Bandpass filters and multiplexers

Abstract

To provide bandpass filters and multiplexers with improved power handling capabilities. [Solution] The bandpass filter comprises a piezoelectric substrate and a plurality of resonators formed on the piezoelectric substrate and arranged to constitute a bandpass filter. The plurality of resonators have IDT electrodes consisting of electrode layers provided on the piezoelectric substrate. The plurality of resonators include a first thickness h1, where the thickness of the electrode layer of the resonator is normalized by the wavelength λ, defined by the electrode finger pitch of the IDT electrodes, and a second thickness h2, where the thickness of the electrode layer of the resonator is thinner than the first thickness h1. Among the plurality of resonators, the thickness of the electrode layer of the resonator having the anti-resonant frequency closest to the high-frequency end of the bandpass filter's passband, which lies on the high-frequency side of the bandpass filter's passband, is configured to be the second thickness h2. The multiplexer also comprises this bandpass filter.

Description

Technical Field

[0001] The present invention relates to a band-pass filter and a multiplexer having a plurality of resonators.

Background Art

[0002] For example, as a duplexer of a mobile phone, a band-pass filter and a multiplexer using a plurality of SAW (Surface acoustic wave) resonators are known.

[0003] In Patent Document 1, in an elastic wave device including a plurality of IDT electrodes provided on a piezoelectric substrate and a dielectric film made of silicon oxide covering the plurality of IDT electrodes, the plurality of IDT electrodes are a first electrode layer mainly composed of one of Mo and W and a second electrode layer mainly composed of Cu, and by configuring the thickness of the first electrode layer and the thickness of the second electrode layer to satisfy a predetermined formula, while stably and effectively widening the specific band of the elastic wave device, the frequency temperature characteristics can be improved, and it is disclosed that the trade-off relationship between widening the specific band in a conventional elastic wave device and the frequency temperature characteristics can be improved.

[0004] Also, in Patent Document 2, a plurality of elastic wave elements provided on the same piezoelectric substrate and each having an electrode layer with a different thickness for each elastic wave element are disclosed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In bandpass filters and multiplexers using SAW resonators equipped with IDT electrodes on a piezoelectric substrate, it is necessary to improve the absolute value of the frequency-temperature characteristics of the resonator. If the absolute value of the frequency-temperature characteristics is large, fluctuations in the transmission characteristics due to temperature changes can cause loss by cutting off signals at frequencies that were originally intended to pass through. This increase in loss leads to heat generation and reduces the power handling capacity. To improve the frequency-temperature characteristics, it is conceivable to improve the frequency-temperature characteristics by thinning the thickness of the electrode layer, as in the SAW resonator (elastic wave device) of Patent Document 1. However, while thinning the electrode layer improves the frequency-temperature characteristics, it also reduces the capacitance per unit area in a plan view of the SAW resonator. Therefore, when the electrode layer of a SAW resonator is thinned, it is necessary to increase the area of ​​the electrode layer or electrodes in a plan view in order to increase the capacitance back to the original capacitance of the SAW resonator, which increases the area of ​​the SAW resonator in a plan view. Therefore, if the area of ​​all resonators included in the bandpass filter and multiplexer is increased in a plan view, there is a problem that the entire bandpass filter and multiplexer will become significantly larger.

[0007] The present invention has been made in view of the above problems, and aims to provide a bandpass filter and a multiplexer that can improve the temperature characteristics of the resonator, reduce losses, and improve power withstand capability while suppressing an increase in the size of the bandpass filter and multiplexer. [Means for solving the problem]

[0008] One embodiment of the bandpass filter of the present invention comprises a piezoelectric substrate and Multiple resonators formed on the piezoelectric substrate, Equipped with, The plurality of resonators each have an IDT electrode consisting of an electrode layer provided on the piezoelectric substrate, The plurality of resonators include a resonator whose electrode layer thickness is a first thickness h1 normalized by the wavelength λ defined by the electrode finger pitch of the IDT electrode, and a resonator whose electrode layer thickness is a second thickness h2 which is thinner than the first thickness h1. Of the plurality of resonators, the thickness of the electrode layer of the resonator that lies on the high-frequency side of the passband of the bandpass filter and has the closest anti-resonant frequency to the high-frequency end of the passband of the bandpass filter is the second thickness h2.

[0009] In a specific embodiment of the above-described aspect of the bandpass filter of the present invention, the thickness of the electrode layer of the resonator having an anti-resonant frequency that is on the high-frequency side of the passband of the bandpass filter and is the second closest anti-resonant frequency from the high-frequency end of the passband of the bandpass filter is the second thickness h2.

[0010] Thus, the pass characteristics of a resonator having the second closest anti-resonant frequency to the high-frequency end of the bandpass filter's passband have the second strongest influence on the attenuation band portion from the high-frequency end to the high-frequency side of the passband. Therefore, it is possible to efficiently suppress losses due to temperature changes and realize a bandpass filter with excellent power handling capabilities.

[0011] In a specific embodiment of the above-described aspect of the bandpass filter of the present invention, the thickness of the electrode layer of the resonator having the closest resonant frequency to the low-frequency end of the bandpass filter's passband, which is located on a lower frequency side than the passband of the bandpass filter, is the second thickness h2.

[0012] In this way, the frequency-temperature characteristics can be improved by thinning the electrode layer of the resonator that lies on the lower frequency side of the bandpass filter's passband and has the closest resonant frequency to the low-frequency end of the bandpass filter's passband.

