JP6909007B2 - Filter circuits, multiplexers and modules - Google Patents

Description

The present invention relates to filter circuits, multiplexers and modules, such as filter circuits, multiplexers and modules having elastic wave resonators.

As the low-pass filter (LPF) and high-pass filter (HPF), a filter combining an inductor and a capacitor (that is, an LC filter) is used. The LC filter is configured by, for example, laminating ceramic layers. It is known to connect a capacitor and an inductor to an elastic wave filter (for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2010-411141

In the LC filter, there is a trade-off relationship between the steepness of the cutoff characteristic between the pass band and the stop band and the insertion loss in the pass band. Therefore, if the insertion loss of the desired pass band is secured, the steepness of the cutoff characteristic deteriorates.

The present invention has been made in view of the above problems, and an object of the present invention is to enhance the steepness of the blocking characteristics.

The present invention comprises a substrate, an elastic wave resonator mounted on the substrate and connected in series between an input terminal and an output terminal, and a first node between the input terminal and the elastic wave resonator. One end is connected to the first element, which is either a capacitor or an inductor, and one end is connected to a second node between the elastic wave resonator and the output terminal, and the first of the capacitors and the inductor is described. The second element, which is the same as the element, is connected to the third node, one end of which is commonly connected to the other end of the first element and the other end of the second element, and the other end is connected to the ground terminal. The first element, the second element, and the third element, which are different from the first element and the second element among the capacitors and inductors, are the elastic wave resonator. The first attenuation pole, which is mounted on the substrate as a separate component to form a series resonance circuit and is mainly formed by the anti-resonance frequency of the elastic wave resonator, has a passing band and mainly the series resonance. It is a filter circuit located between the second attenuation pole formed by the resonance frequency of the circuit.

In the above configuration, the first attenuation pole and the second attenuation pole is rather the frequency is higher than the pass band, the filter circuit may be configured to be low pass filters.

In the above configuration, the first attenuation pole and the second attenuation pole is rather low frequency than the pass band, the filter circuit may be configured to be a high pass filter.

In the above configuration, a matching circuit may be provided at least one of the input terminal and the first node and the second node and the output terminal.

In the above configuration, the elastic wave resonator may include a plurality of elastic wave resonators connected in series or in parallel between the first node and the second node.

In the above configuration, the elastic wave resonator may be configured to include an IDT.

In the above configuration, the elastic wave resonator may include a piezoelectric thin film resonator.

The present invention is a multiplexer having the above filter circuit.

The present invention is a module having the above filter circuit.

According to the present invention, the steepness of the blocking characteristic can be enhanced.

FIG. 1A is a circuit diagram of an LPF according to Comparative Example 1, FIG. 1B is a diagram showing passage characteristics, and FIG. 1C is a Smith chart showing reflection characteristics. FIG. 2A is a circuit diagram of the HPF according to Comparative Example 1, FIG. 2B is a diagram showing passage characteristics, and FIG. 2C is a Smith chart showing reflection characteristics. FIG. 3A is a plan view of the surface acoustic wave resonator, and FIG. 3B is a cross-sectional view of the piezoelectric thin film resonator. FIG. 4A is a circuit diagram of the LPF according to Comparative Example 2, FIG. 4B is a diagram showing passage characteristics, and FIG. 4C is a Smith chart showing reflection characteristics. 5 (a) is a circuit diagram of the HPF according to Comparative Example 2, FIG. 5 (b) is a diagram showing passage characteristics, and FIG. 5 (c) is a Smith chart showing reflection characteristics. 6 (a) is a circuit diagram of the LPF according to the first embodiment, FIG. 6 (b) is a diagram showing passage characteristics, and FIG. 6 (c) is a Smith chart showing reflection characteristics. FIG. 7A is a circuit diagram of the LPF according to the first modification of the first embodiment, FIG. 7B is a diagram showing the passage characteristics, and FIG. 7C is a Smith chart showing the reflection characteristics. 8 (a) is a circuit diagram of the LPF according to the second modification of the first embodiment, FIG. 8 (b) is a diagram showing the passage characteristics, and FIG. 8 (c) is a Smith chart showing the reflection characteristics. 9 (a) is a circuit diagram of the LPF according to the third modification of the first embodiment, FIG. 9 (b) is a diagram showing the passage characteristics, and FIG. 9 (c) is a Smith chart showing the reflection characteristics. 10 (a) is a circuit diagram of an LPF according to a modified example 4 of the first embodiment, FIG. 10 (b) is a diagram showing a passage characteristic, and FIG. 10 (c) is a Smith chart showing a reflection characteristic. 11 (a) is a circuit diagram of the LPF according to the fifth modification of the first embodiment, FIG. 11 (b) is a diagram showing the passage characteristics, and FIG. 11 (c) is a Smith chart showing the reflection characteristics. 12 (a) is a circuit diagram of the HPF according to the second embodiment, FIG. 12 (b) is a diagram showing passage characteristics, and FIG. 12 (c) is a Smith chart showing reflection characteristics. 13 (a) is a circuit diagram of the HPF according to the first modification of the second embodiment, FIG. 13 (b) is a diagram showing the passage characteristics, and FIG. 13 (c) is a Smith chart showing the reflection characteristics. 14 (a) is a circuit diagram of the HPF according to the second modification of the second embodiment, FIG. 14 (b) is a diagram showing the passage characteristics, and FIG. 14 (c) is a Smith chart showing the reflection characteristics. FIG. 15 is a circuit diagram of the diplexer according to the third embodiment. FIG. 16 is a circuit diagram of a front-end circuit including the module according to the fourth embodiment. 17 (a) to 17 (c) are cross-sectional views of the module according to the fourth embodiment.

