Band-pass filter

Abstract

To form a steep attenuation pole while satisfying the balance characteristics in a balanced band-pass filter.SOLUTION: A band-pass filter 1 includes an unbalanced port 11, a first balanced port 12, a second equilibrium port 13, and a first resonator 21, a second resonator 22, and a third resonator 23 provided between the unbalanced port 11 and the first and second balanced ports 12 and 13. The second resonator 22 and the third resonator 23 are both open-ended resonators, and are adjacent to each other in the circuit configuration and are electromagnetically coupled with magnetic coupling as the main coupling. The first resonator 21 is provided at a position closer to the second resonator 22 than the third resonator 23, and jumps and is coupled with the third resonator 23 in terms of circuit configuration.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a balanced bandpass filter having one unbalanced port and a pair of balanced ports.

Background Art

[0002] As one of the electronic components that can be used in the transmission and reception circuits of wireless communication devices such as mobile phones and wireless LAN communication devices, there is a bandpass filter including a plurality of resonators. The bandpass filter preferably has attenuation poles at which the insertion loss changes steeply in each of a first vicinity region that is a frequency region lower than the passband and closer to the passband and a second vicinity region that is a frequency region higher than the passband and closer to the passband.

[0003] Also, as a bandpass filter, a balanced bandpass filter having a pair of balanced ports as output ports is known. For this balanced bandpass filter, good amplitude balance characteristics and phase balance characteristics are required. Good amplitude balance characteristics mean that the difference in amplitude between the two balanced element signals constituting the balanced signal output from the bandpass filter is close to 0. Good phase balance characteristics mean that the phase difference between the two balanced element signals is close to 180 degrees.

[0004] Patent Document 1 discloses a balanced LC filter having a pair of balanced input terminals and a pair of balanced output terminals. In this balanced LC filter, attenuation poles are provided on the lower frequency side or the higher frequency side than the center frequency of the balanced LC filter by pole adjustment capacitors.

[0005] Patent Document 2 discloses a lumped constant type bandpass filter having a pair of balanced terminals and one unbalanced terminal. Patent Document 2 describes that an unbalanced input - balanced output type filter is configured by using the unbalanced terminal as an input terminal and a pair of balanced terminals as output terminals.

Prior Art Documents

Patent Document

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] Currently, mobile communication systems up to the fourth generation have been put into practical use. Also, currently, the standardization of the fifth-generation mobile communication system is underway. In the conventional balanced band-pass filter, in these mobile communication systems, it has been difficult to form sharp attenuation poles in each of the first and second adjacent regions while satisfying the balance characteristics.

[0008] The present invention has been made in view of such problems, and an object thereof is to provide a balanced band-pass filter having one unbalanced port and a pair of balanced ports, which can form sharp attenuation poles while satisfying the balance characteristics.

Means for Solving the Problems

[0009] The band-pass filter of the present invention includes an unbalanced port, a first balanced port, a second balanced port, and a first resonator, a second resonator, and a third resonator provided between the unbalanced port and the first and second balanced ports in terms of circuit configuration. Both the second resonator and the third resonator are open-ended resonators at both ends, and are adjacent to each other in terms of circuit configuration and are electromagnetically coupled with magnetic coupling as the main coupling. The first resonator is provided at a position closer to the second resonator than the third resonator in terms of circuit configuration, and is capacitively coupled to the third resonator.

[0010] In the bandpass filter of the present invention, the first resonator is a single-ended short-circuited resonator and may be provided between the unbalanced port and the second resonator in terms of circuit configuration.

[0011] Also, in the bandpass filter of the present invention, the distance between the second resonator and the third resonator may be smaller than the distance between the first resonator and the second resonator.

[0012] Further, the bandpass filter of the present invention may further include a fourth resonator provided between the unbalanced port and the first and second balanced ports in terms of circuit configuration. In this case, the fourth resonator is provided closer to the third resonator than the second resonator in terms of circuit configuration and may be capacitively coupled to the second resonator. Also, in this case, the first resonator is a single-ended short-circuited resonator and may be provided between the unbalanced port and the second resonator in terms of circuit configuration. Also, the fourth resonator is an open-ended resonator and may be provided between the first and second balanced ports and the third resonator in terms of circuit configuration.

[0013] When the bandpass filter of the present invention includes the fourth resonator, the distance between the second resonator and the third resonator may be smaller than the distance between the first resonator and the second resonator and smaller than the distance between the third resonator and the fourth resonator.

[0014] In addition, the band-pass filter of the present invention may further include a laminate for integrating at least the second and third resonators, the laminate including a plurality of stacked dielectric layers, a plurality of conductor layers, and a plurality of through-holes. In this case, the plurality of conductor layers may include a plurality of conductor layers for resonators. The plurality of through-holes may include a plurality of through-holes for resonators. Further, each of the second and third resonators may include a first through-hole row, a second through-hole row, and a conductor layer portion. Each of the first and second through-hole rows is configured by connecting two or more through-holes among the plurality of through-holes for resonators in series, and may penetrate two or more dielectric layers among the plurality of dielectric layers. The conductor layer portion is configured by one or more conductor layers for resonators among the plurality of conductor layers for resonators, and may connect one end of the first through-hole row and one end of the second through-hole row.

Effects of the Invention

[0015] The band-pass filter of the present invention includes first to third resonators. The second resonator and the third resonator are adjacent to each other in terms of circuit configuration and are electromagnetically coupled with magnetic coupling as the main coupling. The first resonator is provided at a position closer to the second resonator than the third resonator in terms of circuit configuration, and is capacitively coupled to the third resonator. Thereby, according to the present invention, it is possible to realize a band-pass filter that can form a sharp attenuation pole while satisfying balance characteristics.

Brief Description of the Drawings

[0016]

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Embodiments for Carrying Out the Invention

[0017] [First Embodiment] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, referring to FIG. 1, the circuit configuration of the bandpass filter according to the first embodiment of the present invention will be described. FIG. 1 shows the circuit configuration of the bandpass filter according to the present embodiment. As shown in FIG. 1, the bandpass filter 1 includes an unbalanced port 11, a first balanced port 12, a second balanced port 13, a first resonator 21, a second resonator 22, a third resonator 23, and a fourth resonator 24.

[0018] The first to fourth resonators 21 to 24 are provided between the unbalanced port 11 and the first and second balanced ports 12 and 13 in terms of circuit configuration. The second resonator 22 and the third resonator 23 are adjacent to each other in terms of circuit configuration. The first resonator 21 is provided at a position closer to the second resonator 22 than to the third resonator 23 in terms of circuit configuration. The fourth resonator 24 is provided at a position closer to the third resonator 23 than to the second resonator 22 in terms of circuit configuration. In the present application, the expression "in terms of circuit configuration" is used to refer to the arrangement on the circuit diagram rather than the arrangement in the physical configuration.

[0019] In particular, in the present embodiment, the first to fourth resonators 21 to 24 are provided in this order from the unbalanced port 11 side. That is, the second resonator 22 is provided at a position closer to the unbalanced port 11 than to the third resonator 23 in terms of circuit configuration. The first resonator 21 is provided between the unbalanced port 11 and the second resonator 22 in terms of circuit configuration. The fourth resonator 24 is provided between the first and second balanced ports 12 and 13 and the third resonator 23 in terms of circuit configuration.

[0020] The first resonator 21 is a single-ended short-circuited resonator. The band-pass filter 1 further includes capacitors C1 and C11. The capacitor C1 connects one end of the first resonator 21 to the ground. The capacitor C11 connects the one end of the first resonator 21 to the unbalanced port 11. The other end of the first resonator 21 is connected to the ground.

[0021] The second to fourth resonators 22 to 24 are all open-ended resonators. The bandpass filter 1 further includes capacitors C2A, C2B, C3A, C3B, C4A, and C4B. The capacitor C2A connects one end of the second resonator 22 to the ground. The capacitor C2B connects the other end of the second resonator 22 to the ground. The capacitor C3A connects one end of the third resonator 23 to the ground. The capacitor C3B connects the other end of the third resonator 23 to the ground. The capacitor C4A connects one end of the fourth resonator 24 to the ground. The capacitor C4B connects the other end of the fourth resonator 24 to the ground.

[0022] The bandpass filter 1 further includes capacitors C12, C23A, C23B, C34A, and C34B. The capacitor C12 connects the one end of the first resonator 21 to the one end of the second resonator 22. The capacitor C23A connects the one end of the second resonator 22 to the one end of the third resonator 23. The capacitor C23B connects the other end of the second resonator 22 to the other end of the third resonator 23. The capacitor C34A connects the one end of the third resonator 23 to the one end of the fourth resonator 24. The capacitor C34B connects the other end of the third resonator 23 to the other end of the fourth resonator 24.

[0023] The first balanced port 12 is connected to the one end of the fourth resonator 24. The second balanced port 13 is connected to the other end of the fourth resonator 24.

[0024] The second resonator 22 and the third resonator 23 are magnetically coupled and capacitively coupled via the capacitors C23A and C23B. In FIG. 1, the curve marked with the symbol M shows the magnetic coupling between the second resonator 22 and the third resonator 23. Here, among the magnetic coupling and the capacitive coupling that contribute to the electromagnetic coupling between two resonators, the relatively stronger coupling is referred to as the main coupling, and the other coupling is referred to as the sub-coupling. In particular, in this embodiment, the second resonator 22 and the third resonator 23 are electromagnetically coupled with the magnetic coupling as the main coupling and the capacitive coupling as the sub-coupling.

[0025] The first resonator 21 and the second resonator 22 are magnetically coupled and capacitively coupled via the capacitor C12. In particular, in this embodiment, the first resonator 21 and the second resonator 22 are electromagnetically coupled with capacitive coupling as the main coupling and magnetic coupling as the secondary coupling.

[0026] The third resonator 23 and the fourth resonator 24 are magnetically coupled and capacitively coupled via the capacitors C34A and C34B. In particular, in this embodiment, the third resonator 23 and the fourth resonator 24 are electromagnetically coupled with capacitive coupling as the main coupling and magnetic coupling as the secondary coupling.

[0027] Further, the first resonator 21 is magnetically coupled to the third resonator 23 that is not adjacent in the circuit configuration. The fourth resonator 24 is magnetically coupled to the second resonator 22 that is not adjacent in the circuit configuration. In this way, the electromagnetic coupling between two resonators that are not adjacent in the circuit configuration is called a skip coupling. In FIG. 1, the curve marked with the symbol Mc shows the magnetic coupling between two resonators that are not adjacent in the circuit configuration.

[0028] Here, the operation of the bandpass filter 1 will be described. The bandpass filter 1 is a bandpass filter having a predetermined frequency band as a passband. Also, the bandpass filter 1 is a so-called balanced type bandpass filter. In the bandpass filter 1, an unbalanced signal is input and output at the unbalanced port 11, a first balanced element signal is input and output at the first balanced port 12, and a second balanced element signal is input and output at the second balanced port 13. The first balanced element signal and the second balanced element signal constitute a balanced signal. The bandpass filter 1 performs conversion between the unbalanced signal and the balanced signal.

[0029] Next, with reference to FIGS. 2 to 4, the structure of the bandpass filter 1 will be described. FIGS. 2 and 3 are perspective views of the bandpass filter 1. FIG. 4 is a perspective view showing the inside of the bandpass filter 1. The bandpass filter 1 further includes ports 11 to 13, first to fourth resonators 21 to 24, and a laminate 30 for integrating capacitors C1, C2A, C2B, C3A, C3B, C4A, C4B, C11, C12, C23A, C23B, C34A, and C34B. As will be described in detail later, the laminate 30 includes a plurality of stacked dielectric layers, a plurality of conductor layers, and a plurality of through holes.

[0030] The laminate 30 has a rectangular parallelepiped shape. The laminate 30 has an upper surface 30A, a bottom surface 30B, and four side surfaces 30C to 30F that constitute the outer peripheral portion of the laminate 30. 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 upper surface 30A and the bottom surface 30B. In the laminate 30, the direction perpendicular to the upper surface 30A and the bottom surface 30B is the stacking direction of the plurality of dielectric layers and the plurality of conductor layers. In FIGS. 2 to 4, this stacking direction is indicated by an arrow marked with the symbol T. The upper surface 30A and the bottom surface 30B are located at both ends in the stacking direction T.

[0031] Here, as shown in FIGS. 2 to 4, the X direction, the Y direction, and the Z direction are defined. The X direction, the Y direction, and the Z direction are orthogonal to each other. In the present embodiment, one direction parallel to the stacking direction is defined as the Z direction. Also, the direction opposite to the X direction is defined as the -X direction, the direction opposite to the Y direction is defined as the -Y direction, and the direction opposite to the Z direction is defined as the -Z direction.

[0032] As shown in FIGS. 2 and 3, the upper surface 30A is located at the Z-direction end of the laminate 30. The bottom surface 30B is located at the -Z-direction end of the laminate 30. The side surface 30C is located at the -X-direction end of the laminate 30. The side surface 30D is located at the X-direction end of the laminate 30. The side surface 30E is located at the -Y-direction end of the laminate 30. The side surface 30F is located at the Y-direction end of the laminate 30.

[0033] The bandpass filter 1 further includes first to eighth terminals 111, 112, 113, 114, 115, 116, 117, and 118. The first terminal 111 is arranged from the upper surface 30A through the side surface 30C to the bottom surface 30B. The second terminal 112 is arranged from the upper surface 30A through the side surface 30D to the bottom surface 30B. Each of the third to fifth terminals 113 to 115 is arranged from the upper surface 30A through the side surface 30E to the bottom surface 30B. Also, the third to fifth terminals 113 to 115 are arranged in this order in the X direction. Each of the sixth to eighth terminals 116 to 118 is arranged from the upper surface 30A through the side surface 30F to the bottom surface 30B. Also, the sixth to eighth terminals 116 to 118 are arranged in this order in the X direction.

[0034] The first terminal 111 corresponds to the unbalanced port 11. The fifth terminal 115 corresponds to the second balanced port 13. The eighth terminal 118 corresponds to the first balanced port 12. Each of the third, fourth, sixth, and seventh terminals 113, 114, 116, and 117 is connected to the ground.

[0035] Next, with reference to FIGS. 5 to 11, the laminate 30 will be described in detail. The laminate 30 includes 26 stacked dielectric layers. Hereinafter, these 26 dielectric layers will be referred to as the first to 26th dielectric layers in order from the bottom. Also, the first to 26th dielectric layers are represented by reference numerals 31 to 56.

[0036] In FIG. 5(a), the pattern formation surface of the first dielectric layer 31 is shown. FIG. 5(a) shows terminal portions 111a to 118a that respectively form part of terminals 111 to 118.

[0037] In FIG. 5(b), the pattern formation surface of the second dielectric layer 32 is shown. Ground conductor layers 321 and 322 are formed on the pattern formation surface of the dielectric layer 32. The ground conductor layer 321 is connected to the fourth and seventh terminals 114 and 117. The ground conductor layer 322 is connected to the third and sixth terminals 113 and 116.

[0038] In FIG. 6(a), the pattern formation surface of the third dielectric layer 33 is shown. Conductor layers 331, 332, 333, and 334 are formed on the pattern formation surface of the dielectric layer 33. The conductor layer 333 is connected to the eighth terminal 118. The conductor layer 334 is connected to the fifth terminal 115.

[0039] In FIG. 6(b), the pattern formation surface of the fourth dielectric layer 34 is shown. Conductor layers 341, 342, 343, and 344 are formed on the pattern formation surface of the dielectric layer 34. Further, through holes 34T1, 34T2, 34T3, and 34T4 are formed in the dielectric layer 34. The through holes 34T1, 34T2, 34T3, and 34T4 are respectively connected to the conductor layers 341, 342, 343, and 344.

[0040] In FIG. 7(a), the pattern formation surface of the fifth dielectric layer 35 is shown. A conductor layer 351 is formed on the pattern formation surface of the dielectric layer 35. Further, through holes 35T1, 35T2, 35T3, 35T4, and 35T5 are formed in the dielectric layer 35. The through holes 35T1, 35T2, 35T3, and 35T4 are respectively connected to the through holes 34T1, 34T2, 34T3, and 34T4 formed in the fourth dielectric layer 34. The through hole 34T5 is connected to the conductor layer 351.

[0041] In FIG. 7(b), the pattern formation surface of the sixth dielectric layer 36 is shown. A conductor layer 361 is formed on the pattern formation surface of the dielectric layer 36. Further, through holes 36T1, 36T2, 36T3, 36T4, 36T5, 36T6 are formed in the dielectric layer 36. Through holes 35T1, 35T2, 35T3, 35T4, 35T5 formed in the fifth dielectric layer 35 are respectively connected to the through holes 36T1, 36T2, 36T3, 36T4, 36T5. The through hole 36T6 is connected to the conductor layer 361.

[0042] In FIG. 8(a), the pattern formation surface of the seventh dielectric layer 37 is shown. A conductor layer 371 is formed on the pattern formation surface of the dielectric layer 37. Further, through holes 37T1, 37T2, 37T3, 37T4, 37T5, 37T6 are formed in the dielectric layer 37. Through holes 36T1, 36T2, 36T3, 36T4, 36T6 formed in the sixth dielectric layer 36 are respectively connected to the through holes 37T1, 37T2, 37T3, 37T4, 37T6. The through hole 37T5 and the through hole 36T5 formed in the dielectric layer 36 are connected to the conductor layer 371.

[0043] In FIG. 8(b), the pattern formation surface of the eighth dielectric layer 38 is shown. A conductor layer 381 is formed on the pattern formation surface of the dielectric layer 38. The conductor layer 381 is connected to the first terminal 111. Further, through holes 38T1, 38T2, 38T3, 38T4, 38T5 are formed in the dielectric layer 38. Through holes 37T1, 37T2, 37T3, 37T4, 37T5 formed in the seventh dielectric layer 37 are respectively connected to the through holes 38T1, 38T2, 38T3, 38T4, 38T5. The through hole 37T6 formed in the seventh dielectric layer 37 is connected to the conductor layer 381.

