Bandstop filter and electronic module

Abstract

The application relates to a band elimination filter and an electronic module. The band elimination filter comprises a plurality of series arms connected in series, a first parallel circuit and a second parallel circuit. The first parallel circuit or the second parallel circuit is arranged in parallel between any two adjacent series arms. The frequency difference between the resonance frequency of a first resonator in the first parallel circuit and the resonance frequency of a second resonator in the second parallel circuit is greater than or equal to 10 MHz and less than or equal to 50 MHz. By arranging resonators with close resonance frequencies in parallel, narrow-band attenuation is generated, thereby solving the problem of poor steepness.

Description

Technical Field

[0001] This application relates to the field of signal filtering technology, and in particular to a band-stop filter and electronic module. Background Technology

[0002] With the development of technology and the continuous progress of society, the requirements for signal accuracy of electronic devices are becoming increasingly stringent. Many electronic devices now employ filters to filter signals. Traditional filters mainly use capacitors in the in-line (series) arms for filtering, which suffers from a deterioration in steepness. Summary of the Invention

[0003] Therefore, it is necessary to provide a band-stop filter and electronic module that can solve the problem of steepness variation, in order to address the above issues.

[0004] The first aspect of this application provides a band-stop filter, including a series arm, a first parallel circuit, and a second parallel circuit. The number of series arms is multiple and they are connected in series sequentially. The first parallel circuit or the second parallel circuit is connected in parallel between two adjacent series arms. The frequency difference between the resonant frequency of the first resonator in the first parallel circuit and the resonant frequency of the second resonator in the second parallel circuit is greater than or equal to 10MHz and less than or equal to 50MHz.

[0005] In one embodiment, the frequency difference between the resonant frequency of the first resonator and the resonant frequency of the second resonator is greater than or equal to 25MHz and less than or equal to 45MHz.

[0006] In one embodiment, the resonant frequency of the first resonator is less than the resonant frequency of the second resonator; the duty cycle of the first resonator is different from the duty cycle of the second resonator, so that the electromechanical coupling coefficient of the first resonator is less than the electromechanical coupling coefficient of the second resonator.

[0007] In one embodiment, the series arm includes a first series arm, a second series arm, and a third series arm connected in series sequentially. A first parallel circuit is connected in parallel between the first series arm and the second series arm, and a second parallel circuit is connected in parallel between the second series arm and the third series arm. The first series arm, the second series arm, and the third series arm are all capacitors, and the capacitance values ​​of the first series arm and the third series arm are greater than the capacitance value of the second series arm.

[0008] In one embodiment, the equivalent capacitance of the first resonator and the second resonator is less than the capacitance value of the second series arm.

[0009] In one embodiment, the first parallel circuit includes a first inductor and a first resonator connected in parallel, and the second parallel circuit includes a second inductor and a second resonator connected in parallel; wherein the inductance value of the first inductor is greater than the inductance value of the second inductor.

[0010] In one embodiment, the first resonator includes a first resonator A and a first resonator B connected in parallel, wherein the resonant frequency of the first resonator B is greater than the resonant frequency of the first resonator A, and the capacitance of the first resonator B is less than the capacitance of the first resonator A.

[0011] In one embodiment, the Q value of the first resonator B is less than the Q value of the first resonator A.

[0012] In one embodiment, the second resonator includes a second resonator A and a second resonator B connected in parallel, wherein the resonant frequency of the second resonator B is less than the resonant frequency of the second resonator A, and the capacitance of the second resonator B is less than the capacitance of the second resonator A.

[0013] In one embodiment, the Q value of the second resonator B is less than the Q value of the second resonator A.

[0014] A second aspect of this application provides an electronic module including the aforementioned band-stop filter.

