Acoustic Resonator Filter System

Abstract

An example includes an acoustic resonator filter system. The system includes a plurality of filter blocks. Each of the plurality of filter blocks may include a plurality of tunable filter elements. Each of the plurality of tunable filter elements may include an acoustic resonator. The system also includes a switching network that receives a radio frequency (RF) input signal and provides a filtered RF output signal. The switching network may be configured to selectively switch at least one of the plurality of filter blocks into a signal path of the RF input signal to provide the RF output signal.

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates generally to communications, and more particularly, to acoustic resonator filter systems. [Background technology]

[0002] Resonator circuits are implemented in a variety of different types of applications, such as for filtering frequency ranges. There are a variety of different types of resonators. One such type of resonator is an acoustic resonator that utilizes acoustic waves on an integrated circuit (IC). Acoustic resonators include bulk acoustic wave (BAW) resonators and standing acoustic wave (SAW) resonators. Acoustic wave resonators are designed to confine acoustic energy within the resonator to increase the quality factor (Q) of the resonator. As an example, a conventional acoustic resonator can provide effective filtering in a narrow band (e.g., about + / - 5 dB) around a center frequency. Summary of the Invention

[0003] An example includes an acoustic resonator filter system. The system includes a plurality of filter blocks. Each of the plurality of filter blocks may include a plurality of tunable filter elements. Each of the plurality of tunable filter elements may include an acoustic resonator. The system also includes a switching network that receives a radio frequency (RF) input signal and provides a filtered RF output signal. The switching network may be configured to selectively switch at least one of the plurality of filter blocks into a signal path of the RF input signal to provide the RF output signal.

[0004] Another example includes a method for filtering an RF input signal through an acoustic resonator filter system. The method includes providing an RF input signal to a switching network of the acoustic resonator filter system and providing a plurality of switching signals to the switching network to selectively switch at least one of a plurality of filter blocks into a signal path of the RF input signal. Each of the plurality of filter blocks may include a plurality of tunable filter elements. Each of the plurality of tunable filter elements may include an acoustic resonator. The method further includes providing an RF output signal from an output of the switching network. The RF output signal may correspond to the RF input signal provided through the filter blocks selectively switched into the signal path.

[0005] Another example includes an integrated circuit (IC) comprising an acoustic resonator filter system. The acoustic resonator filter system may include a plurality of filter blocks. Each of the plurality of filter blocks may include a plurality of tunable filter elements. Each of the plurality of tunable filter elements may include an acoustic resonator in parallel with a capacitive network. The capacitive network may include a varactor. The method further includes a switching network capable of receiving an RF input signal and providing a filtered RF output signal. The switching network may be configured to selectively switch at least one of the plurality of filter blocks into a signal path of the RF input signal to provide the RF output signal. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a block diagram of an example acoustic resonator filter system. [Diagram 2] FIG. 2 is a circuit diagram of an example filter block. [Diagram 3] FIG. 1 illustrates an example communication transceiver system. [Figure 4] FIG. 2 illustrates an example method for filtering an RF input signal through an acoustic resonator filter system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] The present disclosure relates generally to communications, and more particularly to an acoustic resonator filter system. The acoustic resonator filter system may be implemented in various communications systems, such as in a transmit path and / or a receive path of a wireless transceiver. The acoustic resonator filter system includes a plurality of filter blocks. Each of the plurality of filter blocks includes a plurality of tunable filter elements, each of which includes an acoustic resonator and a capacitive network. As an example, the acoustic resonator may be configured as a combined overtone resonator (COR). As another example, the capacitive network may include a varactor disposed in parallel with the acoustic resonator and in parallel with a capacitance capacitor to provide tuning functionality for the plurality of tunable filter elements. The varactor may be provided with a control voltage to set a capacitance of the plurality of tunable filter elements of each of the plurality of filter blocks.

[0008] The acoustic resonator filter system also includes a switching network configured to receive a switching signal to selectively switch one or more of the plurality of filter blocks into a signal path of a radio frequency (RF) input signal to provide an RF output signal. The switching network may include a plurality of sets of superlattice castellated gate field effect transistor (SLCFET) switches to accommodate a wide range of frequencies of the RF input signal. Thus, each set of switches may provide a bypass node in the signal path of the RF input signal in a first state and a respective one of the plurality of filter blocks in the signal path of the RF input signal in a second state. Thus, the switching network may be implemented to selectively provide one or more different filter blocks into the signal path of the RF input signal in response to the plurality of switching signals.

[0009] 1 illustrates a block diagram of an example of an acoustic resonator filter system 100. The acoustic resonator filter system may be implemented in a variety of communication systems, such as in the transmit and / or receive paths of a wireless transceiver. As described herein, the acoustic resonator filter system, in the example of FIG. 1, filters a signal RF IN The input filter 100 may provide passband filtering of a radio frequency (RF) input signal, denoted as 100 kHz, over a wide spectrum with a wide bandwidth.

[0010] The acoustic resonator filter system includes a plurality of N filter blocks 102, where N is a positive integer. Each of the plurality of filter blocks 102 includes a plurality of tunable filter elements 104. In the example of FIG. 1, each of the plurality of tunable filter elements 104 includes an acoustic resonator 106 and a capacitive network 108. As an example, the acoustic resonator 106 can be configured as a coupled harmonic resonator (COR), and the capacitive network 108 can include a varactor. In the example of FIG. 1, the capacitive network 108 of each of the plurality of tunable filter elements 104 is coupled to a voltage V TN_1 ~V TN_N Therefore, the control voltage V TN_1 ~V TN_N can set the capacitance of the varactor of the capacitive network 108 of each of the tunable filter elements 104. As an example, the varactor of the capacitive network 108 can be placed in parallel with the acoustic resonator 106 and in parallel with a capacitance capacitor.

[0011] As an example, each of the plurality of tunable filter elements 104 may be manufactured substantially identically and may be in the same quantity in each of the plurality of filter blocks 102. Thus, the plurality of control voltages V TN_1 ~V TN_N can provide the tuning function for the multiple tunable filter elements 104 and thus for each of the multiple filter blocks 102. As a first example, multiple control voltages VTN_1 ~V TN_N can each have a distinct amplitude and provide different capacitances for the multiple capacitive networks 108 of the multiple tunable filter elements 104. As a second example, multiple control voltages V TN_1 ~V TN_N may each have approximately equal amplitude, and as described in more detail herein, the filter characteristics of the acoustic resonator filter system 100 may be set based on selectively placing multiple filter blocks 102 in the signal path of the RF input signal. TN_1 ~V TN_N Each of the control voltages V can represent a set of different amplitude voltages, further enhancing the tuning capability of each of the multiple capacitive networks 108 in each of the multiple tunable filter elements 104. TN_1 ~V TN_N can be static or programmable, allowing for greater control over the filter characteristics of acoustic resonator filter system 100.

[0012] The acoustic resonator filter system 100 also receives an RF input signal RF IN and receiving an RF output signal RF corresponding to the filtered RF input signal. OUT The switching network 110 is configured to provide as an output a RF input signal RF IN Selectively switch the RF output signal to the RF OUT Thus, in a first state, each set of switches in the switching network 110 is controlled by a set of switching signals SW to provide an RF input signal RF IN In a second state, a bypass node can be provided in the signal path of the RF input signal RF IN A separate one of a number of filter blocks 102 may be provided in the signal path of the

[0013] In the example of FIG. 1, a particular one of the filter blocks 102 is configured to filter the signal RF passing through the particular filter block 102. IN_1 ~RF IN_N As shown by the RF input signal RF IN is passed through a separate filter block 102, IN As an example, the switching network 110 may be provided as part of a signal path for a wide range of frequencies of an RF input signal, RF IN The switching network may include a plurality of sets of super lattice castellated gate field effect transistor (SLCFET) switches to accommodate an RF input signal RF. Thus, the switching network may be responsive to a plurality of switching signals SW to selectively connect one or more different filter blocks to an RF input signal RF. IN and selectively providing an RF input signal RF IN Sets the selective filtering characteristics of the RF output signal, RF OUT It may be implemented to provide:

[0014] Based on the arrangement of multiple filter blocks 102 comprised of multiple tunable filter elements 104, the acoustic resonator filter system 100 reduces the RF input signal RF IN For example, a typical filter system implementing an acoustic resonator can achieve a bandwidth of less than 5%. However, the acoustic resonator filter system 100 can exhibit excellent filtering characteristics for an RF input signal, RF IN The acoustic resonator filter system 100 can operate at high frequencies, such as up to about 40 GHz, and with a variable bandwidth and tuning range of up to about 33% of the center frequency. As an example, the acoustic resonator filter system 100 can be fabricated on an integrated circuit (IC) having a significantly smaller form factor relative to conventional acoustic resonator filters. Furthermore, the selective tuning of the capacitive network 108 in each of the multiple tunable filter elements and the RF input signal RFIN Based on the selective switching of multiple filter blocks 102 in the signal path, the acoustic resonator filter system 100 can operate as either a bandpass filter, a lowpass filter, a highpass filter or a notch filter with highly tunable filter characteristics.

[0015] 2 shows a circuit diagram 200 of an example of a filter block 202. The filter block 202 may correspond to any one of the filter blocks 102 in the example of FIG. 1. As described in more detail herein, the filter block 202 may correspond to an Xth block of the N filter blocks 102. Accordingly, in the following description of the example of FIG. 2, reference is made to the example of FIG. 1.

[0016] The filter block 202 includes a plurality of Y tunable filter elements 204, where Y is a positive integer. Each of the plurality of tunable filter elements 204 includes an acoustic resonator 206, a capacitor C S , and a variable capacitor (varactor) C V The acoustic resonator 206 includes, in the example of FIG. R1 and inductor L R 1, and a first capacitor C R1 and inductor L R The series arrangement of the second capacitor C R2 The circuit configuration of the acoustic resonator 206 can represent the operating characteristics of the acoustic resonator 206. For example, the first capacitor C R1 , the second capacitor C R2 , and inductor L R The value of may be based on the physical characteristics of the acoustic resonator 206 (e.g., the dimensions of the substrate). S and C V may correspond to the capacitive network 108 in the example of FIG.

[0017] As an example, the acoustic resonator 206 may be configured as a COR (e.g., an aluminum nitride (AlN) COR). Thus, the acoustic resonator 206 receives an RF input signal RF IN The COR may exhibit a high quality factor (Q) at frequencies both above and below a particular frequency range (e.g., Ka band). For example, the COR may operate in a Q range of about 400 to about 1000. Additionally, acoustic resonator 206 configured as a COR may be configured to receive an RF input signal RF IN A shape factor selectivity of about 1.03 can be provided to substantially reject out-of-band components and interferences. Such selectivity can achieve about 60 dB of attenuation at about 50 MHz on either side of the 3.5 GHz bandwidth, thus providing significantly greater attenuation than conventional acoustic resonator filters (e.g., which exhibit a selectivity of about 1.5).

[0018] Acoustic resonator 206, capacitor C S , and varactor C V The parallel arrangement of the varactors C in each of the tunable filter elements 204 can provide significantly improved filter characteristics over conventional filters. V is the varactor C V The control voltage V for setting the capacitance TN_X As an example, the control voltage V TN_X may be approximately the same amplitude for each of the tunable filter elements 204 in the filter block 202. As another example, the control voltage V TN_X may vary among the tunable filter elements 204 within the filter block 202.

[0019] For example, a capacitor C in parallel with the acoustic resonator 206 S and C V The split capacitance provided by the varactor C can provide the ability to continuously tune the tunable filter element 204 over a wide frequency range with minimal impact on the quality factor Q and insertion loss. Vcan be configured as a barium strontium titanate (BST) varactor, which allows a tuning range of up to about 33%, with a loss tangent of about 0.006 and a quality factor Q of about 40 at a frequency of about 18 GHz. Thus, a capacitor C in parallel with the acoustic resonator 206 S and C V The split capacitor configuration can provide a wide range of frequency tuning without degradation in performance of the acoustic resonator filter system 100 .

[0020] As an example, acoustic resonator 206 may be formed within a substrate of an associated IC in which acoustic resonator filter system 100 is fabricated, but the capacitor C S and C V may be arranged as a surface mounted component of an associated IC. For example, the associated IC may include acoustic resonator 206 and capacitor C S and C V Therefore, the RF input signal RF IN The insertion loss associated with the acoustic resonator 206 and the capacitor C may be mitigated in each of the filter blocks 102. For example, the insertion loss may vary as a percentage of the bandwidth of the acoustic resonator filter system 100, such as about 5 dB for a 3% bandwidth, about 2.5 dB for a wider bandwidth, etc. S and C V can be manufactured on a common substrate manufacturing design.

