Multiplexer, wireless communication device, and switchable filter with switchable elastic wave filter

Abstract

To provide a switchable acoustic wave filter, a multiplexer, a radio frequency system, a wireless communication device, and a method.SOLUTION: A multiplexer 20 with a band pass filter 22 and a switchable band stop filter 24 includes a switch 28 that electrically connects a first series acoustic wave resonator R9A to a node N1 in a first state and electrically isolates the first series acoustic wave resonator from the node N1 in a second state. In the first state, the switchable band stop filter filters radio frequency signals using at least an acoustic wave resonator R8 and the first series acoustic wave resonator R9A. In the second state, a switchable acoustic wave filter filters radio frequency signals using at least a second series acoustic wave resonator R9B.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] Cross - reference to Related Applications All applications in which foreign or domestic priority claims are identified in the application data sheet filed together with this application are hereby incorporated by reference pursuant to 37 C.F.R.§1.57. This application claims the benefit of priority of U.S. Provisional Application No. 63 / 194,760, entitled "Switchable Elastic Wave Filter and Related Multiplexer", filed on May 28, 2021; U.S. Provisional Application No. 63 / 208,600, entitled "Switchable Elastic Wave Filter", filed on Jun. 9, 2021; and U.S. Provisional Application No. 63 / 208,620, entitled "Multiplexer Comprising a Switchable Elastic Wave Filter", filed on Jun. 9, 2021, and the disclosures of each of these are hereby incorporated by reference in their entirety for all purposes.

[0002] Embodiments of the present disclosure relate to filters including elastic wave resonators.

Background Art

[0003] Elastic wave filters can include a plurality of elastic wave resonators arranged to filter radio frequency signals. Exemplary elastic wave filters include surface acoustic wave (SAW) filters and bulk acoustic wave (BAW) filters. BAW filters include BAW resonators. Exemplary BAW resonators include thin - film bulk acoustic wave resonators (FBARs) and solidly - mounted resonators (SMRs). SAW filters include SAW resonators. Exemplary SAW resonators include temperature - compensated SAW resonators, non - temperature - compensated SAW resonators, and multilayer piezoelectric substrate (MPS) SAW resonators.

[0004] Elastic 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 elastic wave filters. Elastic wave filters can be either band-pass filters or band-stop filters. Multiple elastic wave filters can be arranged as a multiplexer. For example, two elastic wave filters can be arranged as a duplexer. There are technical challenges associated with filtering signals of relatively close frequencies using different filters in a multiplexer. In addition, there are various engineering trade-offs associated with filters that filter signals under different conditions. [Overview of the Initiative]

[0005] Each innovation described in the claims has several aspects, and no single one is solely responsible for its desirable attributes. Without limiting the scope of the claims, some notable features of this disclosure are briefly described below.

[0006] One aspect of the present disclosure is a switchable elastic wave filter, which includes a first elastic wave resonator, a second elastic wave resonator, and a switch configured to electrically connect the first elastic wave resonator to a node of the switchable elastic wave filter in a first state and to electrically isolate the first elastic wave resonator from the node of the switchable elastic wave filter in a second state. The switchable elastic wave filter is configured to receive a radio frequency signal and to filter the radio frequency signal by at least the first and second elastic wave resonators in a first state and by at least the second elastic wave resonator in a second state.

[0007] A switchable elastic wave filter may have a different bandwidth in the first state than in the second state. In the second state, the switch can electrically connect the electrodes of the first elastic wave resonator to the termination impedance.

[0008] A switchable elastic wave filter may include a third elastic wave resonator. The switch can electrically isolate the third elastic wave resonator from the node in a first state and electrically connect the third elastic wave resonator to the node in a second state. The first and third elastic wave resonators may have different resonant frequencies.

[0009] The first elastic wave resonator may be a series resonator. Alternatively, the first elastic wave resonator may be a shunt resonator. The first elastic wave resonator may be a bulk elastic wave resonator in a given application.

[0010] A switchable elastic wave filter may function as a bandpass filter. A switchable elastic wave filter may function as a bandstop filter. A switchable elastic wave filter may be configured to filter wireless local area network signals. A switchable elastic wave filter may be configured to filter cellular signals. A switchable elastic wave filter may have single-switch loss.

[0011] The switchable elastic wave filter may include a second switch and a fourth elastic wave resonator. The second switch can electrically connect the fourth elastic wave resonator to the second node of the switchable elastic wave filter and electrically isolate the fourth elastic wave resonator from the second node of the switchable elastic wave filter in different states.

[0012] Another aspect of this disclosure is a multiplexer comprising a switchable elastic wave filter and a second filter coupled to the switchable elastic wave filter at a common node. The switchable elastic wave filter comprises a first elastic wave resonator, a second elastic wave resonator, and a switch. The switch is configured to electrically connect the first elastic wave resonator to a node of the switchable elastic wave filter in a first state and to electrically disconnect the first elastic wave resonator from the node of the switchable elastic wave filter in a second state. The switchable elastic wave filter is configured to receive a radio frequency signal and filter the radio frequency signal by at least the first and second elastic wave resonators in a first state and by at least the second elastic wave resonator in a second state.

[0013] The second filter may be a second switchable elastic wave filter configured to selectively and electrically couple an elastic wave resonator to the node of the second filter. The multiplexer may include a third filter coupled to the common node.

[0014] A switchable elastic wave filter may have a single switch loss. The second state may be associated with coexistence.

[0015] Another aspect of this disclosure is a method for radio frequency filtering. The method includes filtering a radio frequency signal by at least a first and a second elastic wave resonator of a switchable elastic wave filter in a first state, toggling the state of the switchable elastic wave filter from the first state to the second state, and filtering the radio frequency signal by at least the second elastic wave resonator of the switchable elastic wave filter but not by the first elastic wave resonator in the second state.

[0016] Toggle can change the bandwidth of a switchable elastic wave filter. The switchable elastic wave filter may have a single switch loss.

[0017] Another aspect of this disclosure is a multiplexer comprising a switchable acoustic wave filter. The multiplexer includes a first filter configured to receive radio frequency signals and a second filter connected to the first filter at a common node. The first filter includes one or more acoustic wave resonators, a plurality of switchable acoustic wave resonators, and a switch configurable to at least a first state and a second state. In the first state, the switch is configured to select a different subset of the plurality of switchable acoustic wave resonators than in the second state, and to use at least one or more acoustic wave resonators together to filter radio frequency signals.

[0018] The second state may be associated with coexistence. The first filter may have lower performance in terms of operating bandwidth than the second state. The first filter may be a band-pass filter having a passband. This passband covers a narrower frequency range than the second state and the first state. The first filter may be a band-stop filter having a stopband. This stopband covers a narrower frequency range than the second state and the first state.

[0019] A switchable elastic wave resonator may include a series resonator. A switchable elastic wave resonator may include a shunt resonator.

[0020] The band edge of the first filter and the band edge of the second filter may have frequencies that are closer in the first state of the switch than in the second state of the switch. The first state may be associated with the second filter being inactive, and the second state may be associated with coexistence.

[0021] The second filter may include a second switch and a second switchable elastic wave resonator. The first filter may be configured to move the band edge of the frequency response of the first filter by toggling the switch between a first and a second state. The second filter may be configured to move the band edge of the frequency response of the second filter by the second switch. The multiplexer may include an inductor-capacitor circuit coupled between both the first and second filters and the antenna node of the multiplexer. The inductor-capacitor filter can attenuate harmonics generated by the switch.

[0022] The first filter may be a band-pass filter, and the second filter may be a band-stop filter. The first filter may be a band-stop filter, and the second filter may be a band-pass filter. The first and second filters may be band-pass filters.

[0023] The first filter may have a single-switch loss. The first filter may include a second switch and a second switchable elastic wave resonator.

[0024] The first and second filters may be configured to filter radio frequency signals associated with different frequency bands. These different frequency bands may include radio local area network bands and cellular bands.

[0025] The first filter and the second filter may each have a band edge that is within 5 megahertz of the other.

[0026] Different subsets may include a first subset and a second subset, where the first subset consists of a first switchable elastic wave resonator and the second subset consists of a second switchable elastic wave resonator.

[0027] Another aspect of the present disclosure is wireless communication including an antenna switch, an antenna, and an antenna duplexer. The antenna duplexer includes a first filter and a second filter coupled to the first filter at a common node. The first filter is present in a signal path between the antenna switch and the antenna. The first filter is configured to receive a radio frequency signal. The first filter includes one or more acoustic wave resonators, a plurality of switchable acoustic wave resonators, and a switch configurable to be in at least a first state and a second state. The switch selects, in the first state, a different subset of the switchable acoustic wave resonators than in the second state and is configured to filter the radio frequency signal using at least one or more acoustic wave resonators together.

[0028] Another aspect of the present disclosure is a switchable filter including one or more acoustic wave resonators, a plurality of switchable acoustic wave resonators, and a switch configurable to be in at least a first state and a second state. The switch is configured to select a different subset of the plurality of switchable acoustic wave resonators to filter a radio frequency signal using at least one or more acoustic wave resonators together in the first state rather than the second state.

[0029] For the purpose of summarizing the present disclosure, certain aspects, advantages, and novel features of the present innovation have been described herein. It should be understood that not all of such advantages necessarily are achieved in accordance with any particular embodiment. That is, the present innovation can be embodied or implemented in a manner that achieves or optimizes one advantage or a group of one or more advantages taught herein without necessarily achieving other advantages that may be taught or suggested herein.

Brief Description of the Drawings

[0030] Embodiments of the present disclosure are described below through non-limiting examples with reference to the accompanying drawings.

