JP4242738B2 - Multilayer bandpass filter - Google Patents

Description

  The present invention relates to a high-frequency multilayer bandpass filter having an attenuation pole, and in particular, a resonator electrode pattern having filter characteristics as an internal electrode inside a ceramic chip or a ceramic substrate, and an input / output electrode pattern connected to an input / output circuit. And a band-pass filter having a structure suitable for low profile (thinning).

  In recent years, for example, components used in wireless devices such as mobile phones and wireless LANs have made remarkable progress in miniaturization, high performance, and high functionality. Along with this trend, there is a strong demand for miniaturization, low profile (thinning) and high performance for bandpass filters used in these wireless devices. Ceramic multilayer high frequency bandpass filters However, there is an increasing demand for downsizing as well as downsizing. In addition, a high-frequency module that has a filter layered on a low-temperature fired ceramic substrate (LTCC substrate) and is miniaturized has been commercialized. In this case as well, a reduction in the height of the module itself is required.

As prior art of these ceramic multilayer bandpass filters, for example, those disclosed in the following patent documents are known.
Japanese Patent No. 3208967 Japanese Patent No. 3191560 JP 7-31503 A JP-A-8-316101

  However, in the case of the conventional ceramic multilayer bandpass filter having the structure shown in FIGS. 10 and 11, if the distance between the upper and lower shield layers is shortened to reduce the height, the magnetic coupling between the resonator electrode patterns is weak. Thus, there is a problem that it is difficult to bring the attenuation pole near the pass band close to the pass band frequency and increase the attenuation near the pass band.

  The present invention has been made in view of the above-described circumstances, and has a structure that can easily change the frequency of the attenuation pole, obtain good band-pass characteristics, and reduce the height (thinner). An object is to provide a small ceramic multilayer bandpass filter.

The multilayer bandpass filter of the present invention has a short-circuited end on one side and an open end on the other side in a filter or module substrate formed by laminating a plurality of dielectric sheets or insulating sheets on which conductor electrodes are formed. A strip-type bandpass filter in which two stripline-type resonator electrode patterns are disposed, wherein the short-circuited end of the stripline-type resonator electrode pattern is connected to a ground electrode on a side surface of the substrate; A strip extending from the side surface, bent in a right angle direction, further bent in a right angle direction toward the side surface of the substrate, forming the open end, and forming a band-shaped U-shaped magnetic field coupling electrode pattern into the two stripline type A layer in which the resonator electrode pattern is formed so as to extend from the side surface of the substrate of the resonator electrode pattern in a band shape and face a portion bent in a right angle direction. Was placed in a separate layer, both ends of the shaped magnetic field coupling electrode pattern of the co is characterized in that it is connected to a ground electrode to which the resonator electrode are short-circuited.

  Thereby, the distance between the magnetic field coupling electrode pattern and the resonator electrode pattern, that is, the thickness of the insulating layer between the magnetic field coupling electrode pattern and the resonator electrode pattern can be arbitrarily adjusted. The strength of magnetic field coupling can be arbitrarily adjusted. Therefore, the magnetic field coupling between both patterns can be easily strengthened, and sufficient magnetic field coupling strength can be obtained even when the height is lowered, the attenuation pole is brought close to the pass band, and the attenuation near the pass band is increased. Design becomes possible. That is, even when the height of the upper and lower shield layers is reduced to 1 mm or less, a ceramic multilayer bandpass filter having good attenuation characteristics and bandpass characteristics can be obtained.

  Here, the open end side of the resonator electrode pattern is a belt-like pattern folded back in a U-shape, and the short-circuit end side of the belt-like pattern is connected to the ground electrode. The resonator electrode pattern is preferably a stripline type suitable for miniaturization and height reduction, and the length of the resonator electrode pattern is determined by the resonance frequency, but the band-shaped resonator electrode pattern is folded back into a U-shape. As a result, the area occupied by the resonator can be reduced, and the size of the filter can be reduced.

  Further, the open end side of the resonator electrode pattern has a wider stepped impedance resonator (SIR) than the short-circuited end side of the resonator electrode pattern, and the resonator electrode pattern has this structure, so that the length of the resonator electrode pattern is increased. The length can be shortened to ¼ wavelength or less, and the size of the filter can be reduced.

