SURFACE ACOUSTIC WAVE RESONATOR WITH ASYMMETRIC REFLECTORS

A multimode longitudinally coupled surface acoustic wave resonator is disclosed. The multimode longitudinally coupled surface acoustic wave resonator can include a first interdigital transducer electrode that is positioned over a piezoelectric layer. The first interdigital transducer electrode includes fingers having a first pitch. The multimode longitudinally coupled surface acoustic wave resonator can also include first and second sets of reflectors that are positioned over the piezoelectric layer. The first and second sets of reflectors include a first number of reflectors having a second pitch and a second number of reflectors having a third pitch, respectively. The first pitch is greater than the second pitch. The multimode longitudinally coupled surface acoustic wave resonator can further include a second interdigital transducer electrode that is positioned over the piezoelectric layer and between the first interdigital transducer electrode and the first set of reflectors. The second interdigital transducer electrode includes fingers having a fourth pitch.

BACKGROUND

Technical Field

Embodiments of this disclosure relate to surface acoustic wave devices with two or more resonant frequencies.

Description of Related Technology

An acoustic wave filter can include a plurality of resonators arranged to filter a radio frequency signal. Example acoustic wave filters include surface acoustic wave (SAW) filters and bulk acoustic wave (BAW) filters. A surface acoustic wave resonator can include an interdigital transductor electrode on a piezoelectric substrate. The surface acoustic wave resonator can generate a surface acoustic wave on a surface of the piezoelectric layer on which the interdigital transductor electrode is disposed. A multi-mode SAW filter, such as a double-mode SAW (DMS) filter, can include a plurality of longitudinally coupled interdigital transducer electrodes positioned between acoustic reflectors.

Acoustic wave filters can be implemented in radio frequency electronic systems. For instance, filters in a radio frequency front end of a mobile phone can include acoustic wave filters. An acoustic wave filter can be a band pass filter. A plurality of acoustic wave filters can be arranged as a multiplexer. For example, two acoustic wave filters can be arranged as a duplexer.

SUMMARY

In one aspect, a surface acoustic wave resonator that has at least a first resonant frequency and a second resonant frequency is disclosed. The surface acoustic wave resonator can include an interdigital transducer electrode over a piezoelectric layer. The interdigital transducer electrode includes fingers having a first pitch. The surface acoustic wave resonator can include a set of reflectors over the piezoelectric layer. The set of reflectors includes a number of reflectors having a second pitch. The first pitch is greater than the second pitch. The number of reflectors are configured to compensate for degradation of a quality factor of the surface acoustic wave resonator due to having the first pitch greater than the second pitch.

In one embodiment, the surface acoustic wave resonator further includes a second set of reflectors over the piezoelectric layer. The interdigital transducer electrode can be positioned between the set of reflectors and the second set of reflectors. The second set of reflectors can include a second number of reflectors having a third pitch. The first pitch of the interdigital transducer electrode can be greater than the third pitch. The second pitch and the third pitch can be the same. The second pitch and the third pitch can be different.

In one embodiment, the first pitch is 1% to 20% greater than the second pitch. The first pitch can be 10% to 20% greater than the second pitch.

In one embodiment, an acoustic wave filter that is configured to filter a radio frequency signal includes the surface acoustic wave resonator as a shunt acoustic wave resonator.

In one aspect, a surface acoustic wave resonator that has at least a first resonant frequency and a second resonant frequency is disclosed. The surface acoustic wave resonator can include an interdigital transducer electrode over a piezoelectric layer. The interdigital transducer electrode includes fingers having a first pitch. The surface acoustic wave resonator can include a set of reflectors over the piezoelectric layer. The set of reflectors includes a number of reflectors having a second pitch. The first pitch is greater than the second pitch. The number of reflectors are configured so as to compensate for reduction of a reflection of the surface acoustic wave resonator provided by the set of reflectors due to having the first pitch greater than the second pitch.

In one embodiment, the surface acoustic wave resonator further includes a second set of reflectors over the piezoelectric layer. The interdigital transducer electrode can be positioned between the set of reflectors and the second set of reflectors. The second set of reflectors can include a second number of reflectors having a third pitch. The first pitch of the interdigital transducer electrode can be greater than the third pitch. The second pitch and the third pitch can be the same. The second pitch and the third pitch can be different.

In one embodiment, the first pitch is 1% to 20% greater than the second pitch. The first pitch can be 10% to 20% greater than the second pitch.

In one embodiment, an acoustic wave filter that is configured to filter a radio frequency signal includes the surface acoustic wave resonator as a shunt acoustic wave resonator.

In one embodiment, a packaged module includes a substrate supporting at least one filter. The at least one filter can include one or more of the surface acoustic wave resonator. The packaged module can be a radio frequency front end module. The packaged module can be a diversity receive module. A wireless communication device can include an antenna, a transceiver, and one or more of the packaged modules.

In one aspect, an acoustic wave filter is disclosed. The acoustic wave filter can include shunt acoustic wave resonators that includes a first shunt acoustic wave resonator. The first shunt acoustic wave resonator includes an interdigital transducer electrode having fingers with a first pitch and a set of reflectors having a number of reflectors with a second pitch. The first pitch is greater than the second pitch. The number of reflectors are configured so as to compensate for degradation of a quality factor of the surface acoustic wave resonator due to having the first pitch greater than the second pitch. The first shunt acoustic resonator has at least a first resonant frequency and a second resonant frequency. The acoustic wave filter can include series acoustic wave resonators. The series acoustic wave resonators and the shunt acoustic wave resonators are together arranged to filter a radio frequency signal.

In one embodiment, the first pitch is 10% to 20% greater than the second pitch.

In one embodiment, the first shunt acoustic wave resonator further includes a second set of reflectors having a second number of reflectors with a third pitch. The interdigital transducer electrode can be positioned between the set of reflectors and the second set of reflectors. The first pitch of the interdigital transducer electrode can be greater than the third pitch.

In one aspect, a surface acoustic wave resonator that has at least a first resonant frequency and a second resonant frequency is disclosed. The surface acoustic wave resonator can include an interdigital transducer electrode over a piezoelectric layer. The interdigital transducer electrode includes fingers having a first pitch. The surface acoustic wave resonator can include a first set of reflectors over the piezoelectric layer. The first set of reflectors includes a first number of reflectors having a second pitch. The first pitch is greater than the second pitch. The surface acoustic wave resonator can include a second set of reflectors over the piezoelectric layer. The second set of reflectors includes a second number of reflectors having a third pitch. The second number of reflectors is different from the first number of reflectors. The second set of reflectors is positioned such that the interdigital transducer electrode is positioned between the first set of reflectors and the second set of reflectors.