[0044] In Fig. 9, (a) shows the pattern formation surfaces of each of the dielectric layers 39 to 48 from the 9th layer to the 18th layer. Through holes 39T1, 39T2, 39T3, 39T4, 39T5 are formed in each of the dielectric layers 39 to 48. Through holes 38T1, 38T2, 38T3, 38T4, 38T5 formed in the 8th dielectric layer 38 are respectively connected to the through holes 39T1, 39T2, 39T3, 39T4, 39T5 formed in the 9th dielectric layer 39. Also, in the dielectric layers 39 to 49, the through holes with the same reference numerals adjacent to each other vertically are connected to each other.

[0045] In Fig. 9, (b) shows the pattern formation surfaces of each of the dielectric layers 49 and 50 of the 19th layer and the 20th layer. A resonator conductor layer 491 is formed on each of the pattern formation surfaces of the dielectric layers 49 and 50. The resonator conductor layer 491 is connected to the 5th and 8th terminals 115 and 118. Also, through holes 49T1, 49T2, 49T3, 49T4, 49T5 are formed in each of the dielectric layers 49 and 50. Through holes 39T1, 39T2, 39T3, 39T4, 39T5 formed in the 18th dielectric layer 48 are respectively connected to the through holes 49T1, 49T2, 49T3, 49T4, 49T5 formed in the 19th dielectric layer 49. Also, in the dielectric layers 49 and 50, the through holes with the same reference numerals adjacent to each other vertically are connected to each other.

[0046] In Fig. 10, (a) shows the pattern formation surfaces of each of the dielectric layers 51 and 52 of the 21st layer and the 22nd layer. Through holes 51T1, 51T2, 51T3, 51T4, 51T5 are formed in each of the dielectric layers 51 and 52. Through holes 49T1, 49T2, 49T3, 49T4, 49T5 formed in the 20th dielectric layer 50 are respectively connected to the through holes 51T1, 51T2, 51T3, 51T4, 51T5 formed in the 21st dielectric layer 51. Also, in the dielectric layers 51 and 52, the through holes with the same reference numerals adjacent to each other vertically are connected to each other.

[0047] In FIG. 10, (b) shows the pattern formation surface of the 23rd dielectric layer 53. A resonator conductor layer 531 is formed on the pattern formation surface of the dielectric layer 53. The resonator conductor layer 531 is connected to the third and sixth terminals 113 and 116. Further, through holes 53T1, 53T2, 53T3, 53T4, and 53T5 are formed in the dielectric layer 53. Through holes 51T1, 51T2, 51T3, and 51T4 formed in the 22nd dielectric layer 52 are connected to the through holes 53T1, 53T2, 53T3, and 53T4, respectively. The through hole 53T5 and the through hole 51T5 formed in the 22nd dielectric layer 52 are connected to a part of the resonator conductor layer 531 that includes the center in the longitudinal direction of the resonator conductor layer 531.

[0048] In FIG. 11, (a) shows the pattern formation surface of the 24th dielectric layer 54. Resonator conductor layers 541, 542, and 543 are formed on the pattern formation surface of the dielectric layer 54. The resonator conductor layer 541 is connected to the third and sixth terminals 113 and 116. The through hole 53T5 formed in the 23rd dielectric layer 53 is connected to a part of the resonator conductor layer 541 that includes the center in the longitudinal direction of the resonator conductor layer 541. Each of the resonator conductor layers 542 and 543 has a first end and a second end located on opposite sides of each other.

[0049] Further, through holes 54T1, 54T2, 54T3, and 54T4 are formed in the dielectric layer 54. The through hole 54T1 and the through hole 53T1 formed in the dielectric layer 53 are connected to a portion near the first end of the resonator conductor layer 542. The through hole 54T2 and the through hole 53T2 formed in the dielectric layer 53 are connected to a portion near the second end of the resonator conductor layer 542. The through hole 54T3 and the through hole 53T3 formed in the dielectric layer 53 are connected to a portion near the first end of the resonator conductor layer 543. The through hole 54T4 and the through hole 53T4 formed in the dielectric layer 53 are connected to a portion near the second end of the resonator conductor layer 543.

[0050] In FIG. 11(b), the pattern formation surface of the 25th dielectric layer 55 is shown. On the pattern formation surface of the dielectric layer 55, resonator conductor layers 552 and 553 are formed. Each of the resonator conductor layers 552 and 553 has a first end and a second end located on opposite sides of each other. The through hole 54T1 formed in the 24th dielectric layer 54 is connected to the vicinity of the first end in the resonator conductor layer 552. The through hole 54T2 formed in the dielectric layer 54 is connected to the vicinity of the second end in the resonator conductor layer 552. The through hole 54T3 formed in the dielectric layer 54 is connected to the vicinity of the first end in the resonator conductor layer 553. The through hole 54T4 formed in the dielectric layer 54 is connected to the vicinity of the second end in the resonator conductor layer 553.

[0051] Although not shown, a mark may be formed on the pattern formation surface of the 26th dielectric layer 56.

[0052] In the laminate 30 shown in FIGS. 2 and 3, the pattern formation surface of the first dielectric layer 31 becomes the bottom surface 30B of the laminate 30, and the surface opposite to the pattern formation surface in the 26th dielectric layer 56 becomes the top surface 30A of the laminate 30. The first to 26th dielectric layers 31 to 56 are laminated and configured. Then, the first to eighth terminals 111 to 118 are formed on the outer peripheral portion of the laminate 30, and the bandpass filter 1 shown in FIGS. 2 and 3 is completed.

[0053] Hereinafter, the correspondence between the components of the bandpass filter 1 and the components inside the laminate 30 shown in FIGS. 5 to 11 will be described. The plurality of dielectric layers of the laminate 30 include a plurality of resonator conductor layers 491, 531, 541, 542, 543, 552, 553 for constituting the first to fourth resonators 21 to 24. The plurality of through holes of the laminate 30 include a plurality of resonator through holes for constituting the first to fourth resonators 21 to 24.

[0054] The first resonator 21 is composed of resonator conductor layers 531 and 541, through-holes 35T5, 36T5, 37T5, 38T5, 53T5, through-hole 39T5 formed in each of dielectric layers 39 to 48, through-hole 49T5 formed in each of dielectric layers 49 and 50, and through-hole 51T5 formed in each of dielectric layers 51 and 52.

[0055] The second resonator 22 is composed of resonator conductor layers 542 and 552, through-holes 34T1, 34T2, 35T1, 35T2, 36T1, 36T2, 37T1, 37T2, 38T1, 38T2, 53T1, 53T2, 54T1, 54T2, through-holes 39T1 and 39T2 formed in each of dielectric layers 39 to 48, through-holes 49T1 and 49T2 formed in each of dielectric layers 49 and 50, and through-holes 51T1 and 51T2 formed in each of dielectric layers 51 and 52.

[0056] As shown in FIG. 4, the second resonator 22 includes a first through-hole row 22A, a second through-hole row 22B, and a conductor layer portion 22C. The first through-hole row 22A is configured by connecting in series through-holes 34T1, 35T1, 36T1, 37T1, 38T1, 53T1, through-hole 39T1 formed in each of dielectric layers 39 to 48, through-hole 49T1 formed in each of dielectric layers 49 and 50, and through-hole 51T1 formed in each of dielectric layers 51 and 52. Also, the first through-hole row 22A penetrates dielectric layers 34 to 53.

[0057] The second through-hole row 22B is configured by connecting in series through-holes 34T2, 35T2, 36T2, 37T2, 38T2, 53T2, through-hole 39T2 formed in each of dielectric layers 39 to 48, through-hole 49T2 formed in each of dielectric layers 49 and 50, and through-hole 51T2 formed in each of dielectric layers 51 and 52. Also, the second through-hole row 22B penetrates dielectric layers 34 to 53.

[0058] The conductor layer portion 22C is composed of resonator conductor layers 542 and 552 connected to each other by through holes 54T1 and 54T2. Further, the conductor layer portion 22C connects one end of the first through hole row 22A and one end of the second through hole row 22B.

[0059] The third resonator 23 is composed of resonator conductor layers 543 and 553, through holes 34T3, 34T4, 35T3, 35T4, 36T3, 36T4, 37T3, 37T4, 38T3, 38T4, 53T3, 53T4, 54T3, 54T4, through holes 39T3 and 39T4 formed in each of the dielectric layers 39 to 48, through holes 49T3 and 49T4 formed in each of the dielectric layers 49 and 50, and through holes 51T3 and 51T4 formed in each of the dielectric layers 51 and 52.

[0060] As shown in FIG. 4, the third resonator 23 includes a first through hole row 23A, a second through hole row 23B, and a conductor layer portion 23C. The first through hole row 23A is configured by connecting in series through holes 34T3, 35T3, 36T3, 37T3, 38T3, 53T3, through holes 39T3 formed in each of the dielectric layers 39 to 48, through holes 49T3 formed in each of the dielectric layers 49 and 50, and through holes 51T3 formed in each of the dielectric layers 51 and 52. Further, the first through hole row 23A penetrates the dielectric layers 34 to 53.

[0061] The second through hole row 23B is configured by connecting in series through holes 34T4, 35T4, 36T4, 37T4, 38T4, 53T4, through holes 39T4 formed in each of the dielectric layers 39 to 48, through holes 49T4 formed in each of the dielectric layers 49 and 50, and through holes 51T4 formed in each of the dielectric layers 51 and 52. Further, the second through hole row 23B penetrates the dielectric layers 34 to 53.

