Filter, filter assembly and carrier aggregation system

Abstract

A filter for a carrier aggregation system, the filter passing a first band of a carrier aggregation signal, includes a surface acoustic wave device 10 including a quartz crystal substrate 12, an interdigital transducer electrode, and a lithium tantalate (LiTaO) layer 14 positioned between the quartz crystal substrate 12 and the interdigital transducer (IDT) electrode 16. [Effect] The filter suppresses higher-order spurious modes corresponding to the second band of the carrier aggregation signal.

Description

[Technical Field]

[0001] Embodiments of the present disclosure relate to filters that include surface acoustic wave devices.

[0002] Cross-reference to priority application Any and all asserted applications for which a foreign or domestic priority claim is identified in an Application Data Sheet filed herewith are hereby incorporated by reference pursuant to Section 1.57 of the U.S.C. This application claims the benefit of priority under Section 119(e) of U.S. Provisional Patent Application No. 62 / 547,610, entitled "Filter with Surface Acoustic Wave Device for Carrier Aggregation System," filed August 18, 2017, the disclosure of which is incorporated herein by reference in its entirety. [Background technology]

[0003] An acoustic wave filter may include multiple resonators arranged to filter radio frequency signals. Examples of acoustic wave filters include surface acoustic wave (SAW) filters and bulk acoustic wave (BAW) filters. A film bulk acoustic resonator (FBAR) filter is an example of a BAW filter.

[0004] Acoustic wave filters can be implemented in radio frequency electronic systems. For example, filters in the radio frequency front end of a mobile phone may include an acoustic wave filter. Multiple acoustic wave filters can be arranged as a multiplexer. For example, two surface acoustic wave filters can be arranged as a duplexer. Summary of the Invention

[0005] Each claimed innovation has several aspects, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of the claims, a summary of some prominent features of the present disclosure is set forth below.

[0006] One aspect of the present disclosure is a filter for a carrier aggregation system. The filter includes a surface acoustic wave device including a quartz crystal substrate, an interdigital transducer electrode, and a lithium-based piezoelectric layer positioned between the quartz crystal substrate and the interdigital transducer electrode. The surface acoustic wave device is configured to suppress higher-order spurious modes corresponding to a second band of the carrier aggregation signal. The filter is configured to pass a first band of the carrier aggregation signal.

[0007] The quartz crystal substrate may have a cut angle ranging from 20° to 52°, where the cut angle is the rotation angle of the Y-cut X-propagation.

[0008] The lithium-based piezoelectric layer may be a lithium tantalate layer. The surface acoustic wave device is configured to generate a surface acoustic wave having a wavelength λ. The lithium tantalate layer may have a thickness in the range of 0.15λ to 1.4λ. The lithium tantalate layer may have a cut angle in the range of 10° to 50°.

[0009] The filter may be a transmit filter, with the first band being a transmit band and the second band being a receive band.The filter may be a receive filter, with the first band being a transmit band and the second band being a transmit band.

[0010] The filter may be configured to suppress other higher order spurious modes corresponding to a third band of the carrier aggregation signal.

[0011] The surface acoustic wave device can be configured to operate in a shear-horizontal mode and can have a speed of sound in the range of 3,800 meters / second to 4,200 meters / second.

[0012] The lithium-based piezoelectric layer can be bonded to a quartz substrate.

[0013] The surface acoustic wave device further includes an additional layer disposed between the lithium-based piezoelectric layer and the quartz substrate, the additional layer configured to increase the quality factor of the surface acoustic wave device.

[0014] Another aspect of the present disclosure is a filter assembly for a carrier aggregation system. The filter assembly includes a first filter and a second filter. The first filter includes a surface acoustic wave device including a quartz crystal substrate, an interdigital transducer electrode, and a lithium-based piezoelectric layer positioned between the quartz crystal substrate and the interdigital transducer electrode. The surface acoustic wave device is configured to suppress higher-order spurious modes corresponding to a second band of the carrier aggregation signal. The first filter is configured to pass the first band of the carrier aggregation signal. The second filter is configured to pass the second band of the carrier aggregation signal.

[0015] The first filter may be a transmit filter and the second filter may be a receive filter. The first filter may be a receive filter and the second filter may be a transmit filter. The filter assembly includes a multiplexer including the first filter and the second filter.

[0016] Another aspect of the present disclosure is a carrier aggregation system including a frequency multiplexing circuit, the frequency multiplexing circuit including a terminal to which a carrier aggregated signal is applied and a multiplexer in communication with the frequency multiplexing circuit. The multiplexer includes a filter coupled to a common node. The filter includes a first filter configured to pass a first band of the carrier aggregated signal. The first filter includes a surface acoustic wave device including a quartz crystal substrate, interdigital transducer electrodes, and a lithium-based piezoelectric layer positioned between the quartz crystal substrate and the interdigital transducer electrodes. The surface acoustic wave device is configured to suppress higher-order spurious modes corresponding to a second band of the carrier aggregated signal.

[0017] The frequency multiplexing circuit may be a diplexer. The multiplexer may be a duplexer. The carrier aggregation system further includes a power amplifier and a switch coupled between the power amplifier and the first filter.

[0018] Another aspect of the present disclosure is a package module for a carrier aggregation system. The package module includes a first filter configured to pass a first band of a carrier aggregation signal, a second filter configured to filter the carrier aggregation signal, and a package enclosing the first and second filters. The first filter includes a surface acoustic wave device including a quartz crystal substrate, an interdigital transducer electrode, and a lithium tantalate layer positioned between the quartz crystal substrate and the interdigital transducer electrode. The surface acoustic wave device is configured to suppress higher-order spurious modes corresponding to the second band of the carrier aggregation signal.

[0019] The package module may further include a power amplifier configured to provide a radio frequency signal to at least one of the first filter or the second filter. The claimed package module may include a multi-throw switch coupled to the first filter and the second filter. The multi-throw switch may have a single throw coupled to a common node, and the first filter may be coupled to the second filter at the common node. The multi-throw switch may have a first throw coupled to the first filter and a second throw coupled to the second filter.

[0020] Another aspect of the present disclosure is a wireless communication device including an antenna configured to receive a carrier aggregated signal and a multiplexer in communication with the antenna. The multiplexer includes a filter coupled to a common node. The filter includes a first filter configured to pass a first band of the carrier aggregated signal and a second filter configured to filter the carrier aggregated signal. The first filter includes a surface acoustic wave device including a quartz crystal substrate, an interdigital transducer electrode, and a lithium tantalate layer positioned between the quartz crystal substrate and the interdigital transducer electrode. The surface acoustic wave device is configured to suppress higher-order spurious modes corresponding to the second band of the carrier aggregated signal.

[0021] The wireless communication device may be a mobile phone. The wireless communication device further includes a frequency multiplexing circuit coupled between the common node and the antenna. The frequency multiplexing circuit may be a diplexer or a triplexer. The wireless communication device may further include an antenna switch coupled between the common node and the antenna. The antenna may be a primary antenna.

[0022] Another aspect of the present disclosure is a method of filtering a carrier-aggregated signal. The method includes passing a first band of the carrier-aggregated signal through a filter including a surface acoustic wave device. The surface acoustic wave device includes a quartz crystal substrate, an interdigital transducer electrode, and a lithium-based piezoelectric layer positioned between the quartz crystal substrate and the interdigital transducer electrode. The method also includes suppressing, with the first filter, higher-order spurious modes corresponding to a second band of the carrier-aggregated signal.

