Miniaturized bandstop filter

Abstract

This invention discloses a miniaturized band-stop filter, comprising a dielectric substrate with a front and a back side disposed opposite to each other. The front side has a main transmission line extending from a first end to a second end, and multiple microstrip line resonators connected to the main transmission line. Both the main transmission line and the microstrip line resonators are formed using microstrip lines. A grounded metal layer is formed on the back side. In this invention, the main transmission line adopts a curved structure, which can significantly reduce the physical span of the main transmission line. The use of microstrip line resonators facilitates miniaturization and allows for convenient tuning of the resonant frequency and suppression bandwidth, adapting to various application scenarios.

Description

Technical Field

[0001] This invention belongs to the field of dielectric filters, and in particular relates to a miniaturized band-stop filter. Background Technology

[0002] In mobile communication, satellite communication, radar, and RF front-end systems, band-stop filters are frequently used to suppress specific interference frequency bands and ensure the normal operation of communication links. Traditional distributed band-stop filters typically employ long transmission lines or cascaded multi-resonator structures, resulting in large size and low integration. Furthermore, parasitic capacitance exists between the resonator and the ground metal layer, leading to resonant frequency shifts, narrower passbands, and decreased suppression, making it difficult to meet the miniaturization, wide passband, and high suppression requirements of modern RF systems. Therefore, it is necessary to propose a band-stop filter with a compact structure, low parasitic effects, and a wide passband. Summary of the Invention

[0003] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a miniaturized band-stop filter.

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A miniaturized band-stop filter includes a dielectric substrate, the dielectric substrate having a front side and a back side disposed opposite to each other; the front side has a main transmission line extending from a first end to a second end thereon and a plurality of microstrip line resonators connected to the main transmission line, the so-called main transmission line and microstrip line resonators are both formed of microstrip lines, the main transmission line is curved, and a ground metal layer is formed on the back side.

[0005] Furthermore, the material of the dielectric substrate is a low-loss dielectric material; and / or Both the microstrip line and the ground metal layer are gold-plated.

[0006] Furthermore, an input / output port is formed at each end of the main transmission line. The main transmission line includes a first transmission line connecting the input / output port to an adjacent microstrip line resonator and a second transmission line connecting two adjacent microstrip line resonators. The length of the second transmission line is adapted to a quarter wavelength of the center frequency of the band-stop filter.

[0007] Furthermore, the first transmission line includes a first horizontal segment connected to the input / output port, a second horizontal segment connected to an adjacent microstrip line resonator, and a first curved segment connecting the first horizontal segment and the second horizontal segment.

[0008] Furthermore, the second transmission line includes a third horizontal segment connected to a microstrip line resonator, a fourth horizontal segment connected to another microstrip line resonator, and a second curved segment connecting the third horizontal segment and the fourth horizontal segment.

[0009] Furthermore, the second curve segment includes a second arc segment connected to the third horizontal segment, a vertical segment connected to the second arc segment, and a third arc segment connecting the vertical segment and the fourth horizontal segment.

[0010] Furthermore, the miniaturized band-stop filter is a fourth-order band-stop filter, and the plurality of microstrip line resonators include a first resonator, a second resonator, a third resonator, and a fourth resonator connected sequentially on the main transmission line. The first resonator and the fourth resonator have the same resonant frequency, and the second resonator and the third resonator have the same resonant frequency.

[0011] Furthermore, the microstrip line resonator includes a serpentine microstrip line and a capacitor disk, with one end of the serpentine microstrip line connected to the main transmission line and the other end of the main transmission line connected to the capacitor disk.

[0012] Furthermore, a hollow area formed by removing the ground metal layer is provided below each area where the microstrip resonator is located.

[0013] Furthermore, a groove is formed in each of the hollowed-out areas on the back side.

[0014] In this invention, the main transmission line adopts a curved structure, which can significantly reduce the physical span of the main transmission line. The microstrip line resonator includes a combination structure of a serpentine microstrip line and a capacitor disk. By employing a curved transmission line and a serpentine bending resonator structure, the physical span of the resonator is significantly reduced while maintaining the electrical length of the serpentine microstrip line. The overall volume of the resulting band-stop filter is significantly smaller than that of traditional structures, achieving miniaturization. Furthermore, the resonant frequency and suppression bandwidth can be easily tuned by adjusting the length, number of bends, linewidth, and capacitor disk area of ​​the serpentine microstrip line, adapting to various application scenarios. In addition, this embodiment eliminates the parasitic capacitance of the microstrip line resonator by forming a hollow area or groove structure on the ground metal layer on the back, avoiding resonant frequency shift, thereby widening the passband range, improving passband flatness and transmission efficiency, and showing broad application prospects. Attached Figure Description

[0015] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the structure of an embodiment of the miniaturized bandstop filter of the present invention.

