JP4390682B2 - Filter using piezoelectric resonator - Google Patents

Description

  The present invention relates to a filter using a piezoelectric resonator, and more particularly to a filter using a piezoelectric resonator used in a radio circuit of a mobile communication terminal such as a mobile phone or a wireless LAN.

  Components built in cellular phones, wireless LANs, and the like are required to be smaller, lighter, and higher performance. One of the parts that satisfy these requirements is a filter using a piezoelectric resonator composed of a piezoelectric body (see Patent Document 1). Hereinafter, an example of this filter will be described with reference to the drawings.

  First, before describing the configuration of the filter, the structure of the piezoelectric resonator used in the filter will be described. FIG. 21 is a perspective view showing a single structure of a basic piezoelectric resonator. 22 is a cross-sectional view taken along the line BB in FIG. 23A and 23B are a circuit symbol and an equivalent circuit diagram of the piezoelectric resonator, respectively. FIG. 24 is a diagram showing frequency characteristics of the piezoelectric resonator alone.

Referring to FIG. 21, the piezoelectric resonator 210 is formed by forming an upper electrode layer 211, a piezoelectric layer 212, a lower electrode layer 213, an insulator layer 214, and a cavity 215 on a substrate 216 such as silicon or glass. Composed. The cavity 215 is provided on the substrate 216 in a non-penetrating manner. An insulator layer 214 made of silicon dioxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ) or the like is formed so as to cover the cavity 215. On the insulating layer 214, a lower electrode layer 213 made of molybdenum (Mo), aluminum (Al), silver (Ag), tungsten (W), platinum (Pt), or the like is formed. On the lower electrode layer 213 of aluminum nitride (AlN), zinc oxide (ZnO), lithium niobate (LiNbO _3), lithium tantalate (LiTaO _3), a piezoelectric layer made of such as potassium niobate (KNbO ₃₎ 212 is formed. An upper electrode layer 211 made of the same material as that of the lower electrode layer 213 is formed on the piezoelectric layer 212. The upper electrode layer 211, the piezoelectric layer 212, the lower electrode layer 213, and the insulator layer 214 constitute a vibration unit 218. Therefore, the vibration part 218 has a structure supported by a part 221 of the substrate 216 as shown in FIG. The cavity 215 is provided to confine mechanical vibration of the piezoelectric layer 212.

By applying a voltage between the upper electrode layer 211 and the lower electrode layer 213, an electric field is generated in the piezoelectric layer 212, and distortion caused by the electric field is excited as mechanical vibration, which is an electrical resonance characteristic. And converted into anti-resonance characteristics. Resonance frequency f _r and the antiresonance frequency f _a of the piezoelectric resonator 210, the thickness of each layer and the size of the vibrating portion 218, also determined by parameters such as the material constants. An equivalent circuit of the piezoelectric resonator 210 shown in FIG. 23A is represented by an electrostatic capacitance C ₀ , an equivalent constant C _1, and an equivalent constant L ₁ as shown in FIG. 23B. Since the resistance component is very small, it is omitted in the equivalent circuit of FIG. 23B. When the capacitance C ₀ is regarded as a capacitance sandwiched between the upper electrode layer 211 and the lower electrode layer 213, the dielectric constant ε _{0 in} vacuum, the relative dielectric constant ε _{r of} the piezoelectric body, the electrode area S, and the piezoelectric body The thickness d can be calculated by the following formula (1).
C ₀ = ε ₀ ε _r × S / d (1)

Further, in the equivalent circuit shown in FIG. 23B, and a parallel resonance that series resonance and impedance impedance becomes 0 becomes infinite, the resonance frequency f _r and the antiresonance frequency f _a is the following formulas (2) and (3 ). The frequency characteristics of the piezoelectric resonator 210 alone are as shown in FIG.
f _r = 1 / (2π × √ (C ₁ L ₁ )) (2)
f _a = _fr × √ (1 + C ₁ / C ₀ ) (3)

  FIG. 25 is a diagram showing an example of a circuit diagram of a conventional filter using three stages of piezoelectric resonators having the frequency characteristics described above. In FIG. 25, a conventional filter 250 includes a series piezoelectric resonator 251, parallel piezoelectric resonators 252a and 252b, and inductors 253a and 253b. The series piezoelectric resonator 251 is connected in series between the input terminal 255a and the output terminal 255b. The parallel piezoelectric resonator 252a has one electrode connected to a connection point between the input terminal 255a and the series piezoelectric resonator 251 and the other electrode connected to one terminal of the inductor 253a. The parallel piezoelectric resonator 252b has one electrode connected to the connection point between the series piezoelectric resonator 251 and the output terminal 255b, and the other electrode connected to one terminal of the inductor 253b. The other terminals of the inductors 253a and 253b are grounded.