[0023] For purposes of summarizing the disclosure, certain aspects, advantages, and novel features of the innovation have been described herein. It is to be understood that not all such advantages may necessarily be achieved in accordance with any particular embodiment. That is, the innovation may be embodied or performed in a manner that achieves or optimizes one advantage or advantages taught herein without necessarily achieving other advantages taught or suggested herein. [Brief explanation of the drawings]

[0024] Several embodiments of the present disclosure are described below by way of non-limiting examples with reference to the accompanying drawings. [Figure 1A] 10 is a graph of transmission coefficient versus frequency when the filter has undesirable attenuation for a frequency band associated with a carrier aggregation signal. [Figure 1B] 10 is a graph of transmission coefficient versus frequency for a filter with desired attenuation for a frequency band associated with a carrier aggregation signal. [Figure 2A] 10 is a graph of transmission coefficient versus frequency when the filter has undesired attenuation for a frequency band associated with a carrier aggregation signal having three carriers. [Figure 2B] 10 is a graph of transmission coefficient versus frequency for a filter with desired attenuation for a frequency band associated with a carrier aggregation signal having three carriers. [Figure 3A] 1 is a cross-sectional view of a surface acoustic wave device according to an embodiment. [Figure 3-1] 3B-3E are graphs associated with a crystal cut angle sweep for various lithium tantalate layer thicknesses of the surface acoustic wave device of FIG. 3A. FIG. 3B is a graph of Qp versus crystal cut angle. FIG. 3C is a graph of Qs versus cut angle. FIG. 3D is a graph of electromechanical coupling coefficient (k2) versus cut angle. FIG. 3D is a graph of temperature coefficient of frequency (TCF) versus cut angle. [Figure 3-2]3F-3I are graphs associated with crystal cut angle sweeps for various lithium tantalate layer thicknesses of the surface acoustic wave device of FIG. 3A, corresponding to different crystal propagation angles than those of FIGS. 3B-3E. FIG. 3F is a graph of Qp vs. crystal cut angle. FIG. 3G is a graph of Qs vs. cut angle. FIG. 3H is a graph of k2 vs. cut angle. FIG. 3I is a graph of TCF vs. cut angle. [Figure 3J] 3B is a graph of quality factor versus lithium tantalate cut angle for the surface acoustic wave device of FIG. 3A. [Figure 3K] 3B is a graph of electromechanical coupling coefficient versus lithium tantalate cut angle for the surface acoustic wave device of FIG. 3A. [Figure 4] FIG. 10 is a cross-sectional view of another surface acoustic wave device. [Figure 5] FIG. 10 is a cross-sectional view of another surface acoustic wave device. [Figure 6A] 6 is a graph of the frequency response for the surface acoustic wave devices of FIGS. 3A, 4 and 5. [Figure 6B] 6 is a graph of electromechanical coupling coefficient (k2) versus frequency for the surface acoustic wave devices of FIGS. 3A, 4 and 5. [Figure 6C] 6 is a graph of quality factor versus frequency for the surface acoustic wave devices of FIGS. 3A, 4 and 5. FIG. [Figure 7A] 6 is a graph of transmission characteristics for the surface acoustic wave devices of FIGS. 3A, 4 and 5. [Figure 7B] 6 is a graph of the reflection characteristics for the surface acoustic wave devices of FIGS. [Figure 8A] 6 is a graph of Qs versus lithium tantalate cut angle for the surface acoustic wave devices of FIGS. 3A, 4 and 5. [Figure 8B] 6 is a graph of Qp versus lithium tantalate cut angle for the surface acoustic wave devices of FIGS. 3A, 4 and 5. [Figure 8C] 6 is a graph of electromechanical coupling coefficient versus lithium tantalate cut angle for the surface acoustic wave devices of FIGS. 3A, 4 and 5. FIG. [Figure 9A] 3B is a graph of Qs versus crystal cut angle for the surface acoustic wave device of FIG. 3A. [Figure 9B] 3B is a graph of Qp versus crystal cut angle for the surface acoustic wave device of FIG. 3A. [Figure 9C] 3B is a graph of electromechanical coupling coefficient versus crystal cut angle for the surface acoustic wave device of FIG. 3A. [Figure 10-1] 10A-10E are graphs associated with a lithium tantalate thickness sweep for the surface acoustic wave device of FIG. 3A. FIG. 10A illustrates ΔZSH and ΔZSP in frequency response. FIG. 10B shows the impedance ratios ΔZSH and ΔZSP versus lithium tantalate layer thickness. [Figure 10-2] Figure 10C is a graph of Qs versus lithium tantalate layer thickness for the surface acoustic wave devices of Figures 3A, 4, and 5. Figure 10D is a graph of Qs versus lithium tantalate layer thickness for the surface acoustic wave devices of Figures 3A, 4, and 5. Figure 10E is a graph of k2 versus lithium tantalate layer thickness for the surface acoustic wave devices of Figures 3A, 4, and 5. [Figure 11] 11A-11C are graphs associated with lithium tantalate propagation angle sweeps for the surface acoustic wave devices of FIGS. 3A, 4, and 5. FIG. 11A is a graph of Qs versus propagation angle. FIG. 11B is a graph of Qp versus propagation angle. FIG. 11C is a graph of k2 versus propagation angle. [Figure 12] 6 is a graph of sound velocity versus lithium tantalate thickness for the surface acoustic wave devices of FIGS. 3A, 4 and 5. [Figure 13] 1 is a cross-sectional view of a surface acoustic wave device according to an embodiment. [Figure 14] 14A-14D are graphs of parameters of the surface acoustic wave device of FIG. 13. FIG. 14A is a graph of silicon dioxide thickness vs. TCF. FIG. 14B is a graph of silicon dioxide thickness vs. Qs. FIG. 14C is a graph of silicon dioxide thickness vs. Qp. FIG. 14D is a graph of silicon dioxide thickness vs. k2. [Figure 15] 1 is a cross-sectional view of a surface acoustic wave device according to an embodiment. [Figure 16A] 1 is a cross-sectional view of a surface acoustic wave device according to an embodiment. [Figure 16B] 16B is a graph comparing electromechanical coupling coefficient versus lithium-based piezoelectric layer cut angle for the surface acoustic wave devices of FIGS. 3A and 16A. [Figure 17A] 1 is a schematic diagram of a carrier aggregation system according to an embodiment; [Figure 17B] 1 is a schematic diagram of a carrier aggregation system according to an embodiment; [Figure 17C] 1 is a schematic diagram of a carrier aggregation system according to an embodiment; [Figure 17D] 1 is a schematic diagram of a carrier aggregation system according to an embodiment; [Figure 18A] FIG. 1 is a schematic block diagram of a module including a filter according to one or more embodiments. [Figure 18B] FIG. 1 is a schematic block diagram of a module including a filter according to one or more embodiments. [Figure 19] 1 is a schematic block diagram of a wireless communication device including a filter according to one or more embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0025] The following description of certain embodiments represents various descriptions of particular embodiments. However, the innovations described herein may be embodied in many different forms, as defined and covered, for example, by the claims. In the drawings referred to in this description, like reference numbers may indicate identical or functionally similar elements. It is understood that the elements illustrated in the drawings are not necessarily to scale. It is further understood that a given embodiment may include more elements than illustrated in the drawings and / or may include a subset of the elements illustrated in the drawings. Furthermore, some embodiments may incorporate any suitable combination of features from two or more drawings.

