CN110011014B

CN110011014B - Waveguide filter and method of manufacturing the same

Info

Publication number: CN110011014B
Application number: CN201910342676.1A
Authority: CN
Inventors: 李津; 黄冠龙; 袁涛
Original assignee: Shenzhen University
Current assignee: Shenzhen University
Priority date: 2019-04-26
Filing date: 2019-04-26
Publication date: 2020-11-13
Anticipated expiration: 2039-04-26
Also published as: CN110011014A

Abstract

The invention discloses a waveguide filter, and relates to the technical field of electromagnetic fields and microwaves. The waveguide filter includes: the waveguide resonator comprises a first waveguide flange plate, a second waveguide flange plate, a first waveguide, a second waveguide and four hemispherical resonators. And a through rectangular groove is formed in the cavity wall of the hemispherical resonator and is used for inhibiting the high-order resonance mode of electromagnetic waves in the hemispherical resonator, so that the parasitic-free stop band bandwidth of the waveguide filter is expanded. The invention also discloses a manufacturing method of the waveguide filter, the waveguide filter structure is integrally printed by adopting the metal powder material through the selective laser sintering 3-D printer, the precise processing is realized, the assembly and the debugging are not needed, and the manufacturing efficiency is effectively improved.

Description

Waveguide filter and method of manufacturing the same

Technical Field

The invention relates to the technical field of electromagnetic fields and microwaves, in particular to a waveguide filter and a manufacturing method thereof.

Background

The air-filled metal cavity resonator is a basic frequency selection unit in a microwave and millimeter wave passive circuit, has the advantages of low radio frequency loss and high power capacity, and is widely applied to engineering practices such as filters, multiplexers, antennas, impedance matching networks and the like. In general, these passive devices or circuits require a metal cavity resonator with a high unloaded quality factor to reduce rf losses.

The air-filled rectangular resonator and the air-filled cylindrical resonator are two common high-unloaded quality factor cavity resonators and are usually processed by a traditional material reduction manufacturing process such as computer numerical control milling. Thus, a metal cavity resonator with a higher unloaded quality factor is an air-filled spherical resonator. However, since the spherical resonator has a highly symmetrical physical structure, the resonant modes of the electromagnetic wave therein are highly degenerate, and the resonant frequencies of the higher-order modes of the electromagnetic wave are spectrally close to the fundamental mode. For bandpass filter applications, this limits the stop band bandwidth and the stop band rejection of the filter.

The physical structure of the microwave millimeter wave device based on the spherical resonator is complex, the microwave millimeter wave device is difficult to efficiently manufacture by adopting a computer numerical control milling process, and the structure of the cavity device is usually required to be split into a plurality of parts to be respectively processed and finally reassembled together when the cavity device is processed. Such mode of processing makes inefficiency, need use fasteners such as a large amount of screws and pins in the assembling process, and assembly error is big moreover, and redundant structure material is many, is unfavorable for realizing high performance, quick and the integration of cavity filtering subassembly in microwave millimeter wave communication system.

Disclosure of Invention

The invention mainly aims to provide a waveguide filter and a manufacturing method thereof, and aims to solve the technical problems that parasitic resonance introduced by a high-order mode of electromagnetic waves is not inhibited, parasitic resistance band width is not generated, the stop band inhibition degree is poor and the integrated processing and forming difficulty of the filter is high in the waveguide filter based on a spherical cavity resonator.

To achieve the above object, a first aspect of the present invention provides a waveguide filter, comprising: the waveguide resonator comprises a first waveguide flange plate, a second waveguide flange plate, a first waveguide, a second waveguide and four hemispherical resonators;

the first waveguide and the second waveguide are both rectangular waveguides, one end of the first waveguide is connected with the first waveguide flange, the other end of the first waveguide is connected with the hemispherical resonator, one end of the second waveguide is connected with the second waveguide flange, and the other end of the second waveguide is connected with the hemispherical resonator;

the four hemispherical resonators are all arranged between the first waveguide and the second waveguide and are air-filled cavity resonators, and the bottom planes between every two adjacent hemispherical resonators are mutually abutted, staggered and cascaded and arranged in a collinear manner;

the hemispherical top surfaces of the four hemispherical resonators are provided with through rectangular grooves;

the rectangular grooves of the hemispherical resonator are axially symmetrically formed along the symmetry line of the hemispherical surface of the hemispherical resonator; the extending direction of the rectangular groove formed in the hemispherical resonator is perpendicular to a connecting line between the input port of the first waveguide flange plate and the output port of the second waveguide flange plate;

the mutual abutting positions of the four hemispherical resonators are provided with circular windows for coupling electromagnetic energy between adjacent hemispherical resonators, and the bottom planes of the head hemispherical resonator and the tail hemispherical resonator are provided with semicircular windows for coupling electromagnetic energy with the first waveguide and the second waveguide respectively.