[0021] In the example of Figure 2, each of the plurality of tunable filter elements 204 is disposed between a filter path node 208 and a low voltage rail, shown as ground in the example of Figure 2. Each of the plurality of filter path nodes 208 is connected to a capacitor C FP_1 ~C FP_Y+1 2. Thus, the filter path capacitor C FP_1 ~C FP_Y+1is one more than the Y tunable filter elements 204. The filter path node 208 and the filter path capacitor C FP_1 ~C FP_Y+1 is the first switch S 1_X and the second switch S 2_X The switch S is located between 1_X and S 2_X are a pair of switching signals SW 1_X and S.W. 2_X 1, each of which is controlled by a respective one of the switches in the switching network 110.

[0022] First switch S 1_X receives an RF input signal as an input and switches a second switch S 2_X provides an RF input signal as an output. In the example of FIG. 2, an RF input signal RF IN is the RF input signal RF of the Xth filter block 202 IN The signal RF represents the filtering effect on IN_X In the first state, the switching signal SW 1_X and S.W. 2_X is a separate switch S 1_X and S 2_X can be configured to couple to each other via bypass node 210. Thus, in the first state, switch S 1_X and S 2_X The bypass node is connected to the RF input signal, RF IN As a result, the tunable filter element 204 is provided as part of the signal path of the switch S 1_X and S 2_X In the first state, the switch S 1_X and S 2_X In a first state, the tunable filter element 204 receives the RF input signal RF IN It provides no filtering effect.

[0023] In the second state, the switching signal SW 1_X and S.W. 2_Xis a separate switch S 1_X and S 2_X 208 and a filter path capacitor CF P_1 ~CF P_Y+1 Thus, in the second state, the switch S 1_X and S 2_X The filter block 202 is connected to the RF input signal RF IN As a result, the plurality of tunable filter elements 204 are provided as part of the signal path of the control voltage V TN_X In response to the varactor C V Based on the variable tuning of the switch S 1_X and S 2_X In the second state, the RF input signal RF IN Provides a filtering effect.

[0024] The filter block 202 may correspond to a single filter block 102 of the acoustic resonator filter system 100. Thus, based on the sets of switching signals SW provided to the switching network 110, each of the multiple filter blocks 102 may be selectively configured to provide a bypass node and one of the tunable filter elements 104 as part of the signal path of the RF input signal RF, in a manner similar to that described above for the filter block 202 in the example of FIG. IN , based on the independent filter characteristics of the filter block 102, and / or based on the signal path of the RF input signal RF IN Based on the number of filter blocks 102 provided in the signal path of the RF input signal RF IN to provide a collective contribution to the filtering of the filtered RF output signal RF OUT may be provided.

[0025] 3 illustrates an example communications transceiver system 300. The communications transceiver system 300 may be implemented in any of a variety of wireless communications systems that may communicate in high and wide frequency bands.

[0026] The communication transceiver system 300 includes a transmit path 302 and a receive path 304. The transmit path 302 includes a digital waveform generator (WFG) 306 configured to generate a digital signal. The digital signal is provided to a digital-to-analog converter (DAC) 308 configured to convert the digital signal to an analog signal. The analog signal is provided to a signal conditioner 310 configured to perform signal conditioning (e.g., amplification, attenuation, analog processing, etc.) on the analog signal. The conditioned analog signal is provided to an acoustic resonator filter system 312. The acoustic resonator filter system 312 may be configured substantially similar to the acoustic resonator filter system 100 in the example of FIG. 1. Thus, the acoustic resonator filter system 312 may include multiple filter blocks each arranged similarly to the filter block 202 in the example of FIG. 2. Thus, the acoustic resonator filter system 312 may provide highly tunable and effective filtering of the conditioned analog signal. The filtered and conditioned analog signal is provided to a power amplifier (PA) 314 for amplification before being transmitted from an antenna 316 in a transmission mode set by a TX / RX switching system 318 .

[0027] The receive path 304 includes a low-noise amplifier (LNA) 320 that receives and amplifies an analog receive signal from the antenna 316 via the TX / RX switching system 318 in a receive mode. The amplified analog signal is provided to an acoustic resonator filter system 322, which may also be configured substantially similar to the acoustic resonator filter system 100 in the example of FIG. 1. Thus, the acoustic resonator filter system 322 may include multiple filter blocks each arranged similarly to the filter block 202 in the example of FIG. 2. Thus, the acoustic resonator filter system 322 may provide highly tunable and effective filtering of the amplified analog receive signal. The filtered analog receive signal is provided to a signal conditioner 324 configured to perform signal conditioning (e.g., amplification, attenuation, analog processing, etc.) on the filtered analog receive signal. The conditioned and filtered analog receive signal is provided to an analog-to-digital converter (ADC) 326 configured to convert the conditioned and filtered analog receive signal to a digital receive signal. Accordingly, the digital received signal is provided to a digital filter 328 configured to process the digital received signal.

[0028] In view of the above structural and functional features described above, methods according to various embodiments of the present disclosure may be better understood by reference to Figure 4. It should be understood and appreciated that, in accordance with the present disclosure, some embodiments may be performed in a different order and / or simultaneously with other embodiments than as illustrated and described herein, and therefore the method of Figure 4 is not limited by the order illustrated. Furthermore, not all illustrated features are required to practice a method according to an embodiment of the present example.

[0029] FIG. 4 illustrates a radio frequency (RF) input signal (e.g., RF input signal RF ) passing through an acoustic resonator filter system (e.g., acoustic resonator filter system 100). IN4 illustrates an example method 400 for filtering an RF input signal (e.g., RF output signal RF 110). At 402, an RF input signal is provided to a switching network (e.g., switching network 110) of an acoustic resonator filter system. At 404, a plurality of switching signals (e.g., switching signal SW) are provided to the switching network to selectively switch at least one of a plurality of filter blocks (e.g., filter block 102) into a signal path of the RF input signal. Each of the plurality of filter blocks may include a plurality of tunable filter elements (e.g., a plurality of tunable filter elements 104). Each of the plurality of tunable filter elements may include an acoustic resonator (e.g., acoustic resonator 106). At 406, an RF output signal (e.g., RF output signal RF 110) is provided to the switching network to selectively switch at least one of a plurality of filter blocks (e.g., filter block 102) into a signal path of the RF input signal. Each of the plurality of filter blocks may include a plurality of tunable filter elements (e.g., tunable filter elements 104). Each of the plurality of tunable filter elements may include an acoustic resonator (e.g., acoustic resonator 106). OUT ) is provided from the output of the switching network. The RF output signal may correspond to the RF input signal provided through a filter block selectively switched into the signal path.

[0030] The above are examples of the present invention. Of course, it is not possible to describe every conceivable combination of elements or methods for purposes of describing the present invention, but one skilled in the art will recognize that many more combinations and permutations of the present invention are possible. Accordingly, the present invention is intended to embrace all such changes, modifications, and variations that fall within the spirit and scope of the appended claims. In addition, when the disclosure or claims recite "a," "an," "a first," or "another" element, or the equivalent thereof, it should be construed as including one or more such elements, and does not require or exclude two or more such elements. As used herein, the term "includes" means including but not limited to, and the term "including" means including but not limited to. The term "based on" means based at least in part on.

Claims

1. 1. An acoustic resonator filter system, comprising: a plurality of filter blocks, each of the plurality of filter blocks including a plurality of tunable filter elements, each of the plurality of tunable filter elements including an acoustic resonator; a switching network that receives a radio frequency (RF) input signal and provides a filtered RF output signal, the switching network being configured to selectively switch at least one of the plurality of filter blocks into a signal path of the RF input signal to provide the RF output signal.

2. The system of claim 1 , wherein each of the plurality of tunable filter elements includes the acoustic resonator in parallel with a capacitive network.

3. The system of claim 2 , wherein the capacitive network includes a varactor in parallel with a fixed capacitance capacitor.

4. 4. The system of claim 3, wherein the varactor of each of the plurality of tunable filter elements is provided with a control voltage to set a capacitance of the capacitive network of each of the plurality of tunable filter elements.