[0031] [Figure 1A-1C]Figures 1A, 1B, and 1C are schematic block diagrams of multiplexers according to several embodiments. [Figure 2] This is a schematic diagram of a multiplexer equipped with a switchable band-stop filter according to one embodiment. [Figure 3] This is a schematic diagram of a multiplexer equipped with a switchable bandpass filter according to one embodiment. [Figure 4] This is a schematic diagram of a multiplexer equipped with a switchable band-block filter and a switchable band-pass filter according to one embodiment. [Figure 5A-5B] Figure 5A is a graph of the insertion loss of a switchable bandpass filter comparing the entire passband with the passband adapted to coexistence. Figure 5B is a graph of the frequency response of the stopband of a switchable bandstop filter comparing the entire stopband with the stopband adapted to coexistence. [Figure 6A-6B] Figure 6A is a graph of the frequency response of a switchable bandpass filter comparing the entire passband with the passband adapted to coexistence. Figure 6B is an enlarged graph of the frequency response of a switchable bandpass filter for the stopband, comparing the entire stopband with the stopband adapted to coexistence. [Figure 7] This is a schematic diagram of a switchable bandpass filter according to one embodiment. [Figure 8] This is a schematic diagram of a switchable bandpass filter according to another embodiment. [Figure 9] This is a schematic diagram of a switchable band-stop filter according to one embodiment. [Figure 10] This is a schematic diagram of a switchable band-stop filter according to another embodiment. [Figure 11] This is a schematic diagram showing a switch configured to selectively and electrically connect a shunt resonator to a node of an elastic wave filter according to one embodiment. [Figure 12] This is a schematic diagram showing a switch configured to selectively and electrically connect a series resonator to a node of an elastic wave filter according to one embodiment. [Figure 13] This is a schematic block diagram of a multiplexer according to one embodiment. [Figure 14A] This is a schematic diagram of a multiplexer equipped with a switchable filter according to one embodiment. [Figure 14B] This is a schematic diagram of a multiplexer equipped with a switchable filter according to one embodiment. [Figure 15] This is a schematic diagram of a multiplexer equipped with a switchable filter according to another embodiment. [Figure 16] This is a schematic diagram of a multiplexer equipped with a switchable filter according to another embodiment. [Figure 17] This is a schematic diagram of a multiplexer equipped with a switchable filter according to one embodiment. [Figure 18] This is a schematic diagram of a multiplexer equipped with a switchable filter according to another embodiment. [Figure 19] This is a schematic diagram of a multiplexer equipped with a switchable filter according to another embodiment. [Figure 20] This is a schematic diagram of a multiplexer equipped with a switchable filter according to one embodiment. [Figure 21] This is a schematic diagram of a multiplexer having a switchable filter with a termination impedance according to one embodiment. [Figure 22] This is a schematic diagram of a multiplexer having a switchable filter with a termination impedance according to another embodiment. [Figure 23] This is a schematic diagram of a radio frequency system equipped with a multiplexer according to one embodiment. [Figure 24] This is a schematic block diagram of a wireless communication device including a filter according to one embodiment. [Modes for carrying out the invention]

[0032] The following detailed description of a given embodiment presents various descriptions of a particular embodiment. However, the innovation described herein can be embodied in numerous different forms defined and covered, for example, by the claims. In this specification, the same reference numeral refers to drawings showing identical or functionally similar elements. It should be understood that the elements shown in the drawings are not necessarily to scale. It should also be understood that a given embodiment may include more elements than shown in the drawings, and / or subsets of the elements shown in the drawings. Furthermore, some embodiments may also include any suitable combination of features from two or more drawings.

[0033] An antennaplexer is a multiplexer coupled between an antenna and multiple radio frequency signal paths. In a given application, an antennaplexer can perform frequency-domain multiplexing (multiplexing) of signals with relatively close frequencies. An exemplary antennaplexer can diplex an intermediate-high-bandwidth (MHB) signal with a 2.4 gigahertz (GHz) WiFi signal. The MHB signal may be, for example, a Band 40 signal. The 2.4 GHz WiFi band has a lower band edge at 2.4 GHz, and the Band 40 signal has an upper band edge at 2.4 GHz. The performance of the exemplary antennaplexer may be significantly degraded at and / or near 2.4 GHz due to zero-frequency transitions. Antennaplexer load loss may be significant near 2.4 GHz in this example.

[0034] To avoid such performance degradation, the antenna plexer may include a design that provides good performance for one band at the expense of performance for another. For example, in the first design, the antenna plexer may include one filter with a band edge around 2.36 GHz covering MHB up to 2.36 GHz, and another filter that covers the entire 2.4 GHz WiFi band from 2.4 GHz to 2.48 GHz. The second design can cover the entire MHB range up to 2.4 GHz, sacrificing the lower band edge of 2.4 GHz WiFi. Since these two designs have different bandwidths for the MHB path, two different filters can be implemented. To support both scenarios of MHB bandwidth coverage, the switch can be switched between two separate filters as desired. A given switchable design involves two switches, namely a switch for the filter input and a switch for the filter output. Thus, in such a design, two switch losses are added to the total filter loss.

[0035] Aspects of this disclosure relate to switching one or more specific elastic wave resonators to adjust the bandwidth of a filter. Such a filter can switch a single elastic wave resonator or a single subset of multiple elastic wave resonators using the properties of the elastic wave resonators to adjust the bandwidth. Thus, such a filter can be implemented such that only one switch loss is included in the total filter loss. Such a filter may have a single switch loss. In addition, since only a single elastic wave resonator or a single subset of multiple elastic wave resonators is switched, the physical layout and implementation are significantly smaller than a solution with two complete filters. This reduction in physical area can be significant in space-constrained user device designs, such as mobile phones.

[0036] A switchable elastic wave filter may include a first elastic wave resonator, a second elastic wave resonator, and a switch configured to electrically connect the first elastic wave resonator to a node of the switchable elastic wave filter in a first state and to electrically isolate the first elastic wave resonator from the node of the switchable elastic wave filter in a second state. The switchable filter can receive a radio frequency signal and filter the radio frequency signal by at least the first and second elastic wave resonators in a first state and by at least the second elastic wave resonator in a second state. The switch can also electrically isolate a third elastic wave resonator from a node in a first state and to electrically connect the third elastic wave resonator to the node in a second state. Thus, the switch can select either the first or third elastic wave resonator to filter the radio frequency signal in different states.

[0037] The switchable filters disclosed herein can be implemented in a multiplexer such as an antenna plexer. One or more filters in a multiplexer may be switchable to adjust the bandwidth. The bandwidth can be adjusted by switching one or more elastic wave resonators.

[0038] When two filters of a multiplexer have band edges that are relatively close in frequency domains, implementing at least one of the two filters as a switchable filter can provide separation of the band edges of the two filters for coexistence, while maintaining the full bandwidth for at least one of the two filters when coexistence is not required. This may sacrifice performance for the purpose of coexistence, but otherwise high filtering performance can be achieved. For the switchable filters disclosed herein, the frequencies of the band edges of the two filters can be close to each other, not for the purpose of coexistence, but without coexistence. The switchable elastic wave filters disclosed herein can selectively and electrically couple one or more elastic wave resonators in the filter to adjust performance for the purpose of coexistence and without coexistence.

[0039] A multiplexer may include a switchable elastic wave filter. The multiplexer may include a first filter and a second filter connected to the first filter at a common node. The first filter may include one or more elastic wave resonators, a plurality of switchable elastic wave resonators, and a switch configurable to at least a first state and a second state. The switch, in the first state, selects a different subset of the plurality of switchable elastic wave resonators than in the second state, and can use at least one or more elastic wave resonators together to filter radio frequency signals. By selecting different subsets of the switchable elastic wave resonators, the frequency domain of the band edge of the first filter can be shifted. For example, the different subsets may include a first subset and a second subset, where the first subset includes only the first switchable elastic wave resonator, and the second subset includes only the second switchable elastic wave resonator. The second filter may also be switchable in a given application. In a given application, the switchable elastic wave filter may be a band-pass filter. In some other applications, switchable acoustic wave filters can be used as band-stop filters.

[0040] The embodiments disclosed herein can achieve technical advantages over other filters and multiplexers. The embodiments disclosed herein can achieve reduced filter switching losses. A given switchable filter disclosed herein may have a single-switch loss. The embodiments disclosed herein can implement a simpler architecture and fewer elastic wave resonators than using separate filters for different conditions. This can advantageously result in a smaller physical layout and lower costs.

[0041] Figures 1A, 1B, and 1C are schematic block diagrams of multiplexers according to several embodiments. These multiplexers may include two elastic wave filters. One of these elastic wave filters is a band-pass filter, and the other is a band-stop filter. One or both of these elastic wave filters may be switchable. The exemplary multiplexers shown in Figures 1A, 1B, and 1C are diplexers.

[0042] Figure 1A shows a multiplexer 10 including a bandpass filter 12 and a switchable bandstop filter 14. Both the bandpass filter 12 and the switchable bandstop filter 14 may be elastic wave filters. The bandpass filter 12 can filter a first radio frequency (RF) signal propagating between a first RF node RF1 and an antenna node ANT. The antenna node ANT is the common node of the multiplexer 10 to which the bandpass filter 12 and the switchable bandstop filter are connected. The first RF signal may be a WiFi signal, such as a 2.4 GHz WiFi signal. The WiFi signal is an example of a wireless local area network (WLAN) signal.

[0043] The switchable bandstop filter 14 can filter the second RF signal propagating between the second RF node RF2 and the antenna node ANT. The second RF signal may be within the cellular operating band. The switchable bandstop filter 14 can generally block frequency components corresponding to the passband of the bandpass filter 12. The signal propagating between the second RF node RF2 and the antenna node ANT may be a mid-high band (MHB) signal. The switchable bandstop filter 14 can provide a stopband for the bandpass filter, such as the 2.4GHz WiFi stopband in the MHB bandpass filter.