  Further, the resonator electrode pattern and the input / output electrode pattern may be arranged in different layers and coupled by capacitive coupling. Further, the ceramic multilayer bandpass filter may be a single chip component or may be used as an electrode pattern that is layered on the high frequency module substrate.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to obtain a favorable filter characteristic, the small ceramic laminated type bandpass filter which has a low-profile structure is provided.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, in each figure, the same code | symbol is attached | subjected to the electrode or dielectric material sheet which has the same function, and the duplicate description is abbreviate | omitted.

  FIG. 1 is an external view of a ceramic multilayer bandpass filter according to an embodiment of the present invention. FIG. 2 is an exploded perspective view showing an example of internal electrode patterns arranged on each green sheet of the ceramic multilayer bandpass filter according to the first embodiment of the present invention, and FIG. 3 shows an electrode pattern of the main part thereof. FIG. 4 is a plan view showing the laminated state.

  As shown in these drawings, a plurality of green sheets S1, S2, S3, S4, S5... Are stacked, pressed, cut into chips, and fired to obtain a ceramic chip 5. Here, the ceramic green sheet becomes a sintered body of the ceramic layer, and the internal electrode paste pattern formed by printing becomes the metal internal electrode layer. Next, a base electrode is formed on the outer surface of the sintered rectangular parallelepiped ceramic chip 5 by printing or sputtering, and Ni plating and Sn plating are performed thereon. 1 and 2 and ground electrodes 3 and 4 are formed.

  As shown in FIGS. 2 and 3, the green sheets S1, S3, S5, S7, and S9 are blank layers on which no internal electrode pattern is formed. On the green sheets S2 and S8, for example, H-shaped shield electrode patterns P21 and P81 are formed by screen printing with a silver-based paste (for example, silver, silver-palladium, etc.) and become a shield layer after sintering. However, the shape of the shield electrode patterns P21 and P81 is not limited to the shape as long as it is a structure that covers the resonator electrode patterns P41 and P42 of the green sheet S4. The shield electrode patterns P21 and P81 extend to the ends of the green sheets S2 and S8 and are electrically connected to the ground electrodes 3 and 4 provided on the outer surface of the chip 5. Although not shown in the drawing, the interval (thickness) between the green sheets on which the internal electrode pattern is formed is laminated for a necessary number of blank sheet green sheets on which no internal electrode is formed, The thickness can be adjusted.

  A pair of resonator electrode patterns P41 and P42 are arranged in parallel on the green sheet S4 so that the open ends D and E face each other, and the other sides (short-circuit ends) C and F of the resonator electrode pattern are connected to the ground electrode 3. Has been. That is, the resonator electrode patterns P41 and P42 are band-shaped patterns whose open ends D and E are folded back in a U-shape, and the short-circuited strip lines having short-circuited ends C and F of the band-shaped pattern connected to the ground electrode 3. It becomes a resonator and is adjusted to a length of about a quarter wavelength (λ) in the passband frequency. Further, since these two resonators are arranged so that the open end sides D and E face each other, the coupling in the pass band is stronger in the electric field coupling than in the magnetic field coupling. One end of the input / output electrode patterns P41a and P42a is connected to the resonator electrode patterns P41 and P42, and the other end is connected to the input / output electrodes 1 and 2, respectively.

A U-shaped band-shaped magnetic field coupling electrode pattern P61 is disposed on the green sheet S6. The magnetic field coupling electrode pattern P61 is arranged in parallel on another green sheet S6 so as to face the center of the pair of resonator electrode patterns P41 and P42 of the green sheet S4. Both ends of the U-shaped magnetic field coupling electrode pattern P61 extend to the end of the chip and are electrically connected to the ground electrode 3. By changing the dimension a and the pattern width w of the magnetic field coupling electrode pattern P61 and the interval t between the resonator electrode patterns (see FIGS. 3 and 4), the coupling of the magnetic field coupling with the pair of resonator electrode patterns P41 and P42 is performed. You can change the degree.
The input / output electrode patterns P41a, P42a and the resonator electrode patterns P41, P42 (or at least the resonator electrode patterns P41, P42) are arranged between the upper and lower shield patterns P21, P81 in the longitudinal section (see FIG. 4). It is desirable to adjust or set the thicknesses of the green sheets S3, S5, and S7 so that they are positioned approximately in the middle of the distance.

