A small-size high-bandwidth thin-film microstrip filter

Abstract

The small-size high-bandwidth thin film microstrip filter comprises a long-strip-shaped substrate and a resonator group arranged on the substrate, a line connecting the midpoints of the long sides of the substrate on both sides forms a center line, the resonator group comprises 2n resonators symmetrically distributed along the center line, n is an even number, a first cross-sawtooth structure forming a capacitive coupling is arranged between the nth-m resonator and the nth-m+1 resonator, a second cross-sawtooth structure forming a capacitive coupling is arranged between the nth resonator and the nth+1 resonator, m is an odd number smaller than n, the cross-sawtooth structure can be used to increase the coupling area and improve the coupling amount without changing the size of the thin film microstrip filter, so that the bandwidth requirement is met, the nth-s resonator and the nth-s+1 resonator are connected through a connecting rib, s is an even number smaller than n, and the inductive coupling formed by the connecting rib can also be used to eliminate the parasitic zero point formed on the far end side of the passband, so that the electrical performance is improved.

Description

Technical Field

[0001] This invention relates to the field of communication technology, and more specifically to a small-size, high-bandwidth thin-film microstrip filter. Background Technology

[0002] Microstrip filters are devices used to separate microwave signals of different frequencies. Their main function is to suppress unwanted signals, preventing them from passing through. With the rapid development of the modern microwave communication industry, miniaturized, lightweight, highly reliable, and high-frequency microwave devices are receiving increasing attention. As a result, thin-film processing technology has developed rapidly. Thin-film processing refers to the process of creating ultra-fine line patterns on ceramic substrates using processes such as evaporation, sputtering, patterning lithography, wet and dry etching, and electroplating to perform specific circuit functions.

[0003] Microstrip filters fabricated using thin-film technology are called thin-film microstrip filters. They have advantages such as fine lines, high precision, good heat dissipation, and high reliability, and are increasingly widely used in microwave circuit systems.

[0004] Traditional thin-film microstrip filters are mostly like Figure 1 As shown, multiple line patterns arranged side-by-side and spaced apart are used as resonators to achieve the filtering function. Although the size of this scheme meets the requirements, as... Figure 2 As shown, the bandwidth of this scheme (300MHz) is less than half of the required specification, far from meeting the usage requirements. The main reason for this phenomenon is that, under the premise of limited length and width, the length and spacing of the line graphic are limited, resulting in insufficient coupling of each resonator, which makes the total bandwidth of the thin film microstrip filter low. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a small-size, high-bandwidth thin-film microstrip filter.

[0006] To achieve the above objectives, the present invention provides a small-size, high-bandwidth thin-film microstrip filter, comprising a long strip-shaped substrate and a resonator group disposed on the substrate, wherein the line connecting the midpoints of the two long sides of the substrate forms a center line, and the resonator group comprises 2n resonators symmetrically distributed along the center line, wherein n is an even number, characterized in that:

[0007] A first cross-saw structure for forming capacitive coupling is provided between the nm-th resonator and the (n-m+1)-th resonator, and a second cross-saw structure for forming capacitive coupling is provided between the n-th resonator and the (n+1)-th resonator, where m is an odd number less than n;

[0008] The ns-th resonator is connected to the (n-s+1)-th resonator by a connecting rib to form inductive coupling, where s is an even number less than n.

[0009] Preferably, the intersection depth of the first cross-serration structure and the second cross-serration structure is positively correlated with the coupling amount of the resonator.

[0010] More preferably, the cross depth of the second cross serrated structure is greater than or equal to the cross depth of the first cross serrated structure.

[0011] Preferably, the number of cross teeth in the first cross-saw structure and the second cross-saw structure is positively correlated with the coupling amount of the resonator.

[0012] Preferably, both the ns-th resonator and the (n-s+1)-th resonator are provided with grounding vias, and the grounding vias on these two resonators are close to the same long side of the substrate.

[0013] More preferably, the connecting rib is positioned close to the grounding through hole.