[0013] In a specific embodiment of the above-described aspect of the bandpass filter of the present invention, the thickness of the electrode layer of the resonator having a resonant frequency that is lower in frequency than the passband of the bandpass filter and is the second closest to the low-frequency end of the passband of the bandpass filter is the second thickness h2.

[0014] In a specific embodiment of the above-described aspect, the bandpass filter of the present invention, when the wavelength defined by the electrode finger pitch of the IDT electrode is λ, the first thickness of the electrode layer of the resonator normalized by the wavelength λ is h1, and the second thickness of the electrode layer of the resonator is h2, is expressed by the following equations 1 and 2. 0.09≦h1 / λ≦0.10 …Equation 1 0.050≦h2 / λ≦0.075 …Equation 2 It satisfies the following conditions.

[0015] In a specific embodiment of the above-described aspect, the bandpass filter of the present invention is configured such that at least one of the plurality of resonators, in which the thickness of the electrode layer is less than the thickness h1 (thickness h2), is divided into a plurality of resonators having the same electrode layer thickness and connected in series to form a divided resonator.

[0016] Thus, while resonators with thin electrode layers generally have lower power handling capabilities than those with thicker electrode layers, by using a split resonator, the frequency-temperature characteristics can be improved by using a thin electrode layer, while simultaneously enhancing power handling capabilities.

[0017] In a specific embodiment of the above-described aspect, the bandpass filter of the present invention is a ladder-type filter with at least three stages.

[0018] The bandpass filter of the present invention, in a specific embodiment of the above-described aspect, is: A multimode elastic wave filter, The system comprises a ladder-type filter connected in series with the multimode elastic wave filter, The ladder-type filter comprises a series resonator and a parallel resonator. It is a DMS plus ladder type filter.

[0019] As a specific aspect of the above aspect, the band - pass filter of the present invention is such that the series resonator having the electrode layer with a thickness h2 thinner than the thickness h1 is a resonator that is not provided in the first and final stages of the series resonator.

[0020] One aspect of the multiplexer of the present invention includes the above - mentioned band - pass filter.

Effect of the Invention

[0021] According to the band - pass filter of the present invention, it includes a resonator in which the thickness of the electrode layer of the resonator is the first thickness h1 normalized by the wavelength λ, and a resonator in which the thickness of the electrode layer of the resonator is the second thickness h2 thinner than the first thickness h1. Since only the electrode layers of some resonators are made thinner than the normalized thickness h1, the loss can be suppressed only in some resonators, and the increase in the size of the entire band - pass filter can be suppressed. Furthermore, the resonator with the thin second thickness h2 contributes most to the formation of the portion up to the attenuation band on the high - frequency side of the pass - characteristic of the band - pass filter compared to other resonators. When the temperature characteristic is improved, the effect of suppressing the loss of the band - pass filter is the highest. It is a resonator having the closest anti - resonance frequency from the high - frequency end of the pass - band of the band - pass filter. Thus, since the electrode layers of some resonators with a particularly high loss - suppression effect are thinned to improve the frequency - temperature characteristic, it is possible to particularly efficiently suppress the loss due to temperature rise and realize a band - pass filter with excellent power - resistance.

Brief Description of the Drawings

[0022] [Figure 1] It is a circuit configuration diagram of a transmission filter as a band - pass filter according to the first embodiment of the present invention. [Figure 2] It is a cross - sectional view showing a cross - section of a resonator constituting the band - pass filter according to the first embodiment of the present invention. [Figure 3]This is a plan view of the resonator constituting the bandpass filter of the first embodiment of the present invention. [Figure 4] This is an enlarged cross-sectional view showing an enlarged cross-section of the electrode layer of the resonator constituting the bandpass filter of the first embodiment of the present invention. [Figure 5] Figure 2 is a graph showing the TCF as it changes with the thickness h / λ of the electrode layer of the resonator. [Figure 6] Figure 1 shows a graph illustrating the attenuation with respect to frequency, representing the pass characteristics of the transmitting filter and each resonator as a bandpass filter. [Figure 7] This is the circuit diagram of the transmitting filter in Example 6. [Figure 8] This is a circuit diagram of a duplexer including a transmit filter according to the first embodiment. [Figure 9] This is a circuit diagram of a duplexer including a receiving filter 40 according to the third embodiment. [Figure 10] This is a circuit diagram showing the duplexer of the fourth embodiment. [Figure 11] Figure 10 shows the receiving filter 60 as a DMS plus ladder type filter, the multimode elastic wave filter DMS, and a graph illustrating the pass characteristics of each resonator. [Figure 12] This is a circuit diagram of the transmit / receive filter (TRx filter) 400 of the fifth embodiment. [Figure 13] This is a cross-sectional view showing a cross-section of the resonator according to the sixth embodiment. [Figure 14] Figure 13 is a graph showing the TCF (Trend Correction Frequency) as the thickness h / λ of the electrode layer of the resonator changes. [Figure 15] This is a cross-sectional view showing a cross-section of the resonator according to the seventh embodiment. [Figure 16] Figure 15 is a graph showing the TCF as it changes with the thickness h / λ of the electrode layer of the resonator. [Figure 17] This is an enlarged cross-sectional view showing an enlarged view of the electrode layer in the eighth embodiment. [Modes for carrying out the invention]

[0023] <About the drawings> In the embodiments described below, the drawings are schematic and may differ from reality in terms of the relationship between thickness and planar dimensions, the ratio of the thickness of each layer, etc. Furthermore, there may be differences in the relationships and ratios of dimensions between the drawings themselves.

