 30. It becomes possible to prevent.

  Hereinafter, referring to simulation results, it is possible to reduce the influence of the resonance phenomenon of the parasitic resonance circuits 7, 8, 9 by reducing the dielectric constant of the third dielectric layers 46 to 50 in detail. explain. First, the result of the first simulation for examining the influence of the parasitic resonance circuits 7, 8, and 9 will be described. In the first simulation, the frequency characteristics, particularly the pass attenuation characteristics, of the first to third models designed so that the passband is approximately 2.4 to 2.5 GHz are obtained. The frequency band of 2.4 to 2.5 GHz corresponds to one frequency band used in the wireless LAN. The first model is a model obtained by removing the parasitic resonance circuits 7, 8, and 9 from the circuit shown in FIG. The second model is a model obtained by removing the parasitic resonance circuits 7 and 8 from the circuit shown in FIG. 5, and is a model for examining the influence of the parasitic resonance circuit 9 by comparing with the first model. The third model is a model obtained by removing the parasitic resonance circuit 9 from the circuit shown in FIG. 5, and is a model for examining the influence of the parasitic resonance circuits 7 and 8 by comparing with the first model.

  FIG. 9 shows an example of frequency characteristics of the first and second models in the first simulation. FIG. 10 shows an example of frequency characteristics of the first and third models in the first simulation. 9 and 10, the horizontal axis represents frequency and the vertical axis represents attenuation. In FIG. 9, the solid curve indicates the pass attenuation characteristic of the first model, and the broken curve indicates the pass attenuation characteristic of the second model. In FIG. 10, the solid curve indicates the pass attenuation characteristic of the first model, and the broken curve indicates the pass attenuation characteristic of the third model.

  As shown in FIG. 9, in the pass attenuation characteristic of the second model, the attenuation varies greatly in the frequency band higher than the pass band. This variation is caused by the resonance phenomenon of the parasitic resonance circuit 9. The self-resonant frequency of the parasitic resonance circuit 9 is equal to or near the frequency at which the curve indicating the pass attenuation characteristic of the second model intersects the curve indicating the pass attenuation characteristic of the first model in the region where the fluctuation occurs. Is the frequency. The self-resonant frequency of the parasitic resonance circuit 9 approaches the pass band as the impedance of the parasitic resonance circuit 9 increases.

  As shown in FIG. 10, the pass attenuation characteristic of the third model has a peak in which the attenuation is extremely small in a frequency band higher than the pass band. This peak is caused by the resonance phenomenon of the parasitic resonance circuits 7 and 8. The peak frequency is the self-resonance frequency of the parasitic resonance circuits 7 and 8. The self-resonant frequencies of the parasitic resonance circuits 7 and 8 approach the pass band as the impedance of the parasitic resonance circuits 7 and 8 increases.

  In the actual bandpass filter, when both the parasitic resonance circuits 7 and 8 and the parasitic resonance circuit 9 are formed, the frequency characteristics on the higher frequency side than the passband in the bandpass filter are the same as those of the second and third models. Fluctuates more complicated than frequency characteristics. This is because the fluctuation caused by the resonance phenomenon of the parasitic resonance circuits 7 and 8 and the fluctuation caused by the parasitic resonance circuit 9 are combined. Therefore, when the parasitic resonance circuits 7, 8, and 9 are formed, the frequency characteristics on the higher frequency side than the pass band are different from the desired frequency characteristics. As a result, there is a possibility that a desired attenuation amount cannot be obtained in a specific frequency band where a desired attenuation amount is required on the higher frequency side than the pass band. Note that, due to the resonance phenomenon of the parasitic resonance circuits 7, 8, and 9, the attenuation amount may be larger than a desired attenuation amount in the specific frequency band. However, in that case, there arises a problem that variation in frequency characteristics between products becomes large.

  Next, the result of the second simulation for obtaining the characteristics of the bandpass filter 1 according to the present embodiment and the bandpass filter of the comparative example will be described. The configuration of the band pass filter of the comparative example is the same as the configuration of the band pass filter 1 according to the present embodiment except for the dielectric constants of the dielectric layers 41 to 53. In the second simulation, the relative permittivity of the dielectric layers 41 to 45 and 51 to 53 in the bandpass filter 1 according to the present embodiment is set to 75, and the relative permittivity of the dielectric layers 46 to 50 is set to 7. The relative dielectric constant of all the dielectric layers 41 to 53 in the band-pass filter of the comparative example was set to 75.