[0062] The conductor layer portion 23C is composed of resonator conductor layers 543 and 553 that are connected to each other by through-holes 54T3 and 54T4. Further, the conductor layer portion 23C connects one end of the first through-hole row 23A and one end of the second through-hole row 23B.

[0063] The fourth resonator 24 is composed of resonator conductor layers 491 formed in each of the dielectric layers 49 and 50.

[0064] The capacitor C1 is composed of conductor layers 322 and 351 and dielectric layers 32 to 34 between the conductor layers 322 and 351.

[0065] The capacitor C2A is composed of conductor layers 321 and 341 and dielectric layers 32 and 33 between the conductor layers 321 and 341. The capacitor C2B is composed of conductor layers 321 and 342 and dielectric layers 32 and 33 between the conductor layers 321 and 342.

[0066] The capacitor C3A is composed of conductor layers 321 and 343 and dielectric layers 32 and 33 between the conductor layers 321 and 343. The capacitor C3B is composed of conductor layers 321 and 344 and dielectric layers 32 and 33 between the conductor layers 321 and 344.

[0067] The capacitor C4A is composed of conductor layers 321 and 333 and dielectric layer 32 between the conductor layers 321 and 333. The capacitor C4B is composed of conductor layers 321 and 334 and dielectric layer 32 between the conductor layers 321 and 334.

[0068] The capacitor C11 is composed of conductor layers 351, 361, 371, 381, dielectric layer 35 between the conductor layers 351 and 361, dielectric layer 36 between the conductor layers 361 and 371, and dielectric layer 37 between the conductor layers 371 and 381. The capacitor C12 is composed of conductor layers 341 and 351 and dielectric layer 34 between the conductor layers 341 and 351.

[0069] The capacitor C23A is composed of conductor layers 331, 341, 343 and a dielectric layer 33 between the conductor layer 331 and the conductor layers 341, 343. The capacitor C23B is composed of conductor layers 332, 342, 344 and a dielectric layer 33 between the conductor layer 332 and the conductor layers 342, 344.

[0070] The capacitor C34A is composed of conductor layers 333, 343 and a dielectric layer 33 between the conductor layers 333, 343. The capacitor C34B is composed of conductor layers 334, 344 and a dielectric layer 33 between the conductor layers 334, 344.

[0071] Next, the structural features of the band - pass filter 1 will be described. As shown in FIG. 4, the distance between the second resonator 22 and the third resonator 23 is smaller than the distance between the first resonator 21 and the second resonator 22 and smaller than the distance between the third resonator 23 and the fourth resonator 24.

[0072] As shown in FIG. 9(b), the resonator conductor layer 491 formed on the dielectric layer 49 and the resonator conductor layer 491 formed on the dielectric layer 50 are arranged so as to overlap each other when viewed from the Z - direction. Also, as shown in FIGS. 10(b) and 11(a), the resonator conductor layer 531 formed on the dielectric layer 53 and the resonator conductor layer 541 formed on the dielectric layer 54 are arranged so as to overlap each other when viewed from the Z - direction. Also, as shown in FIGS. 11(a) and (b), the resonator conductor layer 542 formed on the dielectric layer 54 and the resonator conductor layer 552 formed on the dielectric layer 55 are arranged so as to overlap each other when viewed from the Z - direction, and the resonator conductor layer 543 formed on the dielectric layer 54 and the resonator conductor layer 553 formed on the dielectric layer 55 are arranged so as to overlap each other when viewed from the Z - direction.

[0073] As described above, in the bandpass filter 1 according to the present embodiment, the second resonator 22 and the third resonator 23 are electromagnetically coupled with magnetic coupling as the main coupling, the first resonator 21 is capacitively coupled with the third resonator 23, and the fourth resonator 24 is capacitively coupled with the second resonator 22. According to the present embodiment, due to these couplings, while satisfying the balance characteristics, in each of the first vicinity region, which is a frequency region lower than the passband and closer to the passband, and the second vicinity region, which is a frequency region higher than the passband and closer to the passband, an attenuation pole where the insertion loss changes steeply can be formed.

[0074] Hereinafter, the attenuation pole will be described with reference to the simulation results. In the simulation, first to fifth models of a bandpass filter having the same circuit configuration as the bandpass filter 1 according to the present embodiment were used. In the simulation, the bandpass filter was designed such that the passband of the bandpass filter included a frequency band of 3.3 to 3.9 GHz. Also, in the simulation, the pass characteristics of the bandpass filter were represented using the mixed-mode S parameter representing the response of the difference signal between the first and second balanced element signals output from the first and second balanced ports 12 and 13 when an unbalanced signal was input to the unbalanced port 11. Hereinafter, this S parameter will be referred to as the insertion loss.

[0075] Here, the magnetic coupling coefficient between the second resonator 22 and the third resonator 23 is represented by the symbol k23, the magnetic coupling coefficient of the capacitive coupling between the first resonator 21 and the third resonator 23 is represented by the symbol k13, and the magnetic coupling coefficient of the capacitive coupling between the second resonator 22 and the fourth resonator 24 is represented by the symbol k24. The first to fifth models are models in which the magnetic coupling coefficients k23, k13, and k24 are made different from each other. In the simulation, the pass characteristics of each of the first to fifth models were obtained.

[0076] First, the passing characteristics of each of the first and second models will be described. The first model is a model in which the magnetic coupling coefficient k23 is 0.37 and the magnetic coupling coefficients k13 and k24 of the jump coupling are both 0. The second model is a model in which the magnetic coupling coefficient k23 is 0.07 and the magnetic coupling coefficients k13 and k24 of the jump coupling are both 0.

[0077] FIG. 12 shows the passing characteristics of the first model. FIG. 13 shows the passing characteristics of the second model. In FIGS. 12 and 13, the horizontal axis represents the frequency and the vertical axis represents the insertion loss. From FIG. 12, it can be seen that when the magnetic coupling coefficient k23 is increased and the second resonator 22 and the third resonator 23 are electromagnetically coupled with magnetic coupling as the main coupling, an attenuation pole is formed in a frequency region higher than the passband of the bandpass filter. Also, from FIG. 13, it can be seen that when the magnetic coupling coefficient k23 is decreased and the second resonator 22 and the third resonator 23 are electromagnetically coupled with capacitive coupling as the main coupling, an attenuation pole is formed in a frequency region lower than the passband of the bandpass filter.

[0078] Generally, in a bandpass filter composed of two resonators, when the magnetic coupling coefficient between the two resonators becomes relatively large and the coupling capacitance between the two resonators becomes relatively small, an attenuation pole is formed in a frequency region higher than the center frequency of the passband of the bandpass filter. In the first and second models, in order to clarify the change in the attenuation pole due to the difference in electromagnetic coupling between the second resonator 22 and the third resonator 23, the magnetic coupling coefficients k13 and k24 of the jump coupling are set to 0. However, the above description of the change in the attenuation pole also applies when the magnetic coupling coefficients k13 and k24 are non-zero values. In the present embodiment, as described above, by electromagnetically coupling the second resonator 22 and the third resonator 23 with magnetic coupling as the main coupling, an attenuation pole is formed in the vicinity of the second.

[0079] Next, the passing characteristics of the third model will be described. The third model has a magnetic coupling coefficient k23 of 0.37, a magnetic coupling coefficient k13 of 0.032 for the jump-over coupling, and a magnetic coupling coefficient k24 of 0 for the jump-over coupling.

[0080] FIG. 14 shows the passing characteristics of the third model. In FIG. 14, the horizontal axis represents the frequency, and the vertical axis represents the insertion loss. From FIG. 14 and the passing characteristics of the first model (both magnetic coupling coefficients k13 and k24 of the jump-over coupling are 0) shown in FIG. 12, it can be seen that due to the jump-over coupling between the second resonator 22 and the third resonator 23, an attenuation pole is formed in the frequency region lower than the passing band of the band-pass filter. In the present embodiment, as described above, by jump-over coupling the third resonator 23 with the first resonator 21, an attenuation pole is formed in the vicinity of the first.

[0081] Next, the passing characteristics of the fourth model will be described. The fourth model has a magnetic coupling coefficient k23 of 0.37, a magnetic coupling coefficient k13 of 0 for the jump-over coupling, and a magnetic coupling coefficient k24 of 0.02 for the jump-over coupling.

[0082] FIG. 15 shows the passing characteristics of the fourth model. In FIG. 15, the horizontal axis represents the frequency, and the vertical axis represents the insertion loss. From FIG. 15 and the passing characteristics of the first model (both magnetic coupling coefficients k13 and k24 of the jump-over coupling are 0) shown in FIG. 12, it can be seen that due to the jump-over coupling between the second resonator 22 and the fourth resonator 24, an attenuation pole is formed in the frequency region lower than the passing band of the band-pass filter. In the present embodiment, as described above, by jump-over coupling the fourth resonator 24 with the second resonator 22, an attenuation pole is formed in the vicinity of the first.

[0083] Next, the passing characteristics of the fifth model will be described. The fifth model has a magnetic coupling coefficient k23 of 0.37, a magnetic coupling coefficient k13 of 0.032 for the jump-over coupling, and a magnetic coupling coefficient k24 of 0.02 for the jump-over coupling.