[0026] In carrier aggregation systems, achieving a relatively high quality factor (Q) and high-order spurious mode suppression in surface acoustic wave filters can be difficult.

[0027] Some approaches to this difficulty include an acoustic wave device in which a relatively thin lithium tantalate (LT) layer is bonded onto a relatively high-impedance substrate (e.g., a silicon substrate, an aluminum nitride substrate, or a sapphire substrate). Such an approach can achieve a relatively high Q. However, such an approach can excite relatively strong high-order spurious modes. The spurious modes can make it difficult to achieve a specific attenuation in a high frequency range. This can be problematic in carrier aggregation systems. For example, a multiplexer such as a duplexer or quadplexer may not be able to meet the attenuation specifications for carrier aggregation applications with such spurious modes.

[0028] Aspects of the present disclosure relate to a surface acoustic wave device having a multilayer piezoelectric substrate including a lithium-based piezoelectric layer, such as a lithium tantalate layer or a lithium niobate layer, and a quartz substrate to provide a relatively high Q and suppress high-order spurious modes. The surface acoustic wave device may include a relatively thin lithium tantalate layer bonded to the quartz substrate. The high-order spurious modes can be suppressed by leakage into the crystal cut angle. The crystal cut angle may range from 20° to 52° for an R-rotated YX quartz crystal. The thickness of the lithium tantalate layer may range from 0.15λ to 1.4λ, where λ is the wavelength of the surface acoustic wave generated by the surface acoustic wave device.

[0029] By using quartz instead of a certain relatively high-impedance substrate, higher-order spurious modes can leak into the substrate. This can be attributed to the anisotropic characteristics of quartz. Quartz can behave as a high-impedance substrate at limited crystal cut angles. Therefore, the Q of a surface acoustic wave device including a lithium tantalate layer covering a quartz substrate can be improved compared to other devices by trapping acoustic waves in the lithium tantalate layer. Certain high-impedance substrates (e.g., silicon, aluminum nitride, or sapphire) can trap acoustic waves in the lithium tantalate layer. However, at the same time, higher-order spurious mode responses can also be trapped in the lithium tantalate layer associated with such high-impedance substrates. Therefore, in such situations, higher-order spurious responses may appear in the filter response. The bulk wave velocity of quartz is lower than that of other high-impedance materials such as silicon, aluminum nitride, and sapphire. Therefore, higher-order spurious mode responses may leak into quartz more easily than other high-impedance materials. The Q-factor associated with the spurious responses of higher modes can be reduced by leakage according to the principles and advantages described herein, thereby reducing the impact of spurious modes on the filter response. The temperature coefficient of frequency (TCF) can also be improved by using lithium tantalate coated quartz compared to using lithium tantalate alone.

[0030] FIG. 1A is a graph of transmission coefficient versus frequency for a filter with undesirable attenuation for a frequency band associated with a carrier aggregation signal. This graph corresponds to a two-band carrier aggregation case in which Bands N and M are aggregated. For example, a carrier aggregation signal may aggregate Band 1 and Band 3, where Band 1 has a transmit band of 1920 megahertz (MHz) to 1980 MHz and a receive band of 2110 MHz to 2170 MHz, and Band 3 has a transmit band of 1710 MHz to 1785 MHz and a receive band of 1805 MHz to 1880 MHz. The filter corresponding to the graph in FIG. 1A is a transmit filter configured to pass the Band N transmit frequency band. As shown in FIG. 1A, the frequency response of this filter provides insufficient attenuation corresponding to the Band M receive frequency band for a given application.

[0031] FIG. 1B is a graph of transmission coefficient versus frequency for a filter with a desired attenuation for a frequency band associated with a carrier aggregation signal. The filter corresponding to the graph of FIG. 1B is a transmit filter configured to pass the Band N transmit frequency band. As shown in FIG. 1B, this filter has a desired attenuation corresponding to the Band M receive frequency band. Thus, the filter corresponding to the graph of FIG. 1B can be used for carrier aggregation with Bands N and M.

[0032] A filter according to the principles and advantages described herein can achieve a frequency response similar to that shown in Figure 1B. The graph in Figure 1A illustrates the drawbacks of the previous approach associated with a lithium tantalate layer bonded to a relatively high impedance substrate, as discussed above.

[0033] 1A and 1B illustrate the frequency response of a transmit filter, any suitable principles and advantages described herein may also be implemented in a receive filter. For carrier aggregation signals with Bands N and M, it is desirable to have a relatively high attenuation in the Band M receive frequency band in the Band N transmit filter. Similarly, for carrier aggregation signals with Bands N and M, it is desirable to have a relatively high attenuation in the Band M transmit frequency band in the Band N receive filter.

[0034] 1A and 1B relate to a two-band carrier aggregation case. Any applicable principles and advantages described herein may be applied to carrier aggregation cases with three or more bands.

[0035] FIG. 2A is a graph of transmission coefficient versus frequency for a filter with undesirable attenuation for frequency bands associated with a carrier aggregation signal having three carriers. This graph corresponds to a three-band carrier aggregation case in which Bands N, M, and P are aggregated. For example, a carrier aggregation signal may aggregate Bands 1, 3, and 7. Band 1 may have a transmit band of 1920 MHz to 1980 MHz and a receive band of 2110 MHz to 2170 MHz, Band 3 may have a transmit band of 1710 MHz to 1785 MHz and a receive band of 1805 MHz to 1880 MHz, and Band 7 may have a transmit band of 2500 MHz to 2570 MHz and a receive band of 2620 MHz to 2690 MHz. The filter corresponding to the graph in FIG. 2A is a transmit filter configured to pass the Band N transmit frequency band. As shown in FIG. 2A, the frequency response of this filter may provide insufficient attenuation corresponding to the Band M and Band P receive frequency bands for a given application.

[0036] 2B is a graph of transmission coefficient versus frequency for a filter with desired attenuation for a frequency band associated with a carrier aggregation signal having three carriers. The filter corresponding to the graph of FIG. 2B is a transmit filter configured to pass the Band N transmit frequency band. As shown in FIG. 2B, this filter has desired attenuation corresponding to the Band M receive frequency band and the Band P receive frequency band. A filter according to the principles and advantages described herein can achieve a frequency response similar to that shown in FIG. 2B.

[0037] For a carrier aggregated signal comprising Bands N, M, and P, it is desirable for the Band N transmit filter to have relatively high attenuation for the Band M receive frequency band and the Band P receive frequency band. Similarly, for a carrier aggregated signal comprising Bands N, M, and P, it is desirable for the Band N receive filter to have relatively high attenuation for the Band M transmit frequency band and the Band P transmit frequency band.

[0038] 1A and 2B, filters can include the surface acoustic wave devices disclosed herein. Additionally, the surface acoustic wave devices disclosed herein can be implemented in filters having any other suitable frequency response.

[0039] FIG. 3A is a cross-sectional view of a surface acoustic wave device 10 according to one embodiment. The surface acoustic wave device 10 includes a quartz crystal substrate 12, a lithium tantalate (LiTaO) layer 14 having a thickness H1, and interdigital transducer (IDT) electrodes 16 having a thickness h and a pitch L. The surface acoustic wave device 10 can be implemented in a filter array configured to filter a carrier-aggregated signal. Such a filter can pass a first band of the carrier-aggregated signal and suppress higher-order spurious modes corresponding to a second band of the carrier-aggregated signal. The surface acoustic wave device 10 can be configured to operate in a shear-horizontal (SH) mode.