The conventional filter 250 having this configuration includes a frequency characteristic (solid line in FIG. 26 graph (a)) by the parallel piezoelectric resonators 252a and 252b, and a frequency characteristic by the series piezoelectric resonator 251 (dotted line in the graph (a) in FIG. 26). It will have two. Therefore, if each parameter of the filter 250 is set so that the anti-resonance point 262 of the parallel piezoelectric resonators 252a and 252b and the resonance point 263 of the series piezoelectric resonator 251 are substantially matched, the graph (b) in FIG. A filter having a pass band 265 as shown in FIG.
Japanese Patent No. 2800905

However, the conventional filter cannot be expected to obtain a large attenuation in the frequency bands before and after the pass band. Therefore, this filter cannot be used for a filter of a mobile communication terminal such as a mobile phone or a wireless LAN that needs to pass one of two frequency bands and attenuate the other. For example, in the reception filter for W-CDMA, the reception band is 2.11 to 2.17 GHz and the transmission band is 1.92 to 1.98 GHz.
Further, in the above conventional filter configuration, a large value inductor must be provided between the parallel piezoelectric resonator and the ground, and a new external circuit such as a substrate is required, which increases the size of the filter. Also had.

  Therefore, an object of the present invention is to provide a filter using a piezoelectric resonator capable of suppressing a loss in a pass band while securing an attenuation amount in an attenuation band. Another object of the present invention is to provide a filter using a piezoelectric resonator in which the value and number of inductors necessary for a circuit are reduced to reduce the size.

The present invention is directed to a filter used for constituting the multiple piezoelectric resonator. In order to achieve the above object, the filter of the present invention includes one or more series piezoelectric resonators connected in series between input and output terminals, and the most input terminal of the series piezoelectric resonator. are connected to each side of the terminal and the most of the output terminal side terminals, and two parallel piezoelectric resonators connected in parallel in a ladder to the series piezoelectric resonators, respectively Noso two parallel piezoelectric resonators provided, and two inductors that connects between the ground and the respective electrode which is not connected to the series piezoelectric resonators of the two parallel piezoelectric resonators, connected two inductors of the two parallel piezoelectric resonators respectively composed of one or more sequentially connected added piezoelectric resonator connecting the electrodes.

As the Scripture type specific filter configuration, between the input and output terminals, and first and second series piezoelectric resonators connected in succession in series, is connected to an input terminal of the first series piezoelectric resonator A first parallel piezoelectric resonator having one electrode connected to one terminal, a second electrode having one electrode connected to the other terminal of the first series piezoelectric resonator and one terminal of the second series piezoelectric resonator. A parallel piezoelectric resonator, a third parallel piezoelectric resonator having one electrode connected to the other terminal connected to the output terminal of the second series piezoelectric resonator, and the other electrode of the first parallel piezoelectric resonator; A first inductor connecting between the ground, a second inductor connecting between the other electrode of the third parallel piezoelectric resonator and the ground, and the other electrode of the first parallel piezoelectric resonator and the third And an additional piezoelectric resonator connecting the other electrode of the parallel piezoelectric resonator. In this configuration, the number of piezoelectric resonators constituting the total number and the additional piezoelectric resonator of the piezoelectric resonators constituting the first and second series piezoelectric resonator, even-odd there is a same der Turkey preferred.

As another exemplary filter configuration, between the input and output terminals, the first to third series piezoelectric resonators connected in succession in series, connected to an input terminal of the first series piezoelectric resonator A first parallel piezoelectric resonator in which one electrode is connected to the one terminal formed, a first electrode connected to the other terminal of the first series piezoelectric resonator and one terminal of the second series piezoelectric resonator. Two parallel piezoelectric resonators, a third parallel piezoelectric resonator having one electrode connected to the other terminal of the second series piezoelectric resonator and one terminal of the third series piezoelectric resonator, and a third series A fourth parallel piezoelectric resonator having one electrode connected to the other terminal connected to the output terminal of the piezoelectric resonator, and a first inductor connecting between the other electrode of the first parallel piezoelectric resonator and the ground And a second inductor connecting the other electrode of the second parallel piezoelectric resonator and the ground, A third inductor that connects the other electrode of the third parallel piezoelectric resonator and the ground, a fourth inductor that connects the other electrode of the fourth parallel piezoelectric resonator and the ground, a first additional piezoelectric resonator which connects between the other electrode of the parallel piezoelectric resonators of the other electrode and the parallel piezoelectric resonators of the n (one of n = 2 to 4), first and second n And the second additional piezoelectric resonator connecting the other electrodes of the two parallel piezoelectric resonators.

  As the series piezoelectric resonator, the parallel piezoelectric resonator, and the additional piezoelectric resonator constituting the filter, a thin film elastic wave resonator can be considered. The thin film acoustic wave resonator may be configured such that a piezoelectric layer is sandwiched between an upper electrode and a lower electrode, and a cavity is provided under the lower electrode. In addition, as a thin film acoustic wave resonator without a cavity, a piezoelectric layer is sandwiched between the upper electrode and the lower electrode, and a low impedance layer and a high impedance layer are alternately laminated under the lower electrode. A configuration in which an acoustic multilayer film is provided is also conceivable. Further, it is preferable that each piezoelectric resonator performs electrode connection between adjacent piezoelectric resonators on the equivalent circuit using the same wiring layer.

  A surface acoustic wave resonator can be considered as a piezoelectric resonator constituting this filter. The surface acoustic wave resonator may have a configuration in which an interdigital transducer electrode and a reflector electrode are arranged close to a propagation direction on a piezoelectric substrate.

  As described above, according to the filter using the piezoelectric resonator of the present invention, at least one additional piezoelectric resonator is inserted between the other electrodes of any two parallel piezoelectric resonators. As a result, it is possible to secure a desired attenuation amount in the attenuation band while maintaining suppression of the passage loss in the pass band and an increase in the bandwidth.

  The characteristic configuration provided by the present invention is composed of one series piezoelectric resonator inserted in series with respect to a signal input / output terminal and two parallel piezoelectric resonators inserted in parallel. Any ladder-type filter having more than one stage can be applied regardless of the number of stages. Hereinafter, the present invention will be described by taking as an example a three-stage ladder type filter composed of one series piezoelectric resonator and two parallel piezoelectric resonators.

(First embodiment)
FIG. 1 is a circuit diagram of a filter 10 using a piezoelectric resonator according to a first embodiment of the present invention. In FIG. 1, the filter 10 of the first embodiment includes a series piezoelectric resonator 11, parallel piezoelectric resonators 12 a and 12 b, inductors 13 a and 13 b, and an additional piezoelectric resonator 14.

  The series piezoelectric resonator 11 is connected in series between the input terminal 15a and the output terminal 15b. The parallel piezoelectric resonator 12a has one electrode connected to the connection point between the input terminal 15a and the series piezoelectric resonator 11, and the other electrode connected to one terminal of the inductor 13a. The parallel piezoelectric resonator 12b has one electrode connected to a connection point between the series piezoelectric resonator 11 and the output terminal 15b, and the other electrode connected to one terminal of the inductor 13b. The other terminals of the inductors 13a and 13b are grounded. The additional piezoelectric resonator 14 is connected between the other electrode of the parallel piezoelectric resonator 12a and the other electrode of the parallel piezoelectric resonator 12b.

By connecting the additional piezoelectric resonator 14 as shown in FIG. 1, an equivalent circuit of the series network shown in FIG. 2 is added to the conventional circuit shown in FIG. Resonance frequency f _r and the antiresonance frequency f _a of the equivalent circuit of FIG. 2, can be determined similarly by the above-mentioned equations (2) and (3). However, in this case, it is necessary to consider the influence of the inductor 13a and 13b, the actual resonance frequency f ₀ is lower than the resonance frequency f _r. That is, by appropriately controlling the resonance frequency f ₀ , an attenuation band can be provided at a desired position.

  3 shows the pass characteristic (solid line) of the filter 10 shown in FIG. 1 and the pass characteristic (dotted line) of the conventional filter 250 shown in FIG. The pass characteristic of the filter 10 ensures a sufficient amount of attenuation in a desired frequency band (attenuation band) by adjusting the resonance frequency of the additional piezoelectric resonator 14.