[0044] The switchable bandstop filter 14 is operable in a first state and a second state. In the first state, the switchable bandstop filter 14 may have a stopband that corresponds to the entire passband of the bandpass filter 12. In the second state, the switchable bandstop filter 14 may have a stopband whose lower band edge is below the lower band edge of the passband of the bandpass filter 12. In the second state compared to the first state, the switchable bandstop filter 14 can move the lower edge of its stopband away from the lower band edge of the passband of the bandpass filter 12. In the first state, the bandpass filter 12 may be inactive and not filter radio frequency signals. The second state may exist for coexistence.

[0045] Figure 1B shows a multiplexer 15 including a switchable bandpass filter 16 and a bandstop filter 18. Both the switchable bandpass filter 16 and the bandstop filter 18 may be elastic wave filters. The switchable bandpass filter 16 is operable in a first state and a second state. In the first state, the switchable bandpass filter 16 may have a passband corresponding to the entire operating band. In the second state, the switchable bandpass filter 16 may have a passband where the lower band edge of the stopband is above the lower end of the operating band. The switchable bandpass filter 12 can move the lower edge of its stopband away from the lower edge of the stopband of the bandstop filter 18 in the second state compared to the first state. In the first state, the bandstop filter 18 may be inactive and not filter radio frequency signals. The second state may exist for coexistence. The bandstop filter 18 may have a stopband that generally corresponds to the passband of the operating band associated with the switchable bandpass filter 16.

[0046] Figure 1C shows a multiplexer 19 including a switchable bandpass filter 16 and a switchable bandstop filter 14. In the multiplexer 19, both the bandpass filter and the bandstop filter are switchable. For the purpose of coexistence, the switchable bandpass filter 16 can move the edge of its passband, and the switchable bandstop filter 14 can move the edge of its stopband. When coexistence occurs, in the multiplexer 19, the switchable bandpass filter 16 can reduce its passband, and the switchable bandstop filter 14 can reduce its stopband. When coexistence does not occur, the switchable bandpass filter 16 has the entire passband, and the switchable bandstop filter 14 has the entire stopband.

[0047] The band-stop filters in Figures 1A, 1B, and 1C can provide a stopband to the large passband of a band-pass filter, low-pass filter, or high-pass filter. For example, the band-stop filters in Figures 1A, 1B, and 1C can provide a 2.4GHz WiFi stopband to a band-pass filter that allows an MHB signal to pass through.

[0048] Although the multiplexers in Figures 1A, 1B, and 1C each include a band-pass filter and a band-stop filter, any suitable principles and advantages of these embodiments can be applied to multiplexers with multiple band-pass filters and / or multiple band-stop filters.

[0049] Although moving a predetermined band edge of the filter is described with reference to Figures 1A to 1C, any suitable principles and advantages disclosed herein can be applied to any band edge of an elastic wave filter, or to two or more band edges of an elastic wave filter.

[0050] Examples of multiplexers in Figures 1A, 1B, and 1C will be explained with reference to Figures 2, 3, and 4, respectively.

[0051] Figure 2 is a schematic diagram of a multiplexer 20 comprising a band-pass filter 22 and a switchable band-stop filter 24 according to one embodiment. The multiplexer 20 is an example of the multiplexer 10 in Figure 1A. The illustrated multiplexer 20 is a diplexer. The multiplexer 20 includes a band-pass filter 22, a switchable band-stop filter 24, and a passive impedance network 26.

[0052] The band-pass filter 22 includes elastic wave resonators R1, R2, R3, R4, R5, R6, and R7. These elastic wave resonators may include one or more surface acoustic wave (SAW) resonators, one or more bulk elastic wave (BAW) resonators, one or more other elastic wave resonators, or any suitable combination thereof. For example, elastic wave resonators R1 to R7 may be BAW resonators. The band-pass filter 22 may have a passband for passing, for example, a 2.4GHz WiFi signal. The operating bandwidth for 2.4GHz WiFi may be from 2.40GHz to 2.48GHz.

[0053] As shown in the figure, the switchable bandstop filter 24 includes a capacitor C1, an inductor L1, elastic wave resonators R8, R9A, R9B, and a switch 28. The elastic wave resonators R8, R9A, R9B may include one or more SAW resonators, one or more BAW resonators, one or more other elastic wave resonators, or any suitable combination thereof. For example, the elastic wave resonators R8, R9A, R9B may be BAW resonators. The elastic wave resonators R9A, R9B are switchable elastic wave resonators in the multiplexer 20.

[0054] Switch 28 selects between series elastic wave resonators R9A and R9B, which are part of a group of elastic wave resonators in a switchable bandstop filter 24 that filters RF signals. In the first state, switch 28 can electrically connect the first series elastic wave resonator R9A to node N1 of the switchable bandstop filter 24. Switch 28 can also electrically isolate the second series elastic wave resonator R9B from node N1 in the first state. Elastic wave resonators R8 and R9A filter RF signals in the first state. Elastic wave resonator R9B does not filter RF signals in the first state.

[0055] In the second state, switch 28 can electrically connect the second series elastic wave resonator R9B to node N1. Switch 28 can also electrically isolate the first series elastic wave resonator R9A from node N1 in the second state. Elastic wave resonators R8 and R9B filter the RF signal in the second state. Elastic wave resonator R9A does not filter the RF signal in the second state. As shown in the figure, the switchable bandstop filter 24 is in the second state.

[0056] In a given application, the switch 28 can electrically connect both the series elastic wave resonators R9A and R9B to node N1 in the third state.

[0057] The series elastic wave resonators R9A and R9B may have one or more different characteristics. These different characteristics may include one or more of the following: resonant frequency, anti-resonant frequency, quality factor (Q), harmonic distortion, linearity, frequency temperature coefficient (TCF), power handling, etc.

[0058] The series elastic wave resonators R9A and R9B may have different resonant frequencies. Therefore, by toggling between the first and second states, the switch 28 can adjust the bandwidth of the switchable bandstop filter 24. In the first state, the switchable bandstop filter 24 may have a stopband corresponding to the entire operating band associated with the bandpass filter 22. In the second state, the lower band edge of the stopband of the switchable bandstop filter 24 can be moved to a higher frequency compared to the first state. This may come at the expense of a portion of the stopband corresponding to the operating band associated with the radio frequency signal filtered by the bandpass filter. In the second state, the switchable bandstop filter 24 may have a reduced stopband. The second state may exist for coexistence.

[0059] The passive impedance network 26 includes capacitors C2, C3, C4, and inductors L2, L2, L4. The passive impedance network is coupled between filters 22 and 24 and the antenna node ANT. The antenna node ANT is the common node of the multiplexer 20, to which the bandpass filter 22 and the switchable bandstop filter 24 are connected. The passive impedance network 26 can provide filtering and / or impedance transformation.

[0060] The passive impedance network 26 can implement an inductor-capacitor (LC) filter. An LC filter can attenuate one or more harmonics generated by the switching of a switchable filter. Therefore, one or more harmonics can be suppressed at the antenna node ANT. In some examples, an LC filter can attenuate harmonics from multiple switches of a multiplexer. An LC filter can provide low-pass filtering that protects the switches and / or elastic wave resonators of the multiplexer from one or more relatively high power blocker signals. The passive impedance network 26 can contribute to meeting intermodulation specifications. The passive impedance network 26 can filter and remove intermodulation distortion and / or one or more spurious signals. The passive impedance network 26 can be implemented by any suitable inductor-capacitor circuit topology for a particular application.

[0061] A multiplexer conforming to any suitable principles and advantages disclosed herein can be implemented in various applications without a passive impedance network 26. Accordingly, a multiplexer comprising at least one switchable filter conforming to any suitable principles and advantages disclosed herein can be implemented without an LC filter coupled between the switchable filter of the multiplexer and a common node or antenna node.

[0062] Figure 3 is a schematic diagram of a multiplexer comprising a switchable bandpass filter 32 and a bandstop filter 34 according to one embodiment. The multiplexer 30 is an example of the multiplexer 15 in Figure 1A. The illustrated multiplexer 30 is a diplexer. The multiplexer 30 includes a switchable bandpass filter 32, a bandstop filter 34, and a passive impedance network 26.

[0063] The switchable bandpass filter 32 includes elastic wave resonators R1, R2, R3, R4, R5, R6A, R6B, R7, and a switch 38. The switchable bandpass filter 32 is similar to the bandpass filter 22 in Figure 2, except that the switchable bandpass filter 32 includes a switch 38 that selectively and electrically connects the shunt resonators R6A and / or R6B to node N2. The shunt elastic wave resonators R6A and R6B are switchable elastic wave resonators in the multiplexer 30.

[0064] The shunt elastic wave resonators R6A and R6B may have one or more different characteristics. These different characteristics may include one or more of the following: anti-resonant frequency, resonant frequency, quality factor, harmonic distortion, linearity, TCF, power handling, etc. For example, the shunt resonators R6A and R6B may have different resonant frequencies. By changing the state of switch 38, the lower edge of the passband of the switchable bandpass filter 32 can be adjusted.

[0065] Switch 38 selects which of the shunt elastic wave resonators R6A and / or R6B should be included in the group of elastic wave resonators of the switchable bandpass filter 32 that filters the RF signal. In the first state, switch 38 can electrically connect the first shunt elastic wave resonator R6A to node N2 of the switchable bandpass filter 32. Switch 38 can also electrically isolate the second shunt elastic wave resonator R6B from node N2 in the first state. Elastic wave resonators R1 to R5, R6A and R7 filter the RF signal in the first state. Elastic wave resonator R9B does not filter the RF signal in the first state.