[0016] Figure 2 for Figure 1 Top view.

[0017] Figure 3 for Figure 1 A bottom view.

[0018] Figure 4 This is a schematic diagram of the structure after the groove is formed in the hollowed-out area.

[0019] The diagrams in the instruction manual are labeled as follows: Dielectric substrate 100; Front side 110; Back side 120; Grounding metal layer 121; Main transmission line 200; input / output ports 201, 202; first transmission line 210; first horizontal segment 211; first curved segment 212; second horizontal segment 213; second transmission line 220; third horizontal segment 221; second arc segment 222; vertical segment 223; third arc segment 224; fourth horizontal segment 225; Microstrip line resonator 300; first resonator 310; second resonator 320; third resonator 330; fourth resonator 340. Detailed Implementation

[0020] The following specific examples illustrate the implementation of the present invention. The illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0021] Please see Figure 1 , Figure 1This is a schematic diagram of a miniaturized band-stop filter according to an embodiment of the present invention. The miniaturized band-stop filter of this embodiment includes a dielectric substrate 100. The dielectric substrate 100 is generally made of a high-stability, low-loss dielectric material, enabling the band-stop filter to have lower insertion loss and better transmission performance at high frequencies, thus meeting the requirements of radio frequency microwave systems for low loss and high reliability. In this embodiment, the dielectric substrate 100 is preferably made of alumina ceramic. Compared with conventional polymer dielectrics, glass dielectrics, and other dielectric materials, alumina ceramic has advantages such as lower dielectric loss, better thermal conductivity, higher mechanical strength, and better temperature stability, which can significantly reduce the overall loss of the band-stop filter and improve the performance consistency and service life of the band-stop filter under complex operating conditions and long-term operation. The dielectric substrate 100 includes a front side 110 and a back side 120 disposed opposite to each other. The front side 110 is provided with a main transmission line 200 and a plurality of microstrip line resonators 300. The main transmission line 200 extends from one end of the front side 110 to the other end, forming the main transmission path for radio frequency signals. The plurality of microstrip line resonators 300 are connected to the main transmission line 200, forming a band-stop filter structure. Both the main transmission line 200 and the microstrip line resonators 300 are formed using microstrip lines. Relying on the distributed transmission characteristics of microstrip lines, the band-stop filter can have a stable filtering response and good impedance matching characteristics within the target operating frequency band. The main transmission line 200 is curved to reduce the span of the main transmission line 200. The microstrip line resonators 300 are arranged at intervals along the main transmission line 200, and efficient suppression of specific frequency bands is achieved through coupling.

[0022] In this embodiment, the microstrip lines forming the main transmission line 200 and the microstrip resonator 300 are both constructed using a gold-plated layer structure. Gold in the gold plating layer possesses advantages such as high conductivity, low resistivity, strong oxidation and corrosion resistance, and low high-frequency loss, significantly reducing signal transmission loss and improving conductivity efficiency, while also enhancing the long-term reliability and environmental adaptability of the electrodes. In terms of the fabrication process, to ensure a strong bond and adhesion between the gold plating layer and the dielectric substrate 100, a metal seed layer can be uniformly deposited on the clean surface of the dielectric substrate 100. This seed layer can be made of materials such as titanium, chromium, or titanium-tungsten alloy to improve the adhesion between the gold plating layer and the alumina ceramic substrate, preventing plating peeling, flaking, or excessive contact resistance. Subsequently, a gold layer is deposited on the metal seed layer using electroplating or chemical plating, and then precisely shaped using patterning processes such as photolithography and etching. Finally, a well-patterned and stable gold-plated microstrip line structure is obtained on the front side 110, thereby forming the main transmission line 200 and the microstrip resonator 300.

[0023] Please see Figure 2, an input / output port (201, 202) is formed at each end of the main transmission line 200 for signal access and extraction; the main transmission line 200 includes a first transmission line 210 connecting the input / output ports (201, 202) and the adjacent microstrip line resonator 300 and a second transmission line 220 connecting two adjacent microstrip line resonators 300, and the length of the second transmission line 220 is adapted to a quarter wavelength of the center frequency of the band-stop filter; in this embodiment, the length of the second transmission line 220 can be equal to a quarter wavelength of the center frequency of the band-stop filter.