[0040] The quartz crystal substrate 12 may have a cut angle ranging from 20° to 52°. As used herein, an N° "cut angle" refers to an N° rotated Y-cut in a Y-cut, X-propagating piezoelectric layer. Thus, for a piezoelectric layer with Euler angles (φ, θ, ψ), the "cut angle" in degrees may be θ minus 90°. The surface acoustic wave device generates a surface acoustic wave having a wavelength λ, and the thickness H1 of the lithium tantalate layer 14 may range from 0.15λ to 1.4λ. In some examples, the thickness H1 of the lithium tantalate layer 14 may range from 0.2λ to 1.2λ. The lithium tantalate layer 14 may have a cut angle ranging from 10° to 50°. As shown in FIG. 8C, this cut angle range is consistent with the desired k 2 In some applications, the lithium tantalate layer 14 may have a cut angle ranging from 40° to 50°. The lithium tantalate layer 14 may be bonded to a quartz substrate 12.

[0041] 3B-3E are graphs associated with a quartz crystal cut angle sweep for various lithium tantalate layer thicknesses H1 of the surface acoustic wave device 10. These graphs correspond to a surface acoustic wave device 10 in which the lithium tantalate layer 14 has a thickness H1 of 42° YX, and the quartz crystal substrate 12 has Euler angles (0, θ, 0). The thickness H1 of the lithium tantalate layer 14 is expressed in units of λ, where λ is the wavelength of the surface acoustic wave generated by the surface acoustic wave device 10. λ can be represented by "L". These graphs indicate that quartz crystals with cut angles ranging from 20° to 52° are desirable, corresponding to θ ranging from 110° to 142°. FIG. 3B shows that the quality factor (Qp) at antiresonance peaks near θ = 130° for various lithium tantalate layer 14 thicknesses. 3C shows that the quality factor (Qs) at resonance has a peak near θ = 130° for various thicknesses of the lithium tantalate layer 14. FIG. 2 3E shows that the TCF vs. θ is maximized when the thickness H1 of the lithium tantalate layer 14 is around 0.3λ to 0.5λ.

[0042] 3F-3I are graphs associated with a quartz crystal cut angle sweep for various lithium tantalate layer thicknesses H1 of the surface acoustic wave device 10. These graphs correspond to different quartz crystal propagation angles than those of FIGS. 3B-3E. FIGS. 3F-3I correspond to a surface acoustic wave device 10 in which the lithium tantalate layer 14 has a thickness H1, an LT of 42° YX, and the quartz crystal substrate 12 has Euler angles (0, θ, 90°). FIG. 3F shows that the thinner the lithium tantalate layer 14, the more stable Qp becomes. FIG. 3G shows that the thinner the lithium tantalate layer 14, the larger Qs becomes. FIG. 3H shows that the electromechanical coupling coefficient k when the lithium tantalate layer 14 has a thickness H1 near 0.3λ. 2 FIG. 3H also shows that the electromechanical coupling coefficient k 23I also shows that when the propagation angle of the quartz substrate 12 is 90°, the TCF can be improved compared to when the propagation angle of the quartz substrate 12 is 0°.

[0043] 3J-3K are graphs associated with lithium tantalate cut angle sweeps for surface acoustic wave device 10. These graphs correspond to a surface acoustic wave device 10 in which the lithium tantalate layer 14 has Euler angles of (0,θ,0) and thickness H1=0.3λ, the quartz substrate 12 has Euler angles of (0,132,90), and the IDT electrode 16 has aluminum thickness of 0.08λ. FIG. 3J is a graph of quality factor versus lithium tantalate cut angle for the surface acoustic wave device 10 of FIG. 3A. FIG. 3K is a graph of k for the surface acoustic wave device of FIG. 3A. 2 3K is a graph of the lithium tantalate cut angle versus k. 2 may have a peak at approximately θ=120°. Figure 3K shows that the cut angle of the lithium tantalate layer 14 is preferably in the range of about 90° to 150°.

[0044] 3A, the IDT electrode 16 may be an aluminum IDT electrode. The IDT electrode material may include titanium (Ti), gold (Au), silver (Ag), copper (Cu), platinum (Pt), tungsten (W), molybdenum (Mo), ruthenium (Ru), or any suitable combination thereof. For example, the IDT electrode 16 may include aluminum and molybdenum in certain applications.

[0045] 4 is a cross-sectional view of a surface acoustic wave device 17. The surface acoustic wave device 17 includes a silicon substrate 18, a lithium tantalate layer 14 having a thickness H1, and an IDT electrode 16 having a thickness H and a pitch L.

[0046] 5 is a cross-sectional view of a surface acoustic wave device 19. The surface acoustic wave device 19 includes a lithium tantalate layer 14 and IDT electrodes 16 having a thickness H and a pitch L. The lithium tantalate layer 14 can be thick enough that back-reflection effects are negligible. For example, in certain applications, the thickness of the lithium tantalate layer 14 is greater than 20λ.

[0047] 6A-6C are graphs comparing the characteristics of the surface acoustic wave devices of FIGS. 3A, 4, and 5. These graphs correspond to surface acoustic wave device 10, in which the quartz crystal substrate 12 is 42°YX quartz, the lithium tantalate layer 14 is 42°YX LT with a thickness H1 of λ (λ=2 micrometers (um)), and the IDT electrodes 16 are aluminum and have a thickness H of 0.08λ and a pitch L of λ. These graphs also correspond to surface acoustic wave device 17, in which the lithium tantalate layer 14 is 42°YX LT with a thickness H1 of λ (λ=2 um), and the IDT electrodes 16 are aluminum and have a thickness H of 0.08λ and a pitch L of λ. These graphs also correspond to surface acoustic wave device 19, in which the lithium tantalate layer 14 is 42°YX LT with a thickness H of 0.08λ (λ=2 um), and the IDT electrodes 16 are aluminum and have a thickness H of 0.08λ (λ=2 um) and a pitch L of λ.

[0048] Figure 6A is a graph of the frequency response for the surface acoustic wave devices of Figures 3A, 4, and 5. Figure 6A shows that surface acoustic wave device 17 has a relatively strong response to higher-order spurious modes. Figure 6A also shows that surface acoustic wave device 10 has a relatively low response to higher-order spurious modes.

[0049] FIG. 6B shows the k 2 6B is a graph of the electromechanical coupling coefficient k for the surface acoustic wave device 19. 2 is about 9.6%, and k 2 is about 10.0%, and k for the surface acoustic wave device 17 2This indicates that the probability of

[0050] Figure 6C is a graph of quality factor versus frequency for the surface acoustic wave devices of Figures 3A, 4, and 5. Figure 6C shows that Qs is about 560 for surface acoustic wave device 19, Qs is about 470 for surface acoustic wave device 10, and Qs is about 560 for surface acoustic wave device 17. Figure 6C also shows that Qp is about 938 for surface acoustic wave device 19, Qp is about 1900 for surface acoustic wave device 10, and Qp is about 2100 for surface acoustic wave device 17.