[0066] In the second state, switch 38 can electrically connect the second shunt elastic wave resonator R6B to node N2. Switch 38 can also electrically isolate the first shunt elastic wave resonator R6A from node N2 in the second state. Elastic wave resonators R1 to R5, R6B and R7 filter the RF signal in the second state. Elastic wave resonator R6A does not filter the RF signal in the second state. In the second state, the lower band edge of the switchable bandpass filter 32 may be at a higher frequency than in the first state. This may result in a sacrifice of performance in the lower portion of the passband compared to the first state. Conversely, in the first state, the passband of the switchable bandpass filter 32 may cover the entire operating band. The second state may exist for coexistence. As shown in the figure, the switchable bandpass filter 32 is in the second state.

[0067] In a given application, the switch 38 can electrically connect both the shunt elastic wave resonators R6A and R6B to node N2 in the third state.

[0068] The band-stop filter 34 is similar to the switchable band-stop filter 24 in Figure 2, but differs in that the band-stop filter 34 is not switchable. Therefore, the stopband of the band-stop filter 34 can be effectively fixed. In the band-stop filter 34, the series elastic wave resonator R9 is included in place of the series elastic wave resonators R9A and R9B and the switch 28 from the switchable band-stop filter 24.

[0069] Figure 4 is a schematic diagram of a multiplexer 40 comprising a switchable band-stop filter 24 and a switchable band-pass filter 32 according to one embodiment. In the multiplexer 40, both the band-pass filter 32 and the band-stop filter 24 are switchable. With the multiplexer 40, the performance of the switchable band-stop filter 24 and / or the switchable band-pass filter 32 can be reduced when they coexist.

[0070] In an exemplary application, the switchable bandpass filter 32 is a 2.4GHz WiFi filter, and the switchable bandstop filter 24 is a bandstop filter that blocks 2.4GHz WiFi for MHB filtering. In the exemplary application, the switchable bandpass filter 32 may have a resonant frequency R6A that supports 2.36GHz, the lower edge of the 2.4GHz WiFi passband, and a resonant frequency R6B that supports 2.40GHz, the lower edge of the 2.4GHz WiFi passband. In this example, if shunt resonator R6A is selected, the passband of the switchable bandpass filter 32 may be from 2.36GHz to 2.48GHz. If shunt resonator R6B is selected, the passband of the switchable bandpass filter 32 may be from 2.43GHz to 2.48GHz, or from 2.40GHz to 2.48GHz. Therefore, by selecting the shunt elastic wave resonator R6B instead of the shunt elastic wave resonator R6A, the lower edge of the passband can be shifted to an increasing frequency, sacrificing the performance of the switchable bandpass filter 32 for the lower portion of the passband. This performance sacrifice is made for the purpose of coexistence; otherwise, a larger passband could be used.

[0071] In the switchable bandstop filter 24, in an exemplary application, the series elastic wave resonator R9A may have an anti-resonant frequency supporting 2.36 GHz of the 2.4 GHz WiFi stopband edge, and the series elastic wave resonator R9B may have an anti-resonant frequency supporting 2.40 GHz of the 2.4 GHz WiFi stopband edge. In this example, by toggling the state of the switch 28, the stopband of the switchable bandstop filter 24 is adjusted from 2.36 GHz to 2.48 GHz to 2.40 GHz to 2.48 GHz. The passband of the filter including the switchable bandstop filter 24 is adjusted from 1.71 GHz to 2.36 GHz to 1.71 GHz to 2.40 GHz.

[0072] In a given example, only one of the switchable bandstop filter 24 or the switchable bandpass filter 32 can have its band edge moved by the state of switches 28 or 38, respectively. In some examples, the switchable bandstop filter 24 and the switchable bandpass filter 32 can have their band edges moved away from each other by the state of switches 28 and 38. In some examples, the switchable bandstop filter 24 and the switchable bandpass filter 32 can have their band edges shifted in the same direction at frequency to maintain the same or similar frequency separation from each other by the state of switches 28 and 38.

[0073] The multiplexer 40 was simulated under two different conditions. In the first condition, the entire 2.4 GHz WiFi passband is given for the band-pass filter, and the corresponding stopband is also given for the other filters. In the second condition, the passband and stopband are adjusted for coexistence. Figure 5A is a graph of the insertion loss of the switchable band-pass filter 32 for the first and second conditions. Figure 5B is a graph of the stopband associated with the switchable band-stop filter 24 for the first and second conditions.

[0074] Figure 5A is a graph of the insertion loss of a switchable bandpass filter comparing the entire passband with the passband adapted for coexistence. Figure 5A plots the simulation results of insertion loss for the 2.4GHz WiFi band. The first curve 52 corresponds to the insertion loss of the entire 2.4GHz WiFi band for the first state. The second curve 54 corresponds to the insertion loss of the entire 2.4GHz WiFi band for coexistence in the second state. Figure 5A shows that insertion loss is sacrificed at the lower end of the 2.4GHz WiFi band for coexistence in the second state. The passband of the switchable bandpass filter 32 may be reduced at the lower end of the 2.4GHz WiFi band for coexistence in the second state.

[0075] Figure 5B is a graph of the stopband frequency response of the switchable bandstop filter 24, comparing the entire stopband with the stopband adapted for coexistence. The first curve 56 corresponds to the frequency response with a stopband for the entire 2.4GHz WiFi band for the first state. The second curve 58 corresponds to the frequency response with a narrow stopband of the 2.4GHz WiFi band for coexistence in the second state. Figure 5B shows that the lower end of the 2.4GHz WiFi stopband is sacrificed for coexistence in the second state.

[0076] Figure 6A is a graph of the frequency response of the switchable bandpass filter 32 comparing the entire passband with the passband adapted for coexistence. The first curve 62 represents the entire 2.4GHz WiFi passband for the first state. The second curve 64 represents the 2.4GHz WiFi band reduced for coexistence in the second state. A switch 38, which selects between different shunt elastic wave resonators R6A or R6B, can toggle the state of the switchable bandpass filter 32 between the first and second states. The simulation results show that for the second state, the lower band edge of the passband moves in a frequency-increasing manner. The simulation results show that the performance in the second state at the lower band edge and lower portion of the 2.4GHz WiFi passband is sacrificed compared to the first state. In the graph of Figure 6A, the passband is from approximately 2.4GHz to 2.48GHz in the first state and from approximately 2.43GHz to 2.48GHz in the second state.

[0077] Figure 6B is a graph of the expanded frequency response of the switchable bandpass filter 24 for the stopband, comparing the entire stopband with the stopband adapted for coexistence. The first curve 66 represents the entire 2.4 GHz WiFi stopband for the first state. The second curve 68 represents the 2.4 GHz WiFi band reduced for coexistence in the second state. A switch 28, which selects a different shunt elastic wave resonator R9A or R9B, can toggle the state of the switchable bandpass filter 28 between the first and second states. Simulation results show that for the second state, the lower band edge of the stopband moves to a higher frequency compared to the first state. Simulation results also show that for the second state, performance in a portion of the stopband in the second state is sacrificed compared to the first state.

[0078] Any suitable principles and advantages of the switchable filters disclosed herein can be implemented in standalone filters and / or any other suitable multiplexers. Figures 7 and 8 show examples of switchable bandpass filters. Figures 9 and 10 show examples of switchable bandstop filters. Any suitable elastic wave resonator can be implemented in these filters. For example, a BAW resonator can be included in any of the filters in Figures 7 to 10. The exemplary filters in Figures 7 to 10 are arranged to tune one band edge in the frequency domain. Any suitable principles and advantages disclosed herein can be implemented to tune two or more mode band edges in the frequency domain. For example, a bandpass filter may include the features in Figures 7 and 8 that tune two edges of the passband. As another example, a bandstop filter may include the features in Figures 9 and 10 that tune two edges of the stopband. The filters may include any suitable combination of the features of the embodiments in Figures 7 to 10.

[0079] One or more switchable filters, conforming to any suitable principles and advantages disclosed herein, can be configured to filter radio frequency signals in the fifth-generation (5G) New Radio (NR) operating band within frequency range 1 (FR1). FR1 can range from 410 megahertz (MHz) to 7.125 gigahertz (GHz), as specified, for example, in the current 5G NR specification. One or more filters, conforming to any suitable principles and advantages disclosed herein, may be included in filters configured to filter radio frequency signals in the fourth-generation (4G) Long-Term Evolution (LTE) operating band. One or more filters, conforming to any suitable principles and advantages disclosed herein, may be included in filters having passbands that include the 4G LTE operating band and the 5G NR operating band. One or more switchable filters, conforming to any suitable principles and advantages disclosed herein, can be configured to filter radio frequency signals in wireless local area network bands, such as the WiFi band. One or more switchable filters, conforming to any suitable principles and advantages disclosed herein, may have passbands corresponding to the 5G NR operating band, the 4G LTE operating band, the 4G LTE operating band and 5G operating band, or the radio local area network operating band. One or more switchable filters, conforming to any suitable principles and advantages disclosed herein, may have blockbands corresponding to the 5G NR operating band, the 4G LTE operating band, the 4G LTE operating band and 5G operating band, or the radio local area network operating band.

[0080] A particular embodiment may be described with reference to a switching elastic wave resonator that adjusts the bandwidth of a filter and / or the location of the band edge of the filter in the frequency domain. Any suitable principles and advantages disclosed herein can be applied to switching elastic wave resonators to adjust one or more other suitable properties of a filter, such as linearity, harmonic distortion, power handling, etc. For example, multiple elastic wave resonators with different linearity characteristics can be switched in and / or out of a filter to achieve different linearity performance in different states. Another example is that multiple elastic wave resonators with different characteristics can be switched in and / or out of a filter to achieve different power handling performance in different states.