[0024] <Regarding the first embodiment> Figure 1 is a circuit diagram of a bandpass filter transmit filter 10, which is a first embodiment of the present invention. As shown in Figure 1, the transmit filter 10 as a bandpass filter is a ladder type filter and includes series resonators S1, S2, S3, S4, and S5 connected in series on the path from the transmit port Tx to the antenna port Ant, and parallel resonators P1, P2, P3, and P4 between the nodes connecting the series resonators S1, S2, S3, S4, and S5 and the ground. A node is a connection point between elements.

[0025] The first stage series resonator is S1, and the final stage series resonator is S5.

[0026] The series resonator S2 includes a divided resonator S21 and a divided resonator S22. The series resonator S3 includes divided resonators S31 and S32.

[0027] Figure 2 is a cross-sectional view showing a cross-section of a resonator constituting a bandpass filter according to the first embodiment of the present invention. More specifically, the basic structure of the series resonators S1 to S5 and the parallel resonators P1 to P4 described above is shown in the cross-sectional view as resonator 1. This resonator 1 comprises a piezoelectric layer 2 and an electrode layer 5 provided on the piezoelectric layer 2.

[0028] The piezoelectric layer 2 is, for example, made of 42° rotated Y-cut X-propagating lithium tantalate (LiTaO3), but is not limited to this, and other materials such as lithium niobate (LiNbO3) can also be used. The thickness of the piezoelectric layer 2 is, for example, 200 [μm].

[0029] Figure 3 is a plan view of a resonator constituting a bandpass filter according to the first embodiment of the present invention. In plan view, the resonator 1 comprises an IDT (interdigital transducer) electrode 6 and a reflector 8. The IDT electrode 6 comprises a plurality of electrode fingers 7. The IDT electrode 6 and the reflector 8 are formed by patterning an electrode layer 5.

[0030] Figure 4 is an enlarged cross-sectional view showing a magnified cross-section of the electrode layer of the resonator. This electrode layer 5 consists of a first metal layer 51 and a second metal layer 52. The first metal layer is, for example, an alloy of aluminum and copper. The second metal layer is, for example, titanium. This second metal layer 52, made of titanium, is provided as an adhesive layer to strengthen the bond between the piezoelectric layer 2 and the first metal layer 51, and the thickness of the second metal layer 52 is, for example, 15 nm.

[0031] The combined thickness of the first metal layer 51 and the second metal layer 52 is the thickness h of the electrode layer 5. In this embodiment, the electrode layer 5 thickness h is broadly classified into two types: a thickness h1 defined by the wavelength λ for each resonator, and a thickness h2 set to be thinner than that of h1.

[0032] When the thickness of the electrode layer of the first resonator, normalized by wavelength λ, is h1, and the thickness of the electrode layer of the second resonator is h2, the following equations 1 and 2 are satisfied. 0.09≦h1 / λ≦0.10 …Equation 1 0.050≦h2 / λ≦0.075 …Equation 2

[0033] Figure 6 is a graph showing the attenuation with respect to frequency as the pass characteristics (filter characteristics) of the transmit filter 10 as a bandpass filter shown in Figure 1 and each resonator. As shown in this graph, the passband of the transmit filter 10 is formed by the pass characteristics of each resonator. In Figure 6, at frequencies higher than the passband, the frequencies of the downward peaks in the pass characteristics of the series resonators S1 to S5 are the anti-resonant frequencies. At frequencies lower than the passband, the frequencies of the downward peaks in the pass characteristics of the parallel resonators S1 to S4 are the resonant frequencies.

[0034] <Example 1>

[0035] [Table 1]

[0036] Table 1 shows the wavelength λ defined by the pitch of each resonator, the thickness h of the electrode layer 5 defined by λ, h / λ[%], anti-resonant frequency, resonant frequency, and TCF (Temperature Coefficient of Frequency) of the transmitting filter 10 of Example 1 in the first embodiment shown in Figure 1.

[0037] In Table 1, a resonator where the thickness h of the metal layer 5 satisfies Equation 2 (0.050 ≤ thickness h2 / λ ≤ 0.075) is called the second resonator. The second resonator with a metal layer 5 thickness h2 (130 [nm]) is the divided resonator S21 and S22, which are obtained by dividing the series resonator S2. The divided resonators S21 and S22 have a TCF of -46.6, which is an improvement over the other resonators S1, etc. Resonators other than the first resonator are called the first resonator, where the thickness h of the metal layer 5 satisfies Equation 1 (0.09 ≤ thickness h1 / λ ≤ 0.10) is h1. In the first resonator, the TCF is close to each other, ranging from -51.2 to -53.1. The first resonators, where the electrode layer 5 has a thickness h1 (185 nm), are the series resonators S1, S31, S32, S4, S5 and the parallel resonators P1 to P5. The thickness h1 of the electrode layer 5 is determined by the wavelength λ. The wavelength λ is determined by the electrode finger pitch of the IDT electrode in each resonator. In the second resonator, the thickness h2 of the metal layer 5 satisfying equation 2 is thinner than the thickness h1 of the metal layer 5 satisfying equation 1 in the first resonator.

[0038] Note that resonators not labeled as split resonators in Table 1 are not split resonators. Also, the passband of the transmit filter 10 in Examples 1 to 6 is 1850 [MHz] to 1915 [MHz].

[0039] In the resonator shown in Figure 2, simulations confirm that reducing the thickness h of the electrode layer 5 to h2 improves the TCF. Figure 5 is a graph showing the TCF as a function of the change in electrode layer thickness h / λ for a resonator in which the electrode layer 5 is formed on the piezoelectric layer 2 as shown in Figure 2.

