JP2012175438A - Notch filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the deterioration of characteristics in an attenuation region, in regard to a notch filter having a series arm composed of an inductor for phase inversion and a parallel arm composed of an element portion which produces series resonance at a frequency corresponding to the attenuation region, even in the case that the series arm and the parallel arm are mounted on a board.SOLUTION: An inductor 11 and a SAW resonator 12 (piezoelectric substrate 4) are disposed on a package board 5 in which a conductive path 34 is formed in an internal region thereof. Through the conductive path 34, the SAW resonator 12 is grounded. A resonant circuit 21 is configured by the connection of a capacitance component 37, having a set capacitance value, between the SAW resonator 12 and a grounding port 3, so that the series resonance is produced between with the inductor component of the conductive path 34 at a frequency corresponding to the attenuation region.

Description

  The present invention relates to a notch filter using, for example, SAW (surface acoustic wave).

  As one of filters using SAW (surface acoustic wave) or the like, as shown in FIG. 24, a part of the frequency band (attenuation area) is attenuated, and the higher frequency side than the attenuation area and 2. Description of the Related Art Notch filters (band elimination filters) that each form a pass band on the low frequency side are known. As shown in FIG. 25, this filter is configured by arranging a plurality of, for example, three inductors 101 in series, and connecting SAW resonators 102 between the inductors 101 and 101 in parallel. Then, by shifting the series resonance frequency (resonance point) of these SAW resonators 102 in the attenuation region, the attenuation region is formed over as wide a band as possible, and a large amount of attenuation is provided over the band. I try to get it. Each SAW resonator 102 is grounded. In FIG. 25, 110 is an input port, and 111 is an output port.

  As shown in FIG. 26, each SAW resonator 102 is arranged on a substrate 104 such as alumina (Al2O3) in a state of being patterned on a piezoelectric substrate 103 such as lithium tantalate (LiTaO3). The inductor 101 is disposed on the substrate 104 as an external coil, for example. Each SAW resonator 102 is connected as shown in FIG. 25 through the electrode 106 routed on the substrate 104 and embedded in a through-hole 107 penetrating the substrate 104 vertically. The ground electrode 112 is grounded via the other electrode. In FIG. 26, 108 is a bump that connects the SAW resonator 102 and the electrode of the through hole 107, and 109 is a case body that covers the substrate 104.

Here, when the frequency characteristic is evaluated by mounting the above-described piezoelectric substrate 103 and the inductor 101 on which the SAW resonator 102 is patterned on the substrate 104, compared with the case where the evaluation is performed without arranging the SAW resonator 102 on the substrate 104, The amount of attenuation in the attenuation region will deteriorate. That is, since the conductive path until each SAW resonator 102 is grounded, for example, the electrode in the through-hole 107 has a distributed constant component 120 such as inductance, as shown in the lower side of FIG. The resonance points of the SAW resonator 102 are coupled to each other, for example, and the attenuation is deteriorated (the attenuation is reduced).
Patent Document 1 describes that an inductance La is generated between the acoustic wave resonator P and the ground potential, and that the acoustic wave resonator P14 is capacitive in the pass band. Is not touched.

International Publication No. WO2007 / 015331

  It is an object of the present invention to provide a notch filter having a series arm composed of an inductor for phase inversion and a parallel arm composed of an element part that causes series resonance at a frequency corresponding to an attenuation region, when the parallel arm is mounted on a substrate. Even so, it is an object of the present invention to provide a filter that can suppress deterioration of characteristics in the attenuation region.

The notch filter of the present invention is
In the notch filter for providing an attenuation band between the pass bands formed on the low band side and the high band side,
A plurality of phase inversion inductors connected in series as a series arm between the input port and the output port;
An insulating plate;
A first electrode portion formed on one surface side and the other surface side of the insulating plate, respectively, and a second electrode portion forming a ground port;
A conductive path formed inside the insulating plate to connect the first electrode portion and the second electrode portion to each other;
A plurality of parallel arms, each having one end connected between the series arms adjacent to each other and having the other end connected to the first electrode portion, causing series resonance at a frequency corresponding to the attenuation region. Element part of
A capacitance component provided between the element portion and the second electrode portion, the capacitance value of which is set so that series resonance occurs with the inductor component of the conductive path at a frequency corresponding to the attenuation region; , Provided.

A second auxiliary electrode portion that is provided adjacent to the first electrode portion and the second electrode portion on one surface side and the other surface side of the insulating plate, respectively, and forms a first auxiliary electrode portion and an auxiliary ground port. When,
An auxiliary conductive path formed inside the insulating plate to connect the first auxiliary electrode part and the second auxiliary electrode part to each other;
A parallel signal path for connecting the other end side of the element part and the first auxiliary electrode part to each other;
The capacitance component is provided between the element portion and the second electrode portion, and the capacitance value is set so that series resonance occurs with the inductor component of the conductive path at a frequency corresponding to the attenuation region. Instead of being provided, it is provided between the element part and the second auxiliary electrode part so that parallel resonance occurs with the inductor component of the conductive path at a frequency outside the attenuation region. A capacitance value may be set in the.