A second aspect of the present invention provides a waveguide filter, comprising: the waveguide resonator comprises a first waveguide flange plate, a second waveguide flange plate, a first waveguide, a second waveguide and four hemispherical resonators;

the four hemispherical resonators are all arranged between the first waveguide and the second waveguide and are all cavity resonators filled with air, and the four hemispherical resonators comprise: two slotless hemispherical resonators respectively coupled to the first waveguide and the second waveguide, and two slotted hemispherical resonators respectively coupled to the two slotless hemispherical resonators;

the bottom planes of the two slotted hemispherical resonators and the two slotless hemispherical resonators are in the same orientation, and every two adjacent hemispherical resonators are mutually abutted and cascaded and are arranged in a collinear manner;

the bottom plane and the hemispherical top surface of the slotted hemispherical resonator are both provided with through rectangular grooves;

rectangular grooves in the hemispherical top surface and the bottom plane of the slotted hemispherical resonator are axially symmetrically formed along the symmetry line of the hemispherical surface of the slotted hemispherical resonator; the extension directions of the rectangular grooves formed in the hemispherical top surface and the bottom plane of the slotted hemispherical resonator are perpendicular to a connecting line between the input port of the first waveguide flange plate and the output port of the second waveguide flange plate;

the butt joint of two adjacent hemispherical resonators is provided with a rectangular window for coupling electromagnetic energy between the adjacent hemispherical resonators, and the bottom planes of the head and tail two slotless hemispherical resonators are provided with semicircular windows for coupling the electromagnetic energy with the first waveguide and the second waveguide respectively.

A third aspect of the present invention provides a method of manufacturing a waveguide filter, the method comprising:

adjusting the placing angle of an electronic model of a waveguide filter on a system platform of a selective laser sintering 3-D printer to enable the electronic model to incline by a preset angle, and printing an original workpiece corresponding to the electronic model by using the selective laser sintering 3-D printer and adopting a metal powder material;

wherein the original workpiece comprises: the device comprises a first waveguide flange plate, a second waveguide flange plate, a first waveguide, a second waveguide and four hemispherical resonators, wherein an original workpiece is an inseparable whole;

and removing the metal supporting material generated in the selective laser sintering process on the outer surface of the original workpiece, and polishing and sand blasting the original workpiece to obtain the waveguide filter.

The invention provides a waveguide filter and a manufacturing method thereof, which have the advantages that: through the through rectangular groove formed in the cavity wall of the hemispherical resonator, the high-order electromagnetic wave resonance mode in the hemispherical resonator is effectively inhibited, the parasitic-free stop band bandwidth of the waveguide filter is expanded, and the stop band inhibition degree is improved; the waveguide filter is formed by integrally printing a metal powder material through a selective laser sintering 3-D printer, accurate processing is achieved, assembling and debugging are not needed, and manufacturing efficiency is effectively improved.

Drawings

In order to more clearly illustrate the embodiments or prior art solutions of the present invention, the drawings used in the embodiments or prior art solutions will be briefly described below. It is to be noted that the drawings in the following description are only some embodiments of the invention, and that other drawings may be derived from these drawings by a person skilled in the art without inventive effort.

Fig. 1 is an oblique perspective view of a waveguide filter according to an embodiment of the present invention;

fig. 2 is a cross-sectional view of a waveguide filter along a direction a-a' in fig. 1 according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram of a waveguide flange of a waveguide filter according to an embodiment of the present invention;

fig. 4 is an oblique perspective view of a waveguide filter according to a second embodiment of the present invention;

fig. 5 is a cross-sectional view of a waveguide filter along a direction a-a' in fig. 4 according to a second embodiment of the present invention;

FIG. 6 shows the embodiment of the invention according to FIGS. 1, 2 and 3 with the waveguide filter slotted in front and at the back of the X to K_uSimulated transmission coefficient (S) in frequency band₂₁Parameter) graph;

FIG. 7 shows the second embodiment of the present invention according to FIGS. 4 and 5, in which the waveguide filter is slotted in front of and behind the notch in the range from X to K_uSimulated transmission coefficient (S) in frequency band₂₁Parameter) graph;

FIG. 8 is a schematic flow chart of a method for manufacturing a waveguide filter according to an embodiment of the present invention;

FIG. 9 is a graph of simulated and measured scattering parameters (S-parameters) for a waveguide filter according to the first embodiment of the present invention, as shown in FIGS. 1, 2 and 3;

fig. 10 is a graph showing a simulated and measured scattering parameter (S-parameter) of the waveguide filter according to the second embodiment of the present invention shown in fig. 4 and 5.

