Acoustic matrix filter and radio using acoustic matrix filter

Abstract

Acoustic filters and radio devices including acoustic filters are disclosed. The filter includes a first filter port, a second filter port, and n sub-filters, where n is an integer greater than one. Each sub-filter has a first sub-filter port connected to the first filter port, and a second sub-filter port. The second sub-filter port of at least one sub-filter is connected to the second filter port. A first acoustic wave resonator is connected from the first filter port to ground, and a second acoustic wave resonator is connected from the second filter port to ground. The first and second acoustic wave resonators are configured to create respective transmission zeros near a lower edge of a passband of the filter.

Description

Technical Field

[0001] This disclosure relates to radio frequency filters using acoustic resonators, and more particularly to filters used in communication devices. Background Technology

[0002] Radio frequency (RF) filters are two-ended devices configured to allow some frequencies to pass while blocking others. "Passing" means transmitting with relatively low signal loss, while "blocking" means blocking or essentially attenuating the signal. The range of frequencies a filter can pass through is called its "passband." The range of frequencies blocked by such a filter is called its "stopband." A typical RF filter has at least one passband and at least one stopband. The specific requirements for the passband or stopband depend on the application. For example, a "passband" can be defined as a frequency range where the filter's insertion loss is better than defined values ​​such as 1 dB, 2 dB, or 3 dB. A "stopband" can be defined as a frequency range where the filter's rejection is greater than defined values, such as 20 dB, 30 dB, 40 dB, or greater, depending on the application.

[0003] RF filters are used in communication systems that transmit information over wireless links. For example, RF filters can be found in cellular base stations, mobile phones and computing devices, satellite transceivers and ground stations, Internet of Things (IoT) devices, laptops and tablets, fixed-point radio links, and the RF front end of other communication systems. RF filters are also used in radar and electronic and information warfare systems.

[0004] RF filters typically require numerous design trade-offs to achieve the optimal balance between performance parameters such as insertion loss, rejection, isolation, power handling, linearity, size, and cost for each specific application. Specific design and manufacturing approaches and enhancements can simultaneously benefit one or more of these requirements.

[0005] Enhancements to the performance of RF filters in wireless systems can have a wide-ranging impact on system performance. Improvements to RF filters can lead to improvements such as larger cell size, longer battery life, higher data rates, greater network capacity, lower cost, enhanced security, and higher reliability. These improvements can be implemented individually or in combination at various levels of the wireless system, such as at the RF module, RF transceiver, mobile or fixed subsystem, or network level.

[0006] High-performance RF filters used in current communication systems typically include acoustic resonators, which include surface acoustic wave (SAW) resonators, bulk acoustic wave (BAW) resonators, thin-film bulk acoustic wave resonators (FBAR), and other types of acoustic resonators. However, these existing technologies are not well-suited for use at higher frequencies, which are proposed for use in future communication networks.

[0007] To obtain wider communication channel bandwidth, higher frequency communication bands are necessary. 3GPP (3rd Generation Partnership Project) has standardized radio access technologies for mobile phone networks. The 5G NR (New Radio) standard defines radio access technologies for fifth-generation mobile networks. The 5G NR standard defines several new communication bands. Among these new bands are n77 and n79, where n77 uses a frequency range of 3300 MHz to 4200 MHz, and n79 uses a frequency range of 4400 MHz to 5000 MHz. Both bands n77 and n79 use Time Division Duplex (TDD), therefore, communication devices operating in bands n77 and / or n79 will use the same frequencies for uplink and downlink transmissions. Bandpass filters in bands n77 and n79 must be able to handle the transmit power of the communication devices. High frequencies and wireless bandwidth are also required in the 5GHz and 6GHz 5G bands. The 5G NR standard also defines millimeter wave communication bands between 24.25 GHz and 40 GHz.

[0008] The transversely excited film bulk acoustic resonator (XBAR) is an acoustic resonator structure used in microwave filters. Such an XBAR is described in U.S. Patent 10,491,291, entitled "TRANSVERSELY EXCITED FILM BULK ACOUSTIC RESONATOR". The XBAR resonator includes an interdigital transducer (IDT) formed on a thin floating layer or diaphragm of a single-crystal piezoelectric material. The IDT includes a first set of parallel fingers extending from a first busbar and a second set of parallel fingers extending from a second busbar. The first and second sets of parallel fingers are interleaved. A microwave signal applied to the IDT excites a sheared master acoustic wave in the piezoelectric diaphragm. The XBAR resonator provides high electromechanical coupling and high-frequency capability. XBAR resonators can be used in a variety of RF filters, including band-stop filters, band-pass filters, duplexers, and multiplexers. XBARs are particularly well-suited for use in filters in communication bands above 3 GHz. The matrix XBAR filter is also suitable for frequencies between 1 GHz and 3 GHz. Attached Figure Description

[0009] Figure 1Includes a schematic plan view of a transversely excited thin-film bulk acoustic resonator (XBAR), two schematic cross-sectional views, and one detailed cross-sectional view.

