WO2018171179A1

WO2018171179A1 - Dual-band bandpass filter with high selectivity

Info

Publication number: WO2018171179A1
Application number: PCT/CN2017/107192
Authority: WO
Inventors: 曲美君; 邓力; 李书芳; 张贯京; 葛新科; 高伟明; 张红治
Original assignee: 深圳市景程信息科技有限公司
Priority date: 2017-03-18
Filing date: 2017-10-21
Publication date: 2018-09-27
Also published as: CN106921012A; CN106921012B

Abstract

The present invention provides a dual-band bandpass filter with high selectivity, comprising two first microstrip lines, an input end, an output end, and a second microstrip line provided on the upper surface of a dielectric slab. Both ends of each first microstrip line are provided with an open load and a shorted load, respectively; the middle parts of the two first microstrip lines are connected by means of the second microstrip line; the input end is connected to one of the first microstrip lines, and the output end is connected to the other first microstrip line; both ends of the second microstrip line are respectively communicated with the input end and the output end, and are located on the same horizontal line; the horizontal line serves as a first central axis; a second central axis is perpendicular to the first central axis; the tail end of the shorted load is provided with a shorted metal post, which is connected to a ground metal layer provided on the lower surface of the dielectric slab. The dual-band bandpass filter with high selectivity of the present invention exerts a good suppression effect on out-of-band signals, has high selectivity, introduces less noise, and avoids interference to a radio frequency front end.

Description

Highly selective dual band pass filter

[0001] The present invention relates to the field of radio frequency microwave communication technologies, and in particular, to a high selectivity dual band pass filter.

Background technique

[0002] As a very important device in the RF front-end, the filter can filter out-of-band noise and improve the sensitivity of the circuit system. A microstrip filter is a device used to separate microwave signals of different frequencies. Its main function is to suppress unwanted signals so that they cannot pass through the filter and only pass the desired signal. In microwave circuit systems, the performance of the filter has a large impact on the performance of the circuit system. Due to the diversity of communication bands in modern communication systems, the selectivity of prior art bandpass filters is often insufficient to meet the diversity of communication bands and affect the performance of the entire communication system.

technical problem

[0003] It is an object of the present invention to provide a highly selective dual band pass filter which aims to solve the technical problem of the low selectivity of the conventional band pass filter.

Problem solution

Technical solution

[0004] In order to achieve the above object, the present invention provides a high selectivity dual band pass filter comprising a dielectric plate, two first microstrip lines etched on a surface of the dielectric plate, an input end, an output end, and a first a second microstrip line, and a ground metal layer disposed on a lower surface of the dielectric plate, the high selectivity dual band pass filter being vertically symmetric about the first central axis and bilaterally symmetric about the second central axis, wherein:

[0005] The two ends of each of the first microstrip lines are respectively provided with a circuit load and a short circuit load, and the middle portions of the two first microstrip lines are connected by the second microstrip line;

[0006] one end of the input end is disposed in a middle of one of the first microstrip lines and the other end of the input end extends to a long edge of the dielectric plate;

[0007] one end of the output end is disposed in a middle of another first microstrip line and the other end of the output end extends to another long edge of the dielectric plate;

[0008] Both ends of the second microstrip line are respectively connected to the input end and the output end, and are located on the same horizontal line, the water The flat line is the first central axis, and the second central axis is perpendicular to the first central axis;

[0009] The end of the short-circuit load is provided with a short-circuited metal post that penetrates from the upper surface of the dielectric plate to the lower surface of the dielectric plate and is connected to the ground metal layer disposed on the lower surface of the dielectric plate.

[0010] Preferably, the ground metal layer is a copper-clad metal layer laid on a lower surface of the dielectric plate.

[0011] Preferably, the two first microstrip lines are disposed parallel to each other on the upper surface of the dielectric plate and are bilaterally symmetric with respect to the second central axis, and the two ends of the second microstrip line are vertically connected to the two A microstrip between the lines.

[0012] Preferably, the number of one end of the bypass load and the number of short-circuit loads are four, and one end load and one short-circuit load are respectively disposed at two ends of each first microstrip line.

[0013] Preferably, the first microstrip line, the second microstrip line, the crotch load, the short-circuit load, the input end, and the output end are all metal strips of a strip structure.

[0014] Preferably, the length of the first microstrip line is 2L1+W=2x22.5mm+1.66mm=46.66mm, the width is Wl=1.22mm, and the length of the second microstrip line is L0=9.78 Mm, width W0=1.35mm, the length of the input end and the output end are both L=14.4mm, and the width is W=1.66mm.

