Surface acoustic wave filter with elongated strip structure

Abstract

Disclosed is a surface acoustic wave filter having an elongated strip structure, including an interdigital electrode, a bus bar, an input port configured to receive an input signal and to transmit the signal to the output port through the bus bar and the interdigital electrode, an output port configured to receive the input signal through the bus bar and the interdigital electrode, at least two ground ports configured to transmit the signal to the ground port through the bus bar and the interdigital electrode, and the elongated strip structure. The at least two ground ports are configured to be connected to one of the input port or the output port through the bus bar and the interdigital electrode; and the extension strip structure is configured to communicate with one of the at least two ground ports and extend toward the other of the at least two ground ports outside a region including the interdigital electrode and the bus bar.

Description

Technical Field

[0001] This utility model relates to the field of filters, and more particularly to a surface acoustic wave (SAW) filter with near-end out-of-band suppression. Background Technology

[0002] Surface acoustic waves (SAWs) are elastic waves that propagate along the surface of an object. SAW devices are characterized by low cost, small size, and multiple functions, and have been widely used in radar, communication, navigation, and identification fields. When SAW filters are used as key components of RF front-end chips, they are mainly used for signal frequency band selection and noise suppression, and thus belong to the category of RF filters. With the increasing demand for high-frequency and high-performance filters in 5G, there is a huge application demand for SAW filters with low insertion loss, high rectangularity, high out-of-band rejection, and small size.

[0003] Existing SAW filters are limited by the electromechanical coupling coefficient of the substrate material, and the reduction in device size inevitably comes with a sacrifice in performance. Therefore, maintaining high performance while reducing device size has become an urgent problem to be solved in the industry. Utility Model Content

[0004] The purpose of this invention is to provide a surface acoustic wave filter with an extension bar structure, comprising interdigitated electrodes, a bus bar, an input port, an output port, at least two ground ports, and an extension bar structure. The input port is configured to receive an input signal and transmit the signal to the output port via the bus bar and the interdigitated electrodes. The at least two ground ports are configured to be connected to one of the input port or the output port via the bus bar and the interdigitated electrodes. The extension bar structure is configured to communicate with one of the at least two ground ports and extends outward from the region including the interdigitated electrodes and the bus bar toward the other of the at least two ground ports.

[0005] One aspect of the present invention is to provide a surface acoustic wave filter with an extension bar structure, wherein the region including interdigitated electrodes and a bus bar is configured as a rectangular region, and the at least two grounding ports are configured at the diagonal of the rectangular region, and wherein the extension bar structure extends along the outside of the rectangular region from one grounding port to the other grounding port.

[0006] One aspect of the present invention is to provide a surface acoustic wave filter with an extended strip structure, wherein the extended strip structure is configured as a long strip structure with the same width.

[0007] One aspect of the present invention is to provide a surface acoustic wave filter with an extended strip structure, wherein the extended strip structure is configured to be formed by long strip-shaped structures of different widths.

[0008] One aspect of the present invention is to provide a surface acoustic wave filter with an extension bar structure, wherein the thickness of the extension bar structure is configured to be equal to either the thickness of the interdigitated electrode or the thickness of the busbar.

[0009] One aspect of the purpose of this utility model is to provide a surface acoustic wave filter with an extended strip structure, wherein the surface acoustic wave filter is configured as a trapezoidal filter.

[0010] One aspect of the purpose of this utility model is to provide a surface acoustic wave filter with an extended strip structure, wherein the trapezoidal filter is configured with a 4.5-order trapezoidal topology.

[0011] One aspect of the present invention is to provide a surface acoustic wave filter with an extended strip structure, further comprising an interdigital capacitor configured to be connected in parallel with a near-end series arm resonator in a trapezoidal filter, wherein the near-end series arm resonator is the penultimate or penultimate series arm resonator connected to the output port.

[0012] One aspect of the present invention is to provide a surface acoustic wave filter with an extended strip structure, wherein the aperture direction of the interdigitated capacitor is configured to be perpendicular to the aperture direction of the resonator connected in parallel.

