阅读说明：本技术 具有陷波特性的四频段微带带通滤波器及其设计方法 (Four-frequency-band microstrip band-pass filter with trapped wave characteristic and design method thereof ) 是由 孔勐 程彬彬 陈明生 杨周瑞 张忠祥 张量 柴豆豆 于 2019-10-21 设计创作，主要内容包括：本发明公开了一种具有陷波特性的四频段微带带通滤波器及其设计方法,所述具有陷波特性的四频段微带带通滤波器包括含有导体带、介质基片和接地板的电路板,所述电路板上设有短路穿孔；所述导体带包括输入端口、输出端口、馈线、两个第一阶梯阻抗谐振器、两个第二阶梯阻抗谐振器和两个F型开路枝节；所述馈线连接在输入端口和输出端口之间,两个第一阶梯阻抗谐振器连接在所述馈线的上端部,两个第二阶梯阻抗谐振器连接在所述馈线的下端部,两个F型开路枝节连接在所述馈线的上端部,所述第一阶梯阻抗谐振器位于两个F型开路枝节之间。本发明具有陷波特性,能够同时实现四个频段的带通滤波,并且结构简单、体积小、集成度高、性能优异、兼容性强。(The invention discloses a four-frequency-band microstrip band-pass filter with a trap characteristic and a design method thereof, wherein the four-frequency-band microstrip band-pass filter with the trap characteristic comprises a circuit board containing a conductor band, a dielectric substrate and a ground plate, and the circuit board is provided with a short circuit through hole; the conductor strip comprises an input port, an output port, a feeder line, two first stepped impedance resonators, two second stepped impedance resonators and two F-shaped open-circuit branches; the feeder line is connected between the input port and the output port, the two first stepped impedance resonators are connected to the upper end portion of the feeder line, the two second stepped impedance resonators are connected to the lower end portion of the feeder line, the two F-shaped open-circuit branches are connected to the upper end portion of the feeder line, and the first stepped impedance resonators are located between the two F-shaped open-circuit branches. The four-band-pass filter has the trap characteristic, can realize the band-pass filtering of four frequency bands simultaneously, and has the advantages of simple structure, small volume, high integration level, excellent performance and strong compatibility.)

1. A four-band microstrip band-pass filter with notch characteristics is characterized in that,

the circuit board comprises a conductor strip (1), a dielectric substrate (2) and a grounding plate (3) which are arranged in sequence;

the circuit board is provided with a short circuit through hole (4) penetrating through the conductor strip (1), the dielectric substrate (2) and the grounding plate (3), so that the conductor strip (1) penetrates through the dielectric substrate (2) and is connected with the grounding plate (3); wherein the conductor strip (1) comprises:

an input port (5) and an output port (6);

a feed line (7) connected between the input port (5) and the output port (6) by means of a stepped feed, the shorting via (4) passing through the feed line (7);

two first stepped impedance resonators connected to the upper end of the feed line (7) and bilaterally symmetric with respect to a center line (8) of the circuit board;

two second stepped impedance resonators connected to the lower end portions of the feed lines (7) and bilaterally symmetrical about a center line (8) of the circuit board;

and two F-shaped open-circuit branches which are connected to the upper end part of the feeder line (7) and are bilaterally symmetrical about a center line (8) of the circuit board, wherein the first stepped impedance resonator is positioned between the two F-shaped open-circuit branches.

2. The quad-band microstrip bandpass filter according to claim 1 wherein the F-type open stub comprises:

the inverted L-shaped open-circuit branch section (9) is connected to the feeder line (7);

and the rectangular open-circuit branch sections (10) are connected to the inverted L-shaped open-circuit branch sections (9) and are parallel to the feeder line (7).

3. The quad-band microstrip bandpass filter with notch characteristics according to claim 2, characterized in that the width of the rectangular open stub (10) is larger than the width of the inverted-L open stub (9).

4. The quad-band microstrip bandpass filter with notch characteristics according to claim 1,

the first stepped-impedance resonator comprises a first high-impedance branch (11) and a first low-impedance branch (12); wherein the content of the first and second substances,

the lower end part of the first high-impedance branch line (11) is connected to the feeder line (7);

one end of the first low-impedance branch line (12) is connected to the upper end of the first high-impedance branch line (11);

a coupling gap (13) is formed between the other end of the first low-impedance branch line (12) and the first low-impedance branch line (12) in the other first stepped-impedance resonator.

5. The quad-band microstrip bandpass filter with notch characteristics according to claim 1,

the second stepped-impedance resonator comprises a second high-impedance branch (14) and a second low-impedance branch (15); wherein the content of the first and second substances,

the upper end part of the second high-impedance branch line (14) is connected to the feeder line (7);

one end of the second low-impedance branch line (15) is connected with the lower end of the second high-impedance branch line (14);

the other end of the second low-impedance branch line (15) is connected to a second low-impedance branch line (15) in another second stepped-impedance resonator.

6. The quad-band microstrip bandpass filter with notch characteristics according to claim 1, characterized in that the shorting via (4) is located at the center of the circuit board and/or the diameter of the shorting via (4) is 0.5 mm.