[0040] The simulation conditions are as follows:

[0041] Piezoelectric substrate: 42° rotation Y-cut X-propagation lithium tantalate Piezoelectric substrate thickness: 200 [μm] (100λ) Wavelength λ: 2[μm] Duty: 50%

[0042] As shown in Figure 5, for example, if the thickness h / λ is reduced from 0.10 (10%) to 0.065 (6.5%), the absolute value of the TCF can be reduced by M1 in Figure 5. This difference in improved value, M1, is 8 ppm / deg.C. In other words, it can be seen that reducing the thickness h of the electrode layer 5 from 0.1λ to 0.065λ improves the TCF.

[0043] Figure 6 shows a graph illustrating the attenuation of the transmit filter 10 and each resonator with respect to frequency. This explains that by improving the TCF of only the series resonator S2, it is possible to improve the power handling capacity of the transmit filter 10 as a bandpass filter while simultaneously suppressing the need to increase the size of the transmit filter 10. In this transmit filter 10 as a bandpass filter, the series resonator S2 contributes most to the attenuation portion F1 from the high-frequency end of the passband to the high-frequency side. The next (second) contributor to portion F1 is the series resonator S3. In other words, the shoulder-shaped portion in the upper right of the passband characteristic is most greatly contributed to by the series resonator S2. "High-frequency end of the passband" refers to the highest frequency side of the passband shown in Figure 6.

[0044] Since the TCF of these series resonators S2 to S5 is negative, if the temperature of each resonator rises due to the operation of filter 10, etc., it will shift in the direction of arrow T, that is, towards the lower frequency side.

[0045] This shift in the low-frequency side of section F1 means that the high-frequency end of the passband shifts to the low-frequency side, blocking signals that were originally allowed to pass through.

[0046] Blocking a signal that should be allowed to pass through results in a loss and generates heat in the resonator. If the amount of heat generated is too large, the resonator will overheat, reducing its power handling capacity. For this reason, the absolute value of the TCF (Tuning Cross Frequency) must be small.

[0047] To reduce the absolute value of TCF, one can consider thinning the electrode layer 5, for example, by reducing its thickness h to 0.65λ, as shown in Figure 5 above. However, while thinning the electrode layer 5 improves TCF, it also reduces the capacitance per unit area in a plan view of the resonator. Consequently, if the electrode layer 5 of all resonators in the transmitting filter 10 is thinned, it becomes necessary to increase the capacitance to return the resonator to its original capacitance, requiring an increase in the area of ​​the electrode layer 5 or the electrodes in a plan view. Therefore, the area of ​​the resonator in a plan view becomes larger. This leads to the problem that increasing the area of ​​all resonators in a plan view of the bandpass filter results in a significantly larger overall bandpass filter.

[0048] Therefore, in this embodiment, the TCF is improved by making the electrode layer 5 of only the series resonator S2 (divided resonators S21, S22), which contributes most to the formation of the attenuation band portion F1 from the high-frequency end of the passband to the high-frequency side, a thin thickness h2, while the thickness of the other resonators is kept at h1 rather than being as thin as h2. This makes it possible to efficiently suppress the movement of portion F1 when the temperature rises. Regarding the problem of increasing the size of the filter, only the area of ​​the series resonator S2 increases, while the area of ​​the other resonators does not increase, so the size increase can be suppressed. In this way, it is possible to achieve both improved power handling capacity of the transmitting filter 10 and suppression of the size increase of the bandpass filter.

[0049] Thus, in Example 1, by improving the TCF by reducing the thickness of the electrode layer 5 of the series resonator S2 to h2, it is possible to improve the power handling capacity of the transmitting filter 10 as a bandpass filter while simultaneously suppressing the need to increase the size of the transmitting filter 10.

[0050] Furthermore, by dividing the series resonator S2 into two series-connected divided resonators S21 and S22, the power handling capacity is improved. This suppresses the decrease in power handling capacity of the series resonator S2 caused by reducing the thickness of the electrode layer 5 to h2 only in the series resonator S2.

[0051] <Example 2>

[0052] [Table 2]

[0053] Table 2 shows the wavelength λ defined by the pitch of each resonator, the thickness h of the electrode layer 5 defined by λ, h / λ[%], anti-resonant frequency, resonant frequency, and TCF (frequency-temperature characteristic) of the transmitting filter 10 of Example 2 in the first embodiment shown in Figure 1.

[0054] In Table 2, a resonator where the thickness h of the metal layer 5 satisfies Equation 2 (0.050 ≤ thickness h2 / λ ≤ 0.075) is called a second resonator. The second resonator with a metal layer 5 of thickness h2 is the series resonator S2. The series resonator S2 has a TCF of -46.6, which is an improvement over the other resonators S1, etc. Resonators other than the first resonator have a metal layer 5 of thickness h1 that satisfies Equation 1 (0.09 ≤ thickness h1 / λ ≤ 0.10). The first resonators with a metal layer 5 of thickness h1 have TCFs that are close to each other, ranging from -51.2 to -53.1. The first resonators with an electrode layer 5 of thickness h1 are the series resonators S1, S3 to S5 and the parallel resonators P1 to P5. The thickness h1 is defined by the wavelength λ. The wavelength λ is determined by the electrode finger pitch of the IDT electrodes in each resonator. The thickness h2 of the metal layer 5 that satisfies Equation 2 is thinner than the thickness h1 of the metal layer 5 that satisfies Equation 1.

[0055] As shown in this Example 2, the present invention can also be applied to examples in which a divided resonator is not used in the series resonator.