In one embodiment, the second pitch and the third pitch are the same.

In one embodiment, the second pitch and the third pitch are different. The first pitch can be greater than the third pitch.

In one embodiment, the first pitch is 1% to 20% greater than the second pitch. The first pitch can be 10% to 20% greater than the second pitch.

In one embodiment, an acoustic wave filter that is configured to filter a radio frequency signal includes the surface acoustic wave resonator as a shunt acoustic wave resonator.

In one embodiment, the number of reflectors are configured so as to compensate for degradation of a quality factor of the SAW resonator due to having the first pitch greater than the second pitch.

In one embodiment, the surface acoustic wave resonator further includes a second interdigital transducer electrode over the piezoelectric layer and is positioned between the interdigital transducer electrode and the first set of reflectors. The surface acoustic wave resonator can further include a third interdigital transducer electrode over the piezoelectric layer and is positioned between the interdigital transducer electrode and the second set of reflectors.

In one aspect, an acoustic wave filter is disclosed. The acoustic wave filter can include shunt acoustic wave resonators that includes a first shunt acoustic wave resonator. The first shunt acoustic wave resonator includes an interdigital transducer electrode having fingers with a first pitch, a first set of reflectors having a first number of reflectors with a second pitch, and a second set of reflectors having a second number of reflectors with a third pitch. The first pitch is greater than the second pitch. The first number is different from the second number. The first shunt acoustic resonator has at least a first resonant frequency and a second resonant frequency. The acoustic wave filter can include series acoustic wave resonators. The series acoustic wave resonators and the shunt acoustic wave resonators are together arranged to filter a radio frequency signal.

In one embodiment, the second pitch and the third pitch are the same.

In one embodiment, the second pitch and the third pitch are different. The first pitch can be greater than the third pitch.

In one embodiment, the first pitch is 1% to 20% greater than the second pitch. The first pitch can be 10% to 20% greater than the second pitch.

In one embodiment, a packaged module that includes a substrate supporting at least one filter includes one or more of the surface acoustic wave resonator. The packaged module can be a radio frequency front end module. The packaged module can be a diversity receive module. A wireless communication device includes an antenna, a transceiver, and one or more of the packaged modules of any of the preceding claims.

In one aspect, a multimode longitudinally coupled surface acoustic wave resonator is disclosed. The multimode longitudinally coupled surface acoustic wave resonator can include a first interdigital transducer electrode over a piezoelectric layer. The first interdigital transducer electrode includes fingers having a first pitch. The multimode longitudinally coupled surface acoustic wave resonator can include a first set of reflectors over the piezoelectric layer. The first set of reflectors includes a first number of reflectors having a second pitch. The first pitch is greater than the second pitch. The multimode longitudinally coupled surface acoustic wave resonator can include a second set of reflectors over the piezoelectric layer. The second set of reflectors includes a second number of reflectors having a third pitch. The first pitch is greater than the third pitch. The multimode longitudinally coupled surface acoustic wave resonator can include a second interdigital transducer electrode over the piezoelectric layer and positioned between the first interdigital transducer electrode and the first set of reflectors. The second interdigital transducer electrode includes fingers having a fourth pitch.

In one embodiment, the second pitch and the third pitch are the same.

In one embodiment, the second pitch and the third pitch are different.

In one embodiment, the first pitch is 1% to 20% greater than the second pitch. The first pitch can be 10% to 20% greater than the second pitch.

In one embodiment, an acoustic wave filter configured to filter a radio frequency signal includes the multimode longitudinally coupled surface acoustic wave resonator as a shunt acoustic wave resonator.

In one embodiment, the multimode longitudinally coupled surface acoustic wave resonator further includes a third interdigital transducer electrode over the piezoelectric layer and positioned between the first interdigital transducer electrode and the second set of reflectors. The third interdigital transducer electrode can include fingers having a fifth pitch. The fifth pitch of the third interdigital transducer electrode can be different from the first pitch of the first interdigital transducer electrode.

In one embodiment, the fourth pitch is greater than the second pitch.

In one embodiment, a packaged module including a substrate supporting at least one filter includes one or more surface acoustic wave resonators. The packaged module can be a radio frequency front end module. The packaged module can be a diversity receive module.

In one embodiment, a wireless communication device includes an antenna, a transceiver, and one or more of the packaged modules.

In one aspect, an acoustic wave filter is disclosed. The acoustic wave filter can include shunt acoustic wave resonators that includes a first shunt acoustic wave resonator. The first shunt acoustic wave resonator includes an interdigital transducer electrode having fingers with a first pitch, a first set of reflectors having a first number of reflectors with a second pitch, a second set of reflectors having a second number of reflectors with a third pitch, and a second interdigital transducer electrode having fingers with a fourth pitch. The first pitch is greater than the second pitch and the third pitch. The first shunt acoustic resonator has at least a first resonant frequency and a second resonant frequency. The acoustic wave filter can include series acoustic wave resonators. The series acoustic wave resonators and the shunt acoustic wave resonators are together arranged to filter a radio frequency signal.

In one embodiment, the second pitch and the third pitch are the same.

In one embodiment, the second pitch and the third pitch are different.

In one embodiment, the first pitch is 1% to 20% greater than the second pitch. The first pitch can be 10% to 20% greater than the second pitch.

In one embodiment, the first shunt acoustic wave resonator further includes a third interdigital transducer electrode that is positioned between the first interdigital transducer electrode and the second set of reflectors. The third interdigital transducer electrode can include fingers having a fifth pitch. The fifth pitch of the third interdigital transducer electrode can be different from the first pitch of the first interdigital transducer electrode.

For purposes of summarizing the disclosure, certain aspects, advantages and novel features of the innovations have been described herein. It is to be understood that not necessarily all such advantages may be achieved in accordance with any particular embodiment. Thus, the innovations may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.

