Bandpass filter

Abstract

The embodiment of the present application discloses a kind of band-pass filters, it includes: dielectric substrate;At least two open-loop resonators are arranged on the dielectric substrate;Wherein, each open-loop resonator includes first resonant loop and second resonant loop, the first resonant loop, the second resonant loop are equipped with an opening;The second resonant loop is reversely placed in the resonant cavity of the first resonant loop, and concentric with the first resonant loop;The first resonant loop in adjacent two open-loop resonators is connected by a microstrip line.This band-pass filter provided by the embodiment of the present application has good performance, compact size and is easy to implement, when the related parameters of the open-loop resonator change, the range of the working frequency band of the band-pass filter can be effectively tuned, so that the band-pass filter has robust tunability.

Description

Technical Field

[0001] This application relates to the field of communication technology, and in particular to a bandpass filter. Background Technology

[0002] A bandpass filter is a passive device used to separate microwave signals of different frequencies. As an important component of the RF transceiver front end, the performance of the bandpass filter directly affects the overall performance of the communication system. The split-ring resonator (SRR) has low radiation loss and high performance, and is considered an ideal resonator for the miniaturization design of microwave devices. It can be widely used in the design of various bandpass filters.

[0003] Currently, when engineers in various countries improve bandpass filters using open-loop resonators, they typically adjust relevant parameters of the open-loop resonator, such as metal width, gap distance, crack width, number of rings, spacing between rings, and number of cracks, to achieve microstrip filter tuning. However, bandpass filters constructed from open-loop resonators generally lack robust tunability. When the relevant parameters of the open-loop resonator change, due to uncertainties in the filtering system, the filtering error system of the bandpass filter within the tunable frequency range is prone to stabilization, failing to meet the performance specifications of the bandpass filter.

[0004] Therefore, how to design a robust and tunable bandpass filter is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application provides a bandpass filter, aiming to solve the technical problem that bandpass filters in the prior art lack robust tunability.

[0006] To address the aforementioned technical problems, embodiments of this application provide a bandpass filter, comprising:

[0007] Dielectric substrate;

[0008] At least two open-loop resonators are disposed on the dielectric substrate;

[0009] Each of the open-loop resonators includes a first resonant ring and a second resonant ring, both of which have an opening; the second resonant ring is placed in the resonant cavity of the first resonant ring in the opposite direction and is concentric with the first resonant ring;

[0010] The first resonant rings in two adjacent open-loop resonators are connected by a microstrip line.

[0011] Furthermore, in the bandpass filter, the first resonant ring and the second resonant ring are each formed by bending and folding microstrip lines of different lengths.

[0012] Furthermore, in the bandpass filter, the ratio of the spacing of the openings of the first resonant ring to the length of the microstrip line where the first resonant ring is located is greater than 0.041 and less than 0.074.

[0013] Furthermore, in the bandpass filter, two adjacent open-loop resonators are symmetrically arranged on the dielectric substrate.

[0014] Furthermore, in the bandpass filter, an open-loop resonator is respectively disposed at each of the opposite ends of the dielectric substrate.

[0015] Furthermore, the bandpass filter also includes an input feed line and an output feed line;

[0016] The input feed line and the output feed line are both disposed on the dielectric substrate and are respectively connected to the first resonant ring in the open-loop resonator at opposite ends of the dielectric substrate.

[0017] Furthermore, in the bandpass filter, the ratio of the width of the open-loop resonator to the width of the dielectric substrate is greater than 0.5 and less than 1, and the ratio of the overall length of two adjacent open-loop resonators to the length of the dielectric substrate is greater than 0.5 and less than 1.

[0018] Furthermore, in the bandpass filter, all the open-loop resonators have the same size and structure.

[0019] Furthermore, in the bandpass filter, the first resonant ring and the second resonant ring are circular resonant rings or rectangular resonant rings.

[0020] Furthermore, in the bandpass filter, the resonant frequency of the bandpass filter is 9.21–10.03 GHz.