[0015] The aforementioned band-stop filter and electronic module connect multiple series arms sequentially, with a first parallel circuit or a second parallel circuit connected in parallel between adjacent series arms. The frequency difference between the resonant frequency of the first resonator in the first parallel circuit and the resonant frequency of the second resonator in the second parallel circuit is greater than or equal to 10MHz and less than or equal to 50MHz. By connecting resonators with frequencies close to their resonant frequencies in parallel, narrowband attenuation is generated, thereby solving the problem of deteriorating steepness. Attached Figure Description

[0016] Figure 1 Here is a block diagram of a band-stop filter in one embodiment;

[0017] Figure 2 This is a schematic diagram of the structure of a band-stop filter in one embodiment;

[0018] Figure 3 This is a schematic diagram of the narrowband notch characteristics of a band-stop filter in one embodiment;

[0019] Figure 4 This is a schematic diagram of the narrowband notch characteristics of a band-stop filter in another embodiment;

[0020] Figure 5 This is a schematic diagram of the structure of a band-stop filter in another embodiment;

[0021] Figure 6 This is a schematic diagram of the narrowband notch characteristics of a band-stop filter in another embodiment;

[0022] Figure 7 This is a schematic diagram of the narrowband notch characteristics of a band-stop filter in yet another embodiment. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0025] It is understood that the terms "first," "second," etc., used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of this application, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0026] It is understood that the term "connection" in the following embodiments should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have electrical signal or data transmission with each other.

[0027] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising,” “including,” or “having,” etc., specify the presence of the stated feature, whole, operation, component, part, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, operations, components, parts, or combinations thereof.

[0028] In one embodiment, such as Figure 1As shown, a band-stop filter is provided, including series arms 100, a first parallel circuit 200, and a second parallel circuit 300. Multiple series arms 100 are connected in series, and the first parallel circuit 200 or the second parallel circuit 300 is connected in parallel between adjacent series arms 100. The frequency difference between the resonant frequency (Fr) of the first resonator in the first parallel circuit 200 and the resonant frequency of the second resonator in the second parallel circuit 300 is greater than or equal to 10MHz and less than or equal to 50MHz. The number of series arms 100 can be three or more. When there are three series arms 100, the first parallel circuit 200 and the second parallel circuit 300 can be connected in parallel between every two adjacent series arms 100, respectively. When there are more than one series arm 100, the first parallel circuit 200 or the second parallel circuit 300 can be connected in parallel between some or all of every two adjacent series arms 100. Figure 2 As shown, the relationship between the resonant frequencies of the first resonator reso1 and the second resonator reso2 is not unique. The resonant frequency of the first resonator reso1 can be lower than that of the second resonator reso2, or vice versa. Furthermore, the frequency difference between the resonant frequencies of the first resonator reso1 and the second resonator reso2 is also not unique; for example, it could be 10MHz, 30MHz, 50MHz, etc., and can be set according to actual needs. Further, the frequency difference between the resonant frequencies of the first resonator reso1 and the second resonator reso2 can also be greater than or equal to 25MHz and less than or equal to 45MHz, for example, it can be set to 25MHz, 35MHz, 45MHz, etc.

[0029] The aforementioned band-stop filter connects multiple series arms 100 in series, with either a first parallel circuit 200 or a second parallel circuit 300 connected in parallel between adjacent series arms 100. The frequency difference between the resonant frequency of the first resonator in the first parallel circuit 200 and the resonant frequency of the second resonator in the second parallel circuit 300 is greater than or equal to 10MHz and less than or equal to 50MHz. By connecting resonators with frequencies close to their resonant frequencies in parallel, narrowband attenuation is generated, thereby solving the problem of deteriorating steepness.

[0030] For ease of understanding, the following explanation will use the example that the resonant frequency of the first resonator reso1 is less than the resonant frequency of the second resonator reso2, and will use the first resonator reso1 as the resonator on the low-frequency side and the second resonator reso2 as the resonator on the high-frequency side.