The separation distance between the conductive path and the auxiliary conductive path may be 600 μm or less.
The capacitive component is a laminated film in which a dielectric layer is interposed between two metal layers, and one of these metal layers may be connected to the element portion side, in which case The element unit may be a SAW resonator formed on a piezoelectric substrate, and the capacitance component may be disposed on the piezoelectric substrate.

The series arm is an element portion that causes parallel resonance at a frequency corresponding to the attenuation region, instead of an inductor for phase inversion,
The parallel arm may be an inductor for phase inversion instead of an element portion that causes series resonance at a frequency corresponding to the attenuation region.
The capacitance component has a capacitance value set so that series resonance occurs with the inductor component of the conductive path, and the inductor component and the series resonance between the element portion and the second electrode portion. A capacitance value may be set to occur.
The capacitance component has a capacitance value set so that parallel resonance with the inductor component of the conductive path occurs, and the inductor component and parallel resonance between the element portion and the second electrode portion A capacitance value may be set to occur.

  The present invention relates to a notch filter having a series arm composed of an inductor for phase inversion and a parallel arm composed of an element portion that causes series resonance at a frequency corresponding to the attenuation region, and an insulating plate having a conductive path formed in the internal region. The parallel arm is arranged on the top, and the parallel arm is grounded to the ground port through the conductive path. A capacitance component having a capacitance value is interposed between the ground port and the parallel arm so that series resonance occurs with the inductor component of the conductive path at a frequency corresponding to the attenuation region. Therefore, even when the parallel arm is mounted on the insulating plate, the inductor component of the conductive path is apparently suppressed in the attenuation region, or the influence of the inductor component is eliminated, so that each of the parallel arms is formed. Coupling between the poles of the resonance point can be suppressed, and therefore a notch filter having a good attenuation amount and attenuation width in the attenuation region can be obtained. In another aspect of the invention, an auxiliary conductive path is formed in the insulating plate so as to be adjacent to the conductive path, and the auxiliary arm is connected between the auxiliary ground port of the auxiliary conductive path and the parallel arm connected to the auxiliary ground port. Since a capacitance component with a capacitance value is connected so that parallel resonance occurs with the inductor component of the conductive path in a frequency band outside the attenuation region, a notch filter with a good attenuation amount and attenuation width in the attenuation region is connected. Obtainable.

It is a circuit diagram which shows the notch filter in the 1st Embodiment of this invention. It is a perspective view which shows the external appearance of the said filter. It is a top view which shows the piezoelectric substrate mounted on the said filter. It is a longitudinal cross-sectional view which shows the said filter. It is a longitudinal cross-sectional view which expands and shows a part of said filter. It is a perspective view which expands and partially shows the piezoelectric substrate in the said filter. It is a characteristic view which shows the characteristic obtained by simulation about the conventional filter. It is a characteristic view which shows the characteristic obtained by simulation about the filter of this invention. It is a characteristic view which shows the characteristic obtained by simulation about the filter of this invention. It is a partially expanded longitudinal cross-sectional view which shows the other example of the said filter. It is a circuit diagram which shows the notch filter in the 2nd Embodiment of this invention. It is a top view which shows the piezoelectric substrate mounted on the said filter. It is a longitudinal cross-sectional view which shows the said filter. It is a longitudinal cross-sectional view which expands and shows a part of said filter. It is a characteristic view which shows the result of having simulated about the notch filter of this invention. It is a characteristic view which shows the result of having performed simulation about the conventional notch filter. It is a characteristic view which shows the result of having performed simulation about a notch filter. It is a characteristic view which shows the result of having performed simulation about a notch filter. It is a characteristic view which shows the result of having performed simulation about a notch filter. It is a characteristic view which shows the result of having performed simulation about a notch filter. It is a characteristic view which shows the result of having performed simulation about a notch filter. It is a characteristic view which shows the result of having performed simulation about a notch filter. It is a circuit diagram which shows the other example of the said filter. It is a schematic diagram which shows the frequency characteristic of the conventional filter. It is a circuit diagram which shows the conventional filter. It is a longitudinal cross-sectional view which shows the general appearance of the conventional filter.

[First Embodiment: Series Resonance]
An example of the notch filter according to the first embodiment of the present invention will be described with reference to FIGS. This notch filter is a filter in which a part of the frequency band, in this example, 800 MHz to 880 MHz is set as an attenuation band, and a pass band is arranged on the low frequency side and the high frequency side of the attenuation band, as shown in FIG. As described above, the circuit configuration is such that the inductor 11 for phase inversion which is a series arm and the element portion which is a parallel arm, in this example, the SAW resonator 12 are connected in a ladder form. That is, a plurality of, for example, three inductors 11 are connected in series between the input port 1 and the output port 2, and the SAW resonator 12 is connected between the adjacent inductors 11 and 11 and between the inductor 11 and the ports 1 and 2. One end side of each is connected in parallel. The other end sides of these SAW resonators 12 are connected in parallel to each other via a parallel signal path 12 a and also connected to the ground port 3. In this example, two ground ports 3 are provided in parallel to each other on the parallel signal path 12a. Between each ground port 3 and the parallel signal path 12a, as will be described in detail later, a series resonance circuit 21 that causes series resonance at a frequency corresponding to the above-described attenuation region is interposed. That is, in the series resonance circuit 21, the series resonance frequency (resonance point) is set to a frequency in the attenuation region, for example, 840 MHz.

