A self-torquing waveguide circular polarized antenna

Abstract

The application discloses a self-twisted waveguide circularly polarized antenna, which comprises an input waveguide section, a self-twisted waveguide section and a radiation opening section arranged along the electromagnetic wave propagation direction, the input waveguide section is used for feeding linearly polarized electromagnetic waves, the symmetry cross-section profile of the self-twisted waveguide section continuously rotates along the electromagnetic wave propagation direction, the local electromagnetic boundary direction of the waveguide inner cavity continuously changes with the propagation position, so that the input linearly polarized electromagnetic waves form two orthogonal field components in the propagation process, and the two orthogonal field components gradually form the amplitude relationship and the phase relationship meeting the circular polarization condition; the radiation opening section is used for radiating the electromagnetic waves regulated by the self-twisted waveguide section to the free space. The application realizes polarization regulation and circularly polarized radiation by continuously twisting the waveguide body in space, can reduce the dependence on independent polarization conversion components or external phase shift structures, reduces transmission discontinuity and local reflection, and improves the structural integration degree, processing consistency and engineering reliability.

Description

Technical Field

[0001] This invention belongs to the field of microwave antennas and waveguide transmission, and particularly relates to a self-twisting waveguide circularly polarized antenna. Background Technology

[0002] Circularly polarized antennas can reduce polarization mismatch caused by relative attitude changes between transmitting and receiving antennas, and have certain advantages in suppressing the effects of multipath propagation and improving communication stability in complex propagation environments. Therefore, they are widely used in satellite communication, radar detection, remote sensing measurement, navigation and positioning, and microwave testing. For microwave systems with high requirements for power capacity, transmission efficiency, and environmental adaptability, waveguide structures are often used as the feeding and radiating structures for circularly polarized antennas due to their low conductor loss, high power carrying capacity, and stable mechanical structure. The formation of circularly polarized electromagnetic waves usually requires obtaining two spatially orthogonal electromagnetic field components with similar amplitudes and a phase difference of approximately 90°. Therefore, how to stably establish the above amplitude-phase relationship during waveguide transmission is a key issue in the design of waveguide circularly polarized antennas.

[0003] Existing waveguide circular polarization structures typically employ dielectric polarization plates, metal spacers, ridge structures, orthogonal mode conversion structures, or specialized waveguide phase difference structures to achieve polarization conversion. For example, loading structures with different electromagnetic boundary characteristics can be placed inside the waveguide to give the two orthogonal field components different propagation constants, and the required phase difference can be formed by accumulating over a certain propagation length. Such structures can achieve conversion between linear and circular polarization, but their polarization control function usually depends on the functional structures added inside the waveguide. Different functional structures can easily create new electromagnetic boundary changes with the original waveguide, and their dimensional errors, positional errors, and assembly conditions can all change the amplitude and phase relationship of the two orthogonal field components. Especially as the operating frequency increases and the waveguide size decreases, even small structural deviations can cause significant phase shifts, mode perturbations, or impedance changes, thereby increasing the difficulty of fabrication and debugging, and affecting the consistency between different antenna elements.

[0004] To reduce reflection loss caused by abrupt changes in polarization, patent application CN120221953A proposes a polarization conversion structure with non-axisymmetric gradient ripples on the inner wall of a cylindrical waveguide. This type of structure creates different transverse boundary constraints on two orthogonal field components by continuously or piecewise varying geometric parameters such as ripple depth, tilt, and equivalent radius along the propagation direction, resulting in different propagation constants. The relative phase delay accumulates with the propagation distance, and the conversion between linear and circular polarization is achieved when the phase difference reaches a predetermined value. Compared to stepped abrupt polarization structures, this type of gradient structure can improve transmission continuity and impedance matching performance to some extent. However, its polarization conversion mechanism still mainly relies on specific asymmetric ripples or similar local boundary control structures set on the inner wall of the basic waveguide transmission channel. Polarization performance is affected by multiple local structural parameters such as ripple depth, period, tilt angle, curvature, and gradient law, requiring high processing precision under high-frequency conditions. In addition, this type of structure usually completes the polarization conversion inside the waveguide first, and then delivers the converted circularly polarized guided wave to the subsequent radiation structure. Its polarization conversion process and the conversion process from the guided wave state to the free space radiation state are still functionally separated.

