Filter circuit and band-pass filter device
By designing a filter circuit including acoustic resonator and filtering unit, the problems of small bandwidth and poor rectangular coefficient of traditional bandpass filters are solved, and efficient signal suppression and performance improvement are achieved.
Patent Information
- Application Number
- CN202421930763.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-10
- Publication Date
- 2025-05-27
- Estimated Expiration
- 2034-08-10
AI Technical Summary
Traditional bandpass filters face the problems of small bandwidth and poor rectangular coefficients when designing, especially when meeting wide band and high selectivity requirements, it is difficult to effectively suppress signals.
A filter circuit is designed, including a first acoustic wave resonator, a high-pass filter unit, a second acoustic wave resonator and a low-pass filter unit. By combining the high-pass filter unit and a low-pass filter unit, and introducing acoustic wave resonator at its ports, it reduces the width of the transition band on the high-frequency side and meets the demand for high rectangular coefficients.
It realizes the width of the transition band on the high frequency side to meet the needs of high rectangular coefficients, thereby effectively suppressing the signal in the N79 band and improving the performance of the filter.
Smart Images
Figure CN222916004U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of filters, and particularly relates to a filtering circuit and a band-pass filtering device. Background Art
[0002] In modern communication systems, the design of band-pass filters is crucial for signal transmission and reception. Especially in 5G networks, the application of frequency band N77 (3.3 - 4.2 GHz) is becoming more and more widespread, and the performance requirements for filters are also getting higher and higher. The design methods of traditional band-pass filters face many challenges, especially when wide frequency bands and high selectivity need to be satisfied, these challenges become more prominent.
[0003] First of all, thin-film bulk acoustic resonators (FBARs) have received extensive attention in filter design due to their high Q value and miniaturization characteristics. FBARs utilize the propagation characteristics of acoustic waves in thin-film materials to achieve high-performance frequency selection. However, a major limitation of FBARs lies in their electromechanical coupling coefficient. The electromechanical coupling coefficient is a parameter that measures the energy conversion efficiency between acoustic waves and electrical signals. Although the high electromechanical coupling coefficient of FBARs helps to improve the selectivity of filters, its bandwidth is limited by material properties and structural design. Specifically, it is usually difficult for the bandwidth of FBARs to cover the 3.3 - 4.2 GHz range of the N77 frequency band. This is because within a relatively wide frequency band, FBARs need to maintain good resonance characteristics at different frequency points, but in practice, the limitations of materials and manufacturing processes make this difficult to achieve. Therefore, directly using FBARs to design band-pass filters for the N77 frequency band often fails to meet the requirements of large bandwidth.
[0004] On the other hand, integrated passive devices (IPDs) are also widely used in filter design. IPDs integrate passive components such as inductors, capacitors, and resistors on a substrate to achieve a compact circuit design. The advantage of this design method is that it can achieve high-precision and high-consistency circuit components through precise microfabrication technology. However, the main problem of IPDs in band-pass filter design lies in their insufficient out-of-band rejection performance. Specifically, the transition band of the out-of-band rejection of filters designed by IPDs is relatively wide, that is, the transition interval from the passband to the stopband is relatively long. This relatively wide transition band results in a poor rectangular coefficient of the filter. The rectangular coefficient is an important indicator for measuring the selectivity of a filter, which reflects the steepness of the transition region between the passband and the stopband of the filter. A poor rectangular coefficient means that the filter cannot effectively distinguish between the desired signal and interference signals, resulting in performance degradation.
[0005] Therefore, it is urgent to develop a new filtering circuit and a band-pass filtering device to solve the technical problems of small bandwidth and poor rectangular coefficient caused by directly using FBARs or IPDs in traditional band-pass filters. Summary of the Utility Model
[0006] The object of the present utility model is to provide a filter circuit and a band-pass filtering device.