[0081] Figure 7 is a schematic diagram of a switchable bandpass filter 32 according to one embodiment. The switchable bandpass filter 32 has switchable shunt elastic wave resonators R6A and R6B. In a bandpass filter, the shunt elastic wave resonators typically affect the lower edge of the passband. Switch 38 can select shunt elastic wave resonator R6A in a first state and shunt elastic wave resonator R6B in a second state. This allows the lower edge of the passband to be adjusted for different states of the switchable bandpass filter 32. A series elastic wave resonator R7 may be used as the first elastic wave resonator of the switchable bandpass filter 32 from the common node of the multiplexer shown in Figures 3 and 4, for example. Alternatively, for some other applications, a series elastic wave resonator R1 may be used as the first elastic wave resonator of the switchable bandpass filter 32 from the common node of the multiplexer. By making the series elastic wave resonator R1 the first elastic wave resonator from the common node of the multiplexer, any noise and / or distortion from switch 38 can be moved further away from the common node. In some examples, switch 38 can select both shunt elastic wave resonators R6A and R6B for the third state. The switchable bandpass filter 32 has only single-switch losses.

[0082] Figure 8 is a schematic diagram of a switchable bandpass filter 80 according to another embodiment. The switchable bandpass filter 80 has switchable series elastic wave resonators R7A and R7B. In a bandpass filter, the series elastic wave resonators typically affect the upper edge of the passband. Switch 88 can select the series elastic wave resonator R7A in one state and the series elastic wave resonator R7B in the other state. This allows the upper edge of the passband to be adjusted for different states of the switchable bandpass filter 80. For example, the switchable bandpass filter 80 can lower the upper band edge of the passband to allow coexistence with other frequency bands above the passband. Alternatively, the series elastic wave resonators R7A and / or R7B may be used as the first elastic wave resonator of the switchable bandpass filter 80 from the common node of the multiplexer. Alternatively, for some other applications, the series elastic wave resonator R1 may be used as the first elastic wave resonator of the switchable bandpass filter 80 from the common node of the multiplexer. In some examples, switch 88 can select both the series elastic wave resonators R7A and R7B to the third state. The switchable bandpass filter 80 has only single-switch losses.

[0083] Figure 9 is a schematic diagram of a switchable bandstop filter 24 according to one embodiment. The switchable bandstop filter 24 has switchable series elastic wave resonators R9A and R9B. In a bandstop filter, the series elastic wave resonators typically affect the lower edge of the stopband. Switch 28 can select series elastic wave resonator R9A in the first state and series elastic wave resonator R9B in the second state. This allows the lower edge of the stopband to be adjusted for different states of the switchable bandstop filter 24. In some examples, switch 28 can select both series elastic wave resonators R9A and R9B for the third state. The switchable bandstop filter 24 has only single-switch loss.

[0084] Figure 10 is a schematic diagram of a switchable bandstop filter 100 according to another embodiment. The switchable bandstop filter 100 has switchable shunt elastic wave resonators R8A and R8B. In a bandstop filter, the shunt elastic wave resonator typically affects the upper edge of the stopband. Switch 108 can select shunt elastic wave resonator R8A in one state and shunt elastic wave resonator R8B in other states to adjust the upper edge of the stopband for different states of the switchable bandstop filter 100. For example, the switchable bandstop filter 100 can lower the upper band edge of the stopband to coexist with other frequency bands above the stopband. In some examples, switch 108 can select both shunt elastic wave resonators R8A and R8B for the third state. The switchable bandstop filter 100 has only single-switch loss.

[0085] Although embodiments disclosed herein may relate to filters comprising switches configured to selectively couple different elastic wave resonators to the nodes of the filter, any suitable principles and advantages disclosed herein can be implemented in applications having an elastic wave resonator with a fixed connection to the nodes of the filter, and one or more other elastic wave resonators that may optionally be connected in parallel to the said elastic wave resonator by a switch. For example, in some such applications, there may be one state in which only a shunt elastic wave resonator with a fixed connection is connected to the nodes, and one or more other states with at least one other shunt elastic wave resonator connected in parallel to the said shunt elastic wave resonator via a switch. As another example, in some applications, there may be one state in which only a series elastic wave resonator with a fixed connection is connected to the nodes, and one or more other states with at least one other series elastic wave resonator connected in parallel to the said series elastic wave resonator via a switch.

[0086] Although embodiments disclosed herein may relate to filters comprising switches configured to selectively couple two different elastic wave resonators to the nodes of the filter, any suitable principles and advantages disclosed herein can also be implemented by switches configured to selectively couple three or more elastic wave resonators to the nodes of the filter. Figures 11 and 12 show examples of switches configured to selectively couple one or more of at least three switches to the nodes of the filter. Any suitable principles and advantages of these embodiments can be implemented together with each other and / or together with any suitable features of one or more other embodiments disclosed herein.

[0087] Figure 11 is a schematic diagram showing a switch 118 configured to selectively and electrically connect switchable shunt elastic wave resonators RSHA, RSHB, and RSHN to node NSH of an elastic wave filter stage 110 according to one embodiment. In a first state, the switch 118 can select a different subset of the switchable elastic wave resonators RSHA-RSHN than in a second state, and use at least a series elastic wave resonator RSE together to filter radio frequency signals. By selecting a different subset of the switchable elastic wave resonators RSHA-RSHN, the band edge of the filter, including the filter stage 110, can be shifted in the frequency domain. The switch 118 can electrically connect a single shunt elastic wave resonator from RSHA, RSHB, and RSHN to node NSH at one time. Alternatively or additionally, the switch 118 can electrically connect two or more shunt elastic wave resonators RSHA, RSHB, and RSHN to node NSH at one time. The illustrated filter stage 110 also includes a series elastic wave resonator RSE. The filter stage 110 may be included in a filter comprising one or more other elastic wave resonator filter stages. Alternatively or additionally, the filter stage 110 may be included in a filter comprising an inductor-capacitor circuit.

[0088] Figure 12 is a schematic diagram showing a switch 128 configured to selectively and electrically connect switchable series elastic wave resonators RSEA, RSEB, and RSEN to node NSE of an elastic wave filter stage 120 according to one embodiment. In a first state, the switch 128 can select a different subset of the switchable elastic wave resonators RSEA-RSEN than in a second state, and use at least a shunt elastic wave resonator RSH together to filter radio frequency signals. By selecting a different subset of the switchable elastic wave resonators RSEA-RSEN, the band edge of the filter, including the filter stage 120, can be shifted in the frequency domain. The switch 128 can electrically connect a single series elastic wave resonator from RSEA, RSEB, and RSEN to node NSE at one time. Alternatively or additionally, the switch 128 can electrically connect two or more series elastic wave resonators RSEA, RSEB, and RSEN to node NSE at one time. The illustrated filter stage 120 also includes a shunt elastic wave resonator RSH. The filter stage 120 may be included in a filter comprising one or more other elastic wave resonator filter stages. Alternatively or additionally, the filter stage 120 may be included in a filter comprising an inductor-capacitor circuit.

[0089] As described above, any suitable principles and advantages disclosed herein can be implemented in any suitable multiplexer. Any subset of the filters of such multiplexer, or all of the filters of such multiplexer, may be switchable. Embodiments of a triplexer comprising one or more switchable elastic wave filters are described with reference to Figures 13 to 22. In these embodiments, the bandwidth of the switchable elastic wave filters can be adjusted by switches that selectively couple one or more elastic wave resonators to the nodes of the filters. Any suitable combination of these triplexer features can be implemented together with each other and / or with any other suitable combination of the features disclosed herein.

[0090] Figure 13 is a schematic block diagram of a multiplexer 130 according to one embodiment. The multiplexer 130 is a triplexer. As shown, the multiplexer 130 includes a first switchable elastic wave filter 132, a second switchable elastic wave filter 134, and a third filter 136. The illustrated filters 132, 134, and 136 are coupled to each other at the antenna node ANT. The multiplexer 130 may be an antennaplexer.

[0091] The first switchable elastic wave filter 132 may be a band-pass filter. The first switchable elastic wave filter 132 may be a band-pass filter configured to pass a 2.4 GHz WiFi signal. The bandwidth of the first switchable elastic wave filter 132 can be adjusted according to any suitable principles and advantages disclosed herein. The first switchable elastic wave filter 132 is shown in block form, and illustrative symbols indicate that the bandwidth of the first switchable elastic wave filter 132 can be varied in different states. The same output node of the first switchable elastic wave filter 132 may be coupled to the antenna node ANT in different states.

[0092] The second switchable elastic wave filter 134 may be an MHB filter. The second switchable elastic wave filter 134 may include a notch in its passband for the frequency band corresponding to the first switchable elastic wave filter 132. For example, the second switchable elastic wave filter 134 may have an aa notch for the 2.4 GHz WiFi band. The notch bandwidth of the second switchable elastic wave filter 134 can be adjusted according to any suitable principles and advantages disclosed herein. The second switchable elastic wave filter 134 is shown in block form, and illustrative symbols indicate that the second switchable elastic wave filter 134 can vary its notch bandwidth in different states. The same output node of the second switchable elastic wave filter 134 may be coupled to an antenna node ANT in different states.

[0093] The third filter 136 may be a high-pass filter. The third filter 136 may be an ultra-high bandwidth (UHB) filter. The third filter may be an inductor-capacitor filter including an inductor and a capacitor, or an inductor and a capacitor with one or more elastic wave resonators added.

[0094] An example of multiplexer 130 is described with reference to Figures 14A–16, 19, and 20. An example of a similar multiplexer with one switchable acoustic wave filter is described with reference to Figures 17 and 18. Any suitable combination of features of the embodiments in Figures 13 to 20 can be implemented together.

[0095] Figure 14B is a schematic diagram of a multiplexer 140 equipped with a switchable filter according to one embodiment. The multiplexer 140 is an example of the multiplexer 130 in Figure 13. As shown, the multiplexer 140 includes a first switchable elastic wave filter 142, a second switchable elastic wave filter 145, a third filter 148, and a passive impedance network 26.