[0005] For applications requiring the construction of phased array antenna units or highly integrated microwave radiating units, the aforementioned functional separation may necessitate separate mode matching and impedance matching between the polarization conversion structure, transmission structure, and radiating structure, with the electromagnetic states of each structure influencing each other. When multiple functional segments are connected in series, not only does the overall axial dimension increase, but any deviation in structural parameters can affect the final axial ratio, port reflection, and radiation pattern through cascading. Therefore, existing technologies still need to further address the following issues: how to reduce dependence on independent polarization conversion components or locally functional loading structures while ensuring that linearly polarized guided waves form a stable orthogonal field component amplitude-phase relationship during propagation, and how to enable a more continuous electromagnetic transition between this polarization evolution process and the subsequent radiation process, thereby balancing circular polarization performance, impedance matching, structural integration, and fabrication consistency. Summary of the Invention

[0006] The main technical problem that this invention aims to solve is that existing waveguide circularly polarized antennas rely on independent polarization conversion structures or local boundary loading structures to achieve amplitude and phase modulation of orthogonal field components, resulting in the relative separation of polarization conversion and radiation processes, complex structures, and difficulty in ensuring fabrication consistency.

[0007] Therefore, the present invention provides a self-twisting waveguide circularly polarized antenna, which includes an input waveguide section, a self-twisting waveguide section and a radiating opening section that are sequentially connected along the electromagnetic wave propagation direction; The input waveguide section is used to feed linearly polarized electromagnetic waves. The self-twisting waveguide section has a non-discontinuous rotationally symmetric waveguide cavity cross section. The overall spatial orientation of the cavity cross section changes continuously or segmentally around the propagation axis along the electromagnetic wave propagation direction, so that the direction of the local electromagnetic boundary of the waveguide cavity changes with the propagation position. This allows the linearly polarized electromagnetic wave to gradually couple and form two orthogonal field components during propagation within the self-twisting waveguide section, and the two orthogonal field components form an amplitude and phase relationship that satisfies the circular polarization radiation condition at the output end of the self-twisting waveguide section. The radiating opening section is connected to the output end of the self-twisting waveguide section, and is used to radiate the electromagnetic waves after being modulated by the self-twisting waveguide section into free space.

[0008] Furthermore, the input waveguide section is used to connect to the rectangular waveguide feed port; the radiating opening section is an open waveguide structure, and the waveguide cavity of the radiating opening section is continuously connected to the waveguide cavity on the output side of the self-twisting waveguide section, so that the electromagnetic wave after being regulated by the self-twisting waveguide section transitions from the guided wave state to the free space radiation state.

[0009] Preferably, the waveguide cavity cross-section of the self-twisting waveguide section is rectangular, and the wide side and narrow side of the rectangular cross-section rotate sequentially around the propagation axis as the electromagnetic wave propagation position changes.

[0010] Preferably, the self-twisting waveguide section is a continuous helical torsion structure, and the overall profile of the waveguide cavity cross section rotates continuously and smoothly around the propagation axis along the electromagnetic wave propagation direction.

[0011] In one embodiment, the self-twisting waveguide segment includes a plurality of waveguide sub-segments connected sequentially along the electromagnetic wave propagation direction. Each waveguide sub-segment has a non-discontinuous rotationally symmetric waveguide cavity cross-section, and the waveguide cavity cross-sections of adjacent waveguide sub-segments have a preset angle difference around the propagation axis to form a segmented torsion structure.

[0012] Furthermore, the self-twisting waveguide segment is positioned in the axial direction. The actual cross-section at the location satisfy:

[0013] in, Indicates axial position The reference cross section when no torsion occurs. Indicates rotation around the direction of electromagnetic wave propagation The corresponding rotation transformation, Indicates axial position The torsion angle of the waveguide cavity cross-section; the torsion angle It changes linearly or nonlinearly along the direction of electromagnetic wave propagation.

[0014] Preferably, the total torsion angle of the self-torsion waveguide section is 360°, and the torsion direction of the self-torsion waveguide section is used to determine the rotation direction of the circularly polarized electromagnetic wave.

[0015] Furthermore, the input waveguide section, the self-twisting waveguide section, and the radiating opening section all have conductive metal walls, and the input waveguide section, the self-twisting waveguide section, and the radiating opening section are formed as an integrally molded metal structure.

[0016] Preferably, the rectangular cross-sectional dimensions of the self-torsional waveguide section are 20×40mm, and the axial length is 200mm.