In the first embodiment, each reference numeral indicates:

1. a first waveguide flange; 2. a second waveguide flange; 3. a first hemispherical resonator; 301. a first rectangular groove; 31. a second hemispherical resonator; 311. a second rectangular groove; 32. a third hemispherical resonator; 321. a third rectangular groove; 33. a fourth hemispherical resonator; 331. a fourth rectangular groove; 302. a first circular window; 312. a second circular window; 322. a third circular window; 303. a first semicircular window; 332. a second semicircular window; 4. a first waveguide; 5. a second waveguide; 6. and a through hole.

In embodiment two, each reference numeral indicates:

11. a first waveguide flange; 12. a second waveguide flange; 13. a first slotless hemispherical resonator; 14. a second slotless hemispherical resonator; 15. a first slotted hemispherical resonator; 16. a second slotted hemispherical resonator; 131. a first rectangular window; 151. a second rectangular window; 161. a third rectangular window; 132. a first semicircular window; 141. a second semicircular window; 152. a first rectangular groove; 153. a second rectangular groove; 162. a third rectangular groove; 163. a fourth rectangular groove; 17. a first waveguide; 18. a second waveguide.

Detailed Description

In order to make the objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. It should be noted that the described embodiments are only some embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the embodiments of the present invention, given that the structural dimensions are preferred parameters, the dimensional parameters of the various components can be further modified to obtain the actually desired performance with reference to the embodiments of the present invention.

Referring to fig. 1 and 2, fig. 1 is an oblique perspective view of a waveguide filter according to an embodiment of the present invention, and fig. 2 is a cross-sectional view of the waveguide filter according to the embodiment of the present invention along a direction a-a' in fig. 1, the waveguide filter including:

the waveguide resonator comprises a first waveguide flange plate 1, a second waveguide flange plate 2, a first waveguide 4, a second waveguide 5 and four hemispherical resonators; specifically, the four hemispherical resonators are the first hemispherical resonator 3, the second hemispherical resonator 31, the third hemispherical resonator 32, and the fourth hemispherical resonator 33, respectively, in this order from the first waveguide 4 to the second waveguide 5.

Wherein the flange is a component for interconnection between the waveguide port and the waveguide port for connection between the waveguide ends. Waveguide flanges are flanges that are fixed to the waveguide terminals in an arrangement and can be fitted with fittings for alignment and clamping with mating flanges. In the first embodiment of the invention, the first waveguide flange plate 1 and the second waveguide flange plate 2 are both in size of WR-90 standard rectangular waveguide flange plate under the X frequency band, and the sections of the first waveguide flange plate 1 and the second waveguide flange plate 2 are both rectangular.

Further, in electromagnetism and communication engineering, a waveguide refers to a physical structure that transmits electromagnetic energy between its ports, and common waveguide structures mainly include parallel twin wires, coaxial lines, parallel slab waveguides, rectangular waveguides, circular waveguides, microstrip lines, slab dielectric waveguides, and the like. From the perspective of conducting electromagnetic waves, the waveguide structure can be divided into an inner region and an outer region, and electromagnetic waves are generally confined to propagate in the inner region of the waveguide. In the embodiment of the invention, the adopted wave guide structure is a rectangular wave guide, the section of the rectangular wave guide is rectangular, and the interior of the rectangular wave guide is filled with air.

Further, the first waveguide 4 and the second waveguide 5 are both rectangular waveguides, one end of the first waveguide 4 is connected to the first waveguide flange 1, the other end of the first waveguide is connected to the first hemispherical resonator 3, one end of the second waveguide 5 is connected to the second waveguide flange 2, and the other end of the second waveguide is connected to the fourth hemispherical resonator 33;

further, the first hemispherical resonator 3, the second hemispherical resonator 31, the third hemispherical resonator 32 and the fourth hemispherical resonator 33 are all arranged between the first waveguide 4 and the second waveguide 5 in sequence, and are all cavity resonators filled with air, and bottom planes between every two adjacent hemispherical resonators are mutually abutted, staggered and cascaded and arranged in a collinear manner.

Further, a first rectangular groove 301 is formed in the hemispherical top surface of the first hemispherical resonator 3; a second rectangular groove 311 is formed in the hemispherical top surface of the second hemispherical resonator 31; a third rectangular groove 321 is formed in the hemispherical top surface of the third hemispherical resonator 32; and the hemispherical top surface of the fourth hemispherical resonator 33 is provided with a fourth rectangular groove 331, and the rectangular grooves provided on the hemispherical top surfaces of the four hemispherical resonators all penetrate through the hemispherical top surface.

Furthermore, the rectangular grooves of the hemispherical resonator are axially symmetrically arranged along the symmetry line of the hemispherical surface of the hemispherical resonator; the extending directions of the rectangular grooves formed in the hemispherical resonator are perpendicular to a connecting line between the input port of the first waveguide flange plate 1 and the output port of the second waveguide flange plate 2.