[0013] One aspect of the present invention is to provide a surface acoustic wave filter with an extension strip structure, further comprising a substrate, wherein the substrate is a POI substrate, comprising a piezoelectric layer, a temperature compensation layer and a base layer, wherein the piezoelectric layer is 600 nm thick 42°LT, the temperature compensation layer is 500 nm thick silicon dioxide, and the base layer is 1000 nm thick high-resistivity silicon, and wherein the extension strip structure, interdigitated electrodes and busbars are arranged above the substrate. Attached Figure Description

[0014] The above and other aspects, features and advantages of exemplary embodiments of the present disclosure will become clearer from the following description taken in conjunction with the accompanying drawings, in which:

[0015] Figure 1 This is a comparison diagram showing the effect of parallel capacitors on the admittance response of resonators in SAW filters;

[0016] Figure 2 This is a schematic diagram illustrating an example of the extension bar structure of a SAW filter according to an embodiment of the present invention;

[0017] Figure 3a This is a schematic diagram illustrating an example of a SAW filter with an extended strip structure according to an embodiment of the present invention;

[0018] Figure 3b It shows Figure 3a The equivalent circuit diagram of the SAW filter with an extended bar structure shown is shown.

[0019] Figure 3c This illustrates a SAW filter with an extended strip structure along a line according to an embodiment of the present invention. Figure 3a A cross-sectional view of line A-A' in the diagram;

[0020] Figure 4 This is a schematic diagram showing a performance comparison between a SAW filter with an extension bar structure and a SAW filter without an extension bar structure according to an embodiment of the present invention, under the same conditions.

[0021] Figure 5 This is a schematic diagram showing a performance comparison between a SAW filter with an extension bar structure and a SAW filter without an extension bar structure according to an embodiment of the present invention, under the condition that the standing wave performance is the same.

[0022] Figure 6 This is a schematic diagram showing the structures of three other surface acoustic wave (SAW) filters with different extension bar structures according to embodiments of the present invention;

[0023] Figure 7 This is a schematic diagram illustrating the performance of four surface acoustic wave (SAW) filters with different extension bar structures according to embodiments of the present invention;

[0024] Figure 8 This is a schematic diagram illustrating the structures of three surface acoustic wave (SAW) filters with different extension bar structures according to embodiments of the present invention, as well as the structure of a SAW filter without an extension bar structure; and

[0025] Figure 9 It shows Figure 8 The diagram illustrates the performance of four types of surface acoustic wave (SAW) filters when used as WiFi filters. Detailed Implementation

[0026] Before proceeding with the detailed description below, it may be advantageous to define certain words and phrases used throughout this disclosure. The terms “comprising” and “including” and their derivatives mean, but are not limited to, “including”. The phrase “at least one”, when used with a list of items, means that different combinations of one or more of the listed items may be used, and that only one item in the list may be required. For example, “at least one of A, B, and C” includes any one of the following combinations: A, B, C, A and B, A and C, B and C, A and B and C.

[0027] Definitions of other specific words and phrases are provided throughout this disclosure. Those skilled in the art will understand that, in many, if not most, cases, such definitions apply to the prior and future use of the words and phrases thus defined.

[0028] The various embodiments of the principles of this disclosure described below in conjunction with the accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this disclosure in any way. Those skilled in the art will understand that the principles of this disclosure can be implemented in any suitably arranged system or device. In some cases, the actions described in this disclosure may be performed in a different order and still achieve the desired result. Furthermore, the processes depicted in the drawings do not necessarily require a specific order or sequential sequence to achieve the desired result. In certain embodiments, multitasking and parallel processing may be advantageous.

[0029] The text and accompanying drawings are provided by way of example only to aid in understanding this disclosure. They should not be construed as limiting the scope of the claims appended to this disclosure in any way. Throughout the drawings, the same reference numerals generally indicate the same elements. Although certain embodiments and examples have been provided, it will be apparent to those skilled in the art, based on the content of this disclosure, that changes may be made to the illustrated embodiments and examples without departing from the scope of this disclosure.

[0030] The rectangular coefficient is an important parameter for SAW filters. Filters with a better rectangular coefficient can achieve steeper cutoff characteristics.