[0031] In one embodiment, such as Figure 2 and Figure 3As shown, the series arm 100 includes a first series arm 110, a second series arm 120, and a third series arm 130 connected in series. A first parallel circuit 200 is connected in parallel between the first series arm 110 and the second series arm 120, and a second parallel circuit 300 is connected in parallel between the second series arm 120 and the third series arm 130. The first series arm 110, the second series arm 120, and the third series arm 130 are all capacitors, namely capacitor C1, capacitor C2, and capacitor C3, respectively. The capacitance values ​​of the first series arm 110 and the third series arm 130 are greater than the capacitance value of the second series arm 120.

[0032] Further, the first parallel circuit 200 includes a first inductor L1 and a first resonator reso1 connected in parallel, and the second parallel circuit 300 includes a second inductor L2 and a second resonator reso2 connected in parallel; the inductance value of the first inductor L1 is greater than the inductance value of the second inductor L2. In this embodiment, the inductance value of the first inductor L1 is 2.8nH, and the inductance value of the second inductor L2 is 2.6nH. The resonant frequency of the first resonator reso1 can be set to 2436MHz, and the resonant frequency of the second resonator reso2 can be set to 2476MHz.

[0033] In this embodiment, the capacitance values ​​of the first series arm 110 and the third series arm 130 can be the same or different. For example, the capacitance value of the first series arm 110 can be greater than, equal to, or less than the capacitance value of the third series arm 130, as long as the capacitance values ​​of both the first series arm 110 and the third series arm 130 are greater than the capacitance value of the second series arm 120. In this embodiment, the capacitance values ​​of both the first series arm 110 and the third series arm 130 are 1.6 pF, and the capacitance value of the second series arm 120 is 0.8 pF. Furthermore, the equivalent capacitance of the first resonator reso1 and the second resonator reso2 is less than the capacitance value of the second series arm 120. Similarly, the equivalent capacitance of the first resonator reso1 and the second resonator reso2 can be the same or different. In this embodiment, the equivalent capacitance of both the first resonator reso1 and the second resonator reso2 is 0.5 pF.

[0034] The band-stop filter is configured with resonators, inductors, and capacitors according to the above parameters. Narrowband notch characteristics are as follows: Figure 3As shown in the diagram, the resonant frequency of the first resonator, reso1, is set to 2436MHz, and the resonant frequency of the second resonator, reso2, is set to 2476MHz. The equivalent capacitance of both the first resonator, reso1, and the second resonator, reso2, is 0.5pF. By using two parallel resonators with similar resonant frequencies, a narrow-band attenuation is formed, thereby improving the steepness problem. By properly setting the parameter relationship between capacitor (C), inductor (L), and resonant frequency (Fr), miniaturization of notch filtering functions suitable for Wi-Fi isolation can be achieved.

[0035] In one embodiment, the resonant frequency of the first resonator reso1 is lower than the resonant frequency of the second resonator reso2; the duty cycle of the first resonator reso1 is different from the duty cycle of the second resonator reso2, so that the electromechanical coupling coefficient (k) of the first resonator reso1 is lower than that of the second resonator reso2. 2 The electromechanical coupling coefficient of the first resonator (reso1) is less than that of the second resonator (reso2). The first resonator (reso1) and the second resonator (reso2) can be formed on a piezoelectric substrate, and the electromechanical coupling coefficient of the resonators can be changed by configuring the duty cycle. Preferably, the electromechanical coupling coefficient of the resonators is between 45% and 65% at the duty cycle. When the duty cycle is higher than 65% or lower than 45%, the electromechanical coupling coefficient decreases. With the same pitch, changing the duty cycle of the resonators also changes the frequency. When the duty cycle for the same pitch is set smaller, the frequency increases, and the electromechanical coupling coefficient decreases. The electromechanical coupling coefficients of the first resonator (reso1) and the second resonator (reso2) are not unique. In this embodiment, the electromechanical coupling coefficient of the first resonator (reso1) is configured as 6%, and the electromechanical coupling coefficient of the second resonator (reso2) is configured as 8%.