[0014] Preferably, the length of the substrate is less than or equal to 16 mm, and the width of the substrate is less than or equal to 7 mm.

[0015] More preferably, the substrate is an alumina ceramic substrate with a dielectric constant of 14.5, and the thickness of the substrate is 0.50-0.52 mm.

[0016] More preferably, n equals 4.

[0017] More preferably, the small-size high-bandwidth thin-film microstrip filter further includes an input port, which is connected to the outermost resonator of the resonator group via an impedance line with an impedance of 50 ohms.

[0018] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0019] The present invention provides a small-size, high-bandwidth thin-film microstrip filter, comprising an elongated substrate and a resonator group disposed on the substrate. The line connecting the midpoints of the long sides of the two sides of the substrate forms a center line. The resonator group includes 2n resonators symmetrically distributed along the center line, where n is an even number. By providing a first cross-saw structure for capacitive coupling between the nm-th resonator and the (n-m+1)-th resonator, and a second cross-saw structure for capacitive coupling between the n-th resonator and the (n+1)-th resonator, where m is an odd number less than n, the coupling area can be increased using the cross-saw structure without changing the size of the thin-film microstrip filter, thereby improving the coupling amount and meeting the bandwidth requirements. By connecting the ns-th resonator and the (n-s+1)-th resonator through a connecting rib for inductive coupling, where s is an even number less than n, the parasitic zeros formed on the far end of the passband can be eliminated using inductive coupling without affecting the bandwidth, thus improving the electrical performance of the small-size, high-bandwidth thin-film microstrip filter. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of a traditional thin-film microstrip filter.

[0021] Figure 2 yes Figure 1 The electrical performance diagram is shown, where the dashed lines represent the required parameters and the solid lines represent the actual simulation parameters.

[0022] Figure 3 This is a schematic diagram of a preferred embodiment of the present invention.

[0023] Figure 4 yes Figure 3 Electrical performance diagram.

[0024] Figure 5 yes Figure 3 A schematic diagram of a structure without inductive coupling.

[0025] Figure 6 yes Figure 5 Electrical performance diagram.

[0026] Wherein: 10. Substrate; 11. Center line; 20. Resonator group; 21. First cross-saw structure; 22. Second cross-saw structure; 23. Grounding via; 24. Connecting rib; 30. Impedance line; 40. Input port. Detailed Implementation

[0027] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings.

[0028] like Figure 3As shown, the small-size, high-bandwidth thin-film microstrip filter provided by the present invention includes an elongated substrate 10 and a resonator group 20 disposed on the substrate 10. The line connecting the midpoints of the long sides on both sides of the substrate 10 forms a center line 11. The resonator group 20 includes eight resonators (resonators 1 to 8) symmetrically distributed along the center line. A first cross-saw structure 21 for forming capacitive coupling is provided between the first resonator (resonator 1) and the second resonator (resonator 2), between the third resonator (resonator 3) and the fourth resonator (resonator 4), between the fifth resonator (resonator 5) and the sixth resonator (resonator 6), and between the seventh resonator (resonator 7) and the eighth resonator (resonator 8). A second cross-saw structure 22 for forming capacitive coupling is provided between the fourth resonator (resonator 4) and the fifth resonator (resonator 5). The advantage of this arrangement is that, without changing the size of the thin-film microstrip filter, the coupling area can be increased by utilizing the cross-saw structure, thereby increasing the coupling amount and meeting the bandwidth requirements. Specifically, as shown... Figure 4 As shown, this small-size, high-bandwidth thin-film microstrip filter has a bandwidth of 660MHz, which meets the application requirements. Furthermore, the second resonator (resonator 2) is connected to the third resonator (resonator 3), and the sixth resonator (resonator 6) is connected to the seventh resonator (resonator 7) via connecting ribs to form inductive coupling. Figure 5 and Figure 6 It can be seen that this configuration can eliminate the parasitic zeros formed at the far end of the passband (at 3.74 GHz) by using inductive coupling without affecting the bandwidth, thereby improving the electrical performance of this small-sized, high-bandwidth thin-film microstrip filter.