[0010] Figure 2A It is the equivalent circuit model of an acoustic resonator.

[0011] Figure 2B This is the admittance diagram of an ideal acoustic resonator.

[0012] Figure 2C It is the circuit symbol for an acoustic resonator.

[0013] Figure 3A This is a schematic diagram of a matrix filter that uses an acoustic resonator.

[0014] Figure 3B yes Figure 3A A schematic diagram of the sub-filter.

[0015] Figure 4 yes Figure 3A A graph showing the performance of an embodiment of the filter.

[0016] Figure 5 yes Figure 4 A graph showing the input-output transfer functions of each sub-filter in the embodiment.

[0017] Figure 6 This is a schematic diagram of a matrix duplexer using an acoustic resonator.

[0018] Figure 7 yes Figure 6 A diagram of the input-output transfer function of an embodiment of a duplexer.

[0019] Figure 8 This is a schematic diagram of a matrix multiplexer that uses acoustic resonators.

[0020] Figure 9 yes Figure 8 A graph of the input-output transfer function of an embodiment of a multiplexer.

[0021] Figure 10A This is a schematic diagram of a reconfigurable matrix filter that uses an acoustic resonator.

[0022] Figure 10B yes Figure 10A A schematic diagram of the sub-filters and switching modules.

[0023] Figure 11 yes Figure 10A The input-output transfer function diagrams for two configurations of an embodiment of a reconfigurable matrix filter are shown.

[0024] Figure 12This is a schematic block diagram of a Time Division Duplex (TDD) radio device.

[0025] Figure 13 This is a schematic block diagram of a frequency division duplex (FDD) radio device.

[0026] Throughout the specification, elements appearing in the accompanying drawings are assigned three- or four-digit reference numerals, where the two least significant digits are unique to that element, and one or two most significant digits are the drawing number in which the element is first shown. Elements not described in conjunction with the accompanying drawings may be assumed to have the same characteristics and functions as previously described elements with the same reference numerals. Detailed Implementation

[0027] Component Description

[0028] Figure 1 A simplified schematic top view, orthogonal cross-sectional view, and detailed cross-sectional view of a laterally excited thin-film bulk acoustic resonator (XBAR) 100 are shown. XBAR resonators, such as resonator 100, can be used in a variety of RF filters, including band-stop filters, band-pass filters, duplexers, and multiplexers. XBARs are well-suited for use in communication frequency bands above 3 GHz. The matrix XBAR filter described in this patent is also suitable for frequencies above 1 GHz.

[0029] XBAR 100 consists of a thin-film conductor pattern formed on the surface of a piezoelectric plate 110, which has parallel front and back faces 112 and 114. The piezoelectric plate is a thin single-crystal layer made of a piezoelectric material, such as lithium niobate, lithium tantalate, lanthanum gallium silicate, gallium nitride, or aluminum nitride. The piezoelectric plate is cut such that the orientations of the X, Y, and Z crystal axes are known and consistent with the front and back faces. The piezoelectric plate can be Z-cut (i.e., the Z-axis is perpendicular to the front and back faces 112 and 114), rotated Z-cut, or rotated YX-cut. XBARs can be fabricated on piezoelectric plates with other crystal orientations.

[0030] The back surface 114 of the piezoelectric plate 110 is attached to the surface of the substrate 120, except for a portion of the piezoelectric plate 110 that is not attached to the surface of the substrate 120. This portion of the piezoelectric plate 110 forms a diaphragm 115, which spans a cavity 140 formed in the substrate. The portion of the piezoelectric plate 110 that spans the cavity is referred to herein as the "diaphragm" 115 because this portion is physically similar to the diaphragm of a microphone. Figure 1 As shown, the diaphragm 115 is adjacent to the remainder of the piezoelectric plate 110 around the entire periphery 145 of the cavity 140. In this case, "adjacent" means "continuous connection without any other items in between". In other configurations, the diaphragm 115 is adjacent to the piezoelectric plate around at least 50% of the periphery 145 of the cavity 140.

[0031] Substrate 120 provides mechanical support for piezoelectric plate 110. Substrate 120 can be, for example, silicon, sapphire, quartz, or some other material, or a combination of these materials. Wafer bonding processes can be used to bond the back surface 114 of piezoelectric plate 110 to substrate 120. Alternatively, piezoelectric plate 110 can be grown on substrate 120, or attached to the substrate in some other way. Piezoelectric plate 110 can be directly attached to the substrate, or it can be attached via one or more intermediate material layers (…). Figure 1 (Not shown in the image) is attached to substrate 120.