The present disclosure relates to U.S. patent application Ser. No. ______ [Attorney Docket SKYWRKS.1156A1], titled “SURFACE ACOUSTIC WAVE RESONATOR WITH MODULATED PITCH,” filed on even date herewith, and U.S. patent application Ser. No. ______ [Attorney Docket SKYWRKS.1156A2], titled “MULTIMODE LONGITUDINALLY COUPLED SURFACE ACOUSTIC WAVE RESONATOR WITH MODULATED PITCH,” filed on even date herewith, the entire disclosure of which are hereby incorporated by reference herein.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

Acoustic wave filters can filter radio frequency (RF) signals in a variety of applications, such as in an RF front end of a mobile phone. An acoustic wave filter can be implemented with surface acoustic wave (SAW) devices. A SAW device can be, for example, a multimode longitudinally coupled SAW filter (e.g., a double mode SAW (DMS) filter) or a SAW resonator.

Filters with rejection over a relatively wide frequency range are desired for certain RF systems. Acoustic wave filters can include series acoustic wave resonators and shunt acoustic wave resonators. An anti-resonance frequency of a series acoustic wave resonator can be used for rejection in an acoustic wave filter. The anti-resonance frequency of the series acoustic wave resonator can create an open to thereby create a notch in a frequency response. A resonant frequency of a shunt acoustic wave resonator can be used for rejection in an acoustic wave filter. The resonant frequency of the shunt acoustic wave resonator can create a short to ground to thereby create a notch in a frequency response. The series acoustic wave resonator can have its highest conductance at the resonant frequency.

To achieve a relatively wide frequency range for rejection, an acoustic wave filter can include a plurality of shunt acoustic wave resonators each having a different resonant frequency. As an example, an acoustic wave filter can include 4 or 5 shunt acoustic wave resonators each having different respective resonant frequencies. With more shunt acoustic wave resonators having different resonant frequencies, the acoustic wave filter can achieve relatively higher rejection. At the same time, an acoustic wave filter with more acoustic wave resonators can consume additional area and/or cause an insertion loss degradation.

Aspects of this disclosure relate to an acoustic wave resonator having at least two resonant frequencies. The acoustic wave resonator can be arranged as a shunt resonator in an acoustic wave filter. Such a shunt resonator can achieve at least two notches and increase a frequency range for rejection of the acoustic wave filter. The acoustic wave filter can be a band pass filter with a pass band. For example, the acoustic wave resonator can have a second resonant frequency between a first resonant frequency and a lower edge of the pass band.

An acoustic wave device with at least two resonant frequencies can include an interdigital transducer (IDT) electrode with IDT fingers having a first pitch corresponding to a resonant frequency, and a pair of reflector structures that includes a first set of reflectors having a second pitch and a second set of reflectors having a third pitch. The acoustic wave device can be a surface acoustic wave (SAW) resonator. For example, the acoustic wave device can be a temperature compensated SAW resonator, a non-temperature compensated SAW resonator, or a multilayer piezoelectric substrate SAW resonator. In some embodiments, the first pitch can be greater than the second pitch and/or the third pitch. In some embodiments, a number of reflectors in the first set of reflectors and a number of reflectors in the second set of reflectors can be different. The number of reflectors in the first set of reflector and the second number of reflectors in the second set of reflectors can be determined based at least in part on a quality factor (Q) achieved by the acoustic wave device. In some embodiments, the first and second numbers can be selected such that the Q is greater than a certain value. For example the first and the second numbers can be selected so as to compensate for degradation of the Q due to having the first pitch greater than the second pitch. In some embodiments, the first and second numbers can be selected such that a reflection of the acoustic wave device is greater than a certain value for a frequency range from above a passband of a filter that includes the surface acoustic wave resonator. For example, the first and second numbers can be selected so as to compensate for degradation of the reflection of the acoustic wave device due to having the first pitch greater than the second pitch. In some embodiments, the acoustic wave device includes a multimode surface acoustic wave (MMS) resonator. The MMS resonator can include a second IDT electrode with IDT fingers having a fourth pitch and a third IDT electrode with IDT fingers having a fifth pitch. The first pitch, the fourth pitch, and the fifth pitch can be different, and be greater than the second pitch and/or the third pitch.

Though present disclosure may describe various features in connection with certain types of resonators, principles and advantages disclosed herein can be implemented in any suitable type of resonators, such as boundary wave resonators and/or Lamb wave resonators.

A shunt acoustic wave resonator with multiple resonant frequencies can improve out of band rejection for a filter without significantly degrading the filter response in a pass band. With a shunt acoustic wave resonator with multiple resonant frequencies, stringent rejection specifications can be met with fewer acoustic wave resonators than some previous solutions. Certain aspects of this disclosure can be particularly beneficial when a wider passband compared to the reflection band stopband width is desired, and/or a relatively low frequency resonance is desired to obtain a relatively wide rejection band.

FIG.1Aillustrates a top plan view of a surface acoustic wave (SAW) resonator1.FIG.1Billustrates a pitch profile of the SAW resonator1shown inFIG.1A.FIG.1Cis a graph that illustrates simulated results of the SAW resonator1ofFIG.1Awhen the SAW resonator1is used as a shunt resonator.

The SAW resonator1includes an IDT electrode10and a pair of reflector structures12,14. As shown inFIG.1B, the IDT electrode10and the pair of reflector structures12,14have the same pitches. Also, a number of reflectors in the pair of reflector structures are the same in the SAW resonator1.

The simulated results in the graph ofFIG.1Cincludes simulated admittance result of the SAW resonator1. A single resonance is observed from the graph. Therefore, the SAW resonator1is not suitable when at least two resonant frequencies are desired.

FIG.2Aillustrates a top plan view of a SAW resonator2according to an embodiment.FIG.2Billustrates a pitch profile of the SAW resonator1shown inFIG.2A.FIG.2Cillustrates a cross section of the SAW resonator2ofFIG.2A.FIG.2Dis a graph that illustrates simulated results of the SAW resonator2ofFIG.2Awhen the SAW resonator3is used as a shunt resonator.

The SAW resonator2can include an interdigital transducer (IDT) electrode20with IDT fingers22having a first pitch (λ0) corresponding to a resonant frequency, and a pair of reflector structures that includes a first set of reflectors24having a second pitch (λ1) and a second set of reflectors26having a third pitch (λ2). The IDT electrode20, the first set of reflectors24, and the second set of reflectors26can be positioned over a piezoelectric layer28. In the illustrated embodiment, the first pitch (λ0) is greater than the second pitch (λ1) and the third pitch (λ2). A number of reflectors in the first set of reflectors24and a number of reflectors in the second set of reflectors26can be greater than a number of reflectors in the SAW resonator1shown inFIG.1A.

The IDT electrode20can include any suitable material. For example, the IDT electrode20can include tungsten (W), aluminum (Al), copper (Cu), magnesium (Mg), titanium (Ti), molybdenum (Mo), the like, or any suitable combination thereof. The IDT electrode20may include alloys, such as AlMgCu, AlCu, etc. The first set of reflectors24and the second set of reflectors26can include any suitable material. For example, the first set of reflectors24and the second set of reflectors26can include tungsten (W), aluminum (Al), copper (Cu), magnesium (Mg), titanium (Ti), molybdenum (Mo), the like, or any suitable combination thereof. The first set of reflectors24and the second set of reflectors26may include alloys, such as AlMgCu, AlCu, etc. In some embodiments, one or more of the first IDT electrode20, the first set of reflectors24, and/or the second set of reflectors26can have a multi-layer structure.

The piezoelectric layer28can include any suitable piezoelectric layer, such as a lithium niobate (LN) layer or a lithium tantalate (LT) layer. A thickness of the piezoelectric layer28can be selected based on a wavelength λ or L of a surface acoustic wave generated by the SAW resonator2.

By having the second pitch (λ1) and the third pitch (λ2) of the reflector structures narrower than the first pitch (λ0) of the IDT electrode20, an additional resonance can be generated by a reflector side, as shown in the graph ofFIG.2D. In the frequency response of the SAW resonator2, two notches can be present as opposed to the one notch present in the frequency response of the SAW resonator1. The first to third pitches (λ0), (λ1), (λ2) can contribute to shifting a notch in the frequency response. For example, when the second pitch (λ1) and the third pitch (λ2) of the reflector structures are narrowed, the higher resonance can be shifted up to a higher frequency. Accordingly, the first to third pitches (λ0), (λ1), (λ2) can be selected at least in part by the desired response frequency. For example, a difference between the second pitch (λ1) and/or the third pitch (λ2), and the first pitch (λ0) can relate to a difference between the main resonance and the reflector sub-resonance. In some embodiments, the second pitch (λ1) and the third pitch (λ2) can be different. By varying the second pitch (λ1) and the third pitch (λ2), additional notches can be obtained in the frequency response.

In some embodiments, the first pitch (λ0) can be greater than the second pitch (λ1) and the third pitch (λ2), and be less than 120% of the second pitch (λ1) and/or the third pitch (λ2). For example, the first pitch (λ0) can be about 1% to 20%, about 10% to 20%, or about 15% to 20% greater than the second pitch (λ1) and/or the third pitch (λ2). The second pitch (λ1) and the third pitch (λ2) can be sufficiently wide so as to prevent a significant degradation of a main resonance peak. The second pitch (λ1) and the third pitch (λ2) can be determined based at least in part on manufacturing limitations for forming the reflectors.

The number of reflectors in the first set of reflectors24and the number of reflectors in the second set of reflectors26can affect reflection of the SAW resonator2and/or the Q in the frequency response of the SAW resonator2. A material property (e.g., mass density) of the first set of reflectors24and the second set of reflectors26can affect the reflection of the SAW resonator2and/or the Q in the frequency response of the SAW resonator2. For example, when the SAW resonator2has more numbers of the first set of reflectors24and the second set of reflectors26, a deeper drop in the notch(es) can be generated in the frequency response. When the reflection is 1 or 100%, a gamma value can be 1. Therefore, typically, a higher reflection can be desired for a one port resonator. However, it may be challenging to obtain 100% of reflection when the filter pass band is relatively wide. Accordingly, the first set of reflectors24and the second set of reflectors26can be designed based at least in part on desired frequency response.

The simulated results in the graph ofFIG.2Dinclude simulated admittance result of the SAW resonator1. Two resonances are observed from the graph. Therefore, the SAW resonator2can be suitable when at least two resonant frequencies are desired. Also, as compared to the graph ofFIG.1C, in the graph ofFIG.2D, it can be observed that the reflector stop band is shifted higher and larger margin at high-edge of passband is present. As described above, first to third pitches (λ0), (λ1), (λ2) and the number of reflectors of the first set of reflectors24and the second set of reflectors26can be selected to achieve two or more resonant frequencies while achieving a relatively high Q.

FIG.3is a graph that compares a simulated frequency response30of the SAW resonator1ofFIG.1Aand a simulated frequency response32of the SAW resonator2ofFIG.2Aused as shunt resonators in a ladder band pass filter. In an area indicated by a dashed line34inFIG.3, the simulated frequency response32of the SAW resonator2shows that the SAW resonator2achieves two frequencies in the transmit rejection. Conventionally, in order to achieve two or more resonance frequencies, two or more different types of resonators were used. Using two or more types of resonators, especially when the filter pass band is larger, may cause spurious mode which degrades the filter performance. However, the SAW resonator2can achieve two or more resonance frequencies in the transmit rejection without a significant degradation of the Q as compared to the SAW resonator1.

Various embodiments of SAW devices will now be discussed with reference toFIGS.4to6. Any suitable principles and advantages of the SAW devices disclosed herein can be implemented together with each other.

FIG.4illustrates a top plan view of a SAW resonator3according to another embodiment. Unless otherwise noted, components of the SAW resonator3may be the same or generally similar to like components of any surface acoustic wave resonator disclosed herein.

The SAW resonator3is generally similar to the SAW resonator2illustrated inFIG.2A. Unlike the SAW resonator2, the SAW resonator3has an asymmetric reflector structure. In the SAW resonator3, a number of reflectors of a first set of reflectors24is greater than a number of reflectors of a second set of reflectors26′. By varying the numbers of the reflectors in of the first set of reflectors24and the second set of reflectors26′, additional notches can be obtained in the frequency response. The number of reflectors of the first set of reflectors24in the SAW resonators2,3are kept the same, and the number of the second set of reflectors26′ of the SAW resonator3is fewer than the number of second set of reflectors26of SAW resonator2in the illustrated embodiments. However, any suitable number of reflectors can be selected.

IDT fingers22of an IDT electrode20has a first pitch (λ0) corresponding to a resonant frequency, the first set of reflectors24has a second pitch (λ1), and a second set of reflectors26has a third pitch (λ2). The second pitch (λ1) and the third pitch (λ2) can be the same or different. In some embodiments, the first pitch (λ0) is greater than the second pitch (λ1) and the third pitch (λ2).