[0021] The bandpass filter provided in this application not only boasts excellent performance, compact size, and ease of implementation, but also exhibits robust tunability. It can effectively tune the operating frequency range of the bandpass filter when the relevant parameters of the open-loop resonator change. Furthermore, the bandpass filter provided in this application demonstrates superior insertion loss and return loss, high selectivity, good in-band and out-of-band performance, and a steep passband cutoff edge, providing some harmonic suppression capability. It is suitable for modern wireless radio frequency microwave communication and has good integration potential in existing wireless applications. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A schematic diagram of the geometric structure of a bandpass filter provided in an embodiment of this application;

[0024] Figure 2 This is a schematic diagram of the geometric structure of a uniform impedance resonator provided in an embodiment of this application;

[0025] Figure 3 This is a schematic diagram of the geometric structure of an open-loop resonator provided in an embodiment of this application;

[0026] Figure 4 Equivalent circuit diagram of an open-loop resonator provided in the embodiments of this application;

[0027] Figure 5 The return loss S of the bandpass filter provided in the embodiments of this application 11 Electromagnetic simulation results diagram;

[0028] Figure 6 The insertion loss S of the bandpass filter provided in the embodiments of this application 21 Electromagnetic simulation results diagram;

[0029] Figure 7 The figure shows the S-parameter electromagnetic simulation results of the bandpass filter provided in the embodiment of this application. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] It should be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the application. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0032] It should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., that may be mentioned in the description of this application, indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0033] As analyzed in the background section of this application, existing bandpass filters do not possess robust tunability. To address the aforementioned technical problems, this application provides a bandpass filter.

[0034] Please see Figure 1 and Figure 3 , Figure 1 This is a schematic diagram of the geometric structure of a bandpass filter provided in an embodiment of this application. Figure 3 This is a schematic diagram of the geometric structure of an open-loop resonator provided in an embodiment of this application.

[0035] like Figure 1 and Figure 3 As shown, a bandpass filter includes:

[0036] Dielectric substrate;

[0037] At least two open-loop resonators are disposed on the dielectric substrate;

[0038] Each of the open-loop resonators includes a first resonant ring 11 and a second resonant ring 12, both of which have an opening. The second resonant ring 12 is placed in the resonant cavity of the first resonant ring 11 in the opposite direction and is concentric with the first resonant ring 11. The first resonant rings 11 in two adjacent open-loop resonators are connected by a microstrip line.

[0039] Specifically, the bandpass filter is composed of at least two open-loop resonators cascaded on a dielectric substrate using microstrip lines; that is, the number of open-loop resonators on the dielectric substrate is at least two or more. This application aims to ensure the bandpass filter possesses robust tunability while minimizing its size. Therefore, this application preferably selects a bandpass filter composed of two open-loop resonators cascaded on a dielectric substrate using microstrip lines.

[0040] In this embodiment, each open-loop resonator consists of two resonant rings, namely a first resonant ring 11 and a second resonant ring 12. The two resonant rings in each open-loop resonator are provided with two symmetrical openings, that is, the first resonant ring 11 and the second resonant ring 12 are respectively provided with mutually symmetrical openings. This allows the open-loop resonator to induce a loop current when it is subjected to an electromagnetic field, and thus negative permeability and absorption peaks will appear at the resonant frequency.

[0041] The bandpass filter provided in this application not only has good performance, compact size, and is easy to implement, but also has robust tunability. When the relevant parameters of the open-loop resonator change, it can effectively tune the operating frequency range of the bandpass filter. At the same time, the bandpass filter also exhibits excellent insertion loss and return loss, high frequency performance, good in-band and out-of-band performance, and a steep passband cutoff edge, which has a certain ability to suppress harmonics. It is suitable for modern wireless radio frequency microwave communication fields and has good integration potential in existing wireless applications.