[0096] The first switchable elastic wave filter 142 includes switches 143 and 144, each configured to selectively and electrically connect an elastic wave resonator to a corresponding node of the first switchable elastic wave filter 142. The first switchable elastic wave filter 142 also includes elastic wave resonators R0, R1A, R1B, R2, R3, R4, R5, R6, R7A, R7B, and a series inductor L5. The elastic wave resonators R1A, R1B, R7A, and R7B are switchable elastic wave resonators.

[0097] Switches 143 and 144 can connect different elastic wave resonators to the nodes of the first switchable filter to adjust the bandwidth of the filter for different states. For example, in the first state, switch 143 can connect elastic wave resonator R1A to elastic wave resonator R0 and electrically isolate elastic wave resonator R1B from elastic wave resonator R0. Switch 144 can connect elastic wave resonator R7A to passive impedance network 26 and electrically isolate elastic wave resonator R7B from passive impedance network 26 in the first state. In this example, in the second state, switch 143 can connect elastic wave resonator R1B to elastic wave resonator R0 and electrically isolate elastic wave resonator R1A from elastic wave resonator R0. Switch 144 can connect elastic wave resonator R7B to passive impedance network 26 and electrically isolate elastic wave resonator R7A from passive impedance network 26 in the first state.

[0098] In the multiplexer 140, the first switchable elastic wave filter 142 and the second switchable elastic wave filter 145 are coupled to the antenna node ANT via a passive impedance network 26. The passive impedance network may implement an LC filter. The LC filter can attenuate one or more harmonics generated by one or more switches (e.g., switches 144 and / or 146) of the switchable elastic wave filters 142 and / or 145. This suppresses one or more harmonics at the antenna node ANT. The LC filter can suppress intermodulation distortion and / or spurious responses. The LC filter can provide low-pass filtering to protect one or more switches and / or elastic wave resonators of the multiplexer 140 from one or more relatively high power blocker signals.

[0099] In a given application, the first switchable elastic wave filter 142 may function as a band-pass filter for the 2.4GHz WiFi band. For example, switches 143 and 144 can adjust the passband of the first switchable elastic wave filter 142 from 2.40GHz to 2.48GHz in the first state and from 2.40GHz to 2.46GHz in the second state. In this example, the first state may correspond to passing the entire 2.4GHz WiFi band. In the second state, high isolation is provided for band 53 (2.4835GHz to 2.495GHz), while performance at the upper end of the 2.4GHz WiFi band may be sacrificed in this example.

[0100] The second switchable elastic wave filter 145 includes a switch 146 configured to selectively and electrically connect different elastic wave resonators to the nodes of the second switchable elastic wave filter 145. The switchable elastic wave filter 145 includes capacitors C1 and C7, inductors L1, L6, L7, and elastic wave resonators R8A, R8B, R9, R10. Elastic wave resonators R8A and R8B are switchable elastic wave resonators. The switch 146 can adjust the bandwidth of the stopband of the second switchable filter 145 for different states by connecting different elastic wave resonators to the nodes. In a given application, the switchable elastic wave filter 145 may be a band-stop-pass filter configured to provide a stopband corresponding to the 2.4 GHz WiFi band to an MHB filter. As an example, switch 146 can adjust the stopband of the second first switchable elastic wave filter 145 from 2.40 GHz to 2.48 GHz in the first state and from 2.40 GHz to 2.46 GHz in the second state. Switch 146 can electrically connect elastic wave resonator R8A to the node between elastic wave resonators R9 and R10 in the first state, and electrically isolate elastic wave resonator R8B from the node between elastic wave resonators R9 and R10 in the first state. Switch 146 can electrically connect elastic wave resonator R8B to the node between elastic wave resonators R9 and R10 in the second state, and electrically isolate elastic wave resonator R8A from the node between elastic wave resonators R9 and R10 in the second state. In this example, the first state may correspond to passing the entire 2.4 GHz WiFi band. In the second state, high isolation is provided for band 53, but in this example, stopband performance may be sacrificed at the upper end of the 2.4GHz WiFi band.

[0101] The third filter 148 may be a high-pass filter. The third filter can pass UHB signals. As shown in the figure, the third filter 148 is an inductor-capacitor filter. The illustrated third filter 148 includes capacitors C8 and C9, and inductors L8, L9 and L10. The third filter 148 may include any suitable type of inductor and any suitable type of capacitor. The third filter 148 may implement any suitable inductor-capacitor filter topology, any suitable elastic wave resonator filter topology, or any suitable filter topology including an inductor-capacitor circuit and one or more elastic wave resonators. The third filter 148 is connected to the first switchable elastic wave filter 142 and the second switchable elastic wave filter 145 at the common node of the multiplexer 140. The common node may be an antenna node ANT as shown in the figure.

[0102] Figure 14B is a schematic diagram of a multiplexer 149 equipped with a switchable filter according to one embodiment. The multiplexer 149 is similar to the multiplexer 140 in Figure 14A, except that the switchable elastic wave filter 147 in Figure 14B is equipped with an elastic wave resonator R7 instead of the switch 144 and the corresponding switchable elastic wave resonators R7A and R7B. In the switchable elastic wave filter 147, the switch 143 is positioned away from the antenna node ANT. Therefore, the intermodulation distortion and / or harmonic distortion associated with the switch 143 are introduced away from the antenna node ANT. Such intermodulation distortion and / or harmonic distortion can be attenuated at the antenna node ANT.

[0103] Figure 15 is a schematic diagram of a multiplexer 150 equipped with a switchable filter according to another embodiment. The multiplexer 150 is similar to the multiplexer 140 in Figure 14A, except that the switch 154 and its corresponding switchable elastic wave resonators R5A and R5B are located in different places in the filter topology of the first switchable filter 152 compared to the switch 143 and its corresponding switchable elastic wave resonators R1A and R1B of the first switchable filter 142 in Figure 14A. A switch configured to selectively and electrically connect an elastic wave resonator to a node of the filter can be positioned at any suitable location in the filter topology for a particular application. Two or more switches configured to selectively and electrically connect an elastic wave resonator to a corresponding node of the filter can be positioned at any suitable location in the filter topology for a particular application.

[0104] Figure 16 is a schematic diagram of a multiplexer 160 comprising a switchable filter according to another embodiment. In the multiplexer 160, the first switchable filter 162 includes a switch 144 that selectively and electrically connects switchable elastic wave resonators R7A and R7B to the node of the first switchable filter 162. The switch 144 can adjust the bandwidth of the first switchable filter 162. The multiplexer 160 also includes a second switchable filter. The second switchable filter includes switches 163 and 164 that together select either a first subfilter 165 or a second subfilter 166. Subfilters 165 and 166 each include at least one filter stage and a plurality of elastic wave resonators. As shown, the first subfilter 165 includes elastic wave resonators R11 and R12. The second subfilter 166 shown includes elastic wave resonators R8, R9, R10 and an inductor-capacitor circuit. The inductor-capacitor circuit of the second subfilter may include inductors L6 and L7 and capacitor C7.

[0105] Figure 17 is a schematic diagram of a multiplexer 170 comprising a switchable filter according to one embodiment. The multiplexer 170 includes a single switchable filter. In the multiplexer 170, the first switchable filter 162 is a switchable bandpass filter. In the multiplexer 170, the second filter 175 is fixed and not switchable. The second filter 175 may be the same as or similar to the second subfilter 166 in Figure 16. Switching the first switchable filter 162 to adjust the bandwidth of the first switchable filter 162 together with the stopband generated by the second filter 175 may satisfy performance specifications in a given application.

[0106] Figure 18 is a schematic diagram of a multiplexer 180 equipped with a switchable filter according to another embodiment. The multiplexer 180 is similar to the multiplexer 170 in Figure 17, except that the first switchable elastic wave filter 142 of the multiplexer 180 includes two switches and corresponding switchable elastic wave resonators. The multiplexer 180 is similar to the multiplexer 140 in Figure 14A, except that the second filter 175 of the multiplexer 180 is fixed rather than switchable.

[0107] Figure 19 is a schematic diagram of a multiplexer 190 equipped with a switchable filter according to another embodiment. The multiplexer includes a first switchable filter 192 comprising switches 193 and 144 and switchable elastic wave resonators R3A, R3B, R7A, and R7B. Multiplexer 190 is similar to multiplexers 140 and 150 in Figures 14A and 15, respectively, except that the first switchable elastic wave filter 192 of multiplexer 190 includes switches 193 and corresponding switchable elastic wave resonators R3A and R3B in different locations in the filter topology. Multiplexer 190 is similar to multiplexer 140 in Figure 14A, except that switches 193 and corresponding switchable elastic wave resonators R3A and R3B are located in different locations in the filter topology than switches 143 and corresponding switchable elastic wave resonators R1A and R1B of multiplexer 140. Multiplexer 190 is similar to multiplexer 150 in Figure 15, but differs in that switch 193 and its corresponding switchable elastic wave resonators R3A and R3B are located in different places in the filter topology than switch 154 and its corresponding switchable elastic wave resonators R5A and R5B of multiplexer 150.

[0108] Figure 20 is a schematic diagram of a multiplexer 200 equipped with a switchable filter according to one embodiment. The multiplexer 200 is similar to the multiplexers 140, 150, and 190, but differs in that the multiplexer 200 includes a first switchable elastic wave filter 162 equipped with a single switch 144.

[0109] In the switchable filters disclosed herein, the switchable elastic wave resonator may have, in a given state, one end electrically connected to the filter and the other end electrically isolated from the filter. A termination impedance may be electrically connected in parallel to one or more switchable elastic wave resonators via a switch when none of the elastic wave resonators are selected. Such a termination impedance may improve spurious performance. Exemplary termination impedances and associated switches are described with reference to Figures 21 and 22. Any suitable principles and advantages described with reference to Figures 21 and / or 22 can be implemented according to any suitable principles and advantages of any of the embodiments described above.