[0007] To solve the above technical problems, the present utility model provides a filter circuit, which includes: a first acoustic wave resonator, a high-pass filtering unit, a second acoustic wave resonator, and a low-pass filtering unit; wherein the first acoustic wave resonator, the high-pass filtering unit, the second acoustic wave resonator, and the low-pass filtering unit are connected in sequence, the first acoustic wave resonator is connected to an input port, and the low-pass filtering unit is connected to an output port; the input end of the first acoustic wave resonator is adapted to receive a signal through the input port, and the signal is output through the output port after being processed by the first acoustic wave resonator, the high-pass filtering unit, the second acoustic wave resonator, and the low-pass filtering unit.
[0008] Specifically, the first acoustic wave resonator is a thin film bulk acoustic wave resonator, and the number of resonator elements in the first acoustic wave resonator is N, where N≥1, and the resonator elements in the first acoustic wave resonator are connected in series.
[0009] Specifically, the first acoustic wave resonator is connected to a first inductor in sequence, the first acoustic wave resonator is connected to the input port, and the first inductor is connected to the high-pass filtering unit.
[0010] Specifically, the high-pass filtering unit includes: a first capacitor, a second capacitor, a second inductor, and a third inductor; both ends of the first capacitor are respectively connected to the first acoustic wave resonator and the second acoustic wave resonator; one end of the second capacitor and one end of the second inductor are respectively connected to both ends of the first capacitor, and the other end of the second capacitor is grounded through the third inductor, and the other end of the second inductor is grounded.
[0011] Specifically, the second acoustic wave resonator is a thin film bulk acoustic wave resonator, and the number of resonator elements in the second acoustic wave resonator is N, where N≥1, and the resonator elements in the first acoustic wave resonator are connected in series.
[0012] Specifically, a fourth inductor, the second acoustic wave resonator, and a fifth inductor are connected in sequence, and the fourth inductor is connected to the high-pass filtering unit, and the fifth inductor is connected to the low-pass filtering unit.
[0013] Specifically, the low-pass filtering unit includes: a sixth inductor, a seventh inductor, an eighth inductor, a third capacitor, a fourth capacitor, and a ninth inductor; the sixth inductor, the seventh inductor, and the eighth inductor are connected in sequence, the sixth inductor is connected to the second acoustic resonator, and the eighth inductor is connected to the output port; one end of the third capacitor and one end of the fourth capacitor are respectively connected to both ends of the seventh inductor, and the other end of the third capacitor and the other end of the fourth capacitor are both connected to one end of the ninth inductor, and the other end of the ninth inductor is grounded.
[0014] Specifically, the low-pass filtering unit further includes: a fifth capacitor; the fifth capacitor is connected in parallel with the sixth inductor.
[0015] Specifically, the low-pass filtering unit further includes: a sixth capacitor; the sixth capacitor is connected in parallel with the seventh inductor.
[0016] On the other hand, the present utility model provides a band-pass filtering device, which includes: the filtering circuit as described above, a substrate, and a plastic package; wherein a first installation cavity and a second installation cavity are provided between the plastic package and the substrate; the first acoustic resonator and the second acoustic resonator in the filtering circuit are located in the first installation cavity, and the high-pass filtering unit and the low-pass filtering unit are located in the second installation cavity.
[0017] The beneficial effect of the present utility model is that the present utility model combines the high-pass filtering unit and the low-pass filtering unit, and at the same time introduces the first acoustic resonator and the second acoustic resonator at the ports of the high-pass filtering unit and the low-pass filtering unit, which can reduce the width of the high-frequency side transition band, meet the requirement of a high rectangularity coefficient, and further realize the suppression of signals in the N79 frequency band.
[0018] Other features and advantages of the present utility model will be described in the subsequent description, and part of them will become obvious from the description or be understood by implementing the present utility model.
[0019] To make the above objects, features, and advantages of the present utility model more obvious and understandable, the following specific preferred embodiments are given, and in conjunction with the accompanying drawings, the detailed description is as follows. Description of the Drawings
[0020] In order to more clearly illustrate the specific embodiments of the present utility model or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present utility model. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.