FIG.5illustrates a top plan view of a multimode longitudinally coupled SAW (MMS) resonator4according to an embodiment. Unless otherwise noted, components of the MMS resonator4may be the same or generally similar to like components of any surface acoustic wave resonator disclosed herein.

The MMS resonator4can be a double mode SAW (DMS) filter. The MMS resonator4can include a first IDT electrode40with IDT fingers42having a fourth pitch (λ3) corresponding to a resonant frequency, a second IDT electrode44with IDT fingers46having a fifth pitch (λ4) corresponding to a resonant frequency, a third IDT electrode48with IDT fingers50having a sixth pitch (λ5) corresponding to a resonant frequency, and a pair of reflector structures that includes a first set of reflectors24having a second pitch (λ1) and a second set of reflectors26having a third pitch (λ2). The second pitch (λ1) and the third pitch (λ2) can be the same or different. The fourth pitch (λ3), the fifth pitch (λ4), and sixth pitch (λ5) can be the same or different. In some embodiments, at least one of the fourth pitch (λ3), the fifth pitch (λ4), and sixth pitch (λ5) can be greater than the second pitch (λ1) and/or the third pitch (λ2). In some embodiments, the MMS resonator4can have an asymmetric reflector structure.

FIG.6illustrates a cross section of a temperature compensated surface acoustic wave TC-SAW resonator5according to an embodiment. Unless otherwise noted, components of the SAW resonator3may be the same or generally similar to like components of any surface acoustic wave resonator disclosed herein.

The TC-SAW resonator5can include an interdigital transducer (IDT) electrode60with IDT fingers62having a first pitch (λ0) corresponding to a resonant frequency, and a pair of reflector structures that includes a first set of reflectors64having a second pitch (λ1) and a second set of reflectors66having a third pitch (λ2). The IDT electrode60, the first set of reflectors64, and the second set of reflectors66can be positioned over a piezoelectric layer28. The piezoelectric layer28can be positioned over a support substrate70. A temperature compensation layer72can be provided over the piezoelectric layer28. A dispersion adjustment layer74can be provided over the temperature compensation layer72. In some embodiments, there may be an intermediate layer (not shown) between the piezoelectric layer28and the support substrate70.

As show inFIG.6, the IDT electrode60and the reflectors64,66can have multiple layers of different materials. For example, one layer (e.g., a bottom layer) can be tungsten (W) and another layer (e.g., an upper layer) can be aluminum (Al) in certain embodiments. As another example, the lower layer can be aluminum (Al) and the upper layer can be tungsten (W), in certain embodiments. The bottom layer may include one or more other metals, such as copper (Cu), Magnesium (Mg), titanium (Ti), molybdenum (Mo), etc. The bottom layer may include alloys, such as AlMgCu, AlCu, etc. The upper layer may include one or more other metals, such as copper (Cu), Magnesium (Mg), titanium (Ti), molybdenum (Mo), etc. The upper layer may include alloys, such as AlMgCu, AlCu, etc. In some applications, the bottom layer of the IDT electrode60can impact acoustic properties of the TC-SAW resonator and the upper layer of the IDT electrode60can impact electrical properties of the SAW resonator, in some embodiments.

The support substrate70can be any suitable substrate layer, such as a silicon layer, a quartz layer, a ceramic layer, a glass layer, a spinel layer, a magnesium oxide spinel layer, a sapphire layer, a diamond layer, a silicon carbide layer, a silicon nitride layer, an aluminum nitride layer, or the like.

The temperature compensation layer72can include any suitable temperature compensation material. For example, the temperature compensation layer72can be a silicon dioxide (SiO2) layer. The temperature compensation layer72can be a layer of any other suitable material having a positive temperature coefficient of frequency for SAW resonators with a piezoelectric layer having a negative coefficient of frequency. For instance, the temperature compensation layer72can be a tellurium dioxide (TeO2) layer or a silicon oxyfluoride (SiOF) layer in certain applications. The temperature compensation layer72can include any suitable combination of SiO2, TeO2, and/or SiOF.

The dispersion adjustment layer74can be a SiN layer disposed entirely over an upper surface of the temperature compensation layer72. However, the dispersion adjustment layer74may be partially disposed over the upper surface of the temperature compensation layer72. In certain applications, the dispersion adjustment layer74can include another suitable material, such as a silicon oxynitride (SiON) layer. According to some applications, the dispersion adjustment layer can include SiN and another material. The dispersion adjustment layer74can also function as a passivation layer.

An MMS filter, a SAW resonator, and/or a lamb wave device including any suitable combination of features disclosed herein can be included in a filter arranged to filter a radio frequency signal in a fifth generation (5G) New Radio (NR) operating band within Frequency Range 1 (FR1). A filter arranged to filter a radio frequency signal in a 5G NR operating band can include one or more MPS SAW resonators disclosed herein. FR1 can be from 410 MHz to 7.125 GHz, for example, as specified in a current 5GNR specification. MMS filters disclosed herein can be implemented with less pitch variation than some previous MMS filters. MMS filters disclosed herein can filter higher frequency signals with the same IDT electrode line and space process limitations compared to some previous MMS filters. Filtering higher frequency signals can be advantageous in 5G applications. One or more MMS filters and/or SAW resonators in accordance with any suitable principles and advantages disclosed herein can be included in a filter arranged to filter a radio frequency signal in a fourth generation (4G) Long Term Evolution (LTE) operating band and/or in a filter having a passband that includes a 4G LTE operating band and a 5G NR operating band.

Acoustic wave filters disclosed herein can have a ladder filter topology.FIG.7is a schematic diagram of a ladder filter110that includes a shunt resonator according to an embodiment. The ladder filter110is an example topology of a band pass filter formed from acoustic wave resonators. In a band pass filter with a ladder filter topology, the shunt resonators can have lower resonant frequencies than the series resonators. The ladder filter110can be arranged to filter an RF signal. As illustrated, the ladder filter110includes series acoustic wave resonators111,113,115,117, and119and shunt acoustic wave resonators112,114,116, and118coupled between an RF port RF and an antenna port ANT. The acoustic wave resonators of the ladder filter110can include any suitable acoustic wave resonators. The RF port can be a transmit port for a transmit filter or a receive port for a receive filter. Any suitable number of series acoustic wave resonators can be included in a ladder filter. Any suitable number of shunt acoustic wave resonators can be included in a ladder filter. Any of the illustrated shunt acoustic wave resonators112,114,116, and118can have multiple resonant frequencies in accordance with any suitable principles and advantages disclosed herein. In certain instances, a single shunt resonator of the ladder filter110has multiple resonant frequencies in accordance with any suitable principles and advantages disclosed herein. In some other instances, two or more shunt resonators of the ladder filter110can have multiple resonant frequencies in accordance with any suitable principles and advantages disclosed herein.

Acoustic wave filters disclosed herein can have a lattice filter topology.FIG.8is a schematic diagram of a lattice filter120that includes a resonator according to an embodiment. The lattice filter120is an example topology of a band pass filter formed from acoustic wave resonators. The lattice filter120can be arranged to filter an RF signal. As illustrated, the lattice filter120includes acoustic wave resonators122,124,126, and128. The acoustic wave resonators122and124are considered series resonators. The acoustic wave resonators126and128are considered shunt resonators. The illustrated lattice filter120has a balanced input and a balanced output. The illustrated acoustic wave resonators126and/or128can have multiple resonant frequencies in accordance with any suitable principles and advantages disclosed herein.

In some instances, an acoustic wave filter that includes a shunt resonator having two or more resonant frequencies can have a topology that is a hybrid of a ladder filter and a lattice filter. According to certain applications, an acoustic wave shunt resonator having two or more resonant frequencies can be included in filter that also includes one or more inductors and one or more capacitors.

FIG.9is a schematic diagram of a duplexer130according to an embodiment. The duplexer130includes a first filter132and a second filter134coupled together at an antenna node ANT. The antenna node ANT is a common node of the duplexer130. A shunt inductor L1is also coupled to the first filter132and the second filter134at the antenna node ANT. The duplexer130can be a diversity receive duplexer in which the first filter132is a receive filter and the second filter134is a receive filter. As an illustrative example, the first filter132can be a Band3receive filter and the second filter134can be a Band66receive filter.

The first filter132includes a plurality of acoustic wave resonators. As illustrated, the first filter132is a ladder filter. The acoustic wave resonators of the first filter132include series resonators RA1, RA3, RA5, RA7, and RA9and shunt resonators RA2, RA4, RA6, RA8, RAA, and RAAb. One or more of the shunt resonators RA2, RA4, RA6, RA8, RAA, and RAAb can have a plurality of resonant frequencies. The first filter132also includes a series inductor L2coupled between the plurality of acoustic wave resonators and an RF port RF_OUT1. The first filter132includes a shunt inductor LCuB3. In certain applications, the first filter132can have the frequency response similar to that shown inFIG.2D. In such applications, the shunt resonator RA2can have two resonant frequencies corresponding to the curve inFIG.2D.

The second filter134includes a plurality of acoustic wave resonators. The acoustic wave resonators of the second filter134include series resonators RB1, RB2, and RB4, shunt resonators RB3and RB5, and double mode SAW (DMS) elements D4A and D4B. The shunt resonator RB3and/or the shunt resonator RB4can have a plurality of resonant frequencies in accordance with any suitable principles and advantages disclosed herein in certain embodiments. The second filter134also includes a series inductor L3coupled between the plurality of acoustic wave resonators and an RF port RF_OUT2.

Acoustic wave resonators of the duplexer130can be TC-SAW resonators. Such TC-SAW resonators can have temperature compensation layers of different thicknesses.FIG.10is a schematic diagram of a cross section of surface acoustic wave resonators of the duplexer130ofFIG.9according to an embodiment. As shown inFIG.10, an acoustic wave component135includes TC-SAW resonators136A,136B, and136C. One or more of the TC-SAW resonators136A,136B, and136C can have two or more resonant frequencies in accordance with any suitable principles and advantages disclosed herein. The acoustic wave component135includes a piezoelectric layer137and IDT electrodes138A,138B, and138C on the piezoelectric layer137. A temperature compensation layer139is positioned over the IDT electrodes138A,138B, and138C and the piezoelectric layer137. The piezoelectric layer137can be a lithium niobate layer. The temperature compensation layer139can be a silicon dioxide layer.

The temperature compensation layer139has a plurality of different thicknesses over respective IDT electrodes138A,138B, and138C. The temperature compensation layer139being thicker can result in TCF closer to zero and lower Q and electromechanical coupling coefficient (k2). The temperature compensation layer139can be have different thicknesses such that certain resonators have TCF closer to zero and other resonators have higher Q and k2. The first TC-SAW resonator136A has a first thickness H1of the temperature compensation layer139over the piezoelectric layer137. The second TC-SAW resonator136B has a second thickness H2of the temperature compensation layer139over the piezoelectric layer137. The third TC-SAW resonator136C has a third thickness H3of the temperature compensation layer139over the piezoelectric layer137. As shown inFIG.10, the third thickness H3is greater than the second thickness H2and the second thickness H2is greater than the first thickness H1.

In an embodiment of the duplexer130, acoustic wave resonators RA1, RB1, RB2, RB4can be TC-SAW resonators with the first thickness H1like the TC-SAW resonator136A, acoustic wave resonators RA7, RA9, RB3, and RB5can be TC-SAW resonators with the second thickness H2like the TC-SAW resonator136B, and acoustic wave resonators RA2, RA3, RA4, RA5, RA6, RA8, RAA, and RAAb can be TCSAW resonators with the third thickness H3like the TC-SAW resonator136C.

FIG.11Ais a schematic diagram of a duplexer140that includes an acoustic wave filter according to an embodiment. The duplexer140includes a first filter142and a second filter144coupled together at a common node COM. One of the filters of the duplexer140can be a transmit filter and the other of the filters of the duplexer140can be a receive filter. The transmit filter and the receive filter can be respective ladder filters with acoustic wave resonators having a topology similar to the ladder filter110ofFIG.7. In some other instances, such as in a diversity receive application, the duplexer140can include two receive filters. The common node COM can be an antenna node.

The first filter142is an acoustic wave filter arranged to filter a radio frequency signal. The first filter142can include acoustic wave resonators coupled between a first radio frequency node RF1and the common node. The first radio frequency node RF1can be a transmit node or a receive node. The first filter142includes a shunt acoustic wave resonator having multiple resonant frequencies in accordance with any suitable principles and advantages disclosed herein.

The second filter144can be any suitable filter arranged to filter a second radio frequency signal. The second filter144can be, for example, an acoustic wave filter, an acoustic wave filter that includes shunt resonator with multiple resonant frequencies, an LC filter, a hybrid acoustic wave LC filter, or the like. The second filter144is coupled between a second radio frequency node RF2and the common node. The second radio frequency node RF2can be a transmit node or a receive node.

Although example embodiments may be discussed with filters or duplexers for illustrative purposes, any suitable principles and advantages disclosed herein can be implement in a multiplexer that includes a plurality of filters coupled together at a common node. Examples of multiplexers include but are not limited to a duplexer with two filters coupled together at a common node, a triplexer with three filters coupled together at a common node, a quadplexer with four filters coupled together at a common node, a hexaplexer with six filters coupled together at a common node, an octoplexer with eight filters coupled together at a common node, or the like. One or more filters of a multiplexer can include a shunt acoustic wave resonator having multiple resonant frequencies. Multiplexers include multiplexers with fixed multiplexing and multiplexers with switched multiplexing.

FIG.11Bis a schematic diagram of a multiplexer145that includes an acoustic wave filter according to an embodiment. The multiplexer145includes a plurality of filters142to144coupled together at a common node COM. The plurality of filters can include any suitable number of filters including, for example, 3 filters, 4 filters, 5 filters, 6 filters, 7 filters, 8 filters, or more filters. Some or all of the plurality of acoustic wave filters can be acoustic wave filters.

The first filter142is an acoustic wave filter arranged to filter a radio frequency signal. The first filter142can include acoustic wave resonators coupled between a first radio frequency node RF1and the common node. The first radio frequency node RF1can be a transmit node or a receive node. The first filter142includes a shunt acoustic wave resonator having multiple resonant frequencies in accordance with any suitable principles and advantages disclosed herein. The other filter(s) of the multiplexer145can include one or more acoustic wave filters, one or more acoustic wave filters that include a shunt resonator with multiple resonant frequencies, one or more LC filters, one or more hybrid acoustic wave LC filters, or any suitable combination thereof.

The acoustic wave resonators with multiple resonant frequencies disclosed herein can be implemented in a variety of packaged modules. Some example packaged modules will now be disclosed in which any suitable principles and advantages of the acoustic wave filters and/or acoustic wave resonators disclosed herein can be implemented. The example packaged modules can include a package that encloses the illustrated circuit elements. A module that includes a radio frequency component can be referred to as a radio frequency module. The illustrated circuit elements can be disposed on a common packaging substrate. The packaging substrate can be a laminate substrate, for example.FIGS.12to15are schematic block diagrams of illustrative packaged modules according to certain embodiments. Any suitable combination of features of these packaged modules can be implemented with each other. While duplexers are illustrated in the example packaged modules ofFIGS.13to15, any other suitable multiplexer that includes a plurality of filters coupled to a common node can be implemented instead of one or more duplexers. For example, a quadplexer can be implemented in certain applications. Alternatively or additionally, one or more filters of a packaged module can be arranged as a transmit filter or a receive filter that is not included in a multiplexer.

FIG.12is a schematic diagram of a radio frequency module150that includes an acoustic wave component152according to an embodiment. The illustrated radio frequency module150includes the acoustic wave component152and other circuitry153. The acoustic wave component152can include one or more acoustic wave in accordance with any suitable combination of features of the acoustic wave filters and/or acoustic wave resonators disclosed herein. The acoustic wave component152can include a SAW die that includes SAW resonators, for example.

The acoustic wave component152shown inFIG.12includes one or more acoustic wave filters154and terminals155A and155B. The one or more acoustic wave filters154can include an acoustic wave resonator having multiple resonant frequencies implemented in accordance with any suitable principles and advantages disclosed herein. The terminals155A and154B can serve, for example, as an input contact and an output contact. Although two terminals are illustrated, any suitable number of terminals can be implemented for a particular application. The acoustic wave component152and the other circuitry153are on a common packaging substrate156inFIG.12. The package substrate156can be a laminate substrate. The terminals155A and155B can be electrically connected to contacts157A and157B, respectively, on the packaging substrate156by way of electrical connectors158A and158B, respectively. The electrical connectors158A and158B can be bumps or wire bonds, for example.

The other circuitry153can include any suitable additional circuitry. For example, the other circuitry can include one or more power amplifiers, one or more radio frequency switches, one or more additional filters, one or more low noise amplifiers, one or more RF couplers, one or more delay lines, one or more phase shifters, the like, or any suitable combination thereof. The other circuitry153can be electrically connected to the one or more acoustic wave filters154. The radio frequency module150can include one or more packaging structures to, for example, provide protection and/or facilitate easier handling of the radio frequency module150. Such a packaging structure can include an overmold structure formed over the packaging substrate156. The overmold structure can encapsulate some or all of the components of the radio frequency module150.

FIG.13is a schematic block diagram of a module160that includes duplexers161A to161N and an antenna switch162. One or more filters of the duplexers161A to161N can include an acoustic wave resonator with two or more resonant frequencies in accordance with any suitable principles and advantages disclosed herein. Any suitable number of duplexers161A to161N can be implemented. The antenna switch162can have a number of throws corresponding to the number of duplexers161A to161N. The antenna switch162can include one or more additional throws coupled to one or more filters external to the module160and/or coupled to other circuitry. The antenna switch162can electrically couple a selected duplexer to an antenna port of the module160.

FIG.14is a schematic block diagram of a module170that includes a power amplifier176, a radio frequency switch178, and duplexers161A to161N according to an embodiment. The power amplifier176can amplify a radio frequency signal. The radio frequency switch178can be a multi-throw radio frequency switch. The radio frequency switch178can electrically couple an output of the power amplifier176to a selected transmit filter of the duplexers161A to161N. One or more filters of the duplexers161A to161N can include any suitable number of acoustic wave resonators that have a plurality of resonant frequencies in accordance with any suitable principles and advantages disclosed herein. Any suitable number of duplexers161A to161N can be implemented.