  As shown in FIG. 4, the coupling degree of the magnetic field coupling between these patterns is greatly influenced by the interval t between the resonator electrode patterns P41 and P42 and the magnetic field coupling electrode pattern P61. The adjustment of the distance t can be performed by changing the number or thickness of the green sheets S5 inserted between the green sheets S4 and S6. Specifically, when the interval t is decreased, the magnetic field coupling between the resonator electrode pattern and the magnetic field coupling electrode pattern is increased. As a result, the magnetic field coupling between the pair of resonator electrodes is increased, and the attenuation pole frequency is increased. On the contrary, if the distance t is increased, the magnetic coupling between the pair of resonator electrodes is reduced as a result, and the attenuation pole frequency can be lowered.

  If the ceramic multilayer bandpass filter is lowered in height, the distance between the shield electrode patterns P21 and P61 is reduced, and the magnetic field coupling at the short-circuited portion of the resonator electrode patterns P41 and P42 is weakened. This makes it difficult to control the resonance frequency of the attenuation pole due to the capacitive coupling occurring between the open ends of the two resonator electrodes and the magnetic field coupling occurring between the short-circuit ends. However, in the case of this embodiment, even if the height is lowered, the distance t between the magnetic field coupling electrode pattern P61 and the resonator electrode patterns P41 and P42 provided in a layer different from the resonator electrode patterns P41 and P42 can be easily reduced. Since the magnetic field coupling can be strengthened, the attenuation pole frequency can be made closer to the pass band and the attenuation in the vicinity of the pass band can be increased. For this reason, even if the height is reduced due to the presence of the magnetic field coupling electrode pattern P61, it is easy to bring the attenuation pole generated on the lower side of the pass band due to the magnetic field coupling and the electrostatic coupling closer to the pass band. Accordingly, it is possible to realize a bandpass filter having a good bandpass characteristic having a steep attenuation characteristic on the low band side of the passband.

  FIG. 5 shows an example of internal electrode patterns arranged on each green sheet of the multilayer bandpass filter according to the second embodiment of the present invention. In this embodiment, the input / output electrode pattern is formed on a layer different from the layer on which the resonator electrode pattern is formed. That is, input / output electrode patterns P541 and P542 are formed on the green sheet S54, and a pair of open ends of the input / output electrode patterns P541 and P542 are formed on the green sheet S55. It arrange | positions facing the open end of P551, P552, and both are capacitively coupled.

  The other points are the same between the second embodiment and the first embodiment. That is, the pair of U-shaped resonator electrode patterns P551 and P552 on the green sheet S55 are formed in parallel so that the pair of open ends face each other. A U-shaped magnetic field coupling electrode pattern P571 is formed on the green sheet S57 so as to face the center of the pair of resonator electrode patterns P551 and P552 of the green sheet S55. Both ends of the magnetic field coupling electrode pattern P571 extend to the end of the green sheet S57 and are electrically connected to the ground electrode 3. Here, the thicknesses of the green sheets S53, S56, and S58 are set so that the resonator electrode patterns P551 and P552 are located approximately in the middle of the distance between the upper and lower shield electrode patterns P521 and P591 in the longitudinal sectional view. It is desirable to adjust or set and arrange. For this reason, even if the height is lowered, it is easy to bring the attenuation pole generated on the low band side of the pass band due to magnetic field coupling and capacitive coupling between the resonator electrodes closer to the pass band, and steep attenuation on the low band side of the pass band. The same is true in that a bandpass filter having good bandpass characteristics having characteristics can be realized.

  FIG. 6 is an exploded perspective view showing an example of internal electrode patterns arranged on each green sheet of the ceramic multilayer bandpass filter according to the third embodiment of the present invention. The third embodiment of the present invention is a band-pass filter using an SIR (Stepped Impedance Resonator) type resonator, and FIG. 7A is a plan view showing an electrode pattern of the main part, FIG. ) Is a cross-sectional view showing the laminated state.

