A closed miniaturized wide stopband bandpass filter based on a single cavity and four modes

Abstract

This invention discloses a closed, miniaturized, wide-stopband bandpass filter based on a single cavity and four modes, belonging to the field of microwave technology. The filter comprises an upper metal plate, an upper microwave dielectric plate, an intermediate circuit metal layer, a lower microwave dielectric plate, and a lower metal plate. The intermediate circuit metal layer includes a pair of input / output feed lines, two rows of mutually perpendicular metallized through-holes, a triangular resonator, two loaded slot lines, and a first metallized through-hole in the triangular resonator. Compared with existing technologies, the present invention is smaller in size and has a wider stopband, making it well-suited for use in future millimeter-wave communication systems.

Description

Technical Field

[0001] The present invention belongs to the field of microwave technology, and in particular relates to a closed miniaturized wide-stopband bandpass filter based on a single-cavity four-mode, which can be used in a millimeter-wave transceiver system. Background Art

[0002] Bandpass filters are essential components in modern wireless communication systems. They are primarily used in RF communication systems to select useful signals while suppressing spurious signals and harmonics. Furthermore, as a crucial component for distinguishing between different spectrums, they are crucial for improving spectrum resource utilization.

[0003] The miniaturization, low insertion loss, and wide stopband characteristics of bandpass filters have driven their application. The increasing frequency of communication systems is driving increasingly dense device integration. Device miniaturization is an absolute trend in the future development of devices and RF communication systems, including bandpass filter miniaturization. Furthermore, with the development of 5G communications, high carrier frequencies, high transmission rates, and complex modulation formats have made power loss a significant issue. Therefore, low insertion loss devices are crucial. Furthermore, high-performance, wide-stopband bandpass filters play a key role in preventing out-of-band spurious interference from disrupting signals within the desired frequency band. Based on the above three points, substrate-integrated waveguide (SIW) structures offer a higher quality factor than other transmission structures, such as microstrip, slotline, and stripline structures, resulting in lower insertion loss in the millimeter-wave frequency band. Furthermore, slotline-loaded SIWs offer the advantage of miniaturization compared to SIWs. More importantly, they can achieve multimode resonance to increase operating bandwidth and improve out-of-band rejection. Therefore, multimode-resonant SIW bandpass filters are particularly well-suited for the upcoming fifth-generation mobile communication technology.

[0004] Currently, multi-mode resonant SIW bandpass filters commonly suffer from two issues. First, in most cases, the center frequency of these filters lies in a higher-order resonant mode, which directly increases their size. Second, when all the multi-mode resonant modes utilize substrate-integrated waveguides, their out-of-band suppression is poor. Therefore, the miniaturization, wide stopband, and multi-mode resonance characteristics of SIW bandpass filters will be design difficulties and challenges for future millimeter-wave communications.

[0005] Invention CN201910681141.7 Miniaturized wide stopband HMSIW single cavity three-mode bandpass filter. This bandpass filter uses TE 101 TE 201A single-cavity, three-mode bandpass filter was designed using resonant modes and slot resonance. Its upper stopband features a transmission zero, increasing passband selectivity. However, the filter's cavity is open, increasing losses, and its low-frequency performance needs improvement. Addressing the shortcomings of these filters, we aim to improve them and design similar products with superior performance. Summary of the Invention

[0006] Purpose of the invention: In view of the above-mentioned problems existing in the prior art, the purpose of the present invention is to propose a closed miniaturized wide-stopband bandpass filter with a single cavity and four modes which is simple in structure and easy to implement, and which has the characteristics of small size and high performance out-of-band suppression.

[0007] Technical solution: The purpose of the present invention will be achieved through the following technical solutions:

[0008] A closed, miniaturized, wide-stopband bandpass filter based on a single cavity and four modes, comprising an upper metal plate, an intermediate microwave dielectric plate, an intermediate circuit metal layer, an intermediate microwave dielectric plate, and a lower metal plate; the upper and lower metal plates and metallized through-holes form a closed resonant cavity; the intermediate circuit metal layer comprises a pair of input / output feed lines, a triangular resonant plate, a first loaded slot line, a second loaded slot line, and a first metallized through-hole above the first loaded slot line;

[0009] The intermediate circuit metal layer is an isosceles right triangle;

[0010] The two rows of metallized through holes are respectively parallel to the right-angled sides of the triangle and perpendicular to each other;

[0011] The input / output feed lines are composed of microstrip lines and strip lines. The input / output feed lines are located in the middle circuit metal layer, perpendicular to the hypotenuse of the isosceles right triangle, and parallel to each other.