[0084] FIG. 16 shows the passing characteristics of the fifth model. In FIG. 16, the horizontal axis represents the frequency, and the vertical axis represents the insertion loss. From FIG. 16, the passing characteristics of the third model (magnetic coupling coefficient k24 = 0) shown in FIG. 14, and the passing characteristics of the fourth model (magnetic coupling coefficient k13 = 0) shown in FIG. 15, it can be seen that the attenuation pole formed by the two skip couplings is steeper than the attenuation pole formed by the single skip coupling shown in FIGS. 14 and 15. This is because the effects of one skip coupling and the other skip coupling overlap. In this embodiment, the two skip couplings are used to make the attenuation pole formed in the first vicinity region steeper.

[0085] As can be understood from the simulation results shown in FIGS. 12 to 16, according to this embodiment, by using the magnetic coupling as the main coupling between the second resonator 22 and the third resonator 23, and at least one of the skip coupling between the first resonator 21 and the third resonator 23 and the skip coupling between the second resonator 22 and the fourth resonator 24, steep attenuation poles can be formed in each of the first and second vicinity regions. Further, according to this embodiment, by using both the skip coupling between the first resonator 21 and the third resonator 23 and the skip coupling between the second resonator 22 and the fourth resonator 24, the attenuation pole formed in the first vicinity region can be made steeper.

[0086] Incidentally, in the present embodiment, the distance between the second resonator 22 and the third resonator 23 is made smaller than the distance between the first resonator 21 and the second resonator 22 and smaller than the distance between the third resonator 23 and the fourth resonator 24. In particular, in the present embodiment, the distance between the second resonator 22 and the third resonator 23 is made relatively small, so that while the magnetic coupling between the second resonator 22 and the third resonator 23 is made relatively strong, the capacitive coupling between the second resonator 22 and the third resonator 23 is also made relatively strong. As a result, the frequency of the attenuation pole formed in the vicinity of the second resonator becomes a frequency close to the passband. Thus, according to the present embodiment, it is possible to realize a characteristic in which the insertion loss changes steeply in the vicinity of the passband. An example in which the distance between the second resonator 22 and the third resonator 23 is made larger than in the present embodiment will be described in the second embodiment.

[0087] Also, according to the present embodiment, while satisfying the balance characteristics, it is possible to form the attenuation pole as described above. This effect will be described later with reference to an example of the characteristics of the bandpass filter 1.

[0088] Also, in the present embodiment, each of the second to fourth resonators 22 to 24 is an open-ended resonator. In an open-ended resonator, a circuit configuration symmetric about the resonator can be adopted. In the present embodiment, as shown in FIG. 1, a symmetric circuit configuration is adopted in which the capacitors C2A, C3A, C4A, C23A, C34A and the capacitors C2B, C3B, C4B, C23B, C34B are paired with the second to fourth resonators 22 to 24 as the center.

[0089] Here, the two ends of the open-ended resonator are referred to as the first end and the second end. In an open-ended resonator, if the balance between the electric field and the magnetic field on the first end side and the second end side is lost, the balance characteristics deteriorate. In the present embodiment, by providing the fourth resonator 24, the circuit configuration of the bandpass filter 1 is made more symmetric than in the case where the fourth resonator 24 is not provided. Thus, according to the present embodiment, it is possible to further relax the imbalance between the electric field and the magnetic field and improve the balance characteristics.

[0090] Next, with reference to FIGS. 17 to 22, an example of the characteristics of the bandpass filter 1 according to the present embodiment will be described. Here, an example of the characteristics of the bandpass filter 1 when designed such that the passband of the bandpass filter 1 includes a frequency band of 3.3 GHz to 3.9 GHz is shown.

[0091] FIG. 17 shows an example of the pass characteristics of the bandpass filter 1. FIG. 18 shows an enlarged view of a part of FIG. 17. Here, the insertion loss is shown as the pass characteristic of the bandpass filter 1. In FIGS. 17 and 18, the horizontal axis represents the frequency, and the vertical axis represents the insertion loss. As shown in FIG. 17, it can be seen that in each of the first and second vicinity regions of the bandpass filter 1, attenuation poles are formed where the insertion loss changes steeply.

[0092] Also, the insertion loss is preferably 2.5 dB or less. As shown in FIG. 18, in the bandpass filter 1, in the above-mentioned frequency band, the insertion loss is 2.5 or less.

[0093] FIG. 19 shows an example of the amplitude balance characteristic of the bandpass filter 1. Here, the amplitude balance characteristic of the bandpass filter 1 is represented by the difference in amplitude (hereinafter referred to as the amplitude difference) between the first and second balanced element signals output from the first and second balanced ports 12 and 13 when an unbalanced signal is input to the unbalanced port 11. The amplitude difference is represented by a positive value when the amplitude of the first balanced element signal is larger than the amplitude of the second balanced element signal, and is represented by a negative value when the amplitude of the first balanced element signal is smaller than the amplitude of the second balanced element signal. In FIG. 19, the horizontal axis represents the frequency, and the vertical axis represents the amplitude difference. When the amplitude difference is represented as m (dB), the value of m is preferably -1.5 or more and 1.5 or less, and more preferably -1.0 or more and 1.0 or less. As shown in FIG. 19, in the bandpass filter 1, in the above-mentioned frequency band, the value of m is -1.0 or more and 1.0 or less.

[0094] Figure 20 shows an example of the phase balance characteristics of the band-pass filter 1. Here, the phase balance characteristics of the band-pass filter 1 are represented by the phase difference (hereinafter referred to as the phase difference) between the first and second balanced element signals output from the first and second balanced ports 12 and 13 when an unbalanced signal is input to the unbalanced port 11. The phase difference represents the magnitude by which the phase of the first balanced element signal leads the phase of the second balanced element signal. In Figure 20, the horizontal axis represents the frequency, and the vertical axis represents the phase difference. When the amplitude difference is represented as p (deg), the value of p is preferably 165 or more and 195 or less. As shown in Figure 20, in the band-pass filter 1, in the above-mentioned frequency band, the value of p is 165 or more and 195 or less.

[0095] Figure 21 shows an example of the reflection characteristics of the unbalanced port 11 of the band-pass filter 1. Figure 22 shows an example of the reflection characteristics of the first and second balanced ports 12 and 13 of the band-pass filter 1. In Figures 21 and 22, the horizontal axis represents the frequency, and the vertical axis represents the reflection loss. The reflection loss is preferably 10 dB or more. As shown in Figures 21 and 22, in the band-pass filter 1, in the above-mentioned frequency band, the reflection loss is 10 dB or more.

[0096] As described above, the band-pass filter 1 having the characteristics shown in Figures 17 to 22 can be used in at least the frequency band of 3.3 GHz to 3.9 GHz and has good balance characteristics in this frequency band. Also, as can be understood from Figures 17 to 22, according to this band-pass filter 1, while satisfying the balance characteristics, steep attenuation poles can be formed in each of the first and second adjacent regions.

[0097] [Second Embodiment] Next, a second embodiment of the present invention will be described. First, with reference to Figure 23, the circuit configuration of the band-pass filter according to this embodiment will be briefly described. Figure 23 shows the circuit configuration of the band-pass filter according to this embodiment.

[0098] The circuit configuration of the band-pass filter 101 according to this embodiment is different from that of the band-pass filter 1 in the first embodiment in the following points. In this embodiment, a capacitor C23B that connects one end on the capacitor C2B side of the second resonator 22 and one end on the capacitor C3B side of the third resonator 23 is not provided. The other circuit configuration of the band-pass filter 101 is the same as that of the band-pass filter 1 according to the first embodiment.

[0099] Next, the structure of the band-pass filter 101 will be described. FIG. 24 is a perspective view showing the inside of the band-pass filter 101. Similar to the band-pass filter 1 according to the first embodiment, the band-pass filter 101 includes a laminate 30 and first to eighth terminals 111 to 118 (see FIGS. 2 and 3). The laminate 30 in this embodiment is for integrating ports 11 to 13, first to fourth resonators 21 to 24, and capacitors C1, C2A, C2B, C3A, C3B, C4A, C4B, C11, C12, C23A, C34A, and C34B. The shapes and arrangements of the first to eighth terminals 111 to 118 are the same as those in the first embodiment.

[0100] Next, with reference to FIGS. 25 to 32, the laminate 30 in this embodiment will be described in detail. In this embodiment, the laminate 30 includes 25 stacked dielectric layers instead of the dielectric layers 31 to 56 in the first embodiment. Hereinafter, these 25 dielectric layers will be referred to as the first to 25th dielectric layers in order from the bottom. Also, the first to 25th dielectric layers are represented by reference numerals 61 to 85.

[0101] In FIG. 25, (a) shows the pattern formation surface of the first dielectric layer 61. FIG. 25(a) shows terminal portions 111a to 118a that respectively form part of the terminals 111 to 118.

[0102] In FIG. 25, (b) shows the pattern formation surface of the second dielectric layer 62. A ground conductor layer 621 is formed on the pattern formation surface of the dielectric layer 62. The ground conductor layer 621 is connected to the fourth and seventh terminals 114 and 117.

[0103] In FIG. 26, (a) shows the pattern formation surface of the third dielectric layer 63. A conductor layer 631 is formed on the pattern formation surface of the dielectric layer 63. Further, a through hole 63T5 is formed in the dielectric layer 63. The through hole 63T5 is connected to the conductor layer 631.