Further, mode coupling between the first hemispherical resonator 3 and the second hemispherical resonator 31 is realized by the first circular window 302 formed therein; the mode coupling between the second hemispherical resonator 31 and the third hemispherical resonator 32 is realized by the second circular window 312; the mode coupling between the third hemispherical resonator 32 and the fourth hemispherical resonator 33 is realized by a third circular window 322 formed by the third hemispherical resonator; the coupling between the first hemispherical resonator 3 and the first waveguide 4 is realized through a first semicircular window 303 formed in the first hemispherical resonator; the coupling between the fourth hemispherical resonator 33 and the second waveguide 5 is achieved through the second semicircular window 332 opened therein. By adjusting the radius of the first circular window 302, the strength of mode coupling between the first hemispherical resonator 3 and the second hemispherical resonator 31 can be adjusted; by adjusting the radius of the second circular window 312, the strength of mode coupling between the second hemispherical resonator 31 and the third hemispherical resonator 32 can be adjusted; by adjusting the radius of the third circular window 322, the strength of the mode coupling between the third hemispherical resonator 32 and the fourth hemispherical resonator 33 can be adjusted, thereby designing a desired filter bandwidth. The coupling strength of the first hemispherical resonator 3 and the first waveguide 4 can be adjusted by adjusting the radius of the first semicircular window 303, and the coupling strength of the fourth hemispherical resonator 33 and the second waveguide 5 can be adjusted by adjusting the radius of the second semicircular window 332, so that a desired band-pass filter response is realized.

Specifically, the first circular window 302, the second circular window 312, and the third circular window 322 have radii of 4.241 mm, 3.977 mm, and 4.241 mm, respectively, and the first semicircular window 303 and the second semicircular window 332 each have a radius of 7.297 mm.

Referring to fig. 3, fig. 3 is a schematic structural diagram of a waveguide flange of a waveguide filter according to an embodiment of the present invention. The first waveguide flange plate 1 and the second waveguide flange plate 2 are both in the size of an X-frequency-band standard rectangular waveguide flange plate WR-90, the length of the wide side of a waveguide opening is a, a is 22.86 mm, the length of the narrow side is b, and b is 10.16 mm. As shown in fig. 3, the first waveguide flange 1 and the second waveguide flange 2 each include four through holes 6 that are axisymmetrically distributed, and the waveguide filter is connected to other waveguide components through the through holes 6 by screws and nuts in practical use. The detailed dimensions of the flanges and the location of the through holes refer to the WR-90 flange and through hole parameters in the national code BJ100 standard.

In the first embodiment, the thicknesses of the first waveguide flange 1 and the second waveguide flange 2 are both 3 mm, and the lengths of the first waveguide 4 and the second waveguide 5 are 20 mm.

According to the first embodiment of the present invention, the waveguide filter includes four hemispherical resonators with through rectangular slots, the intrinsic resonant frequency of each hemispherical resonator is determined by the radius r of the air cavity of the hemisphere, and the larger the radius of the air cavity of the hemispherical resonator is, the lower the intrinsic resonant frequency is.

Fundamental mode TM of free-space lower hemispherical resonator₁₀₁The resonant frequency of a mode is determined by equation 1, equation 1 being expressed as follows:

in equation 1, r is expressed in millimeters, and the size of the open rectangular slot does not significantly degrade the fundamental mode TM of the hemispherical resonator₁₀₁Within the unloaded quality factor of the mode, for TM₁₀₁The effect of the resonant frequency of the mode is negligible.

First and second higher order resonant modes TM of free space lower hemispherical resonator_2m1Die and TE₁₀₁The eigenresonance frequencies of the modes are determined by equation 2 and equation 3, respectively, equation 2 being expressed as follows:

equation 3 is expressed as follows:

for example, a hemispherical resonator with an air cavity radius of 13.1 mm, the fundamental mode TM thereof₁₀₁Eigenresonance frequency of the mode is about10GHz, first and second higher order resonant modes TM_2m1Die and TE₁₀₁The eigenresonance frequencies of the modes are about 14.1GHz and 16.37GHz, respectively. Specifically, in the first embodiment of the present invention, in order to realize the passband center frequency of the waveguide filter at 10GHz, the radii of the four hemispherical resonators, i.e., the first hemispherical resonator 3, the second hemispherical resonator 31, the third hemispherical resonator 32, and the fourth hemispherical resonator 33 are 12.691 mm, 12.981 mm, 12.981 mm, and 12.691 mm, respectively, in order from the first waveguide flange 1 to the second waveguide flange 2. The cavity wall thicknesses of the hemispherical bottom planes of the four hemispherical resonators are all 1 mm, and the cavity wall thicknesses of the hemispherical top surfaces are all 3 mm.