  As described above, according to the filter 10 using the piezoelectric resonator according to the first embodiment of the present invention, the additional piezoelectric resonator is inserted between the other electrodes of the two parallel piezoelectric resonators. As a result, compared with the conventional filter 250, it is possible to suppress the loss in the pass band while securing the desired attenuation amount in the attenuation band while maintaining the suppression of the pass loss and the increase in the bandwidth in the pass band. It becomes. Therefore, the filter of the present invention having this configuration can be used as a reception filter or a transmission filter of a mobile communication terminal such as a mobile phone or a wireless LAN.

As shown in FIG. 4A, a series piezoelectric resonator 11a is provided between the input terminal 15a and one electrode of the parallel piezoelectric resonator 12a, and a series piezoelectric element is provided between the one electrode of the parallel piezoelectric resonator 12b and the output terminal 15b. A configuration of the filter 40 in which each of the resonators 11b is inserted is also conceivable. Even in this filter 40, by appropriately adjusting the resonance frequency of the additional piezoelectric resonator 14, a sufficient amount of attenuation can be ensured in a desired frequency band (attenuation band).
Further, as shown in FIGS. 4B and 4C, an additional piezoelectric element is added to a five-stage ladder filter composed of two series piezoelectric resonators inserted in series and three parallel piezoelectric resonators inserted in parallel. A filter configuration in which the resonator 14 is inserted is also conceivable.

(Second Embodiment)
FIG. 5A is a circuit diagram of a filter 50 using a piezoelectric resonator according to the second embodiment of the present invention. 5A, the filter 50 of the second embodiment includes three series piezoelectric resonators 11a to 11c, four parallel piezoelectric resonators 12a to 12d, four inductors 13a to 13d, and an additional piezoelectric resonator 14. It consists of.

  The series piezoelectric resonators 11a to 11c are connected in series between the input terminal 15a and the output terminal 15b. One electrode of each of the parallel piezoelectric resonators 12a to 12d is connected to one of connection points connecting the input terminal 15a, the series piezoelectric resonators 11a to 11c, and the output terminal 15b. The other electrodes of the parallel piezoelectric resonators 12a to 12d are connected to one terminals of the inductors 13a to 13d, respectively. The other terminals of the inductors 13a to 13d are grounded. The additional piezoelectric resonator 14 is connected between the other electrode of the parallel piezoelectric resonator 12b and the other electrode of the parallel piezoelectric resonator 12c. The additional piezoelectric resonator 14 may be connected between any two points of the other electrodes of the parallel piezoelectric resonators 12a to 12d. In addition to the connection form shown in FIG. 5A, the connection shown in FIGS. 5B to 5F is possible. Possible forms.

As described above, the equivalent circuit of the series network shown in FIG. 2 is added by connecting the additional piezoelectric resonator 14 as shown in FIG. 5A. Therefore, by appropriately controlling the resonance frequency f ₀ , an attenuation band can be provided at a desired position.

  As described above, according to the filter 50 using the piezoelectric resonator according to the second embodiment of the present invention, the additional piezoelectric resonator is inserted between the other electrodes of any two parallel piezoelectric resonators. Thereby, as compared with the conventional filter 250, it is possible to secure a desired attenuation amount in the attenuation band while maintaining the suppression of the passage loss in the pass band and the increase in the bandwidth.

  In the second embodiment, the case where the number of additional piezoelectric resonators 14 connected between any two points of the other electrodes of the parallel piezoelectric resonators 12a to 12d is one has been described. However, two additional piezoelectric resonators may be connected. In this case, as shown in FIGS. 6A to 6C, it is necessary that the two additional piezoelectric resonators are connected without overlapping between any two points of the other electrodes of the parallel piezoelectric resonators 12a to 12d. It becomes.

  The number of additional piezoelectric resonators is not limited to one or two, and can be freely set according to desired pass characteristics, product size / cost, and the like. Also, the number of additional piezoelectric resonators connected to each parallel piezoelectric resonator is one, as in the circuits shown in FIGS. 5A to 5F, FIGS. 6A to 6C, and FIGS. 7A to 7X. Is preferable in terms of characteristics, but a configuration in which a plurality of additional piezoelectric resonators are connected to one parallel piezoelectric resonator as in the circuits shown in FIGS. 8A and 8B may be used. Even in this configuration, if the material, thickness, size, and the like of the piezoelectric layer are optimally set, it is possible to sufficiently obtain desired pass characteristics.

  In the case of the filter configuration of the present invention, the inductors 13a to 13d connected to the other electrodes of the parallel piezoelectric resonators 12a to 12d can be omitted if the additional piezoelectric resonator 14 is not connected. That is, the other electrode of the parallel piezoelectric resonator to which the additional piezoelectric resonator is not connected may be directly grounded (for example, FIG. 9). Further, an inductor may be inserted between the input terminal and the series piezoelectric resonator and between the series piezoelectric resonator and the output terminal (for example, FIG. 10). Note that these inductors included in the filter of the present invention can be reduced in value relative to a conventional filter (FIG. 25, etc.) by inserting an additional piezoelectric resonator. Since the filter of the present invention is usually formed on a semiconductor substrate, an inductor necessary for the filter can be formed by a parasitic inductor such as an electrode, wiring, bonding wire, or bump. An example of the semiconductor chip 110 in which the inductor is configured by wiring is shown in FIG. 11A, and an example of the semiconductor package 111 in which the inductor is configured by bonding wires is shown in FIG. 11B. The semiconductor chip on which the filter is formed may be disposed on a printed board or a low-temperature sintered ceramic (LTCC) as necessary.

(Third embodiment)
As described above, the filter circuit shown in each figure is configured by connecting each piezoelectric resonator with an electrode of each piezoelectric resonator on a semiconductor substrate. FIG. 11A is a top view of the semiconductor chip 110 constituting the circuit of the filter 50 shown in FIG. 5A. In the figure, the grid-like shaded portion indicates the upper electrodes of the piezoelectric resonators 11a to 11c, 12a to 12d and 14, the dotted shaded portion indicates the upper layer wiring, and the hatched shaded portion indicates the lower layer wiring or the inductors 13a to 13d. ing. In order to use the space without waste as in the semiconductor chip 110 of FIG. 11A, it is most effective to change the electrode connection layer of the piezoelectric resonator alternately up and down every time the piezoelectric layer is sandwiched as shown in FIG. It is. Therefore, if the additional piezoelectric resonator 14 is also inserted between the upper layer and the lower layer, the chip design is facilitated.

  In the example of FIG. 12, the other electrode of the parallel piezoelectric resonator 12b is formed as an “upper layer”, and the other electrode of the parallel piezoelectric resonator 12c is formed as a “lower layer”. It will be easy to do. On the other hand, both the other electrode of the parallel piezoelectric resonator 12a and the other electrode of the parallel piezoelectric resonator 12c, and the other electrode of the parallel piezoelectric resonator 12b and the other electrode of the parallel piezoelectric resonator 12d are both in the same layer. An electrode is formed. For this reason, when an additional piezoelectric resonator is inserted, it is necessary to connect the upper and lower layers by partially short-circuiting the upper and lower electrode layers.

Therefore, in the third embodiment, a filter configuration will be described in which the number of piezoelectric resonators is adjusted so that additional piezoelectric resonators can be inserted between the upper layer and the lower layer. 13 and 14 are examples of circuit diagrams of a filter using the piezoelectric resonator according to the third embodiment using this configuration.
FIG. 13 shows a configuration of a filter 130 using an additional piezoelectric resonator 134 in which two piezoelectric resonators are connected in series. Thereby, even if the other electrode of the parallel piezoelectric resonator 12a and the other electrode of the parallel piezoelectric resonator 12c are the same layer, the additional piezoelectric resonator 134 can be inserted. FIG. 14 shows a configuration of the filter 140 in which a piezoelectric resonator 141 is further added to the series piezoelectric resonator side, and layers on both pole sides of the additional piezoelectric resonator 14 are made different.
In addition, even when the layers on both pole sides of the additional piezoelectric resonator are originally different, a configuration such as the series piezoelectric resonator 151 and the additional piezoelectric resonator 154 shown in FIG. 15 is possible.

  Thus, the number of additional piezoelectric resonators inserted into the filter and the number of series piezoelectric resonators between which the additional piezoelectric resonators are inserted are both even or both odd (ie, even and odd are the same). By controlling the number of piezoelectric resonators constituting the filter, it is not necessary to connect the upper and lower layers by partially short-circuiting the upper and lower electrode layers.

(Piezoelectric resonator structure 1)
The general structure of the series piezoelectric resonator, the parallel piezoelectric resonator, and the additional piezoelectric resonator used in the filter of each embodiment of the present invention is as described with reference to FIG. 21, but other structures are also conceivable. Hereinafter, the structure of the piezoelectric resonator other than that shown in FIG. 21 will be described.

  In FIG. 21, the cavity 215 is covered with the insulator layer 214, but the cavity 165 may not be covered with the insulator layer 214 as shown in FIG. 16. With such a structure, after each layer of the vibrating portion 218 is deposited, the material filled in the cavity 165 can be removed by etching. The cavity may have any structure as long as it does not hinder the vibration of the vibration unit 218, and the frontage may have any shape such as a polygon, a circle, or an ellipse as well as a square. Further, the cavity may be tapered when viewed from the side. Further, the cavity may penetrate the lower portion of the substrate 216.

  Further, instead of providing the cavity 215 as shown in FIG. 22 and configuring the support part 221 with a part of the substrate 216, an individual support part 171 is provided on the substrate 216 as shown in FIG. A cavity 175 that vibrates may be secured.

  Moreover, as a structure which does not provide a cavity, the structure shown in FIG.18 and FIG.19 can be considered. In the structure of the piezoelectric resonator 180 of FIG. 18 and FIG. 19, a vibration unit 218 composed of a piezoelectric layer 212 sandwiched between an upper electrode layer 211 and a lower electrode layer 213 is disposed on an acoustic multilayer film. The acoustic multilayer film is configured on the substrate 216. This acoustic multilayer film is formed by alternately laminating the low acoustic impedance layers 184 and the high acoustic impedance layers 185 each having a quarter wavelength. By making the first layer of the acoustic multilayer film as the low impedance layer 184 when viewed from the vibration unit 218, the load impedance to the piezoelectric layer 212 is sufficiently reduced, and the piezoelectric layer 212 and the substrate 216 are acoustically isolated. It is the structure which was made to do. With such a structure, the vibration unit 218 approaches the state of free vibration that is not supported by anything even though it is fixed to the substrate 216, and exhibits the same operation as the piezoelectric resonator 210 in FIG. . The larger the number of the low impedance layers 184 and the high impedance layers 185 stacked, the more the vibration part 218 is acoustically isolated from the substrate 216.

The low impedance layer 184 is made of a material such as silicon dioxide (SiO ₂ ) or silicon nitride (Si ₃ N ₄ ), and the high impedance layer 185 is made of aluminum nitride (AlN), zinc oxide (ZnO), molybdenum ( Materials such as Mo), hafnium oxide (HfO ₂ ), titanium oxide (TiO ₂ ), and zirconium oxide (ZrO ₂ ) are used.

The layer structure of the piezoelectric resonator 210 is only an example, and the same effect can be obtained by thinly attaching a piezoelectric layer as a passivation film on the upper electrode or providing an insulating layer between the piezoelectric layer and the electrode. The components of the present invention are not limited to this.
Further, the areas of the vibrating portion 218 including the upper electrode layer 211, the piezoelectric layer 212, the lower electrode layer 213, and the insulator layer 214 may be different from each other. Furthermore, each layer other than the upper electrode layer 211 and the lower electrode layer 213 may be continuously generated between the piezoelectric resonators.
Further, the same effect can be obtained even if the electrode shape is any shape such as a round shape, a polygonal shape or a constricted shape, similarly to the cavity shape.

(Piezoelectric resonator structure 2)
FIG. 20 is a diagram illustrating an example of a surface acoustic wave filter 200 in which the piezoelectric resonator of the filter 10 according to the first embodiment is configured by a surface acoustic wave resonator. The surface acoustic wave resonator is configured by disposing an interdigital transducer electrode and a reflector electrode on a piezoelectric substrate 206 close to the propagation direction. The surface acoustic wave filter 200 includes series surface acoustic wave resonators 201 a to 201 c, parallel surface acoustic wave resonators 202 a to 202 d, and additional surface acoustic wave resonators 204 formed on a piezoelectric substrate 206. It connects by the wiring electrode of. Here, the resonance frequency of the surface acoustic wave resonator is optimally set to obtain desired filter characteristics by adjusting the electrode finger pitch, the metallization ratio, or the electrode film thickness. The first electrode pad 205a is connected to one of the input / output terminals via an inductance component, and the second electrode pad 205b is connected to the other of the input / output terminals via an inductance component. The ground electrode pads 203a to 203d are connected to the parallel surface acoustic wave resonators 202a to 202d and are grounded via an inductance component. Further, an additional surface acoustic wave resonator 204 is connected between the ground electrode pads 203b and 203c.

  The filter using the piezoelectric resonator of the present invention is small in size, has a high attenuation in a desired attenuation band and a low loss characteristic in a pass band, and is a radio circuit in a mobile communication terminal such as a mobile phone or a wireless LAN. It is useful as an internal filter. Moreover, it can be applied to uses such as a filter for a radio base station according to the specification.

1 is a circuit diagram of a filter 10 using a piezoelectric resonator according to a first embodiment of the present invention. Equivalent circuit added by additional piezoelectric resonator 14 The figure which shows the passage characteristic of the filter 10 Circuit diagram of another filter to which the filter 10 of FIG. 1 is applied Circuit diagram of another filter to which the filter 10 of FIG. 1 is applied Circuit diagram of another filter to which the filter 10 of FIG. 1 is applied Circuit diagram of filter 50 using a piezoelectric resonator according to a second embodiment of the present invention Circuit diagram of another filter equivalent to filter 50 of FIG. 5A Circuit diagram of another filter equivalent to filter 50 of FIG. 5A Circuit diagram of another filter equivalent to filter 50 of FIG. 5A Circuit diagram of another filter equivalent to filter 50 of FIG. 5A Circuit diagram of another filter equivalent to filter 50 of FIG. 5A Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. Circuit diagram of another filter equivalent to the filter 10 of FIG. FIG. 5A is a top view of the semiconductor chip 110 constituting the circuit of the filter 50 shown in FIG. 5A. FIG. 5A is a top view of the semiconductor package 111 constituting the circuit of the filter 50 shown in FIG. 5A. The figure explaining the connection layer of each piezoelectric resonator in the semiconductor chip 110 The circuit diagram of the filter 130 using the piezoelectric resonator which concerns on the 3rd Embodiment of this invention. Circuit diagram of another filter 140 that is equivalent to filter 130 of FIG. Circuit diagram of another filter 150 equivalent to the filter 130 of FIG. A perspective view and a sectional view showing a unit structure of another piezoelectric resonator A perspective view and a sectional view showing a unit structure of another piezoelectric resonator A perspective view and a sectional view showing a unit structure of another piezoelectric resonator A perspective view and a sectional view showing a unit structure of another piezoelectric resonator The figure which shows an example of the surface acoustic wave filter 200 which comprised the piezoelectric resonator with the surface acoustic wave resonator. Perspective view and cross-sectional view showing a unitary structure of a basic piezoelectric resonator Perspective view and cross-sectional view showing a unitary structure of a basic piezoelectric resonator Circuit symbol and equivalent circuit diagram of piezoelectric resonator Circuit symbol and equivalent circuit diagram of piezoelectric resonator Diagram showing the frequency characteristics of a single piezoelectric resonator Circuit diagram of filter 250 using conventional piezoelectric resonator The figure which shows the passage characteristic of the filter 250

Explanation of symbols

10, 40, 50, 130-180, 210, 250 Filter 200 Surface acoustic wave filters 11, 11a-11b, 12a-12d, 14, 134, 141, 151, 154, 251, 252 Piezoelectric resonators 13a-13d, 253 Inductors 15a to 15b, 205a to 205b, 255a to 255b Terminals (electrode pads)
110 Semiconductor chip 111 Semiconductor package 165, 175, 215 Cavity 171, 221 Support portion 184 Low impedance layer 185 High impedance layer 201a-201c, 202a-202d, 204 Surface acoustic wave resonator 206, 216 Substrate 211, 213 Electrode layer 212 Piezoelectric Body layer 214 Insulator layer 218 Vibrating part

Claims (12)

A filter used for constituting the multiple piezoelectric resonator,
One or more series piezoelectric resonators connected in series between the input and output terminals, and
Two parallel piezoelectric resonators connected in parallel to each other at the most input terminal side and the most output terminal side terminal of the series piezoelectric resonator and connected in parallel to the series piezoelectric resonator in a ladder shape;
Provided in the two parallel piezoelectric resonators Noso respectively, and two inductors that connects the respective electrode to which the not connected to the series piezoelectric resonators of the two parallel piezoelectric resonators and the ground,
Composed of the previous SL two parallel piezoelectric resonators of the two inductors additional piezoelectric resonators connected one or more consecutive connecting the electrodes which are respectively connected, filter. The filter according to claim 1 , wherein the series piezoelectric resonators and the additional piezoelectric resonators are configured in the same number. A filter using a plurality of piezoelectric resonators in its configuration,
Between the input and output terminals, and first and second series piezoelectric resonators connected in succession in series,
A first parallel piezoelectric resonator having one electrode connected to one terminal connected to an input terminal of the first series piezoelectric resonator;
A second parallel piezoelectric resonator having one electrode connected to the other terminal of the first series piezoelectric resonator and one terminal of the second series piezoelectric resonator;
A third parallel piezoelectric resonators the second series piezoelectric resonator contrast to the connected second terminal to an output terminal of the electrodes are connected,
A first inductor connecting between the other electrode of the first parallel piezoelectric resonator and the ground;
A second inductor connecting between the other electrode of the third parallel piezoelectric resonator and the ground;
Characterized in that it is constituted by an additional piezoelectric resonators connected between said first of said the other electrode of the parallel piezoelectric resonators third parallel piezoelectric resonators of the other electrodes, filters. The number of piezoelectric resonators constituting the total number of the piezoelectric resonator and said additional piezoelectric resonator constituting the first and second series piezoelectric resonator, parity is characterized the same der Turkey, The filter according to claim 3 . A filter using a plurality of piezoelectric resonators in its configuration,
Between the input and output terminals, the first to third series piezoelectric resonators connected in succession in series,
A first parallel piezoelectric resonator having one electrode connected to one terminal connected to an input terminal of the first series piezoelectric resonator;
A second parallel piezoelectric resonator having one electrode connected to the other terminal of the first series piezoelectric resonator and one terminal of the second series piezoelectric resonator;
A third parallel piezoelectric resonator having one electrode connected to the other terminal of the second series piezoelectric resonator and one terminal of the third series piezoelectric resonator;
A fourth parallel piezoelectric resonators the third contrast to the connected second terminal to the output terminal of the series piezoelectric resonator having electrodes connected,
A first inductor connecting between the other electrode of the first parallel piezoelectric resonator and the ground;
A second inductor connecting between the other electrode of the second parallel piezoelectric resonator and the ground;
A third inductor connecting between the other electrode of the third parallel piezoelectric resonator and the ground;
A fourth inductor connecting between the other electrode of the fourth parallel piezoelectric resonator and the ground;
A first additional piezoelectric resonator which connects between the other electrode of the first parallel piezoelectric resonator of the other electrode and the parallel piezoelectric resonator of the first n (one of n = 2 to 4),
Characterized in that it is constituted by a second additional piezoelectric resonator for connecting the other electrode of the two parallel piezoelectric resonators other than the first and second n, filters.   2. The filter according to claim 1, wherein the series piezoelectric resonator, the parallel piezoelectric resonator, and the additional piezoelectric resonator are constituted by thin film elastic wave resonators. The filter according to claim 6 , wherein the thin-film acoustic wave resonator has a configuration in which a piezoelectric layer is sandwiched between an upper electrode and a lower electrode, and a cavity is provided below the lower electrode. The thin film acoustic wave resonator includes an acoustic multilayer film formed by sandwiching a piezoelectric layer between an upper electrode and a lower electrode and alternately laminating a low impedance layer and a high impedance layer under the lower electrode. The filter according to claim 6 , wherein the filter is provided. The series piezoelectric resonators, the parallel piezoelectric resonators and the additional piezoelectric resonator, characterized in that the electrodes are connected between the piezoelectric resonators adjacent to each other in the equivalent circuit in the same wiring layer, claim 7 The filter described in. The series piezoelectric resonators, the parallel piezoelectric resonators and the additional piezoelectric resonator, characterized in that the electrodes are connected between the piezoelectric resonators adjacent to each other in the equivalent circuit in the same wiring layer, claim 8 The filter described in.   2. The filter according to claim 1, wherein the series piezoelectric resonator, the parallel piezoelectric resonator, and the additional piezoelectric resonator are configured by surface acoustic wave resonators. 12. The filter according to claim 11 , wherein the surface acoustic wave resonator has a configuration in which an interdigital transducer electrode and a reflector electrode are arranged close to each other in a propagation direction on a piezoelectric substrate.

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