Hybrid acoustic inductance-capacitance filter cascaded with inductance-capacitance filter

Abstract

Aspects of the application relate to a hybrid acoustic LC filter cascaded with a non-acoustic LC filter. The hybrid acoustic filter can filter a radio frequency signal. The hybrid acoustic LC filter can include an acoustic resonator, an inductor, and a capacitor. The inductor and the capacitor can be external to the acoustic resonator wafer. The non-acoustic LC filter includes an LC circuit. Related multiplexers, wireless communication devices, and methods are disclosed.

Description

[0001] Cross Reference to Related Applications

[0002] Any and all applications identified in the Application Data Sheet as having been filed in this or any foreign or national stage as a continuation, continuation-in-part, divisional, or continuation of an application are hereby incorporated by reference under 37 CFR § 1.57. This application is a continuation-in-part of U.S. Patent Application No. 16 / 182, 1 17, filed November 1 1, 2018, which claims priority to U.S. Provisional Patent Application No. 62 / 700, 142, filed July 18, 2018, entitled "HYBRID ACOUSTIC LC FILTER CASCADED WITH LC FILTER," U.S. Provisional Patent Application No. 62 / 700, 148, filed July 18, 2018, entitled "PARALLEL HYBRID ACOUSTIC PASSIVE FILTER," and U.S. Provisional Patent Application No. 62 / 700, 146, filed July 18, 2018, entitled "HYBRID ACOUSTIC LC FILTER WITH HARMONIC DEPRESSION," under 35 U.S.C. § 1 19(e). The disclosure of each of these priority applications is hereby fully incorporated by reference herein in its entirety. TECHNICAL FIELD

[0003] Embodiments of the present application relate to a hybrid acoustic LC (inductor-capacitor) filter. BACKGROUND

[0004] Acoustic wave filters can include a plurality of acoustic resonators arranged to filter a radio frequency signal. The plurality of acoustic resonators can be arranged as a ladder filter to filter the radio frequency signal. Example acoustic wave filters include surface acoustic wave (SAW) filters and bulk acoustic wave (BAW) filters. Acoustic wave filters can be implemented in radio frequency electronic systems. For example, filters in a radio frequency front end of a mobile phone can include acoustic wave filters.

[0005] LC filters include at least an inductor and a capacitor. LC filters are non-acoustic filters that include passive components. LC filters can filter a radio frequency signal.

[0006] Filtering radio frequency signals at relatively high frequencies and meeting strict filter specifications can be difficult. Accordingly, improved filters are desired to filter signals at relatively high frequencies and meet performance specifications. SUMMARY

[0007] Each of the new inventions described in the claims has several aspects, no single aspect is solely responsible for its desirable attributes. Without limiting the scope of the claims, some prominent features of the application will now be briefly described.

[0008] An aspect of the application is a cascaded filter for radio frequency filtering. The cascaded filter includes a hybrid acoustic LC filter and a non-acoustic LC filter cascaded with the hybrid acoustic LC filter. The hybrid acoustic LC filter is configured to filter a radio frequency signal. The hybrid acoustic LC filter includes a first acoustic resonator on an acoustic resonator die, a second acoustic resonator, a capacitor external to the acoustic resonator die, and an inductor external to the acoustic resonator die. The non-acoustic LC filter includes an LC circuit.

[0009] The hybrid acoustic LC filter can further include a second inductor in parallel with the second acoustic resonator, wherein the second acoustic resonator is arranged as a shunt resonator in series with the inductor.

[0010] The first acoustic resonator and the second acoustic resonator can be shunt resonators. The capacitor and the inductor can be arranged as an LC tank coupled between the first acoustic resonator and the second acoustic resonator.

[0011] The first acoustic resonator can be coupled to a node in a signal path between the LC circuit and both the inductor and the capacitor.

[0012] The first acoustic resonator and the second acoustic resonator can be bulk acoustic wave resonators. For example, the first acoustic resonator and the second acoustic resonator can be film bulk acoustic resonators.

[0013] The LC circuit of the non-acoustic LC filter can include an integrated passive device on an integrated passive device die. The inductor of the hybrid acoustic LC filter can be a surface mount inductor. The inductor of the hybrid acoustic LC filter can include a conductive trace of a substrate. The integrated passive device can include an LC shunt circuit and a series LC resonant circuit.

[0014] The LC circuit of the non-acoustic LC filter can include a series LC resonant circuit and an LC shunt circuit. The series LC resonant circuit can include a parallel LC circuit. The LC shunt circuit can include a series LC circuit. The LC circuit of the non-acoustic LC filter can further include a second shunt series LC circuit.

[0015] A passband of the cascaded filter can be set by a non-acoustic LC filter. The first acoustic resonator can be arranged to provide rejection in a frequency band outside the passband. A lower limit of the passband can be at least 3 gigahertz. The passband can span at least 3.3 gigahertz to 4.2 gigahertz.

[0016] Another aspect of the application is a multiplexer comprising a first filter coupled to a common node and a second filter coupled to the common node. The first filter is configured to filter a radio frequency signal. The first filter comprises a hybrid acoustic LC filter and a non-acoustic LC filter cascaded with the hybrid acoustic LC filter. The hybrid acoustic LC filter comprises a first acoustic resonator on an acoustic resonator wafer, a second acoustic resonator, a capacitor external to the acoustic resonator wafer, and an inductor external to the acoustic resonator wafer.

[0017] The multiplexer can further comprise a third filter coupled to the common node. The second filter can comprise a second hybrid acoustic LC filter. The second filter can comprise a second non-acoustic LC filter.

[0018] Another aspect of the application is a wireless communication device comprising an antenna and a radio frequency front end in communication with the antenna. The radio frequency front end comprises a filter configured to filter a radio frequency signal for transmission via the antenna. The filter comprises a hybrid acoustic LC filter and a non-acoustic LC filter cascaded with the hybrid acoustic LC filter. The hybrid acoustic LC filter comprises an acoustic resonator on an acoustic resonator wafer, a capacitor external to the acoustic resonator wafer, and an inductor external to the acoustic resonator wafer.

[0019] The wireless communication device can be a mobile phone.

[0020] Another aspect of the application is a cascaded filter circuit for radio frequency filtering comprising a hybrid acoustic LC filter, a non-acoustic LC filter comprising an LC circuit, and a switch configured to selectively couple the hybrid acoustic LC filter and the non-acoustic LC filter. The hybrid acoustic LC filter is configured to filter a radio frequency signal. The hybrid acoustic LC filter comprises an acoustic resonator on an acoustic resonator wafer, a capacitor external to the acoustic resonator wafer, and an inductor external to the acoustic resonator wafer.

[0021] The cascaded filter circuit can further comprise a second non-acoustic LC filter, wherein the switch is configured to couple the hybrid acoustic LC filter and the non-acoustic LC filter in a first state, and wherein the switch is configured to couple the hybrid acoustic LC filter and the second non-acoustic LC filter in a second state. The non-acoustic LC filter can be a transmit filter, and the second non-acoustic LC filter can be a receive filter.

[0022] The cascaded filter circuit can further include a second hybrid acoustic LC filter, wherein the switch is configured to couple the hybrid acoustic LC filter and the non-acoustic LC filter in the first state, and wherein the switch is configured to couple the second hybrid acoustic LC filter and the non-acoustic LC filter in the second state.

[0023] The hybrid acoustic LC filter can further include a second inductor in parallel with the acoustic resonator, wherein the acoustic resonator is arranged as a shunt resonator with the inductor.

[0024] The hybrid acoustic LC filter can further include a second acoustic resonator. The first acoustic resonator and the second acoustic resonator can be shunt resonators. The capacitor and the inductor can be arranged as an LC tank between the acoustic resonator and the second acoustic resonator. The hybrid acoustic LC filter can further include a second inductor in series with the first acoustic resonator and a third inductor in series with the second acoustic resonator.

[0025] The acoustic resonator can be a bulk acoustic wave resonator.

[0026] The LC circuit of the non-acoustic LC filter can include an integrated passive device of an integrated passive device wafer. The inductor of the hybrid acoustic LC filter can be a surface mount inductor. The inductor of the hybrid acoustic LC filter can include a conductive trace of a substrate.

[0027] A passband of the cascaded filter including the non-acoustic LC filter and the hybrid acoustic LC filter can be set by the non-acoustic LC filter. A lower limit of the passband can be at least 3 gigahertz.

[0028] Another aspect of the application is a method of filtering a radio frequency signal. The method includes coupling a hybrid acoustic LC filter and a non-acoustic LC filter with a switch. The hybrid acoustic LC filter includes an acoustic resonator on an acoustic resonator wafer, a capacitor external to the acoustic resonator wafer, and an inductor external to the acoustic resonator wafer. The method further includes filtering the radio frequency signal when the hybrid acoustic LC filter and the non-acoustic filter are coupled together.

[0029] The method can further include decoupling the hybrid acoustic LC filter from the non-acoustic LC filter with the switch, and coupling the hybrid acoustic LC filter and a second non-acoustic LC filter with the switch. The method can further include providing the radio frequency signal to the non-acoustic LC filter with a power amplifier, and amplifying a filtered signal provided by the second non-acoustic filter with a low noise amplifier.

[0030] The filtering can include providing a rejection outside a passband of a filter including the hybrid acoustic LC filter and a non-acoustic LC filter using an acoustic resonator of the hybrid acoustic LC filter.

[0031] The radio frequency signal can have a frequency in a range from 3 gigahertz to 5 gigahertz.

[0032] Another aspect of the application is a wireless communication device including an antenna and a radio frequency front end in communication with the antenna. The radio frequency front end includes a filter configured to filter a radio frequency signal for transmission via the antenna. The filter includes a hybrid acoustic LC filter, a non-acoustic LC filter, and a switch configured to selectively couple the hybrid acoustic LC filter and the non-acoustic LC filter. The hybrid acoustic LC filter includes an acoustic resonator on an acoustic resonator wafer and an LC component external to the acoustic resonator wafer.

[0033] The wireless communication device can be a mobile phone.

[0034] Another aspect of the application is a parallel hybrid acoustic passive filter including a first sub-filter and a second sub-filter coupled in parallel with the first sub-filter. The first sub-filter includes a first acoustic resonator and a first non-acoustic passive component. The second sub-filter includes a second acoustic resonator and a second non-acoustic passive component. The first sub-filter and the second sub-filter are together arranged to filter a radio frequency signal.

[0035] The first sub-filter and the second sub-filter can be together arranged as a bandpass filter having a passband. A frequency response of the parallel hybrid acoustic passive filter can have a first sub-passband corresponding to the first sub-filter, a second sub-passband corresponding to the second sub-filter, and a notch at a notch frequency between the first sub-passband and the second sub-passband.

[0036] The first sub-filter and the second sub-filter can be together arranged as a bandstop filter having a stopband. The bandstop filter can have a notch in the stopband.

[0037] The first sub-filter can include a bulk acoustic wave resonator including the acoustic resonator.

[0038] The first non-acoustic passive component can include a first inductor and a second inductor, where the first inductor is in parallel with the acoustic resonator, and where the acoustic resonator is arranged as a shunt resonator with the second inductor.

[0039] The first sub-filter can further include an additional acoustic resonator, where the first acoustic resonator and the additional acoustic resonator are shunt resonators, and where the first non-acoustic passive component includes a capacitor and an inductor arranged as an LC tank coupled between the first acoustic resonator and the additional acoustic resonator.

[0040] The second non-acoustic passive component can include an integrated passive device.

[0041] The first sub-filter and the second sub-filter can have different passbands. A lower limit of the passband of the parallel hybrid acoustic passive filter can be at least 2 gigahertz.

[0042] Another aspect of the application is a multiplexer having a parallel hybrid acoustic passive filter. The multiplexer includes a first filter coupled to a common node and a second filter coupled to the common node. The first filter is configured to filter a radio frequency signal. The first filter includes a first sub-filter in parallel with a second sub-filter. The first sub-filter includes a first acoustic resonator and a first non-acoustic passive component. The second sub-filter includes a second acoustic resonator and a second non-acoustic passive component.

[0043] The first filter can be a bandpass filter. A frequency response of the first filter can have a first sub-passband corresponding to the first sub-filter, a second sub-passband corresponding to the second sub-filter, and a notch at a notch frequency between the first sub-passband and the second sub-passband. The second filter can be a bandstop filter.

[0044] The first filter can be a bandstop filter having a stopband and a notch in the stopband.

[0045] The second filter can include another acoustic resonator and another non-acoustic passive component.

[0046] The first filter can have a first passband, the second filter can have a second passband, and the first passband can have a lower edge at a higher frequency than an upper edge of the second passband.

[0047] The multiplexer can further include a third filter coupled to the common node.

[0048] The multiplexer can further include a shared filter in series between the first filter and the common node, wherein the shared filter is also in series between the second filter and the common node. The shared filter can be a high pass filter.

[0049] Another aspect of the application is a wireless communication device including a radio frequency front end and an antenna in communication with the radio frequency front end. The radio frequency front end includes a filter configured to filter a radio frequency signal. The filter includes a first sub-filter in parallel with a second sub-filter. The first sub-filter includes a first acoustic resonator and a first non-acoustic passive component. The second sub-filter includes a second acoustic resonator and a second non-acoustic passive component.

[0050] Another aspect of the application is a multiplexer having a hybrid acoustic passive filter. The multiplexer includes a plurality of filters configured to filter respective radio frequency signals, a shared filter coupled between each filter of the plurality of filters and a common node, and a radio frequency filter coupled to the common node. Each filter of the plurality of filters has a different passband. At least a first filter of the plurality of filters includes a plurality of acoustic resonators and a non-acoustic passive component.

[0051] The plurality of filters can include a first filter, a second filter, and a third filter. The first filter can be a first bandpass filter having a first passband. The second filter can be a second bandpass filter having a second passband. The third filter can be a bandstop filter having a stopband that includes the first passband and the second passband.

[0052] The shared filter can be a high pass filter. The radio frequency filter can be a low pass filter.

[0053] The shared filter can be a non-acoustic LC filter. The shared filter can include a second acoustic resonator and an LC component.

[0054] The non-acoustic passive component can include an inductor arranged in parallel with a first acoustic resonator of the plurality of acoustic resonators.

[0055] The acoustic resonators can be implemented on an acoustic resonator wafer. The non-acoustic passive component can include an inductor external to the acoustic resonator wafer and a capacitor external to the acoustic resonator wafer.

[0056] A second filter of the plurality of filters can include a plurality of second acoustic resonators and a second non-acoustic passive component. The first filter can have a first passband and the second filter can have a second passband. Both the first passband and the second passband can be within a frequency range from 2 gigahertz to 5 gigahertz. Both the first passband and the second passband can be within a frequency range from 2 gigahertz to 3 gigahertz.

[0057] The multiplexer can be arranged as a quadplexer.

[0058] Another aspect of the application is a wireless communication device including an antenna and a multiplexer in communication with the antenna. The multiplexer includes a plurality of filters configured to filter respective radio frequency signals, a shared filter coupled between each filter of the plurality of filters and a common node, and a radio frequency filter coupled to the common node. The plurality of filters includes a first filter that includes a plurality of acoustic resonators and a non-acoustic passive component.

[0059] A second filter of the plurality of filters can include a plurality of second acoustic resonators and a second non-acoustic passive component. The wireless communication device can be configured to support carrier aggregation at a common node. The carrier aggregation can include a first carrier and a second carrier, where the first carrier is within a first passband of the first filter, and where the second carrier is outside of the first passband and a second passband of the second filter.

[0060] Another aspect of the application is a multiplexer having a hybrid acoustic passive filter. The multiplexer includes a plurality of filters including a first filter and a second filter having different radio frequency passbands, a shared high pass filter coupled between each filter of the plurality of filters and a common node, and a low pass filter coupled to the common node. The first filter includes a plurality of first acoustic resonators and a first LC circuit. The second filter includes a plurality of second acoustic resonators and a second LC circuit.

[0061] The plurality of filters can further include a band stop filter having a stop band that includes passbands of the first filter and the second filter.

[0062] Another aspect of the application is a hybrid acoustic LC filter having harmonic rejection. The hybrid acoustic LC filter includes a hybrid passive / acoustic filter configured to filter a radio frequency signal and a non-acoustic LC filter cascaded with the hybrid passive / acoustic filter. The hybrid passive / acoustic filter includes a plurality of acoustic resonators and a non-acoustic passive component. The non-acoustic LC filter is configured to reject a harmonic of the radio frequency signal.

[0063] The non-acoustic LC filter can be a notch filter. A frequency response of the notch filter can have a notch corresponding to a second harmonic of the radio frequency signal. The frequency response of the notch filter can have two notches corresponding to different harmonics of the radio frequency signal.

[0064] The non-acoustic LC filter can be a low pass filter.

[0065] The non-acoustic LC filter can include an integrated passive device wafer.

[0066] The plurality of acoustic resonators can include a plurality of bulk acoustic wave resonators.

[0067] The non-acoustic passive component can include a first inductor and a second inductor. The acoustic resonators can include a first shunt acoustic resonator arranged in series with the first inductor and in parallel with the second inductor.

[0068] The plurality of acoustic resonators can include a first shunt acoustic resonator and a second shunt acoustic resonator. The non-acoustic passive component can include an LC tank coupled between the first shunt acoustic resonator and the second shunt acoustic resonator.

[0069] Another aspect of the application is a multiplexer comprising a first filter configured to filter a radio frequency signal and a second filter coupled to the first filter at a common node. The first filter comprises a hybrid passive / acoustic filter and a non-acoustic LC filter cascaded with the hybrid passive / acoustic filter. The hybrid passive / acoustic filter comprises a plurality of acoustic resonators and a non-acoustic passive component. The non-acoustic LC filter is configured to suppress harmonics of the radio frequency signal.

[0070] The second filter can comprise a plurality of second acoustic resonators and a second non-acoustic passive component. The first filter can be an intermediate frequency band filter and the second filter can be a high frequency band filter. The multiplexer can further comprise a low frequency band filter coupled to the first filter and the second filter at the common node.

[0071] The non-acoustic LC filter can comprise an integrated passive device of an integrated passive device wafer.

[0072] The non-acoustic passive component can comprise a first inductor and a second inductor. The plurality of acoustic resonators can comprise a first shunt acoustic resonator arranged in series with the first inductor and in parallel with the second inductor.

[0073] The plurality of acoustic resonators can comprise a first shunt acoustic resonator and a second shunt acoustic resonator. The non-acoustic passive component can comprise an LC tank coupled between the first shunt acoustic resonator and the second shunt acoustic resonator.

[0074] The plurality of acoustic resonators can comprise bulk acoustic wave resonators.

[0075] Another aspect of the application is a wireless communication device comprising a radio frequency front end and an antenna in communication with the radio frequency front end. The radio frequency front end comprises a filter configured to filter a radio frequency signal. The filter comprises a hybrid passive / acoustic filter and an LC filter cascaded with the hybrid passive / acoustic filter. The hybrid passive / acoustic filter comprises a plurality of acoustic resonators and a non-acoustic passive component. The non-acoustic LC filter is configured to suppress harmonics of the radio frequency signal. The antenna is configured to transmit a filtered version of the radio frequency signal with the harmonics suppressed.

[0076] The wireless communication device can be configured as a mobile phone.

[0077] The wireless communication device can further comprise a baseband processor and a transceiver, wherein the transceiver is in communication with the radio frequency front end and is further in communication with the baseband processor.

[0078] For purposes of summarizing the application, certain aspects, advantages and novel features of the applications have been described herein. It is to be understood that not necessarily all such advantages can be achieved in accordance with any particular embodiment. Thus, various embodiments can be implemented or performed in any way that achieves like advantages to some extent. BRIEF DESCRIPTION OF DRAWINGS

[0079] Embodiments of the application will be described, by way of non-limiting examples, and with reference to the accompanying drawings.

[0080] FIG. 1A is a schematic block diagram of a cascaded filter including a hybrid acoustic LC filter and an LC filter, according to one embodiment.

[0081] FIG. 1B is a schematic block diagram of a radio frequency system including a cascaded filter in a signal path between a power amplifier and an antenna, according to one embodiment.

[0082] FIG. 1C is a schematic block diagram of a radio frequency system including a cascaded filter in a signal path between an antenna and a low noise amplifier, according to one embodiment.

[0083] FIG. 2A is a schematic block diagram of a cascaded filter circuit including a hybrid acoustic LC filter coupled to an LC filter by a switch, according to one embodiment.

[0084] FIG. 2B is a schematic block diagram of a cascaded filter circuit including an LC filter coupled to a hybrid acoustic LC filter by a switch, according to one embodiment.

[0085] FIG. 3A is a schematic block diagram of a radio frequency system having a cascaded filter circuit, according to one embodiment.

[0086] FIG. 3B is a schematic block diagram of a radio frequency system having a cascaded filter circuit, according to another embodiment.

[0087] FIG. 3C is a schematic block diagram of a radio frequency system having a cascaded filter circuit, according to another embodiment.

[0088] FIG. 4A is a schematic block diagram of a multiplexer including a cascaded filter and another filter, according to one embodiment.

[0089] FIG. 4B is a schematic block diagram of a multiplexer according to another embodiment, the multiplexer comprising a cascaded filter and another filter.

[0090] FIG. 5A is a schematic block diagram of a multiplexer according to one embodiment, the multiplexer comprising a cascaded filter and another filter coupled to a common node through a switch.

[0091] FIG. 5B is a schematic block diagram of a multiplexer according to another embodiment, the multiplexer comprising a cascaded filter and another filter coupled to a common node through a switch.

[0092] FIG. 6A is a schematic diagram of a cascaded filter according to one embodiment.

[0093] FIG. 6B is a plot of a frequency response of the cascaded filter of FIG. 6A

[0094] FIG. 7 is a schematic diagram of a cascaded filter according to another embodiment.

[0095] FIG. 8 is a schematic diagram of a cascaded filter according to another embodiment.

[0096] FIG. 9 is a schematic diagram of a cascaded filter according to another embodiment.

[0097] FIG. 10 is a schematic diagram of a cascaded filter according to another embodiment.

[0098] FIG. 11A is a schematic diagram of a hybrid resonator according to one embodiment.

[0099] FIG. 11B is a plot of a frequency response of the hybrid resonator of FIG. 11A

[0100] is a schematic diagram of a hybrid resonator according to another embodiment. FIG. 12

[0101] is a schematic block diagram of a hybrid shunt bandpass filter according to one embodiment. FIG. 13

[0102] is a schematic block diagram of a diplexer according to one embodiment, the diplexer comprising a hybrid shunt bandpass filter. FIG. 14

[0103] FIG. 15 ​​is a schematic block diagram of a triplexer according to an embodiment, the triplexer including a hybrid shunt bandpass filter.

[0104] FIG. 16 is a schematic block diagram of a triplexer according to an embodiment, the triplexer including a hybrid shunt bandpass filter.

[0105] FIG. 17 is a schematic block diagram of a quadplexer according to an embodiment, the quadplexer including a hybrid shunt bandpass filter.

[0106] FIG. 18 is a schematic diagram of a triplexer according to an embodiment, the triplexer including a hybrid shunt bandpass filter.

[0107] FIG. 19A shows FIG. 18 simulation results for the triplexer of

[0108] FIG. 19B shows FIG. 18 a graph of simulation results for the triplexer of compared to a prior design.

[0109] FIG. 20 is a schematic block diagram of a hybrid shunt bandstop filter according to an embodiment.

[0110] FIG. 21 is a schematic diagram of a hybrid shunt bandstop filter according to an embodiment.

[0111] FIG. 22 is FIG. 21 a graph of frequency response for the hybrid shunt bandstop filter of

[0112] FIG. 23A is a schematic block diagram of a radio frequency system according to an embodiment, the radio frequency system including a hybrid acoustic LC filter in cascade with a low pass filter.

[0113] FIG. 23B is a schematic block diagram of a radio frequency system according to an embodiment, the radio frequency system including a hybrid acoustic LC filter in cascade with a second harmonic trap filter.

[0114] FIG. 24A is a schematic diagram of an example low pass filter.

[0115] FIG. 24B is a schematic diagram of another example low pass filter.

[0116] FIG. 24C is a schematic diagram of an example second harmonic trap filter.

[0117] FIG. 24Dis a schematic diagram of an example harmonic notch filter.

[0118] FIG. 24E is a schematic diagram of an example second harmonic notch and low pass filter.

[0119] FIG. 25A is a schematic block diagram of a triplexer including a hybrid acoustic LC filter in cascade with a low pass filter according to one embodiment.

[0120] FIG. 25B is a schematic block diagram of a triplexer including a hybrid acoustic LC filter in cascade with a second harmonic notch filter according to one embodiment.

[0121] FIG. 26 is a schematic diagram of a radio frequency module having a transmit path including a filter according to one embodiment.

[0122] FIG. 27 is a schematic diagram of a radio frequency module having a receive path including a filter according to one embodiment.

[0123] FIG. 28 is a schematic diagram of a radio frequency module including a filter according to one embodiment.

[0124] FIG. 29 is a schematic diagram of a wireless communication device including a filter according to one embodiment.

[0125] FIG. 30 is a schematic diagram of a wireless communication device including a filter according to another embodiment. DETAILED DESCRIPTION

[0126] The following detailed description of some embodiments presents various descriptions of specific embodiments. However, the new inventions described herein can be practiced in a number of different manners, for example, as defined and covered by the claims. In this description, reference is made to the drawings, where like reference numerals can indicate like or functionally similar elements. It will be understood that the elements illustrated in the figures are not necessarily to scale. Furthermore, it will be understood that some embodiments can include more elements than are illustrated in a figure, and / or some elements not illustrated in the figures. Additionally, some embodiments can incorporate any suitable combination of features from two or more figures. The headings provided herein are for convenience only and do not necessarily affect the scope or meaning of the claims.

[0127] This application relates to filters including acoustic components and non-acoustic passive components. Certain embodiments relate to hybrid acoustic LC filters in cascade with LC filters. Such filters can achieve a relatively wide passband and also meet stringent out-of-band rejection specifications. Some embodiments relate to filters having acoustic components and non-acoustic passive components arranged in parallel with each other. Such filters can achieve a relatively wide bandwidth and high rejection at a stopband relatively close to the passband with no high loss in the passband. Embodiments disclosed herein relate to non-acoustic LC filters in cascade with hybrid passive / acoustic filters, where the non-acoustic LC filters are arranged to suppress harmonics of radio frequency signals provided by the hybrid passive / acoustic filters. Such filters can achieve a relatively high bandwidth and high rejection while suppressing self-generated harmonics. Any suitable combination of features of embodiments disclosed herein can be combined with each other. Two or more embodiments can be implemented together in various applications.

[0128] Hybrid acoustic LC filters in cascade with LC filters

[0129] With the development of fifth generation (5G) wireless communication technology, non-acoustic wideband ultra-high band (UHB) filter designs are facing difficulties in meeting new carrier aggregation specifications. New carrier aggregation often results in more intermodulation frequencies, which can degrade receiver side sensitivity. Therefore, carrier aggregation specifications can have more stringent intermodulation distortion (IMD) rejection specifications for filters.

[0130] LC bandpass filters, such as integrated passive device (IPD) bandpass filters, have the advantage of wide bandwidth and relatively good wide out-of-band rejection. However, LC bandpass filters do not have particularly sharp rejection at frequencies close to the passband. Compared to acoustic wave filters, non-acoustic passband filters have significantly worse rolling-off loss at the passband edge frequencies. This is generally undesirable when high rejection is desired for a stopband close to the passband.

[0131] Due to higher quality factor (Q) than LC resonators, acoustic resonator filters can provide higher rejection at frequencies close to the passband without high edge rolling-off loss, so passive non-acoustic filters can be cascaded with hybrid acoustic LC filters to achieve both wide bandwidth and sharp rejection at a stopband close to the passband.

[0132] To provide a carrier aggregation IMD rejection compatible filter with a relatively sharp rejection at frequencies relatively close to the passband of the filter, a hybrid acoustic LC filter can be implemented. The hybrid acoustic LC filter can be a wideband filter that includes one or more capacitors, one or more inductors, and one or more acoustic resonators. The hybrid acoustic LC filter can include a plurality of hybrid resonators that include an acoustic resonator, at least one inductor, and at least one capacitor.

[0133] The hybrid acoustic LC filter can be cascaded with an LC filter to provide a relatively low loss wide passband and also to provide a relatively sharp rejection at frequencies relatively close to the passband of the cascaded filter. The LC filter can include an integrated passive device (IPD) on an integrated passive device wafer. The hybrid acoustic LC filter can include one or more bulk acoustic wave resonators. The combination of bulk acoustic wave resonators and LC circuit elements in the cascaded filter can provide a relatively wide passband and also can meet relatively stringent out-of-band rejection specifications.

[0134] Aspects of the present application relate to a cascaded filter for filtering a radio frequency signal. The cascaded filter includes a hybrid acoustic LC filter and a non-acoustic LC filter cascaded with the hybrid acoustic LC filter. The hybrid acoustic LC filter includes a plurality of acoustic resonators, capacitors, and inductors. The non-acoustic LC filter includes an LC circuit.

[0135] The cascaded filters discussed herein can be implemented for various frequency bands including wireless frequency bands as long as acoustic resonators can be used. As an example, the cascaded filter can have a passband with a lower frequency limit of at least 2.5 gigahertz (GHz) or at least 3 GHz in certain applications. In certain applications, the cascaded filter can have a relatively high upper passband limit, such as about 4.5 GHz, about 6 GHz, about 8.5 GHz, or about 10 GHz. The cascaded filters discussed herein can be implemented in a power amplifier module, a diversity receive module, or any other appropriate radio frequency front end module. The cascaded filters discussed herein can meet the following design specifications: relatively low insertion loss (IL), relatively sharp frequency cutoff, and relatively strong suppression of intermodulation frequencies and harmonics.

[0136] FIG. 1Ais a schematic block diagram of a cascaded filter 10 according to an embodiment, the cascaded filter 10 including a hybrid acoustic LC filter 12 and an LC filter 14. The cascaded filter 10 has a first port RF1 and a second port RF2. The hybrid acoustic LC filter 12 and the LC filter 14 are arranged in series with each other between the first port RF1 and the second port RF2. In certain applications, a radio frequency signal can propagate from the first port RF1 to the second port RF2. In various applications, a radio frequency signal can propagate from the second port RF2 to the first port RF1.

[0137] The hybrid acoustic LC circuit 12 includes one or more acoustic resonators, one or more inductors, and one or more capacitors. The one or more acoustic resonators can be BAW resonators, such as film bulk acoustic resonators (FBARs). For example, BAW resonators can be more advantageous for filtering signals having higher frequencies, such as frequencies higher than 2.5 GHz. The one or more acoustic resonators can alternatively or additionally include any other suitable acoustic resonator, such as one or more surface acoustic wave (SAW) resonators, one or more boundary acoustic wave resonators, and / or one or more Lamb wave resonators. The hybrid acoustic LC filter 12 can include capacitors and inductors external to a wafer that includes the acoustic resonators. The hybrid acoustic LC filter 12 can be a ladder filter. In certain applications, the hybrid acoustic filter 12 can be a fixed filter. In some instances, a fixed filter can be implemented with lower complexity than a tunable filter. In certain applications, the hybrid acoustic LC filter 12 can be tunable. When the hybrid acoustic LC filter 12 is tunable, a notch and / or a stopband can be tunable.

[0138] The LC circuit 14 includes one or more inductors and one or more capacitors. The LC circuit 14 can include one or more IPDs, one or more surface mount components, one or more passive devices implemented on a package substrate, or any suitable combination thereof. Surface mount components can have higher quality factors and lower insertion loss than IPDs and passive devices implemented on a package substrate at some frequencies. The one or more capacitors can be explicit capacitors and / or parasitic capacitors. The LC circuit 14 can also implement impedance matching.

[0139] FIG. 1B is a schematic block diagram of a radio frequency (RF) system 15 according to an embodiment, the RF system 15 including the cascaded filter 10 in a signal path between a power amplifier 16 and an antenna 17. FIG. 1BThe cascaded filter 10 can be included in a transmit signal path. In certain applications, a first port RF1 of the cascaded filter 10 can be electrically coupled to an output of the power amplifier 16, and a second port RF2 of the cascaded filter 10 can be electrically coupled to the antenna 17. In some applications, the first port RF1 of the cascaded filter 10 can be electrically coupled to the antenna 17, and the second port RF2 of the cascaded filter 10 can be electrically coupled to an output of the power amplifier 16.

[0140] FIG. 1C is a schematic block diagram of an RF system 18 including the cascaded filter 10 in a signal path between the antenna 17 and a low noise amplifier 19, according to one embodiment. FIG. 1C The cascaded filter 10 can be included in a receive signal path. In certain applications, a first port RF1 of the cascaded filter 10 can be electrically coupled to an input of the low noise amplifier 19, and a second port RF2 of the cascaded filter 10 can be electrically coupled to the antenna 17. In some applications, the first port RF1 of the cascaded filter 10 can be electrically coupled to the antenna 17, and the second port RF2 of the cascaded filter 10 can be electrically coupled to an input of the low noise amplifier 19.

[0141] FIG. 2A is a schematic block diagram of a cascaded filter circuit 20 including the hybrid acoustic LC filter 12 coupled to LC filters 14A-14N by a switch 22, according to one embodiment. The cascaded filter circuit 20 can share the hybrid acoustic LC filter 12 among multiple LC circuits 14A-14N. The switch 22 can electrically connect the hybrid acoustic LC filter 12 in series with a selected LC circuit to implement a cascaded filter. The illustrated switch 22 is a multi-throw radio frequency switch. The switch 22 can electrically couple the hybrid acoustic LC filter 12 to a selected LC filter. The switch 22 can have any suitable number of throws, and the cascaded filter circuit 20 can have a corresponding number of LC filters 14A-14N. The illustrated LC filters 14A and 14N are each coupled to a corresponding port RF 21 and RF 2N In the cascaded filter circuit 20, the hybrid acoustic LC filter 12 can combine with a selected one or more of the LC filters 14A-14N to achieve a relatively sharp rejection at frequencies relatively close to a passband. In certain applications, the hybrid acoustic LC filter 12 can be tunable to tune the rejection at frequencies relatively close to a passband for a selected one or more of the LC filters 14A-14N electrically coupled thereto.

[0142] FIG. 2Bis a schematic block diagram of a cascaded filter circuit 25 according to one embodiment, which includes an LC filter 14 coupled to hybrid acoustic LC filters 12A and 12N by a switch 22. The cascaded filter circuit 20 can share the LC filter 14 among multiple hybrid acoustic LC circuits 12A through 12N. The switch 22 can electrically connect the LC filter 14 in series with a selected hybrid acoustic LC circuit to implement a cascaded filter. The illustrated switch 22 is a multi-throw radio frequency switch. The switch 22 can electrically couple the LC filter 14 to a selected hybrid acoustic LC filter. The switch 22 can have any suitable number of throws, and the cascaded filter circuit 25 can have a corresponding number of hybrid acoustic LC filters 12A through 12N. The illustrated hybrid acoustic LC filters 12A and 12N are each coupled to a corresponding port of the cascaded filter circuit 25. 11 and RF 1N .

[0143] FIG. 3A is a schematic block diagram of a radio frequency system 30A with a cascaded filter circuit according to one embodiment. The radio frequency system 30 is an example system in which the cascaded circuit 20 of FIG. 2A may be implemented. As shown, an antenna 32 is coupled to a hybrid acoustic LC filter 12, the switch 22 is a transmit / receive switch, and LC filters 14A and 14B are connected to a power amplifier 34 and a low noise amplifier 36, respectively. FIG. 2B The cascaded circuit 25 of may be implemented in a radio frequency system similar to the radio frequency system 30A.

[0144] FIG. 3B is a schematic block diagram of a radio frequency system 30B with a cascaded filter circuit according to another embodiment. FIG. 3B It is shown that the LC circuits 14A and 14B can be in different transmit paths with respective power amplifiers 34A and 34B. Thus, the hybrid acoustic LC filter 12 can be included in (a) a cascaded filter circuit with the LC filter 14A between the power amplifier 34A and the antenna 32 and (b) a cascaded filter circuit with the LC filter 14B between the power amplifier 34B and the antenna 32.

[0145] FIG. 3C is a schematic block diagram of a radio frequency system 30C with a cascaded filter circuit according to another embodiment. For example, the cascaded filter of the radio frequency system 30C can be implemented in a diversity receive application. FIG. 3CThe LC circuits 14A and 14B can be shown in different receive paths with corresponding low noise amplifiers 36A and 36B. Thus, the hybrid acoustic LC filter 12 can be included in (a) a cascaded filter circuit with the LC filter 14A between the low noise amplifier 36A and the antenna 32 and (b) a cascaded filter circuit with the LC filter 14B between the low noise amplifier 36B and the antenna 32.

[0146] FIG. 4A is a schematic block diagram of a multiplexer 40 including a cascaded filter and another filter according to one embodiment. The multiplexer 40 includes multiple filters coupled to a common node. As shown, the cascaded filter including the LC filter 14 and the hybrid acoustic LC filter 12 and the other filter 42 are coupled together at the common node. In the multiplexer 40, the LC filter 14 is coupled to the common node through the hybrid acoustic LC filter 12. The multiplexer 40 can be a diplexer with two filters, a triplexer with three filters, a quadplexer with four filters, etc. The other filter 42 can include any suitable number of filters. (The other filter 42 can include one or more LC filters (e.g., IPD filters), one or more acoustic filters, one or more hybrid acoustic LC filters, etc., or any suitable combination thereof.)

[0147] FIG. 4B is a schematic block diagram of a multiplexer 45 including a cascaded filter and another filter according to another embodiment. The multiplexer 45 is the same as the multiplexer 40 of FIG. 4A except that the hybrid acoustic LC filter 12 is coupled to the common node through the LC filter 14.

[0148] Multiple filters can be in communication with a common node, such as an antenna node, through a switch. FIG. 5A is a schematic diagram of a radio frequency system 50 including a cascaded filter and another filter 42 coupled to a common node through a switch 52. The cascaded filter, the other filter 42, and the switch 52 can enable switch-plexing. Switch-plexing can enable on-demand multiplexing.

[0149] FIG. 5B is a schematic block diagram of a radio frequency system 55 including a cascaded filter and another filter coupled to a common node through a switch according to another embodiment. The radio frequency system 55 is the same as the radio frequency system 50 of FIG. 5A except that the hybrid acoustic LC filter 12 and the LC filter 14 are arranged in a different order.

[0150] FIG. 6Ais a schematic diagram of a cascaded filter 60 according to an embodiment. The cascaded filter 60 can be a bandpass filter arranged to pass radio frequency signals having frequencies above 3 GHz, such as Band 42 signals and / or Band 43 signals and / or Band 48 signals. In such applications, the acoustic wave resonators of the filter 60 can be BAW resonators. The filter 60 can be used in 5thGeneration (5G) wireless system applications. 5G technology can be referred to as 5G New Radio (NR). The cascaded filter 60 includes a hybrid acoustic LC filter 62 cascaded with an LC filter 64. The hybrid acoustic LC filter 62 is an example of the hybrid acoustic LC filter 12. The LC filter 64 is an example of the LC filter 14.

[0151] The hybrid acoustic LC filter 62 includes acoustic resonators A61 and A62, inductors L601, L602, L603, L604, L605, and L606, and capacitors C601, C602, C603, and C604. The acoustic resonators A61 and A62 can be BAW resonators such as FBARs. In some instances, the acoustic resonators A61 and A62 can include SAW resonators, temperature compensated SAW (TCSAW) resonators, boundary acoustic wave resonators, Lamb wave resonators, or the like, or any suitable combination thereof. The inductors L601, L602, L603, L604, L605, and L606 and the capacitors C601, C602, C603, and C604 are LC / non-acoustic components. The LC / non-acoustic components of the hybrid acoustic LC filter 62 can be implemented external to a die that includes the acoustic resonators A61 and A62. The LC / non-acoustic components of the hybrid acoustic LC filter 62 can include one or more surface mount technology (SMT) inductors and / or capacitors. In some cases, the LC / non-acoustic components of the hybrid acoustic LC filter 62 can include one or more IPDs and / or one or more inductive traces on a package substrate.

[0152] As shown, the hybrid acoustic LC filter 62 includes a hybrid resonator structure in which the inductor L602 is in parallel with the acoustic resonator A62, in which the inductor L603 is in series with the inductor L602 and the acoustic resonator A62. Referring to the equivalent circuit diagram of FIG. 6B, the hybrid acoustic LC filter 62 includes a series resonant circuit 650 in which the inductor L603 is in series with the acoustic resonator A62, in which the inductor L602 is in parallel with the series resonant circuit 650. FIG. 11A and FIG. 11BFurther details are provided regarding this hybrid resonator structure. The illustrated LC filter 62 also includes LC tanks between the acoustic nodes at which acoustic resonators A61 and A62 are arranged in series with respective inductors L603 and L606 in the shunt circuit, where the LC tank includes a capacitor C604 and an inductor L605. Reference is made to FIG. 12 Further details are provided regarding this hybrid resonator structure.

[0153] LC filter 64 can be a bandpass filter. For example, LC filter 64 can be a band 42 / band 43 bandpass filter. LC filter 64 includes an IPD portion 65 on an IPD wafer, a package substrate portion 66 including traces on a package substrate, and an SMT portion 67 including SMT components. IPD portion 65 includes IPD capacitors C605, C606, C607, C608, C609, and C610, and IPD inductor L608. Package substrate portion 66 includes inductive traces arranged as inductors L609, L610, L611, and L612. SMT components 67 include SMT capacitors C611 and C612.

[0154] As shown, LC filter 64 includes a bridge capacitor, an LC resonant circuit, a coupling capacitor, and a series LC tank. First bridge capacitor C610 has a first end coupled to the series LC tank and a second end coupled to an input node of LC filter 64. The series LC tank includes capacitor C605 and inductor L608. First bridge capacitor C610 is in parallel with three coupling capacitors C606, C607, and C608.

[0155] The first LC resonant circuit is an LC shunt resonant circuit. As shown, the first LC resonant circuit includes a shunt inductor L611 in parallel with a series LC circuit including inductor L612 and capacitor C612. Second bridge capacitor C609 has a first end coupled to the series LC tank and a second end coupled to the first LC resonant circuit. Second bridge capacitor C609 is in parallel with two coupling capacitors C606 and C607. The second LC resonant circuit is an LC shunt resonant circuit. As shown, the second LC resonant circuit includes a shunt inductor L609 in parallel with a series LC circuit including inductor L610 and capacitor C611.

[0156] A first coupling capacitor C608 is coupled between an input of the filter and a node at which the first coupling capacitor C608 is coupled to the first LC resonant circuit and a second coupling capacitor C607. The second coupling capacitor C607 is coupled in series between the first coupling capacitor C608 and a third coupling capacitor C606. The second coupling capacitor C607 is also coupled between the first LC resonant circuit and a second LC resonant circuit. The third coupling capacitor C606 is coupled between the series LC tank and a node at which the third coupling capacitor C606 is coupled to the second LC resonant circuit and the second coupling capacitor C607. The illustrated series LC tank is a parallel LC circuit.

[0157] FIG. 6B is FIG. 6A a plot of the frequency response of the cascaded filter 60. The illustrated curve represents FIG. 6A the frequency response of the cascaded filter 60. The stepped line represents a design specification or filter mask. FIG. 6B the curve in FIG. 6A the frequency response of the cascaded filter 60 meets the design specification. As shown, the filter response has two nulls produced by the shunt acoustic resonators A61 and A62. The frequency response has a relatively sharp roll-off at the passband edges. FIG. 6A the non-acoustic LC filter 64 of FIG. 6A the cascaded filter 60 of

[0158] FIG. 6A the cascaded filter 60 of FIG. 7 to FIG. 10 is an example of a non-acoustic LC filter cascaded with a hybrid acoustic LC filter. The principles and advantageous aspects discussed herein can be implemented in various other filter topologies. Some example filter topologies are illustrated in FIG. 7 to FIG. 10The example filters shown illustrate filters for various applications and design specifications. Any suitable combination of the features of these filters can be implemented together with one another and / or in accordance with any other principles and advantageous aspects discussed herein.

[0159] FIG. 7 is a schematic diagram of a cascaded filter 70 according to another embodiment. The cascaded filter 70 includes a hybrid acoustic LC filter 72 cascaded with an LC filter 74. The hybrid acoustic LC filter 72 is an example of the hybrid acoustic LC filter 12. The LC filter 74 is an example of the LC filter 14. For example, the cascaded filter 70 can be a receive filter. In certain applications, the cascaded filter 70 can have a passband from 3.4 GHz to 3.7 GHz.

[0160] The hybrid acoustic LC filter 72 includes acoustic resonators A71, A72, A73, A74, A75, and A76; capacitors C701, C702, and C703; and inductors L701, L702, L703, L704, L705, L706, L707, L708, and L709. The acoustic resonators A71-A76 can be BAW resonators. The capacitors C701-C703 can be SMT capacitors. The inductors L701-L709 can include a combination of SMT inductors and conductive traces of a package substrate.

[0161] The LC filter 74 shown includes capacitors C704 and C705 and inductors L710 and L711. In certain embodiments, the LC filter 74 can be implemented with IPD capacitors and inductors on an IPD wafer. In some other embodiments, the LC filter 74 can be implemented with SMT capacitors and inductors on an IPD wafer.

[0162] FIG. 8 is a schematic diagram of a cascaded filter 80 according to another embodiment. The cascaded filter 80 includes a hybrid acoustic LC filter 82 cascaded with an LC filter 84. The hybrid acoustic LC filter 82 is an example of the hybrid acoustic LC filter 12. The LC filter 84 is an example of the LC filter 14. In one embodiment, the cascaded filter 80 can be a bandpass filter having a passband from about 3.3 GHz to 4.2 GHz. According to another embodiment, the cascaded filter can have a passband from 3.4 GHz to 3.7 GHz. For example, the cascaded filter 80 can be a receive filter.

[0163] The hybrid acoustic LC filter 82 includes acoustic resonators A81, A82, A83, A84, and A85; capacitors C801 and C802; and inductors L801, L802, L803, L804, L805, and L806. The acoustic resonators A81-A85 can be BAW resonators. The capacitors C801 and C802 can be SMT capacitors. The inductors L801-L805 can include a combination of SMT inductors and conductive traces of the package substrate. FIG. 11A and FIG. 11B The hybrid resonators including inductors L802 and L803 and acoustic resonators A81, A82, and A83 can function similarly to the hybrid resonators described with reference to FIG. 12 The hybrid ladder structure including inductors L802-L805, capacitor C802, and acoustic resonators A81-A85 can function similarly to the hybrid ladder structure described with reference to

[0164] The LC filter 84 shown includes capacitors C803, C804, C805, C806, and C807 and inductors L806, L807, L808, and L809. The LC filter 84 can include one or more IPDs, one or more SMT components, one or more conductive traces of the substrate, or any suitable combination thereof.

[0165] FIG. 9 is a schematic diagram of a cascaded filter 90 according to another embodiment. The cascaded filter 90 includes a hybrid acoustic LC filter 92 cascaded with an LC filter 94. The hybrid acoustic LC filter 92 is an example of the hybrid acoustic LC filter 12. The LC filter 94 is an example of the LC filter 14. In some embodiments, the cascaded filter 90 can include surface mount passive components in addition to shunt inductors coupled between acoustic resonators and ground, where such shunt inductors can be printed traces on the package substrate. As such, in such embodiments, the cascaded filter 90 does not include IPDs. In certain instances, the cascaded filter 90 can be a receive filter coupled between an antenna switch and a low noise amplifier. The cascaded filter 90 can improve insertion loss relative to previous designs. The cascaded filter 90 can be a receive filter.

[0166] The hybrid acoustic LC filter 92 includes acoustic resonators A91, A92, and A93; capacitors C901, C902, C903, and C904; and inductors L901, L902, L903, and L904. The acoustic resonators A91-A93 can be BAW resonators. The capacitors C901-C904 can be SMT capacitors. The inductors L901-L904 can include a combination of SMT inductors and conductive traces of the package substrate.

[0167] The illustrated LC filter 94 includes capacitors C903, C904, and C905 and inductors L905, L906, L907, and L908. The LC filter 94 can include one or more IPDs, one or more SMT components, one or more conductive traces of a substrate, or any suitable combination thereof. In one embodiment, the LC filter 94 is composed of SMT inductors and capacitors.

[0168] FIG. 10 is a schematic diagram of a cascaded filter according to another embodiment. The cascaded filter 100 includes a hybrid acoustic LC filter 102 cascaded with an LC filter 104. The hybrid acoustic LC filter 102 is an example of the hybrid acoustic LC filter 12. The LC filter 104 is an example of the LC filter 14. In certain embodiments, the cascaded filter 100 can include IPDs, surface mount passive components, inductive traces on a laminate material, and FBARs. In certain instances, the cascaded filter 100 can be a receive filter coupled between an antenna switch and a low noise amplifier. The cascaded filter 100 can be a bandpass filter having a passband from about 3.3 GHz to 4.2 GHz. In certain embodiments, the cascaded filter 100 is a receive filter.

[0169] The hybrid acoustic LC filter 102 includes acoustic resonators A101, A102, and A103; capacitors C1001 and C1002; and inductors L1001, L1002, L1003, L1004, L1005, and L1006. The acoustic resonators A101-A103 can be BAW resonators. The capacitors C1001 and C1002 can include SMT capacitors and / or IPD capacitors. The inductors L1001-L1006 can include one or more SMT inductors, one or more IPD inductors, one or more conductive traces of a package substrate, or any suitable combination thereof. In one embodiment, the inductors L1001-L1006 include at least SMT inductors, at least one IPD inductor, and at least one conductive trace of a package substrate.

[0170] The hybrid resonator including inductors L1002 and L1003 and acoustic resonator A102 can function similarly to the hybrid resonator described with reference to FIG. 11A and FIG. 11B The hybrid resonator including inductors L1005 and L1006 and acoustic resonator A103 can function similarly to the hybrid resonator described with reference to FIG. 11A and FIG. 11B The hybrid ladder structure including inductors L802-L806, capacitor C1002, and acoustic resonators A102-A103 can function similarly to the hybrid ladder structure described with reference to FIG. 12 ​

[0171] The illustrated LC filter 104 includes capacitors C1003, C1004, C1005, C1006, and C1007 and inductors L1007, L1008, L1009, and L1010. The LC filter 104 can include one or more IPDs, one or more SMT components, one or more conductive traces of a substrate, or any suitable combination thereof. In one embodiment, the LC filter 104 includes at least an SMT component, at least one IPD, and at least one conductive trace of a packaging substrate.

[0172] The hybrid acoustic LC filters discussed herein can include various hybrid resonators that include an acoustic resonator and a non-acoustic passive component. An example hybrid resonator will be discussed with reference to FIG. 11A to FIG. 12 These hybrid resonators can be implemented in association with any suitable embodiment discussed herein.

[0173] FIG. 11A is a schematic diagram of a hybrid resonator 110 according to one embodiment. The hybrid resonator 110 includes an acoustic resonator 112, a first inductor 114, and a second inductor 116. The acoustic resonator 112 is arranged as a shunt resonator. For example, the acoustic resonator 112 can be an FBAR. The acoustic resonator 112 can be any other suitable acoustic resonator. The acoustic resonator 112 is in parallel with the first inductor 114. The acoustic resonator 112 is in series with the second inductor 116. The combination of the inductors 114 and 116 with the acoustic resonator 112 can produce a pair of notches that have little noticeable effect on transmission loss relatively close to the passband. The notches can be in a range of about 1.1 GHz to 8.5 GHz from the lower or upper limit of the passband.

[0174] FIG. 11B is a graph of a frequency response of the hybrid resonator 110 of FIG. 11A The frequency response shows the pair of notches discussed with reference to FIG. 11A The frequency response also shows that the simulated hybrid resonator 110 does not introduce noticeable transmission loss.

[0175] FIG. 12is a schematic diagram of a hybrid resonator 120 according to another embodiment. The hybrid resonator 120 is a hybrid ladder structure. The hybrid resonator 120 includes a first series shunt circuit, an LC tank, and a second series shunt circuit. The first series shunt circuit includes a first acoustic resonator 122 and a first inductor 123. The second series shunt circuit includes a second acoustic resonator 124 and a second inductor 125. The LC tank includes a capacitor 126 in parallel with a third inductor 127. The hybrid resonator 120 includes an LC tank between acoustic nodes. This can provide both inter-resonator impedance matching and far-end notching in the frequency response of a filter including the hybrid resonator 120. The hybrid resonator 120 includes a hybrid ladder structure. For example, the hybrid resonator 120 can be used in a low-pass filter and / or a high-pass filter. The hybrid resonator 120 is a hybrid ladder topology.

[0176] Parallel hybrid acoustic passive filter

[0177] With the development of 5G wireless communication technology, new carrier aggregation (CA) specifications can specify more stringent intermodulation distortion (IMD) rejection for filters. Such new CA can involve more multiplexed filters than previous CA. To provide CA IMD rejection compatible filters with sharp rejection at frequencies close to the passband, an acoustic assisted filter can be designed with a hybrid resonator, such as a hybrid acoustic LC resonator, to provide relatively low loss, wide passband, and relatively sharp rejection at frequencies close to the passband. Acoustic resonators can generate harmonics when relatively high power is applied. Harmonics generated by surface acoustic wave devices or bulk acoustic wave devices can leak to higher frequency bands and / or have emissions that exceed standard specifications.

[0178] To provide CA compatible multiplexed filters with sharp rejection at edge band frequencies, hybrid acoustic LC wideband filters can be included in some or all of the passband arms. To reduce and / or minimize the use of filter acoustic dies and passive components, hybrid acoustic LC filters or integrated passive device (IPD) filters or passive low pass (LP) or high pass (HP) filters can be shared by two or more passband arms. Additionally, to provide specific sharp rejection in a high passband arm (e.g., in Wi-Fi 2.4 GHz) in a bandpass filter (BPF), a parallel hybrid acoustic LC filter can be included. In some examples, a parallel hybrid acoustic LC filter can be cascaded with another filter, such as a passive non-acoustic filter.

[0179] Disclosed are hybrid acoustic LC filters with parallel hybrid acoustic LC sub-filters. In one embodiment, a parallel acoustic LC filter includes a first sub-filter configured to filter a radio frequency signal and a second sub-filter coupled in parallel with the first sub-filter. The first sub-filter includes a first acoustic resonator and a first LC component. The second sub-filter includes a second acoustic resonator and a second LC component. The parallel hybrid acoustic LC filter can be implemented in a multiplexer including a plurality of filters coupled together at a common node. The parallel hybrid acoustic filter can implement any suitable principles and advantageous aspects of the acoustic LC circuits disclosed herein. As one example, the parallel hybrid acoustic LC filter can include a hybrid resonator 110 of FIG. 11A As yet another example, the parallel hybrid acoustic LC filter can include a hybrid ladder structure 120 of FIG. 12

[0180] The parallel hybrid acoustic LC filter can be a bandpass filter. The parallel hybrid acoustic LC filter can be a bandstop filter. The parallel hybrid acoustic LC filter can be in a high frequency band path. Such a filter can reduce and / or minimize design complexity. Additionally, in certain applications, such a filter can be implemented with fewer passive components and / or less physical area. The parallel hybrid passive filters discussed herein can meet design specifications for a high frequency band path, such as a desired rejection at a particular frequency (e.g., a Wi-Fi band). This can allow a high frequency band path to be shared by both a transmit path and a receive path.

[0181] The parallel hybrid acoustic LC filter can provide a relatively wide bandwidth as well as strong rejection at a particular frequency band. The parallel hybrid acoustic LC filter can include multiple hybrid filters in parallel with each other and arranged to provide strong rejection for another frequency band. As one example, a parallel band 40 and band 41 hybrid acoustic LC bandpass filter can provide a wide enough bandwidth for band 40 and band 41 signals while also providing strong rejection for the 2.4 GHz Wi-Fi band. In some embodiments, a passive non-acoustic filter can be cascaded with the parallel hybrid acoustic LC filter to achieve a wide bandwidth and sharp rejection in a high frequency band path. According to certain embodiments, a triplexer can be implemented by a parallel hybrid acoustic LC filter and two other filters coupled to a common node. For example, a triplexer for low band (LB) / mid band (MB) / high band (HB) can include a LB filter, a MB filter, and a HB filter implemented by a hybrid acoustic LC filter including a band 40 filter in parallel with a band 41 filter. Such a triplexer can effectively be used as a quadruplexer to benefit system level carrier aggregation applications.

[0182] FIG. 13 ​is a schematic block diagram of a hybrid shunt bandpass filter 130 according to an embodiment. The shunt hybrid bandpass filter 130 comprises a first bandpass filter 132 and a second bandpass filter 134 arranged in parallel to each other. The first bandpass filter 132 and the second bandpass filter 134 are arranged to filter a radio frequency signal. The first bandpass filter 132 is a hybrid acoustic passive filter comprising a first acoustic resonator and a first non-acoustic passive component. The first non-acoustic passive component can comprise at least an inductor and a capacitor. The second bandpass filter 134 can be a hybrid acoustic passive filter comprising a second acoustic resonator and a second non-acoustic passive component. The second non-acoustic passive component can comprise at least an inductor and a capacitor. The first bandpass filter 132 has a first passband, and the second bandpass filter 134 has a second passband. By comprising two filters in parallel to each other, the bandwidth of the shunt filter can be increased relative to either of the two individual filters comprised in the shunt filter. The hybrid shunt bandpass filter 130 has a passband comprising the first passband and the second passband. The frequency response of the hybrid shunt bandpass filter 130 can have a notch in its passband between the first passband and the second passband. For example, the notch can be for the Wi-Fi frequency band of 2.4 GHz. In FIG. 13 a symbol 135 of the shunt hybrid bandpass filter 130 is also shown in

[0183] Although embodiments are discussed with reference to shunt hybrid acoustic LC filters for high band filters, any appropriate principles and advantageous aspects discussed herein can be applied to mid band filters, low band filters, or any other filters that can benefit from the features discussed herein.

[0184] The shunt hybrid acoustic LC filters discussed herein can be implemented in a power amplifier module, a diversity receive module, or any other appropriate radio frequency front end module.

[0185] The shunt hybrid acoustic passive filters discussed herein can be implemented in a multiplexer comprising a plurality of filters coupled together at a common node. Such a multiplexer can comprise a diplexer, triplexer, quadplexer, etc. Any appropriate number of filters can be coupled together at the common node in the multiplexer. The plurality of filters can be coupled together at the common node by a multi-throw radio frequency switch to implement a switch multiplexing function. Some example multiplexers comprising shunt hybrid acoustic passive filters will be described with reference to FIG. 14 to FIG. 16 An example multiplexer comprises a shunt hybrid acoustic filter 130 of FIG. 13 and can be implemented according to any appropriate principles and advantageous aspects of the shunt hybrid acoustic filter 130.

[0186] FIG. 14is a schematic block diagram of a duplexer 140 according to one embodiment, including a hybrid shunt bandpass filter 130. The duplexer 140 includes the hybrid shunt bandpass filter 130 and a second filter 144. The shunt hybrid acoustic filter 130 can be a high frequency band filter, and the second filter 144 can be a mid frequency band filter as shown. The shunt hybrid acoustic filter 130 and the second filter 144 can be coupled together at a common node such as the antenna node ANT shown. The second filter 144 can be a hybrid acoustic passive filter, a non-acoustic LC filter, or a sonic wave filter. The second filter 144 can be a bandstop filter. The stop band of the bandstop filter can include some or all of the first passband of the first bandpass filter 132 and / or the second passband of the second bandpass filter 134.

[0187] FIG. 15 is a schematic block diagram of a triplexer 150 according to one embodiment, including a hybrid shunt bandpass filter 130. The triplexer 150 includes the hybrid shunt bandpass filter 130, a second filter 154, and a third filter 156. The shunt hybrid acoustic filter 130 can be a high frequency band filter, and the second filter 154 can be a mid frequency band filter, and the third filter 156 can be a low frequency band filter as shown. The shunt hybrid acoustic filter 130, the second filter 154, and the third filter 156 can be coupled together at a common node such as the antenna node shown. The second filter 154 can be a high pass and bandstop filter. The stop band of the high pass and bandstop filter can include some or all of the first passband of the first bandpass filter 132 and / or the second passband of the second bandpass filter 134. The second filter 154 can be a hybrid acoustic LC filter, a non-acoustic LC filter, or a sonic wave filter. The third filter 156 can be a low pass filter. The third filter 156 can be a hybrid acoustic LC filter, a non-acoustic LC filter, or a sonic wave filter. The third filter 156 can pass frequencies below the respective passbands of the second filter 154 and the hybrid shunt bandpass filter 130.

[0188] FIG. 16 is a schematic block diagram of a triplexer 160 according to one embodiment, including a shared high pass filter 162 and a hybrid shunt bandpass filter 130. The triplexer 160 is similar to the triplexer 150 except that the shared high pass filter 162 is cascaded with both the hybrid shunt bandpass filter 130 and the second filter 144 and the second filter 144 is a bandstop filter. FIG. 15The tripod 150 is identical. Therefore, a shared high-pass filter 162 is coupled between the parallel hybrid acoustic filter 130 and the common node. The shared high-pass filter 162 is also coupled between the second filter 144 and the common node. For example, the shared high-pass filter 162 can be an LC filter or a hybrid acoustic LC filter. In one embodiment, the shared high-pass filter 162 can be a non-acoustic passive filter. Such a shared high-pass filter 162, together with the parallel hybrid acoustic filter 130, can achieve a relatively wide bandwidth and relatively sharp blocking for high-frequency paths.

[0189] FIG. 17 This is a schematic block diagram of a quadrupler 170 according to one embodiment, which includes a shared high-pass filter 162 and a hybrid bandpass filter. The quadrupler 170 is connected to, except that separate terminals are provided for the first bandpass filter 132 and the second bandpass filter 134, respectively. FIG. 16 The triplet 160 is identical. This allows for greater freedom in carrier aggregation options. In the quadruplet 170, the first bandpass filter 132 and the second bandpass filter 134 can receive signals in different frequency bands and filter the corresponding signals.

[0190] FIG. 17 This is an example of a multiplexer that includes hybrid acoustic passive filters. The first bandpass filter 132 and the second bandpass filter 134 have different passbands, and both are coupled to a common node via a shared high-pass filter 162. FIG. 17 The first bandpass filter 132 and / or the second bandpass filter 134 may include multiple acoustic resonators and non-acoustic passive components. The non-acoustic passive components may include inductors and capacitors located outside the wafer including the acoustic resonators. The non-acoustic passive components may include an inductor connected in parallel with one of the multiple acoustic resonators. The first bandpass filter 132 and / or the second bandpass filter 134 may include any suitable combination of the features of the hybrid acoustic passive filters disclosed herein. In some embodiments, each of the first bandpass filter 132 and the second bandpass filter 134 has a passband in a frequency range from 2 GHz to 5 GHz, for example, in a frequency range from 2 GHz to 3 GHz.

[0191] A band-stop filter 144 is coupled to a common node via a shared high-pass filter 162. The band-stop filter 144 includes a stopband that includes the passbands of a first band-pass filter 132 and a second band-pass filter. A low-pass filter 156 is coupled to the common node.

[0192] Using a four-tool 170, it can be compared to FIG. 16of the fourplexer. By not filtering the first carrier with the second bandpass filter 134, there can be less insertion loss degradation in the triplexer 160 relative to the fourplexer 170

[0193] FIG. 18 is a schematic diagram of a triplexer 180 including a hybrid shunt bandpass filter 182, in accordance with one embodiment. In FIG. 18 is shown an example multiplexer having a hybrid shunt bandpass filter. As shown, the triplexer 180 includes a hybrid shunt bandpass filter 182, a hybrid acoustic LC filter 184, a non-acoustic LC filter 186, and a harmonic trap filter 188.

[0194] The hybrid shunt bandpass filter 182 is an example of the hybrid shunt bandpass filter 130. The hybrid shunt bandpass filter 182 is a high band filter in the triplexer 180. The hybrid shunt bandpass filter 182 is an example filter topology of acoustic resonators and inductors. As shown, the hybrid shunt bandpass filter 182 is provided with a high band signal through inductors L180i and L1802. The hybrid shunt bandpass filter 182 includes a first sub-filter including acoustic resonators A180i, A1802, A1803, A1804, A1805, A1806, A1807, A1808, A1809, and A1810, and inductors L1803, L1804, and L1805. The hybrid shunt bandpass filter 182 also includes a second sub-filter including acoustic resonators A1811, A1812, A1813, A1814, A1815, A1816, A1817, A1818, A1819, and A1820, and inductors L1806 and L1807. The hybrid shunt bandpass circuit 182 includes parasitic capacitances not shown in FIG. 18 The inductors of the hybrid shunt bandpass filter 182 can include one or more SMT inductors and / or one or more conductive traces of a substrate. The acoustic resonators of the hybrid shunt bandpass filter 182 can include one or more BAW resonators, such as one or more FBARs.

[0195] The hybrid acoustic LC filter 184 includes acoustic resonators, inductors, and capacitors. As shown, the hybrid acoustic LC filter 184 includes acoustic resonators A182i, A1822, A1823, A1824, A1825, A1826, A1827, A1828, and A1829; inductors L1808, L1809, L1810, L1811, and L1812; and capacitors C180i and C1802. The hybrid acoustic LC filter 184 can be implemented in accordance with any suitable principles and advantageous aspects of hybrid acoustic LC filters disclosed herein. The hybrid acoustic LC filter 184 is a mid-band filter in the triplexer 180.

[0196] The non-acoustic LC filter 186 is a low-band filter in the triplexer 180. The non-acoustic LC filter 186 can be a low-pass filter. For example, such a low-pass filter can be implemented in accordance with any suitable principles and advantageous aspects of low-pass filters of FIG. 24A and / or FIG. 24B .

[0197] The harmonic trap filter 188 can provide a trap at a harmonic of the radio frequency signal to filter out the harmonic. For example, the harmonic trap filter 188 can be implemented in accordance with any suitable principles and advantageous aspects of low-pass filters of FIG. 24D . The illustrated harmonic trap filter 188 includes capacitors C1803, C1804, C1805, and C1806 and inductors L1813 and L1814. The harmonic trap filter 188 can provide traps at two harmonic frequencies.

[0198] FIG. 19A Analog results for the triplexer 180 of FIG. 18 are shown. FIG. 19A The passbands of the filters 182, 184, and 186 of the triplexer 180 are shown. The low-pass filter 186 has a passband indicated by a curve using a solid line. The mid-band filter 184 has a passband represented by a first dashed curve. The passband of the parallel hybrid acoustic bandpass filter 182 is represented by a different dashed curve. The parallel hybrid acoustic bandpass filter 182 has a trap in the middle portion of its passband. This trap can correspond to a range of frequencies between two different frequency bands for which the parallel hybrid acoustic bandpass filter 182 is arranged to pass. The analog results show that the isolation is improved across the mid-band and high-band filters in the triplexer 180 compared to the previous design. In the analog of the triplexer 180 of FIG. 18 there is a reasonable insertion loss.

[0199] FIG. 19B Analog results for the triplexer 180 of FIG. 18a graph of simulation results for the triplexer 180. These simulation results show that both insertion loss and isolation are improved using the triplexer 180 compared to previous designs.

[0200] While embodiments of the shunt hybrid acoustic filter discussed herein relate to bandpass filters, any suitable principles and advantageous aspects of the shunt hybrid acoustic filter discussed herein can be applied to bandstop filters. A shunt hybrid acoustic bandstop filter can be implemented as a standalone filter or implemented in a multiplexer. Reference will be made to FIG. 20 to 22 An exemplary shunt hybrid acoustic bandstop filter is discussed.

[0201] FIG. 20 is a schematic block diagram of a hybrid shunt bandstop filter 200 according to an embodiment. The hybrid shunt bandstop filter 200 can produce a relatively wide band rejection at a passband of another filter without using an LC notch filter, which can more significantly reduce in-band loss.

[0202] The shunt hybrid bandstop filter 200 includes a first bandstop filter 202 and a second bandstop filter 204 arranged in parallel to each other. The first bandstop filter 202 and the second bandstop filter 204 are arranged for filtering a radio frequency signal. The first bandstop filter 202 is a hybrid acoustic passive filter including a first acoustic resonator and a first non-acoustic passive component. The first non-acoustic passive component can include at least an inductor and a capacitor. The second bandstop filter 204 is a hybrid acoustic passive filter including a second acoustic resonator and a second non-acoustic passive component. The second non-acoustic passive component can include at least an inductor and a capacitor. The first bandstop filter 202 has a first stopband, and the second bandstop filter 204 has a second stopband. By including two filters in parallel to each other, the stopband of the shunt hybrid bandstop filter 200 can be increased relative to either of the two individual filters 202 or 204 included in the shunt filter.

[0203] The hybrid shunt bandstop filter 200 has a stopband including the first stopband and the second stopband. The frequency response of the hybrid shunt bandstop filter 200 can have a notch in its stopband between the first stopband and the second stopband. In FIG. 20 A label 205 of the shunt hybrid bandpass filter 200 is also shown in

[0204] FIG. 21 is a schematic diagram of a hybrid shunt bandstop filter 210 according to an embodiment. The hybrid shunt bandstop filter 210 is FIG. 20 is an example of the hybrid shunt bandstop filter 200. The hybrid shunt bandstop filter 210 is an example filter topology of acoustic wave resonators and inductors. The hybrid shunt bandstop filter 210 includes a first bandstop filter 212 and a second bandstop filter 214 arranged in parallel to each other. FIG. 21Parasitic capacitances not shown, although these parasitic capacitances are part of the LC circuitry of the hybrid parallel band-stop filter 210.

[0205] As shown in the figure, radio frequency signals can be provided to a hybrid parallel band-stop filter 210 via inductors L2101 and L2102. The hybrid parallel band-stop filter 210 includes a first sub-filter 212, which includes acoustic resonators A2101, A2102, A2103, A2104, and A2105, and inductors L2103, L2104, L2105, L2106, and L2107. The hybrid parallel band-stop filter 210 also includes a second sub-filter 214, which includes acoustic resonators A216, A217, A218, A219, and A220; inductors L2108, L2109, and L2110; and a capacitor C2101. The inductors of the hybrid parallel band-stop filter 210 may include one or more SMT inductors and / or one or more conductive traces on the substrate. The acoustic resonator of the hybrid parallel band-stop filter 210 may include one or more BAW resonators, such as one or more FBARs.

[0206] FIG. 22 yes FIG. 21 A graph showing the frequency response of the hybrid parallel band-stop filter 210. FIG. 22 The frequency response in the figure shows that a relatively wide stopband can be achieved using a parallel hybrid acoustic bandstop filter 210.

[0207] Hybrid acoustic LC filter with harmonic suppression

[0208] With the development of 5G wireless communication technology, new carrier aggregation (CA) can specify more stringent intermodulation distortion (IMD) rejection for filters. To provide CA IMD-compatible filters with sharp rejection near the passband frequencies, acoustically assisted filters can be designed using hybrid resonators, such as hybrid acoustic LC resonators, to provide relatively low loss, a wide passband, and relatively sharp rejection near the passband frequencies. Acoustic resonators can generate harmonics when relatively high power is applied. Harmonics generated by surface acoustic devices or bulk acoustic devices can leak into higher frequency bands and / or have efferentiations exceeding standard specifications.

[0209] Because acoustic resonator filters can generate harmonics at relatively high power, passive non-acoustic filters can be cascaded with hybrid acoustic LC filters to achieve both rejection and suppression of harmonics generated by the resonator. Therefore, non-acoustic LC filters, such as integrated passive device (IPD) filters, can be cascaded with hybrid acoustic LC filters to achieve relatively wide bandwidth and relatively high rejection while suppressing self-generated harmonics.

[0210] The hybrid acoustic LC filters and / or multiplexers discussed herein can include a harmonic rejection filter to reject one or more harmonic frequencies. The harmonic rejection filter can be a low pass filter and / or a notch filter. The disclosed harmonic rejection filter includes a non-acoustic filter. For example, the harmonic rejection filter can be an IPD filter. The harmonic rejection filter is cascaded with the hybrid acoustic LC filter. These cascaded filters can be coupled between a power amplifier and an antenna port. For example, the harmonic rejection filter can be coupled between an antenna port and the hybrid acoustic LC filter.

[0211] Aspects of the disclosure relate to hybrid acoustic LC filters with harmonic rejection. The hybrid acoustic LC includes a hybrid passive / acoustic filter configured to filter a radio frequency signal and a non-acoustic LC filter configured to reject a harmonic of the radio frequency signal. The hybrid passive / acoustic filter includes a plurality of acoustic resonators and a non-acoustic passive component. The non-acoustic LC filter is cascaded with the hybrid passive / acoustic filter.

[0212] The non-acoustic LC filter can be a notch filter. The frequency response of the notch filter can have a notch corresponding to a second harmonic of the radio frequency signal. The frequency response of the notch filter can have a notch corresponding to a third harmonic of the radio frequency signal. The non-acoustic LC filter can be a low pass filter. The non-acoustic LC filter can include an integrated passive device of an integrated passive device wafer.

[0213] The hybrid passive / acoustic filter can be implemented according to any suitable principles and advantageous aspects of any of the hybrid resonators disclosed herein. For example, the hybrid passive / acoustic filter can include a hybrid resonator of FIG. 11A and / or a hybrid resonator of FIG. 12 The acoustic resonators can include bulk wave acoustic resonators.

[0214] The hybrid acoustic LC filters with harmonic rejection can be implemented in various applications, such as standalone filters, in multiplexers including a plurality of filters arranged to filter a radio frequency signal, and in wireless communication devices such as mobile phones. The hybrid acoustic LC filters with harmonic rejection discussed herein can be implemented in a power amplifier module, a diversity receive module, or any other suitable radio frequency front end module.

[0215] FIG. 23AThis is a schematic block diagram of a radio frequency (RF) system according to one embodiment, including a filter 230 comprising a hybrid acoustic LC filter 232 cascaded with a low-pass filter 233. The RF system also includes a power amplifier 231 and an antenna 234. As shown, the hybrid acoustic LC filter 232 can receive an RF signal from the power amplifier 231. The RF signal from the power amplifier 231 can have relatively high power. The acoustic resonator of the hybrid acoustic LC filter 232 can generate one or more harmonics. The low-pass filter 233 can filter out such harmonics. Therefore, filter 230 is a hybrid acoustic LC filter with harmonic suppression. As shown, the low-pass filter 233 is coupled between the output of the hybrid acoustic LC filter 232 and the antenna 234. The antenna 234 can transmit a filtered version of the RF signal provided by the power amplifier 231.

[0216] The hybrid acoustic LC filter 232 may include acoustic resonators and non-acoustic passive components. The acoustic resonators may include one or more bulk acoustic resonators such as FBAR, one or more SAW resonators, one or more boundary wave resonators, one or more Lamb wave resonators, etc., or any suitable combination thereof. The hybrid acoustic LC filter 232 may include an LC circuit comprising one or more inductors and one or more capacitors. The one or more capacitors may include one or more IPD capacitors, one or more surface mount capacitors, one or more parasitic capacitors, etc., or any suitable combination thereof. The one or more inductors may include one or more IPD inductors, one or more surface mount conductors, one or more inductors implemented as conductive traces on a package substrate, etc., or any suitable combination thereof. The hybrid acoustic LC filter 232 may be implemented according to any suitable principles and advantages of the hybrid acoustic LC filters disclosed herein. In some instances, the hybrid acoustic LC filter 232 may include... FIG. 11A The hybrid resonator 110. In some applications, the hybrid acoustic LC filter 232 may include... FIG. 12 The hybrid trapezoidal structure 120.

[0217] In some applications, the hybrid acoustic LC filter 232 may have a passband from 3.3 GHz to 4.2 GHz. Depending on other applications, the hybrid acoustic LC filter 232 may have a passband from 4.4 GHz to 5 GHz. In various embodiments, the hybrid acoustic LC filter 232 may provide blocking for (a) a carrier aggregation transmit blocker and (b) a continuous wave out-of-band blocker.

[0218] The low-pass filter 233 allows signals below the cutoff frequency to pass through and suppresses signals above the cutoff frequency. Therefore, the cutoff frequency of the low-pass filter 233 can be selected to allow radio frequency signals from the hybrid acoustic LC filter 232 to pass through and suppress one or more harmonics of the radio frequency signal. For example, the cutoff frequency can be set to be higher than the frequency of the radio frequency signal and lower than the frequency of the second harmonic of the radio frequency signal. In some embodiments, the hybrid acoustic LC filter 232 is a bandpass filter, and the cutoff frequency of the low-pass filter 233 is higher than the passband of the bandpass filter and lower than the second harmonic of the radio frequency signal passed by the bandpass filter.

[0219] The low-pass filter 233 may be a non-acoustic LC filter. The low-pass filter 233 may include one or more capacitors and one or more inductors. The low-pass filter 233 may include one or more IPDs, one or more surface-mount passive components, one or more passive components of the package substrate (such as one or more inductor traces on the package substrate), or any suitable combination thereof. (See reference...) FIG. 24A and 24B An example circuit topology for a low-pass filter 233 is discussed.

[0220] FIG. 23B This is a schematic block diagram of a radio frequency system according to one embodiment, the radio frequency system including a filter 235, the filter 235 including a hybrid acoustic LC filter 232 cascaded with a harmonic notch filter 236. Besides FIG. 23A The filter 230 was FIG. 23B In addition to replacing the 235 filter in the original, FIG. 23B radio frequency system and FIG. 23A The radio frequency system is the same. Except for replacing the one from... FIG. 23A In addition to the low-pass filter 233 of filter 230, which includes harmonic notch filter 236, filter 235 and FIG. 23A The filter 230 is the same. As shown in the figure, the harmonic notch filter 236 is coupled between the output of the hybrid acoustic LC filter 232 and the antenna 234.

[0221] The harmonic trap filter 236 can have one or more traps in its frequency response to filter out one or more corresponding harmonics of the radio frequency signal from the hybrid acoustic LC filter 232. The second harmonic produced by the acoustic resonator of the hybrid acoustic resonator LC filter 232 can be the most prominent harmonic. Thus, the harmonic trap filter 236 can be a second harmonic trap filter that has a trap at the second harmonic in its frequency response. The harmonic trap filter 236 can have traps at one or more other harmonics. In certain embodiments, a harmonic trap filter cascaded with the hybrid acoustic LC filter 232 can have two or more traps at any suitable harmonics. As an example, a harmonic trap filter can have traps at the second and third harmonics. With the traps at the harmonics of the radio frequency signal provided by the hybrid acoustic LC filter 232, the harmonic trap filter 236 can suppress the harmonics produced by the acoustic resonator of the hybrid acoustic LC filter 232.

[0222] The harmonic trap filter 236 can be a non-acoustic LC filter that includes one or more capacitors and one or more inductors. The harmonic trap filter 236 can include one or more IPDs, one or more surface mount passive components, one or more passive components of a package substrate, such as one or more inductive traces on a package substrate, or the like, or any suitable combination thereof. Example circuit topologies for the harmonic trap filter 236 and / or other suitable harmonic trap filters will be discussed with reference to FIG. 24C and 24D

[0223] FIG. 24A is a schematic diagram of an example low pass filter 240. The low pass filter 240 is an example of the low pass filter 233 of FIG. 23A The low pass filter 240 includes a series inductor LI and a shunt capacitor CI arranged to filter out frequencies above a cutoff frequency. The inductance of the series inductor LI and the capacitance of the shunt capacitor CI can together set the cutoff frequency in the low pass filter 240.

[0224] FIG. 24B is a schematic diagram of another example low pass filter 242. The low pass filter 242 is an example of the low pass filter 233 of FIG. 23A The low pass filter 242 includes series inductors LI to LN and shunt capacitors CI to CN. The inductances of the series inductors LI to LN and the capacitances of the shunt capacitors CI to CN can together set the cutoff frequency in the low pass filter 242.

[0225] FIG. 24C is a schematic diagram of an example harmonic trap filter 243. The harmonic trap filter 243 is an example of the harmonic trap filter 236 of FIG. 23B ​is an example of a harmonic trap filter 236. The harmonic trap filter 243 includes a shunt series LC circuit. The inductor Ls and the capacitor Cl of the shunt series LC circuit can set the frequency of the trap. Different impedances of the inductor Ls and the capacitor Cl can together produce traps at different corresponding frequencies. The traps can be provided at any appropriate harmonic frequencies. For example, the traps can be set to the second harmonic of the radio frequency signal provided to the harmonic trap filter 243. As another example, the traps can be set to the third harmonic of the radio frequency signal provided to the harmonic trap filter 243.

[0226] FIG. 24D is a schematic diagram of an example harmonic trap filter 244. The harmonic trap filter 244 is FIG. 23B is an example of a harmonic trap filter 236. The harmonic trap filter 244 includes two shunt series LC circuits. A first shunt series LC circuit includes a capacitor Cl and an inductor Lsl. A second shunt series LC circuit includes a capacitor C2 and an inductor Ls2. The two shunt series LC circuits can provide traps at different harmonics, such as the second harmonic and the third harmonic. Thus, the illustrated harmonic trap filter 244 can provide traps at two different harmonics. The impedance of each shunt series LC can set the respective frequency of each trap. Other harmonic trap filters can provide traps at three or more harmonics.

[0227] FIG. 24E is a schematic diagram of an example harmonic trap and low pass filter 245. The harmonic trap and low pass filter 245 can provide a low pass filter that also includes traps in the frequency response at harmonics. A shunt series LC circuit can provide the harmonic traps. The shunt series LC circuit includes a capacitor Cl and an inductor Ls. A series inductor LI along with a shunt capacitor C2 can provide the low pass filter characteristics.

[0228] The hybrid acoustic LC filters with harmonic rejection discussed herein can be implemented in multiplexers that include multiple radio frequency filters coupled together at a common node. Example multiplexers include duplexers, triplexers, quadplexers, and the like. Any appropriate number of filters can be coupled together at a common node in a multiplexer. The multiple filters can be coupled together at the common node by a multi-throw radio frequency switch to implement a switch multiplexing function. Some example multiplexers including hybrid acoustic LC filters with harmonic rejection will be described with reference to FIG. 25A to 25B

[0229] FIG. 25A ​is a schematic block diagram of a triplexer 250 according to an embodiment, which includes a hybrid acoustic LC filter 232 in cascade with a low pass filter 233. The triplexer 250 includes FIG. 23A filter 230, a high band filter 252, and a low band filter 254. The filter 230, the high band filter 252, and the low band filter 254 are coupled together at a common node, which is an antenna node in the triplexer 250. The filter 230 is a mid band filter in the triplexer 250. The high band filter 252 can be a band pass filter or a high pass filter. The high band filter 252 is arranged to filter high band radio frequency signals. The high band filter 252 can be a hybrid acoustic LC filter implemented according to any appropriate principles and advantageous aspects discussed herein. As one example, the high band filter can include a parallel hybrid acoustic passive filter. In some other embodiments, the high band filter 252 can be implemented by any other appropriate circuit element, such as a non-acoustic LC circuit element. The low band filter 254 can be a low pass filter or a band pass filter. The low band filter 254 is arranged to filter low band radio frequency signals. The low band filter 254 can be a hybrid acoustic LC filter implemented according to any appropriate principles and advantageous aspects discussed herein. In some other embodiments, the low band filter 254 can be implemented by any other appropriate circuit element, such as a non-acoustic LC circuit element.

[0230] FIG. 25B is a schematic block diagram of a triplexer 255 according to an embodiment, which includes a hybrid acoustic LC filter 232 in cascade with a harmonic trap filter 236. The triplexer 255 is the same as the triplexer 250 of FIG. 25A except that the filter 235 is included instead of the filter 230. The filter 235 includes the harmonic trap filter 236, which is arranged to suppress harmonics in radio frequency signals provided by the hybrid acoustic LC filter 232. In some applications, the harmonic trap filter 236 can provide a trap for two or more harmonics. In certain embodiments, the filter of a multiplexer can include a hybrid acoustic LC filter in cascade with a low pass and a harmonic trap filter.

[0231] radio frequency module

[0232] The filters disclosed herein can be implemented in various packaging modules. Some example packaging modules will now be disclosed, in which any appropriate principles and advantageous aspects of the filters and / or multiplexers disclosed herein can be implemented. The example packaging modules can include a package enclosing the illustrated circuit elements. A module that includes radio frequency components can be referred to as a radio frequency module. The illustrated circuit elements can be disposed on a common package substrate. For example, the package substrate can be a laminate substrate. FIG. 26 to FIG. 28is a schematic block diagram of an exemplary packaging module according to certain embodiments. Any suitable combination of features of these packaging modules can be implemented in conjunction with one another. Although the packaging modules are shown in the example packaging module of FIG. 26 to FIG. 28 Filters are shown in the example packaging module, but any such filters can be implemented in a suitable multiplexer.

[0233] FIG. 26 is a schematic diagram of a radio frequency module 260 having a transmit path including a filter 262 according to one embodiment. The illustrated module 260 includes the filter 262, a power amplifier 263, and a radio frequency switch 264. A radio frequency module including a power amplifier can be referred to as a power amplifier module. The power amplifier 263 can amplify a radio frequency signal. The radio frequency switch 264 can be a multi-throw radio frequency switch. The radio frequency switch 264 can electrically couple an output of the power amplifier 263 to the filter 262. The filter 262 is a transmit filter arranged to filter a transmit radio frequency signal. The filter 262 can include any suitable combination of features of the filters disclosed herein. In some other instances, a radio frequency switch can selectively electrically connect a transmit signal path to an input of a power amplifier.

[0234] FIG. 27 is a schematic diagram of a radio frequency module 270 having a receive path including a filter 272 according to one embodiment. The illustrated module 270 includes the filter 272, a low noise amplifier 274, and a radio frequency switch 274. The filter 272 is a receive filter arranged to filter a received radio frequency signal. The filter 272 can include any suitable combination of features of the filters disclosed herein. The low noise amplifier 274 can amplify a filtered received radio frequency signal provided by the filter 272. The radio frequency switch 274 can electrically couple an output of the low noise amplifier 274 to a receive path. In certain embodiments, the radio frequency switch 276 can be a multi-throw radio frequency switch arranged to selectively electrically couple an output of the low noise amplifier 274 to one or more selected receive paths. In such embodiments, a radio frequency splitter (not shown) can be coupled between the low noise amplifier 274 and the radio frequency switch 276.

[0235] FIG. 28 is a schematic diagram of a radio frequency module 280 including a filter 282 according to one embodiment. The illustrated module 280 includes one or more filters 282, a radio frequency switch 284, a power amplifier 263, and a low noise amplifier 274. The one or more filters 282 can include any suitable combination of features of the filters disclosed herein. The radio frequency switch 284 can electrically couple the one or more filters 282 to the power amplifier 263 and / or the low noise amplifier 274.

[0236] Wireless communication device

[0237] The filters discussed herein can filter radio frequency signals in a wireless communication device. Reference will be made to FIG. 29 and FIG. 30 to discuss example wireless communication devices.

[0238] FIG. 29 is a schematic diagram of a wireless communication device 290 that includes a filter 293 in a radio frequency front end 292, according to an embodiment. The wireless communication device 290 can be any suitable wireless communication device. For example, the wireless communication device 290 can be a mobile phone, such as a smartphone. As shown, the wireless communication device 290 includes an antenna 291, the RF front end 292 that includes the filter 293, a transceiver 294, a processor 295, a memory 296, and a user interface 297. The antenna 291 can transmit RF signals provided by the RF front end 292. Such RF signals can include carrier aggregation signals. The antenna 291 can provide received RF signals to the RF front end 292 for processing. Such RF signals can include carrier aggregation signals.

[0239] The RF front end 292 can include one or more power amplifiers, one or more low noise amplifiers, RF switches, receive filters, transmit filters, duplex filters, multiplexers, frequency multiplexing circuitry, or any combination thereof. The RF front end 292 can transmit and receive RF signals associated with any suitable communication standard. The filter 293 can be implemented according to any suitable principles and advantageous aspects of the filters discussed herein. For example, the filter 293 can implement any suitable combination of the features discussed with reference to any one of Figures 1 to FIG. 25B Two or more filters of the RF front end 292 can be implemented according to any suitable principles and advantageous aspects disclosed herein.

[0240] The transceiver 294 can provide RF signals to the RF front end 292 for amplification and / or other processing. The transceiver 294 can also process RF signals provided by the low noise amplifiers of the RF front end 292. The transceiver 294 is in communication with the processor 295. The processor 295 can be a baseband processor. The processor 295 can provide any suitable baseband processing functionality for the wireless communication device 290. The memory 296 is accessible by the processor 295. The memory 296 can store any suitable data for the wireless communication device 290. The processor 295 is also in communication with the user interface 297. The user interface 297 can be any suitable user interface, such as a display.

[0241] FIG. 30This is a schematic diagram of a wireless communication device 300 according to one embodiment, which includes a filter 293 in a radio frequency front-end 292 and a second filter 303 in a diversity reception module 302. In addition to including diversity reception features, the wireless communication device 300 also includes other features. FIG. 29 The wireless communication device 290 is the same. For example... FIG. 30 As shown, the wireless communication device 300 includes a diversity antenna 301, a diversity module 302, and a transceiver 304. The diversity module 302 is configured to process signals received by the diversity antenna 301 and includes a filter 303. The transceiver 304 communicates with both the radio frequency front-end 292 and the diversity receiving module 302. The filter 303 can be implemented according to any suitable principles and advantages of the filters discussed herein. For example, the filter 303 can be implemented with reference to Figures 1 to 2018. FIG. 25B Any suitable combination of any of the features discussed herein. The two or more filters of diversity receiving module 302 may be implemented according to any suitable principles and advantages disclosed herein.

[0242] in conclusion

[0243] Any principles and advantages discussed herein can be applied to other suitable systems, modules, chips, filter assemblies, filters, wireless communication devices, and methods, and are not limited to those described above. Elements and operations of the various embodiments described above can be combined to provide further embodiments. Any principles and advantages discussed herein can be implemented in association with radio frequency circuits configured to process signals with frequencies ranging from about 30 kHz to 300 GHz (e.g., frequencies ranging from about 450 MHz to 8.5 GHz).

[0244] The various aspects of this disclosure can be implemented in a variety of electronic devices. Examples of electronic devices include, but are not limited to, consumer electronics products, components of consumer electronics products such as chips and / or packaged radio frequency modules, electronic test equipment, uplink wireless communication equipment, personal area network communication equipment, etc. Examples of consumer electronics products include, but are not limited to, mobile phones such as smartphones, wearable computing devices such as smartwatches or headphones, telephones, televisions, computer monitors, computers, routers, modems, handheld computers, laptop computers, tablet computers, personal digital assistants (PDAs), in-vehicle electronic systems such as automotive electronic systems, microwave ovens, refrigerators, stereo systems, digital music players, cameras such as digital cameras, portable memory chips, home appliances, etc. Furthermore, electronic devices may include unfinished products.

[0245] Unless otherwise stated or understood in other manners, conditional language such as "can," "could," "might," "may," "e.g.," "for example," "e.g.," "for instance," "such as," or the like, is understood in the context as actually indicating that certain embodiments include, while other embodiments do not include, certain features, elements, and / or states. The term "coupled" generally is used in the context herein to refer to two or more elements that can be either directly connected, or connected by way of one or more intermediate elements. Likewise, the term "connected" generally is used in the context herein to refer to two or more elements that can be either directly connected, or connected by way of one or more intermediate elements. Additionally, the words "herein," "above," "below," and words of similar import, when used in this application, should not be understood to limit any aspect of the application to that particular paragraph or passages making use of such terms but should be interpreted to include the entire application as a whole. Where the context permits, words in the above DETAILED DESCRIPTION using the singular or plural number can also include the plural or singular number respectively. The word "or" in reference to a list of two or more items should be construed to cover all possible combinations of those items under the explanation of that word below: any item in the list; all of the items in the list; and any combination of the items in the list.

[0246] While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the application. Indeed, the novel devices, filters, filter assemblies, chips, methods, apparatuses, and systems described herein can be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the form of the methods, apparatuses, and systems described herein can be made without departing from the spirit of the application. For example, circuit blocks described herein can be deleted, moved, added, subdivided, combined, and / or modified. Each of these circuit blocks can be implemented in a variety of different ways. The following claims and their equivalents are intended to cover any such forms or modifications as fall within the scope and spirit of the application.

Claims

1. A cascaded filter for radio frequency filtering, the cascaded filter comprising: a hybrid acoustic LC filter configured to filter a radio frequency signal, the hybrid acoustic LC filter comprising a first acoustic resonator on an acoustic resonator die, a second acoustic resonator, a capacitor external to the acoustic resonator die, and an inductor external to the acoustic resonator die; and a non-acoustic LC filter cascaded with the hybrid acoustic LC filter, the non-acoustic LC filter comprising an LC circuit, the LC circuit of the non-acoustic LC filter comprising a series LC resonant circuit and an LC shunt circuit, the series LC resonant circuit comprising a shunt LC circuit.

2. The cascade filter of claim 1, wherein, the hybrid acoustic LC filter further comprising a second inductor in parallel with the second acoustic resonator, and the second acoustic resonator is arranged as a shunt resonator in series with the inductor.

3. The cascade filter of claim 1, wherein, the first acoustic resonator and the second acoustic resonator are shunt resonators, and the capacitor and the inductor are arranged as an LC tank coupled between the first acoustic resonator and the second acoustic resonator.

4. The cascaded filter of claim 1, wherein, the first acoustic resonator is coupled to a node in a signal path between the LC circuit and both the inductor and the capacitor.

5. The cascade filter of claim 1, wherein, the first acoustic resonator and the second acoustic resonator are bulk acoustic wave resonators.

6. The cascade filter of claim 1, wherein, the LC circuit of the non-acoustic LC filter comprises an integrated passive device on an integrated passive device die.

7. The cascade filter of claim 6, wherein, the inductor of the hybrid acoustic LC filter is a surface mount inductor.

8. The cascaded filter of claim 6, wherein, the inductor of the hybrid acoustic LC filter comprises a conductive trace of a substrate.

9. The cascaded filter of claim 6, wherein, the integrated passive device comprises an LC shunt circuit and a series LC resonant circuit.

10. The cascaded filter of claim 1, wherein, a passband of the cascaded filter is set by the non-acoustic LC filter.

11. The cascaded filter of claim 10, wherein, the first acoustic resonator is arranged to provide a rejection at a frequency band outside the passband.

12. The cascaded filter of claim 10, wherein, a lower limit of the passband is at least 3 gigahertz.

13. The cascaded filter of claim 10, wherein, the passband spans from at least 3.3 gigahertz to 4.2 gigahertz.

14. A multiplexer comprising: a first filter coupled to a common node and configured to filter a radio frequency signal, the first filter comprising a hybrid acoustic LC filter and a non-acoustic LC filter cascaded with the hybrid acoustic LC filter, the hybrid acoustic LC filter comprising a first acoustic resonator on an acoustic resonator die, a second acoustic resonator, a capacitor external to the acoustic resonator die, and an inductor external to the acoustic resonator die, the non-acoustic LC filter comprising an LC circuit, the LC circuit of the non-acoustic LC filter comprising a series LC resonant circuit and an LC shunt circuit, the series LC resonant circuit comprising a shunt LC circuit; and a second filter coupled to the common node.

15. The multiplexer of claim 14, further comprising a third filter coupled to the common node.

16. The multiplexer of claim 14, wherein, the second filter comprises a second hybrid acoustic LC filter.

17. A wireless communication device comprising: an antenna; and a radio frequency filter coupled to the antenna, the radio frequency filter comprising: a hybrid acoustic LC filter configured to filter a radio frequency signal, the hybrid acoustic LC filter comprising a first acoustic resonator on an acoustic resonator die, a second acoustic resonator, a capacitor external to the acoustic resonator die, and an inductor external to the acoustic resonator die; and a non-acoustic LC filter cascaded with the hybrid acoustic LC filter, the non-acoustic LC filter comprising an LC circuit, the LC circuit of the non-acoustic LC filter comprising a series LC resonant circuit and an LC shunt circuit, the series LC resonant circuit comprising a shunt LC circuit. a radio frequency front end in communication with the antenna, the radio frequency front end including a filter configured to filter a radio frequency signal for transmission via the antenna, the filter including a hybrid acoustic LC filter and a non-acoustic LC filter cascaded with the acoustic LC filter, the hybrid acoustic LC filter including an acoustic resonator on an acoustic resonator die, a capacitor external to the acoustic resonator die, and an inductor external to the acoustic resonator die, the non-acoustic LC filter including an LC circuit, the LC circuit of the non-acoustic LC filter including a series LC resonant circuit and an LC shunt circuit, the series LC resonant circuit including a parallel LC circuit.

18. The wireless communication device of claim 17, wherein, The wireless communication device is a mobile phone.

19. A cascaded filter circuit for radio frequency filtering, the cascaded filter circuit comprising: a hybrid acoustic LC filter configured to filter a radio frequency signal, the hybrid acoustic LC filter including a first acoustic resonator on an acoustic resonator die, a capacitor external to the acoustic resonator die, and an inductor external to the acoustic resonator die; a non-acoustic LC filter including an LC circuit; a second non-acoustic LC filter; and a switch configured to couple the hybrid acoustic LC filter and the non-acoustic LC filter in a first state, and to couple the hybrid acoustic LC filter and the second non-acoustic LC filter in a second state. The non-acoustic LC filter is a transmit filter and the second non-acoustic LC filter is a receive filter.

20. The cascaded filter circuit of claim 19, wherein, The hybrid acoustic LC filter further includes a second inductor in parallel with the first acoustic resonator, and the acoustic resonator is arranged as a shunt resonator in series with the inductor.

21. The cascaded filter circuit of claim 19, wherein, The hybrid acoustic LC filter further includes a second acoustic resonator, the first acoustic resonator and the second acoustic resonator are shunt resonators, and the capacitor and the inductor are arranged as an LC tank between the first acoustic resonator and the second acoustic resonator.

22. The cascaded filter circuit of claim 19, wherein, The hybrid acoustic LC filter further includes a second inductor in series with the first acoustic resonator and a third inductor in series with the second acoustic resonator.

23. The cascode filter circuit of claim 22, wherein, The first acoustic resonator is a bulk acoustic wave resonator.

24. The cascaded filter circuit of claim 19, wherein, The LC circuit of the non-acoustic LC filter includes an integrated passive device of an integrated passive device die.

25. The cascaded filter circuit of claim 19, wherein, The inductor of the hybrid acoustic LC filter is a surface mount inductor.

26. The cascode filter circuit of claim 25, wherein, The inductor of the hybrid acoustic LC filter includes a conductive trace of a substrate.

27. The cascode filter circuit of claim 25, wherein, A passband of a cascaded filter including the non-acoustic LC filter and the hybrid acoustic LC filter is set by the non-acoustic LC filter.

28. The cascode filter circuit of claim 19, wherein, A lower limit of the passband is at least 3 gigahertz.

29. The cascode filter circuit of claim 28, wherein, 30. A cascaded filter circuit for radio frequency filtering, the cascaded filter circuit comprising: ​ A hybrid acoustic LC filter configured to filter a radio frequency signal, the hybrid acoustic LC filter comprising a first acoustic resonator on an acoustic resonator wafer, a capacitor external to the acoustic resonator wafer, and an inductor external to the acoustic resonator wafer; A non-acoustic LC filter comprising an LC circuit; A second hybrid acoustic LC filter; and A switch configured to couple the hybrid acoustic LC filter and the non-acoustic LC filter in a first state, and to couple the second hybrid acoustic LC filter and the non-acoustic LC filter in a second state.

31. The cascode filter circuit of claim 30, wherein, The hybrid acoustic LC filter further comprises a second inductor in parallel with the first acoustic resonator, and the acoustic resonator is arranged as a shunt resonator in series with the inductor.

32. The cascode filter circuit of claim 30, wherein, The hybrid acoustic LC filter further comprises a second acoustic resonator, the first acoustic resonator and the second acoustic resonator being shunt resonators, and the capacitor and the inductor are arranged as an LC tank between the first acoustic resonator and the second acoustic resonator.

33. The cascode filter circuit of claim 32, wherein, The hybrid acoustic LC filter further comprises a second inductor in series with the first acoustic resonator and a third inductor in series with the second acoustic resonator.

34. The cascode filter circuit of claim 30, wherein, A passband of the non-acoustic LC filter in cascade with the hybrid acoustic LC filter is set by the non-acoustic LC filter.

35. A method of filtering a radio frequency signal, the method comprising: coupling a hybrid acoustic LC filter and a non-acoustic LC filter with a switch, the hybrid acoustic LC filter comprising an acoustic resonator on an acoustic resonator wafer, a capacitor external to the acoustic resonator wafer, and an inductor external to the acoustic resonator wafer; and filtering a radio frequency signal when the hybrid acoustic LC filter and the non-acoustic LC filter are coupled together, the filtering comprising providing a rejection outside a passband of a filter comprising the hybrid acoustic LC filter and the non-acoustic LC filter using the acoustic resonator of the hybrid acoustic LC filter.

36. The method of claim 35, further comprising: decoupling the hybrid acoustic LC filter from the non-acoustic LC filter with the switch; and coupling the hybrid acoustic LC filter and a second non-acoustic LC filter with the switch.

37. The method of claim 36, further comprising: providing the radio frequency signal to the non-acoustic LC filter with a power amplifier; and amplifying a filtered signal provided by the second non-acoustic LC filter with a low noise amplifier.

38. The method of claim 35, wherein, The radio frequency signal has a frequency in a range from 3 gigahertz to 5 gigahertz.

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