[0036] like Figure 4 As shown, the black line labeled ① represents the narrowband notch characteristic curve when the electromechanical coupling coefficients of both the first resonator reso1 and the second resonator reso2 are configured to 8%; the blue line labeled ② represents the narrowband notch characteristic curve when the electromechanical coupling coefficients of both the first resonator reso1 and the second resonator reso2 are configured to 6%; and the red line labeled ③ represents the narrowband notch characteristic curve when the electromechanical coupling coefficient of the first resonator reso1 is configured to 6% and the electromechanical coupling coefficient of the second resonator reso2 is configured to 8%. If the duty cycle of both the first resonator reso1 and the second resonator reso2 is adjusted simultaneously to reduce the electromechanical coupling coefficient, the insertion loss (IL) on the low-frequency side of the notch region can be improved, but this will lead to a deterioration in the attenuation at the notch center (black line → blue line). Therefore, reducing the electromechanical coupling coefficient of only the first resonator reso1 on the low-frequency side can mitigate the deterioration in the attenuation at the notch center (red line).

[0037] In one embodiment, such as Figure 5 As shown, the first resonator reso1 includes a first resonator A (reso1A) and a first resonator B (reso1B) connected in parallel. The resonant frequency of the first resonator B (reso1B) is greater than the resonant frequency of the first resonator A (reso1A), and the capacitance of the first resonator B (reso1B) is less than the capacitance of the first resonator A (reso1A). The resonant frequencies of both the first resonator B (reso1B) and the first resonator A (reso1A) are less than the resonant frequency of the second resonator reso2. In this embodiment, the resonant frequency of the first resonator A (reso1A) is set to 2436MHz, so the resonant frequency of the first resonator B (reso1B) can be set to 2436 + 7.5MHz. The capacitance values ​​and ratios of the first resonator A (reso1A) and the first resonator B (reso1B) are not unique. In terms of the segmentation ratio, the capacitance of the resonator forming the outer attenuation electrode is larger. Taking a 7:3 ratio as an example, the capacitance of the first resonator A (reso1A) can be 0.35pF and the capacitance of the first resonator B (reso1B) can be 0.15pF.

[0038] Correspondingly, the second resonator reso2 may include a second resonator A (reso2A) and a second resonator B (reso2B) connected in parallel. The resonant frequency of the second resonator B (reso2B) is lower than the resonant frequency of the second resonator A (reso2A), and the capacitance of the second resonator B (reso2B) is lower than the capacitance of the second resonator A (reso2A). The resonant frequencies of both the second resonator A (reso2A) and the second resonator B (reso2B) are higher than the resonant frequencies of the first resonator A (reso1A) and the first resonator B (reso1B). In this embodiment, the resonant frequency of the second resonator A (reso2A) is set to 2476MHz, then the resonant frequency of the second resonator B (reso2B) can be set to 2476-6.5MHz. The capacitance values ​​and ratios of the second resonator A (reso2A) and the second resonator B (reso2B) are not unique. Taking a 7:3 ratio as an example, the capacitance of the second resonator A (reso2A) is 0.35pF and the capacitance of the second resonator B (reso2B) is 0.15pF.

[0039] The band-stop filter is further configured with a resonator according to the above structure and parameters, and the narrowband notch characteristics are as follows: Figure 6As shown in the diagram. The electromechanical coupling coefficient of the first resonator, reso1, is configured to be 6%, and that of the second resonator, reso2, is configured to be 8%. The resonant frequency of the first resonator A (reso1A) is set to 2436MHz, and the resonant frequency of the first resonator B (reso1B) is set to 2436 + 7.5MHz. The capacitance of the first resonator A (reso1A) is 0.35pF, and that of the first resonator B (reso1B) is 0.15pF. The resonant frequency of the second resonator A (reso2A) is set to 2476MHz, and that of the second resonator B (reso2B) is set to 2476 - 6.5MHz. The capacitance of the second resonator A (reso2A) is 0.35pF, and that of the second resonator B (reso2B) is 0.15pF. By dividing the resonator into two parallel sections with different resonant frequencies Fr, the attenuation of the notch filter can be improved (blue line → red line).