  The green sheets S61, S63, S65, S67, and S69 are blank layers on which no internal electrode pattern is formed. On the green sheets S62 and S68, shield electrode patterns P621 and P681 are formed by screen printing of a silver-based or copper-based thick film paste to form a shield layer. Input / output electrode patterns P641a and P642a and resonator electrode patterns P641 and P642 are formed on the green sheet S64. The resonator electrode patterns P641 and P642 are cascaded with first transmission line patterns P641b and P642b having a narrow and high characteristic impedance and second transmission line patterns P641c and P642c having a wider and lower characteristic impedance than the first transmission line pattern, respectively. Is. The total line length is adjusted so as to resonate near the center frequency of the multilayer bandpass filter, and the short-circuit ends I and L at one end thereof are exposed to the end surface on the chip side and connected to the ground electrode 3. The other ends J and K are wide open ends, and the open ends J and K are arranged to face each other to form a pair of resonator electrode patterns. A U-shaped band-shaped magnetic field coupling electrode pattern P661 is disposed on a green sheet S66 which is a separate layer so as to face the central portion of each of the resonator electrode patterns P641 and P642.

  FIG. 8A shows an equivalent circuit of the ceramic multilayer bandpass filter according to the first to third embodiments of the present invention. Cp represents the distributed capacitance of the resonator electrode pattern as a lumped constant capacitance, and Lp represents the distributed inductance of the resonator electrode pattern as a lumped constant inductance. The length of the resonator electrode is adjusted so as to resonate near the center frequency of the passband, and Cp and Lp constitute the resonance circuit. Cm represents an equivalent capacitance generated by electric field coupling caused by the open ends of a pair of resonator electrodes facing each other, and M represents magnetic field coupling between the resonator electrode and the magnetic field coupling electrode by a lumped constant inductance. is there. An attenuation pole is generated outside the passband by M due to magnetic field coupling and Cm due to electric field coupling, and the frequency of the attenuation pole is determined by M and Cm. Here, the input / output electrodes are taken out from the middle of the equivalent inductance Lp. However, in the case of the second embodiment, the input / output is capacitive coupling.

  FIG. 8B shows an equivalent circuit of the conventional ceramic multilayer bandpass filter shown in FIGS. Cp represents the distributed capacitance of the resonator electrode pattern as a lumped constant capacitance, and Lp represents the distributed inductance of the resonator electrode pattern as a lumped constant inductance. The length of the resonator electrode is adjusted so as to resonate near the center frequency of the passband, and Cp and Lp constitute the resonance circuit. Cm represents an equivalent capacitance generated by electric field coupling caused by the open ends of the pair of resonator electrodes facing each other, and M represents magnetic field coupling between the pair of resonator electrodes as a lumped constant inductance. An attenuation pole is generated outside the passband by M due to magnetic field coupling and Cm due to electric field coupling, and the frequency of the attenuation pole is determined by M and Cm.

  In this band-pass filter, the resonator electrode pattern is set so that the capacitive coupling generated at the open ends J and K of the resonator electrode pattern is stronger than the magnetic coupling generated at the short-circuit sides I and L at a frequency near the pass band. It is arranged. As a result, coupling in the pass band becomes capacitive, and an attenuation pole is formed by magnetic coupling and capacitive coupling on the lower side of the pass band. The degree of coupling between the two resonator electrode patterns is determined by the distance between open ends d32 and the distance between short ends d31 (see FIG. 7). When the distance d32 is narrowed, the capacitive coupling is strengthened, and when the distance d31 is narrowed, the magnetic field coupling M is strengthened. The degree of coupling is almost determined by the difference between the degree of capacitive coupling and the degree of magnetic field coupling. The input / output impedance matching of the filter is substantially determined by the position b3 of the input / output extraction electrode from the resonator electrode pattern. Further, an attenuation pole is generated outside the pass band by the magnetic field coupling M and the electrostatic coupling Cm, and the frequency of the attenuation pole is substantially determined by the relational expression of the magnetic field coupling M and the electrostatic coupling Cm.

  As described above, when the coupling of the passband is capacitive, an attenuation pole is formed on the lower side of the passband, and the attenuation pole frequency is adjusted by adjusting the strength of the magnetic coupling and electrostatic coupling, The attenuation near the passband can be increased to obtain excellent attenuation characteristics. In order to increase the attenuation in the vicinity of the pass band, it is necessary to increase the magnetic field coupling in order to bring the attenuation pole close to the vicinity of the pass band. Therefore, in the conventional technique, the distance f between the resonator electrodes in FIG. Don't be. However, if the distance between the upper and lower shield electrodes is shortened in order to reduce the height, the magnetic field becomes extremely weak, and the distance f needs to be considerably reduced, which is limited by the limit of the manufacturing process.