[0032] The conventional meaning of "cavity" is "an empty space within a solid". Cavity 140 can be a hole that passes completely through substrate 120 (as shown in cross sections AA and BB), or it can be a groove in substrate 120 below diaphragm 115. For example, cavity 140 can be formed by selectively etching substrate 120 before or after attaching piezoelectric plate 110 to substrate 120.

[0033] The conductor pattern of XBAR100 includes an interdigital transducer (IDT) 130. IDT 130 includes a first plurality of parallel fingers, such as fingers 136, extending from a first busbar 132. IDT 130 also includes a second plurality of fingers extending from a second busbar 134. The first and second plurality of parallel fingers are staggered. The staggered fingers overlap by a distance AP, which is commonly referred to as the “aperture” of the IDT. The center-to-center distance L between the outermost fingers of IDT 130 is the “length” of the IDT.

[0034] The first and second buses 132 and 134 serve as terminals of the XBAR 100. An radio frequency or microwave signal applied between the two buses 132 and 134 of the IDT 130 excites the primary acoustic mode within the piezoelectric plate 110. The primary acoustic mode of the XBAR is a bulk shear mode, in which acoustic energy propagates in a direction substantially perpendicular to the surface of the piezoelectric plate 110, which is also perpendicular or transverse to the direction of the electric field generated by the IDT fingers. Therefore, the XBAR is considered a transversely excited thin-film bulk resonator.

[0035] IDT 130 is placed on piezoelectric plate 110 such that at least the fingers of IDT 130 are positioned on diaphragm 115 of piezoelectric plate, spanning or suspended over cavity 140. For example... Figure 1 As shown, the cavity 140 is rectangular, and the size of the rectangle is greater than the aperture AP and the length L of IDT 130. The cavity of the XBAR can have different shapes, such as regular or irregular polygons. The cavity of the XBAR can have more or fewer four sides, which can be straight or curved.

[0036] A detailed cross-sectional view (detail C) shows two IDT fingers 136a and 136b on the surface of piezoelectric plate 110. Dimension p is the “pitch” of the IDTs and dimension w is the width or “mark” of the IDT fingers. A dielectric layer 150 may be formed between the IDT fingers and optionally on top of them (see IDT finger 136a). The dielectric layer 150 may be a non-piezoelectric dielectric material, such as silicon dioxide or silicon nitride. The dielectric layer 150 may be formed from multiple layers of two or more materials. IDT fingers 136a and 136b may be aluminum, copper, beryllium, gold, tungsten, molybdenum, their alloys and combinations, or some other conductive material. Thin layers (relative to the total thickness of the conductors) of other metals (such as chromium or titanium) may be formed below and / or above the fingers to improve adhesion between the fingers and piezoelectric plate 110 and / or passivate or encapsulate the fingers and / or increase power capacity. The busbars of the IDT130 can be made of the same or different materials as the fingers.

[0037] To facilitate Figure 1 As shown, the geometric spacing and width of the IDT fingers are significantly enlarged relative to the length (dimension L) and aperture (dimension AP) of the XBAR. A typical XBAR in an IDT 110 has more than ten parallel fingers. A single XBAR in an IDT 110 may have hundreds of parallel fingers. Similarly, the thickness of the IDT fingers is significantly enlarged in the cross-sectional view.

[0038] XBARs based on shear wave resonators can outperform state-of-the-art surface acoustic wave (SAW), thin-film bulk acoustic wave (FBAR), and solid-state assembled bulk acoustic wave (SMR BAW) devices. In particular, the piezoelectric coupling of shear wave XBAR resonators can be very high (>20%) compared to other acoustic wave resonators. High-voltage piezoelectric coupling allows for the design and implementation of various types of microwave and millimeter-wave filters with considerable bandwidth.

[0039] The basic behavior of acoustic resonators, including XBAR, is typically used as follows: Figure 2A The Butterworth van Dyke (BVD) circuit model shown is used to describe this. The BVD circuit model consists of a moving arm and a stationary arm. The moving arm includes a dynamic inductor L. m Dynamic capacitor C m and resistance R m The static arm includes static capacitance C0 and resistance R0. Although the BVD model cannot fully describe the behavior of acoustic resonators, it plays a good role in modeling the two primary resonators used for designing bandpass filters, duplexers, and multiplexers (multiplexers are filters with two or more input or output ports with multiple passbands).

[0040] The first primary resonance in the BVD model is caused by the dynamic inductance L. m and dynamic capacitance C m The dynamic resonance is caused by the series combination. The second primary resonance in the BVD model is caused by the dynamic inductance L. m Dynamic capacitor C m The anti-resonance caused by the combination of the static capacitor C0 and the lossless resonator (R) m In the case of R0 = 0), the frequency F of dynamic resonance is... r Given by the following formula

[0041] (1)

[0042] The frequency F of the anti-resonance a Given by the following formula

[0043] (2)

[0044] Where γ = C0 / C m It depends on the resonator structure and the type and orientation of the piezoelectric material's crystal axis.

[0045] Figure 2B Figure 200 shows the admittance amplitude of a theoretically lossless acoustic resonator. The acoustic resonator exhibits resonance at a resonant frequency where the admittance approaches infinity. Resonance is due to... Figure 2A Dynamic inductance L in the BVD model m and dynamic capacitance C m This is caused by the series combination. The acoustic resonator exhibits anti-resonance when the resonator's admittance is close to zero. 214. The anti-resonance is caused by the dynamic inductance L. m Dynamic capacitor C m This is caused by the combination of the static capacitance C0. In a lossless resonator (R... m In the case of R0 = 0), the resonant frequency F r Given by the following formula

[0046] (1)

[0047] The frequency F of the anti-resonance a Given by the following formula

[0048] (2)

[0049] In overly simplified terms, a lossless acoustic resonator can be considered as a short circuit at the resonant frequency 212 and an open circuit at the anti-resonant frequency 214. Figure 2B The resonance and anti-resonance in the model are representative, and acoustic resonators can be designed for other frequencies.

[0050] Figure 2CThe circuit symbol for an acoustic resonator, such as an XBAR, is shown. This symbol will be used to designate each acoustic resonator in the filter schematics in subsequent figures.

[0051] Figure 3A This is a schematic diagram of a matrix filter 300 using an acoustic resonator. The matrix filter 300 includes an array 310 of n sub-filters 320-1, 320-2, 320-n connected in parallel between a first filter port (FP1) and a second filter port (FP2), where n is an integer greater than 1. The sub-filters 320-1, 320-2, 320-n have consecutive passbands, such that the bandwidth of the matrix filter 300 is equal to the sum of the bandwidths of the constituent sub-filters. In a later example of this patent, n = 3. n can be less than or greater than 3 as needed to provide the required bandwidth for the matrix filter 300.

[0052] The sub-filter array 310 is terminated at both ends by acoustic resonators XL1, XL2, XH1, and XH2, which are preferably, but not necessarily, XBARs. Acoustic resonators XL1, XL2, XH1, and XH2 generate “transmission zeros” at their respective resonant frequencies. A “transmission zero” is the frequency at which the filter’s input-output transfer function is very low (zero if the acoustic resonators XL1, XL2, XH1, and XH2 are lossless). Typically, XL1 and XL2 have the same resonant frequency, and XH1 and XH2 have the same resonant frequency. The resonant frequencies of acoustic resonators XL1 and XL2 are chosen to provide transmission zeros near the lower edge of the filter’s passband. Acoustic resonators XL1 and XL2 also function as parallel inductors, which helps to match the impedance at the filter ports to the desired impedance value. In a later example of this patent, the impedance at all ports of the filter is matched to 50 ohms. Choose the resonant frequencies of acoustic resonators XH1 and XH2 to provide transmission zeros at or above the higher edge of the filter passband. Not all matrix filters require acoustic resonators XH1 and XH2.

[0053] Figure 3BThis is a schematic diagram of a sub-filter 350 applicable to sub-filters 320-1, 320-2, and 320-n. Sub-filter 350 includes three acoustic resonators X1, X2, and X3 connected in series between a first sub-filter port (SP1) and a second sub-filter port (SP2). The acoustic resonators X1, X2, and X3 are preferably, but not necessarily, XBARs. Sub-filter 350 includes two coupling capacitors C1 and C2, each connected between ground and a corresponding node between two acoustic resonators. The inclusion of three acoustic resonators in sub-filter 350 is illustrative. A sub-filter can have m acoustic resonators, where m is an integer greater than 1. A sub-filter with m acoustic resonators includes m-1 coupling capacitors. The m acoustic resonators of the sub-filter are connected in series between the two ports SP1 and SP2 of the sub-filter, and each of the m-1 coupling capacitors is connected between ground and a node between a corresponding pair of acoustic resonators from the m acoustic resonators.

[0054] Compared to other types of acoustic resonators, XBARs exhibit very high electromechanical coupling (leading to a significant difference between the resonant and anti-resonant frequencies) but low capacitance per unit area. Matrix filter architectures, as shown in Figures 3A and 3B, utilize the high electromechanical coupling of XBARs without requiring high resonator capacitance.