[0012] The first loaded slot line is perpendicular to the hypotenuse of the triangular resonant plate and is located on the perpendicular bisector of the hypotenuse;

[0013] The first metallized through hole is located above the first loading type slot line, and the edge of the first metallized through hole maintains a certain distance from the upper end of the first loading type slot line;

[0014] The second loading groove line is perpendicular to the hypotenuse of the isosceles right triangle and is located on the perpendicular bisector of the hypotenuse;

[0015] The triangular resonant plate is located inside the isosceles right triangle of the closed resonant cavity, and the triangular resonant plate coincides with the midline of the isosceles right triangle;

[0016] As a further optimization solution of the present invention, the length and width of the first loading slot line are changed to change the TM 100Resonant mode frequency;

[0017] As a further optimization solution of the present invention, by changing the diameter of the first metallized through hole (6), the size of the through hole equivalent inductance can be changed, and by changing the size of the triangular resonant plate (8), the size of the equivalent capacitance can be changed, thereby changing the LC resonant frequency;

[0018] As a further optimization solution of the present invention, the cavity TE is changed by changing the length and width of the second loading slot line. 201 The resonant frequency of the mode;

[0019] As a further optimization solution of the present invention, the matching within the passband is improved by changing the relative position of the input / output feed lines, the distance from the triangular resonator to the hypotenuse of the isosceles right triangle, and the length and width of the first loaded slot line.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following significant technical effects:

[0021] 1. Compared with the traditional SIW four-mode bandpass filter, the single-cavity four-mode closed miniaturized wide stopband bandpass filter proposed in the present invention has a passband center frequency in the fundamental mode resonant mode (TE 101 mold), so that the size of this structure is greatly reduced, with the advantages of small size, easy processing and integration, and low cost.

[0022] 2. The single-cavity four-mode closed miniaturized wide stopband bandpass filter proposed in the present invention is loaded by slot lines and triangular resonant plates and metal through-holes in an equivalent LC resonant circuit. 201 mode shifts to low frequencies, while higher order modes (such as TE 202 The resonant frequency of the mode) remains unchanged, while another resonant mode is introduced, thereby achieving a fourth-order bandwidth response and excellent out-of-band suppression performance, which is suitable for future millimeter-wave communication systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A perspective view of an embodiment of the present invention;

[0024] Figure 2 A top view of an embodiment of the present invention;

[0025] Figure 3 Graphs showing simulated and measured frequency response within the operating frequency band of an embodiment of the present invention.

[0026] Figure 4 Graphs showing simulated and measured frequency response outside the operating frequency band of an embodiment of the present invention.

[0027] In the figure: 1-upper metal plate, 2-upper microwave dielectric plate, 3-middle circuit metal layer, 4-lower microwave dielectric plate, 5-lower metal plate, 6-first metallized through hole, 7-metallized through hole, 8-triangular resonant plate, 9-first loaded slot line, 10-second loaded slot line, 11-isolation metal, 12-assembly metal hole. DETAILED DESCRIPTION

[0028] The present invention will be described in further detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0029] like Figure 1 、 2 As shown, the single-cavity four-mode substrate integrated waveguide wide stopband bandpass filter disclosed in an embodiment of the present invention includes an upper metal plate 1, an intermediate microwave dielectric plate 2, an intermediate circuit metal layer 3, an intermediate microwave dielectric plate 4, and a lower metal plate 5. The upper metal plate 1 and the lower metal plate 5 and the metallized through-hole 7 form a closed resonant cavity. The intermediate circuit metal layer 3 includes a pair of input / output feed lines, a triangular resonant plate 8, a first loaded slot line 9, a second loaded slot line 10, and a first metallized through-hole 6 above the first loaded slot line 9.

[0030] The intermediate circuit metal layer 3 is an isosceles right triangle, with two rows of plated vias 7 parallel to the right-angled sides of the triangle and perpendicular to each other. The input / output feed lines are composed of microstrip lines and striplines. The input / output feed lines are located in the intermediate circuit metal layer 3, perpendicular to the hypotenuse of the isosceles right triangle, and parallel to each other.

[0031] The first loaded slot line 9 is perpendicular to the hypotenuse of the triangular resonant plate and is located on the perpendicular bisector of the hypotenuse; the first metallized through-hole 6 is located above the first loaded slot line 9, and the edge of the first metallized through-hole 6 maintains a certain distance from the upper end of the first loaded slot line 9; the second loaded slot line 10 is perpendicular to the hypotenuse of the isosceles right triangle and is located on the perpendicular bisector of the hypotenuse; the triangular resonant plate 8 is located inside the isosceles right triangle of the closed resonant cavity, and the triangular resonant plate 8 coincides with the midline of the isosceles right triangle.

[0032] In order to achieve the miniaturization and wide stopband characteristics of the cavity filter, a second loaded slot line is introduced on the hypotenuse of the right triangle, which is used to convert the secondary resonance mode TE of the cavity into 201 The mode frequency is reduced and close to the TE101 mode, but the higher order modes of the HMSIW cavity, such as TE 202The mode is basically unaffected, so the introduction of the slot line can increase the bandwidth of the stop band. The introduction of the triangular resonant plate in the right triangle forms an equivalent capacitor, and the introduction of the first metallized through hole forms an equivalent inductor. The triangular resonant plate and the first metallized through hole together form an equivalent LC resonator, thereby generating a TE 101 A resonant mode with a lower frequency than TE 201 The high-frequency resonant mode of the triangular resonator couples with the two modes of the resonant cavity, forming a transmission zero in the high and low stop bands, respectively.

[0033] In order to verify the above analysis, this embodiment designs a device with a center frequency of 5.94 GHz, a 3-dB relative bandwidth of 11.2%, and a measured minimum insertion loss of 0.97 dB, which is as high as 2.24 f A single-cavity, four-mode, closed, miniaturized, wide-stopband bandpass filter with an out-of-band suppression of 24 dB at 0. First, the length of the second loaded slotline 10 was determined, resulting in a resonant frequency of approximately 6.1 GHz. Second, the length and width of the second loaded slotline 9 and the radius of the first plated through-hole 6 were varied to allow the triangular resonator to resonate at 5.6 GHz and 6.2 GHz. Finally, the appropriate in-band return loss was achieved by adjusting the input / output feeder lines.

[0034] like Figure 3 Shown are the simulated and measured frequency response curves of a single-cavity, four-mode, closed-type, miniaturized, wide-stopband bandpass filter. The simulated and measured frequency curves are consistent out-of-band, while the in-band return loss variation in the measured data is primarily due to manufacturing errors. In the measured data, the center frequency is 5.94 GHz, and the 3-dB relative bandwidth is 11.2% (5.61 GHz - 6.27 GHz). A transmission zero exists at 8 GHz, and out-of-band rejection reaches 24 dB across the frequency range from 6.45 GHz to 13.44 GHz. The experimental results confirm the design's wide passband bandwidth, excellent rejection characteristics, and stable performance.

[0035] In summary, the miniaturized wide stopband single-cavity four-mode closed miniaturized wide stopband bandpass filter of the present invention can have four resonant modes in the passband, while suppressing the stopband extending to 2.24 dB by 24 dB. f 0( f 0 is the center frequency), which can be well applied in future millimeter wave communication systems. In addition, the present invention also has a small size (only 0.175λ g 2 (λ g: waveguide wavelength of the center frequency), light weight, simple processing, easy integration and low manufacturing cost.

[0036] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A closed miniaturized wide stopband bandpass filter based on a single cavity and four modes, comprising an upper metal plate (1), an intermediate microwave dielectric plate (2), an intermediate circuit metal layer (3), an intermediate microwave dielectric plate (4), and a lower metal plate (5); characterized in that: The upper metal plate (1), the lower metal plate (5) and the metallized through hole (7) form a closed resonant cavity; the intermediate circuit metal layer (3) includes a pair of input / output feed lines, a triangular resonant plate (8), a first loaded slot line (9), a second loaded slot line (10), and a first metallized through hole (6) above the first loaded slot line (9); the intermediate circuit metal layer (3) is an isosceles right triangle; the two rows of metallized through holes (7) are parallel to the right angle sides of the isosceles right triangle and perpendicular to each other; the input / output feed lines are located in the intermediate circuit metal layer (3), perpendicular to the hypotenuse of the isosceles right triangle and parallel to each other; the triangular resonant plate (8) is located inside the closed resonant cavity, and the triangular resonant plate (8) coincides with the midline of the isosceles right triangle; the first loaded slot line (9) is perpendicular to the hypotenuse of the triangular resonant plate and is located on the perpendicular bisector of the hypotenuse; the second loaded slot line (10) Perpendicular to the hypotenuse of an isosceles right triangle and located on the perpendicular bisector of the hypotenuse.

2. The closed miniaturized wide stopband bandpass filter based on a single cavity and four modes according to claim 1, characterized in that: The input / output feed line is composed of a microstrip line and a stripline.

3. The closed miniaturized wide stopband bandpass filter based on a single cavity and four modes according to claim 1, characterized in that: The first metallized through hole (6) is located above the first loading type slot line (9), and the edge of the first metallized through hole (6) maintains a certain distance from the upper end of the first loading type slot line (9).

4. The closed miniaturized wide stopband bandpass filter based on a single cavity and four modes according to claim 1, characterized in that: The length and width of the first loading type slot line (9) can be changed, and the TM 100 Resonant mode frequency.

5. The closed miniaturized wide stopband bandpass filter based on a single cavity and four modes according to claim 1, characterized in that: The diameter of the first metallized through hole (6) can be changed, and the size of the triangular resonant plate (8) can be changed. By changing the diameter of the first metallized through hole (6), the size of the through hole equivalent inductance can be changed. By changing the size of the triangular resonant plate (8), the size of the equivalent capacitance can be changed, thereby changing the LC resonant frequency.

6. The closed miniaturized wide stopband bandpass filter based on a single cavity and four modes according to claim 1, characterized in that: The length and width of the second loading type slot line (10) can be changed, and the cavity TE can be changed by changing the length and width of the second loading type slot line. 201 The resonant frequency of the mode.

7. The closed miniaturized wide stopband bandpass filter based on a single cavity and four modes according to claim 1, characterized in that: The relative position of the input / output feeder, the distance from the triangular resonant plate (8) to the hypotenuse of the isosceles right triangle, and the length and width of the first loaded slot line (9) can all be changed. By changing the relative position of the input / output feeder, the distance from the triangular resonant plate to the hypotenuse of the isosceles right triangle, and the length and width of the first loaded slot line, the matching within the passband is improved.

Images