[0024] To achieve miniaturization of the band-stop filter and reduce the length of the band-stop filter (i.e., the dimension of the dielectric substrate 100 in the Figure 1 x-axis direction in), the first transmission line 210 and the second transmission line 220 can adopt a curved structure, so that the span of the first transmission line 210 and the second transmission line 220 in the length direction of the band-stop filter can be reduced while their electrical lengths remain unchanged. In this embodiment, the first transmission line 210 includes a first horizontal section 211 connected to the input / output port, a second horizontal section 213 connected to the adjacent microstrip line resonator 300, and a first curved section 212 connecting the first horizontal section 211 and the second horizontal section 213. In this embodiment, the first curved section 212 can be formed by splicing two 90° arcs. Of course, the first curved section 212 can also adopt other continuous smooth curve forms.

[0025] The second transmission line 220 includes a third horizontal section 221 connected to a microstrip line resonator 300, a fourth horizontal section 225 connected to another microstrip line resonator 300, and a second curved section connecting the third horizontal section 221 and the fourth horizontal section 225. In this embodiment, the second curved section includes a second arc section 222 connected to the third horizontal section 221, a vertical section 223 connected to the second arc section 222, and a third arc section 224 connecting the vertical section 223 and the fourth horizontal section 225. The second arc section 222 and the third arc section 224 can adopt 90° arc curves. Of course, other continuous smooth curve forms can also be adopted. By adopting the above structure, a "ji" - shaped structure can be formed by two adjacent second transmission lines 220, and the microstrip line resonator 300 is arranged in the semi - enclosed area (i.e., the concave area of the "ji" - shaped structure) of the "ji" - shaped structure. By adjusting the length of the vertical section 223, the length of the second transmission line 220 can be conveniently adjusted without affecting the length dimension of the band-stop filter.

[0026] To achieve miniaturization of the band-stop filter and reduce the width of the band-stop filter (i.e., the dimension of the dielectric substrate 100 in the Figure 1The microstrip line resonator 300 (with dimensions along the y-axis) includes a serpentine microstrip line and a capacitor disk. One end of the serpentine microstrip line is connected to the main transmission line 200, and the other end is connected to the capacitor disk. The serpentine microstrip line adopts a serpentine bending structure to form an equivalent inductance, and the capacitor disk forms a loaded capacitance. Together, they constitute an LC resonant circuit. The serpentine microstrip line's serpentine back-and-forth bending structure allows for a longer microstrip line length within a smaller area, thereby reducing its span while maintaining the same electrical length, i.e., reducing the width of the band-stop filter.

[0027] Therefore, the microstrip line resonator 300, employing the aforementioned structure, can achieve miniaturization at lower resonant frequencies. Furthermore, the inductance can be easily adjusted by modifying the length, number of bends, and width of the serpentine microstrip line; a longer serpentine microstrip line results in a larger inductance, as does a higher number of bends and a smaller width. Additionally, an extra capacitor can be introduced via a plate-like capacitor disk, thereby adjusting the resonant frequency and optimizing the resonant characteristics. The capacitance can be adjusted by modifying the area of ​​the capacitor disk; the capacitor disk typically employs a rectangular structure, preferably a square one. By adjusting the inductance of the serpentine microstrip line and the capacitance of the capacitor disk, the resonant frequency and suppression band of the microstrip line resonator 300 can be changed.

[0028] The resonant frequency and number of microstrip line resonators 300 can be determined according to actual requirements. When the suppression requirement is high, the number of microstrip line resonators 300 at the same frequency can be increased. When the filter needs to achieve a wider bandstop, the number of microstrip line resonators 300 at different frequencies can be increased.

[0029] The following example illustrates this; please continue reading. Figure 1 and Figure 2 This embodiment describes a fourth-order band-stop filter using its structure. In this structure, the plurality of microstrip line resonators 300 include a first resonator 310, a second resonator 320, a third resonator 330, and a fourth resonator 340 connected sequentially on the main transmission line 200. The first resonator 310 and the fourth resonator 340 have the same resonant frequency, and the second resonator 320 and the third resonator 330 have the same resonant frequency, thus forming a centrally symmetrical structure. By setting two microstrip line resonators 300 at each resonant frequency, the rectangularity of the band-stop filter can be improved, resulting in a narrower transition band between the passband and stopband, a steeper filter edge, and stronger frequency selectivity. Of course, if a higher rectangularity is required, the number of microstrip line resonators 300 with the same resonant frequencies as the first resonator 310 and the second resonator 320 can be further increased.