[0017] Preferably, the self-twisting waveguide circularly polarized antenna operates in the frequency band of 10.2~10.7GHz. Within this frequency band, the port reflection coefficient of the self-twisting waveguide circularly polarized antenna is less than -15dB, and the axial ratio of the main radiation direction is less than 3dB.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects: This invention achieves polarization conversion by causing the cross-sectional profile of a waveguide, which lacks continuous rotational symmetry, to undergo continuous or segmented spatial twisting along the electromagnetic wave propagation direction. This results in the local electromagnetic boundary direction within the waveguide cavity changing with the propagation position, thereby enabling the input linearly polarized electromagnetic wave to continuously couple orthogonal field components and undergo amplitude and phase evolution during propagation, ultimately forming a field distribution that satisfies the circular polarization condition at the radiating end. Compared to existing solutions that rely on dielectric polarization plates, metal partitions, ridge structures, corrugated loading structures, or independent phase-shifting structures to achieve polarization conversion, this invention directly integrates the polarization control function into the spatial configuration of the waveguide body. It eliminates the need for additional independent polarization conversion components or dedicated local boundary loading structures within the basic waveguide transmission channel, thereby reducing electromagnetic boundary discontinuities, local reflections, and assembly errors caused by additional structures. This improves the continuity of the waveguide transmission process and the integration of the antenna structure.

[0019] This invention does not rely on an independent polarization control structure located in a local area within the waveguide to achieve circular polarization radiation. Instead, it utilizes the continuous or segmented rotation of the waveguide cross-section along the electromagnetic wave propagation direction to cause the electromagnetic field within the waveguide to gradually undergo mode coupling and phase evolution with the propagation distance. By coordinating the design of structural parameters such as the total twist angle, twist direction, axial length, the variation law of the twist angle along the axial direction, and cross-sectional dimensions of the self-twisting waveguide section, the amplitude and phase relationship of different orthogonal field components during propagation can be controlled, resulting in an electric field distribution that satisfies the conditions for circular polarization radiation at the radiation opening. Therefore, while achieving circular polarization radiation, antenna performance such as port impedance matching, operating bandwidth, and radiation pattern can also be coordinating for design, thereby reducing the sensitivity of antenna polarization performance to the dimensions and manufacturing errors of the local polarization control structure.

[0020] This invention continuously connects the self-twisting waveguide section and the radiating aperture section, allowing the input linearly polarized electromagnetic wave to gradually evolve its electromagnetic field state during propagation within the self-twisting waveguide section. Near the radiating aperture, an orthogonal field component satisfying the circular polarization radiation condition is formed, which then radiates directly into free space from the radiating aperture. Thus, the polarization evolution process of the electromagnetic field within the waveguide and the radiation process of the guided wave into free space are continuously connected within the same waveguide structure. Compared to a cascaded structure that uses independent polarizers to first polarize the guided wave and then achieves spatial radiation through subsequent radiating structures, this invention reduces the additional connections and matching links between independent polarizers and their subsequent radiating structures. This simplifies the overall antenna structure and reduces the impact of interface and assembly errors between different functional structures on antenna performance. For applications such as phased arrays composed of a large number of repetitive antenna elements, integrating polarization state control, waveguide transmission, and radiation functions into the same self-twisting waveguide structure further reduces the number of independent functional components and assembly steps between elements, improving the consistency of the array element structure and the convenience of engineering implementation. Attached Figure Description

[0021] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0022] Figure 1 This is a schematic diagram of the structure of a self-twisting waveguide circularly polarized antenna provided in an embodiment of the present invention; Figure 2 This is a top view schematic diagram of a self-twisting waveguide circularly polarized antenna provided in an embodiment of the present invention; Figure 3 This is a side view schematic diagram of a self-twisting waveguide circularly polarized antenna provided in an embodiment of the present invention; Figure 4 An axial ratio curve of an antenna provided according to an embodiment of the present invention; Figure 5 A differential reflection coefficient curve of an antenna provided in an embodiment of the present invention; Figure 6 The radiation pattern of an antenna at 10.4 GHz with Phi=0° is provided in an embodiment of the present invention. Figure 7 The radiation pattern of the antenna at 10.4 GHz with Phi=90° is provided in an embodiment of the present invention.

[0023] The reference numerals in the attached figures are as follows: 11-input waveguide section, 12-self-torsional waveguide section, 13-radiation aperture section. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative effort are all within the scope of protection of the present invention.

[0025] This embodiment provides a self-twisting waveguide circularly polarized antenna, used to gradually modulate an input linearly polarized electromagnetic wave into an electromagnetic field that satisfies the conditions for circular polarization radiation during waveguide propagation, and then directly radiates the polarization-modulated electromagnetic wave into free space. Figures 1-3 As shown, the self-twisting waveguide circularly polarized antenna includes an input waveguide section 11, a self-twisting waveguide section 12, and a radiating aperture section 13, which are arranged sequentially and interconnected along the electromagnetic wave propagation direction. The input waveguide section is used to connect to an external feed port and input linearly polarized electromagnetic waves into the self-twisting waveguide section. The self-twisting waveguide section is used to continuously control the spatial distribution and phase state of the electromagnetic field while the electromagnetic wave propagates axially. The radiating aperture section is used to propagate the electromagnetic wave, after being controlled by the self-twisting waveguide section, into free space.

[0026] Assuming the direction of electromagnetic wave propagation is taken as the Z-direction of the spatial coordinate system, the self-torsional waveguide segment extends along the Z-direction, with its central axis essentially aligned with the Z-direction. Unlike adding polarization plates, septa, ridges, corrugations, or other locally loaded structures within a fixed waveguide, this embodiment directly causes the cross-section of the waveguide cavity constituting the waveguide channel to continuously change its spatial orientation along the Z-direction. In other words, the self-torsional waveguide segment possesses a discontinuous rotationally symmetric cross-section for confining the electromagnetic field at different axial positions, and this discontinuous rotationally symmetric cross-section continuously rotates around its central axis as the axial position changes, thereby causing the local electromagnetic boundary direction of the waveguide cavity to continuously change with the propagation position.

[0027] For ease of explanation, the reference cross-section at any axial position z of the self-torsional waveguide segment without spatial rotation can be denoted as... The actual cross-section at this axial position is denoted as Both conditions are met:

[0028] In the formula, Indicates the position coordinates along the direction of electromagnetic wave propagation. Indicates axial position The reference cross section at that location, Indicates rotation about the waveguide propagation axis The corresponding spatial rotation transformation, Indicates axial position The torsion angle of the cross section relative to the reference orientation of the input end. This represents the actual waveguide cross-section formed after the aforementioned rotation. By changing... Follow The variation of the angle of twist can alter the local torsion ratio of the waveguide along the propagation direction. The total torsion angle and axial length together determine the average torsion ratio, while the torsion angle function determines the axial distribution of the torsion ratio.

[0029] In terms of structural implementation, the self-torsional waveguide section in this embodiment adopts a continuous helical torsion structure. That is, the cross-section of the non-discontinuous rotationally symmetric waveguide cavity extending along the propagation direction of the electromagnetic wave continuously and smoothly changes its spatial orientation around the propagation axis, so that there is no obvious abrupt change in orientation between the waveguide cross-sections at adjacent axial positions. This is beneficial to allow the electromagnetic field to be continuously controlled by changing boundary conditions during propagation, reducing the reflection and undesirable mode excitation that may be caused by local structural abrupt changes, and allowing the coupling and phase evolution process of orthogonal field components to proceed continuously along the propagation direction.

[0030] In some embodiments, the self-torsional waveguide segment can also be composed of multiple waveguide sub-segments connected sequentially along the electromagnetic wave propagation direction. Each waveguide sub-segment has a non-continuous rotationally symmetric waveguide cavity cross-section, and the cross-sections of adjacent waveguide sub-segments have a preset angle difference around the propagation axis, causing the cross-sectional orientation of each waveguide sub-segment to change sequentially along the propagation direction, thereby forming an approximately continuous segmented torsion structure. By reasonably reducing the preset angle difference between adjacent waveguide sub-segments and increasing the number of waveguide sub-segments, the segmented torsion structure can be made to approximate a continuous torsion structure in terms of electromagnetic propagation effect, so that the input linearly polarized electromagnetic wave gradually undergoes orthogonal field component coupling and phase evolution as it passes through each waveguide sub-segment sequentially. Therefore, both continuous helical torsion and segmented torsion belong to the structural forms that utilize the overall spatial orientation of the waveguide cross-section to change along the propagation direction to achieve polarization control. The main difference lies in whether the cross-sectional orientation changes continuously or segmentally along the axial direction.

[0031] This embodiment preferably employs a continuous torsion form with a uniform cross-section. That is, the rectangular inner cavity at different axial positions of the torsion waveguide segment has a corresponding rectangular profile, with the main variation manifested in the continuous change of the spatial orientation of the rectangular cross-section around the propagation axis. Thus, the wide and narrow sides of the rectangular waveguide no longer remain fixed throughout the propagation path, but rotate continuously as the electromagnetic wave propagates forward. This overall cross-section torsion method avoids the need to rely on local functional structures set on the fixed inner wall of the waveguide to achieve polarization control. The waveguide boundary itself, used for transmitting electromagnetic waves, simultaneously becomes the structural basis for continuous control of the electromagnetic field.

[0032] In a specific dimension example, the rectangular cross-section of the self-torsional waveguide section can be set to 20×40mm, with an axial length of... The diameter is set to 200 mm, and the total twist angle is set to 360°. The rectangular cross-section begins at the input end of the self-twisted waveguide section and gradually changes orientation along the propagation direction until its output end completes a cumulative 360° spatial rotation relative to the input end. The twist direction can be set clockwise; however, when a polarization output with a different rotation direction is required, the self-twisting direction can be changed according to the target circular polarization rotation direction. For example, under the condition that other structural parameters are basically the same, changing the clockwise twist along the propagation direction to a counterclockwise twist can change the spatial coupling direction and phase evolution direction of the electromagnetic field during propagation, thereby obtaining circular polarization radiation with the opposite rotation direction.

[0033] The average torsion rate of the aforementioned 200mm long self-torsion waveguide segment with a total torsion angle of 360° can be expressed as:

[0034] In the formula, Indicates the average torsion rate. This represents the total twist angle of the self-torsional waveguide segment. This indicates its axial length. In this embodiment, the local torsional rate is not required to be constant over the entire axial length. Based on indicators such as the target operating frequency, shaft ratio, reflection coefficient, and radiation pattern, it can be... The change can be made linearly or nonlinearly, allowing different axial positions to correspond to different local torsional rates. This allows for adjustment of the speed at which the electromagnetic field evolves from the input state to the output state, ensuring that polarization control is not concentrated at a single cross-section or a localized loaded component, but rather distributed throughout the propagation path of the self-torsional waveguide segment.

[0035] The circular polarization formation process described in this embodiment is as follows: Linearly polarized electromagnetic waves first enter the self-twisting waveguide section from the input waveguide section. Near the input end, the electromagnetic field is mainly constrained by the rectangular waveguide boundary at the input end. As the electromagnetic wave propagates along the Z-direction, the spatial orientation of the rectangular cavity begins to change. Therefore, the principal direction of the local cross-section faced by the electromagnetic wave at the next axial position has rotated by a certain angle relative to the previous position. For non-continuous rotationally symmetric waveguides such as rectangles, different transverse directions have different boundary constraint conditions. Therefore, when the principal direction of the local cross-section rotates continuously, the original linearly polarized electromagnetic field is re-decomposed and coupled relative to the new local boundary direction. This process occurs continuously as the propagation distance increases. That is to say, the electromagnetic wave is not only decomposed into two orthogonal components at a certain local structure, but under the action of continuously rotating waveguide boundary conditions, the components of its electric field in the two local orthogonal directions continuously couple, and generate corresponding amplitude evolution and phase evolution during propagation. When the electromagnetic field state formed at the previous axial position continues to enter the next slightly rotated waveguide cross-section, it is further constrained by new local boundaries, thus forming a continuous and distributed polarization control process along the entire self-twisting waveguide section.

[0036] By selecting the length, width, and axial length of the rectangular cross-section Total torsion angle as well as The variation law allows the two orthogonal field components to reach a state suitable for circular polarization at the end of the self-twisting waveguide section, meaning the amplitudes of the two orthogonal field components are basically equal and their phase difference is close to 90°. At this point, after the two orthogonal field components are superimposed, the resulting electric field vector rotates with time, thus forming a circularly polarized electromagnetic field. Therefore, this embodiment does not establish a fixed phase difference region inside the waveguide to make the two fixed-direction field components accumulate a 90° phase difference solely based on the difference in propagation constants. Instead, it utilizes the continuous field coupling and phase evolution formed by the continuous axial rotation of the entire discontinuous rotationally symmetric transmission boundary to establish the polarization state. This allows the polarization control function to be directly integrated into the spatial morphology of the waveguide body.

[0037] It should be noted that circular polarization performance depends not only on whether a phase difference of approximately 90° is ultimately achieved, but also on the amplitude relationship between the two orthogonal field components. Therefore, the design of the self-torsional waveguide section is not simply about adjusting a single phase parameter, but rather involves the total torsion angle, torsion rate distribution, axial length, and rectangular cross-sectional dimensions all participating in electromagnetic field modulation. For example, if the torsion velocity in a local region is too high, it may lead to excessively drastic changes in the local mode and cause reflections; conversely, if the torsion velocity is too low, the desired polarization state may require a longer propagation distance to form. Therefore, full-wave electromagnetic simulation can be used to... , The cross-sectional dimensions are jointly optimized to simultaneously meet requirements such as input matching, circular polarization axial ratio, and far-field radiation pattern. This joint optimization is a conventional technique in microwave antenna and waveguide device design. Those skilled in the art can determine the corresponding parameter combinations based on performance indicators such as the target operating frequency band, port reflection coefficient, axial ratio, and radiation pattern using existing mature full-wave electromagnetic simulation and parameter scanning methods. This embodiment will not elaborate further.

[0038] The output end of the self-twisting waveguide section is continuously connected to the radiating aperture section. The radiating aperture section is mainly used to further couple the circularly polarized electromagnetic field, which has been gradually established within the self-twisting waveguide section, into free space. Since the polarization state is gradually formed during waveguide propagation, a relatively continuous electromagnetic state transition can be achieved from the self-twisting waveguide section to the radiating aperture section. The radiating aperture section can adopt an open waveguide structure, with its internal cavity connected to the internal cavity at the end of the self-twisting waveguide section. This allows the two orthogonal field components formed at the end of the self-twisting waveguide section to maintain their corresponding amplitude-phase relationship and radiate into free space. In specific size design, the size of the radiating aperture can be matched and optimized as needed to minimize the disturbance of the radiating aperture to the propagation mode inside the waveguide, while also considering the main beam direction, gain, and impedance matching. Thus, the self-twisting waveguide section is not only used as a polarization converter in the traditional sense, but together with the radiating aperture, it constitutes a continuous circularly polarized radiating unit, establishing a direct link between the polarization evolution during waveguide propagation and the final free-space radiation process.

[0039] In terms of structural manufacturing, the input waveguide section, the self-twisting waveguide section, and the radiating opening section are preferably formed integrally from conductive metal, with the inner wall constituting a conductive metal boundary for confining electromagnetic wave propagation. These components can be formed using integral metal processing or additive manufacturing methods suitable for complex three-dimensional waveguide structures to reduce positional deviations caused by splicing multiple independent functional components. For the self-twisting waveguide section, since its internal cavity continuously rotates in space, to avoid deformation after processing due to insufficient wall thickness, the waveguide wall thickness t in this embodiment can be set to 3.0~6.0 mm, preferably 5 mm. A larger and relatively stable wall thickness can improve the overall stiffness of the self-twisting waveguide section, thereby reducing the deformation of the internal cavity contour caused by processing, installation, and external mechanical loads. This helps maintain the torsion angle and geometric consistency of the cross-section at each axial position and further improves the consistency of antenna impedance matching, axial ratio, and far-field radiation pattern.

[0040] The self-twisting waveguide circularly polarized antenna described in this embodiment can operate in the X-band, specifically with a target operating frequency band of 10.2~10.7 GHz. During design, based on this target operating frequency band, the rectangular cross-sectional dimensions, the axial length of the self-twisting waveguide segment, the total torsion angle, and the local torsion characteristics are jointly optimized. This ensures that the input linearly polarized electromagnetic wave forms two orthogonal field components during propagation along the self-twisting waveguide segment, and that these two orthogonal field components have amplitude and phase relationships that satisfy the requirements of circularly polarized radiation when they reach the radiating aperture segment. Simultaneously, through the coordinated matching of the above structural parameters, the self-twisting waveguide segment maintains a good energy transmission state during polarization control, reducing reflections and undesirable mode disturbances that may occur due to continuous rotation of the waveguide boundary.

[0041] After completing the structural design of the self-twisting waveguide circularly polarized antenna, its impedance matching performance, circular polarization performance, and far-field radiation characteristics in the operating frequency band are analyzed. Figure 4 This is the axial ratio curve of the self-torsional waveguide circularly polarized antenna in this embodiment. Figure 4 It can be seen that within the target operating frequency band of 10.2~10.7GHz, the axial ratio of the antenna's main radiation direction remains below 3dB overall. This indicates that the two orthogonal field components formed by the self-twisting waveguide section can maintain a relatively stable amplitude and phase relationship within this frequency band, thus meeting the requirements for circular polarization radiation. In particular, the self-twisting waveguide section, by continuously varying the spatial orientation of the discontinuous rotationally symmetric waveguide cross-section along the propagation direction, allows the linearly polarized electromagnetic wave to gradually undergo orthogonal field component coupling and phase evolution during propagation, rather than relying on a local independent phase difference structure to form the required phase difference all at once. Therefore, it can continuously maintain a good circular polarization state within a certain frequency range. The axial ratio curve further demonstrates that the distributed polarization control process formed by the aforementioned continuous spatial torsion can achieve stable circular polarization radiation performance within the target frequency band.

[0042] Figure 5 This is the differential reflection coefficient curve of the self-torsional waveguide circularly polarized antenna in this embodiment, used to characterize the impedance matching state of the antenna input at different frequencies. Figure 5It can be seen that within the target operating frequency band of 10.2~10.7GHz, the port reflection coefficient remains less than -15dB, indicating that the electromagnetic energy fed into the input waveguide section can effectively enter the self-twisting waveguide section and propagate along it towards the radiating opening section, resulting in minimal reflection at the input end. This result demonstrates that although the self-twisting waveguide section continuously changes its cross-sectional spatial orientation along the propagation direction, by matching the cross-sectional dimensions, axial length, total twist angle, and the axial variation law of the twist angle, the local electromagnetic boundary can change relatively smoothly and continuously with the propagation position. This avoids large local reflections caused by drastic structural abrupt changes, achieving both polarization control and good port impedance matching performance.

[0043] Furthermore, to verify the far-field radiation characteristics of the self-twisted waveguide circularly polarized antenna at the target frequency, the radiation patterns in different observation planes were analyzed. Figure 6 This is the radiation pattern of the self-torsional waveguide circularly polarized antenna in this embodiment at Phi=0° and operating frequency of 10.4GHz. Figure 7 This is the radiation pattern of the self-twisting waveguide circularly polarized antenna in this embodiment at Phi=90° and an operating frequency of 10.4GHz. By examining the radiation characteristics in two mutually orthogonal observation planes at Phi=0° and Phi=90° respectively, the beamforming state of the self-twisting waveguide circularly polarized antenna in the main radiation direction and the spatial distribution of different polarization components can be determined. Figure 6 and Figure 7 As shown in the radiation pattern, the antenna can form a relatively clear and stable main radiation beam at 10.4 GHz. This indicates that after the electromagnetic wave undergoes continuous field component coupling and phase evolution in the self-torsional waveguide section, it can not only form a field distribution that satisfies the circular polarization condition at the radiation opening, but also effectively couple to free space from the radiation opening. This achieves a continuous process from linearly polarized guided wave input, polarization evolution inside the self-torsional waveguide, to circularly polarized radiation in free space.

[0044] comprehensive Figures 4-7As can be seen, this embodiment uses the continuous spatial torsion of the waveguide cross-section as the electromagnetic field propagation boundary itself, distributing the formation, amplitude adjustment, and phase evolution of orthogonal field components throughout the entire propagation path of the self-torsional waveguide segment, and allowing the modulated electromagnetic field to radiate directly from the radiation opening into free space. The above structure can simultaneously achieve a port reflection coefficient of less than -15dB and a main radiation direction axial ratio of less than 3dB in the 10.2~10.7GHz operating frequency band, and forms stable radiation patterns in both the Phi=0° and Phi=90° observation planes at 10.4GHz. This demonstrates that the structure can simultaneously achieve impedance matching, circular polarization formation, and far-field radiation performance, verifying the feasibility of integrating the polarization modulation process with the waveguide transmission and radiation processes.

