Elastic wave device

Abstract

This invention discloses an elastic wave device, comprising: an antenna terminal, a bandpass filter having a specified frequency passband, and a bandstop filter having a specified frequency stopband. The bandstop filter includes a parallel resonator connected between a node between the antenna terminal and the bandpass filter and a ground terminal, and a ground inductor connected in series between the parallel resonator and the ground terminal. The combined circuit formed by the parallel resonator and the ground inductor has a first series resonant frequency between 1.9 and 2.4 times the center frequency of the passband, and a second series resonant frequency between 2.8 and 3.2 times the center frequency of the passband.

Description

Technical Field

[0001] This invention relates to the field of communications, and more specifically to an elastic wave device. Background Technology

[0002] With the widespread adoption of smartphones and other mobile communication terminals, the demand for elastic wave devices with functions such as duplexers is constantly increasing. These elastic wave devices not only need to be further miniaturized, but also, especially in transmit filters, require the ability to significantly attenuate the second and third harmonic components generated by power amplifiers.

[0003] Patent Document 1 (JP2012-501564A) discloses a method for improving the isolation between a duplexer and two filters. Specifically, this method couples the receiving filter to the antenna terminal in the duplexer using a band-stop filter, thereby separating the transmitting and receiving paths and improving the isolation of the duplexer. However, Patent Document 1 does not specifically disclose a technical solution for suppressing the second and third harmonic components generated by one of the filters, and therefore cannot effectively attenuate these higher harmonic components.

[0004] Patent Document 2 (JP2018-23044A) discloses a multiplexer that can be miniaturized and suppress unwanted spurious signals. This multiplexer includes a first filter and a notch filter circuit, the notch filter circuit having a stopband in a frequency range twice the passband of the first filter. Although Patent Document 2 discloses a method for suppressing second harmonics, it also does not specifically disclose a technical solution for suppressing the second and third harmonic components generated by one of the filters, thus failing to effectively attenuate these higher harmonic components. Summary of the Invention

[0005] The purpose of this invention is to provide an elastic wave device that can attenuate the second and third harmonic components of a bandpass filter while achieving miniaturization.

[0006] In some embodiments, the present invention provides an elastic wave device, comprising: an antenna terminal, a bandpass filter having a defined frequency passband, and a bandstop filter having a defined frequency stopband. The bandstop filter includes a parallel resonator connected between a node between the antenna terminal and the bandpass filter and a ground terminal, and a ground inductor connected in series between the parallel resonator and the ground terminal. The combined circuit formed by the parallel resonator and the ground inductor has a first series resonant frequency located between 1.9 and 2.4 times the center frequency of the passband, and a second series resonant frequency located between 2.8 and 3.2 times the center frequency of the passband.

[0007] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0008] The accompanying drawings, which are provided to further illustrate the invention and constitute a part of this invention, are illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention.

[0009] Figure 1 This is a cross-sectional view of the elastic wave device in Implementation Method 1.

[0010] Figure 2 This is an example diagram of the elastic wave element of the elastic wave device in Implementation Method 1.

[0011] Figure 3 This is a schematic diagram of the key components of the elastic wave device in Implementation Method 1.

[0012] Figure 4 This is a characteristic diagram of elastic wave device 1.

[0013] Figure 5 This is the MBVD equivalent circuit diagram of the parallel resonator BEFP and the circuit diagram of the ground inductor LS.

[0014] Figure 6 This is a characteristic diagram of another design example of the elastic wave device 1 in Implementation Method 1.

[0015] Figure 7 This is a schematic diagram of the key components of the elastic wave device in Implementation Method 2.

[0016] Figure 8 This is a characteristic diagram of the elastic wave device in Implementation Method 2.

[0017] Symbol explanation: 1. Elastic wave device 2 Packaging substrate 2A conductive pad 2B conductive pad 2C Internal Conductor 3. Chip substrate 3A wiring pattern 3B electrode 4 bumps 5. Sealing section 6 spaces 7. Elastic wave element 7AIDT electrode 7B reflector 7D electrode finger 7E busbar BEFP parallel resonator LS grounding inductor BEFS series resonator. Detailed Implementation

[0018] The embodiments will now be described with reference to the accompanying drawings. It should be noted that in the various drawings, the same or corresponding parts are labeled with the same reference numerals, and repeated descriptions of these parts will be appropriately simplified or omitted.

[0019] <Implementation Method 1> Figure 1 This is a cross-sectional view of the elastic wave device 1 in Embodiment 1.

[0020] like Figure 1 As shown, the elastic wave device 1 includes a packaging substrate 2, two chip substrates 3, multiple bumps 4, and a sealing part 5.

[0021] For example, the packaging substrate 2 is a multilayer substrate containing resin. For example, the packaging substrate 2 is a low-temperature co-fired ceramic (LTCC) multilayer substrate composed of multiple dielectric layers. For example, the packaging substrate 2 incorporates passive components such as capacitors or inductors (e.g., inductors).

[0022] exist Figure 1 In this package, the upper surface of the package substrate 2 is a mounting surface. Multiple conductive pads 2A are formed on the upper surface of the package substrate 2. For example, the multiple conductive pads 2A are formed of copper. The lower surface of the package substrate 2 is a mounting surface for mounting to a mother substrate, etc. Multiple conductive pads 2B are formed on the lower surface of the package substrate 2. For example, the multiple conductive pads 2B are formed of copper. Multiple internal conductors 2C are embedded in the package substrate 2. For example, the multiple internal conductors 2C are formed of copper. Each internal conductor 2C electrically connects its corresponding conductive pad 2A and conductive pad 2B. Furthermore, a grounding inductor LS is embedded in the package substrate 2. The grounding inductor LS is connected to the grounding pad Gnd.

[0023] Chip substrate 3 is mounted on packaging substrate 2. For example, chip substrate 3 is formed of piezoelectric single crystal such as lithium tantalate, lithium niobate, or quartz. For example, chip substrate 3 is formed of piezoelectric ceramic. For example, chip substrate 3 is formed by bonding piezoelectric substrate and support substrate. For example, support substrate is formed of sapphire, silicon, alumina, spinel, quartz, or glass.

[0024] For example, on the main surface of the two chip substrates 3 (on Figure 1 On the lower surface (the middle part), a transmitting filter and a receiving filter are formed respectively.

[0025] The transmitting filter is configured to allow electrical signals in the desired frequency band to pass through. For example, the transmitting filter includes a trapezoidal filter consisting of multiple series resonators and multiple parallel resonators.

[0026] The receiving filter is configured to allow electrical signals in the desired frequency band to pass through. For example, the receiving filter includes a trapezoidal filter composed of multiple series resonators and multiple parallel resonators.

[0027] In some embodiments, the chip substrate 3 includes a wiring pattern 3A and a plurality of electrodes 3B. For example, the plurality of electrodes 3B are interdigital transducer (IDT) electrodes composed of comb-shaped electrode fingers. The chip substrate 3Tx, which includes a transmit filter, as described later, includes a parallel resonator BEFP (in...) as a parallel resonator of a band-stop filter. Figure 1 (Not shown in the diagram). The parallel resonator BEFP is connected to the band-stop filter pad BP. The band-stop filter pad BP is connected to the ground inductor LS via bump 4 and conductive pad 2A.

[0028] Each of the plurality of bumps 4 is formed of gold, conductive adhesive, solder, etc. For example, the height of bump 4 is 20 μm to 50 μm. Each of the plurality of bumps 4 electrically connects the conductive pad 2A to the wiring pattern 3A at a corresponding position.

[0029] The sealing portion 5, while maintaining the space 6 between the packaging substrate 2 and the chip substrate 3, also provides an hermetically sealed seal to the chip substrate 3 together with the packaging substrate 2. For example, the sealing portion 5 is formed of an insulator such as a synthetic resin. The synthetic resin is epoxy resin, polyimide, etc.

[0030] Next, refer to Figure 2 This illustrates an example of elastic wave element 7. Figure 2 This is a schematic diagram of the elastic wave element of the elastic wave device in Embodiment 1.

[0031] exist Figure 2 In the diagram, elastic wave element 7 is a SAW (Surface Acoustic Wave) resonator. For example... Figure 2 As shown, a pair of IDT electrodes 7A and a pair of reflectors 7B are formed on the main surface of the chip substrate 3. The pair of IDT electrodes 7A and the pair of reflectors 7B are configured to excite surface elastic waves.

[0032] In some embodiments, the pair of IDT electrodes 7A and the pair of reflectors 7B are formed of an aluminum-copper alloy. In some embodiments, the pair of IDT electrodes 7A and the pair of reflectors 7B are formed of a suitable metal such as titanium, palladium, silver, or an alloy thereof. In some embodiments, the pair of IDT electrodes 7A and the pair of reflectors 7B are formed of a stacked metal film consisting of multiple metal layers.

[0033] IDT electrode 7A has multiple electrode fingers 7D and a busbar 7E. The multiple electrode fingers 7D are arranged along their long sides. The busbar 7E connects the multiple electrode fingers 7D in an opposing manner. One of a pair of reflectors 7B is adjacent to one side of the pair of IDT electrodes 7A. The other of the pair of reflectors 7B is adjacent to the other side of the pair of IDT electrodes 7A. For example, the pair of IDT electrodes 7A and the pair of reflectors 7B are connected via wiring pattern 3A (in... Figure 2 (Not shown in the figure) The same process is used for film formation and patterning.

[0034] Next, refer to Figure 3 The key parts of the elastic wave device in Implementation Method 1 are explained. Figure 3 This is a schematic diagram of the key components of the elastic wave device in Implementation Method 1.

[0035] like Figure 3 As shown, a trapezoidal filter constituting the transmit filter is formed on a chip substrate 3Tx containing the transmit filter. The trapezoidal filter includes multiple series resonators S1 to S4 and multiple parallel resonators P1 to P3. The transmit filter is, for example, an LTE Band 8 transmit filter with a passband of 880MHz to 915MHz.

[0036] On the chip substrate 3Tx containing the transmit filter, a parallel resonator BEFP constituting the band-stop filter BEF is formed. This parallel resonator BEFP has a resonant frequency higher than the passband of the transmit filter. Because the resonant frequency of the parallel resonator BEFP is higher than that of the transmit filter, it can be formed with a thinner film thickness than the IDT electrode film thickness of the resonator in the trapezoidal filter constituting the transmit filter. Using a thinner film thickness reduces mass, thereby increasing the sound velocity and allowing for sufficient resolution margin for fine patterns.

[0037] In the chip substrate 3Tx, the band-stop filter pad BP is not connected to any resonator other than the parallel resonator BEFP. That is, in the chip substrate 3Tx, the band-stop filter pad BP is only connected to the parallel resonator BEFP. The parallel resonator BEFP is connected to the ground inductor LS via the band-stop filter pad BP, bump 4, and conductive pad 2A.

[0038] The package substrate 2 includes a ground inductor LS that constitutes a band-stop filter BEF. The ground inductor LS is formed by a metal pattern within the package substrate 2. The metal pattern of the ground inductor LS can be patterned on only one layer within the package substrate 2, or it can be patterned across multiple layers. That is, the band-stop filter BEF is formed across the package substrate 2 and the chip substrate 3Tx.

[0039] At this point, the inductance value LS of the grounding inductor LS is set such that the first series resonant frequency of the combined circuit of the parallel resonator BEFP and the grounding inductor LS is 1.9 to 2.4 times the center frequency of the transmit filter passband, and the second series resonant frequency of the combined circuit of the parallel resonator BEFP and the grounding inductor LS is 2.8 to 3.2 times the center frequency of the transmit filter passband. In a specific example, the inductance value LS of the grounding inductor LS can be set to 2nH.

[0040] Figure 4 This is a characteristic diagram of the elastic wave device 1, where the vertical axis represents attenuation and the horizontal axis represents frequency. In this example, the first series resonant frequency m1 is 2.10 GHz, equivalent to 2.34 times the center frequency of the transmit filter's passband, and the second series resonant frequency m2 is 2.75 GHz, equivalent to 3.06 times the center frequency of the transmit filter's passband. It can be seen that by using only a band-stop resonator and an inductor, the attenuation of the elastic wave device 1 near the second and third harmonics can be significantly improved.

[0041] Next, refer to Figure 5 Explain the relationship between the capacitance and inductance values ​​of the parallel resonator BEFP and the grounding inductor LS. Figure 5 This is the MBVD equivalent circuit diagram of the parallel resonator BEFP and a schematic diagram of the ground inductance LS. The MBVD equivalent circuit is short for Modified Butterworth–Van Dyke equivalent circuit, a common equivalent circuit model for elastic wave devices. Note that for simplicity, the resistance component has been omitted here.

[0042] exist Figure 5 In this circuit, capacitors C0 and C1, along with inductor L1, constitute the MBVD equivalent circuit of the parallel resonator BEFP. The grounding inductor LS is connected between the parallel resonator BEFP and the ground terminal Gnd. In one specific embodiment, in the elastic wave device 1, the capacitance of capacitor C0 is set to 1.68 pF, the capacitance of capacitor C1 is set to 0.28 pF, the inductance of inductor L1 is set to 19.1 nH, and the inductance of grounding inductor LS is set to 2.0 nH.

[0043] At this point, when it is necessary to change the first series resonant frequency m1 and the second series resonant frequency m2 of the combined circuit of the parallel resonator BEFP and the ground inductor in order to set the attenuation electrode at any other frequency, or when the size of the parallel resonator BEFP needs to be changed due to chip substrate layout limitations, or the filter design method, the ground inductance value LS can be obtained in the following way: set the first series resonant frequency and the second series resonant frequency as FS1 and FS2 respectively, and use... Figure 5 The capacitance C0, capacitance C1, and inductance L1 in the MBVD equivalent circuit of the parallel resonator BEFP are determined according to the solution of the following simultaneous equations (1) and (2):

[0044] Therefore, spurious emissions from the elastic wave device 1 near the second and third harmonics can be effectively suppressed. Furthermore, it becomes easy to achieve a first series resonant frequency of the parallel resonator BEFP that is 1.9 to 2.4 times the center frequency of the transmit filter's passband, and a second series resonant frequency of the parallel resonator BEFP that is 2.8 to 3.2 times the center frequency of the transmit filter's passband.

[0045] Next, another design example of elastic wave device 1 will be described. Figure 6 This is a characteristic diagram of another design example of the elastic wave device 1 in Implementation Method 1, where the vertical axis represents the attenuation and the horizontal axis represents the frequency.

[0046] In another design example of the elastic wave device 1, the inductance value of the grounding inductor LS is set to 3nH, and the resonant frequency and capacitance C0 of the parallel resonator BEFP are optimized. The remaining structure is the same as... Figure 4 and Figure 5 The structure of the elastic wave device 1 shown is the same.

[0047] like Figure 6 As shown, in this design example, by setting the inductance value of the grounding inductor LS to 3nH, the first series resonant frequency M3 of the combined circuit of the parallel resonator BEFP and the grounding inductor LS becomes exactly twice the center frequency of the passband of the LTE Band 8 transmit filter (880MHz~915MHz), i.e., 1795MHz, and the second series resonant frequency M4 becomes exactly three times it, i.e., 2693MHz.

[0048] In other words, by setting the inductance value of the grounding inductor LS to 3nH, the center of the second and third harmonics of the LTE band 8 transmission passband can be made to correspond to the attenuation pole.

[0049] It can be seen that even in another design example of the elastic wave device 1, by using only a resonator for band-stop and an inductor, the attenuation of the second and third harmonics in the passband of the elastic wave device 1 can be greatly improved, and the spurious second and third harmonics generated by the power amplifier can be effectively suppressed.

[0050] As can be seen from the above-described embodiment 1, this disclosure can provide an elastic wave device that can efficiently attenuate the second and third harmonic components of a bandpass filter while achieving miniaturization.

[0051] <Implementation Method 2> Figure 7 This is a schematic diagram of the key components of the elastic wave device in Embodiment 2. It should be noted that parts that are the same as or correspond to those in Embodiment 1 are labeled with the same symbols, and their descriptions are omitted.

[0052] like Figure 7 As shown, the elastic wave device in Embodiment 2 has a series resonator BEFS constituting a band-stop filter BEF on a chip substrate 3Tx containing a transmitting filter. The series resonator BEFS is connected in series between the series resonator S4 of the trapezoidal filter constituting the transmitting filter and the antenna terminal ANT.

[0053] The series resonator BEFS has a resonant frequency higher than the passband of the transmitting filter. The series resonator BEFS also has an anti-resonant frequency higher than the first series resonant frequency of the combined circuit of the parallel resonator BEFP and the ground inductor LS, but lower than the second series resonant frequency. Because the resonant frequency of the series resonator BEFS is higher than that of the transmitting filter, it can be formed with a thinner film thickness than the resonator IDT electrode film thickness in the trapezoidal filter that constitutes the transmitting filter. Using a thinner film thickness reduces mass, thereby increasing the velocity of sound and allowing for sufficient resolution margin for fine patterns.

[0054] The anti-resonance frequency of the series resonator BEFS is 2.267 GHz. The other structures of the elastic wave device in Embodiment 2 are the same as another design example in Embodiment 1, therefore descriptions are omitted.

[0055] Figure 8 This is a characteristic diagram of the elastic wave device in Implementation Method 2. Figure 8 The vertical axis represents the attenuation. Figure 8 The horizontal axis represents frequency. For example... Figure 8As shown, the harmonic attenuation characteristics of the elastic wave device are improved. By setting the inductance value of the grounding inductor LS to 3nH, the first series resonant frequency M5 of the combined circuit of the parallel resonator BEFP and the grounding inductor LS is 1795MHz, and the second series resonant frequency M6 is 2693MHz. Furthermore, the anti-resonant frequency M7 of the series resonator BEFS is set to 2.267GHz. This demonstrates that while efficiently suppressing spurious emissions near the second and third harmonics of the elastic wave device, it also ensures attenuation between the second and third harmonics.

[0056] According to Embodiment 2 described above, this disclosure can provide an elastic wave device that, while achieving miniaturization, can efficiently attenuate the second and third harmonic components of a bandpass filter and ensure attenuation between the second and third harmonics.

[0057] Of course, the present invention is not limited to the embodiments described above, but includes all embodiments that can achieve the purpose of the present invention.

[0058] Furthermore, although several aspects of at least one implementation method have been described above, it should be understood that various modifications, alterations and improvements will readily come to mind for those skilled in the art.

[0059] These modifications, alterations, and improvements are intended to form part of this description and are included within the scope of the invention. It should be understood that embodiments of the methods and apparatus described herein are not limited to the structures and arrangements shown in the foregoing description or drawings. The methods and apparatus can be implemented in other ways and can be carried out or performed in various forms. Specific implementation examples are given for illustrative purposes only and are not intended to constitute limitation.

[0060] Furthermore, the expressions and terms used herein are for illustrative purposes only and should not be considered limiting. The terms "comprising," "including," "possessing," "having," and variations thereof, as used herein, should be understood to cover the listed items and their equivalents, as well as additional items. References to "or" should be understood as any one, any combination of, or all of the listed items. Descriptions of directions such as front / back, left / right, up / down, and horizontal / vertical are for ease of description only and do not imply that the components of the invention are limited to a specific location or spatial orientation. Therefore, the above descriptions and drawings are merely illustrative.

Claims

1. An elastic wave device, comprising: An antenna terminal, a bandpass filter having a specified frequency passband, and a bandstop filter having a specified frequency stopband, characterized in that: The band-stop filter includes a parallel resonator connected between a node between the antenna terminal and the band-pass filter and a ground terminal, and a ground inductor connected in series between the parallel resonator and the ground terminal; The combined circuit formed by the parallel resonator and the grounding inductor has a first series resonant frequency between 1.9 and 2.4 times the center frequency of the passband, and a second series resonant frequency between 2.8 and 3.2 times the center frequency of the passband.

2. The elastic wave device according to claim 1, characterized in that: It also includes a piezoelectric substrate and a packaging substrate, wherein the multiple resonators constituting the bandpass filter and the parallel resonators are surface elastic wave resonators formed on the piezoelectric substrate, and the grounding inductor is a metal pattern formed on the packaging substrate.

3. The elastic wave device according to claim 1 or 2, characterized in that: The band-stop filter also includes a series resonator connected between the antenna terminal and the band-pass filter.

4. The elastic wave device according to claim 3, characterized in that: The series resonator has a resonant frequency higher than the specified frequency passband.

5. The elastic wave device according to claim 3, characterized in that: The series resonator has an anti-resonance frequency that is higher than the first series resonant frequency of the combined circuit formed by the parallel resonator BEFP and the ground inductor, and lower than the second series resonant frequency.

6. The elastic wave device according to claim 3, characterized in that: The thickness of the comb electrode of the series resonator is less than the thickness of the multiple resonators constituting the bandpass filter.

7. The elastic wave device according to claim 1 or 2, characterized in that: When the parallel resonator is represented by the MBVD equivalent circuit model, the model includes: a dynamic branch consisting of a first inductor L1 and a first capacitor C1 connected in series, and a parallel capacitor C0 connected in parallel with the dynamic branch. When the first series resonant frequency is FS1 and the second series resonant frequency is FS2, the grounding inductor LS is a value that satisfies the following equations (1) and (2): 。 8. The elastic wave device according to claim 1 or 2, characterized in that: The thickness of the comb electrode of the parallel resonator is less than the thickness of the multiple resonators constituting the bandpass filter.

9. The elastic wave device according to claim 1 or 2, characterized in that: The bandpass filter is a transmitting filter, and it also includes a receiving filter formed on the packaging substrate.

10. The elastic wave device according to claim 1 or 2, characterized in that: It also includes pads for blocking filters, which are not connected to resonators other than the parallel resonators.

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