[0015] Preferably, the short-circuit load has a length of L2=l lmm and a width of W2=3 mm, and the length of the open-circuit load is L3=l lmm and the width is W3=1.7 mm.

[0016] Preferably, the short-circuited metal pillar has a column shape.

[0017] Preferably, the dielectric plate is a PCB having a thickness of 0.762 mm and a relative dielectric constant of 3.66.

Advantageous effects of the invention

Beneficial effect

Compared with the prior art, the high-selective dual-band pass filter of the present invention loads four turn-on loads and four short-circuit loads on two microstrip lines, by adjusting the turn-on load and the short-circuit load. The length and width can form a transmission zero in a specific frequency band, so that the original microstrip line has filtering performance, thereby having a higher band pass selectivity, which can have a good suppression effect on the out-of-band signal and a high passband signal. Selectivity, introduce less noise, and avoid interference with the RF front end. Compared to the existing band pass filter, four turn-on loads and four short-circuit loads are connected to the conventional microstrip line through two first microstrip lines, and the present invention can be made by changing the length and width of the microstrip line. The high selectivity dual band pass filter achieves a good matching effect in the operating frequency band.

Brief description of the drawing DRAWINGS

1 is a schematic diagram showing the structure of the upper surface of the high-selectivity dual-band pass filter of the present invention.

2 is a schematic diagram showing the structure of the lower surface of the high-selectivity dual-band pass filter of the present invention.

3 is a schematic diagram of S-parameter results of the high-selectivity dual-band pass filter of the present invention simulated by electromagnetic simulation software.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be further described in detail with reference to the specific embodiments, which are to be construed as the invention.

Referring to FIG. 1, FIG. 1 is a schematic diagram showing the upper surface structure of the high-selectivity dual-band pass filter of the present invention. In this embodiment, the high-selectivity dual-band pass filter includes a dielectric plate 1, two first microstrip lines 10 etched on the upper surface of the dielectric plate 1, an input terminal P1, an output terminal P2, and a second micro A strip 11 and a ground metal layer 14 disposed on the lower surface of the dielectric plate (refer to FIG. 2). The two ends of each of the first microstrip lines 10 are respectively provided with a bypass load 12 and a short-circuit load 13. The middle portions of the two first microstrip lines 10 are connected by the second microstrip line 11, and one end of the input end P1 is disposed at One of the first microstrip lines 10 and the other end of the input end P1 extends to one long edge of the dielectric plate 1, and one end of the output end P2 is disposed at the middle of the other first microstrip line 10 and the output end The other end of P2 extends to the other long edge of the PCB board 2. A short-circuited metal post 130 is disposed at the end of each of the short-circuit loads 13, and the short-circuited metal post 130 may have a columnar shape such as a cylindrical shape or a long cylindrical shape. The dielectric plate 1 is a PCB board, and the specific plate type is Roger.

RO4350B, which has a relative dielectric constant of 3.66 and a plate thickness of 0.762 mm.

[0024] The two ends of the second microstrip line 11 are respectively connected to the input end PI and the output end P2 and are located on the same horizontal line ab. In this embodiment, the horizontal line ab is used as the first central axis ab. The high-selectivity dual-band pass filter of the present invention is vertically symmetrical about the first central axis ab, and is bilaterally symmetric about the second central axis cd, and the first central axis ab and the second central axis cd are perpendicular to each other. The two first microstrip lines 10 are disposed in parallel with each other on the upper surface of the dielectric plate 1 and are symmetric with respect to the second central axis cd, and the second microstrip line 11 and the two first microstrip lines 10 are perpendicularly connected to each other. One end of the bypass load 12 and one end of the short-circuit load 13 are disposed at both ends of each of the first microstrip lines 10 at an arbitrary angle of intersection and communicate with each other. In this embodiment, one end of the open circuit load 12 and one end of the short-circuit load 13 are disposed at opposite ends of each of the first microstrip lines 10 at a mutually orthogonal angle and phase Interconnected.

[0025] It should be noted that the long edge of the dielectric plate 1 defined by the present embodiment refers to the two edges of the dielectric plate 1 parallel to the second central axis cd. The two first microstrip lines 10 are spaced apart by a distance equal to the length of the second microstrip line 11. When one end of the bypass load 12 and one end of the short-circuit load 13 are connected to each other at both ends of the first microstrip line 10 in a mutually orthogonal manner, the distance between the bypass load 12 and the short-circuit load 13 is smaller than the two first microstrips. The separation distance between the lines 10. Since both ends of the two first microstrip lines 10 are provided with a turn-on load 12 and a short-circuit load 13, the high-selective dual-band pass filter of the present invention has four turn-on loads 12 and four Short-circuit load 13. Four open circuit loads 12 and four short circuit loads 13 enable the high selectivity dual band pass filter of the present invention to have two stop bands in any operating frequency band, thereby enabling the highly selective dual band pass filter of the present invention It has dual frequency characteristics and high band pass selectivity.

In the present embodiment, the first microstrip line 10, the second microstrip line 11, the open circuit load 12, the short-circuit load 13, the input end P1, and the output end P2 are all metal strips of a strip structure. The high-selectivity dual-band pass filter of the present invention is connected to the second microstrip line 11 via two first microstrip lines 12 with respect to the existing band pass filter, four turn-on loads 12 and four short-circuit loads 13. Above, and by changing the length and width of the microstrip line, the high-selectivity dual-band pass filter of the present invention can achieve a good matching effect in the operating frequency band.

[0027] The present invention is exemplified by a dual frequency characteristic in which the operating frequency band is implemented in the range of 2.61 GHz to 3.23 GHz and in the range of 4.75 GHz to 5.02 GHz, and the first microstrip line disposed on the upper surface of the dielectric board 1 by way of a specific embodiment. 10. The length and width of the second microstrip line 11, the bypass load 12, the short-circuit load 13, the input terminal P1, and the output terminal P2. In the present embodiment, the length of the first microstrip line 10 is 2L1 + W = 2x22.5mm + 1.66mm = 46.66mm, and the width of the first microstrip line 10 is Wl = 1.22mm. The length of the second microstrip line 11 is L0 = 9.78 mm, and the width of the second microstrip line 11 is W0 = 1.35 mm. The lengths of the input terminal PI and the output terminal P2 are both L=14.4 mm, and the widths of the input terminal P1 and the output terminal P2 are both W=1.66 mm. The length of the bypass load 12 is L3 = l l mm, the width of the bypass load 12 is W3 = 1.7 mm; the length of the short-circuit load 13 is L2 = l lmm, and the width of the short-circuit load 13 is W2 = 3 mm. It should be noted that the thickness of the metal copper plate disposed on the PCB board is generally um level, so the present invention does not apply to the first microstrip line 10, the second microstrip line 11, the open circuit load 12, the short-circuit load 13, and the input end. The thickness of the metal copper of P1 and the output terminal P2 is limited, and does not affect the characteristics of the high-selectivity dual-band pass filter of the present invention.

Referring to FIG. 2, FIG. 2 is a schematic diagram showing the structure of the lower surface of the high-selectivity dual-band pass filter of the present invention. In In this embodiment, the short-circuited metal post 130 at the end of each short-circuit load 13 penetrates from the upper surface of the dielectric plate 1 to the lower surface of the dielectric plate 1, and is connected to the ground metal layer 14 of the lower surface of the dielectric plate 1, the ground metal layer. 14 is a copper-clad metal layer laid on the lower surface of the dielectric plate 1.

[0029]

[0030] The high-selectivity dual-band pass filter of the present invention is designed by the above structure, by loading four turn-on loads 12 and four short-circuit loads 13 on a conventional microstrip line, by adjusting the switch load 12 and The length and width of the short-circuit load 13 can form a transmission zero in a specific operating frequency band, so that the original microstrip line has filtering performance, can have a good suppression effect on the out-of-band signal, has high selectivity to the passband signal, and introduces more Less noise, avoiding interference to the RF front end.

Referring to FIG. 3, FIG. 3 is a schematic diagram of S-parameter results of the high-selectivity dual-band pass filter of the present invention simulated by electromagnetic simulation software. In general, in general, bandpass filters allow signals from different frequency bands to enter the system, filtering out of the out-of-band signals or noise. As can be seen from FIG. 3, the reflection coefficient (IS11I) of the high-selectivity dual-band pass filter of the present invention is below -10 dB in the range of 2.61 GHz to 3.23 GHz and in the range of 4.75 GHz to 5.02 GHz, indicating that the height is high. The selective dual band pass filter can operate from 2.61 GHz to 3.23 GHz and from 4.75 GHz to 5.02 GHz, thus enabling dual frequency characteristics. At 2.13 GHz, the transmission characteristics (IS21I) of the high-selectivity dual-band pass filter of the present invention can reach -35.8 dB, and at 4.13 GHz, the IS21I can reach -50.6 dB, and at 5.27 GHz, the IS21I can reach - 34dB, so the high selectivity dual band pass filter of the present invention has high selectivity. It can be seen that the high-selective dual-band pass filter of the present invention can have a good suppression effect on the out-of-band signal, has high selectivity to the passband signal, introduces less noise, and avoids interference to the RF front end, so Improve the performance of microwave circuits.

[0032] The high-selectivity dual-band pass filter of the present invention loads four turn-on loads 12 and four short-circuit loads 13 on two microstrip lines by adjusting the lengths of the turn-on load 12 and the short-circuit load 13 The width can form a transmission zero in a specific frequency band, so that the original microstrip line has filtering performance, thereby having higher band pass selectivity. The high-selectivity dual-band pass filter of the present invention connects four turn-on loads 12 and four short-circuit loads 13 to the conventional microstrip line through two first microstrip lines 12 with respect to the existing band pass filter. And by changing the length and width of the microstrip line, the high-selectivity dual-band pass filter of the present invention can achieve a good matching effect in the operating frequency band.

The above is only a preferred embodiment of the present invention, and thus does not limit the scope of the patent of the present invention. The equivalent structure or equivalent flow of the invention and the equivalents of the drawings are directly or indirectly applied to other related technical fields, and are included in the scope of patent protection of the present invention.

Industrial applicability

Compared with the prior art, the high-selectivity dual-band pass filter of the present invention loads four turn-on loads and four short-circuit loads on two microstrip lines, by adjusting the lengths of the crowbar load and the short-circuit load. The width can form a transmission zero in a specific frequency band, so that the original microstrip line has filtering performance, thereby having high band pass selectivity, capable of suppressing the out-of-band signal, and having high selectivity to the pass band signal. Introduce less noise to avoid interference with the RF front end. Compared to the existing band pass filter, four turn-on loads and four short-circuit loads are connected to the conventional microstrip line through two first microstrip lines, and the present invention can be made by changing the length and width of the microstrip line. The high selectivity dual band pass filter achieves a good matching effect in the operating frequency band.

Claims

Claim

A highly selective dual band pass filter comprising a dielectric plate, two first microstrip lines etched on a surface of the dielectric plate, an input end, an output end and a second microstrip line, and a lower surface of the dielectric plate a ground metal layer, wherein the high-selectivity dual-band pass filter is vertically symmetrical about a first central axis and symmetrical about a second central axis, wherein: each of the first microstrip lines is respectively provided with The crotch load and the short-circuit load, the middle portions of the two first microstrip lines are connected by the second microstrip line; one end of the input end is disposed in the middle of one of the first microstrip lines and the other end of the input end extends to the medium a long edge of the plate; one end of the output end is disposed in a middle portion of the other first microstrip line and the other end of the output end extends to another long edge of the dielectric plate; both ends of the second microstrip line Connected to the input end and the output end respectively and on the same horizontal line, the horizontal line serves as a first central axis, and the second central axis and the first central axis are perpendicular to each other; The short circuit terminal is provided with a metal column, the short metal post penetrating from the upper surface of the dielectric plate to the lower surface of the dielectric plate and the surface of the metal layer is connected to ground and disposed under the dielectric plate.

The high-selectivity dual-band pass filter according to claim 1, wherein the ground metal layer is a copper-clad metal layer laid on a lower surface of the dielectric plate.

The high-selectivity dual-band pass filter according to claim 1, wherein the two first microstrip lines are disposed in parallel with each other on an upper surface of the dielectric plate and are bilaterally symmetrical with respect to the second central axis, The two ends of the second microstrip line are vertically connected between the two first microstrip lines. The high selectivity dual band pass filter according to claim 1, wherein one end of the open circuit load and the short circuit load The number of each is four, and each of the first microstrip lines is provided with a bypass load and a short-circuit load respectively.

The high-selectivity dual-band pass filter according to claim 1, wherein the first microstrip line, the second microstrip line, the crotch load, the short-circuit load, the input end, and the output end are strip-shaped Structure of the metal copper sheet.

The high-selectivity dual-band pass filter according to claim 5, wherein the length of the first microstrip line is 2L1+W=2x22.5mm+1.66mm=46.66mm, and the width is Wl=1.22mm, the length of the second microstrip line is L0=9.78mm, the width is W0=1.35 mm, the length of the input end and the output end are both L=14.4mm, and the width is W=1.66mm°

[Claim 7] The high-selectivity dual-band pass filter according to claim 6, wherein the short-circuit load has a length of L2 = l lmm and a width of W2 = 3 mm, and the length of the bypass load It is L3 = l lmm and the width is W3 = 1.7 mm.

[Claim 8] The high-selectivity dual-band pass filter according to claim 1, wherein the short-circuited metal post has a columnar shape.

[Claim 9] The high-selectivity dual-band pass filter according to any one of claims 1 to 8, wherein the dielectric plate is a PCB having a thickness of 0.762 mm and a relative dielectric constant of 3.66. Board