[0021] Figure 1 It is a schematic diagram of the filtering circuit provided by the embodiment of the present utility model;
[0022] Figure 2 is the circuit diagram of the filter circuit provided by the embodiment of the present utility model;
[0023] Figure 3 is the external structure diagram of the band-pass filtering device provided by the embodiment of the present utility model;
[0024] Figure 4 is the internal structure diagram of the band-pass filtering device provided by the embodiment of the present utility model;
[0025] Figure 5 is the component distribution diagram of the band-pass filtering device provided by the embodiment of the present utility model;
[0026] Figure 6 is the simulation diagram of the band-pass filtering device provided by the embodiment of the present utility model.
[0027] In the figure:
[0028] 1. First acoustic resonator; 2. High-pass filtering unit; 3. Second acoustic resonator; 4. Low-pass filtering unit; 5. Substrate; 6. Plastic package; 7. Filter circuit; 8. Acoustic unit; 9. Electrical unit;
[0029] IN, input port; OUT, output port;
[0030] Y1, resonator component one; Y2, resonator component two; Y3, resonator component three;
[0031] L1, first inductor; L2, second inductor; L3, third inductor; L4, fourth inductor; L5, fifth inductor; L6, sixth inductor; L7, seventh inductor; L8, eighth inductor; L9, ninth inductor;
[0032] C1, first capacitor; C2, second capacitor; C3, third capacitor; C4, fourth capacitor; C5, fifth capacitor; C6, sixth capacitor. Specific embodiments
[0033] To make the objectives, technical solutions and advantages of the embodiments of the present utility model clearer, the technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some but not all of the embodiments of the present utility model. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.
[0034] Such as Figures 1 to 6As shown, at least one embodiment provides a filtering circuit 73, which includes: a first acoustic wave resonator 1, a high-pass filtering unit 2, a second acoustic wave resonator 3, and a low-pass filtering unit 4; wherein the first acoustic wave resonator 1, the high-pass filtering unit 2, the second acoustic wave resonator 3, and the low-pass filtering unit 4 are connected in sequence, the first acoustic wave resonator 1 is connected to the input port IN, and the low-pass filtering unit 4 is connected to the output port OUT; the input end of the first acoustic wave resonator 1 is adapted to receive a signal through the input port IN, and the signal is output through the output port OUT after being processed by the first acoustic wave resonator 1, the high-pass filtering unit 2, the second acoustic wave resonator 3, and the low-pass filtering unit 4.
[0035] In some embodiments, by combining the high-pass filtering unit 2 and the low-pass filtering unit 4 and introducing the first acoustic wave resonator 1 and the second acoustic wave resonator 3 at the ports of the high-pass filtering unit 2 and the low-pass filtering unit 4, the width of the transition band on the high-frequency side can be reduced to meet the requirement of a high rectangularity coefficient, thereby achieving the suppression of signals in the N79 frequency band.
[0036] In some embodiments, the first acoustic wave resonator 1 is a thin film bulk acoustic wave resonator, and the number of resonator elements in the first acoustic wave resonator 1 is N, where N≥1, and the resonator elements in the first acoustic wave resonator 1 are connected in series.
[0037] In one of the embodiments, please refer to Figure 2 , the first acoustic wave resonator 1 is composed of a resonator element Y1.
[0038] In some embodiments, please refer to Figure 2 , the first resonator is connected to the first inductor L1 in sequence, the first resonator is connected to the input port IN, and the first inductor L1 is connected to the high-pass filtering unit 2.
[0039] Specifically, the input port IN is connected to the first resonator, the first resonator is in series with the first inductor L1, and the first inductor L1 is connected to the input end of the high-pass filtering unit 2.
[0040] In some embodiments, please refer to Figure 2 , the high-pass filtering unit 2 includes: a first capacitor C1, a second capacitor C2, a second inductor L2, and a third inductor L3; both ends of the first capacitor C1 are respectively connected to the first acoustic wave resonator 1 and the second acoustic wave resonator 3; one end of the second capacitor C2 and one end of the second inductor L2 are respectively connected to both ends of the first capacitor C1, and the other end of the second capacitor C2 is grounded through the third inductor L3, and the other end of the second inductor L2 is grounded.
[0041] Specifically, the first capacitor C1, the second capacitor C2, the second inductor L2, and the third inductor L3 form a third-order high-pass filter. By adding the second capacitor C2 to the branch, an out-of-band zero is introduced at the low-frequency end, increasing the out-of-band suppression ratio.
[0042] In some embodiments, the high-pass filtering unit 2 can change the order to increase the out-of-band suppression ratio, or a multi-stage cascading method can be adopted to introduce more acoustic resonators, thereby reducing the width of the transition band.
[0043] In some embodiments, the second acoustic resonator 3 is a thin-film bulk acoustic resonator, and the number of resonator elements in the second acoustic resonator 3 is N, where N≥1, and the resonator elements in the first acoustic resonator 1 are connected in series.
[0044] In one of the embodiments, please refer to Figure 2 , the second acoustic resonator 3 is composed of the resonator element two Y2 and the resonator element three Y3, and the resonator element two Y2 and the resonator element three Y3 have the same parameters.
[0045] In some embodiments, please refer to Figure 2 , the fourth inductor L4, the second acoustic resonator 3, and the fifth inductor L5 are connected in sequence, and the fourth inductor L4 is connected to the high-pass filtering unit 2, and the fifth inductor L5 is connected to the low-pass filtering unit 4.
[0046] Specifically, the output end of the high-pass filtering unit 2 is connected in series with the fourth inductor L4, the fourth inductor L4 and the resonator element two Y2 are connected in series, the resonator element three Y3 and the fifth inductor L5 are connected in series, and the fifth inductor L5 is connected to the input end of the low-pass filtering unit 4.
[0047] In some embodiments, please refer to Figure 2 , the low-pass filtering unit 4 includes: a sixth inductor L6, a seventh inductor L7, an eighth inductor L8, a third capacitor C3, a fourth capacitor C4, and a ninth inductor L9; the sixth inductor L6, the seventh inductor L7, and the eighth inductor L8 are connected in sequence, the sixth inductor L6 is connected to the second acoustic resonator 3, and the eighth inductor L8 is connected to the output port OUT; one end of the third capacitor C3 and one end of the fourth capacitor C4 are respectively connected to both ends of the seventh inductor L7, and the other end of the third capacitor C3 and the other end of the fourth capacitor C4 are both connected to one end of the ninth inductor L9, and the other end of the ninth inductor L9 is grounded.
[0048] In some embodiments, the low-pass filtering unit 4 can change the order to increase the out-of-band suppression ratio, or a multi-stage cascading method can be adopted to introduce more acoustic resonators, thereby reducing the width of the transition band.
[0049] Specifically, the sixth inductor L6, the seventh inductor L7, the eighth inductor L8, the third capacitor C3, the fourth capacitor C4, and the ninth inductor L9 form a fifth-order low-pass filter.
[0050] In some embodiments, referring to Figure 2 , the low-pass filter unit 4 further includes: a fifth capacitor C5; the fifth capacitor C5 is connected in parallel with the sixth inductor L6.
[0051] Specifically, connecting the fifth capacitor C5 in parallel with the sixth inductor L6 can increase the suppression degree of the low-pass filter unit 4.
[0052] In some embodiments, referring to Figure 2 , the low-pass filter unit 4 further includes: a sixth capacitor C6; the sixth capacitor C6 is connected in parallel with the seventh inductor L7.
[0053] Specifically, connecting the sixth capacitor C6 in parallel with the seventh inductor L7 can increase the suppression degree of the low-pass filter unit 4.