[0056] <Example 3>

[0057] [Table 3]

[0058] Table 3 shows the wavelength λ defined by the pitch of each resonator, the thickness h of the electrode layer 5 defined by λ, h / λ[%], anti-resonant frequency, resonant frequency, and TCF (frequency-temperature characteristic) of the transmitting filter 10 of Example 3 in the first embodiment shown in Figure 1.

[0059] In this third embodiment, the thickness of the electrode layer 5 of the divided resonators S21 and S22, which correspond to the series resonator S2, and the parallel resonator P2 was set to a thickness h2, which is thinner than h1. The thickness of the electrode layer 5 of the other resonators is h1. Equations 1 and 2, which satisfy thicknesses h1 and h2, are the same as in the first embodiment.

[0060] The parallel resonator P2 has a resonant frequency that is even lower than the passband of the transmitting filter 10, and is closest to the low-frequency end of the bandpass filter's passband. For this reason, the parallel resonator P2 contributes most to the formation of the attenuation band portion F2 from the low-frequency end of the passband to the lower-frequency side.

[0061] By reducing the thickness h of the electrode layer 5 of the parallel resonator P2 to a thin thickness h2, the TCF is improved, effectively suppressing the movement of the low-frequency portion F2 of the passband when the temperature rises. Furthermore, because the electrode layer 5 is thinned to h2 only for some of the resonators, it is possible to suppress the increase in size of the transmitting filter 10. In other words, it is possible to achieve both improved power handling capacity and suppression of size increase for the transmitting filter 10.

[0062] Furthermore, similar to Example 1, by reducing the thickness h of the electrode layer 5 of the divided resonators S21 and S22 to a thin thickness h2, the TCF of the divided resonators S21 and S22 is improved, and the movement of the high-frequency portion F1 during temperature rise can be efficiently suppressed. This improves the power withstand capability of the transmitting filter 10. <Example 4>

[0063] [Table 4]

[0064] Table 4 shows the wavelength λ defined by the pitch of each resonator, the thickness h of the electrode layer 5 defined by λ, h / λ[%], anti-resonant frequency, resonant frequency, and TCF (frequency-temperature characteristic) of the transmitting filter 10 of Example 4 in the first embodiment shown in Figure 1.

[0065] In this embodiment 4, in addition to the divided resonators S21 and S22 obtained by dividing the series resonator S2 having the anti-resonant frequency closest to the high-frequency end of the passband, the thickness of the electrode layer 5 of the divided resonators S31 and S32 obtained by dividing the series resonator S3 having the second closest anti-resonant frequency to the high-frequency end of the passband was reduced to h2. The thickness of the electrode layer 5 of the other resonators is h1. Equations 1 and 2 satisfied by thicknesses h1 and h2 are the same as in embodiment 1.

[0066] This improves the TCF by reducing the thickness of the electrode layer 5 to h2 only for the series resonator S2 (divided resonators S21, S22) and the series resonator S3 (divided resonators S31, S32), thereby further improving the power handling capacity of the transmitting filter 10 as a bandpass filter compared to Example 1. In addition, by reducing the thickness of the electrode layer 5 for some resonators to h2 while keeping the thickness of the electrode layer 5 for other resonators at h1, it is possible to suppress the increase in size of the transmitting filter 10.

[0067] It is preferable to place series resonators with an electrode layer thickness h2 that is thinner than thickness h1 in stages other than the first and last stages.

[0068] Thinning the electrode layer reduces power handling capacity. However, the first-stage series resonator S1 consumes a large amount of power and requires high power handling capacity, so it is undesirable to make the electrode layer of the first-stage series resonator S1 thin to h2. Thinning the thickness of the final-stage series resonator S5 to h2 necessitates new impedance matching, which increases the effort required for redesign. If the electrode layers of the segmented resonators S21, S22, S31, S32 and the series resonator S4 are made thin to h2, these problems do not occur, thus suppressing the decrease in reliability due to reduced power handling capacity and the effort required for redesign.

[0069] <Example 5>

[0070] [Table 5]

[0071] Table 5 shows the wavelength λ defined by the pitch of each resonator, the thickness h of the electrode layer 5 defined by λ, h / λ[%], anti-resonant frequency, resonant frequency, and TCF (frequency-temperature characteristic) of the transmitting filter 10 of Example 5 in the first embodiment shown in Figure 1.

[0072] In this embodiment 5, in addition to setting the thickness of the electrode layer 5 of the series resonator S2 (divided resonators S21, S22), the series resonator S3 (divided resonators S31, S32), and the parallel resonator P2 to h2 as in embodiment 4, the electrode layer 5 of the parallel resonator P3, which has the second closest resonant frequency to the low-frequency end of the passband, was made even thinner by setting the thickness to h2.

[0073] Therefore, similar to Example 4, by reducing the thickness of the electrode layer 5 of the series resonator S2 (divided resonators S21, S22) and the series resonator S3 (divided resonators S31, S32) to h2, and improving the TCF of these resonators, it is possible to further improve the power withstand capability of the transmitting filter 10 as a bandpass filter.

[0074] Furthermore, in addition to the parallel resonator P2, which had an electrode layer thickness of h2 in Example 4, the electrode layer thickness of the parallel resonator P3 was further reduced to h2 in this embodiment. As a result, the TCF of the parallel resonator P3 is improved, and the movement of the low-frequency portion F2 of the passband when the temperature rises is suppressed more effectively than in Example 4. Moreover, because only some of the resonators have an electrode layer thickness of h2, it is possible to suppress the increase in size of the transmitting filter 10.