[0031] To overcome the limitations imposed by the electromechanical coupling coefficient of the substrate material on filter performance, researchers in this field have made a series of improvements to enhance filter rectangularity by using parallel capacitors. For example, 1) By arranging filters with expanded bandwidth and high rectangularity on both sides of the passband, the deficiency of low substrate electromechanical coupling coefficient can be compensated to some extent. However, this design will lead to a doubling of the filter size. On the one hand, it is difficult to meet the needs of miniaturization of communication equipment. On the other hand, the increased cost due to the increased size will violate the original intention of choosing this design scheme, that is, to use inexpensive ordinary LT to prepare a filter with large bandwidth and high rectangularity; 2) In addition, the rectangularity of the filter can be improved by connecting a capacitor with an interdigitated bar capacitor structure in parallel with a parallel resonator. However, this structure significantly amplifies the bar period. On the other hand, although the peak structure weakens the excitation of spurious signals, the capacitance value that this structure can provide is limited considering the development needs of device miniaturization; 3) There is also a technical solution to improve the rectangularity by setting a pad layer (thickness not less than 2um) at the bottom of the compensation capacitor to form a horizontal plane different from the interdigitated bar of the excitation main signal transducer. This technical solution can effectively suppress the spurious signal generated by conventional compensation capacitor excitation, avoid affecting the performance index of the surface acoustic wave filter due to the increase of compensation capacitor, and reduce the design requirements of compensation capacitor. However, the introduction of the raised platform has increased the process flow, making production more complicated and significantly increasing costs.

[0032] Figure 1 This is a comparison diagram showing the effect of parallel capacitors on the admittance response of the resonator in a SAW filter. Figure 1 Figure (a) shows the admittance curve, which reflects the effect of capacitance on the electromechanical coupling coefficient of the resonator. Figure (b) shows the real part of the admittance curve, which can be used to observe whether the capacitance introduces spurious modes into the resonator's transmission characteristics (where the blue curve represents the performance of the resonator without parallel capacitors; and the red curve represents the performance of the resonator with parallel capacitors).

[0033] refer to Figure 1 By adding a parallel capacitor, the anti-resonance frequency of the resonator is brought closer to the resonant frequency, which raises the stopband on both sides of the resonator, thus improving the rectangularity of the filter. However, the interdigitated capacitor structure requires careful design of the finger period to avoid spurious signals from its excitation affecting the filter's performance.

[0034] Against the backdrop of the miniaturization demand for surface acoustic wave (SAW) filters, introducing parallel capacitors to improve filter rectangularity still leads to performance degradation issues such as near-end out-of-band rejection and return loss. When miniaturization requirements are met without increasing the number of resonator stages, this characteristic significantly limits the improvement of near-end out-of-band rejection and standing wave ratio (SWR) performance, hindering the realization of low insertion loss, high out-of-band rejection, and small-size filters.

[0035] To resolve the contradiction between device miniaturization and high performance (low insertion loss and VSWR, high out-of-band rejection, high rectangularity, etc.), this utility model discloses an extension strip structure connected to the ground terminal. By adjusting the size and position of the extension line, the near-end out-of-band electromagnetic response of the filter can be controlled, providing an efficient and flexible optimization method for enhancing near-end out-of-band rejection.

[0036] Figure 2 This is a schematic diagram illustrating an example of the extension strip structure of a SAW filter according to an embodiment of the present invention.

[0037] refer to Figure 2 The dashed box area represents the interdigitated electrode and busbar area, the solid circular area represents the port PAD, and the elongated area represents the extension structure. The interdigitated electrode and busbar area is configured as a rectangular region, with two grounding ports located diagonally across this rectangular region. The extension structure is configured such that one end is connected to one grounding port (first grounding port), and extends from that grounding port towards the other grounding port (second grounding port) outside the interdigitated electrode and busbar area. The other end of the extension structure, which is not connected to the first grounding port, can be configured to connect to other grounding ports or remain open.

[0038] According to an embodiment of the present invention, the extension strip structure is configured to connect from one ground port (first ground port) to another ground port (second ground port) along the edge of a rectangular region outside the interdigitated electrode and busbar regions. According to an embodiment of the present invention, the extension strip structure is configured as a long strip-shaped structure with the same width. According to an embodiment of the present invention, the extension strip structure can also be configured to be constructed using long strip-shaped structures of different widths. For example, see reference... Figure 2 In part (a), the extension strip structure is formed by a long strip structure of the same width, and it connects the first grounding port and the second grounding port; see reference. Figure 2 In part (b), the extension strip structure is formed by a long strip structure of the same width, and it connects to the first grounding port but not to the second grounding port; see reference. Figure 2In part (c), the extension strip structure is formed by elongated strip structures of varying widths, and it connects to the first ground port but not to the second ground port. Since the out-of-band response of surface acoustic wave (SAW) filters, especially trapezoidal SAW filters, is highly sensitive to ground inductance, an inductor needs to be connected in series on the ground trace of the package substrate to improve the out-of-band performance of the SAW filter. According to an embodiment of this invention, by adding an extension strip to the ground port, the additional electromagnetic effect of the extension strip structure enables on-chip direct control of out-of-band performance without requiring additional substrate design for the chip, thus reducing design difficulty and R&D costs. According to an embodiment of this invention, the width of the extension strip structure and whether it is connected to the second ground port can be determined based on the center frequency, topology, and substrate material type of the SAW filter.

[0039] According to an embodiment of the present invention, the thickness of the extension strip structure can be configured to be equal to the thickness of the interdigitated electrode; alternatively, the thickness of the extension strip structure can also be configured to be equal to the thickness of the busbar. According to an embodiment of the present invention, the material of the extension strip structure can be configured to be consistent with the material of the interdigitated electrode; alternatively, the extension strip structure can also be configured to be formed by selecting other metal materials.

[0040] Those skilled in the art should understand that Figure 2 The embodiments shown are for illustrative purposes only. Other shapes and grounding positions of the extension strip structure are within the scope of this patent without departing from the scope of this utility model.

[0041] For example, according to an embodiment of the present invention, the interdigitated electrode and busbar region can also be configured in other shapes, such as a circular shape, and two grounding ports are arranged on the diameter of the circular shape, and the extension bar structure is configured to extend from one grounding port (first grounding port) to another grounding port (second grounding port) outside the interdigitated electrode and busbar region.

[0042] Figure 3a This is a schematic diagram illustrating an example of a SAW filter with an extension bar structure according to an embodiment of the present invention.

[0043] Figure 3a A Band 40 SAW filter is shown, configured as a trapezoidal filter. The SAW filter includes a piezoelectric substrate, an extension bar structure, a resonator (IDT interdigital transducer), a busbar connecting the resonator, an input port and an output port, two ground ports, and an interdigital capacitor structure connected in parallel with the series resonator.

[0044] refer to Figure 3aIn an example of a SAW filter with an extension strip structure, a busbar connects multiple interdigital electrodes; the interdigital electrodes are positioned between the busbars; an interdigital capacitor structure is configured in parallel with a near-end series arm resonator; the filter ports are configured as pad ball areas and include an input port, an output port, and a ground port; and the extension strip structure is positioned outside the areas of the interdigital electrodes and busbars and connected to the ground port. The extension strip structure has a width of 5 micrometers, a distance d from the output port of 10 micrometers, and connects to two ground ports via the busbar.

[0045] Figure 3a A SAW filter with a 4.5-order trapezoidal topology is shown. The trapezoidal filter achieves bandpass filter characteristics at a specific frequency by forming an electrically coupled network through an alternating series and parallel arrangement of resonators. According to an embodiment of this invention, in Figure 3a In the SAW filter shown, an interdigital capacitor C is connected in parallel at the fourth series resonator. The aperture direction of the interdigital capacitor C connected in parallel with the fourth series resonator is configured to be perpendicular to the aperture direction of the fourth series resonator. According to an embodiment of the present invention, the interdigital capacitor C is configured to improve the right-side rectangularity of the filter passband. Figure 3b It shows Figure 3a The equivalent circuit diagram of the SAW filter with an extended bar structure is shown below. (Reference) Figure 3b An interdigital capacitor C is connected in parallel at the fourth series arm resonator; however, the interdigital capacitor C can also be configured at other near-end locations. For example, the interdigital capacitor C can be configured to be connected in parallel with a near-end series arm resonator, wherein the near-end series arm resonator is one of the penultimate or penultimate series arm resonators connected to the output port.

[0046] Figure 3c This illustrates a SAW filter with an extended strip structure along a line according to an embodiment of the present invention. Figure 3a A cross-sectional view of line A-A' in the diagram.

[0047] refer to Figure 3c The SAW filter with an extension strip structure also includes a substrate, wherein the substrate is a POI substrate, comprising a piezoelectric layer, a temperature compensation layer, and a base layer. The piezoelectric layer is 600 nm thick with a 42°LT thickness, the temperature compensation layer is 500 nm thick with silicon dioxide, and the base layer is 1000 nm thick with high-resistivity silicon. The extension strip structure, interdigitated electrodes, and busbars are arranged above the substrate, wherein the extension strip structure is made of the same material as the interdigitated electrodes, and its thickness is equal to the busbar thickness. (Reference) Figure 3cThe extension strip structure, interdigitated electrodes, and busbars are formed through a first metal layer (M1). A thickening layer is disposed above the busbars and pad ball placement areas of the interdigitated electrodes. This thickening layer is formed by depositing a metal layer with a thickness of approximately 2 micrometers, which is a second metal layer (M2). The thickening layer reduces busbar resistance to lower insertion loss and enhances ball placement reliability.

[0048] Figure 4 This is a schematic diagram showing a performance comparison between a SAW filter with an extension bar structure and a SAW filter without an extension bar structure according to an embodiment of the present invention, all other things being equal.

[0049] exist Figure 4 In the figure, Figure (a) shows the overall response curve of the B40 surface acoustic wave (SAW) filter; Figure (b) shows the passband response curve of the SAW filter; Figure (c) shows the input port VSWR of the SAW filter; and Figure (d) shows the output port VSWR of the SAW filter. The black curve represents the performance of the filter with the extension bar structure, and the red curve represents the performance of the filter without the extension bar structure.

[0050] refer to Figure 4 Figure (a) shows that the SAW filter with an extended strip structure according to this invention exhibits strong notch filtering on both sides of the passband in both the Band 1 and WIFI bands, significantly improving the suppression in both bands. The absolute suppression in the Band 1 band reaches 49dB, and the absolute suppression in the 2431MHz–2483MHz range of the WIFI band reaches 58dB, while the filter's passband response is almost unaffected. The Band 1 band is configured as the 2110MHz–2170MHz band, and the WIFI band is configured as the 2401MHz–2483MHz band. Reference Figure 4 In charts (b), (c), and (d), the black and red curves match, indicating that the introduction of the extension bar did not affect the passband performance, and the passband insertion loss was ≥1.6dB, with a VSWR less than 1.5. In summary, the SAW filter with the extension bar structure according to this invention provides an efficient and flexible optimization method for enhancing near-end out-of-band suppression when the filter's acoustic response meets design specifications.

[0051] The SAW filter with an extension bar structure according to the present invention has excellent left near-band out-of-band suppression and right WIFI suppression, as well as low passband insertion loss and good standing wave performance.

[0052] Figure 5This is a schematic diagram showing a performance comparison between a SAW filter with an extension bar structure and a SAW filter without an extension bar structure according to an embodiment of the present invention, assuming consistent standing wave performance.

[0053] exist Figure 5 In the figure, (a) represents the overall response curve of the B40 type surface acoustic wave (SAW) filter; (b) represents the passband response curve of the SAW filter; (c) represents the input port VSWR of the SAW filter; and (d) represents the output port VSWR of the SAW filter. The black curve represents the performance of the filter with the extended bar structure, and the red curve represents the performance of the filter without the extended bar structure while ensuring consistent VSWR performance.

[0054] refer to Figure 5 In Figure (a), the overall response curves of both the SAW filter with and without the extension bar structure exhibit strong notch filtering in the band 1 band, with out-of-band rejection reaching 49 dB. However, in the WIFI band, it is clearly observed that the notch filtering of the red response curve of the SAW filter without the extension bar structure is significantly higher than that of the black overall response curve. This indicates that, while maintaining consistent VSWR performance, the out-of-band rejection of the SAW filter without the extension bar structure in the left band 1 band achieves optimization by shifting the resonant point of the parallel resonator to the left. However, this also shifts the anti-resonant point of the parallel resonator to the left. To ensure consistent VSWR performance, the resonant point (anti-resonant point) of the series resonator must be shifted to the left. The result is that the insertion loss on the right side of the passband increases compared to the SAW filter with the extension bar structure, and its WIFI rejection is significantly reduced.

[0055] Figure 6 This is a schematic diagram showing the structures of three other surface acoustic wave (SAW) filters with different extension bar structures according to embodiments of the present invention.

[0056] like Figure 6 As shown, in (a), the extension strip structure extends from the first grounding port to the second grounding port and is not connected to the second grounding port; in (b), the extension strip structure extends from the second grounding port to the first grounding port and is not connected to the first grounding port. The width of the extension strip in both (a) and (b) is 5 micrometers. In (c), the extension strip structure connects the first grounding port and the second grounding port, and in the extension strip structure in (c), the width of the fine region is 5 micrometers and the width of the wide region is 24 micrometers.

[0057] Figure 7This diagram illustrates the performance of four surface acoustic wave (SAW) filters with different extension bar structures according to embodiments of the present invention, where black represents the test results of the SAW filter in Figure 3(a), and blue represents... Figure 6 (a) Test results of the surface acoustic wave (SAW) filter in Figure (a), purple indicates... Figure 6 (b) Test results of the surface acoustic wave (SAW) filter, and red indicates Figure 6 (c) Test results of surface acoustic wave (SAW) filter.

[0058] refer to Figure 7 Figure (a) shows the overall response curve of the B40 type surface acoustic wave (SAW) filter. According to Figure (a), the connection method and width of the extension strip structure affect the out-of-band performance of the trapezoidal SAW filter. The suppression performance is best when the extension strip structure is connected to both the first and second grounding ports. Furthermore, in Figure 7 In the figure, (b) shows the passband response curve of the surface acoustic wave (SAW) filter; (c) shows the input port VSWR of the SAW filter; and (d) shows the output port VSWR of the SAW filter. Referring to figures (b), (c) and (d), it can be seen that different extension strip structures have no effect on the passband performance of the filter.

[0059] By Figure 7 Figures (e) and (f) further illustrate the suppression performance of the four extension strip structures for the high-suppression-requirement bands (2110MHz–2200MHz) in the left near-band Band 1 and the right near-band WiFi (2421MHz–2483MHz). Figures (e) and (f) show that when the extension strip structure is connected only to the first ground port or only to the second ground port, the suppression curves for both the Band 1 and WiFi bands of the filter significantly increase, resulting in a worse suppression effect. Furthermore, when the extension strip structure is connected to both ground ports, and a portion of the extension strip structure is thickened, the filter forms a strong notch in the Band 1 band, achieving an absolute suppression of 46.4dB, similar to the suppression performance of the unthickened extension strip structure. However, no strong notch appears in the WiFi band, indicating that the inductance value of the thickened extension strip structure is too small to form a strong notch in the WiFi band. Those skilled in the art can configure the out-of-band suppression performance near the passband of the trapezoidal filter by adjusting the width and connection method of the extension strip structure. According to an embodiment of the present invention, for a B40 trapezoidal surface acoustic wave (SAW) filter, the width of the extension strip structure is configured to be 5 micrometers, the distance d between it and the output port is 10 micrometers, and the two grounding ports are connected by a busbar.

[0060] Figure 8This is a schematic diagram showing the structures of three surface acoustic wave (SAW) filters with different extension bar structures according to embodiments of the present invention, as well as the structure of a surface acoustic wave (SAW) filter without an extension bar structure.

[0061] like Figure 8 As shown, in filter (a), the extension strip structure extends from the first ground port to the second ground port and is connected to the second ground port; in filter (b), the extension strip structure extends from the first ground port to the second ground port but is not connected to the second ground port; in (c), the extension strip structure extends from the second ground port to the first ground port but is not connected to the first ground port; and in filter (d), there is no extension strip structure. Figure 8 In this case, the width of the extension strip joint is configured to be 16 micrometers.

[0062] Figure 9 It shows Figure 8 The diagram illustrates the performance of four surface acoustic wave (SAW) filter structures as WiFi filters (center frequency 2442MHz). The black curve represents the... Figure 8 The test results of the surface acoustic wave (SAW) filter with structure (a) are shown in blue. Figure 8 (b) Test results of the surface acoustic wave (SAW) filter, the purple curve represents... Figure 8 (c) Test results of the surface acoustic wave (SAW) filter, and the red curve as... Figure 8 Test results of (d) surface acoustic wave (SAW) filter.

[0063] refer to Figure 9 In the figure, Figure (a) shows the overall response curves of the four surface acoustic wave (SAW) filters, Figure (b) shows the suppression performance of the four filter structures for the high suppression requirement band 2350MHz to 2370MHz of the left near-end Band40 frequency band of the passband, and Figure (c) shows the suppression performance of the four filter structures for the high suppression requirement band 2500MHz to 2690MHz of the right near-end WiFi frequency band Band41.