5. The system of claim 1 , wherein the acoustic resonators are arranged as coupled harmonic resonators.

6. 2. The system of claim 1 , wherein the plurality of tunable filter elements are respectively disposed between a respective plurality of filter path nodes and a low voltage rail, and each of the plurality of filter blocks further includes a plurality of filter path capacitors connected between each of the plurality of filter path nodes.

7. 7. The system of claim 6, wherein the switching network is configured to switch each of the plurality of filter blocks to provide a signal path through a bypass node in a first state and to provide a signal path through the plurality of filter path nodes and the plurality of filter path capacitors in a second state.

8. 2. The system of claim 1, wherein the switching network comprises a plurality of superlattice castellated gate field effect transistor (SLCFET) switches configured to selectively switch at least one of the plurality of filter blocks into a signal path of the RF input signal to provide the RF output signal.

9. 10. An integrated circuit (IC) comprising the acoustic resonator filter system of claim 1.

10. A communications transceiver system comprising a transmit path and a receive path, each of the transmit path and the receive path including the acoustic resonator filter system of claim 1 .

11. 1. A method for filtering a radio frequency (hereinafter RF) input signal through an acoustic resonator filter system, comprising: providing the RF input signal to a switching network of the acoustic resonator filter system; providing a plurality of switching signals to the switching network to selectively switch at least one of a plurality of filter blocks into a signal path of the RF input signal, each of the plurality of filter blocks including a plurality of tunable filter elements, each of the plurality of tunable filter elements including an acoustic resonator; providing an RF output signal from an output of the switching network, wherein the RF output signal corresponding to the RF input signal is provided through a filter block selectively switched into the signal path.

12. 12. The method of claim 11, wherein each of the plurality of tunable filter elements includes the acoustic resonator in parallel with a capacitive network, the capacitive network including a varactor in parallel with a fixed capacitance capacitor.

13. The method of claim 11 , wherein the acoustic resonators are arranged as coupled harmonic resonators.

14. 12. The method of claim 11 , wherein the plurality of tunable filter elements are respectively disposed between a respective plurality of filter path nodes and a low voltage rail, each of the plurality of filter blocks further including a plurality of filter path capacitors connected between each of the plurality of filter path nodes, and wherein providing the plurality of switching signals comprises providing the plurality of switching signals to selectively provide a signal path through a bypass node of a given one of the plurality of filter blocks in a first state and a signal path through the plurality of filter path nodes and the plurality of filter path capacitors of the given one of the plurality of filter blocks in a second state.

15. 12. The method of claim 11, wherein providing the plurality of switching signals comprises providing the plurality of switching signals to each of a plurality of superlattice castellated gate field effect transistor (SLCFET) switches configured to selectively switch at least one of the plurality of filter blocks into a signal path of the RF input signal.

16. 1. An integrated circuit (IC) comprising an acoustic resonator filter system, the acoustic resonator filter system comprising: a plurality of filter blocks, each of the plurality of filter blocks including a plurality of tunable filter elements, each of the plurality of tunable filter elements including an acoustic resonator in parallel with a capacitive network, the capacitive network including a varactor; a switching network configured to receive a radio frequency (RF) input signal and provide a filtered RF output signal, the switching network configured to selectively switch at least one of the plurality of filter blocks into a signal path of the RF input signal to provide the RF output signal.

17. The system of claim 16 , wherein the acoustic resonators are arranged as coupled harmonic resonators.

18. 17. The system of claim 16, wherein each of the plurality of tunable filter elements is disposed between a respective plurality of filter path nodes and a low voltage rail, and each of the plurality of filter blocks further includes a plurality of filter path capacitors connected between each of the plurality of filter path nodes.

19. 20. The system of claim 18, wherein the switching network is configured to switch each of the plurality of filter blocks to provide a signal path through a bypass node in a first state and to provide a signal path through the plurality of filter path nodes and the plurality of filter path capacitors in a second state.

20. 2. The system of claim 1, wherein the switching network comprises a plurality of superlattice castellated gate field effect transistor (SLCFET) switches configured to selectively switch at least one of the plurality of filter blocks into a signal path of the RF input signal to provide the RF output signal.

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