[0110] Figure 21 is a schematic diagram of a multiplexer 210 having a switchable filter with a termination impedance according to one embodiment. In the multiplexer 210, the first switchable filter 212 includes a switchable circuit 213. A switch 214 of the switchable circuit 213 can selectively connect switchable elastic wave resonators R7A, R7B to the nodes of the first switchable filter 212. The switch 214 can also electrically connect an unselected switchable elastic wave resonator to a termination impedance 215. The termination impedance 215 may be any suitable termination impedance, such as one or more resistors, one or more capacitors, one or more inductors, one or more resistors connected to one or more inductors, etc. The termination impedance 215 may include any suitable passive impedance element that gives the desired spurious performance in the passband and / or stopband. The termination impedance 215 may be, for example, 50 ohms. Switch 214 can connect the termination impedance 215 in parallel to an unselected switchable series elastic wave resonator.

[0111] In the switchable circuit 213, the termination impedance 215 can be connected in parallel to a single switchable elastic wave resonator R7A. Switch 214 can selectively and electrically connect the electrodes of the switchable elastic wave resonator R7A to the termination impedance 215. Switch 214 can connect the termination impedance 215 in parallel to the switchable elastic wave resonator R7A when not selected, and can electrically isolate one end of the termination impedance 215 from the switchable elastic wave resonator R7A when selected. As shown in Figure 20, the switchable elastic wave resonator R7A is selected, and one end of the termination impedance 215 is electrically isolated from the switchable elastic wave resonator R7A. The termination impedance 215 can be connected in parallel to the switchable elastic wave resonator R7A selected for modes in which the passband of the filter 212 is reduced. The termination impedance 215 can be connected in parallel to the switchable elastic wave resonator R7A selected for coexisting modes. The termination impedance 215 can be selectively connected in parallel to the switchable elastic wave resonator R7A.

[0112] The multiplexer 210 also includes a second switchable filter 216 comprising a switchable circuit 217. A switch 218 of the switchable circuit 217 can selectively connect switchable elastic wave resonators R8A, R8B to the nodes of the second switchable filter 216. The switch 218 can also electrically connect an unselected elastic wave resonator to a termination impedance 219. The termination impedance 219 may be any suitable termination impedance, such as one or more resistors, one or more capacitors, one or more inductors, one or more resistors connected to one or more inductors, etc., or any suitable combination thereof. The termination impedance 219 may include any suitable passive impedance element that gives the desired spurious performance in the passband and / or stopband. The termination impedance 219 may be, for example, 10 ohms. The switch 218 can connect the termination impedance 219 in parallel to the unselected shunt elastic wave resonator.

[0113] In the switchable circuit 217, the termination impedance 219 can be connected in parallel to a single switchable acoustic wave resonator R8A. Switch 218 can selectively and electrically connect the electrodes of the switchable acoustic wave resonator R8A to the termination impedance 219. Switch 218 can connect the termination impedance 219 in parallel to the switchable acoustic wave resonator R8A when the switchable acoustic wave resonator R8A is not selected, and can electrically isolate the termination impedance 219 from the switchable acoustic wave resonator R8A when the switchable acoustic wave resonator R8A is selected. As shown in Figure 20, the switchable acoustic wave resonator R8A is selected, and one end of the termination impedance 219 is electrically isolated from the switchable acoustic wave resonator R87A. The termination impedance 219 can be connected in parallel to the selected switchable acoustic wave resonator R8A for modes in which the stopband is reduced, for coexisting modes, for a relatively small percentage of time, etc., or for any appropriate combination thereof.

[0114] In the switchable circuits 213 and 217, the elastic wave resonators R7A, R7B, R8A, and R8A are shown as two elastic wave resonators in series with each other. Each elastic wave resonator may be divided into a series resonator or a parallel resonator. Any of the elastic wave resonators shown in the drawings can be implemented as series resonators. Any of the elastic wave resonators shown in the drawings can be implemented as parallel resonators.

[0115] Figure 22 is a schematic diagram of a multiplexer 220 having a switchable filter with a termination impedance according to another embodiment. The multiplexer 220 is similar to the multiplexer 210 in Figure 21, except that the termination impedance can be connected in parallel to each switchable elastic wave resonator. The termination impedance of the multiplexer 220 may include any appropriate combination of the features of the multiplexer 210.

[0116] In the multiplexer 220, each unselected switchable elastic wave resonator may be connected in parallel to the termination impedance. The multiplexer 220 includes a first switchable filter 222 comprising a switchable circuit 223. A switch 224 of the switchable circuit 223 can connect the termination impedance 225A or 225B in parallel to each of the unselected series elastic wave resonators R7A or R7B. The multiplexer 220 also includes a second switchable filter 226 comprising a switchable circuit 227. A switch 228 of the switchable circuit 227 can connect the termination impedance 229A or 229B in parallel to each of the unselected shunt elastic wave resonators R8A or R8B.

[0117] The switchable acoustic wave filters disclosed herein can be implemented in a radio frequency system. Figure 23 is a schematic diagram of an exemplary radio frequency system 230 comprising a multiplexer according to one embodiment. As shown, the radio frequency system includes an antenna 231, an antenna switch 232, an antenna plexer 233 connected between the antenna 231 and the antenna switch 232, at least one duplexer 234, a receive switch 235, a transmit switch 236, a low-noise amplifier 237, and a power amplifier 238. The antenna plexer 233 may include one or more switchable acoustic wave filters according to any suitable principles and advantages disclosed herein. The antenna plexer 231 may be electrically connected to the antenna 231 at an antenna port. The duplexer 234 may include one or more switchable acoustic wave filters according to any suitable principles and advantages disclosed herein.

[0118] In the radio frequency system 230, the antenna 231 can transmit and receive RF signals. The antennaplexer 233 can provide frequency-domain multiplexing to signals propagating between the antenna 231 and the radio frequency signal path. One such radio frequency signal path includes the antenna switch 232. The antenna switch 232 can selectively and electrically connect a multiplexer or a standalone filter to the antennaplexer 233. As shown in the figure, the antenna switch 232 can selectively and electrically connect a duplexer 234 to the antennaplexer 233. The duplexer 234 includes a receive filter, which is configured to filter the radio frequency signal received by the antenna 231 and to feed the filtered radio frequency signal to a low-noise amplifier 237 via the receive switch 236. The low-noise amplifier 237 can amplify this filtered radio frequency signal. The duplexer 234 also includes a transmit filter, which is configured to filter the radio frequency signal generated by the power amplifier 238 for transmission by the antenna 231. The power amplifier 238 can amplify radio frequency signals. The transmit switch 236 can connect the power amplifier 238 to the transmit filter of the duplexer 234.

[0119] The switchable elastic wave filter disclosed herein can be implemented in a wireless communication device. Figure 24 is a schematic block diagram of a wireless communication device 240 including a switchable elastic wave filter according to one embodiment. The wireless communication device 240 may be a portable device. The wireless communication device 240 may be any suitable wireless communication device. For example, the wireless communication device 240 may be a mobile phone such as a smartphone. As shown in the figure, the wireless communication device 240 includes a baseband system 241, a transceiver 242, a front-end system 243, one or more antennas 244, a power management system 245, a memory 246, a user interface 247, and a battery 248.

[0120] The wireless communication device 240 can be used to communicate using a wide variety of communication technologies, including but not limited to 2G, 3G, 4G (LTE, LTE Advanced, and LTE Advanced Pro), 5G NR, WLAN (e.g., WiFi), WPAN (e.g., Bluetooth® and / or ZigBee®), WMAN (e.g., WiMAX), and / or GPS technology.

[0121] The transceiver 242 generates an RF signal for transmission and processes the incoming RF signal received from the antenna 244. Various functions associated with the transmission and reception of RF signals can be achieved by one or more components, collectively represented as the transceiver 242 in Figure 24. In one example, a separate component (e.g., a separate circuit or die) may be provided to handle a predetermined type of RF signal.

[0122] The front-end system 243 assists in conditioning the signals supplied to and / or received from antenna 804. In the illustrated embodiment, the front-end system 243 includes an antenna tuning circuit 250, a plurality of power amplifiers (PAs) 251, a plurality of low-noise amplifiers (LNAs) 252, a plurality of filters 253, a plurality of switches 254, and a signal splitting / coupling circuit 255. However, other implementations are possible. The filter 253 may include one or more switchable acoustic wave filters following any suitable principles and advantages disclosed herein.

[0123] The front-end system 243 can provide a certain number of functions, including, but not limited to, amplification of signals for transmission, amplification of received signals, filtering of signals, switching between different bandwidths, switching between different power modes, switching between transmit and receive modes, duplexing of signals, multiplexing of signals, or any appropriate combination thereof.

[0124] In a given implementation example, the wireless communication device 240 supports carrier aggregation, providing flexibility to increase the peak data rate. Carrier aggregation can be used with both frequency-division duplexing (FDD) and / or time-division duplexing (TDD), and may be used to aggregate multiple carriers and / or channels. Carrier aggregation includes continuous aggregation, in which continuous carriers are aggregated within the same operating frequency band. Carrier aggregation may be discontinuous and may include carriers whose frequencies are separated within a common band or different bands.

[0125] The multiple antennas 244 may include antennas used for a wide variety of types of communication. For example, antennas 244 may include antennas for transmitting and / or receiving signals associated with a wide variety of frequencies and communication standards.

[0126] In a given implementation example, antenna 244 supports MIMO communication and / or switched diversity communication. For example, MIMO communication uses multiple antennas to communicate multiplexed data streams over a single radio frequency channel. MIMO communication benefits from a high signal-to-noise ratio, improved coding, and / or reduced signal interference due to the spatial multiplexing of the radio environment. Switched diversity refers to communication in which a specific antenna is selected to operate at a particular time. For example, a switch can be used to select a specific antenna from a group of antennas based on various factors such as the observed bit error rate and / or signal strength index.

[0127] The wireless communication device 240 may operate with beamforming in a given implementation. For example, the front-end system 243 may include an amplifier with controllable gain and a phase shifter with controllable phase to provide beamforming and directivity for transmitting and / or receiving signals using antenna 244. For example, in the context of signal transmission, the amplitude and phase of the transmit signal supplied to antenna 244 are controlled so that the signal radiated from antenna 244 is coupled using constructive and destructive interference, resulting in an aggregated transmit signal exhibiting beam-like quality with strong signal intensity propagating in a given direction. In the context of signal reception, the amplitude and phase are controlled so that more signal energy is received when the signal arrives at antenna 244 from a particular direction. In a given implementation, antenna 244 includes one or more arrays of antenna elements to enhance beamforming.

[0128] The baseband system 241 is coupled to a user interface 247 that facilitates the processing of various user input / output (I / O) such as voice and data. The baseband system 241 provides a digital representation of the transmit signal to the transceiver 242, which processes this to generate the RF signal for transmission. The baseband system 241 also processes the digital representation of the receive signal provided by the transceiver 242. As shown in Figure 24, the baseband system 241 is coupled to a memory 246 to facilitate the operation of the wireless communication device 240.

[0129] Memory 246 can be used for a wide variety of purposes, such as storing data and / or instructions, in order to facilitate the operation of the wireless communication device 240 and / or to provide storage for user information.

[0130] The power management system 245 provides a certain number of power management functions for the wireless communication device 240. In a given implementation example, the power management system 245 includes a PA supply control circuit that controls the supply voltage of a plurality of power amplifiers 251. For example, the power management system 245 may be configured to change the supply voltage supplied to one or more of the plurality of power amplifiers 251 in order to improve efficiency such as power added efficiency (PAE).

[0131] As shown in Figure 24, the power management system 245 receives the battery voltage from the battery 248. The battery 248 may be any suitable battery for use in the wireless communication device 240, including, for example, a lithium-ion battery.

[0132] Any of the embodiments described above can be implemented in connection with a portable device such as a cellular handset. The principles and advantages of these embodiments can be used for any system or device, such as any uplink wireless communication device, that can benefit from any of the embodiments described herein. The teachings herein are applicable to a variety of systems. Although this disclosure includes exemplary embodiments, the teachings described herein can be applied to a variety of structures. Any of the principles and advantages described herein can be implemented in connection with an RF circuit configured to process signals in a frequency range of about 30 kHz to 300 GHz, for example, in a frequency range of about 400 MHz to 8.5 GHz, or a frequency range of about 400 MHz to 5 GHz.

[0133] Aspects of this disclosure can be implemented in various electronic devices. Examples of child devices may include, but are not limited to, consumer electronic products, components of consumer electronic products such as packaged radio frequency modules, uplink wireless communication devices, wireless communication infrastructure, and electronic test equipment. Examples of electronic devices may include, but are not limited to, portable telephones such as smartphones, wearable computing devices such as smartwatches or earpieces, telephones, televisions, computer monitors, computers, modems, handheld computers, laptop computers, tablet computers, microwave ovens, refrigerators, automotive electronic systems such as automotive electronic systems, robots such as industrial robots, Internet of Things devices, stereo systems, digital music players, radios, cameras such as digital cameras, portable memory chips, household appliances such as washing machines or dryers, peripheral devices, wristwatches, and clocks. Furthermore, electronic devices may also include unfinished products.

[0134] Unless the context explicitly indicates otherwise, throughout the specification and claims, terms such as “includes,” “equip,” and so on should generally be interpreted in a comprehensive sense, the opposite of an exclusive or exhaustive sense, i.e., “includes but not limited to.” Unless specifically stated or understood otherwise in the context in which they are used, conditional language used herein, in particular, such as “can,” “may,” “may,” “for example,” and “like,” is generally intended to mean that a given embodiment includes a given feature, element, and / or state, while other embodiments do not. The term “combined,” as used herein, refers to two or more elements that can be directly connected or connected via one or more intermediate elements. Similarly, the term “connected,” as used herein, refers to two or more elements that can be directly connected or connected via one or more intermediate elements. In addition, where used herein, the terms “here,” “above,” “below,” and similar terms refer to the entire application and not to any particular part of the application. Where the context allows, the terms used in the detailed explanations above, which use singular or plural numbers, may also include singular or plural numbers.

[0135] While certain embodiments have been described, these embodiments are presented only as examples and are not intended to limit the scope of this disclosure. In fact, the novel resonators, multiplexers, devices, modules, wireless communication devices, apparatus, methods, and systems described herein can be embodied in a variety of other forms. Furthermore, various omissions, substitutions, and modifications in the forms of resonators, filters, multiplexers, devices, modules, wireless communication devices, apparatus, methods, and systems described herein can be made without departing from the essence of this disclosure. For example, while blocks are presented in a given arrangement, alternative embodiments may perform similar functions with different components and / or circuit topologies, and some blocks may be deleted, moved, added, subdivided, combined, and / or modified. Each of these blocks may be implemented in a variety of different forms. Any suitable combination of elements and / or functions of the various embodiments described above can be combined to give further embodiments. The appended claims and their equivalents are intended to cover such forms or modifications that fall within the scope and essence of this disclosure.

Claims

1. A multiplexer equipped with a switchable acoustic wave filter, A first filter configured to receive radio frequency signals, The second filter connected to the first filter and Includes, The first filter described above is a band-stop filter having a stopband, The first filter includes one or more elastic wave resonators, a plurality of switchable elastic wave resonators, and a switch that can be configured to be in at least a first state and a second state. The switch is configured to select a first subset of the plurality of switchable elastic wave resonators in the first state, select a second subset of the plurality of switchable elastic wave resonators in the second state, and filter the radio frequency signal by using at least one or more of the elastic wave resonators together in both the first and second states. A multiplexer wherein the frequency range of the stopband in the second state is narrower than the frequency range of the stopband in the first state, and is included in the frequency range of the stopband in the first state.

2. The multiplexer according to claim 1, wherein the switchable elastic wave resonator includes a series resonator.

3. The multiplexer according to claim 1, wherein the switchable elastic wave resonator includes a shunt resonator.

4. The band edge of the stopband of the first filter and the band edge of the passband of the second filter have closer frequencies in the first state of the switch than in the second state of the switch. The multiplexer according to claim 1, wherein the first state is associated with the second filter being inactive.

5. The multiplexer according to claim 1, wherein the second filter includes a second switch and a second switchable elastic wave resonator.

6. The first filter is configured to move the band edge of the frequency response of the first filter by toggling the switch between a first state and a second state. The multiplexer according to claim 5, wherein the second filter is configured to move the band edge of the frequency response of the second filter by the second switch.

7. The system further includes an inductor-capacitor circuit coupled between both the first filter and the second filter and the antenna node of the multiplexer, The multiplexer according to claim 5, wherein the inductor-capacitor circuit is configured to attenuate harmonics generated by the switch.

8. The multiplexer according to claim 1, wherein the second filter is a band-pass filter.

9. The multiplexer according to claim 1, wherein the first filter includes a second switch and a second switchable elastic wave resonator.

10. The first and second filters are configured to filter radio frequency signals associated with different frequency bands, The multiplexer according to claim 1, wherein the different frequency bands include a wireless local area network band and a cellular band.

11. The multiplexer according to claim 1, wherein the first filter and the second filter each have a band edge that is within 5 megahertz of each other.

12. The first subset of the above consists of a first switchable elastic wave resonator, The multiplexer according to claim 1, wherein the second subset comprises a second switchable elastic wave resonator.

13. The multiplexer according to claim 1, wherein the first filter has one switch loss.

14. A wireless communication device, Antenna switch and Antenna and, An antenna plexer including a first filter and a second filter coupled to the first filter Includes, The first filter is a band-blocking filter in the signal path between the antenna switch and the antenna. The first filter is configured to receive radio frequency signals, The first filter includes one or more elastic wave resonators, a plurality of switchable elastic wave resonators, and a switch that can be configured to be in at least a first state and a second state. The switch is configured to select a first subset of the plurality of switchable elastic wave resonators in the first state, select a second subset of the plurality of switchable elastic wave resonators in the second state, and filter the radio frequency signal by using at least one or more of the elastic wave resonators together in both the first and second states. A wireless communication device wherein the frequency range of the stopband of the band-stop filter in the second state is narrower than the frequency range of the stopband in the first state, and is included in the frequency range of the stopband in the first state.

15. A switchable filter, One or more elastic wave resonators, Multiple switchable elastic wave resonators, A switch that can be configured to be in at least a first state and a second state, Includes, The switch is configured to select a first subset of the plurality of switchable elastic wave resonators in the first state, select a second subset of the plurality of switchable elastic wave resonators in the second state, and filter radio frequency signals by using at least one or more of the elastic wave resonators together in both the first and second states. The switchable filter is a band-stop filter having a stopband, A switchable filter wherein the frequency range of the stopband in the second state is narrower than the frequency range of the stopband in the first state, and is included in the frequency range of the stopband in the first state.

16. The stopband of the first filter is associated with the operating band. The multiplexer according to claim 1, wherein the second filter is a band-pass filter having a passband corresponding to the operating bandwidth.

17. The multiplexer according to claim 16, wherein the operating bandwidth is the Wi-Fi operating bandwidth.

18. The second filter is a band-pass filter having a passband, The multiplexer according to claim 8, wherein the passband covers a smaller frequency range in the second state compared to the first state.

19. The stopband of the first filter is associated with the operating band. The wireless communication device according to claim 14, wherein the second filter is a band-pass filter having a passband corresponding to the operating bandwidth.

20. The stopband of the first filter is associated with the Wi-Fi operating band. The wireless communication device according to claim 14, wherein the second filter is a band-pass filter having a passband corresponding to the Wi-Fi operating band.

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