[0075] <Example 6> Figure 7 is a circuit diagram of the transmitting filter 10B in Example 6.

[0076] [Table 6]

[0077] Table 6 shows the wavelength λ defined by the pitch of each resonator, the thickness h of the electrode layer 5 defined by λ, h / λ[%], anti-resonant frequency, resonant frequency, and TCF (frequency-temperature characteristic) of the transmitting filter 10B in Example 6.

[0078] In this embodiment 6, the series resonator S2 was divided into three parts to form divided resonators S21, S22, and S23 connected in series.

[0079] Therefore, by dividing the series resonator S2 into series-connected segmented resonators S21, S22, and S23, the power handling capacity is improved. This suppresses the decrease in power handling capacity of the series resonator S2 caused by reducing the thickness of the electrode layer 5 to h2 only in the series resonator S2. Thus, it is possible to achieve both a thin electrode layer for the resonator and improved power handling capacity.

[0080] <Second Embodiment> Figure 8 is a circuit diagram of a duplexer 100 as a multiplexer including a transmit filter 10 according to the first embodiment of the present invention. As shown in Figure 8, this duplexer 100 comprises a transmit filter 10 as a bandpass filter and a receive filter 20. Components having the same role and name as in the first embodiment are given the same reference numerals and their descriptions are omitted.

[0081] In this way, a duplexer 100 equipped with the transmit filter 10 as a bandpass filter of the present invention can be configured. The transmit filter 10 can be adapted to the embodiments described above in Examples 1 to 6. <Third Embodiment>

[0082] Figure 9 is a circuit diagram of a duplexer including a receiving filter 40 according to a third embodiment of the present invention. This duplexer 200 is composed of a transmitting filter 30 and a receiving filter 40.

[0083] Both the transmit filter 30 and the receive filter 40 are ladder-type filters.

[0084] In the receiving filter 40, similar to the above examples 1 to 6, the electrode layer 5 of some of the resonators may be made thin h2. That is, in the passband characteristics, the electrode layer 5 of only the series resonator S7 (divided resonators S71, S72) that contributes most to the formation of the attenuation band portion from the high-frequency end of the passband to the high-frequency side, or the series resonator S8 (S81, S82) that contributes second most, may be configured with a thin thickness h2. Here, the passband characteristics are omitted from the illustration, assuming that the sign of the series resonator S2 in Figure 6 corresponds to the series resonator S7 of the receiving filter 40, and the series resonator S3 in Figure 6 corresponds to S8. Furthermore, the electrode layer 5 of only the parallel resonator P6 (corresponding to the parallel resonator P2 in Figure 6) that contributes most to the formation of the attenuation band portion from the low-frequency end of the passband to the low-frequency side, or the parallel resonator P7 (corresponding to the parallel resonator P3 in Figure 6) that contributes second most, may be configured with a thin thickness h2.

[0085] <Fourth Embodiment> Figure 10 is a circuit diagram showing a duplexer as a multiplexer according to a fourth embodiment of the present invention. This duplexer 300 includes a transmit filter 50 and a receive filter 60.

[0086] The transmit filter 50 is a ladder-type filter.

[0087] The receiving filter 60 is a DMS-plus ladder filter, which consists of a multimode elastic wave filter (DMS) and a ladder filter (L) connected in series.

[0088] The ladder filter L is composed of series resonators Sr1 and Sr2 and parallel resonators Pr1 and Pr2.

[0089] In the receiving filter 60 as a DMS plus ladder type filter, the present invention may be applied in the same manner as in the above embodiments 1 to 6, by setting the thickness of the electrode layer 5 to a thin h2 for at least the series resonator Sr1 and, in addition to the series resonator Sr1, either one or both of the parallel resonators Pr1 and Pr2.

[0090] Figure 11 is a graph showing the receiving filter 60 as a DMS plus ladder type filter in Figure 10, the multimode elastic wave filter DMS, and the pass characteristics of each resonator.

[0091] The series resonator Sr1 is the closest resonator with an anti-resonant frequency to the high-frequency end of the passband of this filter. Therefore, the series resonator Sr1 contributes most to the formation of the partial F1A from the high-frequency end of the passband to the attenuation region. Since it is located on the high-frequency side of the passband of the bandpass filter, the thickness of the electrode layer 5 of the series resonator Sr1 is made thinner than the original thickness h1, h2, to improve the TCF. By improving the TCF of the series resonator Sr1, it is possible to suppress the movement of the partial F1A to the low-frequency side (arrow T2 in Figure 11) even if the temperature of the series resonator Sr1 rises. In addition, since the thickness of the electrode layer 5 is reduced for only some of the resonators, it is possible to suppress the increase in the size of the filter. Details of the thicknesses h1 and h2 are the same as in Table 1 of Example 1, so they are omitted here.

[0092] The resonator with the second closest anti-resonant frequency from the high-frequency end of the filter's passband is the series resonator Sr2, and therefore contributes second most to the formation of partial F1A. For this reason, the thickness of the electrode layer 5 of the series resonator Sr2 is set to h2, which is thinner than the original thickness h1. By setting the thickness of the electrode layer 5 of the series resonator Sr2 to h2 in this way, the TCF can be improved. Details of the thickness are the same as in Table 1 and are therefore omitted. In this embodiment, the thickness of the electrode layer 5 of the series resonator Sr2 is set to the thin h2, but the thickness of the electrode layer 5 of the series resonator Sr2 may also be set to h1.