  In the second simulation, the bandpass filter 1 according to the present embodiment and the bandpass filter of the comparative example are designed so that the passband is approximately 2.4 to 2.5 GHz, and each frequency characteristic, particularly the passband is designed. The attenuation characteristics were obtained. FIG. 11 shows an example of frequency characteristics of the band-pass filter 1 according to the present embodiment and the band-pass filter of the comparative example obtained by the second simulation. In FIG. 11, the horizontal axis represents frequency and the vertical axis represents attenuation. In FIG. 11, the solid curve indicates the pass attenuation characteristic of the bandpass filter 1 according to the present embodiment, and the broken curve indicates the pass attenuation characteristic of the bandpass filter of the comparative example.

  As shown in FIG. 11, in the band-pass filter of the comparative example, the frequency characteristic (pass attenuation characteristic) on the higher frequency side than the pass band is large and complicatedly varied. This is because the fluctuation caused by the resonance phenomenon of the parasitic resonance circuits 7 and 8 and the fluctuation caused by the parasitic resonance circuit 9 are combined as described above. Therefore, in the bandpass filter of the comparative example, a desired attenuation amount is obtained in a specific frequency band on the high frequency side of the pass band where a desired attenuation amount is required, for example, a frequency band 3 to 5 times the pass band. It becomes impossible.

  On the other hand, in the band pass filter 1 according to the present embodiment, the variation in frequency characteristics (pass attenuation characteristics) in a band of 3 to 5 times the frequency of the pass band is smaller than in the band pass filter of the comparative example. ing. As a result, a desired attenuation can be stably obtained in a frequency band of 3 to 5 times the pass band. As described above, according to the present embodiment, the dielectric constants of the third dielectric layers 46 to 50 are made smaller than the dielectric constants of the first and second dielectric layers 45 and 51, thereby causing parasitic resonance. The influence of the resonance phenomenon of the circuits 7, 8, and 9 can be reduced.

  Next, referring to the result of the third simulation, by reducing the dielectric constant of the third dielectric layers 46 to 50, the self-resonance frequencies of the parasitic resonance circuits 7, 8, and 9 are increased from the passband to the high frequency. We will explain in detail why we can move away. In the third simulation, the parasitic resonance circuits 7, 8, and 9 are regarded as microstrip lines, respectively, and the relationship between the dielectric constant around the transmission line in this microstrip line and the resonance frequency is examined.

  First, the fourth and fifth models used in the third simulation will be described with reference to FIGS. 12 and 13. The fourth and fifth models are both 1/4 wavelength microstrip line models. FIG. 12 is an explanatory diagram showing the fourth model. 12A is a perspective view of the fourth model, and FIG. 12B is a side view of the fourth model. The fourth model includes a transmission line 73, a dielectric layer 71 surrounding the transmission line 73, and a ground conductor plate 74 disposed on the bottom surface of the dielectric layer 71. The dielectric layer 71 has an upper portion 71A and a lower portion 71B. The transmission line 73 is disposed between the upper portion 71A and the lower portion 71B. The left end of the transmission line 73 in FIG. 12B is grounded, and the right end of the transmission line 73 in FIG. 12B is an open end. The relative dielectric constant of the dielectric layer 71 is 75.

  FIG. 13 is an explanatory diagram showing the fifth model. 13A is a perspective view of the fifth model, and FIG. 13B is a side view of the fifth model. The fifth model includes a transmission line 83, dielectric layers 81 and 82 surrounding the transmission line 83, and a ground conductor plate 84 disposed on the bottom surface of the dielectric layer 82. The dielectric layer 81 is disposed on the dielectric layer 82. The transmission line 83 is disposed between the dielectric layers 81 and 82. The left end of the transmission line 83 in FIG. 13B is grounded, and the right end of the transmission line 83 in FIG. 13B is an open end. The relative dielectric constant of the dielectric layer 81 is 7, and the relative dielectric constant of the dielectric layer 82 is 75. The transmission lines 73 and 83 have a length L of 3700 μm and a width W of 300 μm.

  In the third simulation, high-frequency signals were supplied to the transmission lines 73 and 83 from the vicinity of the respective open ends, and the frequency characteristics of the fourth and fifth models were obtained. FIG. 14 is a characteristic diagram showing frequency characteristics of the fourth model. FIG. 15 is a characteristic diagram showing frequency characteristics of the fifth model. 14 and 15, the horizontal axis represents frequency, and the vertical axis represents attenuation. Both the fourth and fifth models resonate at a predetermined resonance frequency. The resonance frequency of the fourth model was 2.28 GHz, and the resonance frequency of the fifth model was 2.81 GHz. As understood from this result, a part of the periphery of the transmission line 83 (dielectric material) as in the fifth model is compared with the case where the dielectric constant of the entire periphery of the transmission line 73 is large as in the fourth model. By reducing the dielectric constant of the layer 81), the resonance frequency is increased.

