LTCC-based high-performance dual-band band-pass filter

Abstract

The invention discloses a high-performance dual-band band-pass filter based on a dual-mode resonator structure. The high-performance dual-band band-pass filter comprises an input feeder line, two short-circuit stub loading hairpin ring resonators and an output feeder line. Wherein the two short-circuit stub loaded hairpin ring resonators are the same in topological structure, size and working frequency. The input feeder line is in slot coupling with the first short-circuit stub-loaded hairpin ring resonator to provide electromagnetic excitation, and the output feeder line is in slot coupling with the second short-circuit stub-loaded hairpin ring resonator to provide electromagnetic excitation. Based on the structure of the short-circuit stub loaded hairpin ring resonator, the invention provides a miniaturized dual-band band-pass filter which has multiple transmission zeros with independent and controllable center frequency and is compact in structure. The size problem caused by the fact that a common circuit needs a multi-layer circuit to achieve a large center frequency ratio and needs an additional structure to achieve multiple transmission zeros is solved.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technology, and more particularly to a high-performance dual-band bandpass filter based on LTCC. Background Art

[0002] With the rapid development of wireless communication technology, spectrum resources are becoming increasingly crowded, and the demand for high-performance dual-band bandpass filters with a large center frequency ratio is increasing. The current technology used to achieve a large center frequency ratio is mainly through cascading, such as using a microstrip structure to achieve a low-frequency passband, and a SIW or cavity structure to achieve a high-frequency passband, and then cascading these two structures. In addition, the suppression between the two passbands also requires additional structures to achieve high suppression, which undoubtedly greatly increases the circuit size. Therefore, how to achieve miniaturization while ensuring high suppression characteristics between the two passbands deserves further study.

[0003] Microstrip lines are widely used in filter design due to their advantages such as simple processing and low cost. However, at present, there are still certain design challenges for high-performance dual-band bandpass filters with a large center frequency ratio based on microstrip structure design. (1) There are many spurious frequencies in the uniform microstrip line structure, and these frequencies are close to each other, which makes it difficult to meet the requirements of having a large center frequency ratio and achieving high suppression characteristics between the two passbands. Although the cascaded low-pass structure can suppress the spurious frequencies between the two passbands, it will greatly increase the circuit size. Subsequent research will use the method of moving the feed line position to suppress unnecessary high-order harmonics to achieve high suppression characteristics. (2) The out-of-band suppression of the upper stopband of the second passband is low and the suppression range is narrow. Subsequent research will use the method of generating zero points to suppress the high-order harmonics in the upper stopband to achieve high suppression characteristics over a wide range. Summary of the invention

[0004] The technical problem to be solved by the present invention is that, in view of the shortcomings and deficiencies existing in the prior art, a design scheme and circuit structure of a dual-band bandpass filter with controllable center frequency based on a short-circuited branch-loaded hairpin ring resonator is provided. The dual-band bandpass filter of the present invention has the advantages of simple structure and easy processing.

[0005] The present invention adopts the following technical scheme: a high-performance dual-band bandpass filter, comprising an input feeder and a first short-circuit branch-loaded hairpin ring resonator slot-coupled with the input feeder, an output feeder and a second short-circuit branch-loaded hairpin ring resonator slot-coupled with the output feeder; The first short-circuit branch loaded hairpin ring resonator includes a first short-circuit branch structure and a first hairpin ring structure; the second short-circuit branch loaded hairpin ring resonator includes a second short-circuit branch structure and a second hairpin ring structure, and the first direction is perpendicular to the second direction.

[0006] Furthermore, the first short-circuit branch structure is located in the first hairpin ring structure and is bent multiple times, so that the corresponding part of the first short-circuit branch structure is parallel to the corresponding part of the first hairpin ring structure with a preset gap; the second short-circuit branch structure is located in the second hairpin ring structure and is bent multiple times, so that the corresponding part of the second short-circuit branch structure is parallel to the corresponding part of the second hairpin ring structure with a preset gap.

[0007] Further, each of the input feeder and the output feeder includes a feeding portion and a coupling portion; One end of the feeding part is connected to the coupling part and has different distances from two ends of the coupling part. The other end of the feeding part serves as an input / output port. The coupling part is used to achieve gap coupling with the two short-circuit branch-loaded hairpin ring resonators.