[0051] Figure 7A is a graph of transmission characteristics corresponding to the graphs of Figures 6A-6C for the surface acoustic wave devices of Figures 3A, 4, and 5. Figure 7A shows that the surface acoustic wave device 17 has a relatively strong response to higher-order spurious modes, and that the surface acoustic wave device 10 has a relatively low higher-order spurious response.

[0052] FIG. 7B is a graph of the reflection characteristics corresponding to the graphs of FIGS. 6A to 6C for the surface acoustic wave devices of FIGS.

[0053] 8A, 8B, and 8C are graphs of the lithium tantalate cut angle swept for the surface acoustic wave devices of FIGS. 3A, 4, and 5. These graphs correspond to the surface acoustic wave devices corresponding to the graphs of FIGS. 6A-6C, except that the lithium tantalate cut angle is varied. FIGS. 8A and 8B show that a given lithium tantalate cut angle can result in high Qs and Qp values. FIG. 8B illustrates that available lithium tantalate cut angles can be limited by bulk radiation. FIG. 8C shows that a lower cut angle can result in a higher electromechanical coupling coefficient.

[0054] 9A, 9B, and 9C are graphs of crystal cut sweeps for the surface acoustic wave device 10 of FIG. 3A. These graphs correspond to the surface acoustic wave device 10 corresponding to the graphs of FIGS. 6A-6C, except that the crystal cut angle is varied. FIGS. 8A and 8B show that a given crystal cut angle can result in high Qs and Qp values. These graphs show that a crystal cut angle in the range of 20° to 52° is desirable.

[0055] 10A-10E are graphs associated with lithium tantalate thickness sweeps for the surface acoustic wave device 10 of FIG. 3A. These graphs correspond to the surface acoustic wave device 10 corresponding to the graphs of FIGS. 6A-6C, except that the lithium tantalate thickness H1 is varied. FIG. 10A shows the change in ΔZ in the frequency response. SH and ΔZ SP FIG. 10B illustrates the impedance ratio ΔZ SH and ΔZ SP FIG. 10B shows that a lithium tantalate thickness H1 of less than 1.4λ is desirable. FIG. 10C is a graph of Qs versus lithium tantalate layer thickness for the surface acoustic wave devices of FIGS. 3A, 4, and 5. FIG. 10D is a graph of Qs versus lithium tantalate layer thickness for the surface acoustic wave devices of FIGS. 3A, 4, and 5. FIG. 10E is a graph of Qs versus lithium tantalate layer thickness for the surface acoustic wave devices of FIGS. 3A, 4, and 5. 2 10E shows that a lithium tantalate thickness H1 of at least 0.15λ is desirable. Thus, these graphs show that a lithium tantalate thickness H1 in the range of 0.15λ to 1.4λ is desirable. When the lithium tantalate thickness H1 is greater than 1.4λ, ΔZ SH and ΔZ SP 5 having a constant thickness for the lithium tantalate layer 14 is used in Figures 10C-10E because the lithium tantalate layer 14 for the surface acoustic wave device 19 is thick enough that the bottom reflection effect is negligible.

[0056] The thickness of the quartz substrate 12 of the surface acoustic wave device 10 of FIG. 3A may be, for example, less than 695 micrometers (um). The upper thickness limit of the quartz substrate 12 may comply with wafer bending specifications, such as the SEMI standard for 6-inch quartz wafers. The thickness of the quartz substrate 12 may be at least λ. Thus, the thickness of the quartz substrate 12 may range from λ to 695 um, where λ is the wavelength of the surface acoustic wave generated by the surface acoustic wave device 10.

[0057] FIGS. 11A-11C are graphs associated with lithium tantalate propagation angle sweeps for the surface acoustic wave devices of FIGS. 3A, 4, and 5. These graphs correspond to the surface acoustic wave devices corresponding to the graphs of FIGS. 6A-6C, except that the propagation angles are changed. The lithium tantalate layers of FIGS. 3A, 4, and 5 can have Euler angles φ, θ, and ψ. The second Euler angle θ is the cut angle plus 90°. The third Euler angle ψ is the propagation angle. FIG. 11A is a graph of Qs versus propagation angle. FIG. 11B is a graph of Qp versus propagation angle. FIGS. 11A and 11B show that the Qs and Qp of the surface acoustic wave device 10 of FIG. 3A do not decrease significantly as ψ is rotated (e.g., increased). Thus, the lithium tantalate layer 14 of the surface acoustic wave device 10 of FIG. 3A can have a propagation angle ψ ranging from -10° to 10°. FIG. 11C shows the k 2 1 is a graph of propagation angle versus.

[0058] The quartz crystal layer 12 of the surface acoustic wave device 10 of FIG. 3A may have Euler angles φ, θ, and ψ. The second Euler angle θ is the cut angle plus 90°. The third Euler angle ψ is the propagation angle. The Qs, Qp, and k of the surface acoustic wave device 10 with quartz crystal substrates having cut angles of 40° (i.e., θ=130°) and 44° (i.e., θ=134°) are shown below. 2 It is shown that the ψ of the quartz substrate 12 is preferably in the range of -10° to 10°. 2Analysis of the above indicates that φ of the quartz substrate 12 is preferably in the range of −10° to 10° in the given example.

[0059] FIG. 12 is a graph of acoustic velocity versus lithium tantalate layer thickness for the surface acoustic wave devices of FIGS. 3A, 4, and 5. The acoustic velocity ranges from 3800 meters / second to 4200 meters / second. The acoustic velocity corresponds to a shear wave (SH) mode. Therefore, the surface acoustic wave devices described herein can operate in the SH mode.

[0060] FIG. 13 is a cross-sectional view of a surface acoustic wave device 20 according to one embodiment. The surface acoustic wave device 20 is similar to the surface acoustic wave device 10 of FIG. 3A except that the surface acoustic wave device 20 includes a silicon dioxide layer 22 covering the IDT electrode 16. The silicon dioxide layer 22 has a thickness H2. The silicon dioxide layer 22 can reduce the TCF of the surface acoustic wave device 20 to near zero compared to the surface acoustic wave device 10 of FIG. 3A. The surface acoustic wave device 20 may be referred to as a temperature-compensated surface acoustic wave device. In some examples, a different temperature-compensating layer can be implemented instead of the silicon dioxide layer 22. Such a temperature-compensating layer can have a positive temperature coefficient of frequency, thereby compensating for the TCF of the lithium tantalate layer 14. Alternative temperature-compensating layers can include, for example, tellurium dioxide (TeO2) and / or silicon oxyfluoride (SiOF).

[0061] 14A-14D are graphs of parameters of the surface acoustic wave device 20 of FIG. 13. These graphs correspond to a surface acoustic wave device 20 in which the quartz crystal substrate 12 is 42°YX quartz, the lithium tantalate layer 14 is 42°YX LT with a thickness H1 of λ (λ=2 μm), the IDT electrodes 16 are aluminum with a thickness H of 0.08λ and a pitch L of λ, and the silicon dioxide layer 22 has a thickness H2. These graphs include curves of the parameters of the surface acoustic wave device 20 versus the thickness H2 of the silicon dioxide layer 22.

[0062] Figure 14A is a graph of silicon dioxide thickness versus TCF for the surface acoustic wave device 20 of Figure 13 and a similar surface acoustic wave device without the quartz substrate present. Figure 14A shows that the temperature coefficient of frequency (TCF) can be improved (i.e., can be close to zero) as the thickness H2 of the silicon dioxide layer 22 is increased.