  Next, an overview of the notch filter will be described with reference to FIG. This notch filter is disposed on a package substrate 5 which is a common insulating plate made of alumina (Al 2 O 3), for example, and includes the above-described inductor 11 provided as a component such as a coil and the back surface side (package substrate). 5) and a piezoelectric substrate 4 made of, for example, lithium tantalate (LiTaO3), on which four SAW resonators 12 are patterned. On the package substrate 5, a substantially box-shaped lid 6 having an opening on the lower side is provided so as to cover the inductor 11 and the piezoelectric substrate 4 from the upper side. In FIG. 2, the outline of the lid 6 is indicated by a one-dot chain line, and a part of the piezoelectric substrate 4 is notched and drawn. Further, a conductive line 31 for connecting the inductor 11 and the SAW resonator 12 (piezoelectric substrate 4) is formed on the package substrate 5. A part of the conductive line 31 is omitted in FIG. The arrangement layout of the inductor 11 and the conductive line 31 is schematically shown.

  Next, the arrangement layout of the SAW resonator 12 on the piezoelectric substrate 4 will be described. As shown in FIG. 3, the piezoelectric substrate 4 has a direction perpendicular to the propagation direction of the elastic wave (left and right direction in FIG. 3). The four SAW resonators 12 are spaced apart from each other. The SAW resonator 12 and the SAW resonator 12 are arranged on the near side and the far side in the propagation direction of the elastic wave (front-rear direction in FIG. 3) so that the electric circuit shown in FIG. In order to connect the inductor 11 and each of the ports 1, 2, and 3 to each other, a plurality of, for example, four metal films 13 each having a substantially rectangular shape are disposed.

  That is, on the front side of the piezoelectric substrate 4, the metal film 13 connected to the input port 1 from the left side to the right side, the first inductor 11 from the input port 1 side and the second inductor from the input port 1 side 11 and two metal films 13 and 13 connected to the ground port 3 are arranged in this order. The metal films 13 and 13 connected to the ground port 3 will be described in detail later, but when viewed in plan, the two metal films 13 and 13 are arranged side by side. The SAW resonator 12 and the ground port 3 are connected in series with each other via a side region. With respect to these two metal films 13 and 13 connected to the ground port 3, the metal film 13 on the ground port 3 side is denoted by “13 a” and the metal film 13 on the SAW resonator 12 side is denoted by “13 b”. The film 13a is disposed in the end region of the piezoelectric substrate 4, and the metal film 13b is disposed at a position closer to the input port 1 side than the metal film 13a.

  On the back side of the piezoelectric substrate 4, from the left side to the right side, metal films 13 a and 13 b connected to the ground port 3, the first inductor 11 from the output port 2 side, and the second from the output port 2 side A metal film 13 connecting the inductor 11 to each other and a metal film 13 connected to the output port 2 are arranged in this order. 3 includes a plurality of electrode fingers 14a arranged so as to intersect with each other in a comb-tooth shape, and a pair of bus bars 14b connected to one end side of the electrode fingers 14a and arranged in parallel to each other. IDT (Inter Digital Transducer) electrode. Reference numeral 15 denotes a reflector disposed on both sides of the IDT electrode 14 in the propagation direction of the elastic wave. FIG. 3 shows a state in which the piezoelectric substrate 4 in FIG. 2 described above is viewed from the back surface side (package substrate 5 side).

  The SAW resonator 12 and the metal film 13 are connected via the routing electrode 16 so as to form the circuit shown in FIG. That is, with respect to the four SAW resonators 12 in FIG. 3, from the left to the right, “first SAW resonator 12”, “second SAW resonator 12”, “third SAW resonator 12” and “ When the left side of the pair of bus bars 14b, 14b of the IDT electrode 14 is called the first bus bar 14b and the right side is called the second bus bar 14b, the left end of the front side in FIG. The routing electrode 16 extending from the metal film 13 connected to the input port 1 is connected to the second bus bar 14 b in the first SAW resonator 12. The first bus bar 14b in the first SAW resonator 12 passes through the lateral region of the first SAW resonator 12 to the inner side of the piezoelectric substrate 4 via the routing electrode 16, and reaches the metal film 13b. It is connected.