[0055] Figure 4 Figure 400 shows the performance of an exemplary matrix filter implemented using XBAR for all acoustic resonators. Specifically, solid line 410 is a graph of the filter's transfer function S21 from FP1 to FP2 as a function of frequency. Dashed line 420 is a graph of the return loss at S11 and FP1 as a function of frequency. Since the exemplary filter is symmetrical, solid line 410 and dashed line 420 are also graphs of S12 and S22. Figure 3A and Figure 3B As shown, the matrix filter comprises three sub-filters, each consisting of three XBARs. In this example and all subsequent examples, the filter performance is determined by simulating the filter using a BVD model of the XBARs (Figure 2A).

[0056] Table 1 provides the characteristics of the components of the matrix filter. Each XBAR is defined by its resonant frequency Fr and static capacitance C0. It is assumed that the Q of each XBAR is 1000. It is assumed that γ is 2.5, representing a lithium niobate XBAR. The same assumptions and component values ​​are used in all subsequent examples in this patent.

[0057] Table 1

[0058]

[0059] The exemplary matrix filter is symmetrical because the impedance at both port 1 and port 2 is equal to 50 ohms. The internal circuitry of the filter is also symmetrical; XBARs X1 and X3 are identical within each sub-filter, XL1 and XL2 are identical, and XH1 and XH2 are identical. A matrix filter can be designed to have significantly different impedances at port 1 and port 2; in this case, the internal circuitry will be asymmetrical.

[0060] Figure 5 Its performance is Figure 4 The diagram shows the characteristic plots of the components within an exemplary matrix filter. Specifically, solid line 510, dashed line 520, and dashed line 530 are amplitude plots of the input-output transfer functions of sub-filter 1, sub-filter 2, and sub-filter 3, respectively.

[0061] The input-output transfer function of an exemplary filter, such as Figure 4 The diagram shows the vector sum of the input-output transfer functions of three sub-filters. For this purpose, the input-output transfer functions of sub-filter 1 and sub-filter 2 cross at a frequency where (a) the S21 of both filters is essentially equal to -3 dB and (b) the phases of the input-output transfer functions of the two filters are essentially equal. In this context, "essentially equal" means sufficiently equal to avoid causing unpleasant variations in the insertion loss of the matrix filter within the filter passband. The value of "essentially equal" may vary for different filter applications. Similar requirements apply to sub-filters 2 and 3. In matrix filters with more than three sub-filters, similar requirements apply to each adjacent (frequency-wise) pair of sub-filters.

[0062] The vertical dotted lines indicate the resonant frequencies of the XBARs within the exemplary matrix filter. The line marked "XL" indicates the resonant frequencies of resonators XL1 and XL2, adjacent to the lower edge of the filter passband. Similarly, the line marked "XH" indicates the resonant frequencies of resonators XH1 and XH2, adjacent to the upper edge of the filter passband. The two lines marked "SF1" indicate the resonant frequencies of the separate XBARs within sub-filter 1. Note that both resonant frequencies are below the center of the passband. This is because the resonant frequencies of the series-connected resonators and capacitors are higher than the resonant frequencies of the separate resonators. Similarly, the two lines marked "SF2" indicate the resonant frequencies of the XBARs within sub-filter 2, and the two lines marked "SF3" indicate the resonant frequencies of the XBARs within sub-filter 3.

[0063] Figure 6This is a schematic diagram of a matrix filter 600 configured as a duplexer. The matrix filter 600 includes an array 610 of three sub-filters 620-1, 620-2, and 620-n. Sub-filter 1 620-1 is connected between the first filter port (FP1) and the second filter port (FP2). Sub-filters 2 620-2 and 3 620-3 are connected in parallel between FP1 and the third filter port (FP3). FP1 is the common port of the duplexer, and FP2 and FP3 are branch ports. As previously described, the two ends of the sub-filter array 610 are terminated by XBAR XL and XH.

[0064] Figure 7 yes Figure 6 Figure 700 shows the performance of an example of a matrix filter duplexer 600. In this example, XL, XH, and three sub-filters are connected to... Figure 3A The corresponding components of the matrix filter 300 are the same. Figure 7 In the diagram, solid line 710 is a graph of the FP1 to FP2 transfer function S21 according to frequency variation. Dashed line 720 is a graph of the FP1 to FP3 transfer function S31 according to frequency variation. Since the exemplary filter is symmetrical, solid line 710 and dashed line 720 are also graphs of S12 and S13, respectively. Matrix filter 600 is exemplary.