[0042] Currently, the main consideration in designing X-band bandpass filters is how to reduce passband loss while minimizing filter size. For example, the stepped impedance type substrate integrated coaxial line bandpass filter is constructed based on stepped impedance resonators (SIRs) combined with substrate integrated coaxial line (SICL) technology. Furthermore, a planar structure is designed to provide excitation for the SICL resonator by guiding the SICL resonator with a coplanar wave, addressing the connection between the SICL resonator and other planar circuits. Among them, substrate integrated coaxial line technology is a technology that plans out traditional coaxial lines. SICL, like traditional coaxial lines, is a shielded, non-dispersive TEM waveguide structure. It is fabricated using high-resistivity silicon as a substrate and thick, low-loss-factor benzocyclobutene (BCB) as a dielectric, using MEMS (Microelectromechanical systems) manufacturing process. Multilayer metal conduction bands are designed inside the low-temperature co-fired ceramic device or module. The electromagnetic interaction between the multilayer metal conduction bands includes both horizontal coupling between each layer and vertical coupling between different layers. Its topology is relatively complex, which leads to a relatively high actual production and processing cost for the bandpass filter. Most importantly, it is impossible to effectively tune its operating frequency range, thus making the bandpass filter lack robust tunability.

[0043] The bandpass filter provided in this application, when applied to X-band tuning, can easily achieve robust tunability of the resonant frequency, especially in the 9.21–10.03 GHz range. In other words, considering the uncertainties in the filtering system, the bandpass filter provided in this application not only ensures asymptotic stability of the filtering error system within the tunable frequency range but also meets the performance specifications of a bandpass filter. Furthermore, the bandpass filter provided in this application can be used in short-range fire control radar applications, thus it can also be used in X-band radar applications requiring narrow and sharp filtering circuits.

[0044] In some embodiments, the first resonant ring 11 and the second resonant ring 12 are each formed by bending and folding microstrip lines of different lengths. The length of the microstrip line corresponding to the first resonant ring 11 is greater than the length of the microstrip line corresponding to the second resonant ring 12, and the widths of the two microstrip lines may be equal or unequal. Preferably, in this embodiment, the width of the microstrip line corresponding to the first resonant ring 11 is greater than the width of the microstrip line corresponding to the second resonant ring 12.

[0045] Specifically, a microstrip line is a microwave transmission line consisting of a single conductor strip supported on a dielectric substrate. It is suitable for fabricating planar transmission lines for microwave integrated circuits, and features small size, light weight, wide operating bandwidth, high reliability, and low manufacturing cost. Microstrip lines can be used to directly fabricate... Figure 2 The Uniform Impedance Resonator (UIR) shown has a simple basic structure. The resonance condition of the UIR mainly depends on the length of the microstrip line, so it is easy to design and can be widely used.

[0046] In this embodiment, the first resonant ring 11 and the second resonant ring 12 are formed by bending microstrip lines of different lengths. That is, each open-loop resonator in this application can be considered as being formed by bending and folding two uniform impedance resonators of different lengths. Figure 3 As shown, the first resonant ring 11 and the second resonant ring 12 are respectively provided with mutually symmetrical openings. The main excitation method of the open-loop resonator constructed by them is to achieve this through an axial magnetic field or magnetic flux perpendicular to the ring surface. Figure 3 As can be seen, the open-loop resonator is a miniaturized and compact structure with cross-polarization characteristics. Therefore, it can be excited by a time-varying electric field parallel to the toroidal surface. However, the efficiency of magnetic field excitation is much higher than that of electric field excitation, so an axial magnetic field is required for it to work. Thus, the open-loop resonator can be equivalently represented as a resonant circuit consisting of two capacitors 1 / 2Cr, a resistor R, and an inductor Lr connected in series, as shown below. Figure 4 The equivalent circuit shown.

[0047] Because open-loop resonators have small electrical dimensions and their physical dimensions are much smaller than the wavelength corresponding to their resonant frequency, typically reaching about one-tenth of the guided wave wavelength, and have a high quality factor Q, this application uses a bandpass filter designed by cascading multiple open-loop resonators on a dielectric substrate. This not only easily achieves robust tunability of the resonant frequency, but also exhibits excellent insertion loss and return loss, high frequency performance, good in-band and out-of-band performance, and a steep passband cutoff edge, providing a certain degree of harmonic suppression.

[0048] In some embodiments, the microstrip line corresponding to the first resonant ring 11 is bent and folded to adjust the width of the opening of the first resonant ring 11.

[0049] In this embodiment, when the microstrip line corresponding to the first resonant ring 11 is bent and folded, the width of the opening of the first resonant ring 11 can be adjusted by controlling the spacing between the beginning and end of the microstrip line. That is, the spacing between the beginning and end of the microstrip line is the opening of the first resonant ring 11. In this way, the bandpass filter can be controlled in a specific band (such as 9.21 to 10.03 GHz) of tunable frequency range, and robust tunability of the resonant frequency can be achieved more easily.

[0050] In some specific embodiments, the ratio of the spacing of the openings of the first resonant ring 11 to the length of the microstrip line where the first resonant ring 11 is located is greater than 0.041 and less than 0.074.

[0051] In this embodiment, by limiting the ratio of the spacing of the openings of the first resonant ring 11 to the length of the microstrip line where the first resonant ring 11 is located to between 0.041 and 0.074, the bandpass filter can be controlled in the tunable frequency range of the X-band, especially in the frequency range of 9.21 to 10.03 GHz, and robust tunability of the resonant frequency can be easily achieved.

[0052] In some embodiments, two adjacent open-loop resonators are symmetrically arranged on the dielectric substrate, and each open-loop resonator has the same size and structure.

[0053] In this embodiment, the first resonant ring 11 in each open-loop resonator is formed by bending and folding microstrip lines of the same length and width. Similarly, the second resonant ring 12 in each open-loop resonator is also formed by bending and folding microstrip lines of the same length and width. By symmetrically arranging two adjacent open-loop resonators on a dielectric substrate, and ensuring that the open-loop resonators on the bandpass filter have the same size and structure, this application not only easily achieves robust tunability of the X-band resonant frequency but also makes the bandpass filter compact and easy to implement.

[0054] In some embodiments, such as Figure 1As shown, the bandpass filter provided in this application further includes an input feed line 21 and an output feed line 22; wherein, the input feed line 21 and the output feed line 22 are both disposed on the dielectric substrate and are respectively connected to the first resonant ring 11 at opposite ends of the dielectric substrate.

[0055] Specifically, the input feed line 21 and the output feed line 22 are respectively located at opposite ends of the dielectric substrate, such as the left and right ends of the dielectric substrate. The material of the input feed line 21 and the output feed line 22 can be copper foil, but is not limited to copper foil.

[0056] It should be noted that the microstrip lines used in the first resonant ring 11 and the second resonant ring 12, the microstrip lines connecting two adjacent first resonant rings 11, the input feed line 21 of the bandpass filter, and the output feed line 22 in this application can all be made of copper foil, but are not limited to copper foil. Furthermore, the width and length of the microstrip lines used in the first resonant ring 11 and the second resonant ring 12, the microstrip lines connecting two adjacent first resonant rings 11, the input feed line 21 of the bandpass filter, and the output feed line 22 can be selected and set according to actual applications, and this application does not impose specific limitations.

[0057] In some embodiments, the ratio of the width of the open-loop resonator to the width of the dielectric substrate is greater than 0.5 and less than 1, and the ratio of the overall length of two adjacent open-loop resonators to the length of the dielectric substrate is greater than 0.5 and less than 1.

[0058] Specifically, this application limits the ratio of the width of the open-loop resonator to the width of the dielectric substrate to between 0.5 and 1, and also limits the ratio of the overall length of two adjacent open-loop resonators to the length of the dielectric substrate to between 0.5 and 1. This makes the bandpass filter compact and easy to implement, and also makes it easier to achieve robust tunability of the X-band resonant frequency.