[0008] Further, the coupling portion includes a first coupling line and a second coupling line connected to each other; The first coupling line and the second coupling line are both used to realize slot coupling, the first coupling line is perpendicular to the feeding portion, the second coupling line is perpendicular to the first coupling line, and the second coupling line is bent multiple times to realize electromagnetic coupling.

[0009] Furthermore, a metal layer and a dielectric substrate layer are provided, wherein the metal layer includes an upper metal layer and a lower metal layer; The upper metal layer includes two resonator units and two feed lines and resonators.

[0010] Furthermore, the lower metal layer is a metal floor structure, and the metal floor is provided with two metal through holes penetrating the upper metal layer and the dielectric substrate layer.

[0011] Furthermore, the first short-circuit branch loaded hairpin ring resonator and the second short-circuit branch loaded hairpin ring resonator are symmetrically arranged microstrip lines.

[0012] Furthermore, the equivalent impedances of the first short-circuit branch structure, the first hairpin ring structure, the second short-circuit branch structure and the second hairpin ring structure are the same.

[0013] Furthermore, the upper metal layer uses 0.018 mm copper as the metal, and the dielectric substrate layer uses Rogers5880, with a dielectric constant of 2.2, a thickness of 0.508 mm, and a loss tangent of 0.0009.

[0014] Beneficial effects of the invention: The high-performance dual-band bandpass filter proposed by the invention has a compact layout and can generate multiple transmission zeros, which helps to achieve higher passband selectivity and out-of-band suppression effect, and solves the size problem caused by the need for cascading to achieve a large center frequency ratio in general circuits. In addition, the two center frequencies of the dual-band bandpass filter can be controlled independently, which helps to achieve a dual-band bandpass filter with a controllable center frequency ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the embodiments of the present invention or the drawings of related technical solutions in the prior art are introduced below. It should be understood that the drawings introduced below are only for the convenience of clearly describing some embodiments of the technical solutions of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0016] Figure 1 It is a structural schematic diagram of a high-performance dual-band bandpass filter provided in an embodiment of the present application.

[0017] Figure 2 It is a schematic diagram of the resonator structure of a high-performance dual-band bandpass filter provided in an embodiment of the present application.

[0018] Figure 3 It is a schematic diagram of a scattering parameter curve of a single resonator of a high-performance dual-band bandpass filter under weak coupling conditions provided in an embodiment of the present application.

[0019] Figure 4 It is a schematic diagram of a scattering parameter curve of a high-performance dual-band bandpass filter provided in an embodiment of the present application.

[0020] Figure 5 It is a schematic diagram of a partially enlarged scattering parameter curve of a high-performance dual-band bandpass filter provided in an embodiment of the present application.

[0021] Wherein p1 is the feeding part, p2 is the first coupling line, p3 is the second coupling line, and s2 is the coupling distance between the resonators; 110 is an input feeder, 120 is an output feeder, 130 is a first short-circuit branch loaded with a hairpin ring resonator, 132 is a first short-circuit branch structure, 134 is a first short-circuit branch loaded with a hairpin ring resonator, 131, 133, 135 are microstrip lines, and 140 is a second short-circuit branch loaded with a hairpin ring resonator. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention, but the implementation of the present invention is not limited thereto. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0023] A high-performance dual-band bandpass filter, comprising a 50Ω input feeder and a first short-circuit branch-loaded hairpin ring resonator slot-coupled with the input feeder, and a 50Ω output feeder and a second short-circuit branch-loaded hairpin ring resonator slot-coupled with the output feeder; The input feeder is symmetrically arranged with the output feeder, and the input feeder is slot-coupled with the first short-circuit branch-loaded hairpin ring resonator to provide electromagnetic excitation, and the output feeder is slot-coupled with the second short-circuit branch-loaded hairpin ring resonator to provide electromagnetic excitation. The first short-circuit branch-loaded hairpin ring resonator and the second short-circuit branch-loaded hairpin ring resonator are slot-coupled to generate a passband under electromagnetic excitation.