[0029] In this embodiment, the cross depth of the first cross sawtooth structure 21 and the second cross sawtooth structure 22 is positively correlated with the coupling amount of the resonator. To facilitate adjustment, the cross depth of the second cross sawtooth structure 22 is greater than the cross depth of the first cross sawtooth structure 21.

[0030] Furthermore, the number of cross teeth in the first cross-saw structure 21 and the second cross-saw structure 22 is positively correlated with the coupling amount of the resonator.

[0031] In this embodiment, both the second resonator (resonator 2) and the third resonator (resonator 3) are provided with grounding through holes 23. The grounding through holes 23 on these two resonators are close to the same long side of the substrate 10, and the connecting ribs 24 are disposed close to the grounding through holes 23.

[0032] In this embodiment, the small-size high-bandwidth thin-film microstrip filter also includes an input port 40, which is connected to the outermost resonators (resonator 1 and resonator 8) of the resonator group via an impedance line 30 with an impedance of 50 ohms.

[0033] In this embodiment, the substrate 10 has a length of 16 mm and a width of 6.5 mm. The substrate 10 is an alumina ceramic substrate with a dielectric constant of 14.5 and a thickness of 0.508 mm. The center frequency F0 of this small-size high-bandwidth thin-film microstrip filter is 2.45 GHz, the bandwidth is 0.66 GHz, and the suppression F0 ± 0.55 GHz ≥ 25 dB is ≥ 25 dB.

[0034] The above are merely specific embodiments of this application. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principles of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A small-size high-bandwidth thin-film microstrip filter, comprising a long strip-shaped substrate and a resonator group arranged on the substrate, a line connecting the midpoints of the long sides of the substrate on both sides constituting a center line, the resonator group comprising 2n resonators symmetrically distributed along the center line, wherein, n is an even number, characterized in that: The length of the substrate is less than or equal to 16 mm, the width is less than or equal to 7 mm, and the thickness is 0.50-0.52 mm; A first cross-sawtooth structure for forming capacitive coupling is arranged between the nth-m resonator and the nth-m+1 resonator, and a second cross-sawtooth structure for forming capacitive coupling is arranged between the nth resonator and the nth+1 resonator, wherein m is an odd number less than n; Grounding vias are arranged on the nth-s resonator and the nth-s+1 resonator, the grounding vias on the two resonators are close to the same side of the long side of the substrate, the nth-s resonator and the nth-s+1 resonator are connected through a connecting rib arranged close to the grounding vias to form inductive coupling, wherein s is an even number less than n; So that the bandwidth of the small-size high-bandwidth thin-film microstrip filter is 660Mhz, and the parasitic zero points formed on the far end of the passband are eliminated.

2. The small size high bandwidth thin film microstrip filter according to claim 1, characterized in that: The cross depth of the first cross-sawtooth structure and the second cross-sawtooth is positively related to the coupling amount of the resonator.

3. The small size high bandwidth thin film microstrip filter according to claim 2, wherein: The cross depth of the second cross-sawtooth structure is greater than or equal to the cross depth of the first cross-sawtooth structure.

4. The small size high bandwidth thin film microstrip filter according to claim 1, wherein: The cross tooth number of the first cross-sawtooth structure and the second cross-sawtooth is positively related to the coupling amount of the resonator.

5. The small size high bandwidth thin film microstrip filter according to claim 1, wherein: The substrate is an alumina ceramic substrate with a dielectric constant of 14.

5.

6. The small size high bandwidth thin film microstrip filter according to claim 1, wherein: The n is equal to 4.

7. The small size high bandwidth thin film microstrip filter according to any one of claims 1 to 6, characterized in that: The small-size high-bandwidth thin-film microstrip filter further comprises an input port, and the input port is connected to the outermost resonator of the resonator group through an impedance line with an impedance of 50 ohms.

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