7. The quad-band microstrip bandpass filter with notch characteristics according to claim 1, characterized in that the input port (5) and the output port (6) are symmetrically arranged with respect to a center line (8) of the circuit board and/or the first ladder impedance resonator and the second ladder impedance resonator are each a quarter of an operating wavelength in length.

8. The quad-band microstrip bandpass filter with notch characteristics according to claim 1, characterized in that the dielectric substrate (2) has a dielectric constant of 2.2; and/or the thickness of the dielectric substrate (2) is 0.707 mm; and/or the material of the medium substrate (2) is Rogers 5880; and/or the length of the medium substrate (2) is 35.8mm, and the width is 30.7 mm.

9. A method of designing a quad-band microstrip bandpass filter having a notch characteristic as claimed in any one of claims 1 ~ 8, wherein the method comprises the steps of:

s1: on the basis that the input port (5) and the output port (6) are connected to the feeder line (7) in a step feed connection mode and the input port (5) and the output port (6) share the short circuit through hole (4), a pair of first step impedance resonators, a pair of second step impedance resonators and a pair of F-shaped open-circuit branches are arranged on the dielectric substrate (2) in parallel;

s2: adjusting the sizes and the positions of the first stepped impedance resonator and the second stepped impedance resonator to adjust the working ranges of the highest frequency band and the lowest frequency band in the four frequency bands; and adjusting the size and the position of the F-shaped open circuit branch to adjust the working ranges and the trap point frequencies of the other two frequency bands in the four frequency bands so as to obtain the four-frequency-band microstrip band-pass filter with the trap characteristic meeting the requirements.

10. The design method according to claim 9, wherein the specific steps of step S2 are as follows:

m1: inverting the sizes of the first stepped impedance resonator and the second stepped impedance resonator according to the working ranges of the highest frequency band and the lowest frequency band in the four frequency bands, and inverting the sizes of the F-type open-circuit branches according to the working ranges and trap point frequencies of the other two frequency bands in the four frequency bands;

m2: and adjusting the positions of the first stepped impedance resonator, the second stepped impedance resonator and the F-shaped open-circuit stub to reduce the coupling interference among the first stepped impedance resonator, the second stepped impedance resonator and the F-shaped open-circuit stub at the same side and obtain the required four-band microstrip band-pass filter with the notch characteristic.

Technical Field

The invention relates to a four-band microstrip band-pass filter with a trapped wave characteristic and a design method thereof.

Background

In a mobile communication system, a filter is a radio frequency front-end device used for selecting an operating frequency band and filtering out-of-band interference. A filter is a two-port network having characteristics that provide signal transmission in the pass band frequencies and attenuation in the stop band to control the frequency response in a communication system. With the rapid development of modern mobile communication, the filter gradually develops towards the trend of miniaturization, high performance, low cost and multi-band, and the microstrip bandpass filter easily meets the above requirements, so that the microstrip bandpass filter has attracted the attention of researchers in the industry and is applied to various fields of the mobile communication industry.

At present, the fifth generation mobile communication (5G) is one of the most popular subjects of the global information industry, and a new technical revolution in the global mobile communication field is raised, China has made an important progress in the research and development of the 5G technology, the ministry of industry and communications has formally issued low-frequency band experimental frequencies in the 5G mobile communication to three operators of China mobile, China telecom, China Unicom and the like, wherein the frequencies are 2515MHz ~ 2675MHz, 3400MHz ~ 3500MHz, 3500MHz ~ 3600MHz and 4800MHz ~ 4900MHz, the existing filter cannot well realize the band-pass filtering of four frequency bands, cannot simultaneously construct the notch between adjacent narrow bands when realizing the band-pass filtering of the four frequency bands, and therefore cannot adapt to the use requirements of the 5G technology.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a four-frequency-band microstrip band-pass filter with a trapped wave characteristic, which has the trapped wave characteristic, can simultaneously realize the band-pass filtering of four frequency bands, and has the advantages of simple structure, small volume, high integration level, excellent performance and strong compatibility.

In order to solve the technical problems, the technical scheme of the invention is as follows: a four-band microstrip band-pass filter with a trap characteristic comprises a circuit board which comprises a conductor strip, a dielectric substrate and a grounding plate which are arranged in sequence;

the circuit board is provided with a short circuit through hole penetrating through the conductor strip, the dielectric substrate and the grounding plate, so that the conductor strip penetrates through the dielectric substrate and is connected with the grounding plate; wherein the conductor strip comprises:

an input port and an output port;

a feed line connected between the input port and the output port by way of a stepped feed, the shorting via passing through the feed line;

two first stepped impedance resonators connected to upper end portions of the feeder lines and symmetrical left and right with respect to a center line of the circuit board;

two second stepped impedance resonators connected to the lower end of the feed line and symmetrical to each other about the center line of the circuit board;

the first stepped impedance resonator is positioned between the two F-shaped open-circuit branches.