  The result of the third simulation can be explained as follows. First, the length of one wavelength of an electromagnetic wave having a predetermined frequency in the dielectric varies depending on the dielectric constant of the dielectric, and increases as the dielectric constant decreases. Next, if the length of the transmission line existing in the dielectric is considered to be constant, the length of one wavelength of the electromagnetic wave having the same frequency increases as the dielectric constant of the dielectric decreases. On the contrary, the length of one wavelength corresponding to the length becomes smaller, and the frequency corresponding to one wavelength corresponding to the length of the transmission line becomes higher. Therefore, when the transmission line has a resonance frequency, the resonance frequency increases as the dielectric constant of the dielectric decreases.

  The above description also applies to the relationship between the dielectric constant of the dielectric around the parasitic resonance circuits 7, 8, 9 and the self-resonance frequency of the parasitic resonance circuits 7, 8, 9. That is, as the dielectric constant of the dielectric around the parasitic resonance circuits 7, 8, 9 decreases, the self-resonance frequency of the parasitic resonance circuits 7, 8, 9 increases. If the dielectric constant of the entire periphery of the parasitic resonance circuits 7, 8, and 9 is reduced, the self-resonance frequency of the parasitic resonance circuits 7, 8, and 9 can be increased. However, as described above, The functions of the second interstage coupling capacitors 17 and 18 and the bypass coupling capacitor 19 are impaired. Therefore, in the present embodiment, only the dielectric constant of the third dielectric layers 46 to 50 existing between the first and second interstage coupling capacitors 17 and 18 and the bypass coupling capacitor 19 is reduced. Thus, the self-resonance frequency of the parasitic resonance circuits 7, 8, and 9 is increased without impairing the functions of the first and second inter-stage coupling capacitors 17 and 18 and the bypass coupling capacitor 19, thereby increasing the frequency from the passband. Keep away from the side. As a result, according to the present embodiment, as shown in FIG. 11, it is possible to reduce the fluctuation of the frequency characteristic (pass attenuation characteristic) in the frequency band of 3 to 5 times the pass band.

[Second Embodiment]
Next, a band pass filter according to a second embodiment of the present invention will be described. The circuit configuration of the band-pass filter 101 according to the present embodiment is the same as that of the first embodiment, as shown in FIG.

  FIG. 16 is a perspective view showing the main part of the bandpass filter 101. FIG. 17 is a perspective view of the bandpass filter 101 as viewed from below. The band pass filter 101 includes a multilayer body 30. Similar to the first embodiment, the stacked body 30 has a rectangular parallelepiped shape having an outer peripheral portion. The outer peripheral portion of the stacked body 30 includes an upper surface 30A, a bottom surface 30B, and four side surfaces 30C to 30F. As shown in FIG. 17, in the present embodiment, the ground terminal 31 is formed from the position of the ridgeline between the bottom surface 30B and the side surface 30C to the position of the ridgeline between the bottom surface 30B and the side surface 30D. .

  The band-pass filter 101 includes conductor layers 32 and 33 disposed on the side surfaces 30C and 30D in the outer peripheral portion of the multilayer body 30. The conductor layer 32 is formed from the position of the ridge line between the upper surface 30A and the side surface 30C to the position near the ridge line between the bottom surface 30B and the side surface 30C. The conductor layer 33 is formed from the position of the ridgeline between the upper surface 30A and the side surface 30D to the position near the ridgeline between the bottom surface 30B and the side surface 30D. The conductor layers 32 and 33 are electrically connected to the ground terminal 31.

  Next, with reference to FIG. 18 thru | or FIG. 20, the point from which the laminated body 30 in this Embodiment differs from the laminated body 30 in 1st Embodiment is demonstrated. 18A to 18D respectively show the top surfaces of the first to fourth dielectric layers from the top. 19A and 19B respectively show the top surfaces of the fifth and sixth dielectric layers from the top, and FIG. 19C shows the seventh to tenth dielectric layers from the top. (D) shows the top surface of the eleventh dielectric layer from the top. 20A and 20B show the top surfaces of the twelfth and thirteenth dielectric layers from the top, respectively, and FIG. 20C shows the bottom surface of the thirteenth dielectric layer. .

  As shown in FIG. 18B, the lower end 421a1 of the first portion 421a of the conductor layer 421 formed on the upper surface of the second dielectric layer 42 is the upper surface of the dielectric layer 42 shown in FIG. ) Is located at the lower end. Further, the through hole 424 is not provided in the dielectric layer 42.

  As shown in FIG. 18C, the upper end 431a1 of the first portion 431a of the conductor layer 431 formed on the upper surface of the third dielectric layer 43 corresponds to the upper surface of the dielectric layer 43 shown in FIG. ). Further, the through holes 432, 433, and 434 are not provided in the dielectric layer 43.

  As shown in FIG. 18D, the lower end 441a1 of the first portion 441a of the conductor layer 441 formed on the upper surface of the fourth dielectric layer 44 is the upper surface of the dielectric layer 44 shown in FIG. ) Is located at the lower end. Further, the through holes 442, 443, 444 are not provided in the dielectric layer 44.

  As shown in FIG. 19A, the upper end 451a1 of the first portion 451a of the conductor layer 451 formed on the upper surface of the fifth dielectric layer 45 is the upper surface of the dielectric layer 45 shown in FIG. ). The through holes 452, 453, and 454 are not provided in the dielectric layer 45.

  As shown in FIG. 19B, a part of each of the first and second portions 461a and 461b of the conductor layer 461 formed on the upper surface of the sixth dielectric layer 46 is the dielectric layer 46. Is extended to the upper end in FIG. 19 (b). The dielectric layer 46 is not provided with through holes 462, 463, 464.

  As shown in FIG. 19 (c), the through holes 472, 473, 474 are not provided in the seventh dielectric layer 47. Further, the through holes 482, 483, and 484 are not provided in the eighth dielectric layer 48. Further, the ninth dielectric layer 49 is not provided with through holes 492, 493, and 494. Further, the through holes 502, 503, and 504 are not provided in the tenth dielectric layer 50.

  As shown in FIG. 19 (d), the through holes 512, 513, and 514 are not provided in the eleventh dielectric layer 51. Further, as shown in FIG. 20A, the through holes 522, 523, and 524 are not provided in the twelfth dielectric layer 52.

  As shown in FIG. 20B, the ground conductor layer 531 formed on the top surface of the thirteenth dielectric layer 53 is formed on the top surface of the dielectric layer 53 from the upper end in FIG. Extends to the lower edge. Further, the through holes 532, 533, 537, and 538 are not provided in the dielectric layer 53.

  As shown in FIG. 20C, the ground terminal 31 formed on the lower surface of the thirteenth dielectric layer 53 is located on the lower surface of the dielectric layer 53 from the upper end in FIG. It extends to the end of the.

  The first portion 421a of the conductor layer 421, the first portion 441a of the conductor layer 441, the conductor layer 531 and the ground terminal 31 are electrically connected to the conductor layer 32. Further, the first portion 431a of the conductor layer 431, the first portion 451a of the conductor layer 451, the first and second portions 461a and 461b of the conductor layer 461, the conductor layer 531 and the ground terminal 31 are connected to the conductor layer 33. Electrically connected. The conductor layers 32 and 33 are formed on the side surfaces 30C and 30D of the multilayer body 30 after the multilayer body 30 is manufactured.

  In the present embodiment, the through hole rows 62, 63, 64 and the through holes 537, 538 in the first embodiment are not provided. The conductor layer 32 constitutes a conductive path serving as a substitute for the through hole row 64 and the through holes 537 and 538. The conductor layer 33 constitutes a conductive path serving as a substitute for the through-hole rows 62 and 63. Of the conductor layer 33, the portion from the conductor layer 461 to the ground terminal 31 constitutes a common conductive path for electrically connecting the first to third inductors 11, 12, and 13 to the ground terminal 31. doing. Thus, in the present embodiment, the common conductive path is configured using the conductor layer 33 arranged on the outer peripheral portion of the multilayer body 30.

  According to the present embodiment, since the number of through holes is reduced as compared with the first embodiment, it is possible to further prevent the quality of the band pass filter 101 from being deteriorated due to the through holes. . Other configurations, operations, and effects in the present embodiment are the same as those in the first embodiment.

  In addition, this invention is not limited to said each embodiment, A various change is possible. For example, in each embodiment, the third dielectric layer having a dielectric constant smaller than that of the first and second dielectric layers is located between the first conductor layer 461 and the third conductor layer 511. In other words, the first conductor layer 461 and the third conductor layer 511 are not necessarily in contact with each other. For example, the dielectric constant of at least one of the dielectric layer 46 and the dielectric layer 50 may be the same as that of the dielectric layers 45 and 51.