[0104] In FIG. 26, (b) shows the pattern formation surface of the fourth dielectric layer 64. Conductor layers 641, 642, and 643 are formed on the pattern formation surface of the dielectric layer 64. The through hole 63T5 formed in the third dielectric layer 63 is connected to the conductor layer 641. The conductor layer 632 is connected to the eighth terminal 118. The conductor layer 633 is connected to the fifth terminal 115.

[0105] In FIG. 27, (a) shows the pattern formation surface of the fifth dielectric layer 65. Conductor layers 651, 652, 653, and 654 are formed on the pattern formation surface of the dielectric layer 65. Further, through holes 65T1, 65T2, 65T3, and 65T4 are formed in the dielectric layer 65. The through holes 65T1, 65T2, 65T3, and 65T4 are connected to the conductor layers 651, 652, 653, and 654, respectively.

[0106] In FIG. 27, (b) shows the pattern formation surface of the sixth dielectric layer 66. A conductor layer 661 is formed on the pattern formation surface of the dielectric layer 66. Further, through holes 66T1, 66T2, 66T3, 66T4, and 66T5 are formed in the dielectric layer 66. The through holes 65T1, 65T2, 65T3, and 65T4 formed in the fifth dielectric layer 65 are connected to the through holes 66T1, 66T2, 66T3, and 66T4, respectively. The through hole 66T5 is connected to the conductor layer 661.

[0107] In FIG. 28(a), the pattern formation surfaces of the seventh and eighth dielectric layers 67 and 68 are shown. Through holes 67T1, 67T2, 67T3, 67T4, and 67T5 are formed in each of the dielectric layers 67 and 68. Through holes 66T1, 66T2, 66T3, 66T4, and 66T5 formed in the sixth dielectric layer 66 are connected to the through holes 67T1, 67T2, 67T3, 67T4, and 67T5 formed in the seventh dielectric layer 67, respectively. Also, in the dielectric layers 67 and 68, the through holes with the same reference numerals adjacent to each other vertically are connected to each other.

[0108] In FIG. 28(b), the pattern formation surface of the ninth dielectric layer 69 is shown. A conductor layer 691 is formed on the pattern formation surface of the dielectric layer 69. The conductor layer 691 is connected to the first terminal 111. Also, through holes 69T1, 69T2, 69T3, 69T4, and 69T5 are formed in the dielectric layer 69. Through holes 67T1, 67T2, 67T3, 67T4, and 67T5 formed in the eighth dielectric layer 68 are connected to the through holes 69T1, 69T2, 69T3, 69T4, and 69T5, respectively.

[0109] In FIG. 29(a), the pattern formation surface of the tenth dielectric layer 70 is shown. A conductor layer 701 is formed on the pattern formation surface of the dielectric layer 70. Also, through holes 70T1, 70T2, 70T3, 70T4, and 70T5 are formed in the dielectric layer 70. Through holes 69T1, 69T2, 69T3, and 69T4 formed in the ninth dielectric layer 69 are connected to the through holes 70T1, 70T2, 70T3, and 70T4, respectively. The through hole 70T5 and the through hole 69T5 formed in the ninth dielectric layer 69 are connected to the conductor layer 701.

[0110] In FIG. 29, (b) shows the pattern formation surfaces of the dielectric layers 71 to 76 of the 11th to 16th layers. Through holes 71T1, 71T2, 71T3, 71T4, 71T5 are formed in each of the dielectric layers 71 to 76. Through holes 70T1, 70T2, 70T3, 70T4, 70T5 formed in the 10th dielectric layer 70 are connected to the through holes 71T1, 71T2, 71T3, 71T4, 71T5 formed in the 11th dielectric layer 71, respectively. Also, in the dielectric layers 71 to 76, through holes with the same reference numerals adjacent to each other vertically are connected to each other.

[0111] In FIG. 30, (a) shows the pattern formation surfaces of the 17th and 18th dielectric layers 77 and 78. A resonator conductor layer 771 is formed on each of the pattern formation surfaces of the dielectric layers 77 and 78. The resonator conductor layer 771 is connected to the fifth and eighth terminals 115 and 118. Also, through holes 77T1, 77T2, 77T3, 77T4, 77T5 are formed in each of the dielectric layers 77 and 78. Through holes 71T1, 71T2, 71T3, 71T4, 71T5 formed in the 16th dielectric layer 76 are connected to the through holes 77T1, 77T2, 77T3, 77T4, 77T5 formed in the 17th dielectric layer 77, respectively. Also, in the dielectric layers 77 and 78, through holes with the same reference numerals adjacent to each other vertically are connected to each other.

[0112] In FIG. 30, (b) shows the pattern formation surfaces of the 19th and 20th dielectric layers 79 and 80. Also, through holes 79T1, 79T2, 79T3, 79T4, 79T5 are formed in each of the dielectric layers 79 and 80. Through holes 77T1, 77T2, 77T3, 77T4, 77T5 formed in the 18th dielectric layer 78 are connected to the through holes 79T1, 79T2, 79T3, 79T4, 79T5 formed in the 19th dielectric layer 79, respectively. Also, in the dielectric layers 79 and 80, through holes with the same reference numerals adjacent to each other vertically are connected to each other.

[0113] In Fig. 31, (a) shows the pattern formation surface of the 21st dielectric layer 81. A resonator conductor layer 811 is formed on the pattern formation surface of the dielectric layer 81. The resonator conductor layer 811 is connected to the third and sixth terminals 113, 116. Further, through holes 81T1, 81T2, 81T3, 81T4, 81T5 are formed in the dielectric layer 81. Through holes 79T1, 79T2, 79T3, 79T4 formed in the 20th dielectric layer 80 are respectively connected to the through holes 81T1, 81T2, 81T3, 81T4. The through hole 81T5 and the through hole 79T5 formed in the 20th dielectric layer 80 are connected to a part of the resonator conductor layer 811 including the center in the longitudinal direction of the resonator conductor layer 811.

[0114] In Fig. 31, (b) shows the pattern formation surface of the 22nd dielectric layer 82. A resonator conductor layer 821 is formed on the pattern formation surface of the dielectric layer 82. The resonator conductor layer 821 is connected to the third and sixth terminals 113, 116. The through hole 81T5 formed in the 21st dielectric layer 81 is connected to a part of the resonator conductor layer 821 including the center in the longitudinal direction of the resonator conductor layer 821. Further, through holes 82T1, 82T2, 82T3, 82T4, 82T5 are formed in the dielectric layer 82. Through holes 81T1, 81T2, 81T3, 81T4 formed in the dielectric layer 81 are respectively connected to the through holes 82T1, 82T2, 82T3, 82T4.

[0115] In FIG. 32, (a) shows the pattern formation surface of the 23rd dielectric layer 83. On the pattern formation surface of the dielectric layer 83, resonator conductor layers 832 and 833 are formed. Each of the resonator conductor layers 832 and 833 has a first end and a second end located on opposite sides of each other. Further, through holes 83T1, 83T2, 83T3, and 83T4 are formed in the dielectric layer 83. The through hole 83T1 and the through hole 82T1 formed in the 22nd dielectric layer 82 are connected to the vicinity of the first end in the resonator conductor layer 832. The through hole 83T2 and the through hole 82T2 formed in the dielectric layer 82 are connected to the vicinity of the second end in the resonator conductor layer 832. The through hole 83T3 and the through hole 82T3 formed in the dielectric layer 82 are connected to the vicinity of the first end in the resonator conductor layer 833. The through hole 83T4 and the through hole 82T4 formed in the dielectric layer 82 are connected to the vicinity of the second end in the resonator conductor layer 833.

[0116] In FIG. 32, (b) shows the pattern formation surface of the 24th dielectric layer 84. On the pattern formation surface of the dielectric layer 84, resonator conductor layers 842 and 843 are formed. Each of the resonator conductor layers 842 and 843 has a first end and a second end located on opposite sides of each other. The through hole 83T1 formed in the 24th dielectric layer 83 is connected to the vicinity of the first end in the resonator conductor layer 842. The through hole 83T2 formed in the dielectric layer 83 is connected to the vicinity of the second end in the resonator conductor layer 842. The through hole 83T3 formed in the dielectric layer 83 is connected to the vicinity of the first end in the resonator conductor layer 843. The through hole 83T4 formed in the dielectric layer 83 is connected to the vicinity of the second end in the resonator conductor layer 843.

[0117] Although not shown, a mark may be formed on the pattern formation surface of the 25th dielectric layer 85.

[0118] In the laminate 30 according to this embodiment, the pattern formation surface of the first dielectric layer 61 is the bottom surface 30B of the laminate 30 (see FIGS. 2 and 3), and the surface on the side opposite to the pattern formation surface in the 25th dielectric layer 85 is the top surface 30A of the laminate 30 (see FIGS. 2 and 3). The first to 25th dielectric layers 61 to 85 are laminated and configured. Then, the first to eighth terminals 111 to 118 are formed on the outer peripheral portion of the laminate 30, and the bandpass filter 101 is completed.

[0119] Hereinafter, the correspondence between the components of the bandpass filter 101 and the internal components of the laminate 30 shown in FIGS. 25 to 32 will be described. In this embodiment, the plurality of dielectric layers of the laminate 30 include a plurality of resonator conductor layers 771, 811, 821, 832, 833, 842, 843 for constituting the first to fourth resonators 21 to 24.

[0120] The first resonator 21 is constituted by resonator conductor layers 811, 821, through holes 70T5, 81T5, through holes 71T5 formed in each of the dielectric layers 71 to 76, through holes 77T5 formed in each of the dielectric layers 77, 78, and through holes 79T5 formed in each of the dielectric layers 79, 80.

[0121] The second resonator 22 is constituted by resonator conductor layers 832, 842, through holes 65T1, 65T2, 66T1, 66T2, 69T1, 69T2, 70T1, 70T2, 81T1, 81T2, 82T1, 82T2, 83T1, 83T2, through holes 67T1, 67T2 formed in each of the dielectric layers 67, 68, through holes 71T1, 71T2 formed in each of the dielectric layers 71 to 76, through holes 77T1, 77T2 formed in each of the dielectric layers 77, 78, and through holes 79T1, 79T2 formed in each of the dielectric layers 79, 80.

[0122] Similar to the first embodiment, the second resonator 22 includes a first through-hole row 22A, a second through-hole row 22B, and a conductor layer portion 22C (see FIG. 24). The first through-hole row 22A is configured by connecting in series through-holes 65T1, 66T1, 69T1, 70T1, 81T1, 82T1, a through-hole 67T1 formed in each of the dielectric layers 67 and 68, a through-hole 71T1 formed in each of the dielectric layers 71 to 76, a through-hole 77T1 formed in each of the dielectric layers 77 and 78, and a through-hole 79T1 formed in each of the dielectric layers 79 and 80. Also, the first through-hole row 22A penetrates the dielectric layers 65 to 82.

[0123] The second through-hole row 22B is configured by connecting in series through-holes 65T2, 66T2, 69T2, 70T2, 81T2, 82T2, a through-hole 67T2 formed in each of the dielectric layers 67 and 68, a through-hole 71T2 formed in each of the dielectric layers 71 to 76, a through-hole 77T2 formed in each of the dielectric layers 77 and 78, and a through-hole 79T2 formed in each of the dielectric layers 79 and 80. Also, the second through-hole row 22B penetrates the dielectric layers 65 to 82.

[0124] The conductor layer portion 22C is composed of resonator conductor layers 832 and 842 connected to each other by through-holes 83T1 and 83T2.

[0125] The third resonator 23 is composed of resonator conductor layers 833 and 843, through-holes 65T3, 65T4, 66T3, 66T4, 69T3, 69T4, 70T3, 70T4, 81T3, 81T4, 82T3, 82T4, 83T3, 83T4, through-holes 67T3 and 67T4 formed in each of the dielectric layers 67 and 68, through-holes 71T3 and 71T4 formed in each of the dielectric layers 71 to 76, through-holes 77T3 and 77T4 formed in each of the dielectric layers 77 and 78, and through-holes 79T3 and 79T4 formed in each of the dielectric layers 79 and 80.

[0126] Similar to the first embodiment, the third resonator 23 includes a first through-hole row 23A, a second through-hole row 23B, and a conductor layer portion 23C (see FIG. 24). The first through-hole row 23A is configured by connecting in series through-holes 65T3, 66T3, 69T3, 70T3, 81T3, 82T3, a through-hole 67T3 formed in each of the dielectric layers 67 and 68, a through-hole 71T3 formed in each of the dielectric layers 71 to 76, a through-hole 77T3 formed in each of the dielectric layers 77 and 78, and a through-hole 79T3 formed in each of the dielectric layers 79 and 80. Further, the first through-hole row 23A penetrates the dielectric layers 65 to 82.

[0127] The second through-hole row 23B is configured by connecting in series through-holes 65T4, 66T4, 69T4, 70T4, 81T4, 82T4, a through-hole 67T4 formed in each of the dielectric layers 67 and 68, a through-hole 71T4 formed in each of the dielectric layers 71 to 76, a through-hole 77T4 formed in each of the dielectric layers 77 and 78, and a through-hole 79T4 formed in each of the dielectric layers 79 and 80. Further, the second through-hole row 23B penetrates the dielectric layers 65 to 82.

[0128] The conductor layer portion 23C is composed of resonator conductor layers 833 and 843 connected to each other by through-holes 83T3 and 83T4.

[0129] The fourth resonator 24 is composed of resonator conductor layers 771 formed in each of the dielectric layers 77 and 78.

[0130] The capacitor C1 is composed of conductor layers 621 and 701 and dielectric layers 62 to 69 between the conductor layers 621 and 701.

[0131] Capacitor C2A is composed of conductor layers 621 and 651 and dielectric layers 62 to 64 between the conductor layers 621 and 651. Capacitor C2B is composed of conductor layers 621 and 652 and dielectric layers 62 to 64 between the conductor layers 621 and 652.

[0132] Capacitor C3A is composed of conductor layers 621 and 653 and dielectric layers 62 to 64 between the conductor layers 621 and 653. Capacitor C3B is composed of conductor layers 621 and 654 and dielectric layers 62 to 64 between the conductor layers 621 and 654.

[0133] Capacitor C4A is composed of conductor layers 621 and 642 and dielectric layers 62 and 63 between the conductor layers 621 and 642. Capacitor C3B is composed of conductor layers 621 and 643 and dielectric layers 62 and 63 between the conductor layers 621 and 643.

[0134] Capacitor C11 is composed of conductor layers 691 and 701 and dielectric layer 69 between the conductor layers 691 and 701. Capacitor C12 is composed of conductor layers 651 and 661 and dielectric layer 65 between the conductor layers 651 and 661.

[0135] Capacitor C23A is composed of conductor layers 631, 641, 651, and 653, dielectric layers 63 and 64 between the conductor layers 631 and 653, dielectric layer 63 between the conductor layers 631 and 641, and dielectric layer 64 between the conductor layers 641 and 651.

[0136] Capacitor C34A is composed of conductor layers 642 and 653 and dielectric layer 64 between the conductor layers 642 and 653. Capacitor C34B is composed of conductor layers 643 and 654 and dielectric layer 64 between the conductor layers 643 and 654.

[0137] Next, with reference to FIG. 24, the structural features of the band-pass filter 101 will be described. In the present embodiment, the distance between the second resonator 22 and the third resonator 23 is smaller than the distance between the first resonator 21 and the second resonator 22 and smaller than the distance between the third resonator 23 and the fourth resonator 24. Also, in the present embodiment, the distance between the second resonator 22 and the third resonator 23 is larger than the distance between the second resonator 22 and the third resonator 23 in the first embodiment (see FIG. 4).

[0138] As shown in FIG. 30(a), the resonator conductor layer 771 formed on the dielectric layer 77 and the resonator conductor layer 771 formed on the dielectric layer 78 are arranged so as to overlap each other when viewed from the Z direction. Also, as shown in FIGS. 31(a) and (b), the resonator conductor layer 811 formed on the dielectric layer 81 and the resonator conductor layer 821 formed on the dielectric layer 82 are arranged so as to overlap each other when viewed from the Z direction. Also, as shown in FIGS. 32(a) and (b), the resonator conductor layer 832 formed on the dielectric layer 83 and the resonator conductor layer 842 formed on the dielectric layer 84 are arranged so as to overlap each other when viewed from the Z direction, and the resonator conductor layer 833 formed on the dielectric layer 83 and the resonator conductor layer 843 formed on the dielectric layer 84 are arranged so as to overlap each other when viewed from the Z direction.

[0139] Next, the operation and effects of the band-pass filter 101 according to the present embodiment will be described. In the present embodiment, as in the first embodiment, in each of the first vicinity region, which is a frequency region lower than the passband and close to the passband, and the second vicinity region, which is a frequency region higher than the passband and close to the passband, an attenuation pole where the insertion loss changes steeply is formed.

[0140] In particular, in this embodiment, the distance between the second resonator 22 and the third resonator 23 is made larger than that in the first embodiment, and while the magnetic coupling between the second resonator 22 and the third resonator 23 is made weaker than that in the first embodiment, the capacitive coupling between the second resonator 22 and the third resonator 23 is also made weaker than that in the first embodiment. Specifically, by not providing the capacitor C23B, the capacitive coupling between the second resonator 22 and the third resonator 23 is weakened. The capacitive coupling between the second resonator 22 and the third resonator 23 is adjusted by the capacitor C23A. On the other hand, in the first embodiment, the capacitive coupling between the second resonator 22 and the third resonator 23 is adjusted by the capacitors C23A and C23B. According to this embodiment, compared with the first embodiment, the adjustment of the capacitive coupling between the second resonator 22 and the third resonator 23 becomes easier.

[0141] Next, with reference to FIGS. 33 to 38, an example of the characteristics of the bandpass filter 101 according to this embodiment will be described. Here, an example of the characteristics of the bandpass filter 101 when it is designed such that the passband of the bandpass filter 101 includes a frequency band of 4.7 GHz to 5.1 GHz is shown.

[0142] FIG. 33 shows an example of the pass characteristics of the bandpass filter 101. FIG. 34 shows an enlarged view of a part of FIG. 33. Here, the insertion loss when an unbalanced signal is input to the unbalanced port 11 is shown as the pass characteristics of the bandpass filter 101. In FIGS. 33 and 34, the horizontal axis represents the frequency, and the vertical axis represents the insertion loss. As shown in FIG. 33, in the bandpass filter 101, in each of the first vicinity region, which is a frequency region lower than the passband and close to the passband, and the second vicinity region, which is a frequency region higher than the passband and close to the passband, it can be seen that attenuation poles where the insertion loss changes steeply are formed.