[0054] Specifically, connecting the fifth capacitor C5 in parallel with the sixth inductor L6 and connecting the sixth capacitor C6 in parallel with the seventh inductor L7 can introduce two suppression zeros at high frequencies.
[0055] Specifically, referring to Figure 6 , after simulating the filter circuit 73, the filter circuit 73 can achieve a center frequency of 3300 MHz to 4200 MHz, preferably 3750 MHz; a bandwidth of 900 MHz, an insertion loss better than 2.5 dB, a stopband suppression degree of 30 dB from DC to 2690 MHz, a suppression better than 30 dB from 4400 MHz to 5000 MHz, and a suppression better than 30 dB from 5150 MHz to 7125 MHz.
[0056] As Figures 1 to 6 shown, at least one embodiment provides a band-pass filtering device, which includes: the filter circuit 73, the substrate 5, and the plastic package 6 provided in the above embodiments; wherein a first installation cavity and a second installation cavity are provided between the plastic package 6 and the substrate 5; the first acoustic resonator 1 and the second acoustic resonator 3 in the filter circuit 73 are located in the first installation cavity, and the high-pass filter unit 2 and the low-pass filter unit 4 are located in the second installation cavity.
[0057] Specifically, referring to Figures 4 to 5 , some inductors in the filter circuit 73 are installed on the substrate 5, and the substrate 5 is prepared by a multi-layer lamination process and includes a ceramic substrate 5 or a PCB substrate 5.
[0058] Specifically, referring to Figures 4 to 5 , the first acoustic resonator 1 and the second acoustic resonator 3 belong to the acoustic unit 8 and are integrally installed together.
[0059] Specifically, the functions of the first acoustic wave resonator 1 and the second acoustic wave resonator 3 are to reduce the bandwidth of the transition band.
[0060] Specifically, please refer to Figures 4 to 5 , the high-pass filter unit 2 and the low-pass filter unit 4 belong to the electrical unit 9 and are integrally installed together.
[0061] Specifically, please refer to Figures 4 to 5 , the high-pass filter unit 2 and the low-pass filter unit 4 are fabricated using glass as the substrate, and silicon, gallium arsenide, glass, or sapphire can also be used as the substrate material, and are formed by photolithography, etching, deposition, or sputtering.
[0062] Specifically, the plastic package 6 is a polymer-filled housing, and its purpose is to isolate the influence of the external environment on the chip.
[0063] Specifically, the filter circuit 73 combines the electrical and acoustic characteristics to achieve the design of a band-pass filter with miniaturization, large bandwidth, narrow transition band, and high rectangularity factor.
[0064] Specifically, the overall package size of the band-pass filtering device is 1.6 * 0.8 * 0.5 mm.
[0065] Specifically, the band-pass filtering device has the characteristics of small size, light weight, low loss, high suppression, wide passband, high rectangularity factor, etc., and is fabricated using a mature semiconductor process with high process precision and is suitable for mass production.
[0066] In summary, the present utility model combines the high-pass filter unit and the low-pass filter unit, and at the same time introduces the first acoustic wave resonator and the second acoustic wave resonator at the ports of the high-pass filter unit and the low-pass filter unit, which can reduce the width of the transition band on the high-frequency side, meet the requirement of high rectangularity factor, and further achieve the suppression of the signal in the N79 frequency band.
[0067] All the devices (components without specific structures) selected in this application are common standard components or components known to those skilled in the art, and their structures and principles can be known by those skilled in the art through technical manuals or by conventional experimental methods. Moreover, the software programs involved in this application are all prior arts, and this application does not involve any improvement to the software programs.
[0068] In the description of the embodiments of the present utility model, unless otherwise clearly specified and limited, the terms "mounted", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific situations.
[0069] In the description of the present utility model, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present utility model. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.