  The first bus bar 14 b of the second SAW resonator 12 connects the first inductor 11 from the input port 1 side and the second inductor 11 from the input port 1 side on the front side of the piezoelectric substrate 4. It is connected to the metal film 13 through the lead electrode 16. The second bus bar 14 b in the second SAW resonator 12 is connected to the first bus bar 14 b in the third SAW resonator 12 through the routing electrode 16, and the back side and the front side of the piezoelectric substrate 4. On the side, they are connected to the metal films 13b and 13b, respectively. The second bus bar 14 b in the third SAW resonator 12 is connected to the first inductor 11 from the output port side and the second inductor from the output port 2 side on the back side of the piezoelectric substrate 4 via the routing electrode 16. 11 is connected to the metal film 13 between them. In the fourth SAW resonator 12, the first bus bar 14b is connected to the metal film 13 directed to the output port 2 in the inner region of the piezoelectric substrate 4 through the routing electrode 16, and the second bus bar 14b. Is connected to the metal film 13 b on the front side of the piezoelectric substrate 4. In FIG. 3, the SAW resonator 12, the metal film 13, and the routing electrode 16 are hatched to distinguish them from the region on the piezoelectric substrate 4, and the inductor 11 is schematically shown.

  As shown in FIG. 4, the surface of the piezoelectric substrate 4 on which the SAW resonator 12 and the metal film 13 are formed is brought into contact with the package substrate 5 side, and as shown in FIG. The conductive line 31 formed on the substrate 5 is connected to the respective metal films 13 and 13a via bumps 32 having a diameter of about 200 μm, for example. With this conductive line 31, the inductor 11 and the SAW resonator 12 are connected on the package substrate 5 as described above. The package substrate 5 has a through-hole (via hole) 33 penetrating vertically at a position away from the bump 32 connected to the metal film 13a laterally. A metal body such as copper (Cu) is embedded in the through hole 33 as a conductive path 34, and the first electrode portion on the upper end side of the conductive path 34 is interposed via the conductive line 31 and the bump 32. Are connected to the metal film 13a, and the lower end side forms the above-described ground port (second electrode portion) 3. The conductive path 34 has a diameter dimension (width dimension) and a height dimension of, for example, 150 μm and 100 μm, respectively. Therefore, as shown in FIG. 1 described above, a distributed constant component 38 including an inductor component, a resistance component, etc. have. The bump 32, the routing electrode 16, and the metal films 13a and 13b between the ground port 3 and the SAW resonator 12 connected to the ground port 3 correspond to the parallel signal path 12a described above. FIG. 4 schematically shows the metal film 13a. Further, although the ground port 3 made of a metal film is formed on the lower surface side of the package substrate 5 so as to cover the lower side of the conductive path 34, when the metal film is not provided, the lower end portion of the conductive path 34 is grounded. Configure port 3.

Next, the metal films 13a and 13b and the connection part between the metal film 13a and the bump 32 will be described in detail. FIG. 5 is an enlarged view of a connecting portion between the metal film 13a and the bump 32. Between the metal film 13b and the piezoelectric substrate 4, a dielectric layer 35 made of, for example, SiO2 (silicon dioxide) is shown. And the metal layer 36 are laminated in this order from the metal film 13b side to the piezoelectric substrate 4 side. The dielectric layer 35 is bent at a right angle toward the piezoelectric substrate 4 so that the side wall portion on the metal film 13 a side covers the side surface of the metal layer 36, and the metal films 13 a and 13 b and the metal layer 36 are bent. Are connected via the dielectric layer 35, that is, the metal films 13a and 13b and the metal layer 36 are not in direct contact with each other. Therefore, the metal film 13b, the dielectric layer 35, and the metal layer 36 form a capacitance component 37 composed of a capacitor, and are interposed between the parallel signal path 12a and the metal film 13a. The capacitance component 37 has the thickness, surface area, and relative dielectric constant (material of the dielectric layer 35) of the dielectric layer 35 such that the capacitance value is about 450 pF to 50,000 pF, for example, about 850 pF. In this example, the film thickness, surface area, and relative dielectric constant (material of the dielectric layer 35) of the dielectric layer 35 are 50 nm, 490000 μm ² (700 μm × 700 μm), and ε _r = 10, respectively.

  Here, an example of a method of forming the capacitance component 37 will be described with reference to FIG. First, the SAW resonator 12, the routing electrode 16, and the metal layer 36 are formed on the piezoelectric substrate 4 by a photoresist method. Next, a thin film made of a dielectric (not shown) is laminated on the piezoelectric substrate 4, and the dielectric thin film other than the upper side of the metal layer 36 and the side wall portion of the metal layer 36 on the metal film 13a side is similarly removed by a photoresist method. . Then, a metal film 13 (metal films 13a and 13b) is formed on the piezoelectric substrate 4 by a photoresist method. In this way, the capacitance component 37 is formed so as to have the above-described capacitance value. In FIG. 6, the thickness dimension of the capacitive component 37 is schematically drawn (thicker than the actual thickness), but the metal layers 13 a and 13 b are formed as the metal layers 36 and the dielectric layers 35 are extremely thin. It is formed so as to straddle the metal layer 36 and the dielectric layer 35.

  Accordingly, a parallel signal path 12a and a conductive path 34 are arranged between the ground port 3 and the SAW resonator 12 connected to the ground port 3, and a capacitance component 37 is interposed in the parallel signal path 12a. It is installed. Since the conductive path 34 has the distributed constant component 38 as described above, the inductor component and the capacitive component 37 of the distributed constant component 38 constitute the series resonance circuit 21. This series resonant circuit 21 has series resonance at a frequency corresponding to the attenuation region of the notch filter according to the size of the inductor component of the distributed constant component 38, specifically according to each dimension and material of the conductive path 34. As described above, the capacitance value in the above-described capacitance component 37 is set.

  Therefore, when an electric signal flows between the input port 1 and the output port 2 and series resonance occurs in each SAW resonator 12, the inductor component of the conductive path 34 causes the SAW resonator 12 and the ground port 3 to be connected. The electric signal flow in the circuit is about to be inhibited. However, since the series resonance circuit 21 is configured by connecting the capacitance component 37 to the inductor component so that series resonance with the inductor component occurs at a frequency corresponding to the attenuation region, the SAW resonator 12 and the ground port are formed in the attenuation region. The electric signal flows between the terminals 3 and 3 very easily. Therefore, a pole of series resonance is formed in each SAW resonator 12 in a state where inhibition by the inductor component of the conductive path 34 is suppressed, and thus a good (large) attenuation amount can be obtained in the attenuation region.

  Here, FIG. 7 shows a simulation of filter characteristics in a state where each component (inductor 11 and piezoelectric substrate 4) is mounted on the package substrate 5, and chip-shaped filter characteristics without mounting these components on the package substrate 5. It can be seen that the attenuation in the attenuation region is degraded by the inductor component of the conductive path 34. On the other hand, as shown in FIG. 8, by forming a series resonant circuit 21 by connecting a capacitance component 37 in series to the conductive path 34, an attenuation amount substantially equal to the characteristic obtained in the chip shape can be obtained. Yes.

  According to the above-described embodiment, in the notch filter including the series arm composed of the inductor 11 and the parallel arm composed of the SAW resonator 12 which is an element portion that causes series resonance at a frequency corresponding to the attenuation region, The inductor 11 and the SAW resonator 12 (piezoelectric substrate 4) are arranged on the package substrate 5 on which the conductive path 34 is formed, and the SAW resonator 12 is grounded through the conductive path 34. A capacitance component 37 having a capacitance value is connected between the SAW resonator 12 and the ground port 3 so that series resonance with the inductor component of the conductive path 34 occurs at a frequency corresponding to the attenuation region. is doing. Therefore, even when the SAW resonator 12 is mounted on the package substrate 5, the inductor component of the conductive path 34 is apparently suppressed in the attenuation region, and therefore the resonance point pole formed by each SAW resonator 12. The coupling between each other can be suppressed, and therefore a notch filter having a good attenuation amount and attenuation width in the attenuation region can be obtained.

  In addition, since the capacitance component 37 is individually provided for each conductive path 34, the pole of the resonance point can be increased for any SAW resonator 12. Furthermore, the dielectric layer 35 is a thin film as described above and is easily broken. However, when the piezoelectric substrate 4 and the package substrate 5 are connected by the bumps 32, bumps are formed in a region that is laterally removed from the dielectric layer 35. Since 32 is formed, it is possible to prevent the dielectric layer 35 from being broken when the bumps 32 are formed, and thus it is possible to manufacture a filter with a high yield.

  Here, when the capacitance value of the capacitance component 37 was calculated, it was found that a good attenuation was obtained in the range of 450 pF to 50000 pF, as shown in FIG. Incidentally, the size of the inductor component of the conductive path 34 at this time was calculated as 0.05 nH (the width dimension and the height dimension of the conductive path 34 were 150 μm and 100 μm, respectively). That is, the preferable capacitance value of the capacitance component 37 varies depending on the size of the inductor component of the conductive path 34, that is, each dimension and material of the conductive path 34. If the size of the inductor component is the above-described value, 450 pF to 50000 pF.

  In the above example, the capacitive component 37 is disposed on the piezoelectric substrate 4, but it may be disposed between the ground port 3 and the SAW resonator 12 connected to the ground port 3. For example, as shown in FIG. Alternatively, it may be disposed above the conductive path 34 on the package substrate 5. Specifically, the above-described metal layer 36 and dielectric layer 35 are laminated in this order from the lower side (package substrate 5 side) above the conductive path 34, and the upper side of the dielectric layer 35 is placed on the upper side. The above-described conductive line 31 may be formed so as to cover it. Also in this case, the side wall portion of the dielectric layer 35 is formed, for example, at a right angle toward the package substrate 5 side so that the metal layer 36 and the conductive line 31 are not directly connected. Further, the capacitive component 37 is arranged so as to be connected to the conductive path 34 from the lower side on the back surface side (grounding port 3 side) of the package substrate 5, and the lower end portion of the capacitive component 37 is used as the grounding port 3. good.

[Second Embodiment: Parallel Resonance]
In the first embodiment described above, in order to suppress the inductor component of the conductive path 34 between the SAW resonator 12 connected to the ground port 3 and the ground port 3, the capacitance component 37 is added to the conductive path 34. Although the series resonance circuit 21 is configured by connecting in series, the parallel resonance circuit 22 may be configured by connecting a capacitance component 37 to the conductive path 34 in parallel. In this case, the anti-resonance frequency (anti-resonance point) of the parallel resonance circuit 22 is set to a region greatly deviating from the frequency corresponding to the attenuation region, in this example, 700 MHz. Accordingly, even in this case, in the attenuation region, the influence of the inductor component of the conductive path 34 between the SAW resonator 12 connected to the ground port 3 and the ground port 3 is suppressed. Hereinafter, an example using such parallel resonance will be described as a second embodiment. In addition, about the site | part of the same structure as 1st Embodiment mentioned above, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  As shown in FIG. 11, the capacitance components 37 of the second embodiment are connected in parallel to the parallel signal path 12a to which the ground port 3 is connected as described above. Specifically, as shown in FIG. 12, the above-described metal films 13a and 13b are disposed independently of each other (the metal films 13a and 13b are disposed so as not to contact each other). Then, on the back side in FIG. 12, parallel signal paths extending from the first bus bar 14b of the first SAW resonator 12 and the second bus bar 14b of the second SAW resonator 12 with respect to the metal films 13a and 13b. 12a are connected in parallel with each other, and parallel signal paths 12a extending from the first bus bar 14b of the third SAW resonator 12 and the second bus bar 14b of the fourth SAW resonator 12 on the front side in FIG. Are connected to the metal films 13a and 13b in parallel. The distance between the metal films 13a and 13b is set to a dimension as short as possible so that the metal films 13a and 13b are insulated from each other, in this example, about 600 μm.

  Then, as shown in FIG. 13, the metal film 13 a is connected to the ground port 3 independently (separately from the metal film 13 b) through the conductive path 34 formed on the package substrate 5, and An auxiliary conductive path 34 a in which a metal body such as copper is embedded is formed in the package substrate 5 so as to be adjacent to the conductive path 34. Further, the metal film 13b is connected to the auxiliary grounding port (second auxiliary electrode portion) 3a formed on the lower surface of the auxiliary conductive path 34a via the bump 32 independently (separately from the metal film 13a). ing. The separation distance between the conductive paths 34 and 34a is set to about 30 μm, for example. The upper end portion of the auxiliary conductive path 34a forms a first auxiliary electrode portion. In FIG. 13, regions around the metal films 13a and 13b are shown in a simplified manner.

  Here, as shown in FIG. 14, on the piezoelectric substrate 4 side of the metal film 13b, a metal layer 36 and a dielectric layer 35 are laminated from the piezoelectric substrate 4 side toward the metal film 13b. The layer 36, the dielectric layer 35, and the metal film 13b constitute the capacitance component 37 described above. Therefore, the capacitive component 37 is connected in parallel to the conductive path 34 connected to the ground port 3 to form the parallel resonance circuit 22. In this case, the capacitance value of the capacitance component 37 is such that the thickness dimension, surface area, and relative dielectric constant (material) of the dielectric layer 35 are set so that the antiresonance point of the parallel resonance circuit 22 is set to the frequency described above. Is set. As shown in FIG. 11 described above, the auxiliary conductive path 34a also has a distributed constant component 38a including an inductor component and the like. FIG. 14 schematically shows the thickness dimensions of the metal layer 36, the dielectric layer 35, and the metal film 13b.

  Therefore, when an electric signal flows between the input port 1 and the output port 2 in this filter, an anti-resonance point is formed at a frequency outside the attenuation region in the parallel resonance circuit 22. Thus, an electrical signal flows between the SAW resonator 12 and the ground port 3 so that the influence of the inductor component of the conductive path 34 connected to 3 is reduced (or eliminated). Therefore, also in the second embodiment, the poles of the series resonance of each SAW resonator 12 are formed, and an attenuation region with a good attenuation amount is obtained.

Also in the second embodiment, the capacitive component 37 may be arranged on the package substrate 5 side (the piezoelectric substrate 4 side on the surface of the package substrate 5 or between the package substrate 5 and the auxiliary ground port 3a).
In the second embodiment, the anti-resonance point of the parallel resonance circuit 22 is set as described above. However, the anti-resonance point may be set in a region outside the frequency corresponding to the attenuation region. Specifically, it may be set to 600 to 800 MHz or 850 to 1000 MHz. Furthermore, the separation distance between the conductive paths 34 and 34a is preferably as close as possible to form the parallel resonant circuit 22, but it is necessary to prevent the conductive paths 34 and 34a from being electrically connected to each other. is there. Therefore, it is preferable that the separation distance is a dimension in which the parallel resonance circuit 22 is formed while insulating between the conductive paths 34 and 34a, specifically about 1 μm to 600 μm.