According to the first embodiment of the invention, the hemispherical top surfaces of the four slotted hemispherical resonators are respectively provided with a through rectangular groove, and the rectangular grooves are characterized in that:

1. the slotted length direction of the rectangular slot is perpendicular to the TM needed to be suppressed in the hemispherical resonator_2m1Die and TE₁₀₁The mould induces current direction on the hemispherical surface, and the slotting position of the rectangular groove is positioned at TM_2m1Die and TE₁₀₁The region of the mode where the induced current density is greatest. In particular, in the first embodiment, the first rectangular groove 301 formed in the hemispherical top surface of the first hemispherical resonator 3, the second rectangular groove 311 formed in the hemispherical top surface of the second hemispherical resonator 31, the third rectangular groove 321 formed in the hemispherical top surface of the third hemispherical resonator 32, and the fourth rectangular groove 331 formed in the hemispherical top surface of the fourth hemispherical resonator 33 have their groove length directions perpendicular to the connecting line between the input port of the first waveguide flange 1 and the output port of the second waveguide flange 2;

2. the rectangular grooves are axially symmetrically formed along the hemispherical symmetry line of the corresponding hemispherical resonator;

3. the rectangular through-slots being provided for breaking the TM_2m1Die and TE₁₀₁The induced current distribution of the modes suppresses these two higher order modes to the maximum. The length and width of the rectangular groove satisfy TM_2m1Die and TE₁₀₁Sufficient suppression of the mode is achieved without significantly deteriorating the fundamental mode TM₁₀₁Mold carrierAnd (4) quality factor. Specifically, in the first embodiment of the present invention, the opening lengths of the rectangular grooves of the four hemispherical resonators correspond to a center angle of 90 degrees, and the widths of the rectangular grooves are 4 millimeters.

Referring to fig. 4 and 5, fig. 4 and 5 are oblique perspective views of a waveguide filter according to a second embodiment of the present invention, and fig. 5 is a cross-sectional view of the waveguide filter according to the second embodiment of the present invention along a direction a-a' in fig. 4, the waveguide filter including:

the waveguide resonator comprises a first waveguide flange plate 11, a second waveguide flange plate 12, a first waveguide 17, a second waveguide 18 and four hemispherical resonators; the four hemispherical resonators include: the first and second slotted

hemispherical resonators

13 and 14 are connected to the first and

second waveguides

17 and 18, respectively, and the first and second slotted

hemispherical resonators

15 and 16 are connected to the first and second slotted

hemispherical resonators

13 and 14, respectively, and the first and second slotted

hemispherical resonators

15 and 16 are connected to each other.

Further, the first waveguide 17 and the second waveguide 18 are both rectangular waveguides, one end of the first waveguide 17 is connected to the first waveguide flange 11, the other end of the first waveguide is connected to the first slotless hemispherical resonator 13, one end of the second waveguide 18 is connected to the second waveguide flange 12, and the other end of the second waveguide is connected to the second slotless hemispherical resonator 14. In the second embodiment of the present invention, the first waveguide flange 11 and the second waveguide flange 12 are both the size of the WR-90 standard rectangular waveguide flange at the X frequency band, and the sections of the first waveguide flange 11 and the second waveguide flange 12 are both rectangular. In the second embodiment, the thickness of the first waveguide flange 11 and the second waveguide flange 12 is 4 mm, and the length of the first waveguide 17 and the second waveguide is 20 mm.

Further, the four hemispherical resonators are all arranged between the first waveguide 17 and the second waveguide 18 and are all air-filled cavity resonators, wherein the structures are fixedly connected according to the sequence of the first waveguide 17, the first slotless hemispherical resonator 13, the first slotted hemispherical resonator 15, the second slotted hemispherical resonator 16, the second slotless hemispherical resonator 14 and the second waveguide 18. Specifically, the radii of the first slotless hemispherical resonator 13, the first slotted hemispherical resonator 15, the second slotted hemispherical resonator 16 and the second slotless hemispherical resonator 14 are 12.599 mm, 12.749 mm, 12.749 mm and 12.599 mm, respectively. The cavity wall thickness of the hemispherical bottom plane of the hemispherical resonator is 3 mm, and the cavity wall thickness of the hemispherical top surface is 3 mm.

Furthermore, the bottom planes of the two slotted hemispherical resonators and the two slotless hemispherical resonators are in the same orientation, and every two adjacent hemispherical resonators are mutually abutted and cascaded and are arranged in a collinear manner;