  In the present invention, a magnetic field coupling electrode is added to a layer separate from the resonator electrode pattern, and a magnetic field coupling electrode pattern P661 is formed on the green sheet S66. The magnetic field coupling electrode pattern has a U-shape, and is formed at a position facing the center of the two resonator electrode patterns P641 and P642 as shown in FIG. Further, both ends of the magnetic field coupling electrode pattern P661 are exposed at the end of the chip and are connected to the ground electrode 3. As shown in FIG. 7, the line width w3 of the magnetic field coupling electrode pattern P661 is narrower than the widths of the resonator electrode patterns P641 and P642. This is to suppress a change in filter characteristics due to stacking deviation. It is.

  In the band-pass filter of FIG. 6, the resonator electrode pattern is arranged so that the electrostatic coupling generated on the open end side of the resonator electrode is stronger than the magnetic field coupling generated on the short-circuit side at a frequency near the pass band. . Thereby, the coupling in the passband is capacitive, and an attenuation pole is formed by the magnetic coupling M and the capacitive (electric field) coupling Cm on the lower side of the passband.

  Next, a method for adjusting the magnetic field coupling M and the electric field coupling Cm in the band-pass filter of the present invention will be described. The electric field coupling Cm is adjusted by changing the distance d32 (FIG. 7) between the open ends of the resonator electrode pattern as in the conventional band pass filter. If the distance d32 is reduced, the electric field coupling becomes stronger, and conversely, if the distance d32 is increased, it becomes weaker. Furthermore, although not shown in the figure when strengthening electric field coupling, a capacitive coupling electrode pattern may be provided in a separate layer so as to face the open end electrode surface of the resonator electrode pattern.

  The magnetic field coupling M is adjusted by changing the interlayer distance t3 (FIG. 7B) between the magnetic field coupling electrode pattern P661 and the resonator electrode patterns P641 and P642. If t3 is decreased, the magnetic field coupling is increased, and if t3 is increased, it is decreased. The adjustment of the magnetic field coupling M is a point that is greatly different from that of the conventional band pass filter, and is a feature of the band pass filter of the present invention. That is, the magnetic field coupling electrode pattern is provided in a layer different from the resonator electrode pattern, and the interlayer distance t3 is adjusted. With this configuration, even if the distance between the shield electrodes is shortened due to the low profile, the magnetic field coupling can be strengthened by adjusting t3. Therefore, the magnetic field coupling M and the electrostatic coupling Cm are generated. It becomes easy to bring the low-frequency attenuation pole close to the vicinity of the passband, and a bandpass filter having excellent low-frequency attenuation characteristics can be designed even if the height is lowered.

  FIG. 9A shows a characteristic comparison between the bandpass filter of the present invention and the conventional bandpass filter. The heights of both bandpass filters and the distance between the shield electrodes are the same. As can be seen from the figure, in the bandpass filter of the present invention, the attenuation pole is close to the vicinity of the passband, and the attenuation characteristic near the passband is excellent. Furthermore, when trying to reduce the height, it is difficult for the conventional type to further increase the attenuation near the pass band because the attenuation pole is further away from the pass band. By adjusting t3, it is possible to easily bring the attenuation pole frequency closer to the pass band.

  Regarding the multilayer bandpass filter according to the first embodiment of the present invention, three types of green sheets (t = 270 μm, 320 μm, 420 μm) having different thicknesses are used as the green sheet S5, and the resonance is achieved by changing the interlayer distance t. FIG. 9B shows transmission characteristics by electromagnetic field simulation when the degree of coupling of the magnetic field coupling M between the electrode patterns P41 and P42 and the magnetic field coupling electrode pattern P61 is changed. According to this result, it can be seen that when the interlayer distance t decreases, the attenuation pole frequency approaches the frequency in the pass band, and the frequency characteristics in the vicinity of the pass band are improved.

  Although three embodiments of the ceramic multilayer bandpass filter as described above have been shown, the present invention is not limited to the above-described embodiments. For example, a high-frequency filter in which a multilayer filter is formed on a low-temperature fired ceramic substrate. It can also be applied to modules. Thus, it goes without saying that various modified embodiments are possible without departing from the spirit of the present invention.