[0143] Further, comparing FIG. 33 with FIG. 17 showing an example of the passing characteristics of the bandpass filter 1 according to the first embodiment, the following differences can be found. In the bandpass filter 101, the attenuation poles formed in the high-frequency side frequency region are farther from the passing band than in the bandpass filter 1. This is because the distance between the second resonator 22 and the third resonator 23 in the bandpass filter 101 is made larger than that in the bandpass filter 1, and while weakening the magnetic coupling between the second resonator 22 and the third resonator 23 compared to the bandpass filter 1, the capacitive coupling between the second resonator 22 and the third resonator 23 by the capacitors C23A and C23B is also made weaker than that in the bandpass filter 1. In other words, from FIGS. 17 and 33, by reducing the distance between the second resonator 22 and the third resonator 23 and strengthening the magnetic coupling between the second resonator 22 and the third resonator 23, while also strengthening the capacitive coupling between the second resonator 22 and the third resonator 23, the frequency of the attenuation pole formed in the vicinity of the second can be brought closer to the passing band.

[0144] Also, the insertion loss is preferably 3.0 dB or less. As shown in FIG. 34, in the bandpass filter 101, in the aforementioned frequency band, the insertion loss is 3.0 or less.

[0145] FIG. 35 shows an example of the amplitude balance characteristics of the bandpass filter 101. Here, the amplitude balance characteristics of the bandpass filter 101 are represented using the amplitude difference in the same manner as in FIG. 19 in the first embodiment. In FIG. 35, the horizontal axis represents the frequency, and the vertical axis represents the amplitude difference. When the amplitude difference is represented as m (dB), the value of m is preferably -1.5 or more and 1.5 or less, and more preferably -1.0 or more and 1.0 or less. As shown in FIG. 35, in the bandpass filter 101, in the aforementioned frequency band, the value of m is -1.0 or more and 1.0 or less.

[0146] FIG. 36 shows an example of the phase balance characteristics of the band-pass filter 101. Here, the phase balance characteristics of the band-pass filter 101 are represented using the phase difference, similar to FIG. 20 in the first embodiment. In FIG. 36, the horizontal axis represents the frequency, and the vertical axis represents the phase difference. When the amplitude difference is represented as p (deg), the value of p is preferably 165 or more and 195 or less. As shown in FIG. 35, in the band-pass filter 101, in the aforementioned frequency band, the value of p is 165 or more and 195 or less.

[0147] FIG. 37 shows an example of the reflection characteristics of the unbalanced port 11 of the band-pass filter 101. FIG. 38 shows an example of the reflection characteristics of the first and second balanced ports 12 and 13 of the band-pass filter 101. In FIGS. 37 and 38, the horizontal axis represents the frequency, and the vertical axis represents the reflection loss. The reflection loss is preferably 10 dB or more. As shown in FIGS. 37 and 38, in the band-pass filter 101, in the aforementioned frequency band, the reflection loss is 10 dB or more.

[0148] As described above, the band-pass filter 101 having the characteristics shown in FIGS. 33 to 38 can be used in at least the frequency band of 4.7 GHz to 5.1 GHz and has good balance characteristics in this frequency band. Also, as can be understood from FIGS. 33 to 38, according to this band-pass filter 101, while satisfying the balance characteristics, steep attenuation poles can be formed in each of the first and second neighboring regions.

[0149] Other configurations, operations, and effects in this embodiment are the same as those in the first embodiment.

[0150] [Third Embodiment] Next, a third embodiment of the present invention will be described. First, with reference to FIG. 39, the circuit configuration of the band-pass filter according to this embodiment will be described. FIG. 39 shows the circuit configuration of the band-pass filter according to this embodiment.

[0151] The circuit configuration of the band-pass filter 201 according to this embodiment is different from that of the band-pass filter 101 according to the second embodiment in the following points. In this embodiment, a capacitor C23A for connecting one end on the capacitor C2A side of the second resonator 22 and one end on the capacitor C3A side of the third resonator 23 is not provided.

[0152] Also, the band-pass filter 201 includes capacitors C5A and C5B. Each of the capacitors C5A and C5B has a first end and a second end. The first end of the capacitor C5A is connected to the capacitors C2A and C3A. The second end of the capacitor C5A is connected to the ground.

[0153] The first end of the capacitor C5B is connected to the capacitors C2B and C3B. The second end of the capacitor C5B is connected to the ground.

[0154] The other circuit configuration of the band-pass filter 201 is the same as the circuit configuration of the band-pass filter 101 according to the second embodiment.

[0155] In this embodiment, the set of capacitors C2A, C3A, and C5A and the set of capacitors C2B, C3B, and C5B are both connected in a so-called Y-type connection. According to this embodiment, compared with the case where these sets are connected in a so-called π-type connection or Δ-type connection, the capacitance of each of the capacitors C2A, C2B, C3A, C3B, C5A, and C5B can be reduced. As a result, according to this embodiment, the band-pass filter 201 can be miniaturized.

[0156] Other configurations, operations, and effects in this embodiment are the same as those in the second embodiment.

[0157] Note that the present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the band-pass filter of the present invention may be integrated with other circuits to form one multilayer electronic component. Examples of other circuits include a splitter circuit, a filter, a matching circuit, and the like.

Explanation of Reference Numerals

[0158] 1... balun, 11... unbalanced port, 12... first balanced port, 13... second balanced port, 21... first resonator, 22... second resonator, 23... third resonator, 24... fourth resonator, 30... laminate, 111... first terminal, 112... second terminal, 113... third terminal, 114... fourth terminal, 115... fifth terminal, 116... sixth terminal, 117... seventh terminal, 118... eighth terminal.

Claims

1. An unbalanced port; a first balanced port; a second balanced port; and A bandpass filter including a first resonator, a second resonator and a third resonator provided between the unbalanced port and the first and second balanced ports in terms of a circuit configuration, the second resonator and the third resonator are both open-ended resonators, adjacent to each other in a circuit configuration, and electromagnetically coupled with each other using magnetic coupling as a primary coupling; the second resonator and the third resonator are provided between the first resonator and the first and second balanced ports in terms of a circuit configuration; the first resonator is provided at a position closer to the second resonator than to the third resonator in terms of a circuit configuration; the first resonator includes a first resonator conductor layer; the second resonator includes a second resonator conductor layer; the third resonator includes a third resonator conductor layer; the second resonator conductor layer and the third resonator conductor layer are disposed with a predetermined gap therebetween, the first resonator conductor layer is disposed so as to sandwich the second resonator conductor layer between the first resonator conductor layer and the third resonator conductor layer such that the first resonator and the third resonator are cross-coupled; The bandpass filter further includes a first capacitor connected to one end of the second resonator; a second capacitor connected to one end of the third resonator; a third capacitor having a first end and a second end; the first end of the third capacitor is connected to the first and second capacitors; The second end of the third capacitor is connected to ground.

2. 2. The bandpass filter according to claim 1, wherein the first resonator is a one-end short-circuited resonator and is provided between the unbalanced port and the second resonator in terms of circuit configuration.

3. 3. The bandpass filter according to claim 1, wherein a distance between the second resonator and the third resonator is smaller than a distance between the first resonator and the second resonator.

4. a fourth resonator provided between the unbalanced port and the first and second balanced ports in terms of circuit configuration; the fourth resonator is provided at a position closer to the third resonator than the second resonator in terms of a circuit configuration; the fourth resonator includes a fourth resonator conductor layer; 2. The bandpass filter according to claim 1, wherein the fourth resonator conductor layer is disposed so as to sandwich the third resonator conductor layer between the fourth resonator conductor layer and the second resonator conductor layer, so that the second resonator and the fourth resonator are cross-coupled.

5. the first resonator is a one-end short-circuited resonator and is provided between the unbalanced port and the second resonator in terms of a circuit configuration; 5. The bandpass filter according to claim 4, wherein the fourth resonator is a resonator with both ends open, and is provided between the first and second balanced ports and the third resonator in terms of a circuit configuration.

6. 6. The bandpass filter according to claim 4, wherein a distance between the second resonator and the third resonator is smaller than a distance between the first resonator and the second resonator and is smaller than a distance between the third resonator and the fourth resonator.

7. 7. The bandpass filter according to claim 1, further comprising a laminate for integrating at least the second and third resonators, the laminate including a plurality of laminated dielectric layers and a plurality of laminated conductor layers, and a plurality of through holes.

8. the plurality of conductor layers include a plurality of resonator conductor layers, the plurality of through holes includes a plurality of resonator through holes, each of the second and third resonators includes a first row of through holes, a second row of through holes, and a conductor layer portion; each of the first and second through hole rows is configured by connecting two or more through holes of the plurality of resonator through holes in series, and penetrates two or more dielectric layers of the plurality of dielectric layers; 8. The bandpass filter according to claim 7, wherein the conductor layer portion is formed by one or more of the plurality of resonator conductor layers, and connects one end of the first row of through holes and one end of the second row of through holes.

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