FIG.15is a schematic diagram of a radio frequency module180that includes an acoustic wave filter according to an embodiment. As illustrated, the radio frequency module180includes duplexers161A to161N that include respective transmit filters183A1to183N1and respective receive filters183A2to183N2, a power amplifier176, a select switch178, and an antenna switch162. The radio frequency module180can include a package that encloses the illustrated elements. The illustrated elements can be disposed on a common packaging substrate187. The packaging substrate187can be a laminate substrate, for example. A radio frequency module that includes a power amplifier can be referred to as a power amplifier module. A radio frequency module can include a subset of the elements illustrated inFIG.15and/or additional elements. The radio frequency module180may include any one of the acoustic wave devices with a plurality of resonant frequencies in accordance with any suitable principles and advantages disclosed herein.

The duplexers161A to161N can each include two acoustic wave filters coupled to a common node. For example, the two acoustic wave filters can be a transmit filter and a receive filter. As illustrated, the transmit filter and the receive filter can each be a band pass filter arranged to filter a radio frequency signal. One or more of the transmit filters183A1to183N1can include an acoustic wave resonator with a plurality of resonant frequencies in accordance with any suitable principles and advantages disclosed herein. Similarly, one or more of the receive filters183A2to183N2can include an acoustic wave resonator with a plurality of resonant frequencies in accordance with any suitable principles and advantages disclosed herein. AlthoughFIG.15illustrates duplexers, any suitable principles and advantages disclosed herein can be implemented in other multiplexers (e.g., quadplexers, hexaplexers, octoplexers, etc.) and/or in switch-plexers.

The power amplifier176can amplify a radio frequency signal. The illustrated switch178is a multi-throw radio frequency switch. The switch178can electrically couple an output of the power amplifier176to a selected transmit filter of the transmit filters183A1to183N1. In some instances, the switch178can electrically connect the output of the power amplifier176to more than one of the transmit filters183A1to183N1. The antenna switch162can selectively couple a signal from one or more of the duplexers161A to161N to an antenna port ANT. The duplexers161A to161N can be associated with different frequency bands and/or different modes of operation (e.g., different power modes, different signaling modes, etc.).

The filters with an acoustic wave resonator having a plurality of resonant frequencies disclosed herein can be implemented in a variety of wireless communication devices.FIG.16Ais a schematic diagram of a wireless communication device190that includes filters193in a radio frequency front end192according to an embodiment. One or more of the filters193can include an acoustic wave resonator having a plurality of resonant frequencies in accordance with any suitable principles and advantages disclosed herein. The wireless communication device190can be any suitable wireless communication device. For instance, a wireless communication device190can be a mobile phone, such as a smart phone. As illustrated, the wireless communication device190includes an antenna191, an RF front end192, a transceiver194, a processor195, a memory196, and a user interface197. The antenna191can transmit RF signals provided by the RF front end192. Such RF signals can include carrier aggregation signals. The antenna191can receive RF signals and provide the received RF signals to the RF front end192for processing. Such RF signals can include carrier aggregation signals. The wireless communication device190can include two or more antennas in certain instances.

The RF front end192can include one or more power amplifiers, one or more low noise amplifiers, one or more RF switches, one or more receive filters, one or more transmit filters, one or more duplex filters, one or more multiplexers, one or more frequency multiplexing circuits, the like, or any suitable combination thereof. The RF front end192can transmit and receive RF signals associated with any suitable communication standards. One or more of the filters193can include an acoustic wave resonator with a plurality of resonant frequencies that includes any suitable combination of features of the embodiments disclosed above.

The transceiver194can provide RF signals to the RF front end192for amplification and/or other processing. The transceiver194can also process an RF signal provided by a low noise amplifier of the RF front end192. The transceiver194is in communication with the processor195. The processor195can be a baseband processor. The processor195can provide any suitable base band processing functions for the wireless communication device190. The memory196can be accessed by the processor195. The memory196can store any suitable data for the wireless communication device190. The user interface197can be any suitable user interface, such as a display with touch screen capabilities.

FIG.16Bis a schematic diagram of a wireless communication device200that includes filters193in a radio frequency front end192and second filters203in a diversity receive module202. The wireless communication device200is like the wireless communication device190ofFIG.16A, except that the wireless communication device200also includes diversity receive features. As illustrated inFIG.16B, the wireless communication device200includes a diversity antenna201, a diversity module202configured to process signals received by the diversity antenna201and including filters203, and a transceiver194in communication with both the radio frequency front end192and the diversity receive module202. One or more of the second filters203can include an acoustic wave resonator having a plurality of resonant frequencies in accordance with any suitable principles and advantages disclosed herein.

Although embodiments disclosed herein relate to surface acoustic wave filters and/or resonators, any suitable principles and advantages disclosed herein can be applied to other types of acoustic wave devices that include an IDT electrode, such as Lamb wave devices and/or boundary wave devices. For example, any suitable combination of features of the acoustic velocity adjustment structures disclosed herein can be applied to a Lamb wave device and/or a boundary wave device.

Any of the embodiments described above can be implemented in association with mobile devices such as cellular handsets. The principles and advantages of the embodiments can be used for any systems or apparatus, such as any uplink wireless communication device, that could benefit from any of the embodiments described herein. The teachings herein are applicable to a variety of systems. Although this disclosure includes some example embodiments, the teachings described herein can be applied to a variety of structures. Any of the principles and advantages discussed herein can be implemented in association with RF circuits configured to process signals in a frequency range from about 30 kHz to 300 GHz, such as in a frequency range from about 450 MHz to 8.5 GHz. Acoustic wave resonators and/or filters disclosed herein can filter RF signals at frequencies up to and including millimeter wave frequencies.

Aspects of this disclosure can be implemented in various electronic devices. Examples of the electronic devices can include, but are not limited to, consumer electronic products, parts of the consumer electronic products such as packaged radio frequency modules and/or packaged filter components, uplink wireless communication devices, wireless communication infrastructure, electronic test equipment, etc. Examples of the electronic devices can include, but are not limited to, a mobile phone such as a smart phone, a wearable computing device such as a smart watch or an ear piece, a telephone, a television, a computer monitor, a computer, a modem, a hand-held computer, a laptop computer, a tablet computer, a microwave, a refrigerator, a vehicular electronics system such as an automotive electronics system, a stereo system, a digital music player, a radio, a camera such as a digital camera, a portable memory chip, a washer, a dryer, a washer/dryer, a copier, a facsimile machine, a scanner, a multi-functional peripheral device, a wrist watch, a clock, etc. Further, the electronic devices can include unfinished products.