[Comparative Example 1]
Comparative Example 1 is an example of an LC filter. FIG. 1A is a circuit diagram of an LPF according to Comparative Example 1, FIG. 1B is a diagram showing passage characteristics, and FIG. 1C is a Smith chart showing reflection characteristics. As shown in FIG. 1A, the inductor L01 and the capacitor C01 are connected in parallel between the terminals T1 and T2. The inductor L01 and the capacitor C01 form a parallel resonant circuit. The capacitor C02 is connected between the node N1 between the terminal T1 and the inductor L01 and the capacitor C01 and the ground terminal (ground). The capacitor C03 is connected between the node N2 between the inductor L01 and the capacitor C01 and the terminal T2 and the ground terminal.

The passage characteristic S21 from the terminals T1 to T2 and the reflection characteristic S11 from the terminal T1 were simulated. The simulation conditions of FIGS. 1 (b) and 1 (c) are as follows.
Terminals T1, T2: 50Ω termination C01: 3.1pF
C02: 1.2pF
C03: 1.2pF
L01: 1.2nH

In FIGS. 1 (b) and 1 (c), the frequency with the highest S21 is shown in m1, and the frequency at the bottom of the attenuation pole higher than the frequency m1 and closest to m1 is shown in m2. The same applies to the following LPF. The magnitude of S21 and the magnitude / angle of S11 at frequencies m1 and m2 are as follows.
Frequency m1 = 2.250GHz, S21 = -0.35dB, S11 = 0.28 / -7 °
Frequency m2 = 2.610GHz, S21 = -59.2dB, S11 = 1.0 / -89 °

At frequency m1, S21 is large (ie, loss is small) and S11 is located approximately in the center of the Smith chart. That is, the high frequency signal input from the terminal T1 is hardly reflected and attenuated by the LPF and is output from the terminal T2. At the frequency m2, S21 is small (that is, the attenuation is large), and the magnitude of S11 is almost 1. That is, the high frequency signal input from the terminal T1 is hardly reflected or attenuated by the LPF, and is hardly output from the terminal T2. The difference between the frequencies m1 and m2 is 360 MHz.

FIG. 2A is a circuit diagram of the HPF according to Comparative Example 1, FIG. 2B is a diagram showing passage characteristics, and FIG. 2C is a Smith chart showing reflection characteristics. As shown in FIG. 2A, capacitors C04 and C05 are connected in series between terminals T1 and T2. The inductor L02 and the capacitor C06 are connected in series between the node N01 between the capacitors C04 and C05 and the ground terminal. The inductor L02 and the capacitor C06 form a series resonant circuit.

The simulation conditions of FIGS. 2 (a) and 2 (b) are as follows.
Terminals T1, T2: 50Ω termination C04: 1.5pF
C05: 1.5pF
C06: 1.0pF
L02: 8nH

In FIGS. 2 (b) and 2 (c), the frequency with the highest S21 is shown in m1, and the frequency at the bottom of the attenuation pole lower than the frequency m1 and closest to m1 is shown in m2. The same applies to the following HPF. The magnitude of S21 and the magnitude / angle of S11 at frequencies m1 and m2 are as follows.
Frequency m1 = 2.250GHz, S21 = -0.13dB, S11 = 0.17 / -174 °
Frequency m2 = 1.780GHz, S21 = -60.1dB, S11 = 1.0 / -80 °
The difference between the frequencies m1 and m2 is 470 MHz.

As in Comparative Example 1, in the LC filter, the frequency between the frequencies m1 and m2 is several hundreds of MHz, and the blocking characteristic between the pass band and the blocking band is not steep. When the frequencies m1 and m2 are brought close to each other, S21 at the frequency m1 becomes small (that is, the loss becomes large). As described above, in order to secure the insertion loss in the pass band, the steepness of the cutoff characteristic between the pass band and the blocking band cannot be improved.

[Comparative Example 2]
Comparative Example 2 is an example in which a capacitor other than the LC resonance circuit in Comparative Example 1 is replaced with an elastic wave resonator. Examples of elastic wave resonators used in Comparative Examples and Examples will be described. FIG. 3A is a plan view of the surface acoustic wave resonator, and FIG. 3B is a cross-sectional view of the piezoelectric thin film resonator. As shown in FIG. 3A, an IDT (Interdigital Transducer) 51 and a reflector 52 are formed on the piezoelectric substrate 50. The IDT 51 has a pair of comb-shaped electrodes 51a facing each other. The comb-shaped electrode 51a has a plurality of electrode fingers 51b and a bus bar 51c for connecting the plurality of electrode fingers 51b. Reflectors 52 are provided on both sides of the IDT 51. The IDT 51 excites a surface acoustic wave on the piezoelectric substrate 50. The piezoelectric substrate 50 is, for example, a lithium tantalate substrate or a lithium niobate substrate. The IDT 51 and the reflector 52 are formed of, for example, an aluminum film or a copper film. The piezoelectric substrate 50 may be bonded to the lower surface of a support substrate such as a sapphire substrate, an alumina substrate, a spinel substrate, or a silicon substrate. A protective film or a temperature compensation film may be provided to cover the IDT 50 and the reflector 52.