furthermore, the mode coupling between two adjacent hemispherical resonators of the waveguide filter is realized by a rectangular window formed at the abutting position of the hemispherical resonators, that is, the mode coupling between the first slotless hemispherical resonator 13 and the first slotted hemispherical resonator 15 is realized by a first rectangular window 131 formed at the abutting position, the mode coupling between the first slotted hemispherical resonator 15 and the second slotted hemispherical resonator 16 is realized by a second rectangular window 151 formed at the abutting position, and the mode coupling between the second slotted hemispherical resonator 16 and the second slotless hemispherical resonator 14 is realized by a third rectangular window 161 formed at the abutting position. The input and output coupling of the waveguide filter is realized by semicircular windows arranged on the bottom planes of the head and tail two slotless hemispherical resonators, namely, the coupling of the first slotless hemispherical resonator 13 and the first waveguide 17 is realized by a first semicircular window 132 arranged on the first slotless hemispherical resonator, the coupling of the second slotless hemispherical resonator 14 and the second waveguide 18 is realized by a second semicircular window 141 arranged on the second slotless hemispherical resonator, and the input and output coupling strength of the waveguide filter can be adjusted by adjusting the radiuses of the first semicircular window 132 and the second semicircular window 141, so that the required band-pass filtering response is realized. Specifically, the first rectangular window 131, the second rectangular window 151, and the third rectangular window 161 have widths of 9.209 mm, 8.498 mm, and 9.209 mm, respectively, and heights of 6 mm. The semicircular windows for input and output coupling are located in the chamber wall with a thickness of 1 mm.

Further, the bottom plane and the hemispherical top surface of the first slotted hemispherical resonator 15 are respectively provided with a first rectangular groove 152 and a second rectangular groove 153, and the bottom plane and the hemispherical top surface of the second slotted hemispherical resonator 16 are respectively provided with a third rectangular groove 162 and a fourth rectangular groove 163.

Further, a first rectangular groove 152 and a second rectangular groove 153 formed in the first slotted hemispherical resonator 15 are axially symmetrically formed along a symmetry line of a hemispherical surface of the first slotted hemispherical resonator 15; the extending directions of the first rectangular groove 152 and the second rectangular groove 153 are perpendicular to a connecting line between the input port of the first waveguide flange 11 and the output port of the second waveguide flange 12; the third rectangular groove 162 and the fourth rectangular groove 163 formed in the second slotted hemispherical resonator 16 are formed in axial symmetry along the line of symmetry of the hemispherical surface of the second slotted hemispherical resonator 16; the extending directions of the third rectangular groove 162 and the fourth rectangular groove 163 are perpendicular to the connection line between the input port of the first waveguide flange 11 and the output port of the second waveguide flange 12.

The first rectangular groove 152, the second rectangular groove 153, the third rectangular groove 162, and the fourth rectangular groove 163 are characterized in that:

1. the slot length direction of the second rectangular slot 153 and the fourth rectangular slot 163 is perpendicular to the TM required to be inhibited_2m1Die and TE₁₀₁The die induces a current in the direction of its corresponding grooved hemisphere, and the position of the groove is located at the TM_2m1Die and TE₁₀₁The region of the mode where the induced current density is greatest. In particular, in the second embodiment, the length directions of the second rectangular groove 153 and the fourth rectangular groove 163 are both perpendicular to the connection line between the input port of the first waveguide flange 11 and the output port of the second waveguide flange 12;

2. the slot length direction of the first rectangular slot 152 and the third rectangular slot 162 is perpendicular to the TE to be suppressed₁₀₁The die induces a current in the direction of its corresponding grooved bottom plane, and the grooving position is at TE₁₀₁The region of the mode where the induced current density is greatest. In particular, in the second embodimentIn the middle, the length directions of the first rectangular groove 152 and the third rectangular groove 162 are both perpendicular to a connecting line between the input port of the first waveguide flange 11 and the output port of the second waveguide flange 12;

3. the slotted structures of the first rectangular slot 152 and the second rectangular slot 153 are axisymmetrical along the hemispherical symmetry line of the first slotted hemispherical resonator 15; the slotted structures of the third rectangular slot 162 and the fourth rectangular slot 163 are axisymmetrical along the hemispherical surface of the second slotted hemispherical resonator 16;

4. the first rectangular groove 152, the second rectangular groove 153, the third rectangular groove 162 and the fourth rectangular groove 163 are opened to break the TM_2m1Die and TE₁₀₁The induced current distribution of the modes suppresses these two higher order modes to the maximum. The first rectangular groove 152, the second rectangular groove 153, the third rectangular groove 162 and the fourth rectangular groove 163 have the groove length and width satisfying the TM_2m1Die and TE₁₀₁Sufficient suppression of the mode is achieved without significantly deteriorating the fundamental mode TM₁₀₁Unloaded quality factor of the mode. Specifically, the widths of the second rectangular groove 153 and the fourth rectangular groove 163 are both 4 mm, and the spherical center angle corresponding to the lengths is 90 degrees; the first rectangular groove 152 and the third rectangular groove 162 each have a width of 1.5 mm and a length of 23 mm.

It should be noted that the second rectangular slot 153 and the fourth rectangular slot 163 can be implemented for TM at the same time_2m1Die and TE₁₀₁Suppression of the mold due to the grooved area on the top surface of the hemisphere, TM_2m1Die and TE₁₀₁The induced current of the mode has an overlapping component and the current density is maximum. The first rectangular groove 152 and the third rectangular groove 162 are only for TE₁₀₁Mold generation is suppressed because of the slotted area in the hemispherical bottom plane, TE₁₀₁Maximum TM of induced current density of mode_2m1The induced current density of the mode is minimal.