  Further, in each embodiment, the first and third inductors 11 and 13 are configured by the first conductor layer 461 for configuring the first and second interstage coupling capacitors 17 and 18. . However, the first conductor layer and the conductor layers constituting the first and third inductors 11 and 13 may be conductor layers different from each other.

  The bandpass filter of the present invention may include four or more resonators. In this case, there are a plurality of second resonators.

  DESCRIPTION OF SYMBOLS 1 ... Multilayer type band pass filter, 2 ... Input terminal, 3 ... Output terminal, 4, 5, 6 ... Resonator, 7, 8, 9 ... Parasitic resonance circuit, 11-13, 20 ... Inductor, 14-16 ... Resonance Capacitors for capacitors, 17, 18... Interstage coupling capacitors, 19... Capacitors for bypass coupling, 30.

Claims (9)

A laminate including a plurality of laminated dielectric layers;
An input terminal and an output terminal arranged on the outer periphery of the laminate;
A first resonator, a second resonator, a third resonator, a first inter-stage coupling capacitor, a second inter-stage coupling capacitor, and a bypass coupling capacitor provided in the multilayer body, respectively. A laminated bandpass filter comprising:
Of the first to third resonators, the first resonator is closest to the input terminal, the third resonator is closest to the output terminal, and the second resonator. Is located between the first and third resonators;
The first interstage coupling capacitor capacitively couples the first resonator and the second resonator,
The second interstage coupling capacitor capacitively couples the second resonator and the third resonator,
The bypass coupling capacitor capacitively couples the first resonator and the third resonator,
The bypass coupling capacitors are arranged at different positions in the stacking direction of the plurality of dielectric layers with respect to the first and second interstage coupling capacitors,
The first and second interstage coupling capacitors are configured to include first and second conductor layers arranged at different positions in the stacking direction,
The bypass coupling capacitor is configured to include third and fourth conductor layers arranged at different positions in the stacking direction,
The plurality of dielectric layers include a first dielectric layer disposed between the first and second conductor layers, and a second dielectric layer disposed between the third and fourth conductor layers. A body layer; and a third dielectric layer disposed between the first and second inter-stage coupling capacitors and the bypass coupling capacitor;
A multilayer bandpass filter, wherein a dielectric constant of the third dielectric layer is smaller than a dielectric constant of the first and second dielectric layers.   The first conductor layer includes a first portion for constituting the first inter-stage coupling capacitor and a second portion for constituting the second inter-stage coupling capacitor, The multilayer bandpass filter according to claim 1, wherein the multilayer bandpass filter is disposed between the first dielectric layer and the third dielectric layer. The third conductor layer is disposed between the second dielectric layer and the third dielectric layer;
The fourth conductor layer includes a first layer electrically connected to a first portion of the first conductor layer and facing a part of the third conductor layer, and a first layer of the first conductor layer. The multilayer bandpass filter according to claim 2, further comprising: a second layer electrically connected to the second portion and facing the other part of the third conductor layer. The first resonator includes a first inductor and a first resonator capacitor;
The second resonator includes a second inductor and a second resonator capacitor,
The third resonator includes a third inductor and a third resonator capacitor,
The first inductor is constituted by the first portion of the first conductor layer;
The second inductor is constituted by the second conductor layer;
The third inductor is constituted by the second portion of the first conductor layer;
There is no conductor layer between the first conductor layer and the second conductor layer,
The first to third resonator capacitors are arranged at different positions in the stacking direction with respect to the first to third inductors,
The second inductor has a smaller inductance than the first and third inductors,
4. The multilayer bandpass filter according to claim 2, wherein the second resonator capacitor has a capacitance larger than that of the first and third resonator capacitors.   5. The multilayer bandpass filter according to claim 4, wherein the second resonator capacitor is configured by using three or more conductor layers arranged at different positions in the stacking direction.   6. The multilayer bandpass filter according to claim 4, wherein the second resonator further includes a fourth inductor connected in series with the second resonator capacitor.   And a ground terminal disposed on one end face in the stacking direction of the stacked body, and a common conductive path for electrically connecting the first to third inductors to the ground terminal. The multilayer bandpass filter according to any one of claims 4 to 6.   8. The multilayer bandpass filter according to claim 7, wherein the common conductive path is configured using a through hole.   The multilayer bandpass filter according to claim 7, wherein the common conductive path is configured by using a conductor layer disposed on an outer peripheral portion of the multilayer body.

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