As shown in FIG. 3B, the piezoelectric film 57 is provided on the substrate 55. The lower electrode 56 and the upper electrode 58 are provided so as to sandwich the piezoelectric film 57. A gap 59 is formed between the lower electrode 56 and the substrate 55. The lower electrode 56 and the upper electrode 58 excite elastic waves in the thickness longitudinal vibration mode in the piezoelectric film 57. The lower electrode 56 and the upper electrode 58 are metal films such as a ruthenium film. The piezoelectric film 57 is, for example, an aluminum nitride film. The substrate 55 is, for example, a silicon substrate, a sapphire substrate, an alumina substrate, a spinel substrate, or a glass substrate.

FIG. 4A is a circuit diagram of the LPF according to Comparative Example 2, FIG. 4B is a diagram showing passage characteristics, and FIG. 4C is a Smith chart showing reflection characteristics. As shown in FIG. 4A, the capacitors C02 and C03 are replaced with elastic wave resonators R01 and R02 as compared with FIG. 1A of Comparative Example 1. Other configurations are the same as those of the LPF of Comparative Example 1, and the description thereof will be omitted.

The simulation conditions of FIGS. 4 (b) and 4 (c) are as follows.
Terminals T1, T2: 50Ω termination C01: 3.0pF
L01: 1.5nH
R01, R02: The simulation was carried out with a piezoelectric thin film resonator having a resonance frequency of 2.26 GHz and an antiresonance frequency of 2.33 GHz.

As shown in FIG. 4B, the frequency at the bottom of the attenuation pole A01 formed mainly by the anti-resonance frequencies of the elastic wave resonators R01 and R02 is m2. The attenuation pole A02 formed by the resonance frequency of the parallel resonant circuit formed by the inductor L01 and the capacitor C01 is formed on the high frequency side of the attenuation pole A01.

In FIGS. 4 (b) and 4 (c), the size of S21 and the size / angle of S11 at frequencies m1 and m2 are as follows.
Frequency m1 = 1.900GHz, S21 = -0.46dB, S11 = 0.00 / 107 °
Frequency m2 = 2.260GHz, S21 = -64.8dB, S11 = 0.96 / 176 °
The difference between the frequencies m1 and m2 is 360 MHz.

5 (a) is a circuit diagram of the HPF according to Comparative Example 2, FIG. 5 (b) is a diagram showing passage characteristics, and FIG. 5 (c) is a Smith chart showing reflection characteristics. As shown in FIG. 5A, the capacitors C04 and C05 are replaced with elastic wave resonators R03 and R04 as compared with FIG. 2A of Comparative Example 1. Other configurations are the same as those of the HPF of Comparative Example 1, and the description thereof will be omitted.

The simulation conditions of FIGS. 5 (b) and 5 (c) are as follows.
Terminals T1, T2: 50Ω termination C06: 1.0pF
L02: 5.5nH
R03, R04: The simulation was carried out with a piezoelectric thin film resonator having a resonance frequency of 2.26 GHz and an antiresonance frequency of 2.33 GHz.

As shown in FIG. 5B, the frequency at the bottom of the attenuation pole A01 formed mainly by the antiresonance frequencies of the elastic wave resonators R03 and R04 is m2. The attenuation pole A02 formed by the resonance frequency of the series resonance circuit formed by the inductor L02 and the capacitor C06 is formed on the low frequency side of the attenuation pole A01.

In FIGS. 5 (b) and 5 (c), the size of S21 and the size / angle of S11 at frequencies m1 and m2 are as follows.
Frequency m1 = 2.900GHz, S21 = -0.41dB, S11 = 0.09 / -177 °
Frequency m2 = 2.33GHz, S21 = -60.3dB, S11 = 0.94 / -4 °
The difference between the frequencies m1 and m2 is 570 MHz.

Even if the resonance frequency or antiresonance frequency of the elastic wave resonator other than the LC resonance circuit is formed near the frequency m1 as in Comparative Example 2, the difference between the frequencies m1 and m2 is several hundred MHz. As described above, in order to secure the insertion loss in the pass band, the steepness of the cutoff characteristic between the pass band and the blocking band cannot be improved.

The first embodiment is an example of a filter circuit having an LPF function. 6 (a) is a circuit diagram of the LPF according to the first embodiment, FIG. 6 (b) is a diagram showing passage characteristics, and FIG. 6 (c) is a Smith chart showing reflection characteristics. As shown in FIG. 6A, elastic wave resonators R1a and R1b are connected in parallel between terminals T1 and T2. The elastic wave resonators R1a and R1b are 1-port resonators. The node N1 is a node between the terminal T1 and the elastic wave resonators R1a and R1b. The node N2 is a node between the elastic wave resonators R1a and R1b and the terminal T2. One end of the capacitor C1 is connected to the node N1, and one end of the capacitor C2 is connected to the node N2. The other end of the capacitor C1 and the other end of the capacitor C2 are commonly connected to the node N3. One end of the inductor L3 is connected to the node N3, and the other end is connected to the ground terminal. An LC series resonant circuit 10 in which the inductor L3 and the capacitors C1 and C2 are connected in series is formed between the nodes N1 and N2 and the ground terminal.

The simulation conditions of FIGS. 6 (b) and 6 (c) are as follows.
Terminals T1, T2: 50Ω termination C1: 0.2pF
C2: 0.2pF
L3: 9.1nH
R1a, R1b: A simulation was carried out with a piezoelectric thin film resonator having a resonance frequency of 2.26 GHz and an antiresonance frequency of 2.33 GHz.