[0040] Furthermore, to prevent steep bounces in the notch section, the Q values ​​(quality factors) of the two parallel resonators after the bisection can be set. In one embodiment, the Q value of the first resonator B (reso1B) is less than the Q value of the first resonator A (reso1A). Further, the Q value of the second resonator B (reso2B) is less than the Q value of the second resonator A (reso2A). The specific Q values ​​of the two parallel resonators after the bisection are not unique. For example, after the bisection, the Q value of the first resonator B (reso1B) can be reduced to 300, and the Q value of the second resonator B (reso2B) can be reduced to 250. The Q values ​​of the first resonator A (reso1A) and the second resonator A (reso2A) can remain unchanged or change slightly, as long as the Q value of the first resonator B (reso1B) is less than the Q value of the first resonator A (reso1A), and the Q value of the second resonator B (reso2B) is less than the Q value of the second resonator A (reso2A). Figure 7 As shown, by reducing the Q value of the resonator (inner attenuation pole) added due to the bisection, a steep bounce in the notch section can be prevented, thereby obtaining a stable response (blue line → red line).

[0041] In one embodiment, an electronic module is also provided, including the band-stop filter described above.

[0042] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0043] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A band-stop filter, characterized in that, It includes a series arm, a first parallel circuit, and a second parallel circuit. The number of series arms is multiple and they are connected in series. The first parallel circuit or the second parallel circuit is connected in parallel between two adjacent series arms. The frequency difference between the resonant frequency of the first resonator in the first parallel circuit and the resonant frequency of the second resonator in the second parallel circuit is greater than or equal to 10MHz and less than or equal to 50MHz.

2. The band-stop filter according to claim 1, characterized in that, The frequency difference between the resonant frequency of the first resonator and the resonant frequency of the second resonator is greater than or equal to 25MHz and less than or equal to 45MHz.

3. The band-stop filter according to claim 1, characterized in that, The resonant frequency of the first resonator is less than that of the second resonator; the duty cycle of the first resonator is different from that of the second resonator, so that the electromechanical coupling coefficient of the first resonator is less than that of the second resonator.

4. The band-stop filter according to claim 1, characterized in that, The series arm includes a first series arm, a second series arm, and a third series arm connected in series. A first parallel circuit is connected in parallel between the first series arm and the second series arm, and a second parallel circuit is connected in parallel between the second series arm and the third series arm. The first series arm, the second series arm, and the third series arm are all capacitors, and the capacitance values ​​of the first series arm and the third series arm are greater than the capacitance value of the second series arm.

5. The band-stop filter according to claim 4, characterized in that, The equivalent capacitance of the first resonator and the second resonator is less than the capacitance of the second series arm.

6. The band-stop filter according to claim 1, characterized in that, The first parallel circuit includes a first inductor and a first resonator connected in parallel, and the second parallel circuit includes a second inductor and a second resonator connected in parallel; wherein the inductance value of the first inductor is greater than the inductance value of the second inductor.

7. The band-stop filter according to any one of claims 1 to 6, characterized in that, The first resonator includes a first resonator A and a first resonator B connected in parallel. The resonant frequency of the first resonator B is greater than the resonant frequency of the first resonator A, and the capacitance of the first resonator B is less than the capacitance of the first resonator A.

8. The band-stop filter according to claim 7, characterized in that, The Q value of the first resonator B is less than the Q value of the first resonator A.

9. The band-stop filter according to any one of claims 1 to 6, characterized in that, The second resonator includes a second resonator A and a second resonator B connected in parallel. The resonant frequency of the second resonator B is less than the resonant frequency of the second resonator A, and the capacitance of the second resonator B is less than the capacitance of the second resonator A.

10. The band-stop filter according to claim 9, characterized in that, The Q value of the second resonator B is less than the Q value of the second resonator A.

11. An electronic module, characterized in that, Includes the band-stop filter as described in any one of claims 1 to 10.

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