[0070] In several embodiments provided by the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. The device embodiments described above are only illustrative. For example, the division of the units is only a logical function division, and there can be other division methods in actual implementation. For another example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed coupling or direct coupling or communication connection to each other can be through some communication interfaces. The indirect coupling or communication connection of the devices or units can be in an electrical, mechanical or other form.
[0071] Based on the above inspiration from the ideal embodiments of the present utility model, through the above description, relevant staff can completely make various changes and modifications without departing from the technical idea of the present utility model. The technical scope of the present utility model is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.
Claims
1. A filter circuit, characterized in that: include: A first acoustic wave resonator, a high pass filter unit, a second acoustic wave resonator and a low pass filter unit; in The first acoustic wave resonator, the high-pass filter unit, the second acoustic wave resonator, and the low-pass filter unit are connected in sequence, the first acoustic wave resonator is connected to the input port, and the low-pass filter unit is connected to the output port; The input end of the first acoustic wave resonator is suitable for receiving a signal through an input port, and the signal is processed by the first acoustic wave resonator, the high-pass filter unit, the second acoustic wave resonator, and the low-pass filter unit and then output through an output port.
2. The filter circuit according to claim 1, characterized in that: The first acoustic wave resonator is a thin film bulk acoustic wave resonator, and the number of resonator elements in the first acoustic wave resonator is N, wherein N≥1, and the resonator elements in the first acoustic wave resonator are connected in series.
3. The filter circuit according to claim 1, characterized in that: The first acoustic wave resonator and the first inductor are connected in sequence, the first acoustic wave resonator is connected to the input port, and the first inductor is connected to the high-pass filter unit.
4. The filter circuit according to claim 1, characterized in that: The high-pass filter unit includes: a first capacitor, a second capacitor, a second inductor and a third inductor; Two ends of the first capacitor are connected to the first acoustic wave resonator and the second acoustic wave resonator respectively; One end of the second capacitor and one end of the second inductor are connected to two ends of the first capacitor respectively, and the other end of the second capacitor is grounded through the third inductor, and the other end of the second inductor is grounded.
5. The filter circuit according to claim 1, characterized in that: The second acoustic wave resonator is a thin film bulk acoustic wave resonator, and the number of resonator elements in the second acoustic wave resonator is N, wherein N≥1, and the resonator elements in the first acoustic wave resonator are connected in series.
6. The filter circuit according to claim 1, characterized in that: The fourth inductor, the second acoustic wave resonator and the fifth inductor are connected in sequence, and the fourth inductor is connected to the high-pass filter unit, and the fifth inductor is connected to the low-pass filter unit.
7. The filter circuit according to claim 1, characterized in that: The low-pass filter unit includes: a sixth inductor, a seventh inductor, an eighth inductor, a third capacitor, a fourth capacitor and a ninth inductor; The sixth inductor, the seventh inductor, and the eighth inductor are connected in sequence, the sixth inductor is connected to the second acoustic wave resonator, and the eighth inductor is connected to the output port; One end of the third capacitor and one end of the fourth capacitor are respectively connected to two ends of the seventh inductor, and the other end of the third capacitor and the other end of the fourth capacitor are both connected to one end of the ninth inductor, and the other end of the ninth inductor is grounded.
8. The filter circuit according to claim 7, characterized in that: The low-pass filtering unit further includes: a fifth capacitor; The fifth capacitor and the sixth inductor are connected in parallel.
9. The filter circuit according to claim 7, characterized in that: The low-pass filtering unit further includes: a sixth capacitor; The sixth capacitor and the seventh inductor are connected in parallel.
10. A bandpass filter device, characterized in that: include: The filter circuit, substrate and plastic package as described in any one of claims 1 to 9; in A first installation cavity and a second installation cavity are provided between the plastic package shell and the substrate; The first acoustic wave resonator and the second acoustic wave resonator in the filter circuit are located in the first installation cavity, and the high-pass filter unit and the low-pass filter unit are located in the second installation cavity.