[0030] Since the resonant frequencies of the first resonator 310 and the second resonator 320 are different, the suppression frequency band formed by the first resonator 310 and the suppression frequency band formed by the second resonator 320 will only partially overlap, thus allowing them to be combined to form a relatively wide bandstop. Of course, if a wider bandstop is required, more microstrip line resonators 300 with resonant frequencies different from those of the first resonator 310 and the second resonator 320 can be added.

[0031] Please see Figure 3 The back surface 120 has a grounding metal layer 121 to ensure electromagnetic shielding. Below each microstrip resonator 300, a hollow area formed by removing the grounding metal layer 121 is provided. (See also...) Figure 4 Furthermore, grooves can be cut into the hollowed-out area to form recesses, thereby increasing the thickness of the dielectric substrate 100 in that area. By forming hollowed-out or recessed structures, the parasitic capacitance of the microstrip line resonator 300 can be eliminated, resonant frequency delay can be avoided, and the normal passband can be widened.

[0032] In this embodiment, the main transmission line 200 adopts a curved structure, which can significantly reduce the physical span of the main transmission line 200. The microstrip line resonator 300 includes a combination structure of a serpentine microstrip line and a capacitor disk. It can adopt a curved transmission line and a serpentine bending resonator structure, which can significantly reduce the physical span of the resonator while keeping the electrical length of the serpentine microstrip line unchanged. The overall volume of the resulting band-stop filter is significantly reduced compared to the traditional structure, realizing the miniaturization of the structure. Furthermore, the resonant frequency and suppression bandwidth can be easily tuned by adjusting the length, number of bends, linewidth, and area of ​​the capacitor disk of the serpentine microstrip line, adapting to the needs of various application scenarios. In addition, in this embodiment, by forming a hollow area or groove structure on the ground metal layer 121 on the back side 120, the parasitic capacitance of the microstrip line resonator 300 can be eliminated, avoiding resonant frequency shift, thereby widening the passband range, improving passband flatness and transmission efficiency, and has broad application prospects.

[0033] The above embodiments merely illustrate preferred implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention should be determined by the appended claims.

Claims

1. A miniaturized bandstop filter, characterized by: The device includes a dielectric substrate, which has a front side and a back side disposed opposite to each other. The front side is provided with a main transmission line extending from a first end to a second end and a plurality of microstrip line resonators connected to the main transmission line. The main transmission line and the microstrip line resonators are both formed using microstrip lines. The main transmission line is curved. The back side is formed with a ground metal layer.

2. The miniaturized band reject filter of claim 1, wherein: The dielectric substrate is made of a low-loss dielectric material; and / or Both the microstrip line and the ground metal layer are gold-plated.

3. The miniaturized band-stop filter as described in claim 1, characterized in that: The main transmission line forms an input / output port at each end. The main transmission line includes a first transmission line connecting the input / output port to an adjacent microstrip line resonator and a second transmission line connecting two adjacent microstrip line resonators. The length of the second transmission line is adapted to a quarter wavelength of the center frequency of the band-stop filter.

4. The miniaturized band-stop filter as described in claim 3, characterized in that: The first transmission line includes a first horizontal segment connected to the input / output port, a second horizontal segment connected to an adjacent microstrip line resonator, and a first curved segment connecting the first horizontal segment and the second horizontal segment.

5. The miniaturized band-stop filter as described in claim 3, characterized in that: The second transmission line includes a third horizontal segment connected to a microstrip line resonator, a fourth horizontal segment connected to another microstrip line resonator, and a second curved segment connecting the third horizontal segment and the fourth horizontal segment.

6. The miniaturized band-stop filter as described in claim 5, characterized in that: The second curve segment includes a second arc segment connected to the third horizontal segment, a vertical segment connected to the second arc segment, and a third arc segment connecting the vertical segment and the fourth horizontal segment.

7. The miniaturized band-stop filter as described in claim 1, characterized in that: The miniaturized band-stop filter is a fourth-order band-stop filter. The plurality of microstrip line resonators include a first resonator, a second resonator, a third resonator, and a fourth resonator connected in sequence on the main transmission line. The first resonator and the fourth resonator have the same resonant frequency, and the second resonator and the third resonator have the same resonant frequency.

8. The miniaturized band-stop filter as described in claims 1 to 7, characterized in that: The microstrip line resonator includes a serpentine microstrip line and a capacitor disk. One end of the serpentine microstrip line is connected to the main transmission line, and the other end of the main transmission line is connected to the capacitor disk.

9. The miniaturized band-stop filter as described in claim 8, characterized in that: Below each microstrip resonator region, a hollow area formed by removing the grounding metal layer is provided.

10. The miniaturized band-stop filter as described in claim 9, characterized in that: The back surface has a groove formed in each of the hollowed-out areas.

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