[0024] The first short-circuit branch loaded hairpin ring resonator includes a first short-circuit branch structure and a first hairpin ring structure; the second short-circuit branch loaded hairpin ring resonator includes a second short-circuit branch structure and a second hairpin ring structure, and the first direction is perpendicular to the second direction.

[0025] Furthermore, the first short-circuit branch structure is located in the first hairpin ring structure and is bent multiple times, so that the corresponding part of the first short-circuit branch structure is parallel to the corresponding part of the first hairpin ring structure with a preset gap; the second short-circuit branch structure is located in the second hairpin ring structure and is bent multiple times, so that the corresponding part of the second short-circuit branch structure is parallel to the corresponding part of the second hairpin ring structure with a preset gap.

[0026] Further, each of the input feeder and the output feeder includes a feeding portion and a coupling portion; One end of the feeding part is connected to the coupling part and has different distances from two ends of the coupling part. The other end of the feeding part serves as an input / output port. The coupling part is used to achieve gap coupling with the two short-circuit branch-loaded hairpin ring resonators.

[0027] Further, the coupling portion includes a first coupling line and a second coupling line connected to each other; The first coupling line and the second coupling line are both used to realize slot coupling, the first coupling line is perpendicular to the feeding portion, the second coupling line is perpendicular to the first coupling line, and the second coupling line is bent multiple times to realize electromagnetic coupling.

[0028] Furthermore, a metal layer and a dielectric substrate layer are provided, wherein the metal layer includes an upper metal layer and a lower metal layer; The upper metal layer includes two resonator units and two feed lines and resonators.

[0029] Furthermore, the lower metal layer is a metal floor structure, and the metal floor is provided with two metal through holes penetrating the upper metal layer and the dielectric substrate layer.

[0030] Furthermore, the first short-circuit branch loaded hairpin ring resonator and the second short-circuit branch loaded hairpin ring resonator are symmetrically arranged microstrip lines.

[0031] Furthermore, the equivalent impedances of the first short-circuit branch structure, the first hairpin ring structure, the second short-circuit branch structure and the second hairpin ring structure are the same.

[0032] Furthermore, the upper metal layer uses 0.018 mm copper as the metal, and the dielectric substrate layer uses Rogers5880, with a dielectric constant of 2.2, a thickness of 0.508 mm, and a loss tangent of 0.0009.

[0033] Further explanation is as follows: Figure 1 As shown, the present invention provides a high-performance dual-band bandpass filter, including two layers of metal and a layer of dielectric substrate, wherein the resonator part and the feeder structure are located on the upper metal layer, and the lower metal layer is a metal floor with two metal through holes penetrating the upper metal layer and the intermediate dielectric substrate, and the through hole diameter is 0.25mm. The upper metal layer adopts a copper thickness of 0.018mm, the dielectric constant of the dielectric material is 2.2, the thickness is 0.508mm, and the loss tangent is 0.0009. The plane size of the core circuit is 5.7mm×6.25mm.

[0034] like Figure 2 As shown, the short-circuit branch loaded hairpin ring resonator of the present invention is composed of a short-circuit branch structure and a hairpin ring structure. Figure 3 As shown, under the condition of weak coupling excitation, the resonator has multiple resonant frequencies. Here we only study two resonant frequencies of the resonator. f 1 and f 3. When the length of microstrip lines L1, L2, and L3 is changed, the resonant frequency f 1 and resonant frequency f 3 have an impact, among which the resonant frequency f1 The branch with the greatest impact is the short-circuit branch structure, that is, the length of L3, which has a great impact on the resonant frequency. f 3 The most influential branch is the open branch of the hairpin ring structure, that is, the length of L1, so the center frequency of the two passbands can be flexibly controlled by reasonably adjusting the length of L1 and L3. The final optimized circuit size is: L1 = 6.9mm, L2 = 10.5mm, L3 = 11.9mm, the microstrip line width of the resonator part adopts 0.2mm line width, the microstrip line of the feeder part coupled with the resonator adopts 0.15mm line width, and the 50Ω feeder width at the port adopts 1.55mm.

[0035] like Figure 4 As shown, a schematic diagram of a scattering parameter curve of a high-performance dual-band bandpass filter provided by an embodiment of the present invention. The two center frequencies of the dual-band bandpass filter of the present invention are respectively located at 2.4GHz and 12.4GHz, the maximum insertion losses in the two passbands are respectively 0.3dB and 0.8dB, the lower stopband suppression is lower than -60dB, the suppression between the two passbands is lower than -23.8dB, the upper stopband suppression of the second passband is lower than -19.5dB, and the suppression frequency range covers 12.9GHz-18GHz. Not only the high suppression characteristics between the two passbands are achieved, but also the wider suppression range of the upper stopband of the second passband is achieved, which effectively improves the transmission efficiency of the signal.

[0036] Figure 5 (a) is a schematic diagram of a first passband amplified scattering parameter curve of a high performance dual passband filter provided by an embodiment of the present invention, Figure 5 (b) is a schematic diagram of a second passband amplified scattering parameter curve of a high performance dual-band bandpass filter provided by an embodiment of the present invention.

[0037] In addition, since the resonator structure adopts a hairpin ring structure, it effectively increases the signal transmission path, so that it can generate multiple transmission zero points and improve the suppression degree. By properly adjusting the position of the feed line, the resonant frequency can be suppressed. f 2 The passband of the excitation greatly improves the stopband suppression characteristics between the two passbands.

[0038] The above description is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a technician familiar with the technical field within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

Claims

1. A high performance dual-band bandpass filter, characterized in that: It includes an input feeder and a first short-circuit branch-loaded hairpin ring resonator slot-coupled with the input feeder, and an output feeder and a second short-circuit branch-loaded hairpin ring resonator slot-coupled with the output feeder; The first short-circuit branch loaded hairpin ring resonator includes a first short-circuit branch structure and a first hairpin ring structure; the second short-circuit branch loaded hairpin ring resonator includes a second short-circuit branch structure and a second hairpin ring structure, and the first direction is perpendicular to the second direction.

2. A high performance dual-band bandpass filter according to claim 1, characterized in that: The first short-circuit branch structure is located in the first hairpin ring structure and is bent multiple times, so that a corresponding portion of the first short-circuit branch structure is parallel to a corresponding portion of the first hairpin ring structure with a preset gap; The second short-circuit branch structure is located in the second hairpin ring structure and is bent multiple times, so that a corresponding portion of the second short-circuit branch structure is parallel to a corresponding portion of the second hairpin ring structure with a preset gap therebetween.

3. A high performance dual-band bandpass filter according to claim 1, characterized in that: Each of the input feeder and the output feeder includes a feeding portion and a coupling portion; One end of the feeding part is connected to the coupling part and has different distances from two ends of the coupling part. The other end of the feeding part serves as an input / output port. The coupling part is used to achieve gap coupling with the two short-circuit branch-loaded hairpin ring resonators.

4. A high performance dual-band bandpass filter according to claim 3, characterized in that: The coupling portion includes a first coupling line and a second coupling line connected to each other; The first coupling line and the second coupling line are both used to realize slot coupling, the first coupling line is perpendicular to the feeding portion, the second coupling line is perpendicular to the first coupling line, and the second coupling line is bent multiple times to realize electromagnetic coupling.

5. A high performance dual-band bandpass filter according to claim 1, characterized in that: Providing a metal layer and a dielectric substrate layer, wherein the metal layer comprises an upper metal layer and a lower metal layer; The upper metal layer includes two resonator units and two feed lines and resonators.

6. A high performance dual-band bandpass filter according to claim 5, characterized in that: The lower metal layer is a metal floor structure, and the metal floor is provided with two metal through holes penetrating the upper metal layer and the dielectric substrate layer.

7. A high performance dual-band bandpass filter according to claim 1, characterized in that: The first short-circuit branch loaded hairpin ring resonator and the second short-circuit branch loaded hairpin ring resonator are symmetrically arranged microstrip lines.

8. A high performance dual-band bandpass filter according to claim 2, characterized in that: The equivalent impedances of the first short-circuit branch structure, the first hairpin ring structure, the second short-circuit branch structure and the second hairpin ring structure are the same.

9. A high performance dual-band bandpass filter according to claim 5, characterized in that: The upper metal layer uses 0.018mm copper as the metal, and the dielectric substrate layer uses Rogers5880, with a dielectric constant of 2.2, a thickness of 0.508mm, and a loss tangent of 0.0009.

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