阅读说明：本技术 一种基于多层平行板波导的宽带线源 (Broadband line source based on multilayer parallel plate waveguide ) 是由 吴锡东 童利 冀俊超 周金芳 王成龙 于 2021-06-30 设计创作，主要内容包括：本发明公开了一种基于多层平行板波导的宽带线源,包括依次层叠设置的第一平行板波导、第二平行板波导、第三平行板波导,所述第一平行板波导与第二平行板波导通过第一弧形弯头连接,所述第二平行板波导与第三平行板波导通过第二弧形弯头连接,所述第一平行板波导的输入端口与H面喇叭连接,所述第三平行板波导的输出端口与第三弯头连接。该线源为宽带结构,能够增大横向输出范围的同时,有效减小线源纵向尺寸,在一维平面上得到相位均匀分布,幅度为余弦函数分布的平面波,从而有效减小大口径阵列天线的体积与加工难度。(The invention discloses a broadband line source based on multilayer parallel plate waveguides, which comprises a first parallel plate waveguide, a second parallel plate waveguide and a third parallel plate waveguide which are sequentially stacked, wherein the first parallel plate waveguide and the second parallel plate waveguide are connected through a first arc-shaped elbow, the second parallel plate waveguide and the third parallel plate waveguide are connected through a second arc-shaped elbow, an input port of the first parallel plate waveguide is connected with an H-plane horn, and an output port of the third parallel plate waveguide is connected with a third elbow. The line source is of a broadband structure, the longitudinal size of the line source can be effectively reduced while the transverse output range can be enlarged, the plane waves with uniformly distributed phases and cosine function distribution amplitudes are obtained on a one-dimensional plane, and therefore the size and the processing difficulty of the large-caliber array antenna are effectively reduced.)

1. The broadband line source is characterized by comprising a first parallel plate waveguide, a second parallel plate waveguide and a third parallel plate waveguide which are sequentially stacked, wherein the first parallel plate waveguide and the second parallel plate waveguide are connected through a first arc-shaped elbow, the second parallel plate waveguide and the third parallel plate waveguide are connected through a second arc-shaped elbow, an input port of the first parallel plate waveguide is connected with an H-plane horn, and an output port of the third parallel plate waveguide is connected with a third elbow.

Preferably, the H-plane horn is composed of two inclined planes and two planes, wherein the direction of the inclined planes is the direction of the electric field, and the direction of the planes is the direction of the magnetic field.

Preferably, the H-plane horn is arranged along a transverse central axis of the line source, and upper and lower wide surfaces of the H-plane horn are respectively connected with upper and lower surfaces of the first parallel plate waveguide.

Preferably, the opening of the H-face horn faces the first arc-shaped elbow, and cylindrical waves radiated from the output port of the horn are symmetrically distributed along the transverse central axis.

Preferably, the H-face horn may not be directly connected to the first curved elbow, and the transverse dimension D2 of the first curved elbow may be equal to the overall transverse dimension D1 of the line source or smaller than the overall transverse dimension D1 of the line source;

preferably, the H-plane horn can also be directly connected with the first arc-shaped elbow, and the transverse dimension D2 of the first arc-shaped elbow is smaller than the overall transverse dimension D1 of the line source;

preferably, the first parallel plate waveguide, the second parallel plate waveguide and the third parallel plate waveguide are replaced by a substrate integrated waveguide.

Preferably, the central axes of the first arc-shaped elbow and the second arc-shaped elbow are coincident.

2. The multilayer parallel plate waveguide-based broadband line source of claim 1, wherein the input port of the H-plane horn is connected to a rectangular waveguide.

Preferably, the rectangular waveguide is arranged along a transverse central axis of the line source, the upper wide surface and the lower wide surface of the rectangular waveguide are respectively connected with the upper wide surface and the lower wide surface of the H-face horn, and the height of the rectangular waveguide is the same as that of the H-face horn.

Preferably, the main mode of the rectangular waveguide is a TE10 mode.

3. The broadband line source based on the multilayer parallel plate waveguide of claim 1, wherein the first arc-shaped elbow is a C-shaped cavity structure, the inner wall of the cavity is made of a metal material, and the C-shaped opening faces the inner side of the line source structure and is used for changing the transmission direction and phase distribution of electromagnetic waves in the waveguide.

Preferably, the transverse rotation radian of the first arc-shaped elbow meets the following formula:

wherein:a is half of the overall transverse dimension D1 of the line source, and e is the value rangeIs constant.

4. The broadband line source based on the multilayer parallel plate waveguide as claimed in claim 1 or 3, wherein the contact position of the first arc-shaped elbow with the first parallel plate waveguide and the second parallel plate waveguide is provided with upper and lower symmetrical first matching for realizing the turning of the propagation direction of the plane wave.

Preferably, the first matching step is a rectangular step, or a triangular step with a certain radian.

Preferably, the first matching step may turn the propagation direction of a plane wave passing through the first parallel-plate waveguide by 180 degrees, and enter the second parallel-plate waveguide.

5. The broadband line source based on the multilayer parallel plate waveguide of claim 1, wherein the second arc-shaped elbow is a C-shaped cavity structure, the inner wall of the cavity is made of a metal material, and the C-shaped opening faces the inner side of the line source structure and is used for changing the transmission direction and phase distribution of electromagnetic waves in the waveguide.

Preferably, the transverse rotation radian of the second arc-shaped elbow meets the following formula:

X²4fY, wherein: f is a value range ofIs constant.

6. The broadband line source based on the multilayer parallel plate waveguide as claimed in claim 1 or 6, wherein the contact position of the second arc-shaped elbow with the second parallel plate waveguide and the third parallel plate waveguide is provided with an upper and a lower two symmetrical second matching steps for realizing the turning of the propagation direction of the plane wave.

Preferably, the second matching step is a rectangular step, or a triangular step with a certain radian.

Preferably, the second matching step may turn the propagation direction of the plane wave passing through the second parallel-plate waveguide by 180 degrees, and enter the third parallel-plate waveguide.

7. The broadband line source based on the multilayer parallel plate waveguide of claim 1, wherein the third bend is an L-shaped bend, and the rotation radian in the transverse direction is a straight line.

Preferably, the L-shaped elbow is formed by an L-shaped corner and a third mating step.

Preferably, the third matching step is a rectangular step, or a triangular step with a certain radian.

8. The multilayer parallel plate waveguide-based broadband line source of claim 1, wherein the output port of the third parallel plate waveguide is disposed directly above the third parallel plate waveguide for connecting a CTS antenna.

9. The multilayer parallel plate waveguide-based broadband line source of claim 1, wherein the first parallel plate waveguide, the second parallel plate waveguide and the third parallel plate waveguide are separated by a thin metal plate.

Preferably, the upper, lower and side walls of the first, second and third parallel plate waveguides are made of metal conductors, and the side walls are adhered with wave-absorbing materials.

10. An antenna comprising a broadband line source based on multilayer parallel plate waveguides as claimed in any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of antenna feed sources, in particular to a broadband line source based on multilayer parallel plate waveguides.

Background

The array antenna has good performance, and is widely applied to the fields of radar, communication, rocker telemetry, space technology and the like. With the continuous progress of communication systems, low-cost, miniaturized, high-gain, high-efficiency, broadband array antennas are urgently needed in modern communication systems. Conventional array antennas include microstrip array antennas, parabolic antennas, lens antennas, and the like.

The waveguide is a common low-loss transmission line, is an important wave guide device for transmitting electromagnetic waves by adopting a metal tube, and the tube wall of the waveguide is usually made of copper, aluminum or other metal materials. The waveguide has no inner conductor, electromagnetic energy is guided and transmitted in the inner space of the waveguide, and external electromagnetic wave leakage can be prevented. In the design of the antenna and the wire source thereof, the waveguide has stronger practical significance due to the characteristics of low loss and high power capacity. The PPW (Parallel Plate Waveguide) can be obtained by unfolding a one-dimensional Waveguide structure into a two-dimensional structure, and the PPW is composed of two flat plates and has the excellent characteristics of simple structure, low section, small insertion loss and the like. Unlike conventional waveguides, it is capable of transmitting TEM modes, and also has a wider bandwidth. There are few reports of antennas based on two-dimensional PPW structures and their associated theories. The two-dimensional structure has more design freedom for antenna research, so that the problems in the design of the large-aperture antenna can be solved. The ideal PPW structure is not present because the parallel plates require support of the boundary. When studying PPW in practice, one or more of its boundaries will typically be closed, similar to a waveguide with a long side of the cross-section being much larger than the narrow side.

In the design of parallel plate waveguide array antennas, it is often necessary to design line sources. Compared with the open structure of the antenna, the line source is a closed structure, and the line source can output plane electromagnetic waves with equal phase distribution for feeding the antenna. The line sources of the conventional waveguide antenna are mainly classified into two types according to the amplitude distribution manner, one is a discrete line source, and the other is a continuous line source. The performance of the line source not only has direct influence on the matching of the antenna, but also the characteristics of the amplitude and the phase of the electromagnetic wave output by the line source have decisive influence on the radiation field gain and the side lobe level of the antenna, and meanwhile, the size of the line source directly determines the minimum size of the array antenna. Therefore, the design of the line source is critical to obtain good overall antenna performance.

The application number is 201310409126.X discloses a broadband line source for a planar waveguide CTS antenna feeding device, which comprises an H-surface sectorial horn antenna, an offset reflecting surface and a slab waveguide, wherein the H-surface sectorial horn antenna and the offset reflecting surface are arranged inside the slab waveguide, and the phase center of the H-surface sectorial horn antenna is arranged at the focus of the offset reflecting surface. The wide-band line source is characterized in that the horn antenna is arranged at the focus of the reflector, and the field radiated by the horn antenna generates plane waves with equal phase distribution at the aperture surface of the reflector through the reflector. However, this broadband line source has a problem that the overall longitudinal dimension is large, which is disadvantageous for the miniaturization design of the broadband line source.

The application number 201610523014.0 discloses a broadband line source for a planar CTS antenna, which comprises a feed network, a first rectangular waveguide and a plurality of H-surface single-ridge rectangular waveguide T-shaped junctions with the same structure size, wherein the network is a power divider and is formed by sequentially arranging a plurality of H-surface single-ridge rectangular waveguide T-shaped junctions at transverse zero intervals to form an H-surface single-ridge rectangular waveguide T-shaped junction array. The broadband line source uniformly distributes the energy of the electromagnetic wave input into the rectangular waveguide to obtain the plane wave with equal amplitude distribution and equal phase distribution at the waveguide of the output parallel plate. However, the broadband line source has the following problems: firstly, because the line source adopts a power divider, the longitudinal width of the line source is increased by multiple times while the transverse output range is enlarged, and the feed source is not suitable for large-caliber small-size array antennas; in the design process of the array antenna line source, in order to meet the low-sidelobe performance of the antenna, the line source is generally required to be capable of outputting plane waves with the amplitude distributed in a cosine law, the broadband line source can only output plane waves with the constant-amplitude distribution, and when the broadband line source is used as the line source, the antenna sidelobe is higher.

The Chinese patent with the application number of 201621478793.9 discloses an H-face horn line source, which comprises an input rectangular waveguide, an H-face horn connected to the input rectangular waveguide, and a metamaterial arranged on the caliber surface of the H-face horn. The metamaterial comprises a plurality of conductive microstructures, wherein the conductive microstructures are arranged on a substrate in an array mode at one stage. The line source achieves the function of adjusting the equivalent refractive index of electromagnetic waves on a caliber surface through the arrangement of the metamaterial, so that plane waves with equal phase distribution are obtained at an output port. However, the broadband line source has the following problems: the bandwidth of a line source is limited by the bandwidth of a metamaterial, and the designed line source is often a narrow-band line source; and secondly, the transverse output distance of the line source is limited, so that the antenna is not suitable for a large-aperture array antenna.

Therefore, with the wide application of the large-aperture array antenna, the problems of the existing line source technology are as follows: the output transverse size is small, the bandwidth is narrow, the longitudinal size is overlarge, and the output amplitude distribution does not meet the low side lobe characteristic of the antenna.

Disclosure of Invention

Based on the technical defects in the prior art, the invention mainly aims to provide a broadband line source based on multilayer parallel plate waveguides, so as to solve the problems of line source miniaturization and broadband and output amplitude distribution during large-caliber feeding.

In order to achieve the purpose, the invention adopts the following technical scheme: a broadband line source based on multilayer parallel plate waveguides comprises a first parallel plate waveguide, a second parallel plate waveguide and a third parallel plate waveguide which are sequentially stacked, wherein the first parallel plate waveguide and the second parallel plate waveguide are connected through a first arc-shaped elbow, the second parallel plate waveguide and the third parallel plate waveguide are connected through a second arc-shaped elbow, an input port of the first parallel plate waveguide is connected with an H-plane horn, and an output port of the third parallel plate waveguide is connected with a third elbow. The line source is of a broadband structure, the longitudinal size of the line source can be effectively reduced while the transverse output range can be enlarged, the plane waves with uniformly distributed phases and cosine function distribution amplitudes are obtained on a one-dimensional plane, and therefore the size and the processing difficulty of the large-caliber array antenna are effectively reduced.

Furthermore, the H-face horn is composed of two inclined planes and two planes, wherein the direction of the inclined planes is the direction of the electric field, and the direction of the planes is the direction of the magnetic field. The H-plane horn is arranged along the transverse central axis of the line source, and the upper wide surface and the lower wide surface of the H-plane horn are respectively connected with the upper surface and the lower surface of the first parallel plate waveguide. The opening of the H-face loudspeaker faces to the direction of the first arc-shaped elbow, and cylindrical waves radiated from the output port of the loudspeaker are symmetrically distributed along the transverse central axis. The width of output cylindrical wave beams can be adjusted by adjusting the size of the opening of the horn, and the shape of the horn inclined plane can be pyramid or exponentially and gradually changed.

Further, the H-face horn may not be directly connected to the first arc-shaped bend, and at this time, the transverse dimension D2 of the first arc-shaped bend may be equal to the overall transverse dimension D1 of the line source or may be smaller than the overall transverse dimension D1 of the line source, so that the amplitude distribution of the output plane wave obtained by the structure is steeper, and the suppression effect of the side lobe level is better. The overall transverse dimension D1 of the line source and the transverse dimension D2 of the first arcuate bend are shown in figure 14.

Furthermore, the H-plane horn can also be directly connected with the first arc-shaped elbow, and the transverse dimension D2 of the first arc-shaped elbow is smaller than the overall transverse dimension D1 of the line source, so that the structure has higher caliber efficiency. The overall transverse dimension D1 of the line source and the transverse dimension D2 of the first arcuate bend are shown in figure 14.

Further, the input port of the H-face horn is connected with the rectangular waveguide, and can be externally connected with a mode conversion device (for example, a microstrip waveguide transition structure, a standard coaxial waveguide transition structure, etc.). In order to achieve good impedance performance, the rectangular waveguide is arranged along the transverse central axis of the line source, the upper wide surface and the lower wide surface of the rectangular waveguide are respectively connected with the upper wide surface and the lower wide surface of the H-face horn, and the height of the rectangular waveguide is the same as that of the H-face horn. The primary mode of the rectangular waveguide is the TE10 mode. The opening of the H-face horn is larger than lambda, wherein lambda is the waveguide wavelength of the highest frequency transmission electromagnetic wave.

Furthermore, the first arc-shaped elbow is of a C-shaped cavity structure, the inner wall of the cavity is made of metal materials, and the C-shaped opening faces the inner side of the line source structure and is used for changing the transmission direction and phase distribution of electromagnetic waves in the waveguide. The transverse rotation radian of the first arc-shaped elbow meets the following formula:

wherein:a is half of the overall transverse dimension D1 of the line source, and e is in the range ofA constant.

In this embodiment, the longitudinal direction of the line source is defaulted to the central axis direction of the elbow, and the transverse direction is defaulted to the direction perpendicular to the central axis direction of the elbow.

The phase distribution of the plane wave reaching the second parallel plate waveguide can be preliminarily adjusted by adjusting the phase center position of the cylindrical wave excited by the H-plane horn and the value of e.

Furthermore, an upper and a lower symmetrical first matching steps are arranged at the contact position of the first arc-shaped elbow and the first parallel plate waveguide and the second parallel plate waveguide, and are used for realizing the turning of the plane wave propagation direction. The first matching step is a rectangular step or a triangular step with a certain radian. The first matching step may turn the direction of plane wave propagation through the first parallel-plate waveguide by 180 degrees into the second parallel-plate waveguide.

Furthermore, the second arc-shaped elbow is of a C-shaped cavity structure, the inner wall of the cavity is made of metal materials, and the C-shaped opening faces the inner side of the line source structure and is used for changing the transmission direction and phase distribution of electromagnetic waves in the waveguide. The transverse rotation radian of the second arc-shaped elbow meets the following formula:

X²4fY, wherein: f is a value range ofIs constant.

Furthermore, an upper and a lower symmetrical second matching steps are arranged at the contact position of the second arc-shaped elbow and the second parallel plate waveguide and the third parallel plate waveguide, and are used for realizing the turning of the plane wave propagation direction. The second matching step is a rectangular step or a triangular step with a certain radian. The second matching step may turn the propagation direction of the plane wave passing through the second parallel-plate waveguide by 180 degrees, and enter the third parallel-plate waveguide. By adjusting the longitudinal relative positions of the first arc-shaped elbow and the second arc-shaped elbow and the value of f, the phase distribution of the plane wave reaching the third parallel plate waveguide can be adjusted.

Further, the third elbow is an L-shaped elbow, and the rotation radian of the third elbow in the transverse direction is a straight line. The L-shaped elbow is composed of an L-shaped corner and a third matching step. The third matching step is a rectangular step or a triangular step with a certain radian.

Furthermore, the output port of the third parallel plate waveguide is arranged right above the third parallel plate waveguide, and is used for connecting a parallel feed, a series feed network or a radiation structure such as a CTS antenna and the like which need a plane wave feed antenna, and directly radiating electromagnetic waves.

Further, the first parallel plate waveguide, the second parallel plate waveguide and the third parallel plate waveguide are separated by a metal thin plate. The upper, lower and side walls of the first, second and third parallel plate waveguides are made of metal conductors, and wave-absorbing materials are attached to the side walls.

Further, the first parallel plate waveguide, the second parallel plate waveguide and the third parallel plate waveguide may be replaced by a substrate integrated waveguide.

Further, the central axes of the first arc-shaped elbow and the second arc-shaped elbow are overlapped.

The invention also provides an antenna comprising a broadband line source based on multilayer parallel plate waveguides according to any of the forms described above.

Compared with the prior art, the invention has the following advantages and beneficial effects:

1. the antenna is simple in design, low in section and easy to process, and can effectively reduce the overall longitudinal size of a line source under the condition of large-caliber transverse output, so that the overall size of the large-caliber array antenna can be further reduced.

2. The parallel plate waveguide is used as the main structure of the line source, and the line source has the characteristic of wide band, so the feed source can be widely used for the wide band array antenna.

3. The output amplitude distribution of the line source is in cosine function distribution, and when the line source is used for an array antenna feed source, the performance requirement of low side lobes can be met.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.

FIG. 1 is a perspective schematic view of a broadband line source according to an embodiment of the present invention;

FIG. 2 is a schematic side sectional view of a broadband line source according to an embodiment of the present invention;

FIG. 3 is a schematic cross-sectional view of a first layer of parallel plate waveguides of a broadband line source according to an embodiment of the present invention;

FIG. 4 is a schematic cross-sectional view of a second layer of parallel plate waveguides of a broadband line source according to an embodiment of the present invention;

FIG. 5 is a schematic cross-sectional view of a third layer of parallel plate waveguides of a broadband line source according to an embodiment of the present invention;

FIG. 6 is a graph of an electric field magnitude simulation for a first layer of parallel plate waveguides of a broadband line source according to an embodiment of the present invention;

FIG. 7 is a graph of an electric field magnitude simulation for a second layer of parallel plate waveguides of a broadband line source according to an embodiment of the present invention;

FIG. 8 is a graph showing the simulation of the electric field amplitude of the third layer of parallel plate waveguides of the broadband line source according to the embodiment of the present invention;

FIG. 9 is a graph of a broadband source input port Voltage Standing Wave Ratio (VSWR) simulation provided by an embodiment of the present invention;

FIG. 10 is a graph illustrating normalized amplitude distribution at an output port of a broadband line source provided by an embodiment of the present invention at a frequency of 30 GHz;

FIG. 11 is a graph illustrating normalized phase distribution at an output port of a broadband line source provided by an embodiment of the present invention at a frequency of 30 GHz;

FIG. 12 is a schematic perspective view of a broadband line source according to another embodiment of the present invention;

FIG. 13 is a schematic side sectional view of another embodiment of a broadband line source according to the present invention;

FIG. 14 is a schematic perspective view of a broadband line source according to another embodiment of the present invention;

figure 15 is a schematic side sectional view of another embodiment of a broadband line source according to the present invention;

FIG. 16 is a schematic cross-sectional view of a first layer of parallel plate waveguides of a broadband line source according to another embodiment of the present invention;

FIG. 17 is a schematic cross-sectional view of a second layer of parallel plate waveguides of a broadband line source according to another embodiment of the present invention;

figure 18 is a schematic cross-sectional view of a third layer of parallel plate waveguides of a broadband line source according to another embodiment of the present invention.

The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the 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.

It should be noted that, if directional indications (such as up, down, left, right, front, and back … …) are involved in the embodiment of the present invention, the directional indications are only used to explain the relative positional relationship between the components, the movement situation, and the like in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indications are changed accordingly.

In addition, if there is a description of "first", "second", etc. in an embodiment of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.

As shown in fig. 1-2, the broadband line source according to the embodiment of the present invention mainly includes three first parallel plate waveguides 6, second parallel plate waveguides 7, and third parallel plate waveguides 8, which are sequentially stacked, where the first parallel plate waveguides 6 and the second parallel plate waveguides 7 are connected by a first arc-shaped bend 3, the second parallel plate waveguides 7 and the third parallel plate waveguides 8 are connected by a second arc-shaped bend 4, an input port of the first parallel plate waveguide 6 is connected to the H-plane horn 2, and an output port of the third parallel plate waveguide 8 is connected to a third bend 5. The line source is of a broadband structure, the longitudinal size of the line source can be effectively reduced while the transverse output range can be enlarged, the plane waves with uniformly distributed phases and cosine function distribution amplitudes are obtained on a one-dimensional plane, and therefore the size and the processing difficulty of the large-caliber array antenna are effectively reduced.

By adjusting the longitudinal position of the H-plane horn 2 and the phase center of the cylindrical wave, the rotational radians of the first arc-shaped elbow 3 and the second arc-shaped elbow 4 are adjusted, so that the cylindrical wave generated by the H-plane horn 2 passes through the first parallel plate waveguide 6, the first arc-shaped elbow 3, the second parallel plate waveguide 7 and the second arc-shaped elbow 4, and after the third parallel plate waveguide 8 and the third elbow 5, a plane wave with equal phase and amplitude distributed along the transverse direction in a cosine function can be obtained. This example adopts external rectangular waveguide 1 to carry out the feed, and the overall profile is the metal cuboid, and inside fretwork part is parallel plate waveguide cavity structure. Electromagnetic waves are fed in through the rectangular waveguide port on the side face, pass through the parallel plate waveguide cavity structure and are output from the parallel plate waveguide port on the top face. The input electromagnetic wave mode is a TE10 mode of a standard rectangular waveguide, the output electromagnetic wave mode is a quasi-TEM mode of a parallel plate waveguide, the electric field amplitude of the output quasi-TEM mode in the transverse direction of the whole structure is in cosine distribution, and the electric field phase is in equiphase distribution.

As shown in fig. 2, the parallel plate waveguide cavity is mainly composed of an input port rectangular waveguide 1, an H-plane horn 2, a first parallel plate waveguide 6, a second parallel plate waveguide 7, a third parallel plate waveguide 8, a first arc-shaped bend 3, a second arc-shaped bend 4, and a third bend 5 when viewed from the side. Wherein the ports of the rectangular waveguide 1 are located at the lateral broadside sides of the line source and the output ports are located at the top surface of the line source. The rectangular waveguide 1 and the H-plane horn 2 have the same horizontal height as a first parallel plate waveguide 6, a second parallel plate waveguide 7 and a third parallel plate waveguide 8, wherein the first parallel plate waveguide 6, the second parallel plate waveguide 7 and the third parallel plate waveguide 8 are arranged in parallel, the first parallel plate waveguide 6 and the second parallel plate waveguide 7 are separated by a metal thin plate in the vertical direction, and the second parallel plate waveguide 7 and the third parallel plate waveguide 8 are separated by a metal thin plate in the vertical direction. One end of the first parallel plate waveguide 6 is connected with a cylindrical wave feed source of the H-plane horn 2; the other end of the first parallel plate waveguide 6 is connected with one end of the second parallel plate waveguide 7 through a first arc-shaped elbow 3, two triangular first matching steps 11 are arranged on the upper surface and the lower surface of the first arc-shaped elbow 3, and the plane wave fed in by the first parallel plate waveguide 6 passes through the first arc-shaped elbow 3, turns to 180 degrees in the propagation direction and reaches the second parallel plate waveguide 7; the other end of the second parallel plate waveguide 7 is connected with one end of the third parallel plate waveguide 8 through a second arc-shaped elbow 4, two triangular second matching steps 12 are arranged on the upper surface and the lower surface of the second arc-shaped elbow 4, and the plane wave fed in from the second parallel plate waveguide 7 passes through the second arc-shaped elbow 4, the propagation direction of the plane wave is turned by 180 degrees and reaches the third parallel plate waveguide 8; the third parallel plate waveguide 8 is connected to the output port through the third bend 5, and the plane wave fed from the third parallel plate waveguide 8 passes through the third bend 5, and the propagation direction of the plane wave is turned by 90 degrees to reach the output port.

Specifically, the first curved elbow 3 and the second curved elbow 4 are C-shaped cavity structures (which may also be referred to as C-shaped elbows). Wherein:

the transverse rotation radian of the first arc-shaped elbow 3 meets the formulaWherein:a is half of the overall transverse dimension D1 of the line source, and e is in the range ofA constant. In this embodiment, the longitudinal direction of the line source is defaulted to the central axis direction of the elbow, and the transverse direction is defaulted to the direction perpendicular to the central axis direction of the elbow.

The transverse rotation radian of the second arc-shaped elbow 4 meets the formula X²4fY, wherein: f is a value range ofIs constant. The parameters obtained by self-taking in the embodiment are optimized, so that a better transmission effect and a required output plane wave can be obtained.

As shown in fig. 3 to 5, the first parallel-plate waveguide 6 shown in the example connects the H-plane horn 2 and the first curved elbow 3. The rectangular waveguide 1 of the input end is a standard type rectangular waveguide, the external standard wave is connected with a conversion device, the rectangular waveguide 1 is placed along the central axis of a line source, the wide side of the rectangular waveguide 1 is connected with an upper parallel plate and a lower parallel plate, the distance between the two parallel plates is the width of the narrow side of the rectangular waveguide, and the excitation signal of the rectangular waveguide is in a TE10 mode. The H-plane Bragg grating 2 consists of two inclined planes 9 and two planes 10, wherein the inclined planes are in the direction of an electric field, the planes are in the direction of a magnetic field, and the planes are in contact with the upper surface and the lower surface of the parallel plate waveguide. Loudspeaker are placed along the whole horizontal axis of structure, loudspeaker's input port connection rectangular wave 1's output port, loudspeaker's opening direction is first arc elbow 3, the cylindrical wave of loudspeaker's output port radiation play, along the horizontal axis symmetric distribution of overall structure, loudspeaker's E face height and rectangular waveguide 1's broadside highly uniform, loudspeaker opening size is greater than lambda (the waveguide wavelength of the highest frequency transmission electromagnetic wave), output beam width can be adjusted through adjusting loudspeaker's opening size, loudspeaker inclined plane's shape can be pyramid type or exponential law gradual change type, be exponential law gradual change type in this example.

As shown in figures 1 to 5, the H-plane horn and the first arc-shaped elbow are not directly connected, the transverse dimension D2 of the first arc-shaped elbow is equal to the overall transverse dimension D1 of a line source, the amplitude distribution of the output plane wave obtained by the structure is steeper, the suppression effect of the side lobe level is better, and simulation shows that the suppression of the side lobe level by the structure can generally reach below-30 dB. The overall transverse dimension D1 of the line source and the transverse dimension D2 of the first arcuate bend are shown in figure 14.

As shown in fig. 14 to 18, in another example, the H-plane horn is directly connected to the first curved elbow, and the transverse dimension D2 of the first curved elbow is smaller than the overall transverse dimension D1 of the line source, so that the structure has higher caliber efficiency, and simulation shows that the structure can generally achieve more than 85% of caliber efficiency. The overall transverse dimension D1 of the line source and the transverse dimension D2 of the first arcuate bend are shown in figure 14.

The second parallel-plate waveguide 7 shown in this example connects the first curved bend 3 and the second curved bend 4. The third parallel plate waveguide 8 shown in the example connects the second curved bend 4 and the third bend (which is an L-shaped bend). In the example, the upper, lower and side walls 15 of the first parallel plate waveguide 6, the second parallel plate waveguide 7 and the third parallel plate waveguide 8 are all made of good metal conductors, and wave-absorbing materials are attached to the side walls.

As shown in fig. 6-11, the broadband line source of the present invention was simulated using commercial simulation software. The simulation graph of the electric field amplitude of the first parallel plate waveguide is shown in fig. 6, the simulation graph of the electric field amplitude of the second parallel plate waveguide is shown in fig. 7, and the simulation graph of the electric field amplitude of the third parallel plate waveguide is shown in fig. 8. As can be seen from fig. 6 to 8, the cylindrical wave is excited at the input port, and the third parallel wave is guided to be a plane wave whose amplitude distribution is cosine distribution or equal phase distribution. The simulation graph of the input port voltage standing wave ratio of the broadband line source of the invention at 15GHz to 35GHZ is shown in FIG. 9. The normalized amplitude curve diagram of the output port at the frequency point of 30GHz is shown in FIG. 10. The normalized phase curve of the output port at the frequency point of 30GHz is shown in fig. 11. As can be seen from the analysis of FIG. 9, the voltage standing wave ratio of the present invention is lower than 1.2 in the whole frequency band from 20GHz to 35GHz, and the present invention has a broadband characteristic. As can be seen from the analysis of FIG. 10, the amplitude distribution of the present invention at the frequency point of 30GHz shows an uneven distribution, which is similar to a cosine distribution. As can be seen from the analysis of FIG. 10, the phase distribution of the present invention shows equal phase distribution at the frequency point of 30GHz, which is similar to an ideal plane wave.

Based on the above principle, the invention can also increase the number of layers (more than three layers) of the parallel plate waveguide as required, as shown in fig. 12 and 13, the parallel plate waveguide can be designed into a five-layer structure, the principle of which is similar to the structure described above, so as to solve the problems of line source miniaturization, broadband and output amplitude distribution during large-caliber feeding, and further description is omitted. The parallel plate waveguides can be arranged into any multiple layers according to the size of a line source structure, wherein the bottom layer is input layer waveguides, the top layer is output layer waveguides, the middle layer is transmission layer waveguides, and two adjacent layers of parallel plate waveguides are connected through arc-shaped elbows. Assuming that the number of the arc bends is N (N is more than or equal to 2), the parallel plate waveguide is N +1 layers. The curvatures of all points of the arc where the arc-shaped elbow is located can be the same or different, and are specifically set according to parameters of the plane wave output by the line source, and are not described one by one. When the structure of the line source is designed, the parallel plate waveguides with different layers can be selected according to the requirements of the structure and the size of the line source. By controlling the number of layers of the parallel plate waveguide, the width-to-length ratio of the whole line source can be flexibly adjusted, and the units of the expansion part are the same, so that the design difficulty of the antenna is reduced.

The above are specific embodiments of the present invention, and those skilled in the art can make the broadband line source of the present embodiment by applying the method disclosed in the present invention and some alternative ways without creative efforts. The linear source is suitable for being used as a line source of a large-caliber broadband array antenna.

The above-mentioned embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above-mentioned embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.