  Here, the simulation result performed about the filter of 2nd Embodiment is demonstrated. As shown in FIG. 15, by connecting a capacitive component 37 in parallel to the conductive path 34, a large attenuation of −64 dB is obtained in the vicinity of 835 MHz. On the other hand, when the capacitive component 37 is not arranged (conventional notch filter), as shown in FIG. 16, only an attenuation of about −57 dB is obtained in the vicinity of 835 MHz.

  Subsequently, a simulation result of how the frequency characteristic (attenuation characteristic) of the notch filter changes depending on the resistance component included in the capacitance component 37 and the distributed constant component 38 is shown. First, FIG. 17 shows characteristics when only the inductor component is provided as the distributed constant component 38 in the conductive path 34 when the capacitance component 37 is not disposed. FIG. 18 shows the characteristics when the distributed constant component 38 includes a resistance component of 0.3Ω.

  FIG. 19 shows the characteristics when the resistance component of the distributed constant component 38 is 0.1Ω and the capacitance component 37 having a capacitance value of 1000 pF is provided in parallel with the resistance component. 12 shows a characteristic in which a resistance component of 12Ω is arranged in each of two distributed constant components 38, and a capacitance component 37 of 1000 pF is connected in parallel to one and the other of these resistance components, respectively. FIG. 21 shows characteristics in which a resistance component of 6Ω is arranged in each of the two distributed constant components 38 and a capacitance component 37 of 1000 pF is connected in parallel to one and the other of these resistance components. From these results, it can be seen that the attenuation characteristics change by changing the inductor component and the capacitance value. 19, 20, and 21, when the capacitance component 37 is connected in parallel to the resistance component, the SAW resonator 12 is more than the resistance component in the parallel signal path 12 a between the ground port 3 and the SAW resonator 12. When two conductive paths extending from the side and the ground port 3 side are formed, and one end side and the other end side of the capacitive component 37 are connected to these conductive paths (each capacitive component 37 is connected to the ground port 3) Case)).

  In FIG. 22, a resistance component of 0.3Ω is arranged in each of the two distributed constant components 38, a capacitance component 37 of 1000 pF is connected in parallel to each of the resistance components, and the capacitance component 37 is connected to the ground port. The characteristic when connecting to the auxiliary ground port 3a instead of 3 is shown. In FIG. 22, it can be seen that a characteristic with a large attenuation is obtained as compared with the examples of FIGS.

[Other examples]
In the above example, three and four inductors 11 and SAW resonators 12 are arranged, respectively, but a plurality of these inductors 11 and SAW resonators 12 may be arranged, for example, four and five.

  In addition, the parallel signal path 12 a including the conductive path 34, the bump 32, and the routing electrode 16 between the ground port 3 and the SAW resonator 12 connected to the ground port 3 is compared with the size of the conductive path 34. Therefore, the inductor component such as the bump 32 is smaller than the inductor component of the conductive path 34. Therefore, in the series resonance circuit 21 and the parallel resonance circuit 22, the capacitance value of the capacitance component 37 is set so as to resonate with the inductor component of the conductive path 34, but as the capacitance component 37, resonance with the inductor component of the conductive path 34 occurs. Instead, the capacitance value may be set so as to cause resonance with the inductor component of the parallel signal path 12a and the conductive path 34 between the ground port 3 and the SAW resonator 12 connected to the ground port 3. . In that case, a filter having a better attenuation characteristic can be obtained.

  Further, the inductor 11 and the SAW resonator 12 are mounted on the common package substrate 5. However, the inductor 11 is arranged on a substrate different from the package substrate 5 and the inductor 11 and the SAW resonator are connected via an electrode (not shown). 12 may be connected to each other. Further, a plurality of, for example, two ground ports 3 are provided, and the series resonant circuit 21 or the parallel resonant circuit 22 is arranged on the conductive paths 34 connected to the respective ground ports 3. At least one of these conductive paths 34 is provided. A series resonance circuit 21 and a parallel resonance circuit 22 may be arranged. Further, the conductive path 34 and the ground port 3 may be provided individually for the plurality of SAW resonators 12, and the series resonant circuit 21 and the parallel resonant circuit 22 may be connected to each conductive path 34.

  Further, in each of the above examples, the inductor 11 and the SAW resonator 12 are used as the series arm and the parallel arm, respectively, but as shown in FIG. 23, the SAW resonator 12 and the inductor 11 are arranged as the series arm and the parallel arm, respectively. You may do it. Also in this case, the SAW resonator 12 is disposed on the piezoelectric substrate 4 and the inductor 11 and the piezoelectric substrate 4 are disposed on the package substrate 5 so that the series resonant circuit 21 or the parallel resonant circuit 22 is configured. Capacitance component 37 is connected in series or in parallel with the inductor component between 11 and ground port 3. FIG. 23 shows an example in which a series resonance circuit 21 is provided. Furthermore, in FIG. 23, instead of the inductor 11, an element that causes parallel resonance at a frequency outside the attenuation range, for example, a SAW resonator 12 may be disposed as a parallel arm.

In the above, the SAW resonator 12 may be a resonator using an elastic wave propagating in the piezoelectric substrate 4 instead of the resonator using the surface acoustic wave.
Furthermore, instead of the SAW resonator 12, a crystal resonator, a piezoelectric thin film resonator, a MEMS resonator, or a dielectric may be used as an element unit that causes series resonance or parallel resonance. Examples of the piezoelectric thin film resonator include an FBAR (Film Bulk Acoustic Resonator) and an SMR (Solid Mounted Resonator). When a dielectric is used as the element portion, the dielectric is provided on both sides of the microstrip line. Further, the element unit includes a resonance circuit (LC resonance circuit) in which a coil and a capacitor are connected in parallel.

In addition to the configuration in which the metal film 13b, the dielectric layer 35, and the metal layer 36 are stacked as the capacitive component 37, the IDT electrodes described above in which capacitive components are formed between the electrode fingers 14a and 14a adjacent to each other 14 may be sufficient. When the IDT electrode 14 is used as the capacitive component 37, the capacitive component 37 is patterned on the piezoelectric substrate 4 or the package substrate 5. When the capacitive component 37 formed of the IDT electrode 14 is provided on the piezoelectric substrate 4, the capacitive component 37 is prevented so that the elastic wave generated in the capacitive component 37 does not affect the other SAW resonator 12. Reflectors and absorbers are arranged on both sides in the propagation direction of the elastic wave. Furthermore, the capacitance component 37 may be arranged on the package substrate 5 as a component such as an external capacitor.
Also, examples of electronic components to which the filter of the present invention is applied include SAWBEF and a digital terrestrial TV tuner module using the filter.

DESCRIPTION OF SYMBOLS 1 Input port 2 Output port 3 Grounding port 3a Auxiliary grounding port 5 Package board 12 SAW resonator 12a Parallel signal path 21 Series resonant circuit 22 Parallel resonant circuit 34 Conductive path 34a Auxiliary conductive path 37 Capacitance component 38 Distributed constant component

Claims (8)

In the notch filter for providing an attenuation band between the pass bands formed on the low band side and the high band side,
A plurality of phase inversion inductors connected in series as a series arm between the input port and the output port;
An insulating plate;
A first electrode portion formed on one surface side and the other surface side of the insulating plate, respectively, and a second electrode portion forming a ground port;
A conductive path formed inside the insulating plate to connect the first electrode portion and the second electrode portion to each other;
A plurality of parallel arms, each having one end connected between the series arms adjacent to each other and having the other end connected to the first electrode portion, causing series resonance at a frequency corresponding to the attenuation region. Element part of
A capacitance component provided between the element portion and the second electrode portion, the capacitance value of which is set so that series resonance occurs with the inductor component of the conductive path at a frequency corresponding to the attenuation region; And a notch filter. A second auxiliary electrode portion that is provided adjacent to the first electrode portion and the second electrode portion on one surface side and the other surface side of the insulating plate, respectively, and forms a first auxiliary electrode portion and an auxiliary ground port. When,
An auxiliary conductive path formed inside the insulating plate to connect the first auxiliary electrode part and the second auxiliary electrode part to each other;
A parallel signal path for connecting the other end side of the element part and the first auxiliary electrode part to each other;
The capacitance component is provided between the element portion and the second electrode portion, and the capacitance value is set so that series resonance occurs with the inductor component of the conductive path at a frequency corresponding to the attenuation region. Instead of being provided, it is provided between the element part and the second auxiliary electrode part so that parallel resonance occurs with the inductor component of the conductive path at a frequency outside the attenuation region. The notch filter according to claim 1, wherein a capacitance value is set in the notch filter.   The notch filter according to claim 2, wherein a separation distance between the conductive path and the auxiliary conductive path is 600 μm or less.   The capacitive component is a laminated film in which a dielectric layer is interposed between two metal layers, and one of these metal layers is connected to the element portion side. 4. The notch filter according to any one of 3. The element unit is a SAW resonator formed on a piezoelectric substrate,
The notch filter according to claim 4, wherein the capacitive component is disposed on the piezoelectric substrate. The series arm is an element portion that causes parallel resonance at a frequency corresponding to the attenuation region, instead of an inductor for phase inversion,
6. The notch filter according to claim 1, wherein the parallel arm is an inductor for phase inversion instead of an element portion that causes series resonance at a frequency corresponding to the attenuation region. .   The capacitance component has a capacitance value set so that series resonance occurs with the inductor component of the conductive path, and the inductor component and the series resonance between the element portion and the second electrode portion. The notch filter according to claim 1, wherein a capacitance value is set so as to occur.   The capacitance component has a capacitance value set so that parallel resonance with the inductor component of the conductive path occurs, and the inductor component and parallel resonance between the element portion and the second electrode portion 3. The notch filter according to claim 2, wherein a capacitance value is set so as to occur.

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