As shown in FIG. 6B, the attenuation pole A1 formed mainly by the antiresonance frequencies of the elastic wave resonators R1a and R1b is formed. The attenuation pole A2 formed mainly by the resonance frequency of the LC series resonance circuit 10 is formed at the frequency m2 on the higher frequency side than the attenuation pole A1.

Since the attenuation pole A1 is mainly formed by the anti-resonance frequencies of the elastic wave resonators R1a and R1b, the breaking characteristic can be steep. When the damping poles A1 and A2 approach each other and the damping poles A1 and A2 form one damping pole with a minimum of one, the steepness of the damping pole A1 cannot be obtained. Therefore, it is preferable that the attenuation poles A1 and A2 each have a minimum.

In FIGS. 6 (b) and 6 (c), the size of S21 and the size / angle of S11 at frequencies m1 and m2 are as follows.
Frequency m1 = 2.300GHz, S21 = -0.33dB, S11 = 0.14 / -133 °
Frequency m2 = 2.340GHz, S21 = -21.7dB, S11 = 0.92 / -71 °

In Example 1, the loss at the frequency m1 is −0.33 dB, which is about the same as the LPF of Comparative Examples 1 and 2, and the difference between the frequencies m1 and m2 can be reduced to 40 MHz, which is nearly an order of magnitude smaller. In this way, the insertion loss of the pass band can be reduced and the steepness of the cutoff characteristic between the pass band and the blocking band can be improved.

[Modification 1 of Example 1]
Modification 1 of the first embodiment is an example in which the inductor and the capacitor of the LC series resonant circuit 10 are replaced. FIG. 7A is a circuit diagram of the LPF according to the first modification of the first embodiment, FIG. 7B is a diagram showing the passage characteristics, and FIG. 7C is a Smith chart showing the reflection characteristics. As shown in FIG. 7A, the capacitors C1, C2 and the inductor L3 are replaced with the inductors L1, L2 and the capacitor C3, respectively, as compared with the first embodiment. Other configurations are the same as those in the first embodiment, and the description thereof will be omitted.

The simulation conditions of FIGS. 7 (b) and 7 (c) are as follows.
Terminals T1, T2: 50Ω termination L1: 8.5nH
L2: 22nH
C1: 0.5pF
R1a, R1b: A simulation was carried out with a piezoelectric thin film resonator having a resonance frequency of 2.26 GHz and an antiresonance frequency of 2.33 GHz.

As shown in FIG. 7B, the attenuation poles A1 and A2 are formed as in the first embodiment. In FIGS. 7 (b) and 7 (c), the size of S21 and the size / angle of S11 at frequencies m1 and m2 are as follows.
Frequency m1 = 2.300GHz, S21 = -0.35dB, S11 = 0.20 / -86 °
Frequency m2 = 2.343GHz, S21 = -21.0dB, S11 = 0.93 / -78 °
The difference between the frequencies m1 and m2 is 43 MHz.

In the first modification of the first embodiment, even if the inductor and the capacitor of the LC series resonant circuit 10 are replaced, the insertion loss of the pass band can be reduced and the steepness of the cutoff characteristic between the pass band and the blocking band can be improved. ..

[Modification 2 of Example 1]
Modification 2 of the first embodiment is an example in which a matching circuit is provided. 8 (a) is a circuit diagram of the LPF according to the second modification of the first embodiment, FIG. 8 (b) is a diagram showing the passage characteristics, and FIG. 8 (c) is a Smith chart showing the reflection characteristics. As shown in FIG. 8A, a matching circuit 12 is provided between the terminal T1 and the elastic wave resonators R1a and R1b as compared with the first embodiment. The matching circuit 12 has a shunt-connected inductor L4. A matching circuit 14 is provided between the elastic wave resonators R1a and R1b and the terminal T2. The matching circuit 14 has a shunt-connected inductor L5. Other configurations are the same as those in the first embodiment, and the description thereof will be omitted.

The simulation conditions of FIGS. 8 (b) and 8 (c) are as follows.
Terminals T1, T2: 50Ω termination C1: 0.22pF
C2: 0.22pF
L3: 8.7nH
L4: 9nH
L5: 9nH
R1a, R1b: A simulation was carried out with a piezoelectric thin film resonator having a resonance frequency of 2.26 GHz and an antiresonance frequency of 2.33 GHz.

As shown in FIG. 8 (b), the attenuation poles A1 and A2 are formed as in the first embodiment. In FIGS. 8 (b) and 8 (c), the size of S21 and the size / angle of S11 at frequencies m1 and m2 are as follows.
Frequency m1 = 2.300GHz, S21 = -0.19dB, S11 = 0.04 / -102 °
Frequency m2 = 2.345GHz, S21 = -21.0dB, S11 = 0.91 / -60 °
The difference between the frequencies m1 and m2 is 45 MHz.

In the second modification of the first embodiment, the insertion loss in the pass band can be made smaller than that of the first embodiment by providing the matching circuits 12 and 14. Moreover, the pass band can be widened.

[Modification 3 of Example 1]
In the third modification of the first embodiment, the elastic wave resonator is one example. 9 (a) is a circuit diagram of the LPF according to the third modification of the first embodiment, FIG. 9 (b) is a diagram showing the passage characteristics, and FIG. 9 (c) is a Smith chart showing the reflection characteristics. As shown in FIG. 9A, one elastic wave resonator R1 is provided as compared with the first embodiment. Other configurations are the same as those in the first embodiment, and the description thereof will be omitted.

The simulation conditions of FIGS. 9 (b) and 9 (c) are as follows.
Terminals T1, T2: 50Ω termination C1: 0.2pF
C2: 0.2pF
L3: 9.1nH
R1: The simulation was carried out with a piezoelectric thin film resonator having a resonance frequency of 2.26 GHz and an antiresonance frequency of 2.33 GHz.

As shown in FIG. 9B, the attenuation poles A1 and A2 are formed as in the first embodiment. In FIGS. 9 (b) and 9 (c), the size of S21 and the size / angle of S11 at frequencies m1 and m2 are as follows.
Frequency m1 = 2.300GHz, S21 = -0.51dB, S11 = 0.19 / 5 °
Frequency m2 = 2.340GHz, S21 = -14.6dB, S11 = 0.93 / -59 °
The difference between the frequencies m1 and m2 is 40 MHz.

As in the modified example 3 of the first embodiment, even if one elastic wave resonator is used, the same degree of insertion loss and steepness as in the first embodiment can be realized.

[Modified Example 4 of Example 1]
In the modified example 4 of the first embodiment, there are three examples of elastic wave resonators. 10 (a) is a circuit diagram of an LPF according to a modified example 4 of the first embodiment, FIG. 10 (b) is a diagram showing a passage characteristic, and FIG. 10 (c) is a Smith chart showing a reflection characteristic. As shown in FIG. 10A, three elastic wave resonators R1a to R1c are provided in parallel as compared with the first embodiment. Other configurations are the same as those in the first embodiment, and the description thereof will be omitted.

The simulation conditions of FIGS. 10 (b) and 10 (c) are as follows.
Terminals T1, T2: 50Ω termination C1: 0.2pF
C2: 0.2pF
L3: 9.1nH
R1a, R1b, R1c: A simulation was carried out with a piezoelectric thin film resonator having a resonance frequency of 2.26 GHz and an antiresonance frequency of 2.33 GHz.

As shown in FIG. 10B, the attenuation poles A1 and A2 are formed in the same manner as in the first embodiment. In FIGS. 10 (b) and 10 (c), the size of S21 and the size / angle of S11 at frequencies m1 and m2 are as follows.
Frequency m1 = 2.300GHz, S21 = -0.49dB, S11 = 0.27 / -133 °
Frequency m2 = 2.340GHz, S21 = -13.9dB, S11 = 0.90 / -80 °
The difference between the frequencies m1 and m2 is 40 MHz.

As in the modified example 4 of the first embodiment, even if three elastic wave resonators are used, the same degree of insertion loss and steepness as in the first embodiment can be realized.

[Modification 5 of Example 1]
Modification 5 of Example 1 is an example in which the capacitances of the capacitors C1 and C2 are different. 11 (a) is a circuit diagram of the LPF according to the fifth modification of the first embodiment, FIG. 11 (b) is a diagram showing the passage characteristics, and FIG. 11 (c) is a Smith chart showing the reflection characteristics. As shown in FIG. 11A, the circuit diagram of the modified example 5 of the first embodiment is the same as that of the first embodiment, and the description thereof will be omitted.

The simulation conditions of FIGS. 11 (b) and 11 (c) are as follows.
Terminals T1, T2: 50Ω termination C1: 0.15pF
C2: 0.25pF
L3: 9.1nH
R1a, R1b: A simulation was carried out with a piezoelectric thin film resonator having a resonance frequency of 2.26 GHz and an antiresonance frequency of 2.33 GHz.

As shown in FIG. 11B, the attenuation poles A1 and A2 are formed as in the first embodiment. In FIGS. 11 (b) and 11 (c), the size of S21 and the size / angle of S11 at frequencies m1 and m2 are as follows.
Frequency m1 = 2.300GHz, S21 = -0.38dB, S11 = 0.15 / -173 °
Frequency m2 = 2.340GHz, S21 = -21.0dB, S11 = 0.91 / -58 °
The difference between the frequencies m1 and m2 is 40 MHz.

As in the modified example 5 of the first embodiment, even if the capacitances of the capacitors C1 and C2 are different, the same degree of insertion loss and steepness as in the first embodiment can be realized.

The second embodiment is an example of a filter circuit having a function of HPF. 12 (a) is a circuit diagram of the HPF according to the second embodiment, FIG. 12 (b) is a diagram showing passage characteristics, and FIG. 12 (c) is a Smith chart showing reflection characteristics. As shown in FIG. 12A, elastic wave resonators R1a to R1c are connected in series between terminals T1 and T2. Other configurations are the same as those in the first embodiment, and the description thereof will be omitted.

The simulation conditions of FIGS. 12 (b) and 12 (c) are as follows.
Terminals T1, T2: 50Ω termination C1: 0.5pF
C2: 0.5pF
L3: 4.7nH
R1a, R1b, R1c: A simulation was carried out with a piezoelectric thin film resonator having a resonance frequency of 2.26 GHz and an antiresonance frequency of 2.33 GHz.

As shown in FIG. 12B, the attenuation pole A1 formed mainly from the antiresonance frequencies of the elastic wave resonators R1a to R1c is formed at the frequency m2. The attenuation pole A2 formed mainly from the resonance frequency of the LC series resonance circuit 10 is formed on the low frequency side of the attenuation pole A1.

In FIGS. 12 (b) and 12 (c), the size of S21 and the size / angle of S11 at frequencies m1 and m2 are as follows.
Frequency m1 = 2.300GHz, S21 = -0.26dB, S11 = 0.03 / 180 °
Frequency m2 = 2.255GHz, S21 = -20.3dB, S11 = 0.96 / -167 °

In Example 2, the loss at the frequency m1 is −0.26 dB, which is about the same as the HPF of Comparative Examples 1 and 2, and the difference between the frequencies m1 and m2 can be reduced to 45 MHz, which is nearly an order of magnitude smaller. In this way, the insertion loss of the pass band can be reduced and the steepness of the cutoff characteristic between the pass band and the blocking band can be improved.

[Modification 1 of Example 2]
Modification 1 of the second embodiment is an example in which a matching circuit is provided. 13 (a) is a circuit diagram of the HPF according to the first modification of the second embodiment, FIG. 13 (b) is a diagram showing the passage characteristics, and FIG. 13 (c) is a Smith chart showing the reflection characteristics. As shown in FIG. 13A, a matching circuit 12 is provided between the terminal T1 and the elastic wave resonator R1a as compared with the second embodiment. The matching circuit 12 has a shunt-connected inductor L4. A matching circuit 14 is provided between the elastic wave resonator R1c and the terminal T2. The matching circuit 14 has a shunt-connected inductor L5. Other configurations are the same as those in the second embodiment, and the description thereof will be omitted.

The simulation conditions of FIGS. 13 (b) and 13 (c) are as follows.
Terminals T1, T2: 50Ω termination C1: 1.3pF
C2: 1.3pF
L3: 1.2nH
L4: 1.6nH
L5: 1.6nH
R1a, R1b, R1c: A simulation was carried out with a piezoelectric thin film resonator having a resonance frequency of 2.26 GHz and an antiresonance frequency of 2.33 GHz.

As shown in FIG. 13B, the attenuation poles A1 and A2 are formed as in the second embodiment. In FIGS. 13 (b) and 13 (c), the size of S21 and the size / angle of S11 at frequencies m1 and m2 are as follows.
Frequency m1 = 2.280GHz, S21 = -0.10dB, S11 = 0.02 / -105 °
Frequency m2 = 2.200GHz, S21 = -21.0dB, S11 = 0.91 / 4 °
The difference between the frequencies m1 and m2 is 80 MHz.

In the first modification of the second embodiment, the insertion loss in the pass band can be made smaller than that of the second embodiment by providing the matching circuits 12 and 14. Moreover, the pass band can be widened.

[Modification 2 of Example 2]
Modification 2 of the second embodiment is an example in which a plurality of elastic wave resonators are provided in parallel. 14 (a) is a circuit diagram of the HPF according to the second modification of the second embodiment, FIG. 14 (b) is a diagram showing the passage characteristics, and FIG. 14 (c) is a Smith chart showing the reflection characteristics. As shown in FIG. 14A, the circuit diagram of the modified example 2 of the second embodiment is the same as that of the first embodiment, and the description thereof will be omitted.

The simulation conditions of FIGS. 14 (b) and 14 (c) are as follows.
Terminals T1, T2: 50Ω termination C1: 0.4pF
C2: 0.4pF
L3: 8.2nH
R1a, R1b: A simulation was carried out with a piezoelectric thin film resonator having a resonance frequency of 2.26 GHz and an antiresonance frequency of 2.33 GHz.

As shown in FIG. 14 (b), the attenuation poles A1 and A2 are formed as in the second embodiment. In FIGS. 14 (b) and 14 (c), the size of S21 and the size / angle of S11 at frequencies m1 and m2 are as follows.
Frequency m1 = 2.360GHz, S21 = -0.33dB, S11 = 0.04 / 88 °
Frequency m2 = 2.313GHz, S21 = -21.2dB, S11 = 0.91 / 73 °
The difference between the frequencies m1 and m2 is 47 MHz.

The same HPF as in the second embodiment can be realized even if a plurality of elastic wave resonators R1a and R1b are provided in parallel as in the second modification of the second embodiment.

According to Examples 1 and 2 and a modification thereof, an elastic wave resonator is connected in series between the terminal T1 (input terminal) and the terminal T2 (output terminal). An LC direct resonant circuit is connected between the nodes N1 and N2 and the ground terminal. Here, as an element forming the LC series resonant circuit 10, a capacitor C1 or an inductor L1 having one end connected to a node N1 (first node) and the other end connected to a node N3 (third node) is used as the first element. The second element is a capacitor C2 or an inductor L2 whose one end is connected to the node N2 (second node) and the other end is connected to the node N3. An inductor L3 or a capacitor C3 having one end connected to the node N3 and the other end connected to the ground terminal is used as the third element. In order for the first element to the third element to form the LC series resonant circuit 10, the first element and the second element are required to form the LC series resonant circuit 10, as in the first and second modified examples 2 to 5 and the second and second modified examples thereof. When the capacitors are C1 and C2, respectively, the second element is the inductor L3. When the first element and the second element are inductors L1 and L2, respectively, as in the first modification of the first embodiment, the third element becomes the capacitor C3.

As a result, as in Examples 1 and 2 and its modifications, the insertion loss at the frequency m1 (passband) is about the same as that of Comparative Examples 1 and 2, and the cutoff characteristic between the passband and the blocking band is steep. Can improve sex.

As in the first embodiment and its modifications, the attenuation pole A2 formed by the first element, the second element, and the third element has a higher frequency than the attenuation pole A1 formed by the elastic wave resonator. This makes it possible to realize a filter circuit that functions as an LPF.

As in the second embodiment, the attenuation pole A2 formed by the first element, the second element, and the third element has a lower frequency than the attenuation pole A1 formed by the elastic wave resonator. As a result, a filter circuit that functions as an HPF can be realized.

A bandpass filter may be formed by combining LPF and HPF.

The attenuation pole A1 is mainly formed by the anti-resonance frequencies of the elastic wave resonators R1, R1a to R1c. However, it is affected by the LC series resonant circuit 10 and the like. Therefore, the frequency at the bottom of the attenuation pole A1 is different from the antiresonance frequency when the elastic wave resonators R1, R1a to R1c are alone. The attenuation pole A2 is mainly formed from the LC series resonant circuit 10. However, it is affected by the elastic wave resonators R1a to R1c. Therefore, the frequency at the bottom of the attenuation pole A2 is different from the resonance frequency when the LC series resonant circuit 10 is alone.

Since the attenuation pole A1 is mainly formed by the anti-resonance frequencies of the elastic wave resonators R1 and R1a to R1c, the steepness of the cutoff characteristic between the pass band and the blocking band can be improved. Further, since the attenuation poles A1 and A2 have different minimums, the steepness of the cutoff characteristic can be further improved. Further, the attenuation pole A2 can increase the amount of attenuation in the blocking band.

As in Example 1 and its modifications 2 to 4 and Example 2 and its modifications, the capacitances of the capacitors C1 and C2 may be substantially the same as each other. The inductances of the inductors L1 and L2 may be substantially the same as each other. That is, the reactance of the first element and the reactance of the second element may be substantially equal.

As in the first modification of the first embodiment, the inductances of the inductors L1 and L2 may be different from each other. As in the modified example 5 of the first embodiment, the capacitances of the capacitors C1 and C2 may be different from each other. That is, the reactance of the first element and the reactance of the second element may be different from each other.

In addition to the LC series resonant circuit 10, another LC series resonant circuit having a resonance frequency different from that of the LC series resonant circuit 10 may be provided between the nodes N1 and / or N2 and the ground terminal. As a result, the blocking band can be widened.

As in the modified example 3 of the first embodiment, the number of elastic wave resonators R1 connected in series between the nodes N1 and N2 may be one. Even if a plurality of elastic wave resonators R1a to R1c are connected in series between the nodes N1 and N2 as in the first embodiment and the modified examples 1, 2, 4, 5 and the modified example 2 of the second embodiment. good.

As in the second embodiment and the first modification thereof, a plurality of elastic wave resonators R1a to R1c may be connected in parallel between the node N1 and the node N2.

When a plurality of elastic wave resonators R1a to R1c are provided, the antiresonance frequencies of the plurality of elastic wave resonators R1a to R1c may all be substantially equal. At least one anti-resonant frequency of the plurality of elastic wave resonators R1a to R1c may be different from the anti-resonant frequency of the other elastic wave resonators. By making the anti-resonance frequencies of the elastic wave resonators R1a to R1c different, the blocking band can be widened.

Even if a matching circuit is provided at least one of the space between the terminal T1 and the node N1 and the space between the node N2 and the terminal T2 as in the modified example 2 of the first embodiment and the modified example 1 of the second embodiment. good. As a result, the insertion loss of the pass band can be suppressed and the pass band can be widened.

The elastic wave resonators R1, R1a to R1c may include an IDT as shown in FIG. 3A, or may include a piezoelectric thin film resonator as shown in FIG. 3B.

When the elastic wave resonator is a piezoelectric thin film resonator, two elastic wave resonators R1a and R1b are provided in series or in parallel between the nodes N1 and N2. The capacitance, resonance frequency and antiresonance frequency of the elastic wave resonators R1a and R1b are made substantially equal. Further, the polarization directions of the piezoelectric films of the elastic wave resonators R1a and R1b are opposite to each other when viewed from the nodes N1 or N2. As a result, the second harmonics generated by the elastic wave resonators R1a and R1b can be suppressed.

FIG. 15 is a circuit diagram of the diplexer according to the third embodiment. As shown in FIG. 15, the LPF60 is connected between the common terminal Ant and the terminal TL. The HPF62 is connected between the common terminal Ant and the terminal TH. LPF60 is used as a filter circuit of Example 1 and a modified example thereof, and HPF62 is used as a filter circuit of Example 2 and a modified example thereof. Thereby, the steepness of the blocking characteristics of LPF60 and HPF62 can be improved. Therefore, demultiplexing with a narrow band interval becomes possible. Either LPF60 or HPF62 may be used as the filter circuit of Example 1 or Example 2. By combining the filter circuits of Examples 1 and 2 and the modified examples thereof, a multiplexer such as a duplexer, a triplexer, or a quadplexer can be realized in addition to the diplexer. This enables demultiplexing with narrow band spacing, such as in systems where carrier aggregation or MIMO (Multiple-Input and Multiple-Output) is used.

FIG. 16 is a circuit diagram of a front-end circuit including the module according to the fourth embodiment. As shown in FIG. 16, the common terminal Ant of the diplexer 30 is connected to the antenna 42. The terminals TL and TH of the diplexer 30 are connected to the duplexer 34 via a switch 32, respectively. The RX terminal of the duplexer 34 is connected to the RFIC (Radio Frequency Integrated Circuit) 40 (broken line). The TX terminal of the duplexer 34 is connected to the RFIC (Radio Frequency Integrated Circuit) 40 via the switch 36 and the power amplifier 38 (solid line).

The power amplifier 38 amplifies the transmission signal output from the RFIC 40. The switch 36 outputs the amplified transmission signal to any one transmission terminal of one or a plurality of duplexers 34. The duplexer 34 outputs a signal in the transmission band among the high frequency signals input to the transmission terminal to the switch 32 and suppresses signals of other frequencies. The duplexer 34 outputs a signal in the reception band among the high frequency signals input from the switch 32 to the RFIC 40 and suppresses signals of other frequencies. The RFIC 40 includes a low noise amplifier and amplifies signals in the reception band.

The switch 32 connects any one of one or more duplexers 34 to the terminal TL or TH. The diplexer 30 causes the common terminal Ant to output or input a low-band signal input or output to the terminal TL, and does not input or output a high-band signal to the terminal TL.

The diplexer 30 causes the low band input or output to the terminal TL to output or input a signal to the common terminal Ant, and does not input or output the high band signal to the terminal TL. The diplexer 30 causes a high band input or output to the terminal TH to output or input a signal to the common terminal Ant, and does not input or output a low band signal to the terminal TH.

In FIG. 16, the diplexer 30 can be the diplexer of the third embodiment. Further, the filter included in the duplexer 34 can be used as a filter circuit of Examples 1 and 2 and a modification thereof.

17 (a) to 17 (c) are cross-sectional views of the module according to the fourth embodiment. As shown in FIG. 17A, the elastic wave resonator 22, the laminated filter 24, and the chip component 26 are mounted on the printed circuit board 20. A resin sealing portion 28 is provided on the printed circuit board 20 so as to cover the elastic wave resonator 22, the laminated filter 24, and the chip component 26. The printed circuit board 20 is a substrate in which wiring is formed on an insulating substrate such as glass epoxy resin. The resin sealing portion 28 is a mold resin such as an epoxy resin.

The elastic wave resonator 22 is provided with at least a part of filters of the elastic wave resonators R1, R1a to R1c, and / or the duplexer 34 in Examples 1 and 2 and their modifications. The multilayer filter 24 is provided with at least a part of the LC series resonant circuit 10 of Examples 1 and 2 and a modification thereof, and / or at least a part of the diplexer 30 and the duplexer 34. The chip component 26 is at least a part of the capacitors and inductors of the LC series resonant circuit 10 and / or the diplexer 30 of Examples 1 and 2 and variations thereof.

As shown in FIG. 17B, a ceramic substrate 20a such as LTCC (Low Temperature Co-fired Ceramic) or HTCC (High Temperature Co-fired Ceramic) may be used instead of the printed circuit board 20. Other configurations are the same as those in FIG. 17A, and the description thereof will be omitted.

As shown in FIG. 17 (c), the laminated filter 24 may not be provided. Other configurations are the same as those in FIG. 17B, and the description thereof will be omitted.

The module may include at least one of the diplexer 30 and duplexer 34 of FIG.

Although the examples of the present invention have been described in detail above, the present invention is not limited to such specific examples, and various modifications and modifications are made within the scope of the gist of the present invention described in the claims. It can be changed.

10 LC series resonant circuit 12, 14 matching circuit

Claims (11)

With the board
An elastic wave resonator mounted on the substrate and connected in series between the input terminal and the output terminal,
A first element, one end of which is connected to a first node between the input terminal and the elastic wave resonator and is either a capacitor or an inductor,
One end is connected to the second node between the elastic wave resonator and the output terminal, and the second element of the capacitor and the inductor, which is the same as the first element, and
One end is connected to a third node in which the other end of the first element and the other end of the second element are commonly connected, and the other end is connected to a ground terminal. The third element, which is the other element different from the second element,
Equipped with
The first element, the second element, and the third element are mounted on the substrate as components separate from the elastic wave resonator to form a series resonant circuit.
The first decay pole formed mainly by the anti-resonance frequency of the elastic wave resonator is a filter located between the pass band and the second decay pole formed mainly by the resonance frequency of the series resonance circuit. circuit. Wherein the first attenuation pole and the second attenuation pole is rather the frequency is higher than the pass band, the filter circuit is a filter circuit according to claim 1, wherein a low-pass filter. Wherein the first attenuation pole and the second attenuation pole is rather low frequency than the pass band, the filter circuit is a filter circuit according to claim 1, wherein the high-pass filter. The filter circuit according to any one of claims 1 to 3, wherein a matching circuit is provided between the input terminal and the first node and between the second node and the output terminal. The filter circuit according to any one of claims 1 to 4, wherein the elastic wave resonator includes a plurality of elastic wave resonators connected in series or in parallel between the first node and the second node. The filter circuit according to any one of claims 1 to 5, wherein the elastic wave resonator includes an IDT. The filter circuit according to any one of claims 1 to 5, wherein the elastic wave resonator includes a piezoelectric thin film resonator. A multiplexer having the filter circuit according to any one of claims 1 to 7. A module having the filter circuit according to any one of claims 1 to 7. The filter circuit according to any one of claims 1 to 7, wherein the first element and the second element are inductors, and the third element is a capacitor. The filter circuit according to any one of claims 1 to 7, wherein the first element and the second element are capacitors, and the third element is an inductor.

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