Referring to fig. 6 and 7, fig. 6 shows the waveguide filter of fig. 1, 2 and 3 according to the first embodiment of the present invention before and after notching in the X to K directions_uSimulated transmission coefficient (S) in frequency band₂₁Parametric) graph, fig. 7 shows the second embodiment of the present invention according to fig. 4 and 5, before and after the waveguide filter is slottedX to K_uSimulated transmission coefficient (S) in frequency band₂₁Parameter) profile.

In order to preliminarily verify the suppression effect of the slotting structure of the hemispherical resonator on the stop-band parasitic resonance of the waveguide filter, the physical models of the two waveguide filters in the first embodiment of the invention relating to fig. 1, fig. 2 and fig. 3 and the second embodiment of the invention relating to fig. 4 and fig. 5 are subjected to electromagnetic simulation, and the simulation result is shown in fig. 6 and fig. 7. Simulation results show that after the hemispherical resonator is slotted in the manner described in the first embodiment and the second embodiment, the parasitic resonance of the two waveguide filters is effectively suppressed near 14GHz, and the simulated stop band suppression degree is respectively better than 38dB and 42dB in the frequency range from 10.5GHz to 16.2 GHz.

Referring to fig. 8, fig. 8 is a schematic flow chart illustrating a method for manufacturing a waveguide filter according to an embodiment of the present invention. As shown in fig. 8, the flowchart includes:

s101, adjusting the placing angle of an electronic model of a waveguide filter on a system platform of a selective laser sintering 3-D printer to enable the electronic model to incline by a preset angle, and printing an original workpiece corresponding to the electronic model by using a metal powder material through the selective laser sintering 3-D printer;

the electronic model of the waveguide filter is arranged reasonably, so that the electronic model is inclined by a preset angle, no metal supporting material is generated inside the metal cavity of the waveguide filter in the process of printing the waveguide filter by the selective laser sintering 3-D printer, and the cavity structure of the waveguide filter can be completely stacked layer by layer through laser sintering metal powder to realize self-supporting molding.

Further, the electronic model of the waveguide filter is a three-dimensional electronic model of the waveguide filter designed according to the design principles of the above-described embodiments of the invention.

Furthermore, the first waveguide flange plate, the second waveguide flange plate, the first waveguide, the second waveguide and the four hemispherical resonators of the waveguide filter are integrally printed by a 3-D printer by using metal powder as a structural material. The metal powder can be made of metal materials such as aluminum alloy, stainless steel and titanium alloy, preferably aluminum alloy powder is used as a structural material and is integrally printed by a selective laser sintering 3-D printer.

Further, an industrial-grade direct metal laser sintering 3-D printer is adopted, a laser adopted by the 3-D printer is an yttrium fiber laser, the laser power is 400 watts, the aluminum alloy powder is selectively sintered in the environment of protective gas argon, the diameter of a laser spot in a sintering area is 100 micrometers, and the longitudinal printing resolution, namely the stacking layer thickness of the printing material, is 60 micrometers. And after the selective laser sintering 3-D printer completes the printing task, taking out the original workpiece, and carrying out the following subsequent treatment on the original workpiece.

S102, removing a metal supporting material generated on the outer surface of the original workpiece in the selective laser sintering process, and polishing and sand blasting the original workpiece to finally obtain the waveguide filter.

Among the process of polishing and sand blasting original workpieces, the polishing process is to manually polish the outer surfaces of the workpieces by tools such as files, coarse sand paper and the like so as to obtain smoother outer surfaces, the sand blasting process is to place the workpieces subjected to the polishing process in a sand blasting machine to perform omnibearing sand blasting on the inner and outer surfaces of the workpieces, and the aim of further reducing the roughness of the surfaces of the sintered aluminum alloy workpieces is achieved.

Referring to fig. 9, fig. 9 is a graph illustrating scattering parameters (S-parameters) simulated and measured by the waveguide filter according to the first embodiment of the present invention shown in fig. 1, fig. 2 and fig. 3, wherein fig. 9(a) is an S-parameter curve around the pass band of the waveguide filter, and fig. 9(b) is an S-parameter curve of the waveguide filter in the frequency band from X to Ku.

In order to verify the rf performance of the waveguide filter according to the first embodiment of the present invention, fig. 1, fig. 2 and fig. 3 relate to, the scattering parameters (S-parameters) of the waveguide filter were simulated and measured. It can be seen that the waveguide filter in the first embodiment according to fig. 1, 2 and 3 achieves the desired chebyshev bandpass filter response, with a measured passband in the range of 9.92-10.22 GHz, a passband average insertion loss of 1dB, a passband return loss of better than 15dB, and a passband center frequency shifted by about 86MHz (relative frequency shift of about 0.86%) from the simulated value to the high frequency. The frequency shift is due to the fact that the metal material after laser sintering and cooling causes the air cavity volume of the resonator to shrink to less than the design's preferred value. Frequency shifts due to volume shrinkage can be reduced by structurally compensating the printed electronic model prior to printing. The quality of the waveguide filter printed by the integrated 3-D printing is 83 grams, assembling and any fastener are not needed, manual debugging is not needed in the testing process, and the waveguide filter can be used after being processed. Meanwhile, the notch structure does not have obvious influence on the passband radio frequency performance of the waveguide filter, the stop band rejection degree of the tested waveguide filter is better than 34dB up to 16.4GHz, the stop band rejection degree is better than 11dB up to 18GHz, and the frequency range of a non-parasitic stop band is larger than 1.8: 1.

Referring to fig. 10, fig. 10 is a graph showing scattering parameters (S-parameters) simulated and measured by the waveguide filter according to the second embodiment of the present invention shown in fig. 4 and 5, in which fig. 10(a) is an S-parameter curve around the pass band of the waveguide filter, and fig. 10(b) is an S-parameter curve of the waveguide filter in the X-Ku frequency band.

In order to verify the rf performance of the waveguide filter according to the second embodiment of the present invention, fig. 4 and 5 relate to a simulation and measurement of the scattering parameter (S-parameter) of the waveguide filter. It can be seen that the waveguide filter of the second embodiment according to fig. 4 and 5 achieves the desired chebyshev bandpass filter response, with a measured passband in the range of 10-10.23 GHz, a passband average insertion loss of 0.9dB, a passband return loss of better than 20dB, a passband center frequency shifted towards high frequency by about 115MHz (about 1.15% shift relative frequency) from the simulated value, again due to the volume shrinkage of the resonator's air cavity after laser sintering and re-cooling of the metallic material, which is less than the design preference. Frequency shifts due to volume shrinkage can be reduced by structurally compensating the printed electronic model prior to printing. The quality of the waveguide filter printed by the integrated 3-D printing is 103 g, assembling and any fastener are not needed, manual debugging is not needed in the testing process, and the waveguide filter can be used after being processed. Meanwhile, the notch structure does not have obvious influence on the passband radio frequency performance of the waveguide filter, the stop band rejection degree of the tested waveguide filter is better than 32dB up to 16.4GHz, the stop band rejection degree is better than 11dB up to 18GHz, and the frequency range of a non-parasitic stop band is larger than 1.8: 1.

In both embodiments provided in the present application, it should be understood that the disclosed structures and methods of fabrication may be implemented in other ways. For example, the two embodiment structures of the waveguide filter described above are merely illustrative, such as: the sizes of the notches of the rectangular grooves are only a few physical structures which can be realized, the sizes can be designed into other reasonable sizes according to the design principle and the working frequency of the filter in practice, cavity slotting patterns in other shapes can be designed to achieve the purpose of inhibiting high-order resonant modes of electromagnetic waves, and flexible filter structure design and better radio frequency response can be realized by changing the order of the waveguide filter, the number of slotted hemispherical resonators, the coupling topology, the slotting positions and the like. In addition, the waveguide filter can be processed by adopting other metal powder materials through a selective laser sintering or selective laser melting technology, other additive manufacturing technologies based on non-metal materials can be adopted to be realized by being assisted by a surface metallization technology, and a proper 3-D printing material and a proper 3-D printer can be selected according to the requirements of practical application.

In view of the above description of the waveguide filter and the manufacturing method thereof provided by the present invention, those skilled in the art will recognize that there may be variations in the embodiments and applications of the concepts according to the embodiments of the present invention.

Claims

1. A waveguide filter, comprising:

the waveguide resonator comprises a first waveguide flange plate, a second waveguide flange plate, a first waveguide, a second waveguide and four hemispherical resonators;

rectangular grooves in the hemispherical top surface and the bottom plane of the slotted hemispherical resonator are axially symmetrically formed along the symmetry line of the hemispherical surface of the slotted hemispherical resonator;

the extending direction of the rectangular grooves formed in the semispherical top surface and the bottom plane of the slotted semispherical resonator is perpendicular to a connecting line between the input port of the first waveguide flange plate and the output port of the second waveguide flange plate.

2. The waveguide filter of claim 1,

3. The waveguide filter of claim 2 wherein the first waveguide flange and the second waveguide flange each contain a plurality of through-holes;

the first waveguide flange plate, the second waveguide flange plate, the first waveguide, the second waveguide and the four hemispherical resonators are all made of metal powder serving as structural materials through selective laser sintering and 3-D printer integrated printing.

4. A waveguide filter manufacturing method for manufacturing a waveguide filter according to any one of claims 1 to 3, the method comprising: