Circulator for full duplex communication

Abstract

An example circulator generally includes a plurality of branches. Each of the branches includes a first acoustic wave resonator and a second acoustic wave resonator coupled in series with the first acoustic wave resonator. Each of the branches further includes a first switch device and a second switch device. The first switch device is coupled in parallel with the first acoustic wave resonator. The second switch device is coupled in parallel with the second acoustic wave resonator.

Description

Cross-references to related applications

[0001] This application claims priority to U.S. Patent Application No. 18 / 426,118, filed January 29, 2024, which is incorporated herein by reference. Technical Field

[0002] Certain aspects of this disclosure relate generally to a circulator and its use in routing signals in electronic devices that support wireless communication. Background Technology

[0003] Wireless communication devices are widely deployed to provide a variety of communication services, such as telephone, video, data, messaging, broadcasting, and so on. These wireless communication devices can transmit and / or receive radio frequency (RF) signals via any of a variety of suitable radio access technologies (RATs), including but not limited to 5G New Radio (NR), Long Term Evolution (LTE), Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Wideband CDMA (WCDMA), Global System for Mobile Communications (GSM), Bluetooth, Bluetooth Low Energy (BLE), ZigBee, and Wireless Local Area Network (WLAN) RATs (e.g., WiFi).

[0004] A wireless communication network may include multiple base stations capable of supporting communication with multiple mobile stations. A mobile station (MS) may communicate with a base station (BS) via downlink and uplink. A downlink (or forward link) refers to the communication link from the base station to the mobile station, while an uplink (or reverse link) refers to the communication link from the mobile station to the base station. The mobile station may transmit data and control information to the base station on the uplink and / or receive data and control information from the base station on the downlink. The base station and / or mobile station may include a circulator that can be used to share an antenna between a transmit chain for processing signals used for wireless transmission and a receive chain for processing signals used for wireless reception. Summary of the Invention

[0005] The systems, methods, and apparatuses of this disclosure each have several aspects, with no single aspect solely responsible for their desired properties. Without limiting the scope of this disclosure as set forth in the following claims, some features will now be briefly discussed. Upon consideration of this discussion, and particularly after reading the section entitled "Detailed Description," it will be understood how the features of this disclosure provide the advantage of including a circulator with two or more fixed-frequency resonators, which are switched using a switching element coupled in parallel with each respective resonator, thereby eliminating the need for lossy and / or nonlinear circuitry elements included in conventional circulators and required to modify the resonant frequency of a single resonator.

[0006] Certain aspects of this disclosure provide a circulator. The circulator typically includes multiple branches. Each branch includes a first acoustic resonator and a second acoustic resonator coupled in series with the first acoustic resonator. Each branch also includes a first switching device coupled in parallel with the first acoustic resonator and a second switching device coupled in parallel with the second acoustic resonator.

[0007] Certain aspects of this disclosure provide a method for wireless communication. The method typically includes: using a circulator to route a first signal from a transmit link to an antenna, the circulator including multiple branches, each branch including: a first acoustic resonator having a first series resonant frequency; a second acoustic resonator coupled in series with the first acoustic resonator and having a second series resonant frequency different from the first series resonant frequency; a first switching device coupled in parallel with the first acoustic resonator; and a second switching device coupled in parallel with the second acoustic resonator. The method further includes: using the circulator to route a second signal from the antenna to a receive link.

[0008] Certain aspects of this disclosure provide an apparatus. The apparatus typically includes a transmit chain, a receive chain, and an antenna. The apparatus also includes a first port coupled to the transmit chain, a second portion coupled to the antenna, and a third port coupled to the receive chain. The circulator also includes multiple branches. Each branch includes a first acoustic resonator and a second acoustic resonator coupled in series with the first acoustic resonator. Each branch also includes a first switching device coupled in parallel with the first acoustic resonator and a second switching device coupled in parallel with the second acoustic resonator.

[0009] To achieve the foregoing and related objectives, one or more aspects include the features fully described below and specifically pointed out in the claims. The following description and drawings illustrate some exemplary features of one or more aspects in detail. However, these features indicate only some of the various ways in which the principles of the various aspects may be employed, and this description is intended to include all such aspects and their equivalents. Attached Figure Description

[0010] To gain a more detailed understanding of the foregoing features of this disclosure, a more specific description, which has been briefly summarized above, can be obtained by referring to various aspects, some of which are illustrated in the accompanying drawings. However, it should be noted that the drawings illustrate only certain typical aspects of this disclosure and are therefore not to be construed as limiting its scope, as other equally valid aspects may be acknowledged in this description.

[0011] Figure 1 This is a diagram illustrating an example wireless communication network in which various aspects of the present disclosure can be practiced.

[0012] Figure 2 It is a block diagram conceptually illustrating the design of an example base station (BS) and user equipment (UE) in which various aspects of this disclosure can be practiced.

[0013] Figure 3 This is a block diagram of an example radio frequency (RF) transceiver in which various aspects of this disclosure can be practiced.

[0014] Figure 4 This is a schematic diagram of an example looper in a first configuration according to certain aspects of this disclosure.

[0015] Figure 5 An example looper in a second configuration is illustrated according to certain aspects of this disclosure.

[0016] Figure 6 It is a graphical representation of the modulation of an acoustic resonator in a branch of a circulator according to certain aspects of this disclosure.

[0017] Figure 7 It is a graphical representation of the frequency response of a circulator according to certain aspects of this disclosure.

[0018] Figure 8 This is a flowchart illustrating example operations for operating a looper according to certain aspects of this disclosure.

[0019] For ease of understanding, the same reference numerals have been used where possible to denote common elements in the figures. It is conceivable that elements disclosed in one aspect may be usefully applied to other aspects without specific description. Detailed Implementation

[0020] Certain aspects of this disclosure relate to circulators used in devices to allow radio frequency (RF) signals to travel along one path (e.g., a transmit path or a receive path) while blocking RF signals from traveling along a different path (e.g., another of the transmit or receive paths). A circulator according to aspects of this disclosure includes multiple branches, each branch including a first acoustic resonator, a second acoustic resonator coupled in series with the first acoustic resonator, a first switching device coupled in parallel with the first acoustic resonator, and a second switching device coupled in parallel with the second acoustic resonator. The first and second switching devices can operate alternately such that only one acoustic resonator is active in each branch at any given time. This arrangement eliminates the need for lossy and / or nonlinear circuit elements included in conventional circulators to modify the resonant frequency of a single resonator.

[0021] Various aspects of this disclosure are described more fully below with reference to the accompanying drawings. However, this disclosure may be embodied in many different forms and should not be construed as limited to any particular structure or function presented throughout this disclosure. Rather, these aspects are provided so that this disclosure will be comprehensive and complete, and will fully convey the scope of protection of this disclosure to those skilled in the art. Based on the teachings herein, those skilled in the art should understand that the scope of this disclosure is intended to cover any aspect of the disclosure herein, whether implemented independently or in combination with any other aspect of this disclosure. For example, any number of aspects set forth herein may be used to implement an apparatus or practice. Furthermore, the scope of this disclosure is intended to cover such apparatuses or methods implemented using structures, functions, or structures and functions other than or different from the aspects of the disclosure set forth herein. It should be understood that any aspect of this disclosure herein may be embodied by one or more elements of the claims.

[0022] The word “exemplary” is used in this document to mean “serving as an example, instance, or illustration.” Any aspect described as “exemplary” in this document is not necessarily to be construed as preferred or superior to other aspects.

[0023] As used in this article, the term "connected with" in various tenses of the verb "connect" can refer to an element. A Directly connected to the component B Or other components can be connected to the component. A With components B Between (i.e., elements) A With components B Indirect connection). In the context of electronic components, the term "connected to..." may also be used herein to refer to leads, traces, or other conductive materials used to connect components.A and components B Electrical connections (and any components that are electrically connected between them). Example wireless system

[0024] Figure 1 Example wireless communication network 100 is illustrated in which various aspects of this disclosure can be practiced. For example, wireless communication network 100 may be a new radio (NR) system (e.g., a fifth-generation (5G) or later NR network), an evolved universal terrestrial radio access (E-UTRA) system (e.g., a fourth-generation (4G) network), a universal mobile telecommunications system (UMTS) (e.g., a second-generation / third-generation (2G / 3G) network), or a code division multiple access (CDMA) system (e.g., a 2G / 3G network), or may be configured to communicate according to one or more IEEE standards such as the 802.11 standard.

[0025] like Figure 1 As illustrated, the wireless communication network 100 may include several base stations (BS) 110a to 110z (each individually referred to herein as BS 110 or collectively as BS 110) and other network entities. BS may also be referred to as access point (AP), evolved Node B (eNodeB or eNB), next-generation Node B (gNodeB or gNB), or some other terminology.

[0026] BS 110 can provide communication coverage for a specific geographic area (sometimes referred to as a "cell"), which can be stationary or mobile depending on the location of the mobile BS 110. In some examples, BS 110 can use any suitable transport network, interconnecting with each other and / or connecting to one or more other BSs or network nodes (not shown) in the wireless communication network 100 via various types of backhaul interfaces (e.g., direct physical connection, wireless connection, virtual network, etc.). Figure 1 In the example shown, BS 110a, 110b, and 110c can be macro BSs for macro cells 102a, 102b, and 102c, respectively. BS 110x can be a pico BS for pico cell 102x. BS 110y and 110z can be femto BSs for femto cells 102y and 102z, respectively. A BS can support one or more cells.

[0027] BS 110 communicates with one or more user equipment (UEs) 120a to 120y (each individually referred to herein as "UE 120" or collectively as "UE 120") in the wireless communication network 100. The UE can be fixed or mobile and can also be referred to as a user terminal (UT), mobile station (MS), access terminal, station (STA), client, wireless device, mobile device, or some other term. The user terminal can be a wireless device such as a cellular phone, smartphone, personal digital assistant (PDA), handheld device, wearable device, wireless modem, laptop computer, tablet computer, personal computer, etc.

[0028] BS 110 is considered a transmitting entity for downlink and a receiving entity for uplink. UE 120 is considered a transmitting entity for uplink and a receiving entity for downlink. As used herein, a “transmitting entity” is a separately operating apparatus or device capable of transmitting data via a frequency channel, and a “receiving entity” is a separately operating apparatus or device capable of receiving data via a frequency channel. In the following description, the subscript “…” dn " indicates the downlink, subscript " up "Indicates uplink. You can select..." N up Each UE is used for simultaneous transmission on the uplink, and can be selected. N dn Each UE is used for simultaneous transmission on the downlink. N up It can be equal to or not equal to N dn ,and N up and N dn It can be a static value or it can be changed for each scheduling interval. Beam control or some other spatial processing techniques can be used at BS 110 and UE 120.

[0029] UEs 120 (e.g., 120x, 120y, etc.) may be distributed throughout the wireless communication network 100, and each UE 120 may be stationary or mobile. The wireless communication network 100 may also include relay stations (e.g., relay station 110r) (also referred to as repeaters, etc.) that receive data transmissions and / or other information transmissions from upstream stations (e.g., BS 110a or UE 120r) and transmit the data transmissions and / or other information transmissions to downstream stations (e.g., UE 120 or BS 110), or relay transmissions between UEs 120 to facilitate communication between devices.

[0030] BS 110 can communicate with one or more UE 120s on both the downlink and uplink at any given time. The downlink (i.e., the forward link) is the communication link from BS 110 to UE 120, while the uplink (i.e., the reverse link) is the communication link from UE 120 to BS 110. UE 120 can also communicate peer-to-peer with another UE 120.

[0031] Wireless communication network 100 can use multiple transmit antennas and multiple receive antennas to transmit data on the downlink and uplink. BS 110 can be equipped with several ( N ap (Number) antennas to achieve transmit diversity for downlink transmission and / or receive diversity for uplink transmission. A set of ( N u Each UE 120 can receive downlink transmissions and send uplink transmissions. Each UE 120 can send user-specific data to and / or receive user-specific data from the BS 110. Typically, each UE 120 may be equipped with one or more antennas. N u Each UE 120 can have the same or different number of antennas.

[0032] The wireless communication network 100 can be a time-division duplex (TDD) system or a frequency-division duplex (FDD) system. In a TDD system, the downlink and uplink share the same frequency band. In an FDD system, the downlink and uplink use different frequency bands. The wireless communication network 100 can also utilize a single carrier or multiple carriers for transmission. Each UE 120 can be equipped with a single antenna (e.g., to reduce cost) or multiple antennas (e.g., where additional cost can be supported).

[0033] Network controller 130 (sometimes referred to as a "system controller") can communicate with a group of BSs 110 and (e.g., via backhaul) provide coordination and control for these BSs 110. In some cases (e.g., in a 5G NR system), network controller 130 may include centralized units (CUs) and / or distributed units (DUs). In some aspects, network controller 130 can communicate with core network 132 (e.g., a 5G core network (5GC)) that provides various network functions such as access and mobility management, session management, user plane functions, policy control functions, authentication server functions, unified data management, application functions, network openness functions, network repository functions, network slice selection functions, etc.

[0034] In certain aspects of this disclosure, BS 110 and / or UE 120 may include a circulator, as described in more detail herein.

[0035] Figure 2 Examples of BS 110a and UE 120a in which aspects of this disclosure may be implemented (e.g., from...) Figure 1 Example components of a wireless communication network 100.

[0036] On the downlink, at BS 110a, the transmitting processor 220 can receive data from data source 212, control information from controller / processor 240, and / or other data (e.g., from scheduler 244). Various types of data can be transmitted on different transport channels. For example, control information can be designated for the Physical Broadcast Channel (PBCH), Physical Control Format Indicator Channel (PCFICH), Physical Hybrid Automatic Repeat Request (HARQ) Indicator Channel (PHICH), Physical Downlink Control Channel (PDCCH), Group Common PDCCH (GC PDCCH), etc. Data can be designated for the Physical Downlink Shared Channel (PDSCH), etc. The Media Access Control (MAC)-Control Element (MAC-CE) is a MAC layer communication structure that can be used for exchanging control commands between wireless nodes. The MAC-CE can be carried in shared channels such as PDSCH, Physical Uplink Shared Channel (PUSCH), or Physical Sidelink Shared Channel (PSSCH).

[0037] Processor 220 can process (e.g., encode and symbol map) data and control information to obtain data symbols and control symbols, respectively. Transmitter processor 220 can also generate reference symbols such as those for primary synchronization signal (PSS), secondary synchronization signal (SSS), PBCH demodulation reference signal (DMRS), and channel state information reference signal (CSI-RS).

[0038] The transmit (TX) multiple-input multiple-output (MIMO) processor 230 can perform spatial processing (e.g., pre-decoding) on ​​data symbols, control symbols, and / or reference symbols where applicable, and can provide the output symbol stream to the modulators (MODs) in transceivers 232a to 232t. Each modulator in transceivers 232a to 232t can process its own output symbol stream (e.g., for orthogonal frequency division multiplexing (OFDM), etc.) to obtain an output sample stream. Each transceiver in transceivers 232a to 232t can further process (e.g., convert to analog, amplify, filter, and up-convert) the output sample stream to obtain a downlink signal. The downlink signal from transceivers 232a to 232t can be transmitted via antennas 234a to 234t, respectively.

[0039] At UE 120a, antennas 252a to 252r can receive downlink signals from BS 110a and can provide the received signals to transceivers 254a to 254r respectively. Transceivers 254a to 254r can adjust (e.g., filter, amplify, down-convert, and digitize) the corresponding received signals to obtain input samples. Each demodulator (DEMOD) in transceivers 232a to 232t can further process the input samples (e.g., for OFDM, etc.) to obtain received symbols. MIMO detector 256 can obtain the received symbols from all demodulators in transceivers 254a to 254r, perform MIMO detection on the received symbols where applicable, and provide the detected symbols. Receiver processor 258 can process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide the decoded data for UE 120a to data sink 260, and provide the decoded control information to controller / processor 280.

[0040] On the uplink, at UE 120a, the transmit processor 264 can receive and process data from data source 262 (e.g., for the Physical Uplink Shared Channel (PUSCH)) and control information from controller / processor 280 (e.g., for the Physical Uplink Control Channel (PUCCH)). The transmit processor 264 can also generate reference symbols for reference signals (e.g., for the Sounding Reference Signal (SRS)). Symbols from the transmit processor 264 can be pre-decoded by the TX MIMO processor 266 where applicable, further processed by modulators (MODs) in transceivers 254a to 254r (e.g., for Single Carrier Frequency Division Multiplexing (SC-FDM), etc.), and transmitted to BS 110a. At BS 110a, the uplink signal from UE 120a can be received by antenna 234, processed by demodulators in transceivers 232a to 232t, detected by MIMO detector 236 where applicable, and further processed by receiver processor 238 to obtain decoded data and control information transmitted by UE 120a. Receiver processor 238 can provide the decoded data to data sink 239 and the decoded control information to controller / processor 240.

[0041] Memory 242 and 282 can store data and program code for BS 110a and UE 120a, respectively. Memory 242 and 282 can also interface with controller / processor 240 and 280, respectively. Scheduler 244 can schedule UEs for data transmission on the downlink and / or uplink.

[0042] Antenna 252, processors 258, 264, 266 and / or controller / processor 280 of UE 120a, and / or antenna 234, processors 220, 230, 238 and / or controller / processor 240 of BS 110a may be used to perform the various techniques and methods described herein.

[0043] NR can use Orthogonal Frequency Division Multiplexing (OFDM) with a cyclic prefix (CP) on both the uplink and downlink. NR can support half-duplex operation using Time Division Duplex (TDD). OFDM and Single-Carrier Frequency Division Multiplexing (SC-FDM) divide the system bandwidth into multiple orthogonal subcarriers, which are often referred to as tones, frequency bands, etc. Each subcarrier can be modulated with data. Modulation symbols can be transmitted in the frequency domain using OFDM and in the time domain using SC-FDM. The spacing between adjacent subcarriers can be fixed, and the total number of subcarriers can depend on the system bandwidth. The system bandwidth can also be divided into subbands. For example, a subband can cover multiple resource blocks (RBs). Although the discussion of NR has been limited to half-duplex operation, it should be understood that NR can also support full-duplex operation associated with other wireless communication schemes, such as Single-Frequency Full-Duplex (SFFD).

[0044] In certain aspects of this disclosure, transceiver 232 and / or transceiver 254 may include a circulator, as described in more detail herein. Example RF transceiver

[0045] Figure 3 This is a block diagram of an example radio frequency (RF) transceiver circuit 300 according to certain aspects of this disclosure. The RF transceiver circuit 300 includes a transmit (TX) path 302 (also referred to as a "transmit chain") for transmitting signals via antenna 306 and a receive (RX) path 304 (also referred to as a "receive chain") for receiving signals via antenna 306. The RF transceiver circuit 300 includes an interface 308 connecting each of the transmit path 302 and the receive path 304 to antenna 306. Interface 308 may, for example, include wideband RF cancellation circuitry. The RF transceiver circuit 300 includes a circulator 309 coupled to interface 308 and antenna 306. The circulator 309 routes a first signal (e.g., a transmit signal) for transmission from transmit path 302 to antenna 306 and routes a second signal (e.g., a receive signal) for reception from antenna 306 to receive path 304. It should be understood that when the first signal is routed from the transmit path 302 to the antenna 306, the circulator 309 isolates the transmit path 302 from the receive path 304. It should also be understood that when the second signal is routed from the antenna 306 to the receive path 304, the circulator 309 isolates the antenna receive path 304 from the transmit path 302.

[0046] Receiving in-phase (I) and / or quadrature (Q) baseband analog signals from a digital-to-analog converter (DAC) 310, the TX path 302 may include a baseband filter (BBF) 312, a mixer 314, a driver amplifier (DA) 316, and a power amplifier (PA) 318. The BBF 312, mixer 314, DA 316, and PA 318 may be included in a radio frequency integrated circuit (RFIC). In some respects, the PA 318 may be external to the RFIC.

[0047] In some respects, DAC 310 can be implemented by any suitable high-speed DAC topology (such as a current-steering DAC) from a variety of suitable high-speed DAC topologies. BBF 312 filters the baseband signal received from DAC 310, and mixer 314 mixes the filtered baseband signal with the transmit local oscillator (LO) signal to convert the baseband signal of interest to a different frequency (e.g., up-convert from baseband to RF). This frequency conversion process produces a sum and difference frequency between the LO frequency and the frequency of the baseband signal of interest. This sum and difference frequency is referred to as the "beat frequency." The beat frequency is typically in the RF range, such that the signal output from mixer 314 is typically an RF signal, which can be amplified by DA 316 and / or PA 318 before being transmitted by antenna 306. When a mixer 314 is exemplified, several mixers can be used to up-convert the filtered baseband signal to one or more intermediate frequencies and subsequently up-convert the IF signal to the frequency used for transmission.

[0048] The RX path 304 may include a low-noise amplifier (LNA) 324, a mixer 326, and a baseband filter (BBF) 328. The LNA 324, mixer 326, and BBF 328 may be included in one or more RFICs, which may be the same RFIC as the RFIC including the TX path components, or may not be the same RFIC as the RFIC including the TX path components. The RF signal received via antenna 306 may be amplified by the LNA 324, and the mixer 326 mixes the amplified RF signal with a received local oscillator (LO) signal to convert the RF signal of interest to a different baseband frequency (e.g., down-conversion). The baseband signal output from the mixer 326 may be filtered by the BBF 328 before being converted to digital I and / or Q signals by an analog-to-digital converter (ADC) 330 for digital signal processing.

[0049] Some transceivers may employ a frequency synthesizer with a variable-frequency oscillator (e.g., a voltage-controlled oscillator (VCO) or a digitally controlled oscillator (DCO)) to generate a stable, tunable LO with a specific tuning range. Thus, the transmit LO may be generated by the TX frequency synthesizer 320, which may be buffered or amplified by amplifier 322 before being mixed with the baseband signal in mixer 314. Similarly, the receive LO may be generated by the RX frequency synthesizer 332, which may be buffered or amplified by amplifier 334 before being mixed with the RF signal in mixer 326. In some aspects, a single frequency synthesizer may be used for both TX path 302 and RX path 304. In some aspects, the TX frequency synthesizer 320 and / or the RX frequency synthesizer 332 may include a frequency multiplier (such as a doubler) driven by an oscillator (e.g., a VCO) in the frequency synthesizer.

[0050] Controller 336 (e.g., Figure 2 The controller / processor 280 in the controller can direct the operation of the RF transceiver circuit 300A, such as transmitting signals via TX path 302 and / or receiving signals via RX path 304. The controller 336 can be a processor, digital signal processor (DSP), application-specific integrated circuit (ASIC), field-programmable gate array (FPGA) or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof. Memory 338 (e.g., Figure 2 The memory 282 in the memory can store data and / or program code used to operate the RF transceiver circuit 300. The controller 336 and / or the memory 338 may include control logic (e.g., complementary metal-oxide-semiconductor (CMOS) logic).

[0051] Although Figures 1 to 3 Wireless communication is provided as an example application (in which certain aspects of this disclosure may be implemented for the purpose of understanding), but certain aspects described herein can be used as circulators in any of a variety of other suitable systems. Example Looper

[0052] Figure 4 A looper 400 according to certain aspects of this disclosure is illustrated. The looper 400 can be implemented as follows: Figure 3 The circulator 309 allows the radio frequency signal to travel along a path (e.g., Figure 3 Sending path 302 or Figure 3 The receiving path 304) travels. In this way, the circulator 400 can control the signal flow and minimize the impact on electronic devices (e.g., including the circulator 400) that include it. Figure 1Interference between different components of UE 120a (e.g., by supporting cancellation techniques). Circulator 400 includes multiple ports. For example, circulator 400 includes ports coupled to the transmission chain (e.g., Figure 3 The first port P1 of the transmission chain 302 is coupled to the antenna (e.g., Figure 3 The second port P2 of the antenna 306) and coupled to the receiver chain (e.g., Figure 3 The third port P3 of the receiving chain 304.

[0053] The looper 400 also includes multiple branches coupled between ports (e.g., first port P1, second port P2, and third port P3). For example, the looper 400 includes a first branch 402, a second branch 404, and a third branch 406. The multiple branches of the looper 400 can be arranged in any suitable topology. For example, the multiple branches can be as follows: Figure 4 The first configuration described is an arrangement (e.g., a star / Y configuration). Alternatively, multiple branches can be arranged as follows: Figure 5 The second configuration (e.g., triangular configuration) arrangement is depicted in the circulator 500.

[0054] As shown in the figure, each of the multiple branches of the circulator 400 (e.g., first branch 402, second branch 404, third branch 406) includes a first acoustic resonator 408 and a second acoustic resonator 410 coupled in series with the first acoustic resonator 408. The first acoustic resonator 408 has a first series resonant frequency, while the second acoustic resonator 410 has a second series resonant frequency different from the first series resonant frequency. In this way, the operating passband of the circulator 400 is defined. In some aspects of this disclosure, the first acoustic resonator 408 may be a first bulk acoustic wave (BAW) resonator, and the second acoustic resonator 410 may be a second BAW resonator. More specifically, the first BAW resonator and the second BAW resonator may each be a film BAW.

[0055] The first acoustic resonator 408 and the second acoustic resonator 410 may each have a quality factor (e.g., the ratio of the center frequency of the main resonator to the bandwidth of the main resonator). In this way, the design of the circulator 400 can be improved compared to a conventional circulator (e.g., lower insertion loss at high frequencies) because the first acoustic resonator 408 and the second acoustic resonator 410 of the disclosed circulator 400 can replace the lumped element resonators (e.g., inductors and capacitors) and varactor diodes used in each branch of a conventional circulator.

[0056] Each of the multiple branches of the circulator 400 includes a first inductor 412 coupled in parallel with the first acoustic resonator 408. Each of the multiple branches of the circulator 400 also includes a second inductor 414 coupled in parallel with the second acoustic resonator 410. The first inductor 412 and the second inductor 414 may each have a low quality factor (e.g., the ratio of inductive reactance to resistance). In this way, the first inductor 412 and the second inductor 414 do not affect (e.g., reduce) the high quality factor of the series resonance of the first acoustic resonator 408 and the series resonance of the second acoustic resonator 410, respectively.

[0057] Furthermore, the first inductor 412 and the second inductor 414 respectively detune the parallel resonance of the first acoustic resonator 408 and the second acoustic resonator 410 at the operating frequency (e.g., the first series resonant frequency and the second series resonant frequency), so that the first acoustic resonator 408 and the second acoustic resonator 410 operate only as series resonators at the operating frequency.

[0058] In this way, by detuning the parallel resonance of the first acoustic resonator 408, the first inductor 412 prevents a decrease in the performance of the circulator 400 at a desired frequency (e.g., a difference) caused by the difference between the series resonance and the parallel resonance of the first acoustic resonator 408. Similarly, by detuning the parallel resonance of the second acoustic resonator 410, the second inductor 414 prevents a decrease in the performance of the circulator at a desired frequency (e.g., the second series resonance frequency) caused by the difference between the series resonance and the parallel resonance of the second acoustic resonator 410.

[0059] In some aspects of this disclosure, the first acoustic resonator 408 and the second acoustic resonator 410 may each have the same static capacitance to avoid switching the impedance of each respective acoustic resonator. In such aspects of this disclosure, the first inductor 412 and the second inductor 414 are identical. In other aspects of this disclosure, the value of the first inductor 412 may differ from the value of the second inductor 414.

[0060] Each of the multiple branches includes a first switching device 416, which is coupled in parallel with a first acoustic resonator 408 and operable to selectively bypass the first acoustic resonator 408. Each of the multiple branches also includes a second switching device 418, which is coupled in parallel with a second acoustic resonator 410 and operable to selectively bypass the second acoustic resonator 410.

[0061] The parallel arrangement of the first switching device 416 and the second switching device 418 relative to the first acoustic resonator 408 and the second acoustic resonator 410 minimizes the number of switching devices required in each corresponding branch of the circulator 400, and thus minimizes the impact of additional switching losses on the performance of the circulator 400.

[0062] As will be discussed in more detail below, switching the first switching device 416 and the second switching device 418 in each corresponding branch of the circulator 400 will generate a time-varying passband in each corresponding branch of the circulator 400.

[0063] In certain aspects of this disclosure, the first switching device 416 and the second switching device 418 of the second branch 404 of the circulator 400 are configured to be controlled with a first phase shift (e.g., implemented by a phase shifter 420) relative to the first switching device 416 and the second switching device 418 of the first branch 402 of the circulator 400. For example, a control signal 422 (e.g., a pulse wave) provided to the first switching device 416 and the second switching device 418 of the first branch 402 of the circulator 400 is phase-shifted according to the first phase shift before being provided to the first switching device 416 and the second switching device 418 of the second branch 404 of the circulator 400. The first phase shift may be, for example, 120 degrees, such that the control signal 422 provided to the first switching device 416 and the second switching device 418 of the second branch 404 is out of phase by 120 degrees relative to the control signal 422 provided to the first switching device 416 and the second switching device 418 of the first branch 402 of the circulator 400.

[0064] Furthermore, the first switching device 416 and the second switching device 418 of the third branch 406 of the circulator 400 are configured to be controlled with a second phase shift relative to the first switching device 416 and the second switching device 418 of the first branch 402 of the circulator 400 (e.g., implemented by a phase shifter 424). For example, the control signal 422 provided to the first switching device 416 and the second switching device 418 of the first branch 402 of the circulator 400 is phase-shifted according to the second phase shift before being provided to the first switching device 416 and the second switching device 418 of the third branch 400. The second phase shift may be 240 degrees, such that the control signal 422 provided to the first switching device 416 and the second switching device 418 of the third branch 406 is out of phase by 240 degrees relative to the control signal 422 provided to the first switching device 416 and the second switching device 418 of the first branch 402 of the circulator 400.

[0065] In certain aspects of this disclosure, a first control signal 426 and a second control signal 428, different from the first control signal 426, may be provided to a first switching device 416 and a second switching device 418 of each of a plurality of branches of the circulator 400, respectively. For example, the first control signal 426 provided to the first switching device 416 of each respective branch of the circulator 400 may be the control signal 422 discussed above, while the second control signal 428 provided to the second switching device 418 of each respective branch of the circulator 400 may be the inverse of the control signal 422 discussed above. Furthermore, the first control signal 426 and the second control signal 428 provided to the first switching device 416 and the second switching device 418 of the second branch 404 and the third branch 406 may have an associated phase offset. More specifically, the first control signal 426 and the second control signal 428 provided to the first switching device 416 and the second switching device 418 of the second branch 404 may have a first phase offset (e.g., 120 degrees). Additionally, the first control signal 426 and the second control signal 428 provided to the first switching device 416 and the second switching device 418 of the third branch 406 respectively may have a second phase offset (e.g., 240 degrees).

[0066] By controlling a first switching device 416 of each corresponding branch of the circulator 400 according to a first control signal 426 and a second switching device 418 of each corresponding branch of the circulator 400 according to a second control signal 428, the first switching device 416 and the second switching device 418 are operated such that only one acoustic resonator (e.g., the first acoustic resonator 408 or the second acoustic resonator 410) in each corresponding branch of the circulator 400 is bypassed at a time. For example, as Figure 4 and Figure 5 As shown, the first switching device 416 of each corresponding branch of the circulator 400 / 500 may be in a first state (e.g., open), while the second switching device 418 of each corresponding branch of the circulator 400 / 500 may be in a second state (e.g., closed).

[0067] In this way, only one acoustic resonator (specifically, the second acoustic resonator 410) is bypassed in each corresponding branch of the circulator 400. To switch from bypassing the second acoustic resonator 410 in each corresponding branch of the circulator 400 to bypassing the first acoustic resonator 408 in each corresponding branch of the circulator 400, the first switching device 416 and the second switching device 418 of each corresponding branch of the circulator 400 can be switched. More specifically, a first control signal 426 can control the first switching device 416 of each corresponding branch of the circulator 400 to switch from a first state (e.g., open) to a second state (e.g., closed). Additionally, a second control signal 428 can control the second switching device 418 of each corresponding branch of the circulator 400 to switch from the second state (e.g., closed) to the first state (e.g., open).

[0068] Figure 6 A graph 600 illustrates the fixed resonant frequencies of two or more acoustic resonators included in one branch of a circulator according to certain aspects of this disclosure. For example, graph 600 depicts the series resonant frequency 1 of the first signal, which represents the frequency referenced above. Figure 4 and Figure 5 The first series resonant frequency of the first acoustic resonator 408 of the circulators 400 and 500 is discussed. Graph 600 also depicts the second signal series resonant frequency 2, which represents the second series resonant frequency of the second acoustic resonator 410 of the circulator 400.

[0069] As shown in the figure, the first series resonant frequency is different from (e.g., lower than) the second series resonant frequency. Furthermore, although the graphical representation is only about one branch of circulators 400 and 500, the curve 600 is generally the same for each of the other branches of circulators 400 and 500. In operation, the first switching device 416 and the second switching device 418 included in each corresponding branch of circulators 400 and 500 are iteratively switched to selectively bypass the first acoustic resonator 408 and the second acoustic resonator 410 one at a time, thereby generating the first signal series resonant frequency 1 and the second signal series resonant frequency 2.

[0070] Figure 7 An example of an instruction looper according to certain aspects of this disclosure is illustrated (e.g., Figure 4 and Figure 5 The performance of the circulator 400 is plotted in graph 700. The horizontal axis of graph 700 represents the frequency (e.g., measured in gigahertz), and the vertical axis (e.g., the left side of graph 700) represents the transmission chain (e.g., ...). Figure 3 The transmission path 302) is connected to the antenna (e.g., Figure 3The insertion loss in decibels between the first port and the second port of the circulator of the antenna 306, and the connection of the antenna to the receiver chain (e.g., Figure 3 The insertion loss, in decibels, between the second port and the third port of the circulator in the receive path 304. The vertical axis (e.g., the right side of graph 700) also represents the insertion loss between the receiver and receiver paths (e.g., the receiver path 304) and the receiver path 304. Figure 3 The first port of the circulator in the sending path 302) and connected to the receiving chain (e.g., Figure 3 The isolation in decibels between the third port of the circulator of the receiving path 304)

[0071] Graph 700 includes a first signal S21 indicating the insertion loss between the first port P1 of circulators 400 and 500 and the second port P2 of circulators 400 and 500. For example, the first port P1 may be coupled to a transmit chain (e.g., Figure 3 The transmission path 302), and the second part P2 of the circulator 400 can be coupled to the antenna (e.g., Figure 3 Antenna 306).

[0072] Graph 700 includes an indication of the first port P1 of the circulator 400 and the coupling to the receiver chain (e.g., Figure 3 The second signal S31 indicates the insertion loss between the third port P3 of the circulators 400 and 500 in the receive path 304. Therefore, the second signal S31 indicates the insertion loss between the circulators 400 and 500 in the receive path 304 and the third port P3. Figure 3 The isolation between the first port P1 of circulator 400 and the third port P3 of circulators 400 and 500 (transmission path 302) is shown. As illustrated, the second signal S31 includes a stopband. Therefore, circulators 400 and 500 attenuate the frequency within the stopband to isolate the third port P3 from the first port P1. In this way, circulators 400 and 500 prevent signals intended for transmission entering the first port P1 of circulators 400 and 500 from traveling to the third port P3 of circulators 400 and 500; instead, the signals must travel to the second port P2 of circulators 400 and 500, which is coupled to the antenna. Example operation for routing signals using a looper

[0073] Figure 8 This is a flowchart illustrating example operation 800 for routing signals in an electronic device including a circulator, according to certain aspects of this disclosure. For example, the above references may be used... Figure 4 and Figure 5 The loops 400 and 500 are discussed to perform operation 800.

[0074] Operation 800 can begin at block 802, where circulators 400 and 500 are used to transfer the first signal from the transmitting chain (e.g., ...). Figure 3 The transmission path 302 in the middle) is routed to the antenna (e.g., Figure 3 Antenna 306 in the first branch 402 and the second switching device 418 in each of the first branch 402 and the second branch 404 can be iteratively switched as described above to generate a passband corresponding to the frequency of the first signal (e.g., antenna 306 in the first branch 402). Figure 7 (Passband 604 in the diagram). In this way, circulators 400 and 500 can route the first signal from the transmit link to the antenna. Furthermore, the first switching device 416 and the second switching device 418 in the third branch 406 of circulators 400 and 500 can be iteratively switched to generate a stopband corresponding to the passband. In this way, circulators 400 and 500 prevent the first signal from traveling from the transmit link 302 to the receive link 304.

[0075] Operation 800 can continue at block 804, where the second signal is routed from the antenna to the receive chain. For example, the first switch 416 and the second switch 418 of the second branch 404 (e.g., coupled to the antenna) of circulators 400 and 500, and the first switch 416 and the second switch 418 of the third branch 406 (e.g., coupled to the receive chain) of circulator 400, can be iteratively switched to generate a passband that includes the frequency of the second signal. In this way, circulators 400 and 500 can route the second signal from the antenna to the receive chain. Furthermore, the first switch 416 and the second switch 418 in the first branch 402 of circulators 400 and 500 can be iteratively switched to generate a stopband corresponding to the passband. In this way, circulators 400 and 500 prevent the second signal from traveling from the antenna to the transmit chain. Example

[0076] In addition to the various aspects described above, specific combinations of these aspects are also within the scope of this disclosure, some of which are detailed below:

[0077] Aspect 1: A circulator comprising: a plurality of branches, each of the plurality of branches comprising: a first acoustic resonator; a second acoustic resonator coupled in series with the first acoustic resonator; a first switching device coupled in parallel with the first acoustic resonator; and a second switching device coupled in parallel with the second acoustic resonator.

[0078] Aspect 2: The circulator according to aspect 1, wherein the first acoustic resonator has a first series resonant frequency, and the second acoustic resonator has a second series resonant frequency different from the first series resonant frequency.

[0079] Aspect 3: The circulator according to aspect 1 or 2, wherein the first acoustic resonator comprises a first bulk acoustic (BAW) resonator, and the second acoustic resonator comprises a second BAW resonator.

[0080] Aspect 4: A circulator according to any one of Aspects 1 to 3, wherein the first switching device is operable to selectively bypass the first acoustic resonator, and the second switching device is operable to selectively bypass the second acoustic resonator. Furthermore, the first switching device and the second switching device are configured to be operated such that they bypass the first acoustic resonator and the second acoustic resonator alternately at a modulation frequency.

[0081] Aspect 5: A circulator according to any one of Aspects 1 to 4, wherein the first switching device of the first branch of the plurality of branches is configured to be controlled with a first phase offset relative to the first switching device of the second branch of the plurality of branches; wherein the first switching device of the third branch of the plurality of branches is configured to be controlled with a second phase offset relative to the first switching device of the second branch of the plurality of branches; and wherein the first phase offset is different from the second phase offset.

[0082] Aspect 6: A circulator according to any one of Aspects 1 to 5, wherein the first switching device and the second switching device in the first branch of the plurality of branches are configured to receive a first control signal and an inverted version of the first control signal, respectively; wherein the first switching device and the second switching device in the second branch of the plurality of branches are configured to receive a second control signal and an inverted version of the second control signal, respectively; wherein the second control signal is out of phase with the first control signal by 120 degrees; wherein the first switching device and the second switching device in the third branch of the plurality of branches are configured to receive a third control signal and an inverted version of the third control signal, respectively; and wherein the third control signal is out of phase with the first control signal by 240 degrees.

[0083] Aspect 7: A circulator according to any one of aspects 1 to 6, wherein each of the plurality of branches further comprises: a first inductor element coupled in parallel with the first acoustic resonator; and a second inductor element coupled in parallel with the second acoustic resonator.

[0084] Aspect 8: A circulator according to any one of aspects 1 to 7, wherein the plurality of branches are arranged in a star configuration.

[0085] Aspect 9: A circulator according to any one of aspects 1 to 7, wherein the plurality of branches are arranged in a triangular configuration.

[0086] Aspect 10: A method for routing a signal in an electronic device supporting wireless communication. The method includes: using a circulator of the electronic device to route a first signal from a transmit link to an antenna, the circulator including a plurality of branches, each of the plurality of branches including: (i) a first acoustic resonator having a first series resonant frequency, (ii) a second acoustic resonator coupled in series with the first acoustic resonator and having a second series resonant frequency different from the first series resonant frequency, (iii) a first switching device coupled in parallel with the first acoustic resonator, and (iv) a second switching device coupled in parallel with the second acoustic resonator; and using the circulator to route a second signal from the antenna to a receive link.

[0087] Aspect 11: According to the method of aspect 10, wherein the first signal and the second signal are in a frequency band ranging from 7 GHz to 24 GHz.

[0088] Aspect 12: The method according to aspect 10 or 11, wherein using the circulator to route the first signal from the transmit link to the antenna or to route the second signal from the antenna to the receive link comprises: switching the first switching device and the second switching device in each of the plurality of branches alternately at a modulation frequency such that only the first acoustic resonator in each of the plurality of branches is bypassed during a first time interval, and only the second acoustic resonator in each of the plurality of branches is bypassed during a second time interval occurring after the first time interval.

[0089] Aspect 13: The method according to aspect 12, wherein the switching comprises: providing a first control signal and an inverted version of the first control signal to the first switching device and the second switching device respectively in a first branch of the plurality of branches; providing a second control signal and an inverted version of the second control signal to the first switching device and the second switching device respectively in a second branch of the plurality of branches, the second control signal being 120 degrees out of phase with the first control signal; and providing a third control signal and an inverted version of the third control signal to the first switching device and the second switching device respectively in a third branch of the plurality of branches, the third control signal being 240 degrees out of phase with the first control signal.

[0090] Aspect 14: An apparatus comprising: a transmit chain; a receive chain; an antenna; and a circulator, the circulator comprising: a first port coupled to the transmit chain; a second port coupled to the antenna; a third port coupled to the receive chain; and a plurality of branches coupled between the first port, the second port, and the third port, each of the plurality of branches comprising: a first acoustic resonator; a second acoustic resonator coupled in series with the first acoustic resonator; a first switching device coupled in parallel with the first acoustic resonator; and a second switching device coupled in parallel with the second acoustic resonator.

[0091] Aspect 15: The apparatus according to aspect 14, wherein the first acoustic resonator has a first series resonant frequency; and the second acoustic resonator has a second series resonant frequency different from the first series resonant frequency.

[0092] Aspect 16: The apparatus according to aspect 14 or 15, wherein the first acoustic resonator comprises a first bulk acoustic (BAW) resonator; and the second acoustic resonator comprises a second BAW resonator.

[0093] Aspect 17: The apparatus according to any one of aspects 14 to 16, wherein each of the plurality of branches further comprises: a first inductor element coupled in parallel with the first acoustic resonator; and a second inductor element coupled in parallel with the second acoustic resonator.

[0094] Aspect 18: The apparatus according to any one of aspects 14 to 17, wherein the first switching device and the second switching device are configured to be operated such that they bypass the first acoustic resonator and the second acoustic resonator alternately at the modulation frequency.

[0095] Aspect 19: The apparatus according to any one of aspects 14 to 18, wherein the first switching device of the first branch of the plurality of branches is configured to be controlled with a first phase offset relative to the first switching device of the second branch of the plurality of branches; the first switching device of the third branch of the plurality of branches is configured to be controlled with a second phase offset relative to the first switching device of the second branch of the plurality of branches; and the first phase offset is different from the second phase offset.

[0096] Aspect 20: The apparatus according to any one of aspects 14 to 19, wherein the plurality of branches are arranged in a star configuration such that a first branch of the plurality of branches is coupled between the first port and the common node, a second branch of the plurality of branches is coupled between the second port and the common node, and a third branch of the plurality of branches is coupled between the third port and the common node. in conclusion

[0097] This document describes a circulator comprising multiple branches, each branch including at least a first acoustic resonator and a second acoustic resonator coupled in series with the first acoustic resonator. The first and second acoustic resonators have different fixed frequencies (e.g., a first series resonant frequency and a second series resonant frequency). Each branch also includes a first switching device coupled in parallel with the first acoustic resonator and a second switching device coupled in parallel with the second acoustic resonator. The first and second switching devices can be switched to selectively bypass the first and second acoustic resonators, respectively. In this way, the circulator according to certain aspects of this disclosure does not require lossy and / or nonlinear circuitry elements required in conventional circulators to modify the resonant frequency of a single resonator. Furthermore, since the first and second switching devices are coupled in parallel with the first and second acoustic resonators, the first and second switching devices do not affect (e.g., reduce) the quality factor of the first and second acoustic resonators.

[0098] The above description provides examples and is not intended to limit the scope, applicability, or examples set forth in the claims. Changes may be made to the function and arrangement of the elements discussed without departing from the scope of this disclosure. Various processes or components may be omitted, substituted, or added as appropriate in various examples. For example, the described method may be performed in a different order than described, and various steps may be added, omitted, or combined. Furthermore, features described with respect to some examples may be combined in others. For example, any number of aspects set forth herein may be used to implement an apparatus or practice. Moreover, the scope of this disclosure is intended to cover such apparatus or methods practiced using structures, functionalities, or structures and functions other than or different from the various aspects of this disclosure set forth herein. It should be understood that any aspect of this disclosure disclosed herein may be embodied by one or more elements of these claims. The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects.

[0099] The various operations of the methods described above can be performed by any suitable component capable of performing the corresponding function. This component can include various hardware and / or software components and / or modules, including but not limited to circuits, application-specific integrated circuits (ASICs), or processors. Generally, in the presence of operations illustrated in the accompanying drawings, these operations can have corresponding components plus functional elements.

[0100] As used in this article, the phrase "at least one of" in a list of items refers to any combination of these items, including a single member. For example, " a , b or c "At least one of" is intended to cover: a , b , c , ab , ac , bc and abc and any combination having multiple identical elements (e.g., a - a , a - a - a , a - a - b , a - a - c , a - b - b , a - c - c , b - b , b - b - b , b - b - c , c - c and c - c - c or a , b and c (any other sorting).

[0101] The methods disclosed herein include one or more steps or actions for implementing the described methods. The steps and / or actions of the methods may be interchanged without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and / or use of a particular step and / or action may be modified without departing from the scope of the claims.

[0102] It should be understood that the claims are not limited to the precise configurations and components illustrated above. Various modifications, variations, and alterations may be made to the arrangement, operation, and details of the methods and apparatus described above without departing from the scope of the claims.

Claims

1. A looper, the looper comprising: Multiple branches, each of the multiple branches including: First acoustic resonator; The second acoustic resonator is coupled in series with the first acoustic resonator. A first switching device, the first switching device being coupled in parallel with the first acoustic resonator; and The second switching device is coupled in parallel with the second acoustic resonator.

2. The circulator according to claim 1, wherein: The first acoustic resonator has a first series resonant frequency; and The second acoustic resonator has a second series resonant frequency that is different from the first series resonant frequency.

3. The circulator according to claim 2, wherein: The first acoustic resonator includes a first bulk acoustic (BAW) resonator; and The second acoustic resonator includes a second BAW resonator.

4. The circulator according to claim 1, wherein: The first switching device is operable to selectively bypass the first acoustic resonator; The second switching device is operable to selectively bypass the second acoustic resonator; and The first switching device and the second switching device are configured to be operated such that they bypass the first acoustic resonator and the second acoustic resonator alternately at the modulation frequency.

5. The circulator according to claim 1, wherein: The first switching device of the first branch of the plurality of branches is configured to be controlled with a first phase offset relative to the first switching device of the second branch of the plurality of branches; The first switching device of the third branch of the plurality of branches is configured to be controlled with a second phase offset relative to the first switching device of the second branch of the plurality of branches; and The first phase offset is different from the second phase offset.

6. The circulator according to claim 1, wherein: The first switching device and the second switching device in the first branch of the plurality of branches are configured to receive a first control signal and the inverted version of the first control signal, respectively; The first switching device and the second switching device in the second branch of the plurality of branches are configured to receive the second control signal and the inverted version of the second control signal, respectively; The second control signal is 120 degrees out of phase with the first control signal; The first and second switching devices in the third branch of the plurality of branches are configured to receive a third control signal and the inverted version of the third control signal, respectively. and The third control signal is out of phase by 240 degrees relative to the first control signal.

7. The looper of claim 1, wherein each of the plurality of branches further comprises: The first inductor element is coupled in parallel with the first acoustic resonator. and The second inductor element is coupled in parallel with the second acoustic resonator.

8. The circulator of claim 1, wherein the plurality of branches are arranged in a star configuration.

9. The circulator of claim 1, wherein the plurality of branches are arranged in a triangular configuration.

10. A method for routing signals in an electronic device supporting wireless communication, the method comprising: The electronic device uses a circulator to route a first signal from a transmit link to an antenna. The circulator includes multiple branches, each of which includes: (i) a first acoustic resonator having a first series resonant frequency; (ii) a second acoustic resonator coupled in series with the first acoustic resonator and having a second series resonant frequency different from the first series resonant frequency; (iii) a first switching device coupled in parallel with the first acoustic resonator; and (iv) a second switching device coupled in parallel with the second acoustic resonator. The circulator is used to route the second signal from the antenna to the receiver chain.

11. The method of claim 10, wherein the first signal and the second signal are in a frequency band ranging from 7 GHz to 24 GHz.

12. The method of claim 10, wherein using the circulator to route the first signal from the transmit link to the antenna or to route the second signal from the antenna to the receive link comprises: The first switching device and the second switching device in each of the plurality of branches are switched alternately at the modulation frequency such that only the first acoustic resonator in each of the plurality of branches is bypassed during a first time interval, and only the second acoustic resonator in each of the plurality of branches is bypassed during a second time interval that occurs after the first time interval.

13. The method of claim 12, wherein the switching comprises: In the first branch of the plurality of branches, a first control signal and an inverted version of the first control signal are respectively provided to the first switching device and the second switching device; In the second branch of the plurality of branches, a second control signal and an inverted second control signal are respectively provided to the first switching device and the second switching device, wherein the second control signal is 120 degrees out of phase with the first control signal; as well as In the third branch of the plurality of branches, a third control signal and the inverse of the third control signal are provided to the first switch device and the second switch device, respectively, and the third control signal is out of phase with the first control signal by 240 degrees.

14. An apparatus comprising: Sending chain; Receive chain; antenna; and A looper, the looper comprising: A first port, the first port being coupled to the transmission chain; A second port, which is coupled to the antenna; A third port, said third port being coupled to the receiver chain; and Multiple branches, coupled between the first port, the second port, and the third port, each of the multiple branches comprising: First acoustic resonator; The second acoustic resonator is coupled in series with the first acoustic resonator. A first switching device, the first switching device being coupled in parallel with the first acoustic resonator; and The second switching device is coupled in parallel with the second acoustic resonator.

15. The apparatus according to claim 14, wherein: The first acoustic resonator has a first series resonant frequency; and The second acoustic resonator has a second series resonant frequency that is different from the first series resonant frequency.

16. The apparatus of claim 14, wherein: The first acoustic resonator includes a first bulk acoustic (BAW) resonator; and The second acoustic resonator includes a second BAW resonator.

17. The apparatus of claim 14, wherein each of the plurality of branches further comprises: The first inductor element is coupled in parallel with the first acoustic resonator. and The second inductor element is coupled in parallel with the second acoustic resonator.

18. The apparatus of claim 14, wherein the first switching device and the second switching device are configured to be operated such that they bypass the first acoustic resonator and the second acoustic resonator alternately at the modulation frequency.

19. The apparatus according to claim 14, wherein: The first switching device of the first branch of the plurality of branches is configured to be controlled with a first phase offset relative to the first switching device of the second branch of the plurality of branches; The first switching device of the third branch of the plurality of branches is configured to be controlled with a second phase offset relative to the first switching device of the second branch of the plurality of branches; and The first phase offset is different from the second phase offset.

20. The apparatus of claim 14, wherein the plurality of branches are arranged in a star configuration such that a first branch of the plurality of branches is coupled between the first port and the common node, a second branch of the plurality of branches is coupled between the second port and the common node, and a third branch of the plurality of branches is coupled between the third port and the common node.

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