Small-size high-suppression film band-pass filter

Abstract

The utility model provides a small-size high-suppression film band-pass filter which comprises a substrate. A metal transmission line and a plurality of resonators are arranged on the substrate; the resonator is connected with the metal transmission line; the resonator is composed of a bent microstrip line and a straight microstrip line with different impedances; one end of the resonator is open-circuited, and the other end is connected to the metal short-circuit layer on the back of the substrate through a metal via hole. According to the utility model, through different microstrip line impedances and different bending lengths, the near-end suppression and the far-end suppression of the filter are improved.

Description

Technical Field

[0001] This utility model relates to the field of thin-film bandpass filter technology, specifically to a small-volume, high-suppression thin-film bandpass filter. Background Technology

[0002] With the rapid development of 5G communication, satellite navigation and Internet of Things technologies, microwave filters, as core components of the radio frequency front end, are increasingly in demand for miniaturization and high suppression performance. Traditional bandpass filters are mainly implemented using cavity structures, dielectric resonators or LTCC technology, but they generally have the following defects in high-frequency applications: (1) Cavity filters are difficult to compress due to their three-dimensional mechanical structure; (2) Cavity filters require high processing precision, resulting in high production costs; (3) Although thin-film filters have advantages in size, their suppression performance is insufficient. Utility Model Content

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a small-volume, high-suppression thin-film bandpass filter. By using different microstrip line impedances and different bending lengths, the near-end and far-end suppression of the filter are improved. This is achieved through the following technical solutions:

[0004] A small-volume, high-suppression thin-film bandpass filter includes a substrate; a metal transmission line and multiple resonators are disposed on the substrate; the resonators are connected to the metal transmission line; the resonators are composed of bent microstrip lines and straight microstrip lines with different impedances; one end of the resonator is open-circuited, and the other end is connected to a metal short-circuit layer on the back side of the substrate through a metal via.

[0005] Optionally or preferably, the substrate is a silicon-containing substrate or an alumina substrate.

[0006] Optionally or preferably, the number of resonators is three, and the three resonators are arranged in a linear array on the front side of the substrate, with a spacing of 0.1-0.3 mm between adjacent resonators.

[0007] Optionally or preferably, the bent microstrip line includes alternating narrow and wide segments, wherein the characteristic impedance of the narrow segment is 65-85Ω and the characteristic impedance of the wide segment is 25-35Ω.

[0008] Optionally or preferably, the metal via adopts a blind via structure, wherein the depth of the blind via is 70-90% of the substrate thickness and the diameter is 80-120μm.

[0009] Optionally or preferably, the thickness of the substrate is 0.25-0.4 mm, the thickness of the metal short-circuit layer is 8-12 μm, and the metal short-circuit layer covers more than 90% of the back surface area of ​​the substrate.

[0010] Optionally or preferably, the surface of the substrate is further provided with a dielectric protective layer, the thickness of which is 15-25 μm and the dielectric constant is 3.5-4.2.

[0011] Optionally or preferably, the coupling distance between the metal transmission line and the nearest resonator is 0.08-0.15 mm, and the end of the metal transmission line is provided with a matching section with an impedance of 50 Ω.

[0012] Based on the above technical solution, the present invention provides a small-volume, high-suppression thin-film bandpass filter, which can produce the following technical effects:

[0013] (1) The three-dimensional structure is compact and can integrate multiple resonators in a small area, reducing the volume by more than 85% compared with traditional cavity filters;

[0014] (2) The bent microstrip line and the straight microstrip line work together to improve the second harmonic suppression by more than 40%;

[0015] (3) Metal vias combined with a large area of ​​metal short-circuit layer on the back side will reduce grounding inductance and voltage standing wave ratio;

[0016] (4) The resonators arranged in a linear array form directional electromagnetic coupling, which improves the flatness compared to existing planar filters. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of this utility model;

[0019] Figure caption:

[0020] 1-Metal transmission line, 2-Metal via, 3-First resonator, 4-Second resonator, 5-Third resonator. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0022] In a preferred embodiment:

[0023] like Figure 1 As shown:

[0024] This embodiment provides a small-volume, high-suppression thin-film bandpass filter, including a substrate; a metal transmission line 1 and multiple resonators are provided on the substrate; the resonators are connected to the metal transmission line 1; the resonators are composed of bent microstrip lines and straight microstrip lines with different impedances; one end of the resonator is open-circuited, and the other end is connected to the metal short-circuit layer on the back of the substrate through a metal via 2.