Further provides a specific construction scheme of the F-shaped open-circuit branch, and the F-shaped open-circuit branch comprises:

the inverted L-shaped open-circuit branch is connected to the feeder line;

and the rectangular open-circuit branch is connected to the inverted L-shaped open-circuit branch and is parallel to the feeder line.

Further, the width of the rectangular open-circuit branch is larger than that of the inverted L-shaped open-circuit branch.

There is further provided a concrete structure of the first stepped-impedance resonator, the first stepped-impedance resonator including a first high-impedance branch line and a first low-impedance branch line; wherein the content of the first and second substances,

the lower end part of the first high-impedance branch line is connected to the feed line;

one end of the first low-impedance branch line is connected to an upper end of the first high-impedance branch line;

a coupling gap is formed between the other end portion of the first low-impedance branch line and the first low-impedance branch line in the other first stepped-impedance resonator.

Further provided is a concrete structure of the second stepped-impedance resonator, which includes a second high-impedance branch line and a second low-impedance branch line; wherein the content of the first and second substances,

the upper end part of the second high-impedance branch line is connected to the feeder line;

one end part of the second low-impedance branch line is connected with the lower end part of the second high-impedance branch line;

the other end of the second low-impedance branch line is connected to a second low-impedance branch line in another second stepped-impedance resonator.

Further, the short circuit through hole is located at the center of the circuit board, and/or the diameter of the short circuit through hole is 0.5 mm.

Further, the input port and the output port are symmetrically arranged about a center line of the circuit board, and/or the lengths of the first stepped impedance resonator and the second stepped impedance resonator are both quarter of the working wavelength.

Further, the dielectric constant of the dielectric substrate is 2.2; and/or the thickness of the medium substrate is 0.707 mm; and/or the material of the medium substrate is Rogers 5880; and/or the dielectric substrate has a length of 35.8mm and a width of 30.7 mm.

The invention also provides a design method of the four-band microstrip band-pass filter with the trapped wave characteristic, and the method comprises the following steps:

s1: the input port and the output port are connected to a feed line in a stepped feed connection mode, and the input port and the output port share a short circuit through hole, and a pair of first stepped impedance resonators, a pair of second stepped impedance resonators and a pair of F-shaped open-circuit branches are arranged on the dielectric substrate in parallel;

s2: adjusting the sizes and the positions of the first stepped impedance resonator and the second stepped impedance resonator to adjust the working ranges of the highest frequency band and the lowest frequency band in the four frequency bands; and adjusting the size and the position of the F-shaped open circuit branch to adjust the working ranges and the trap point frequencies of the other two frequency bands in the four frequency bands so as to obtain the four-frequency-band microstrip band-pass filter with the trap characteristic meeting the requirements.

Further, the specific steps of step S2 are as follows:

m1: inverting the sizes of the first stepped impedance resonator and the second stepped impedance resonator according to the working ranges of the highest frequency band and the lowest frequency band in the four frequency bands, and inverting the sizes of the F-type open-circuit branches according to the working ranges and trap point frequencies of the other two frequency bands in the four frequency bands;

m2: and adjusting the positions of the first stepped impedance resonator, the second stepped impedance resonator and the F-shaped open-circuit stub to reduce the coupling interference among the first stepped impedance resonator, the second stepped impedance resonator and the F-shaped open-circuit stub at the same side and obtain the required four-band microstrip band-pass filter with the notch characteristic.

After the technical scheme is adopted, the four-band microstrip band-pass filter with the notch characteristic is simple in structure, small in size, high in integration level, excellent in performance and capable of achieving the notch characteristic and simultaneously achieving band-pass filtering of four working bands, the four working bands are respectively a first pass band, a second pass band, a third pass band and a fourth pass band, and the working ranges of the first pass band and the fourth pass band can be adjusted by adjusting the lengths and the widths of the first high-impedance branch line, the first low-impedance branch line, the second high-impedance branch line and the second low-impedance branch line and adjusting the distances between the first high-impedance branch line, the second high-impedance branch line and the second low-impedance branch line and between the first high-impedance; through adjusting the length of branch knot and the branch knot of opening a way of rectangle of type of falling L, adjust the branch knot of opening a way of type of falling L with distance between input port, the output port, adjust the branch knot of opening a way of rectangle and distance between the feeder can adjust the working range and the trapped wave point frequency of second passband and third passband to the frequency range of four working frequency ranges of regulation that need is nimble according to the design, make its operation requirement that adapts to 5G technique, and can also expand more working frequency ranges through adding suitable structures such as ladder impedance resonator, the design method is nimble simple, extensive applicability, and the compatibility is strong.

Drawings

FIG. 1 is a schematic diagram of a circuit board used in the present invention;

FIG. 2 is a schematic structural diagram of a four-band microstrip bandpass filter with notch characteristics according to the present invention;

FIG. 3 is a diagram of a signal path in a four-band microstrip bandpass filter with notch characteristics according to the present invention;

fig. 4 is a graph showing the insertion loss and return loss of the four-band microstrip bandpass filter having the notch characteristic according to the present invention.

Detailed Description

In order that the present invention may be more readily and clearly understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings.