Waveguide structure, waveguide slot antenna, and radar antenna

Abstract

The specification provides a waveguide structure, a waveguide slot antenna and a radar antenna. The waveguide structure comprises one or more radiation slots arranged along the length direction on the wide side surface of the waveguide cavity, a bias cavity is arranged on the side of the narrow side corresponding to the radiation slot, and the bias cavities of adjacent radiation slots are staggered on both sides of the narrow side respectively. By arranging the bias cavity on the narrow side of the waveguide cavity, the waveguide surface current zero point can be offset from the center line of the wide side, which is conducive to the design of the radiation slot along the center line of the wide side of the waveguide, effectively reduces the size of the wide side of the waveguide, is conducive to the miniaturization design of the waveguide slot antenna in the wide side direction, and reduces the design, simulation and processing difficulty of the waveguide antenna. In addition, the problem of radiation pattern distortion caused by slot offset can be suppressed, and the performance of the waveguide antenna is improved.

Description

Technical Field

[0001] This specification relates to the field of wireless radio frequency technology, specifically to a waveguide structure, a waveguide slot antenna, and a radar antenna. Background Technology

[0002] Millimeter-wave radar, characterized by its short wavelength and strong penetration, can provide accurate environmental information in harsh environments, thus playing a crucial role in advanced driver assistance systems (ADAS). Among these, waveguide antennas have become the mainstream choice for millimeter-wave radar antennas due to their advantages such as low loss, high power, and wide bandwidth.

[0003] Among related technologies, waveguide antennas are difficult to design and manufacture, and their parameters are difficult to optimize. For example, the sidelobe level is difficult to suppress and may become distorted, affecting the performance of the waveguide antenna. Summary of the Invention

[0004] To address the aforementioned technical problems, this specification provides a waveguide structure, a waveguide antenna formed using the waveguide structure, and a radar antenna having the waveguide antenna.

[0005] In a first aspect, embodiments of this specification provide a waveguide structure, the waveguide structure including a waveguide cavity located inside a metal body, the waveguide cavity including a wide side and a narrow side; Multiple radiation slots are provided along the length of the wide side surface of the waveguide cavity; On one side of the narrow side corresponding to each radiation slot, a bias cavity is provided along the surface of the narrow side and toward the side opposite to the surface of the wide side. The bias cavity causes the zero point of the surface current of the waveguide cavity to deviate from the center line of the wide side. The bias cavities corresponding to two adjacent radiation slots are located on opposite narrow sides of the waveguide cavity.

[0006] In some possible implementations, the plurality of radial slits are located on the center line of the wide side and are spaced apart along the center line of the wide side.

[0007] In some possible implementations, the first dimension of the bias cavity along the length direction is larger than the second dimension of the radiation slit along the length direction; And / or, The first dimension of the bias cavity along its length is equal to or approximately equal to half the wavelength of the waveguide, and the second dimension of the radiation slit along its length is equal to or approximately equal to half the wavelength of free space.

[0008] In some possible implementations, the bias cavity includes a functional segment extending along the narrow side surface toward a side opposite to the wide side surface, and a transition segment is provided on at least one side of the functional segment along its length direction, the transition segment forming a chamfered structure to connect the side of the functional segment to the waveguide cavity. The chamfered structure formed by the transition section includes a planar chamfered structure or an arc-shaped chamfered structure.

[0009] Secondly, embodiments of this specification provide a waveguide slot antenna, including a metal body and a waveguide cavity and a feed cavity formed inside the metal body, wherein the waveguide cavity has a waveguide structure as described in any of the above embodiments; The metal body includes a top surface extending in a horizontal direction, and the metal body has an antenna radiation hole extending from the radiation slot to the top surface corresponding to the position of each radiation slot. The first end of the feeding cavity is connected to the feeding waveguide, and the second end is connected to the waveguide cavity. The feeding cavity is used to transmit the electromagnetic waves input by the feeding waveguide to the waveguide cavity to excite each radiation slot to radiate signals outward.

[0010] In some possible implementations, the feeding cavity includes a polarization direction switching unit, which is used to configure the electromagnetic wave input from the feeding waveguide in a first polarization direction to a second polarization direction orthogonal to the first polarization direction. And / or, The waveguide antenna further includes at least one tuning element, which is disposed in the feed cavity and / or the waveguide cavity, and the tuning element is used to adjust the equivalent impedance in the feed cavity and / or the waveguide cavity.

[0011] In some possible implementations, the second end of the feed cavity is connected to one side of the waveguide cavity along its length; In the waveguide cavity, the bias cavities corresponding to any two adjacent radiation slots are located on opposite narrow sides of the waveguide cavity.

[0012] In some possible implementations, the second end of the feeding cavity is connected to the middle of a narrow side surface of the waveguide cavity, and the waveguide cavity includes a plurality of radiation slots symmetrically arranged on both sides of the feeding cavity. In a local waveguide cavity located on any side of the feeding cavity, the bias cavities corresponding to two adjacent radiation slots are located on the narrow sides of the waveguide cavity on opposite sides, respectively. The bias cavities corresponding to two adjacent symmetrical radiation slots close to the feed cavity are located on the same narrow side of the waveguide cavity.

[0013] In some possible implementations, the antenna radiating aperture includes an antenna port and an antenna opening, the antenna port being connected to the radiating slot, and the antenna opening being connected to the antenna port, wherein the size of the antenna opening gradually increases from the connecting end to the top surface; And / or, The top surface is provided with multiple choke structures. The choke structures are recessed from the top surface of the metal body and their length direction is parallel to the length direction of the waveguide cavity. The multiple choke structures are arranged at intervals and are respectively located on both sides of the antenna radiation hole.

[0014] Thirdly, embodiments of this specification provide a radar antenna, including a waveguide antenna array, wherein the waveguide antenna array includes multiple waveguide antennas, and the waveguide antennas are the waveguide antennas described in any of the above embodiments.

[0015] The waveguide structure described in this specification includes multiple radiating slots arranged along the length of the wide side surface of the waveguide cavity. A bias cavity is provided on one side of the narrow side corresponding to each radiating slot, and the bias cavities of adjacent radiating slots are staggered on both sides of the narrow side. By utilizing the bias cavity arranged on the narrow side of the waveguide cavity, the zero point of the waveguide surface current can be deviated from the centerline of the wide side. The radiating slots, positioned at the centerline, can also effectively cut the current to generate radiated energy. This facilitates the design of the radiating slots along the centerline of the wide side of the waveguide, thereby effectively reducing the waveguide's dimensions in the wide side direction. This is beneficial for miniaturizing the waveguide slot antenna in the wide side direction and reduces the difficulty of waveguide antenna design, simulation, and fabrication. Furthermore, it can suppress the radiation pattern distortion caused by slot offset, improving the waveguide antenna performance. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the specific embodiments or related technologies of this specification, the drawings used in the description of the specific embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are some embodiments of this specification. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the cavity structure of a rectangular waveguide in related technologies.

[0018] Figure 2 This is a cross-sectional schematic diagram of the waveguide geometry model in some embodiments of this specification.

[0019] Figure 3 This is a schematic diagram of the mesh points of the waveguide geometry model in some embodiments of this specification.

[0020] Figure 4This is the equivalent circuit diagram of a rectangular waveguide in related technologies.

[0021] Figure 5 This is a waveguide model diagram of some embodiments in this specification.

[0022] Figure 6 This is a waveguide model diagram of some other embodiments in this specification.

[0023] Figure 7 yes Figure 6 The diagram shows the electric field and current distribution of the waveguide model.

[0024] Figure 8 This is a waveguide model diagram of some other embodiments in this specification.

[0025] Figure 9 This is a schematic diagram of the waveguide structure in some embodiments of this specification.

[0026] Figure 10 This is a side view of the waveguide structure in some embodiments of this specification.

[0027] Figure 11 This is a schematic diagram of a waveguide slot antenna in some embodiments of this specification.

[0028] Figure 12 This is a schematic diagram of the cavity of the waveguide slot antenna in some embodiments of this specification.

[0029] Figure 13 This is a cavity schematic diagram of a waveguide slot antenna in some other embodiments of this specification.

[0030] Figure 14 This is a schematic diagram of a waveguide slot antenna in some other embodiments of this specification.

[0031] Figure 15 This is a schematic diagram of a radar antenna in some embodiments of this specification. Detailed Implementation

[0032] The technical solutions of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this specification, not all of them. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this specification. Furthermore, the technical features involved in the different embodiments of this specification described below can be combined with each other as long as they do not conflict with each other.

[0033] A waveguide is a hollow tube encased in a metal shell. It relies on total internal reflection of the metal wall to confine electromagnetic waves to propagate inside the cavity. Its transmission loss is much lower than that of traditional antennas, and it has strong anti-interference capabilities and strong stability in complex electromagnetic environments such as vehicle radar. Therefore, it is widely used in vehicle millimeter-wave radar antennas.

[0034] In waveguide antennas, to achieve electromagnetic wave radiation, multiple slots need to be created on the surface of the waveguide cavity. These slots are staggered and offset on both sides of the centerline of the wide side of the waveguide surface, for example... Figure 1 The diagram shows a cavity structure of a rectangular waveguide in the related technology. Multiple slot outlets are opened on the wide side surface of the waveguide and must be offset from the center line of the surface. The energy radiated by the slots varies with the distance from the center line, thereby achieving the purpose of power distribution.

[0035] It can be understood that the surface current distribution of a waveguide TE mode (transverse electromagnetic wave) is as follows: at the centerline of the wide side of the waveguide surface, the transverse current is zero, that is, the centerline is the current zero point, while there is a transverse current component at locations away from the centerline. In order to effectively radiate electromagnetic waves outward, the slot exits must cut off the surface current. If the slots are set on the centerline, energy cannot be radiated. Therefore, multiple slot exits must be set off from the centerline.

[0036] However, this approach has drawbacks. The varying distances of each slot exit from the centerline increase the difficulty of antenna design and simulation. Furthermore, the high precision required for slot placement increases manufacturing complexity. Left-right offset slots can lead to difficult-to-suppress and distorted sidelobe levels, and in cases with a small number of slots, can even cause main lobe distortion, affecting waveguide antenna performance. Arranging the slot exits collinearly along the centerline can better address these issues. However, to achieve power distribution at each slot exit, an additional power divider is needed. The power divider's cavity structure is complex, making design and manufacturing more difficult, and it also causes additional power loss, reducing antenna performance.

[0037] To address this technical problem, some embodiments of this specification provide a waveguide structure, a waveguide antenna formed using the waveguide structure, and a radar antenna having the waveguide antenna. By optimizing the waveguide cavity structure, the surface current zero point on the wide side of the waveguide is offset from the center line, which is beneficial for achieving the centered setting of the radiation slot.

[0038] In some embodiments, this specification provides a waveguide structure that is a metal cavity structure, such as a waveguide cavity formed inside a metal body.

[0039] It is worth noting that, taking a rectangular waveguide as an example, a rectangular waveguide refers to a waveguide cavity with a rectangular cross-sectional shape, such as... Figure 1As shown, the waveguide cross-section refers to the section perpendicular to the center line of the diagram. In the field of waveguide technology, the structure of a rectangular waveguide is described using wide and narrow sides. The wide side refers to the long side of the rectangle, and the narrow side refers to the short side. Correspondingly, the surface where the wide side of the rectangular waveguide is located is called the wide wall (or wide surface), and the surface where the narrow side is located is called the narrow wall (or narrow surface). That is, the cavity structure of a rectangular waveguide is a cubic structure formed by two wide walls and two narrow walls.

[0040] In this specification, multiple radiation slots are formed along the length of the wide side surface (i.e., wide wall) of the waveguide cavity. These radiation slots are used to radiate millimeter-wave signals outward. Furthermore, on one side of the narrow side corresponding to each radiation slot, a bias cavity is provided, extending along the narrow side surface and toward the side opposite to the wide side surface. The bias cavities corresponding to two adjacent radiation slots are located on opposite narrow sides of the waveguide cavity.

[0041] As described above, in a traditional rectangular waveguide, if the radiating slot is located on the center line of the wide side surface, the radiating slot is a zero point of lateral current, and energy cannot be effectively radiated outward. Therefore, in the embodiments of this specification, a bias cavity is provided on one side of the narrow side corresponding to each radiating slot, extending along the narrow side surface and toward the side opposite to the wide side surface. The bias cavity is used to deviate the position of the zero point of the wide wall current of the waveguide cavity from the center line, thereby enabling effective energy radiation at the center line position of the wide wall.

[0042] It is worth noting that in the scheme described in this specification, the irregularly shaped bent waveguide formed by the bias cavity structure can deviate the position of the wide-wall current zero point from the centerline, thereby enabling the radiating slot located at the centerline of the wide wall to effectively cut the current and generate energy radiation. However, this does not mean that the radiating slot of the waveguide structure provided in this specification must be located on the centerline of the wide-side surface. Rather, it provides a design concept that allows the radiating slot to be set along the centerline of the wide wall. For example, in some embodiments, the radiating slot can be set off from the centerline of the wide wall according to specific needs, as long as the current can be effectively cut at the radiating slot.

[0043] For example, in other embodiments, the radiating slots can be positioned along the centerline of the wide wall, such as multiple radiating slots arranged collinearly and at intervals along the centerline of the wide wall. This reduces the difficulty of waveguide antenna design, simulation, and fabrication, and suppresses the radiation pattern distortion caused by slot offset. Furthermore, a centered radiating slot design effectively reduces the size in the wide side direction, thus facilitating miniaturization of the waveguide antenna in the wide side direction.

[0044] To facilitate a detailed understanding and explanation of the scheme described in this specification, the theoretical basis of the waveguide structure in the implementation method described in this specification will be explained below.

[0045] The waveguide structure described in this specification is an irregularly shaped, bent structure, which differs from the traditional rectangular waveguide. To investigate the influence of the electromagnetic field within this irregularly shaped, bent waveguide cavity, a cross-sectional shape is constructed as follows: Figure 2 The irregular waveguide shown is analyzed using the finite difference method, and its transmission characteristics, such as the cutoff wavelength of the dominant mode (TE mode), are also analyzed.

[0046] exist Figure 2 In the example, 'a' represents the length of the wide side, 'b1' and 'b2' represent the lengths of the two narrow sides, and 'c' represents the width of the bias cavity. In this geometric model, the waveguide is assumed to be filled with air and is longitudinally uniform. In one example, the longitudinal field method is used, with 'u' representing the electric field along the z-axis. The z-axis direction is the direction of electromagnetic wave propagation, which can be referenced. Figure 2 The directions indicated by the o-xyz coordinate system in the example.

[0047] In this example, the electromagnetic field structure within the waveguide can be reduced to solving a two-dimensional scalar wave equation, also known as a two-dimensional Helmholtz homogeneous wave equation, expressed as: (1) In formula (1), It represents the second-order partial derivative of u with respect to the transverse coordinate x, and its physical meaning is the rate of change of the longitudinal electric field u along the wide side (x direction) of the waveguide. It represents the second-order partial derivative of u with respect to the longitudinal coordinate y, and its physical meaning is the rate of change of the longitudinal electric field u along the narrow side (y direction) of the waveguide. It is the cutoff wavenumber, determined by the waveguide cross-sectional geometry, where, k represents the free space wavenumber. Angular frequency, The permeability of the medium, The dielectric constant of the medium, This represents the phase change coefficient along the z-direction of the waveguide.

[0048] It is understandable that the Helmholtz equation is a continuous equation and cannot be solved directly. Therefore, the finite difference method is used to transform the continuous partial differential equation into a difference expression. Its physical meaning is to divide the waveguide cross section into grid points, and the field value of each grid point in the field can be represented by the value of the adjacent point.

[0049] For example Figure 3 As shown, grid point o is the grid point to be determined within the field, and the field value is... Grid point 1 is a neighboring point in the positive x-axis direction, and its field value is... Grid point 3 is a neighboring point in the negative x-axis direction, and its field value is... Grid point 2 is a neighboring point in the positive y-axis direction, and its field value is... Grid point 4 is a neighboring point in the negative y-axis direction, and its field value is... h represents the basic grid unit step size, ph represents the x-direction distance from grid point 0 to 1, rh represents the x-direction distance from grid point 0 to 3, qh represents the y-direction distance from grid point 0 to 2, and th represents the y-direction distance from grid point 0 to 4. Among these, p,r,q,t ≤ 1 is constrained.

[0050] For the waveguide dominant mode (TE mode), u satisfies the homogeneous Norman boundary condition on the waveguide wall, i.e. The Helmholtz equation is transformed into a difference expression using forward difference and central difference: (2) (3) Then, substituting formulas (2) and (3) into formula (1), we can obtain: (4) Equation (4) represents the equation satisfied by grid point 0 within the waveguide. It can be understood that the waveguide cross-section is divided into n grid points, thus extending Equation (4) to all grid points yields the field values ​​to be determined at each grid point. The system of n difference equations (i=1,2,3,…,n) with unknowns can be represented in matrix form as follows: (5) In formula (5), The matrix coefficients are determined entirely by the shape and size of the waveguide cross-section. The field values ​​to be determined at the grid points It is a column vector of components. Denotes the eigenvalues, where, , Indicates the cutoff wavelength of the waveguide. Therefore, the above problem can be reduced to a matrix eigenvalue problem, which involves finding the eigenvalues ​​of the matrix. You can get This leads to the cutoff wavelength of the waveguide. .

[0051] Through the finite difference numerical analysis of the above formulas (1) to (5), it can be seen that when the cross-sectional shape and / or size of the waveguide cavity is changed, the surface current distribution of the main mode in the waveguide cavity will change accordingly. This provides an effective theoretical basis for the design of the irregular waveguide structure in the embodiments of this specification. The design process of the irregular waveguide structure in the embodiments of this specification will be further explained below.

[0052] First of all, Figure 1 The example illustrates the use of rectangular waveguides in related technologies. Figure 4The equivalent circuit diagram of this rectangular waveguide is shown. (For example...) Figure 4 As shown, the center distance of the end slot outlet from the short surface on the right side of the waveguide is... The center-to-center distance between two adjacent slit exits is , The wavelength is the waveguide wavelength, and adjacent slot exits are alternately located on both sides of the centerline of the wide wall of the waveguide and at the antinode of the standing wave voltage.

[0053] In the relevant technical solution, the outlets of adjacent gaps are offset to both sides of the center line. Since the surface currents of the TE mode are in opposite directions on both sides of the center line, the resulting 180° phase shift precisely compensates for the spacing between adjacent gaps. The resulting phase difference allows the various slot exits to radiate in phase. Using the equivalent circuit method, the slot exits are represented as parallel admittance elements, and the conductance of the slot exits is expressed as: (6) In formula (6), g represents the slot conductance, which represents the magnitude of the slot radiation power. a represents the length of the wide side of the rectangular waveguide. b represents the length of the narrow side of the rectangular waveguide. This represents the wavelength of a wave in free space in air. d represents the waveguide wavelength. d represents the distance of the slit from the center line of the wide side. As can be seen from formula (6), the larger the distance d of the slit from the center line, the larger the conductance g, that is, the higher the radiated power of the slit. Thus, the power distribution at the outlet of each slit can be achieved by adjusting the spacing d.

[0054] In the irregular waveguide design of the embodiments described in this specification, the TE mode electromagnetic field of the waveguide cavity is offset relative to the center of the wide side, so that the slots are located on the center line while also cutting the current to generate radiation. According to formula (6), the relationship between the admittance of each slot in the irregular waveguide and the narrow side dimension b1 can be derived: (7) In formula (7), k is a constant and b1 is the narrow side dimension. According to formula (7), if you want to adjust the conductivity g (equivalent to the radiation power) of the slit outlet, you only need to change the length of one side of the narrow side. In this way, the radiation slit can be centered on the center line of the wide side.

[0055] The above provides a correlation between the radiated power of the radiating slot and the narrow side dimension, offering reliable theoretical guidance for the design of irregular waveguide structures in this specification. (1) By setting an offset cavity on one side of the radiation gap to extend the narrow side dimension, the current zero point that was originally located on the center line of the wide side can be shifted, so that setting the radiation gap on the center line of the wide side can also cut the current to generate radiation energy.

[0056] (2) For two adjacent radiation slots, the bias cavities of the two slots are staggered on the narrow sides of the two slots respectively. The reverse characteristics of the original surface current can be used to compensate for the phase difference caused by the slot spacing, so as to realize the in-phase radiation of multiple radiation slots.

[0057] (3) The longer the bias cavity extends the narrow side, the higher the radiation power distributed to the radiation slots on the corresponding wide wall.

[0058] Based on the above theoretical basis, the design and simulation process of the waveguide structure of the embodiment in this specification will be described below.

[0059] It can be understood that the design goal of an antenna is to satisfy a given radiation pattern. The radiation pattern is used to characterize the antenna's radiation performance, including the main lobe radiation pattern, side lobe radiation patterns, etc. For a waveguide antenna, suppose it has N (N≥1) radiation slots. This represents the excitation amplitude of the nth radiating slit (pre-obtained based on the radiation pattern during design, and is a known quantity). All slits have the same size and are in a resonant state. Indicates the conductivity of each radiating slot. This represents the radiated power of the nth radiating slit. To represent the total radiated power, we have: (8) Depend on Figure 4 Examples can be obtained as follows: (9) In formula (9), Indicates the total input admittance. When the end is fed Combining equations (8) and (9), we can obtain: (10) The admittance of each radiation slot can be derived from the excitation amplitude of each slot, and then extracted using electromagnetic simulation software. The geometric model can be set to have distances of [missing information - likely related to distances between the slots and their ends]. From transmission line theory, the transmission matrix T is expressed as: (11) In formula (11), y represents the admittance of a single radiation slot, and the T matrix is ​​from microwave transmission line theory. The conversion relationship between the S matrix and the T matrix is ​​expressed as: (12) Then, by combining equations (11) and (12), we can obtain: (13) In formula (13), This represents the port reflection coefficient, which can be directly obtained through simulation software. Therefore, the admittance value y of the radiation slit can be obtained through simulation.

[0060] First, let's take a single-radiating slot waveguide as an example. See [link / reference] Figure 5 As shown, the radial slit is located on the center line of the wide side, and the dimension of one narrow side is b1. The center of the radial slit is located at the distance from both ends. In this waveguide model, electromagnetic simulation software can be used to traverse the waveguide using b1 as the parameter, continuously modifying the parameter values ​​of b1 and calculating the reflection coefficient. Based on formula (13), the admittance value of the radiation slit can be calculated in reverse until the calculated admittance value matches the aforementioned target value. If the values ​​are the same or similar, the value of b1 at this point is the narrow side dimension corresponding to the radial slit.

[0061] The above example, using a single radiating slot, illustrates the design and simulation process of waveguide structures. Figure 6 The cavity structure of an irregular waveguide with two radiating slots is shown. In this example, the target admittance values ​​for the two slots are different because the radiated power of each slot is different given the radiation pattern. There are also differences, so for each radiating slit, the above design and simulation process is repeated to calculate the narrow side dimension b1 corresponding to each slit unit. This specification will not elaborate on this further.

[0062] It is worth noting that, in Figure 6 In the example, the bias cavities corresponding to two adjacent radiation slits are alternately arranged on the narrow sides of both sides, for example... Figure 6 As shown in (b), the two bias cavities are respectively located on the narrow sides of the waveguide. As mentioned above, this staggered arrangement can utilize the characteristic that the surface current on the wide side is opposite about the center line to compensate for the 180° phase difference caused by the gap spacing, and achieve in-phase radiation of the two gaps.

[0063] Figure 7 (a) shows Figure 6 Electric field distribution in the waveguide Figure 7 (b) shows Figure 6 The current distribution of the waveguide shows that the zero points of the surface current on the wide side at the two radiating slot locations are both deviated from the center line, and are located on the left and right sides of the center line, respectively. This also proves the feasibility of the irregular waveguide of the embodiment in this specification, that is, by using the bias cavity structure, the surface current zero points of the waveguide cavity can be effectively deviated from the center line of the wide side, thereby achieving the centered arrangement of the radiating slots on the center line of the wide side.

[0064] Based on the above conclusions and proofs, waveguide cavities can be extended to structures that include more radiation slots, such as... Figure 8As shown, these radiation slots can be arranged centered on the center line of the wide side of the waveguide, and the bias cavities of adjacent radiation slots are located on the narrow sides respectively. That is, the bias cavities of multiple radiation slots are alternately arranged on the narrow sides.

[0065] As can be seen from the above, in the embodiments of this specification, by using the bias cavity set on the narrow side of the waveguide cavity, the zero point of the current on the waveguide surface can be deviated from the center line of the wide side. The radiation slots set at the center line position can also effectively cut the current to generate radiation energy. Therefore, the radiation slots can be arranged along the center line of the wide side of the waveguide, which reduces the difficulty of waveguide antenna design, simulation and manufacturing, and also alleviates the problem of radiation pattern distortion caused by slot offset, effectively improving the performance of the waveguide antenna.

[0066] Figure 9 Schematic diagrams of waveguide structures in some embodiments of this specification are shown below. Figure 9 Examples are provided for illustration. It can be understood that the waveguide structure described in this specification refers to a waveguide cavity located inside a metal body, that is, Figure 9 The waveguide structure shown is a cavity structure.

[0067] See Figure 9 As shown in (a), the waveguide cavity 100 includes a wide side and a narrow side. According to the direction indicated by the coordinate system o-xyz, the wide side of the waveguide cavity 100 is the side parallel to the x-axis direction, and the narrow side is the side parallel to the y-axis direction. The z-axis direction is the direction of electromagnetic wave transmission inside the waveguide cavity 100. The surface formed by the wide side is called the wide wall (or wide surface), and according to the coordinate system, the wide wall is the surface parallel to the xoz plane; the surface formed by the narrow side is called the narrow wall (or narrow surface), and according to the coordinate system, the narrow wall is the surface parallel to the yoz plane.

[0068] In the embodiments described in this specification, k (k≥1) radiation slots 110 are provided on the wide side surface of the waveguide cavity, for example... Figure 9 In the example, a total of k=4 radiating slots 110 are set on the wide side surface of the waveguide cavity. It is worth noting that the k radiating slots are collinear and spaced apart along the center line L of the wide side. That is to say, each radiating slot is centered on the center line L of the wide wall and does not need to deviate from the center line L.

[0069] Combination Figure 9As shown in (a), each portion of the waveguide cavity corresponding to each radiating slot 110 is defined as a slot element F, thus the waveguide cavity 100 in this example sequentially includes slot elements F1 to F4 along the z-axis direction. The z-axis dimension of each slot element F is the distance from the center point of the spacing between two slots to the center point of the next spacing. In some embodiments, the z-axis length of each slot element F is 1 / 2λ1, where λ1 is the waveguide wavelength. Furthermore, the center-to-center spacing between two adjacent radiating slots 110 is also 1 / 2λ1.

[0070] In this embodiment of the specification, in each slot cell F, a bias cavity 120 is provided on one narrow side, extending along the narrow wall in a direction away from the radiation slot. The bias cavity 120 transforms the original rectangular waveguide cavity into a structure with the bottom of the narrow wall protruding. Moreover, as can be seen from the foregoing, the bias cavities 120 of two adjacent slot cells F are located on the narrow walls on both sides, respectively.

[0071] For example, combining Figure 9 As shown in (b), for slot unit F1, a bias cavity 120a is provided on one side of its narrow wall, while for the adjacent slot unit F2, the bias cavity 120b is provided on the other side of the narrow wall, which is different from 120a. For slot unit F3, the bias cavity 120c is provided on the same narrow wall as 120a but different from 120b, and so on, forming a structure in which the bias cavities 120 of adjacent slot units are alternately arranged on the narrow walls on both sides.

[0072] In some embodiments, a first dimension of the bias cavity 120 along the length direction (z-axis direction) of the waveguide cavity is larger than a second dimension of the radiation slot 110 along the length direction. For example Figure 10 As shown, Figure 10 This is a side view of the waveguide cavity 100, that is, from... Figure 9 The viewing angle in the -x direction of (a). In this example, the first dimension of the bias cavity 120 along its length is 1 / 2λ1, and the second dimension of the radiation slit 110 along its length is 1 / 2λ2. Wherein, λ1 is the waveguide wavelength, that is, the wavelength of the millimeter wave propagating in the waveguide; λ2 is the free space wavelength, that is, the wavelength of the millimeter wave propagating in free space (such as air). It can be understood that the waveguide wavelength of the millimeter wave is greater than the free space wavelength, therefore the first dimension of the bias cavity 120 is greater than the second dimension of the radiation slit 110.

[0073] In some embodiments, as described above, since the narrow wall dimension b1 of the slot element corresponding to each radiation slot 110 needs to be calculated and simulated based on the radiation pattern, the extension length of the bias cavity 120 corresponding to different slot elements is also different. This extension length refers to the length extending from the bottom narrow wall of the waveguide cavity 100 along the -y direction. For example... Figure 10In the example, the extension length of the bias cavity 120 of slot element F1 is x1, and the extension length of the bias cavity 120 of the adjacent slot element F2 is x2. In this example, x2 is greater than x1. By optimizing the extension length of the bias cavity 120, the radiated power of the radiating slot 110 can be adjusted, thereby optimizing the design of the antenna pattern sidelobes.

[0074] In some embodiments, the bias cavity 120 includes a functional segment extending along the narrow side surface toward the side opposite to the wide side surface, and a transition segment is provided on at least one side of the functional segment along the length direction, the transition segment forming a chamfered structure to connect the side of the functional segment with the waveguide cavity 100.

[0075] It is understandable that the waveguide cavity 100 is a cavity structure formed in the metal body. Therefore, due to the presence of the bias cavity 120, the position of the bias cavity 120 will have a height difference with the bottom wide wall of the waveguide cavity 100. If the bias cavity 120 and the waveguide cavity 100 are connected at a right angle, the millimeter wave will be strongly reflected during transmission, generating a standing wave inside the waveguide and reducing the antenna radiation gain.

[0076] Therefore, in this embodiment of the specification, the bias cavity 120 is divided into a functional segment and a transition segment. The functional segment is the core structure for realizing the above-mentioned zero-point offset and power distribution, while the transition segment is a chamfered structure set on one or both sides of the functional segment to connect and transition with the waveguide cavity 100.

[0077] For example Figure 10 In the example, the bias cavity 120 of the slot unit F3 includes a functional segment e1 and transition segments e2 and e3 located on both sides of the functional segment e1. In this example, the transition segments e2 and e3 change the two sides of the functional segment e1 from right angles to planar chamfered structures. Compared with right angle connections, the planar chamfered structure can effectively reduce reflected waves, thereby optimizing waveguide standing waves and improving antenna gain.

[0078] exist Figure 10 In the example, transition segments e2 and e3 are planar chamfered structures. In other embodiments, the transition segments can also be set as arc-shaped chamfered structures. Those skilled in the art will understand this, and this specification will not elaborate further.

[0079] As described above, in this embodiment, by utilizing a bias cavity positioned along the narrow side of the waveguide cavity, the zero point of the waveguide surface current can be deviated from the centerline of the wide side. The radiating slot, positioned along the centerline, can also effectively cut the current to generate radiated energy. Therefore, it is advantageous to design the radiating slot along the centerline of the wide side of the waveguide, reducing the difficulty of waveguide antenna design, simulation, and fabrication. Furthermore, it alleviates the radiation pattern distortion caused by slot offset, effectively improving waveguide antenna performance. Moreover, it can effectively reduce the size along the wide side, facilitating miniaturization of the waveguide antenna along this direction. Additionally, by setting the bias cavity structure with functional and transition sections, reflected waves can be effectively reduced, increasing the antenna radiation gain.

[0080] The structure and principle of the waveguide cavity exemplified in this specification have been described above. The waveguide antenna formed using the above waveguide cavity will be described below.

[0081] In some embodiments, this specification provides a waveguide antenna comprising a metallic body and a waveguide cavity and a feed cavity formed within the metallic body. The waveguide cavity may have the waveguide structure described in any of the foregoing embodiments. The metallic body includes a top surface extending in a horizontal direction, and an antenna radiation aperture extending from the radiation slot to the top surface is formed at the location of each radiation slot. A first end of the feed cavity is connected to a feed waveguide, and a second end is connected to the waveguide cavity. The feed cavity is used to transmit electromagnetic waves input from the feed waveguide to the waveguide cavity to excite each radiation slot to radiate signals outward.

[0082] Figure 11 This specification shows schematic diagrams of waveguide antennas according to some embodiments. The following is a description in conjunction with... Figure 11 Please provide an explanation.

[0083] The metal body 200 is the main structure of the waveguide antenna, and the waveguide cavity 100 can be formed inside the metal body 200 by material removal processing. For example... Figure 11 As shown in (a), the metal body 200 includes an upper metal body 210 and a lower metal body 220 stacked together, with the upper metal body 210 located above the lower metal body 220.

[0084] In this example, the upper surface of the upper metal body 210 forms the top surface of the metal body 200, and the lower surface of the lower metal body 220 forms the bottom surface of the metal body 200. The upper metal body 210 and the lower metal body 220 can be connected to form an integral structure through processes such as welding and bonding.

[0085] See Figure 11As shown in (b), the aforementioned waveguide structure is formed between the upper metal body 210 and the lower metal body 220 through a material removal process. For example, in some embodiments, the waveguide cavity included in the waveguide structure may also be divided into two parts, one part located in the upper metal body 210 and the other part located in the lower metal body 220. After the upper metal body 210 and the lower metal body 220 are assembled and connected, the two parts of the cavity are combined to form a complete waveguide cavity.

[0086] For example Figure 11 In the example shown in (b), a rectangular cavity portion of the waveguide cavity 100 can be formed by processing the inner surface of the upper metal body 210, while an offset cavity 120 can be formed by processing the inner surface of the lower metal body 220. Thus, after the upper metal body 210 and the lower metal body 220 are assembled, the rectangular cavity portion and the offset cavity 120 are combined to form a complete waveguide cavity 100.

[0087] Figure 12 The cavity structures of waveguide cavity 100 and feed cavity 130 in the example of this specification are shown below. Figure 12 Please provide an explanation.

[0088] exist Figure 12 In the example, the waveguide cavity 100 is end-fed, that is, the feeding cavity 130 is connected to one end of the waveguide cavity 100 along its length, so that the millimeter wave is transmitted unidirectionally along the length of the waveguide cavity 100 after being input through the feeding cavity 130.

[0089] It can be understood that the function of the feeding cavity 130 is to connect the feeding waveguide and the waveguide cavity 100. The feeding waveguide refers to the waveguide transmission line, which connects to the radio frequency front-end circuit of the millimeter wave antenna. Thus, the millimeter wave generated by the radio frequency front-end circuit is transmitted to the feeding cavity 130 through the feeding waveguide, and then sent into the waveguide cavity 100 for transmission through the feeding cavity 130, and radiates energy outward through the radiation slot 110.

[0090] In this example, the feeding cavity 130 includes a polarization direction conversion unit 131 and a tuning element 132 disposed inside the polarization direction conversion unit 131. The polarization direction conversion unit 131 is used to configure an electromagnetic wave signal input from the feeding waveguide in a first polarization direction to a second polarization direction, the second polarization direction being orthogonal to the first polarization direction. Optionally, the polarization direction conversion unit 131 can adopt an E-plane to H-plane structure, its function being to convert the electromagnetic wave from one polarization direction to another.

[0091] The first and second polarization directions refer to the vertical and horizontal polarization directions within the horizontal plane, respectively. Horizontal polarization refers to the polarization state where the direction of the electric field vector's vibration is parallel to the horizontal plane. Horizontally polarized antennas typically have a wide horizontal coverage area and are suitable for terrestrial broadcasting and certain communication systems. Horizontally polarized antennas have higher gain in the horizontal direction, making them suitable for horizontal signal propagation. Vertical polarization refers to the polarization state where the direction of the electric field vector's vibration is perpendicular to the horizontal plane. Vertically polarized antennas typically have higher gain and are suitable for communication systems requiring high directivity.

[0092] For example Figure 12 In this example, the polarization direction conversion unit 131 includes an input port M, which is connected to a feeding waveguide. In this example, the input port M is in the vertical polarization direction, meaning that the millimeter wave transmitted from the feeding waveguide to the polarization direction conversion unit 131 is in the vertical polarization direction, while the waveguide cavity 100 is in the horizontal polarization direction. Thus, the polarization direction conversion unit 131 converts the electromagnetic wave in the vertical polarization direction entering through the input port M into the horizontal polarization direction and sends it into the waveguide cavity 100 for horizontal polarization direction transmission.

[0093] In this example, a tuning element 132 is also provided within the polarization direction switching unit 131. Optionally, the tuning element 132 can be a metal block. For example, when the power supply cavity 130 is processed in the metal body 200, a portion of the structure can be retained to form the tuning element 132, which can be located inside or near the polarization direction switching unit 131.

[0094] The tuning element 132 is used to adjust the impedance matching state of the feeding cavity 130, thereby optimizing the port standing wave ratio (VSWR) at the polarization direction transition unit 131. For example, during the transmission of electromagnetic waves from the feeding waveguide through the polarization direction transition unit 131 to the waveguide cavity 100, impedance discontinuities may occur at the polarization direction transition unit 131 due to the change in polarization direction and the change in the cross-sectional shape of the cavity, resulting in reflected waves and an increase in the VSWR. By adjusting the size or position of the tuning element 132, a compensating reactance can be introduced to counteract the reflection at the polarization direction transition unit 131, thereby reducing the port VSWR and ensuring efficient transmission of electromagnetic wave energy to the waveguide cavity 100, reducing energy loss.

[0095] In some embodiments, the tuning element 132 is made of metal and is block-shaped, columnar, or sheet-shaped, embedded in the cavity wall or internal cavity of the polarization direction transition unit 131. The position and size of the tuning element 132 can be determined by simulation or experimental debugging based on the actual impedance characteristics of the polarization direction transition unit 131, which will not be described in detail in this specification.

[0096] Continue to refer to Figure 12As shown in (b), in this example, the structure and shape of the waveguide cavity 100 can be referred to the aforementioned Figure 9 and Figure 10 In this embodiment, the multiple radiation slots 110 of the waveguide cavity 100 are arranged at intervals along the centerline of the wide wall, and the bias cavities 120 of adjacent radiation slots 110 are alternately arranged on the narrow walls on both sides. Those skilled in the art can understand and fully implement this by referring to the foregoing embodiments, and this specification does not impose any limitations thereon.

[0097] Combination Figure 11 and Figure 12 As shown, in this example, an antenna radiation hole 230 extending from the radiation slot 110 to the top surface is provided on the top surface of the metal body 200 corresponding to the position of the radiation slot 110. Figure 12 As shown in (a), the antenna radiation aperture 230 includes an antenna port 231 and an antenna opening 232. The antenna port 231 is connected to the radiation slot 110 and extends along the normal direction perpendicular to the horizontal direction. The antenna opening 232 is connected to the antenna port 231, and the opening size of the antenna opening 232 gradually increases from the connection position to the top surface. That is, the size of the antenna opening 232 gradually opens to form a horn shape. This horn-shaped opening adjusts the antenna beamwidth by its flare angle and length, and serves as a gradual transition structure from the waveguide cavity to free space to reduce radiation reflection and improve radiation efficiency.

[0098] In some embodiments, the top surface of the metal body 200 is further provided with one or more choke structures, which may be groove structures or protruding ridge structures. For example Figure 11 In the example, the choke structure employs a choke slot 240. The choke slot 240 is recessed inward from the top surface of the metal body 200, and its length direction is parallel to the length direction of the waveguide cavity 100. Multiple choke slots 240 are spaced apart and located on both sides of the antenna radiation aperture 230. The choke slot 240 can suppress the passage of electromagnetic waves. For example, in one example, the depth of the choke slot 240 is approximately 1 / 4 of the free-space wavelength of millimeter waves. By fine-tuning the depth of the choke slot, the current distribution near the antenna can be fine-tuned. For example, the depth of the choke slot 240 can be set to 0.28 times the free-space wavelength of air. Figure 11 In the example, the top surface of the metal body 200 is provided with a total of 4 choke slots 240. The 4 choke slots 240 are located on both sides of the antenna radiation hole 230 in pairs, and the length of the choke slots 240 covers all the antenna radiation holes 230.

[0099] In the above embodiments, the waveguide antenna is end-fed, meaning the feeding cavity is located at one end of the waveguide cavity, allowing electromagnetic waves to propagate unidirectionally within the waveguide cavity. In other embodiments, a center-fed method can also be used, where electromagnetic waves enter from the middle of the waveguide cavity 100 and then radiate towards both ends. The following describes a similar approach. Figure 13 and Figure 14 Please provide an explanation.

[0100] See Figure 13 and Figure 14 For example, structures identical to those described in the previous embodiments will not be repeated here. The main difference between this example and the previous example is that the feeding cavity 130 is connected to the middle of one narrow wall of the waveguide cavity 100. In this way, electromagnetic waves no longer enter from one end of the waveguide cavity 100 along its length and propagate unidirectionally to the other end, but instead enter from the middle of the waveguide cavity 100 and propagate to both ends along its length.

[0101] In this example, the waveguide cavity 100 is symmetrically divided into two parts along its length from the position of the feed cavity 130. See also... Figure 13 As shown in (b), for the left half of the waveguide cavity 100, electromagnetic waves enter the waveguide cavity 100 from the middle feed cavity 130 and then propagate towards the left end, exciting the two radiation slots 110 located in the left half to generate radiated energy. Similarly, for the right half of the waveguide cavity 100, electromagnetic waves enter the waveguide cavity 100 from the middle feed cavity 130 and then propagate towards the right end, exciting the two radiation slots 110 located in the right half to generate radiated energy.

[0102] In other words, Figure 13 In the example, it is equivalent to having two sets of symmetrical sub-antennas, each set of sub-antennas including two radiation slots. In order to keep the phase of the radiation slots of the two sets of sub-antennas consistent, it is necessary to ensure that the phase of the two radiation slots of each set is consistent.

[0103] For example Figure 13 As shown in (b), in the waveguide cavity located in the left half of the feed cavity 130, the bias cavity 120a corresponding to the first radiation slot and the bias cavity 120b corresponding to the second radiation slot are alternately arranged on the narrow walls on both sides. In the waveguide cavity located in the right half of the feed cavity 130, the bias cavity 120c corresponding to the third radiation slot and the bias cavity 120d corresponding to the fourth radiation slot are alternately arranged on the narrow walls on both sides. As for the bias cavity 120b corresponding to the second radiation slot and the bias cavity 120c corresponding to the third radiation slot, since the electromagnetic wave transmission phases at the two radiation slots are opposite, the bias cavities corresponding to the two need to be set on the same narrow wall.

[0104] In one example, since bias cavity 120b and bias cavity 120c are located on the same narrow wall, they can be connected to form a single structure, thereby reducing the difficulty of manufacturing. Of course, those skilled in the art will understand that they can also be used as separate structures, and this specification does not limit this.

[0105] It is worth noting that the above Figure 13 The bias cavity arrangement in the implementation method is the same as described above. Figure 12 The bias arrangement in the end-feeding schemes of the embodiments is essentially the same. Both use bias cavities to ensure that the surface current direction is consistent at the location of each gap, thereby achieving compensation for the radiation phase. The only difference is that with end-feeding, the electromagnetic wave propagates unidirectionally, and the bias cavities can be alternated sequentially in one direction; while with middle-feeding, the electromagnetic wave propagates bidirectionally, and the bias cavities need to be arranged symmetrically about the feeding position to ensure that the radiation phase of the gaps on the left and right sides is the same. Both of the above arrangement methods are equivalent implementation schemes of the technical concept of this specification.

[0106] Continue to refer to Figure 13 As shown, the feeding cavity 130 includes a polarization direction switching unit 131 and a tuning element 132. In this example, in addition to the tuning element 132a disposed inside the polarization direction switching unit 131, the tuning element 132 may also include a tuning element 132b disposed inside the waveguide cavity 100 and located at the middle of the length direction of the waveguide cavity 100.

[0107] In one example, the tuner 132b is positioned near the connection between the feed cavity 130 and the waveguide cavity 100 to adjust the impedance matching at the feed port. After electromagnetic waves enter the waveguide cavity 100 from the feed cavity 130, they need to be split in two directions, left and right. This bifurcation structure causes impedance discontinuity at the feed point, resulting in reflected waves and affecting the port VSWR. By setting the tuner 132b and adjusting its size and position within the waveguide cavity 100, a compensating reactance can be introduced to counteract the reflections caused by the bifurcation structure, reducing the VSWR at the feed point and improving electromagnetic wave transmission efficiency.

[0108] In some embodiments, the tuning element 132b may be made of metal and may be cylindrical, blocky or sheet-like in shape, protruding from the wide or narrow side surface of the waveguide cavity 100 into the cavity. Its specific size and position are determined by simulation and debugging, and will not be described in detail in this specification.

[0109] Figure 14 It shows Figure 13 The metallic structure of the waveguide antenna corresponding to the implementation method can be understood and fully implemented by those skilled in the art in conjunction with the foregoing, and will not be described in detail here.

[0110] As described above, in the embodiments of this specification, by utilizing the bias cavity set on the narrow side of the waveguide cavity, the zero point of the current on the waveguide surface can be deviated from the centerline of the wide side. The radiating slots, positioned at the centerline, can also effectively cut the current to generate radiated energy. Therefore, the radiating slots can be arranged along the centerline of the wide side of the waveguide, reducing the difficulty of waveguide antenna design, simulation, and fabrication. Furthermore, it alleviates the problem of radiation pattern distortion caused by slot offset, effectively improving the performance of the waveguide antenna. In addition, by setting the bias cavity structure with functional sections and transition sections, reflected waves can be effectively reduced, increasing the antenna radiation gain. Moreover, the waveguide cavity can be applied to various antenna structures such as end-fed and center-fed, offering greater flexibility.

[0111] In some embodiments, this specification also provides a radar antenna that can be used in a vehicle-mounted millimeter-wave radar system.

[0112] For example, see one example. Figure 15 As shown, the radar antenna includes a waveguide antenna array, which includes an upper array structure formed on the upper metal body 210 and a lower array structure formed on the lower metal body 220. When the upper metal body 210 and the lower metal body 220 are assembled as one unit, the upper array structure and the lower array structure are combined to form a waveguide antenna array.

[0113] The waveguide antenna array includes multiple waveguide antennas, which include waveguide antennas according to any of the above embodiments. The multiple waveguide antennas are arranged in an array along a horizontal direction, and each waveguide antenna is connected to the radio frequency front-end circuit via a feed waveguide. In operation, the radio frequency front-end circuit generates electromagnetic wave signals in the millimeter-wave band, which are transmitted to the corresponding waveguide antennas via the feed waveguides. In each waveguide antenna, the electromagnetic wave enters the polarization direction conversion unit 131 through the feed cavity 130 for polarization direction conversion, and is then sent into the waveguide cavity 100. The electromagnetic wave energy is radiated outward from each radiation slot through the antenna radiation aperture 230. The radiated beams of the multiple waveguide antennas are combined in space to form an antenna pattern with high gain and a predetermined direction.

[0114] By using the above-mentioned waveguide antenna array arrangement, the overall gain and angular resolution of the radar antenna can be further improved, meeting the needs of vehicle-mounted millimeter-wave radar for long-range detection and high-precision target identification.

[0115] As described above, in the embodiments of this specification, by utilizing the bias cavity set on the narrow side of the waveguide cavity, the zero point of the waveguide surface current can be deviated from the centerline of the wide side. The radiating slot, positioned at the centerline, can also effectively cut the current to generate radiated energy. Therefore, it is advantageous to design the radiating slot along the centerline of the wide side of the waveguide, reducing the difficulty of waveguide antenna design, simulation, and fabrication. Furthermore, it alleviates the problem of radiation pattern distortion caused by slot offset, effectively improving the performance of the waveguide antenna. Moreover, it can effectively reduce the size in the wide side direction, which is beneficial for the miniaturization design of the waveguide antenna in the wide side direction. In addition, by setting the bias cavity structure of functional segments and transition segments, reflected waves can be effectively reduced, and antenna radiation gain can be improved. Furthermore, the waveguide cavity can be applied to various antenna structures such as end-fed and center-fed, offering greater flexibility.

[0116] Obviously, the above embodiments are merely examples for clear illustration and are not intended to limit the embodiments. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all embodiments here. However, obvious variations or modifications derived therefrom remain within the scope of protection created by this specification.

Claims

1. A waveguide structure, characterized in that, The waveguide structure includes a waveguide cavity located inside a metal body, the waveguide cavity including a wide side and a narrow side; Multiple radiation slots are provided along the length of the wide side surface of the waveguide cavity; On one side of the narrow side corresponding to each radiation slot, a bias cavity is provided along the surface of the narrow side and toward the side opposite to the surface of the wide side. The bias cavity causes the zero point of the surface current of the waveguide cavity to deviate from the center line of the wide side. The bias cavities corresponding to two adjacent radiation slots are located on opposite narrow sides of the waveguide cavity.

2. The waveguide structure according to claim 1, characterized in that, The plurality of radial slits are located on the center line of the wide side and are spaced apart along the center line of the wide side.

3. The waveguide structure according to claim 1, characterized in that, The first dimension of the bias cavity along the length direction is larger than the second dimension of the radiation slit along the length direction; And / or, The first dimension of the bias cavity along its length is equal to or approximately equal to half the wavelength of the waveguide, and the second dimension of the radiation slit along its length is equal to or approximately equal to half the wavelength of free space.

4. The waveguide structure according to any one of claims 1 to 3, characterized in that, The bias cavity includes a functional segment extending along the narrow side surface toward a side opposite to the wide side surface, and a transition segment is provided on at least one side of the functional segment along the length direction. The transition segment forms a chamfer structure to connect the side of the functional segment with the waveguide cavity. The chamfered structure formed by the transition section includes a planar chamfered structure or an arc-shaped chamfered structure.

5. A waveguide slot antenna, characterized in that, It includes a metal body and a waveguide cavity and a feeding cavity formed inside the metal body, the waveguide cavity having a waveguide structure as described in any one of claims 1 to 4; The metal body includes a top surface extending in a horizontal direction, and the metal body has an antenna radiation hole extending from the radiation slot to the top surface corresponding to the position of each radiation slot. The first end of the feeding cavity is connected to the feeding waveguide, and the second end is connected to the waveguide cavity. The feeding cavity is used to transmit the electromagnetic waves input by the feeding waveguide to the waveguide cavity to excite each radiation slot to radiate signals outward.

6. The waveguide slot antenna according to claim 5, characterized in that, The feeding cavity includes a polarization direction conversion unit, which is used to configure the electromagnetic wave input from the feeding waveguide in the first polarization direction to a second polarization direction orthogonal to the first polarization direction. And / or, The waveguide antenna further includes at least one tuning element, which is disposed in the feed cavity and / or the waveguide cavity, and the tuning element is used to adjust the equivalent impedance in the feed cavity and / or the waveguide cavity.

7. The waveguide slot antenna according to claim 5, characterized in that, The second end of the feeding cavity is connected to one side of the waveguide cavity along its length. In the waveguide cavity, the bias cavities corresponding to any two adjacent radiation slots are located on opposite narrow sides of the waveguide cavity.

8. The waveguide slot antenna according to claim 5, characterized in that, The second end of the feeding cavity is connected to the middle of the narrow side surface of one side of the waveguide cavity, and the waveguide cavity includes a plurality of radiation slots that are symmetrically arranged on both sides of the feeding cavity. In a local waveguide cavity located on any side of the feeding cavity, the bias cavities corresponding to two adjacent radiation slots are located on the narrow sides of the waveguide cavity on opposite sides, respectively. The bias cavities corresponding to two adjacent symmetrical radiation slots close to the feed cavity are located on the same narrow side of the waveguide cavity.

9. The waveguide slot antenna according to claims 5 to 8, characterized in that, The antenna radiating aperture includes an antenna port and an antenna opening. The antenna port is connected to the radiating slot, and the antenna opening is connected to the antenna port. The size of the antenna opening gradually increases from the connecting end to the top surface. And / or, The top surface is provided with multiple choke structures. The choke structures are recessed from the top surface of the metal body and their length direction is parallel to the length direction of the waveguide cavity. The multiple choke structures are arranged at intervals and are respectively located on both sides of the antenna radiation hole.

10. A radar antenna, characterized in that, The device includes a waveguide antenna array, which comprises a plurality of waveguide slot antennas, wherein the waveguide slot antennas include the waveguide antennas according to any one of claims 5 to 9.

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