[0065] In most applications, a duplexer will have the same number (two, three or more) of sub-filters connected in parallel between the common port and the two branch ports.

[0066] FP1 can be considered as the common port of the matrix filter duplexer 600. FP2 can be considered as the "low-band" port and FP3 can be considered as the "high-band" port. When the matrix filter duplexer is used for frequency division duplex radio, one of FP2 and FP3 can be the receive port of the duplexer, and the other of FP2 and FP3 can be the transmit port of the duplexer, depending on the frequencies allocated for reception and transmission.

[0067] Figure 8This is a schematic diagram of a matrix filter 800 configured as a multiplexer. The matrix filter 800 includes an array 810 of three sub-filters 820-1, 820-2, and 820-n. Sub-filter 1 820-1 is connected between the first filter port (FP1) and the second filter port (FP2). Sub-filter 2 820-2 is connected between FP1 and the third filter port (FP3). Sub-filter 3 820-3 is connected between FP1 and the fourth filter port (FP4). As previously mentioned, the sub-filter array 810 is terminated at both ends by XBAR XL and XH. FP1 is the common port of the multiplexer, and FP2, FP3, and FP4 are branch ports of the multiplexer. A multiplexer may have more than three branch ports.

[0068] Figure 9 yes Figure 8 Figure 900 shows the performance of an example of a matrix filter multiplexer 800. In this example, XL, XH, and three sub-filters are used with... Figure 3A The corresponding components of the matrix filter 300 are the same. Figure 9 In the diagram, solid line 910 is a graph of the transfer function S21 from FP1 to FP2 with varying frequency. Dashed line 920 is a graph of the transfer function S31 from FP1 to FP3 with varying frequency. Dashed line 930 is a graph of the transfer function S41 from FP1 to FP4 with varying frequency. Since the exemplary filter is symmetrical, solid line 910, dashed line 920, and dashed line 930 are also graphs of S12, S13, and S14, respectively.

[0069] Figure 10A This is a schematic diagram of a reconfigurable matrix filter 1000 using XBARs. The reconfigurable matrix filter 1000 includes an array 1010 of n sub-filter / switch circuits 1020-1, 1020-2, 1020-n connected in parallel between a first filter port (FP1) and a second filter port (FP2), where n is an integer greater than 1. In the following example, n = 3. n can be greater than 3 as needed to provide the required bandwidth for the reconfigurable matrix filter 1000. Each sub-filter / switch circuit acts as a bandpass filter that can be selectively enabled (i.e., connected between FP1 and FP2) or disabled (i.e., not connected between FP1 and FP2). As previously described, the array 1010 of sub-filter / switch circuits is terminated at both ends by XBARs XL and XH.

[0070] Sub-filter / switch circuits 1020-1, 1020-2, and 1020-n have continuous passbands, such that the bandwidth of the matrix filter 1000 is equal to the sum of the bandwidths of the constituent sub-filters when all sub-filter / switch modules are enabled. One or more sub-filter / switch circuits can be disabled to customize the matrix filter bandwidth or to insert notches or stopbands throughout the passband.

[0071] Figure 10B It is applicable Figure 10A A schematic diagram of sub-filter / switch circuit 1050 of sub-filter / switch circuits 1020-1, 1020-2, and 1020-n is shown. Sub-filter / switch circuit 1050 includes three acoustic resonators X1, X2, and X3 connected in series between the first sub-filter port (SP1) and the second sub-filter port (SP2), and also includes coupling capacitors C1 and C2 grounded from the nodes between adjacent acoustic resonators. Including three acoustic resonators in sub-filter / switch circuit 1050 is exemplary, and sub-filter / switch circuits may have more than three acoustic resonators. When a sub-filter / switch circuit includes more than three acoustic resonators, the number of coupling capacitors will be one less than the number of acoustic resonators. Acoustic resonators X1, X2, and X3 are preferably, but not necessarily, XBARs.

[0072] The sub-filter / switch circuit 1050 includes a switch SW connected in series with the acoustic resonator X2. When the switch SW is closed, the sub-filter / switch circuit operates as a sub-filter suitable for any of the previous examples. When the switch SW is open, the sub-filter / switch circuit presents appropriate impedances to SP1 and SP2, but has an open-circuit input-output transfer function. When the sub-filter / switch circuit includes more than three acoustic resonators, the switch can be connected in series with any acoustic resonator except the two acoustic resonators connected to the two sub-filter ports. In other words, the switch can be connected in series with any "middle acoustic resonator" in the middle of the resonator string, but not with the two "end acoustic resonators" at the ends of the string.