[0063] FIG. 14B is a graph of silicon dioxide thickness versus Qs for the surface acoustic wave device 20 of FIG. 13, a similar surface acoustic wave device without a quartz substrate, and a similar surface acoustic wave device with a silicon substrate instead of a quartz substrate.

[0064] FIG. 14C is a graph of silicon dioxide thickness versus Qp for the surface acoustic wave device 20 of FIG. 13, a similar surface acoustic wave device without a quartz substrate, and a similar surface acoustic wave device with a silicon substrate instead of a quartz substrate.

[0065] FIG. 14D shows a graph of silicon dioxide thickness versus k for the surface acoustic wave device 20 of FIG. 13, a similar surface acoustic wave device without a quartz substrate, and a similar surface acoustic wave device with a silicon substrate instead of a quartz substrate. 2 This is a graph of

[0066] FIG. 15 is a cross-sectional view of a surface acoustic wave device 25 according to one embodiment. The surface acoustic wave device 25 is similar to the surface acoustic wave device 10 of FIG. 3A, except that the surface acoustic wave device 25 includes an additional layer 26 disposed between the quartz crystal substrate 12 and the lithium tantalate layer 14. The additional layer 26 may be a relatively high impedance material to enhance reflection at the LT / quartz crystal interface and improve the quality factor. The additional layer 26 may reinforce the adhesion between the quartz crystal substrate 12 and the lithium tantalate layer 14. The additional layer 26 may be, for example, an aluminum nitride (AlN) layer, a silicon nitride (SiN) layer, an aluminum oxide (AlO) layer, a silicon carbide (SiC) layer, a silicon oxynitride layer, a sapphire layer, a diamond layer, or the like.

[0067] Although certain embodiments described herein relate to surface acoustic wave devices including lithium tantalate layers, any suitable principles and advantages described herein may also be applied to surface acoustic wave devices including any other suitable lithium-based piezoelectric layers instead of lithium tantalate layers, including lithium niobate (LiNbO) and lithium tantalate.

[0068] 16A is a cross-sectional view of a surface acoustic wave device 30 according to one embodiment. The surface acoustic wave device 30 is similar to the surface acoustic wave device 10 of FIG. 3A, except that the surface acoustic wave device 30 includes a lithium niobate layer 32 instead of the lithium tantalate layer 14.

[0069] FIG. 16B shows the electromechanical coupling coefficient k between the surface acoustic wave device 10 of FIG. 3A and the surface acoustic wave device 30 of FIG. 16A. 2 16B is a graph comparing the cut angle of the lithium-based piezoelectric layer. The graph corresponds to surface acoustic wave devices 10 and 30 having h=0.08λ and H1=0.3λ. One curve in this graph corresponds to the surface acoustic wave device 10 of FIG. 3A, which has a lithium tantalate layer 14 with Euler angles (0, θ, 0) and a quartz crystal substrate 12 with Euler angles (0, 132, 90). The other curve in this graph corresponds to the surface acoustic wave device 30 of FIG. 16A, which has a lithium niobate layer 32 with Euler angles (0, θ, 0) and a quartz crystal substrate 12 with Euler angles (0, 132, 90). As shown in FIG. 16B, the surface acoustic wave device 30 of FIG. 16A has a better k-axis than the surface acoustic wave device 10 of FIG. 3A. 2 16B shows that a θ in the range of approximately 70° to 155° is preferred for certain embodiments of the surface acoustic wave device 30.

[0070] Although certain embodiments described herein relate to surface acoustic wave devices that include a quartz substrate, any applicable principles and advantages described herein may also be applied to surface acoustic wave devices that include any other suitable substrate instead of a quartz substrate, which may also be arranged to trap acoustic waves within the lithium-based piezoelectric layer while allowing one or more higher-order spurious mode responses to leak into the other substrate.

[0071] The surface acoustic wave device can be included in a filter. A filter including one or more surface acoustic wave devices can be referred to as a surface acoustic wave filter. A plurality of surface acoustic wave devices are arranged as series resonators and shunt resonators to form a ladder-type filter. In some examples, a filter can include a plurality of surface acoustic wave resonators and one or more other resonators (e.g., one or more bulk acoustic wave resonators, one or more Lamb wave resonators, one or more boundary acoustic wave resonators, etc., or any suitable combination thereof).

[0072] As described above, the surface acoustic wave device disclosed herein can be implemented in a filter configured to pass a first band of a carrier aggregation signal and suppress higher-order spurious modes corresponding to a second band of the carrier aggregation signal. A carrier aggregation system can process a carrier aggregation signal including two or more carriers. For example, the carrier aggregation system can process a carrier aggregation signal received by an antenna. As another example, the carrier aggregation system can generate a carrier aggregation signal to be transmitted by an antenna. Examples of carrier aggregation systems that can include such filters are described with reference to FIGS. 17A-17D.

[0073] FIG. 17A is a schematic diagram of a carrier aggregation system 40. The exemplary carrier aggregation system 40 includes power amplifiers 42A and 42B, switches 43A and 43B, duplexers 44A and 44B, switches 45A and 45B, a diplexer 46, and an antenna 47. The power amplifiers 42A and 42B may each transmit an amplified RF signal associated with a different carrier. The switch 43A may be a band select switch. The switch 43A may couple the output of the power amplifier 42A to a selected duplexer of the duplexer 44A. Each duplexer may include a transmit filter and a receive filter. Any of the filters of the duplexers 44A and 44B may be implemented according to any suitable principles and advantages described herein. The switch 45A may couple a selected duplexer of the duplexer 44A to the diplexer 46. The diplexer 46 can combine the RF signals provided by the switches 45A and 45B into a carrier aggregation signal that is transmitted by the antenna 47. The diplexer 46 can separate different frequency bands of the carrier aggregation signal received by the antenna 47. The diplexer 46 is an example of a frequency domain multiplexer. Other frequency domain multiplexers include triplexers. A carrier aggregation system including a triplexer can process a carrier aggregation signal associated with three carriers. The switches 45A and 45B and the selectable receive filters of the duplexers 44A and 44B can provide the frequency band separated RF signals to the respective receive paths.

[0074] FIG. 17B is a schematic diagram of a carrier aggregation system 50. The exemplary carrier aggregation system 50 includes power amplifiers 42A and 42B, low-noise amplifiers 52A and 52B, switches 53A and 53B, filters 54A and 54B, a diplexer 46, and an antenna 47. The power amplifiers 42A and 42B can each transmit an amplified RF signal associated with a different carrier. The switch 53A can be a transmit / receive switch. The switch 53A can couple the filter 54A to the output of the power amplifier 42A in a transmit mode and to the input of the low-noise amplifier 52A in a receive mode. The filter 54A and / or the filter 54B can be implemented according to any suitable principles and advantages described herein. The diplexer 46 can combine the RF signals from the power amplifiers 42A and 42B provided by the switches 53A and 53B into a carrier-aggregated signal transmitted by the antenna 47. The diplexer 46 can separate different frequency bands of the carrier aggregation signal received by the antenna 47. The switches 53A and 53B and the filters 54A and 54B can provide the RF signals with the separated frequency bands to the low noise amplifiers 52A and 52B, respectively.