[0045] Therefore, this embodiment constructs the non-continuous rotationally symmetric waveguide cavity itself as a waveguide boundary that rotates continuously in space along the propagation direction. This allows the electromagnetic wave to sequentially undergo field component coupling, amplitude adjustment, phase evolution, and finally circular polarization radiation within the same continuous waveguide channel. This eliminates the need for an additional independent local polarization control structure within the fixed basic waveguide to generate the propagation constant difference, and also eliminates the need for a separate 90° phase-shifting structure connected in series after the self-twisting waveguide section. The entire polarization control process is distributed along the axial propagation path of the self-twisting waveguide section, thereby reducing the impact of independent functional components and their interfaces on the continuity of electromagnetic propagation.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; under the concept of the present invention, the technical features in the above embodiments may have many other variations as described above in different aspects of the present invention, which are not provided in detail for the sake of brevity; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A self-twisting waveguide circularly polarized antenna, characterized in that, It includes an input waveguide section, a self-torsional waveguide section, and a radiation aperture section that are connected sequentially along the direction of electromagnetic wave propagation; The input waveguide section is used to feed linearly polarized electromagnetic waves. The self-twisting waveguide section has a non-discontinuous rotationally symmetric waveguide cavity cross section. The overall spatial orientation of the cavity cross section changes continuously or segmentally around the propagation axis along the electromagnetic wave propagation direction, so that the direction of the local electromagnetic boundary of the waveguide cavity changes with the propagation position. This allows the linearly polarized electromagnetic wave to gradually couple and form two orthogonal field components during propagation within the self-twisting waveguide section, and the two orthogonal field components form an amplitude and phase relationship that satisfies the circular polarization radiation condition at the output end of the self-twisting waveguide section. The radiating opening section is connected to the output end of the self-twisting waveguide section, and is used to radiate the electromagnetic waves after being modulated by the self-twisting waveguide section into free space.

2. The self-twisting waveguide circularly polarized antenna as described in claim 1, characterized in that, The input waveguide section is used to connect to the feed port of the rectangular waveguide; the radiating opening section is an open waveguide structure, and the waveguide cavity of the radiating opening section is continuously connected to the waveguide cavity on the output side of the self-twisting waveguide section, so that the electromagnetic wave after being regulated by the self-twisting waveguide section transitions from the guided wave state to the free space radiation state.

3. The self-twisting waveguide circularly polarized antenna as described in claim 1, characterized in that, The waveguide cavity cross-section of the self-twisting waveguide section is rectangular, and the wide side and narrow side of the rectangular cross-section rotate sequentially around the propagation axis as the electromagnetic wave propagation position changes.

4. The self-twisting waveguide circularly polarized antenna as described in claim 1, characterized in that, The self-twisting waveguide section is a continuous helical torsion structure, and the overall contour of the waveguide cavity cross section rotates continuously and smoothly around the propagation axis along the electromagnetic wave propagation direction.

5. The self-twisting waveguide circularly polarized antenna as described in claim 1, characterized in that, The self-twisting waveguide segment includes multiple waveguide sub-segments connected sequentially along the electromagnetic wave propagation direction. Each waveguide sub-segment has a non-continuous rotationally symmetric waveguide cavity cross-section. The waveguide cavity cross-sections of adjacent waveguide sub-segments have a preset angle difference around the propagation axis to form a segmented torsion structure.

6. The self-twisting waveguide circularly polarized antenna as described in claim 1, characterized in that, The self-twisting waveguide segment is in the axial position The actual cross-section at the location satisfy: in, Indicates axial position The reference cross section when no torsion occurs. Indicates rotation around the direction of electromagnetic wave propagation The corresponding rotation transformation, Indicates axial position The torsion angle of the waveguide cavity cross-section; the torsion angle It changes linearly or nonlinearly along the direction of electromagnetic wave propagation.

7. The self-twisting waveguide circularly polarized antenna as described in claim 1, characterized in that, The total twist angle of the self-twisting waveguide section is 360°, and the twist direction of the self-twisting waveguide section is used to determine the rotation direction of the circularly polarized electromagnetic wave.

8. The self-twisting waveguide circularly polarized antenna as described in claim 1, characterized in that, The input waveguide section, the self-twisting waveguide section, and the radiating opening section all have conductive metal walls, and the input waveguide section, the self-twisting waveguide section, and the radiating opening section are formed as an integral metal structure.

9. The self-twisting waveguide circularly polarized antenna as described in claim 3, characterized in that, The rectangular cross-sectional dimensions of the self-torsional waveguide section are 20mm × 40mm, and the axial length is 200mm.

10. The self-twisting waveguide circularly polarized antenna as described in claim 1, characterized in that, The self-twist waveguide circularly polarized antenna operates in the frequency band of 10.2 GHz to 10.7 GHz. Within this frequency band, the port reflection coefficient of the self-twist waveguide circularly polarized antenna is less than -15 dB, and the axial ratio of the main radiation direction is less than 3 dB.

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