[0073] Figure 11 Figure 1100 shows an example performance diagram of the reconfigurable matrix filter duplexer 1000 from Figure 10. In this example, the components within XL, XH, and the three sub-filter / switch circuits are... Figure 3A The corresponding components of the matrix filter 300 are the same. Figure 11In the diagram, solid line 1130 is a graph of the port 1-port 2 transfer function S21 of the filter as the frequency varies when sub-filter / switch circuit 1 is enabled and sub-filter / switch circuits 2 and 3 are disabled. Dashed line 1110 is a graph of S21 as the frequency varies when sub-filter / switch circuit 3 is enabled and sub-filter / switch circuits 1 and 2 are disabled. The sum of the two curves 1110 and 1130 (not shown but easily imagined) is the port 1-port 2 transfer function as the frequency varies when sub-filter / switch circuits 1 and 3 are enabled and sub-filter / switch circuit 2 is disabled. A total of eight different filter configurations are possible through various combinations of enabling the three sub-filter / switch circuits.

[0074] Figure 12 This is a schematic block diagram of a Time Division Duplex (TDD) radio device 1200. TDD radios transmit and receive on the same frequency channel within a designated communication band. Radio device 1200 includes a matrix bandpass filter 1210 having a first filter port FP1 configured to connect to an antenna 1205 and a second filter port FP2 coupled to a transmit / receive (T / R) switch 1215. The T / R switch 1215 connects the second port of the matrix bandpass filter 1210 to the output of a transmitter 1220 or the input of a receiver 1225. The T / R switch 1215, transmitter 1220, and receiver 1225 are monitored by a processor 1230 performing media access control functions. Specifically, the processor 1230 controls the operation of the T / R switch 1215, and when the matrix bandpass filter 1210 is reconfigurable, the processor 1230 can control the operation of switches within the bandpass filter. Antenna 1205 may be part of radio device 1200 or external to radio device 1200.

[0075] Radio equipment 1200 is configured to operate within a designated communication frequency band. A matrix bandpass filter 1210 has a passband encompassing the designated communication frequency band and one or more stopbands to block designated frequencies outside the designated communication frequency band. Preferably, the bandpass filter 1210 has low loss in its passband and high suppression in its stopband. Furthermore, the bandpass filter 1210 must be compatible with TDD operation; that is, the bandpass filter 1210 must be stable and reliable when passing the RF power generated by transmitter 1220. The matrix bandpass filter 1210 can be... Figure 3A Matrix filter 300 or Figure 10A A reconfigurable matrix filter 1000 is implemented using an acoustic resonator that can be XBAR.

[0076] The matrix bandpass filter 1210 can be as follows: Figure 10AThe reconfigurable matrix filter is shown. The use of a reconfigurable filter allows the filter bandwidth to be reduced to a single channel or group of channels within a specified communication band. This can reduce interference from other radio devices communicating in the same communication band. When the matrix bandpass filter 1210 is reconfigurable, the switches within the sub-filters can be controlled by process 1230.

[0077] Figure 13 This is a schematic block diagram of a frequency division duplex (FDD) radio device 1300. An FDD radio device transmits and receives within different frequency ranges having defined communication bands. The transmit and receive frequency ranges are typically, but not necessarily, adjacent. Radio device 1300 includes an antenna 1305; a matrix filter duplexer 1310 having a common filter port FP1 configured to be connected to the antenna 1305; a transmit filter port FP3 coupled to the output of a transmitter 1320; and a receive filter port FP2 coupled to the input of a receiver 1325.

[0078] Radio device 1300 is configured to operate in a specified communication frequency band. Matrix filter duplexer 1310 includes a receive filter coupled between FP1 and FP2 and a transmit filter coupled between FP1 and FP3. The receive filter may include one or more receive sub-filters. The transmit filter may include one or more transmit sub-filters. The transmit filter must be compatible with the RF power generated by transmitter 1320. Matrix filter duplexer 1310 can be implemented using an acoustic resonator, which may be an XBAR.

[0079] The matrix filter duplexer 1310 can be used with Figure 6 Similar to the matrix duplexer 600, it has the same number of sub-filters in both the transmit and receive filters. The common filter port of the matrix filter duplexer 1310 can be FP1 of the matrix duplexer 600, which can be port 1 of the duplexer 600. The transmit port TP can be one of FP2 or FP3, and the receive port RP can be the other of FP2 and FP3.

[0080] Conclusion

[0081] Throughout this specification, the embodiments and examples shown should be considered as examples and not as limitations on the disclosed or claimed devices and processes. While many of the examples provided herein relate to specific combinations of method actions or system elements, it should be understood that those actions and elements can be combined in other ways to achieve the same objective. Regarding the flowcharts, additional and fewer steps may be taken, and the steps shown may be combined or further refined to implement the methods described herein. Actions, elements, and features discussed in connection with only one embodiment are not intended to exclude their similarity in other embodiments.

[0082] As used herein, “multiple” means two or more. As used herein, a “group” of items may include one or more such items. As used herein, whether in the written description or in the claims, the terms “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” etc., shall be understood as open-ended, i.e., referring to including but not limited to. Only the transitional phrases “consisting of…” and “substantially consisting of…” are closed or semi-closed transitional phrases relative to the claims. Ordinal numbers used in the claims, such as “first,” “second,” “third,” etc., are used to modify claim elements. This does not in itself indicate the priority, order, or sequence of action of one claim element over another, but is merely used to distinguish one claim element with the same name from another element with the same name (but with ordinal numbers), thereby differentiating claim elements. As used herein, “and / or” means that the listed items are alternatives, but alternatives also include any combination of the listed items.

Claims

1. A filter, comprising: First filter port and second filter port; There are n sub-filters, where n is an integer greater than 1, and each of the n sub-filters has a first sub-filter port and a second sub-filter port; A first acoustic resonator is connected between the first filter port and ground; and A second acoustic resonator is connected between the second filter port and ground, wherein The first sub-filter port of each of the n sub-filters is connected to the first filter port. The second sub-filter port of at least one of the n sub-filters is connected to the second filter port, and The first acoustic resonator and the second acoustic resonator are configured to create their respective transmission zeros at the lower edge of the passband of the adjacent filter.

2. The filter according to claim 1, characterized in that, Each of the n sub-filters includes: m acoustic resonators are connected in series between the first sub-filter port and the second sub-filter port, where m is an integer greater than 1; and m-1 capacitors, each capacitor is connected between ground and a node between a corresponding pair of acoustic resonators from m acoustic resonators.

3. The filter according to claim 2, characterized in that, The m acoustic resonators in each of the n sub-filters are laterally excited thin-film bulk acoustic resonators (XBARs).

4. The filter according to claim 2, characterized in that, Each of the n sub-filters comprises m acoustic resonators, including: a first end acoustic resonator connected to a port of the first sub-filter; a second end acoustic resonator connected to a port of the second sub-filter; and one or more intermediate acoustic resonators connected between the first end acoustic resonator and the second end acoustic resonator. Each of the n sub-filters also includes a switch connected in series with one of the one or more intermediate acoustic resonators.

5. The filter according to claim 1, characterized in that, The first acoustic resonator and the second acoustic resonator are laterally excited thin-film bulk acoustic resonators (XBAR).

6. The filter according to claim 1, characterized in that, The second sub-filter port of all n sub-filters is connected to the second filter port.

7. The filter according to claim 6, characterized in that, The passband of the filter is equal to the sum of the passbands of the n sub-filters.

8. The filter according to claim 6, characterized in that, Also includes: A third acoustic resonator is connected between the first filter port and ground; and A fourth acoustic resonator is connected between the second filter port and ground, wherein The third and fourth acoustic resonators are configured to create transmission zeros near the upper edge of the passband of the filter.

9. The filter according to claim 8, characterized in that, The third and fourth acoustic resonators are laterally excited thin-film bulk acoustic resonators (XBAR).

10. The filter according to claim 1, characterized in that, Also includes: A third filter port, in which The n sub-filters include one or more low-frequency band sub-filters and one or more high-frequency band sub-filters. The second sub-filter port of the one or more low-frequency band sub-filters is connected to the second filter port, and The second sub-filter port of the one or more high-frequency band sub-filters is connected to the third filter port.

11. The filter according to claim 10, characterized in that, Also includes: A third acoustic resonator is connected between the first filter port and ground; and A fourth acoustic resonator is connected between the third filter port and ground, wherein The third and fourth acoustic resonators are configured to create transmission zeros near the upper edge of the passband of the filter.

12. The filter according to claim 11, characterized in that, The third and fourth acoustic resonators are laterally excited thin-film bulk acoustic resonators (XBAR).

13. A time-division duplex wireless device, comprising: The filter as described in claim 6; One transmitter; One receiver; and A transmitter / receiver switch for selectively connecting the second filter port to one of the output of the transmitter and the input of the receiver.

14. The time-division duplex wireless device according to claim 13, characterized in that, Also includes: The antenna is connected to the port of the first filter.

15. A frequency division duplex wireless device, comprising: The filter as described in claim 10; A receiver having an input terminal connected to one of the second filter port and the third filter port; and A transmitter having an output terminal connected to another of the second filter port and the third filter port.

16. The frequency division duplex wireless device according to claim 15, characterized in that, Also includes: The antenna is connected to the port of the first filter.

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