[0059] In some embodiments, the first resonant ring 11 and the second resonant ring 12 are circular resonant rings or rectangular resonant rings. Specifically, the shape of the open-loop resonator composed of the first resonant ring 11 and the second resonant ring 12 can be circular, rectangular, or other shapes. That is, the open-loop resonator mentioned in this application is not limited to circular and rectangular shapes. Its specific shape can be designed according to actual needs, and this application does not make specific limitations.

[0060] The present application will now be described in conjunction with preferred embodiments and implementation methods.

[0061] This preferred embodiment is an X-band robust tunable bandpass filter based on an open-loop resonator, such as... Figure 1As shown, the bandpass filter includes a dielectric substrate, two open-loop resonators, an input feed line 21, and an output feed line 22. Each open-loop resonator includes a first resonant ring 11 and a second resonant ring 12. Both the first resonant ring 11 and the second resonant ring 12 have an opening. The second resonant ring 12 is placed in the resonant cavity of the first resonant ring 11 in opposite directions and is concentric with the first resonant ring 11. Two adjacent first resonant rings 11 are connected by a microstrip line to realize the cascading of two open-loop resonators. The input feed line 21 and the output feed line 22 are both disposed on the dielectric substrate and connected to the first resonant rings 11 at the left and right ends of the dielectric substrate, respectively.

[0062] In this embodiment, the overall area of ​​the bandpass filter is 24.0mm × 6mm, and the dimensions of the dielectric substrate are 24.0mm × 12.0mm. The microstrip lines used in the first resonant ring 11 and the second resonant ring 12, the microstrip lines connecting the two first resonant rings 11, the input feed line 21, and the output feed line 22 are all made of copper foil. Both the first resonant ring 11 and the second resonant ring 12 are rectangular. The dielectric substrate has a length of 24mm, a width of 12mm, a dielectric constant of 2.65, and a thickness of 1mm. The dielectric substrate is made of F4B material. The impedance of the input feed line 21 and the output feed line 22 is 50 ohms. The length of both the input feed line 21 and the output feed line 22 is L0 = 4mm, and the width of both is W0 = 2.8mm. The length of the first resonant ring 11 is L1 = 6 mm, the height of the resonant cavity of the first resonant ring 11 is L2 = 4 mm, the distance from each end of the opening of the first resonant ring 11 to its respective inner wall is L3 = 1.35 mm, the length of the microstrip line connecting the two first resonant rings 11 is L4 = 4 mm, the length of the second resonant ring 12 is L5 = 2.5 mm, the height of the resonant cavity of the second resonant ring 12 is L6 = 1.5 mm, the distance from each end of the opening of the second resonant ring 12 to its respective inner wall is L7 = 0.35 mm, the width of the microstrip line where the first resonant ring 11 is located is W1 = 1 mm, the width of the microstrip line where the second resonant ring 12 is located is W2 = 0.5 mm, the spacing g1 between the openings of the first resonant ring 11 is not less than 0.95 and not greater than 1.65 mm, and the spacing g2 between the openings of the second resonant ring 12 is g2 = 0.8 m.

[0063] The bandpass filter mentioned in the embodiments of this application can be electromagnetically simulated using common high-frequency electromagnetic simulation software, and its performance can be demonstrated numerically.

[0064] This application uses ANSYS HFSS 15.0 to simulate the above-mentioned bandpass filter structure. During the simulation, the aperture spacing of the first resonant ring 11 in the bandpass filter is 0.95mm, 1.05mm, 1.15mm, 1.25mm, 1.3mm, 1.35mm, 1.45mm, 1.55mm, and 1.65mm, respectively. The simulation results are available in the [link to simulation results]. Figures 5 to 7 , Figure 5 The return loss S of the bandpass filter provided in the embodiments of this application 11 Electromagnetic simulation result diagram, Figure 6 The insertion loss S of the bandpass filter provided in the embodiments of this application 21 Electromagnetic simulation result diagram, Figure 7 The figure shows the S-parameter electromagnetic simulation results of the bandpass filter provided in the embodiment of this application.