[0093] The parallel resonator Pr1 is located on the low-frequency side of the filter's passband and has the closest resonant frequency to the low-frequency end of the passband. Therefore, the parallel resonator Pr1 contributes most to the formation of the partial F2A from the low-frequency end of the passband to the attenuation region.

[0094] In this embodiment, the TCF of the parallel resonator Pr1 is improved by setting the thickness of the electrode layer 5 of the parallel resonator Pr1 to h2, which is thinner than the original thickness h1.

[0095] By improving the TCF of the parallel resonator Pr1, it is possible to suppress the shift of partial F2A to the low-frequency side (arrow T2 in Figure 11) even when the temperature of the parallel resonator Pr1 rises. In addition, since the thickness of the electrode layer 5 is reduced only in some of the resonators, it is possible to suppress the increase in the size of the filter.

[0096] <Fifth Embodiment> Figure 12 is a circuit diagram of a transmit / receive filter (TRx filter) 400 according to the fifth embodiment of the present invention. This transmit / receive filter 400 is a ladder-type filter, in which series resonators S1, S2, S3, and S4 are connected in series between the transmit / receive port TRx and the antenna port Ant, and parallel resonators P1, P2, P3, and P4 are connected in parallel between these series resonators and ground.

[0097] The parallel resonator P1 is connected to the node between the transmit / receive port TRx and the series resonator S1.

[0098] The series resonator S2 is divided into two resonators S21 and S22, which are connected in series. The series resonator S3 is divided into two resonators S31 and S32, which are connected in series.

[0099] The transmit / receive filter 400 is a filter that switches between transmitting as a transmit filter and receiving as a receive filter.

[0100] The present invention can also be applied to such a transmit / receive filter 400 to construct a bandpass filter in which the electrode layer h2 of a series resonator having the closest anti-resonant frequency from the high-frequency end of the filter's passband, or a series resonator having the second closest anti-resonant frequency in addition to the series resonator having the closest anti-resonant frequency from the high-frequency end of the filter's passband, is made thin. By improving the TCF of the series resonator, even if the temperature rises, the shift of the partial F1A from the filter's passband to the attenuation band to the lower frequency side is suppressed, preventing heat generation due to loss and improving power withstand capability. Furthermore, since the thickness of the electrode layer 5 is reduced only for some of the resonators, the size of the filter can be suppressed.

[0101] The details of these electrode layers 5 are the same as in Examples 1 to 6, so we will omit their explanation.

[0102] <Sixth Embodiment> Figure 13 is a cross-sectional view showing a cross-section of a resonator according to the sixth embodiment. As shown in Figure 13, the resonator 1A may have a support substrate 3 below the piezoelectric layer 2.

[0103] The support substrate 3 may be made of a spinel substrate, for example, but may also be made of other materials such as a sapphire substrate, silicon substrate, quartz substrate, crystal substrate, alumina substrate, or silicon carbide substrate.

[0104] The thickness of the support substrate 3 is, for example, 200 [μm].

[0105] In this embodiment, simulations confirm that reducing the thickness h of the electrode layer 5 to h2 improves the TCF. Figure 14 is a graph showing the TCF as a function of the change in the thickness h / λ of the electrode layer 5 of the resonator 1A equipped with the support substrate 3, piezoelectric layer 2, and electrode layer 5 shown in Figure 13.

[0106] The simulation conditions are as follows:

[0107] Piezoelectric substrate: 42° rotation Y-cut X-propagation lithium tantalate Piezoelectric substrate thickness: 1.0 [μm] (0.5λ) Support substrate: Spinel Support substrate thickness: 200 [μm] Wavelength λ: 2[μm] Duty: 50%

[0108] As shown in Figure 14, for example, if the thickness h / λ is reduced from 0.10 (10%) to 0.065 (6.5%), the TCF can be improved by reducing its absolute value by M2 as shown in Figure 14. This difference in improved value, M2, is 9 [ppm / deg.C]. In other words, it can be seen that the TCF is improved by reducing the thickness h of the electrode layer 5 from 0.1λ to 0.065λ.

[0109] As shown in the graph in Figure 14, the TCF can be improved by reducing the thickness h, so the present invention can be applied to resonators in which a support substrate 3 is provided below the piezoelectric layer 2.

[0110] <Seventh Embodiment> Figure 15 is a cross-sectional view showing a cross-section of the resonator according to the seventh embodiment. As shown in Figure 15, the resonator 1B may have an intermediate layer 4 between the piezoelectric layer 2 and the support substrate 3.

[0111] The intermediate layer 4 is, for example, silicon oxide (SiO2).

[0112] The thickness of the support substrate 3 is, for example, 200 [μm].

[0113] In this embodiment, simulations confirm that reducing the thickness h of the electrode layer 5 to h2 improves the TCF. Figure 16 is a graph showing the TCF as a function of the change in electrode layer thickness h / λ of the resonator 1B, which is equipped with a support substrate 3, an intermediate layer 4, a piezoelectric layer 2, and an electrode layer 5, as shown in Figure 15.

[0114] The simulation conditions are as follows:

[0115] Piezoelectric substrate: 42° rotation Y-cut X-propagation lithium tantalate Piezoelectric substrate thickness: 0.6 [μm] (0.3λ) Intermediate layer: Silicon oxide Interlayer thickness: 1.0 [μm] (0.5λ) Support substrate: Spinel Support substrate thickness: 200 [μm] Wavelength λ: 2[μm] Duty: 50%

[0116] As shown in Figure 16, for example, if the thickness h / λ is reduced from 0.10 (10%) to 0.065 (6.5%), the TCF can be improved by reducing its absolute value by M3 as shown in Figure 16. This difference in improved value, M3, is 11 ppm / deg.C. In other words, it can be seen that the TCF is improved by reducing the thickness h of the electrode layer 5 of resonator 1B from 0.1λ to 0.065.

[0117] As shown in the graph in Figure 16, the present invention can be applied to a resonator 1B in Figure 15, in which an intermediate layer 4 is provided between the piezoelectric layer 2 and the support substrate 3.

[0118] <Eighth Embodiment> Figure 17 is an enlarged cross-sectional view showing an expanded electrode layer in the eighth embodiment. This electrode layer 5B comprises a first metal layer 51, a second metal layer 52, and a third metal layer 53.

[0119] The first metal layer is, for example, an alloy of aluminum and copper. The second metal layer is, for example, titanium. This second metal layer 52 made of titanium is provided as an adhesive layer to strengthen the bond between the piezoelectric layer 2 and the first metal layer 51. The thickness of the third metal layer 53 is, for example, 15 nm. The third metal layer 53 is, for example, titanium. The thickness of the third metal layer is, for example, 15 nm.

[0120] In these embodiments, the pass characteristics of each resonator in the bandpass filter have been described, but the positions of the resonators with pass characteristics are not limited to these examples. For example, the pass characteristics of series resonator S2 and series resonator S3 may be swapped.

[0121] In these embodiments, the case where the bandpass filter of the present invention is a transmit filter has been described, but it may also be applied to a receive filter. Furthermore, the bandpass filter of the present invention may be applied to both the transmit filter and the receive filter of a duplexer.

[0122] While these embodiments have described how the bandpass filter of the present invention can be used in a duplexer, it is not limited to this and can be applied to other multiplexers such as triplexers or quadplexers. Furthermore, the bandpass filter of the present invention may be applied to some or all of the bandpass filters included in such a multiplexer.

[0123] The present invention has been described above, but in the specific implementation of the present invention as a bandpass filter and multiplexer, various modifications and additions are possible without departing from the spirit of the invention, and are not limited to the embodiments described above. [Explanation of Symbols]

[0124] 1,1A,1B resonator 2 Piezoelectric layer 3. Support substrate 4. Middle Class 5 Electrode layer 6 IDT electrode 7 electrode fingers 8 reflector 10,30,50 Sending Filter 20,40,60 Receiver Filter 100, 200, 300 Duplexa 400 transmit / receive filters Thickness of the electrode layers h, h1, h2 S1,S2,S3,S4,S5 Series resonator P1,P2,P3,P4 parallel resonator

Claims

1. Piezoelectric substrate and Multiple resonators formed on the piezoelectric substrate, Equipped with, The plurality of resonators each have an IDT electrode consisting of an electrode layer provided on the piezoelectric substrate, The plurality of resonators include a resonator whose electrode layer thickness is a first thickness h1 normalized by the wavelength λ defined by the electrode finger pitch of the IDT electrode, and a resonator whose electrode layer thickness is a second thickness h2 which is thinner than the first thickness h1. Of the plurality of resonators, the thickness of the electrode layer of the resonator that lies on the high-frequency side of the passband of the bandpass filter and has the closest anti-resonant frequency to the high-frequency end of the passband of the bandpass filter is the second thickness h2. Bandpass filter.

2. Furthermore, the thickness of the electrode layer of the resonator that lies at a higher frequency than the passband of the bandpass filter and has the second closest anti-resonant frequency from the high-frequency end of the bandpass filter's passband is the second thickness h2. The bandpass filter according to claim 1.

3. Furthermore, the thickness of the electrode layer of the resonator that lies on the lower frequency side of the passband of the bandpass filter and has the closest resonant frequency to the low-frequency end of the passband of the bandpass filter is the second thickness h2. The bandpass filter according to claim 1.

4. Furthermore, the thickness of the electrode layer of the resonator that lies on the lower frequency side of the passband of the bandpass filter and has the second closest resonant frequency from the low-frequency end of the bandpass filter's passband is the second thickness h2. The bandpass filter according to claim 1.

5. When the wavelength defined by the electrode finger pitch of the IDT electrode is λ, and the first thickness of the electrode layer of the resonator normalized by the wavelength λ is h1, and the second thickness of the electrode layer of the resonator is h2, then the following equations 1 and 2 0.09≦h1 / λ≦0.10 …Formula 1 0.050≦h2 / λ≦0.075…Formula 2 satisfies A bandpass filter according to any one of claims 1 to 4.

6. Of the aforementioned plurality of resonators, at least one resonator in which the thickness of the electrode layer is a second thickness h2 that is thinner than the first thickness h1 is divided into a plurality of resonators having the same electrode layer thickness and configured as a divided resonator connected in series. A bandpass filter according to any one of claims 1 to 4.

7. The bandpass filter is a ladder filter with at least three stages. A bandpass filter according to any one of claims 1 to 4.

8. The aforementioned bandpass filter is A multimode elastic wave filter, A ladder-type filter connected in series with the multi-mode elastic wave filter, Equipped with, The ladder-type filter comprises a series resonator and a parallel resonator. This is a DMS plus ladder type filter. A bandpass filter according to any one of claims 1 to 4.

9. A series resonator in which the thickness of the electrode layer is less than the thickness h1 (thickness h2) is a resonator that is not one of the resonators provided in the first or final stage of the series resonator provided in the bandpass filter. A bandpass filter according to any one of claims 1 to 4.

10. The bandpass filter is provided as described in claim 1. Multiplexer.

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