[0064] Depend on Figure 9As shown in Figures (a), (b), and (c), when the extension bar structure is connected to both ground ports simultaneously, the filter's suppression curve rises significantly in the Band 40 band, with a suppression of only 40dB, indicating poor suppression performance. When the extension bar structure is connected only to the first ground port, the filter exhibits optimal suppression performance in both the Band 40 and Band 41 bands. When the extension bar structure is connected only to the second ground port, the filter's suppression curve rises significantly in both the Band 40 and Band 41 high suppression requirement bands, and its suppression performance deteriorates compared to when only the first ground port is connected. When the extension bar structure is not introduced, the filter's suppression performance in the Band 40 high suppression requirement band is comparable to that of the filter connected only to the second ground port, but in the Band 41 high suppression requirement band, its suppression curve rises the most, indicating the worst suppression performance.

[0065] according to Figure 9 It is known that the extension strip structure can significantly adjust the near-band out-of-band performance of the acoustic trapezoidal surface wave (SAW) filter. Those skilled in the art can design the optimal width and connection method of the extension strip according to the different center frequencies and topologies of the filter to obtain good out-of-band performance.

[0066] Those skilled in the art will understand that the various illustrative logic blocks, modules, circuits, and steps described in this disclosure can be implemented in hardware, software, or a combination of both. Whether such a set of functions is implemented in hardware or software depends on the specific application and the design constraints imposed on the overall system. Those skilled in the art may implement the described set of functions in different ways for each specific application, but such design decisions should not be construed as departing from the scope of this disclosure.

[0067] The above embodiments of this disclosure are merely for ease of description and to aid in a comprehensive understanding of this disclosure, and are not intended to limit the scope of this disclosure. Therefore, it should be understood that all modifications and alterations, or forms of modifications and alterations, derived from the technical concept of this disclosure, other than those disclosed herein, fall within the scope of this disclosure.

Claims

1. A surface acoustic wave filter with an extension bar structure, comprising interdigitated electrodes, a bus bar, an input port, an output port, at least two ground ports, and an extension bar structure, characterized in that, The input port is configured to receive input signals and transmit the signals to the output port via a busbar and interdigitated electrodes; The at least two grounding ports are configured to be connected to one of the input ports or the output ports via the busbar and interdigitated electrodes; as well as The extension strip structure is configured to communicate with one of the at least two grounding ports and extend outside the region including the interdigitated electrodes and the busbar toward the other of the at least two grounding ports.

2. The surface acoustic wave filter according to claim 1, characterized by, The region including the interdigitated electrodes and the busbar is configured as a rectangular region, and the at least two grounding ports are located at the diagonals of the rectangular region. The extension strip structure extends along the outside of the rectangular region from one grounding port to another grounding port.

3. The surface acoustic wave filter according to claim 1, characterized by, The extension strip structure is configured as a long strip structure with the same width.

4. The surface acoustic wave filter according to claim 1, characterized by, The extension strip structure is configured to be constructed by long strip-shaped structures of different widths.

5. The surface acoustic wave filter according to claim 1, wherein The thickness of the extension strip structure is configured to be equal to either the thickness of the interdigitated electrode or the thickness of the busbar.

6. The surface acoustic wave filter according to claim 1, wherein The surface acoustic wave filter is configured as a trapezoidal filter.

7. The surface acoustic wave filter according to claim 6, characterized by The trapezoidal filter is configured with a 4.5-order trapezoidal topology.

8. The surface acoustic wave filter according to claim 6, wherein It also includes interdigitated capacitors configured to be connected in parallel with a near-end series arm resonator in series in the trapezoidal filter, the near-end series arm resonator being the penultimate or penultimate series arm resonator connected to the output port.

9. The surface acoustic wave filter according to claim 8, characterized by, The aperture direction of the interdigital capacitor is configured to be perpendicular to the aperture direction of the resonator connected in parallel.

10. The surface acoustic wave filter according to claim 1, wherein It also includes a substrate, which is a POI substrate, comprising a piezoelectric layer, a temperature compensation layer, and a base layer. The piezoelectric layer is 600 nm thick and has a 42°LT thickness; the temperature compensation layer is 500 nm thick and has silicon dioxide thickness; and the substrate layer is 1000 nm thick and has high resistivity silicon thickness. The extension bar structure, interdigitated electrodes, and busbars are arranged above the substrate.

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