[0075] 17C is a schematic diagram of a carrier aggregation system 60 including a multiplexer in a signal path between a power amplifier and an antenna. The exemplary carrier aggregation system 60 includes a low-band path, a mid-band path, and a high-band path. In a given application, the low-band path may process radio frequency signals with frequencies below 1 GHz, the mid-band path may process radio frequency signals with frequencies between 1 GHz and 2.2 GHz, and the high-band path may process radio frequency signals with frequencies above 2.2 GHz.

[0076] A diplexer 46 may be included between the RF signal path and the antenna 47. The diplexer 46 may frequency multiplex radio frequency signals that are relatively far apart in frequency. The diplexer 46 may be implemented with relatively low-loss passive circuit elements. The diplexer 46 may combine (for transmission) and separate (for reception) carriers of a carrier aggregation signal.

[0077] As illustrated, the low-band path includes a power amplifier 42A configured to amplify a low-band radio frequency signal, a band select switch 43A, and a multiplexer 64A. The band select switch 43A can electrically connect the output of the power amplifier 42A to a selected transmit filter of the multiplexer 64A. The selected transmit filter may be a band-pass filter whose passband corresponds to the frequency of the output signal of the power amplifier 42A. The multiplexer 64A may include any suitable number of transmit filters and any suitable number of receive filters. One or more of the transmit filters and / or one or more of the receive filters may be implemented according to any suitable principles and advantages described herein. The multiplexer 64A may have the same number of transmit filters as receive filters. In some examples, the multiplexer 64A may have a different number of transmit filters than receive filters.

[0078] As illustrated in FIG. 17C , the intermediate-band path includes a power amplifier 42B configured to amplify the intermediate-band radio frequency signal, a band select switch 43B, and a multiplexer 64B. The band select switch 43B can electrically connect the output of the power amplifier 42B to a selected transmit filter of the multiplexer 64B. The selected transmit filter may be a band-pass filter whose passband corresponds to the frequency of the output signal of the power amplifier 42B. The multiplexer 64B may include any suitable number of transmit filters and any suitable number of receive filters. One or more of the transmit filters and / or one or more of the receive filters may be implemented according to any suitable principles and advantages described herein. The multiplexer 64B may have the same number of transmit filters as the receive filters. In some examples, the multiplexer 64B may have a different number of transmit filters than the receive filters.

[0079] In the exemplary carrier aggregation system 60, the high-band path includes a power amplifier 42C configured to amplify a high-band radio frequency signal, a band select switch 43C, and a multiplexer 64C. The band select switch 43C can electrically connect the output of the power amplifier 42C to a selected transmit filter of the multiplexer 64C. The selected transmit filter may be a band-pass filter whose passband corresponds to the frequency of the output signal of the power amplifier 42C. The multiplexer 64C may include any suitable number of transmit filters and any suitable number of receive filters. One or more of the transmit filters and / or one or more of the receive filters may be implemented according to any suitable principles and advantages described herein. The multiplexer 64C may have the same number of transmit filters as the receive filters. In some examples, the multiplexer 64C may have a different number of transmit filters than the receive filters.

[0080] The selection switch 65 can selectively provide the radio frequency signal from the mid-band path or the high-band path to the diplexer 46. Thus, the carrier aggregation system 60 can process carrier aggregation signals with either a combination of low-band and high-band or a combination of low-band and mid-band.

[0081] Figure 17D is a schematic diagram of a carrier aggregation system 70 including a multiplexer in the signal path between the power amplifier and the antenna. Carrier aggregation system 70 is similar to carrier aggregation system 60 of Figure 17C, except that carrier aggregation system 70 includes a switchplexing feature. Switchplexing may be implemented according to any suitable principles and advantages described herein.

[0082] Switchplexing can implement on-demand multiplexing. Some radio frequency systems can operate in a single-carrier mode most of the time (e.g., about 95% of the time) and in a carrier aggregation mode a small portion of the time (e.g., about 5% of the time). Switchplexing can reduce the load in the single-carrier mode in which a radio frequency system may operate most of the time compared to multiplexers that include filters with fixed connections to a common node. Such load reduction can be significant when there are a relatively large number of filters included in the multiplexer.

[0083] In the exemplary carrier aggregation system 70, duplexers 64B and 64C are selectively coupled to diplexer 46 by switch 75. Switch 75 is configured as a multi-close switch in which two or more throws can be simultaneously active. Simultaneous activation of multiple throws of switch 75 can enable transmission and / or reception of carrier aggregation signals. Switch 75 may also enable a single throw to be active during single-carrier mode. As illustrated, each duplexer of duplexer 44A is coupled to a separate throw of switch 75. Similarly, exemplary duplexer 44B includes multiple duplexers coupled to separate throws of switch 75. Alternatively, instead of coupling a duplexer to each throw of switch 75 as illustrated in FIG. 17D, one or more individual filters of a multiplexer may be coupled to a dedicated throw of a switch coupled between the multiplexer and a common node. For example, in some applications, such a switch may have twice the number of throws of exemplary switch 75.

[0084] The filters described herein can be implemented in a variety of package modules. Several example package modules in which any suitable principles and advantages of the filters described herein can be implemented are described herein. Figures 18A and 18B are schematic block diagrams illustrating package modules according to certain embodiments.

[0085] FIG. 18A is a schematic block diagram of a module 80 including a power amplifier 42, a switch 83, and a filter 84 according to one or more embodiments. The module 80 may include a package enclosing the illustrated components. The power amplifier 42, the switch 83, and the filter 84 may be disposed on a common package substrate. The package substrate may be, for example, a laminate substrate. The switch 83 may be a multi-throw radio frequency switch. The switch 83 may electrically couple the output of the power amplifier 42 to a selected filter of the filter 84. The filter 84 may include any suitable number of surface acoustic wave filters. One or more of the filters of the filter 84 may be implemented according to any suitable principles and advantages disclosed herein.

[0086] FIG. 18B is a schematic block diagram of a module 85 including power amplifiers 42A and 42B, switches 83A and 83B, filters 84A and 84B according to one or more embodiments, and an antenna switch 88. Module 85 is similar to module 80 of FIG. 18A, except that module 85 includes an additional RF signal path, and antenna switch 88 is arranged to selectively couple signals from filter 84A or filter 84B to an antenna node. One or more of filters 84A and / or 84B may be implemented according to any suitable principles and advantages disclosed herein. The additional RF signal path includes an additional power amplifier 42B, an additional switch 83B, and an additional filter 84B. Different RF signal paths may be associated with different frequency bands and / or different operating modes (e.g., different power modes, different signaling modes, etc.).

[0087] FIG. 19 is a schematic block diagram of a wireless communication device 90 including a filter 93 according to one or more embodiments. The one or more surface acoustic wave filters of the filter 93 may be implemented according to any suitable principles and advantages disclosed herein. The wireless communication device 90 may be any suitable wireless communication device. For example, the wireless communication device 90 may be a mobile phone, such as a smartphone. Illustratively, the wireless communication device 90 includes an antenna 91, an RF front end 92, a transceiver 94, a processor 95, and a memory 96. The antenna 91 may transmit RF signals provided by the RF front end 92. Such RF signals may include carrier aggregated signals. The antenna 91 may provide received RF signals to the RF front end 92 for processing. Such RF signals may include carrier aggregated signals.

[0088] The RF front end 92 may include one or more power amplifiers, one or more low-noise amplifiers, RF switches, receive filters, transmit filters, duplex filters, multiplexers, frequency multiplexing circuits, or any suitable combination thereof. The RF front end 92 can transmit and receive RF signals associated with any suitable communications standard. Any of the surface acoustic wave devices and / or filters disclosed herein can be implemented in the filter 93 of the RF front end 92.

[0089] The transceiver 94 may provide an RF signal to the RF front end 92 for amplification and / or other processing. The transceiver 94 may also process the RF signal provided by the low noise amplifier of the RF front end 92. The transceiver 94 is in communication with a processor 95. The processor 95 may be a baseband processor. The processor 95 may provide any suitable baseband processing functionality for the wireless communication device 90. A memory 96 is accessible by the processor 95. The memory 96 may store any suitable data for the wireless communication device 90.

[0090] Any of the principles and advantages described herein may apply not only to the systems, modules, filters, multiplexers, wireless communication devices, and methods described above, but also to other suitable systems (e.g., carrier aggregation systems), modules, chips, surface acoustic wave devices, filters, duplexers, multiplexers, wireless communication devices, and methods. Elements and operations of the various embodiments described above may be combined to provide additional embodiments. Any of the principles and advantages described herein may be implemented in radio frequency circuits configured to process signals having frequencies in the range of approximately 30 kHz to 300 GHz, e.g., approximately 450 MHz to 8.5 GHz. For example, any of the filters described herein may filter signals having frequencies in the range of approximately 30 kHz to 300 GHz, e.g., approximately 450 MHz to 8.5 GHz.

[0091] Aspects of the present disclosure can be implemented in various electronic devices. Examples of electronic devices include, but are not limited to, consumer electronic products, components of consumer electronic products such as chip and / or package radio frequency modules, electronic test equipment, uplink wireless communication devices, personal area network communication devices, etc. Examples of consumer electronic products may include, but are not limited to, mobile phones such as smartphones, wearable computing devices such as smart watches or earpieces, telephones, televisions, computer monitors, computers, routers, modems, handheld computers, laptop computers, tablet computers, personal digital assistants (PDAs), vehicle electronic systems such as automobile electronic systems, microwave ovens, refrigerators, stereo systems, digital music players, cameras such as digital cameras, portable memory chips, home appliances, etc. Additionally, electronic devices may include unfinished products.

[0092] Furthermore, conditional language used herein, such as, inter alia, "can," "could," "may," "might," "for example," "such as," and the like, is generally intended to convey that certain embodiments include certain features, elements, and / or conditions, while other embodiments do not, unless specifically stated otherwise or understood otherwise from the context of use. The term "coupled," as generally used herein, refers to two or more elements that may be either directly coupled to each other or coupled via one or more intermediate elements. Similarly, the term "connected," as generally used herein, refers to two or more elements that may be either directly connected to each other or connected via one or more intermediate elements. Additionally, the terms "here," "above," "below," and words of similar import, when used in this application, refer to this application as a whole, and not to any specific portion of this application.

[0093] While certain embodiments have been described, these embodiments are presented by way of example only and are not intended to limit the scope of the present disclosure. Indeed, the novel devices, chips, methods, apparatus, and systems described herein may be embodied in a variety of other forms. Furthermore, various omissions and changes in the form of the methods, apparatus, and systems described herein may be made without departing from the spirit of the present disclosure. For example, circuit blocks described herein may be deleted, moved, added, subdivided, combined, and / or modified. Each of these circuit blocks may be implemented in a variety of different ways. The appended claims and their equivalents are intended to cover any such forms or modifications that fall within the scope and spirit of the present disclosure.

Claims

1. A filter for a carrier aggregation system, comprising: including a surface acoustic wave device, the surface acoustic wave device includes a quartz crystal substrate, an interdigital transducer electrode, and a lithium-based piezoelectric layer positioned between the quartz crystal substrate and the interdigital transducer electrode; the surface acoustic wave device is configured to suppress a higher-order spurious mode corresponding to a second band of the carrier aggregation signal; The filter is configured to pass a first band of carrier aggregation signals.

2. 2. The filter of claim 1, wherein the quartz substrate has a cut angle in the range of 20 degrees to 52 degrees.

3. 2. The filter of claim 1, wherein said lithium-based piezoelectric layer is a lithium tantalate layer.

4. the surface acoustic wave device is configured to generate a surface acoustic wave having a wavelength λ; 4. The filter of claim 3, wherein the thickness of said lithium tantalate layer is in the range of 0.15.lambda. to 1.4.lambda..

5. the filter is a transmit filter; the first band is a transmission band; 2. The filter of claim 1, wherein said second band is a receive band.

6. the filter is a receive filter; the first band is a receive band; 2. The filter of claim 1, wherein said second band is a transmit band.

7. The filter of claim 1 , wherein the filter is configured to suppress other higher order spurious modes corresponding to a third band of the carrier aggregation signal.

8. 2. The filter of claim 1, wherein said lithium-based piezoelectric layer is a lithium tantalate layer having a cut angle in the range of 10 degrees to 50 degrees.

9. 10. The filter of claim 1, wherein the surface acoustic wave device is configured to operate in a shear wave mode.

10. 2. The filter of claim 1, wherein said surface acoustic wave device has a sound velocity in the range of 3,800 meters / second to 4,200 meters / second.

11. 2. The filter of claim 1, wherein the lithium-based piezoelectric layer is bonded to the quartz substrate.

12. the surface acoustic wave device further includes an additional layer disposed between the lithium-based piezoelectric layer and the quartz substrate; The filter of claim 1 , wherein the additional layer is configured to increase the quality factor of the surface acoustic wave device.

13. 1. A filter assembly for a carrier aggregation system, comprising: a first filter including a surface acoustic wave device, the surface acoustic wave device including a quartz crystal substrate, an interdigital transducer electrode, and a lithium-based piezoelectric layer positioned between the quartz crystal substrate and the interdigital transducer electrode, the surface acoustic wave device configured to suppress higher order spurious modes corresponding to a second band of the carrier aggregation signal, the first filter configured to pass the first band of the carrier aggregation signal; a second filter configured to pass a second band of carrier aggregation signals; and A filter assembly including:

14. the first filter is a transmit filter; 14. The filter assembly of claim 13, wherein the second filter is a receive filter.

15. the first filter is a receive filter; 14. The filter assembly of claim 13, wherein the second filter is a transmit filter.

16. 14. The filter assembly of claim 13, wherein the filter assembly includes a multiplexer including a first filter and a second filter.

17. A carrier aggregation system, a frequency multiplexing circuit having a terminal to which a carrier aggregation signal is applied; a multiplexer in communication with the frequency multiplexing circuit; Including, the multiplexer includes a filter coupled to a common node; the filter includes a first filter configured to pass a first band of carrier aggregation signals; the first filter includes a surface acoustic wave device; the surface acoustic wave device includes a quartz crystal substrate, an interdigital transducer electrode, and a lithium-based piezoelectric layer positioned between the quartz crystal substrate and the interdigital transducer electrode; The surface acoustic wave device is configured to suppress higher-order spurious modes corresponding to a second band of a carrier aggregation signal.

18. 18. The carrier aggregation system of claim 17, wherein the frequency multiplexing circuit is a diplexer.

19. 18. The carrier aggregation system of claim 17, wherein the multiplexer is a duplexer.

20. a power amplifier; a switch coupled between the power amplifier and the first filter; 20. The carrier aggregation system of claim 17, further comprising:

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