[0065] from Figures 5 to 7 As can be seen from the above, the X-band robust tunable bandpass filter based on an open-loop resonator provided in this preferred embodiment exhibits good overall performance. The basic center resonant frequency of the bandpass filter is 9.66 GHz, and the -3 dB relative bandwidth in the range of 9.55–9.75 GHz is 2.07%. Simultaneously, the bandpass filter demonstrates high -3 dB attenuation and stopband performance, resulting in high selectivity. This allows the bandpass filter to be used in X-band radar applications requiring narrow and sharp filtering circuits. Furthermore, the bandpass filter exhibits a passband return loss better than 24 dB and an insertion loss of 0.36 dB.

[0066] In summary, by varying the spacing of the openings in the first resonant ring 11 within the range of 0.95–1.65 mm, this application can control the tunable frequency range of the bandpass filter from 9.21 to 10.03 GHz, thereby easily achieving robust tunability of the bandpass filter's resonant frequency. Furthermore, the bandpass filter provided in the above embodiments also provides an acceptable short-range fire control radar application band, which can be used in X-band radar applications requiring narrow and sharp filtering circuits. In addition, this bandpass filter exhibits superior insertion loss, return loss, and compact size, high frequency performance, good in-band and out-of-band performance, a steep passband cutoff edge, and a certain degree of harmonic suppression capability.

[0067] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A bandpass filter, characterized in that, include: Dielectric substrate; At least two open-loop resonators are disposed on the dielectric substrate, and the open-loop resonators are cascaded on the dielectric substrate using microstrip lines. Each of the open-loop resonators includes a first resonant ring and a second resonant ring, both of which have an opening; the second resonant ring is placed in the resonant cavity of the first resonant ring in the opposite direction and is concentric with the first resonant ring; The ratio of the spacing between the openings of the first resonant ring to the length of the microstrip line on which the first resonant ring is located is greater than 0.041 and less than 0.074; the first resonant ring and the second resonant ring are each formed by bending and folding microstrip lines of different lengths. The first resonant rings in two adjacent open-loop resonators are connected by a microstrip line; the microstrip line corresponding to the first resonant ring is bent and folded to adjust the width of the opening of the first resonant ring, thereby controlling the tunable frequency range of the bandpass filter in a specific band; the spacing between the openings of the first resonant rings is 0.95 mm to 1.65 mm, and the resonant frequency of the bandpass filter is 9.21 to 10.03 GHz; the length of the microstrip line corresponding to the first resonant ring is greater than the length of the microstrip line corresponding to the second resonant ring, and the width of the microstrip line corresponding to the first resonant ring is greater than the width of the microstrip line corresponding to the second resonant ring. It also includes an input feed line and an output feed line; wherein the input feed line and the output feed line are both disposed on the dielectric substrate and are respectively connected to the first resonant ring in the open-loop resonator at opposite ends of the dielectric substrate.

2. The bandpass filter according to claim 1, characterized in that, Two adjacent open-loop resonators are symmetrically arranged on the dielectric substrate.

3. The bandpass filter according to claim 2, characterized in that, An open-loop resonator is disposed at each of the opposite ends of the dielectric substrate.

4. The bandpass filter according to any one of claims 1-3, characterized in that, The ratio of the width of the open-loop resonator to the width of the dielectric substrate is greater than 0.5 and less than 1, and the ratio of the overall length of two adjacent open-loop resonators to the length of the dielectric substrate is greater than 0.5 and less than 1.

5. The bandpass filter according to any one of claims 1-3, characterized in that, All of the open-loop resonators described have the same dimensions and structure.

6. The bandpass filter according to any one of claims 1-3, characterized in that, The first resonant ring and the second resonant ring are either circular or rectangular resonant rings.

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