It is an external view of a ceramic multilayer bandpass filter. It is a disassembled perspective view which shows the example of an internal electrode pattern arrange | positioned at each green sheet of the ceramic multilayer type bandpass filter which is 1st Example of this invention. It is a top view which shows the relative position of a magnetic field coupling electrode pattern with respect to the resonator electrode pattern and input / output electrode pattern of the ceramic multilayer bandpass filter which is 1st Example of this invention. It is sectional drawing by the AA line shown in FIG. 3 of the ceramic multilayer type bandpass filter which is 1st Example of this invention. It is a disassembled perspective view which shows the example of an internal electrode pattern arrange | positioned at each green sheet of the ceramic multilayer type bandpass filter which is 2nd Example of this invention. It is a disassembled perspective view which shows the example of an internal electrode pattern arrange | positioned at each green sheet of the ceramic multilayer type bandpass filter which is 3rd Example of this invention. FIG. 7A is a plan view showing a relative position of a magnetic field coupling electrode pattern with respect to a resonator electrode pattern and an input / output electrode pattern of a ceramic multilayer bandpass filter according to a third embodiment of the present invention, and FIG. It is sectional drawing by the HH line | wire shown in FIG. It is the equivalent circuit schematic of the ceramic laminated type bandpass filter of (a) 1st Example and (b) conventional example of this invention. It is the transmission characteristic figure of the ceramic multilayer type bandpass filter of the 1st example of the present invention and the conventional example, (a) is the transmission characteristic (dotted line) of the 1st example, and the transmission characteristic (solid line) of the conventional example, (B) shows the transmission characteristics when the thickness of the green sheet is changed with respect to the first embodiment of the present invention. It is a disassembled perspective view which shows the example of an internal electrode pattern arrange | positioned at each green sheet of a prior art example. It is a top view which shows the resonator electrode pattern and input / output electrode pattern of a prior art example.

Explanation of symbols

1, 2 I / O electrodes 3, 4 Ground electrode 5 Ceramic chips S1 to S9, S51 to S60, S61 to S69 Green sheets S101 to S107 Green sheets P21, P81, P521, P591, P621, P681 Shield pattern P1021, P1061 Shield pattern P41, P42, P551, P552 Resonator electrode patterns P641, P642, P1041, P1042 Resonator electrode patterns P41a, P42a, P541, P542 I / O electrode patterns P641a, P642a, P1041a, P1042a I / O electrode patterns P61, P571, P661 Combined electrode pattern

Claims (7)

Two stripline resonators having a short-circuited end on one side and an open end on the other in a filter or module substrate formed by laminating a plurality of dielectric sheets or insulator sheets on which conductor electrodes are formed A laminated bandpass filter in which an electrode pattern is arranged,
The stripline resonator electrode pattern has the short-circuited end connected to the ground electrode on the substrate side surface, extends from the substrate side surface in a strip shape, bends in a right angle direction, and further bends in a right angle direction toward the substrate side surface, Forming an open end,
The resonator electrode pattern is formed such that a band-like U-shaped magnetic field coupling electrode pattern extends from the side surface of the substrate of the two stripline resonator electrode patterns in a band shape and faces a portion bent in a right angle direction. Placed in a layer separate from the layer where
A laminated bandpass filter, wherein both ends of the U-shaped magnetic field coupling electrode pattern are connected to a ground electrode in which the resonator electrode is short-circuited .   The multilayer bandpass filter according to claim 1, wherein the distance between the stripline resonator electrode pattern and the upper and lower shield electrodes is a low profile of 1 mm or less.   2. The stacked type according to claim 1, wherein in the band-pass filter, the resonator electrode pattern is U-shaped, and the U-shaped resonator electrode pattern is disposed so that open end sides thereof face each other. Bandpass filter.   2. The band pass filter according to claim 1, wherein an open end side of the resonator electrode pattern is a wide SIR (stepped Impedance Resonator) with respect to a short-circuit end side of the resonator electrode pattern. Multilayer bandpass filter.   5. The multilayer bandpass filter according to claim 1, wherein an input / output electrode pattern is taken out from the middle of the resonator electrode pattern.   The input / output electrode pattern is formed in a layer different from the resonator electrode so as to face a part of the resonator electrode pattern, and is taken out by capacitive coupling. 4. The laminated bandpass filter according to 4.   A width of the band-shaped U-shaped magnetic field coupling electrode pattern is narrower than a width of the stripline resonator electrode pattern and is disposed within a range of the width of the stripline resonator electrode pattern. The multilayer bandpass filter according to claim 1.

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