[0025] Furthermore, in this embodiment, the substrate is selected as a silicon-containing substrate or an alumina substrate.

[0026] Furthermore, in this embodiment, the number of resonators is three, and the three resonators are arranged in a linear array on the front side of the substrate, such as... Figure 1 As shown, the first resonator 3, the second resonator 4, and the third resonator 5 are respectively, and the spacing between adjacent resonators is 0.1-0.3mm.

[0027] Furthermore, in this embodiment, the bent microstrip line includes alternating narrow and wide segments, wherein the characteristic impedance of the narrow segment is 65-85Ω and the characteristic impedance of the wide segment is 25-35Ω.

[0028] Furthermore, in this embodiment, the metal via 2 adopts a blind via structure, the depth of which is 70-90% of the substrate thickness and the diameter is 80-120μm.

[0029] Furthermore, in this embodiment, the thickness of the substrate is 0.25-0.4 mm, the thickness of the metal short-circuit layer is 8-12 μm, and the metal short-circuit layer covers more than 90% of the back surface area of ​​the substrate.

[0030] Furthermore, the surface of the substrate is provided with a dielectric protective layer, the thickness of which is 15-25 μm and the dielectric constant is 3.5-4.2.

[0031] Furthermore, the coupling distance between the metal transmission line and the nearest resonator is 0.08-0.15mm, and the end of the metal transmission line is provided with a matching section with an impedance of 50Ω.

[0032] The working principle provided in this embodiment is as follows:

[0033] Radio frequency signals are input through metal transmission line 1, and energy is transferred to the first resonator 3 through coupling gap; the bent microstrip line generates fundamental mode resonance, and the straight microstrip line synchronously excites higher-order modes; adjacent resonators enhance energy transmission in the passband through electromagnetic coupling modulated by the gap, while suppressing out-of-band spurious waves; metal via 2 introduces harmonic energy into the metal short-circuit layer on the back side, and reduces the Q value through distributed absorption to avoid the generation of secondary resonance peaks.

[0034] The above description is merely a preferred embodiment of this utility model. It should be understood that this utility model is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of this utility model should be protected within the scope of the appended claims.

Claims

1. A small volume high rejection thin film bandpass filter characterized by: The application relates to a substrate, wherein a metal transmission line and a plurality of resonators are arranged on the substrate; the resonators are connected with the metal transmission line; the resonators are composed of bent microstrip lines and straight microstrip lines with different impedances; one end of the resonators is open, and the other end is connected to a metal short circuit layer on the back of the substrate through a metal via.

2. The small size high rejection thin film bandpass filter according to claim 1, characterized in that: The substrate is selected from a silicon substrate or an alumina substrate.

3. The small size high rejection thin film bandpass filter according to claim 1, wherein: The number of the resonators is three, and the three resonators are arranged in a linear array on the front of the substrate, and the spacing between adjacent resonators is 0.1-0.3 mm.

4. The small size high rejection thin film bandpass filter according to claim 1, wherein: The bent microstrip line comprises alternately arranged narrow-band sections and wide-band sections, wherein the characteristic impedance of the narrow-band sections is 65-85 omega, and the characteristic impedance of the wide-band sections is 25-35 omega.

5. The small size high rejection thin film bandpass filter according to claim 1, wherein: The metal via adopts a blind hole structure, the hole depth of the blind hole is 70-90% of the thickness of the substrate, and the hole diameter is 80-120 mu m.

6. The small size high rejection thin film bandpass filter according to claim 1, wherein: The thickness of the substrate is 0.25-0.4 mm, the thickness of the metal short circuit layer is 8-12 mu m, and the metal short circuit layer covers more than 90% of the area of the back of the substrate.

7. The small size high rejection thin film bandpass filter according to claim 1, wherein: The surface of the substrate is further provided with a dielectric protective layer, the thickness of the dielectric protective layer is 15-25 mu m, and the dielectric constant is 3.5-4.

2.

8. The small size high rejection thin film bandpass filter according to claim 1, wherein: The coupling spacing between the metal transmission line and the nearest resonator is 0.08-0.15 mm, and the end of the metal transmission line is provided with a matching section with an impedance of 50 omega.

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