A broadband millimeter-wave circularly polarized open waveguide antenna

Abstract

The present invention discloses a broadband millimeter-wave circularly polarized open waveguide antenna. The array antenna includes an E-plane feed waveguide wrapped by an external metal, an E-plane waveguide impedance transformer, a waveguide radiation unit, and two radiation slots. The E-plane feed waveguide includes an input port and an output port, and the output port is connected to the E-plane waveguide impedance transformer. The output end of the E-plane waveguide impedance transformer is connected to the wider side wall of the waveguide radiation unit. The upper part of the waveguide radiation unit is open to form a radiation aperture. Two radiation slots are respectively loaded on the two wider side walls of the waveguide radiation unit. Electromagnetic waves are input from the E-plane feed waveguide to the waveguide radiation unit via the E-plane waveguide impedance transformer, and then radiated outward by the radiation aperture and the radiation slots. The present invention simultaneously has the advantages of single-layer circular polarization realizability, low loss, wide impedance bandwidth, wide axial ratio bandwidth, easy array construction, and low cost, etc.

Description

Technical Field

[0001] The present invention belongs to the field of millimeter-wave antennas, and particularly relates to a broadband millimeter-wave circularly polarized open waveguide antenna. Background Art

[0002] Circularly polarized antennas have received extensive attention in various wireless systems. It has three advantages: a circularly polarized antenna can receive incoming waves of any polarization, and its radiated waves can also be received by any polarized antenna; circularly polarized antennas have spin orthogonality; when a polarized wave is incident on a symmetric object, the spin is reversed, and electromagnetic waves of different spins have a large numerical polarization isolation. There have been many studies on the circular polarization performance of antennas. From the perspective of the number of feed ports, it can be divided into single-port and dual-port structures. For a dual-port circularly polarized antenna, generally, two ports are used to excite orthogonal electric field components with equal amplitudes but a phase difference of 90° to achieve circular polarization performance. However, in practical applications, for simplicity, single-feed structures are widely used. For example, a patch antenna fed by a microstrip line achieves circular polarization performance by changing the shape to a square loop or cutting an inclined slot at the center of the patch. However, the axial ratio (AR) bandwidth of these antennas is not wide enough, and the gain is not high due to dielectric losses. Some circularly polarized antennas use crossed dipoles as antenna elements. Generally, the gain of this type of antenna is low, so methods such as adding artificial magnetic conductors are needed to increase the gain. Couplers are usually used in the feed layer of circularly polarized coupled antennas to provide the required excitation amplitude and phase. In these structures, the upper-layer elements and the lower-layer couplers need to be designed separately, and the design process is relatively complex. In addition, substrate integrated waveguide technology can also be used for circularly polarized antennas.

[0003] To more easily excite orthogonal electric fields, many structures use L-shaped probes when designing antenna elements to achieve circular polarization performance. However, for the antenna structure fed by an L-shaped probe, it is difficult to further construct a single-port low-loss array. In addition to the above research on waveguide antennas with L-shaped probes, other studies such as conical slot antennas, open circular waveguides with stubs, combinations of open rectangular waveguides and open-loop resonators, horn antennas with conical elliptical waveguides, and circularly polarized slot waveguide antennas have also been proposed.

[0004] Although these waveguide structures have the advantage of low loss, some of them have problems such as insufficient impedance bandwidth and axial ratio bandwidth, and some have problems such as difficulty in constructing an antenna array that is easy to integrate and has low loss. Summary of the Invention

[0005] The object of the present invention is to provide a broadband millimeter-wave circularly polarized open waveguide antenna for the problems existing in the above-mentioned prior art.

[0006] The technical solution for achieving the object of the present invention is as follows: A broadband millimeter-wave circularly polarized open waveguide antenna, which includes an E-plane feeding waveguide wrapped by an external metal, an E-plane waveguide impedance transformer, a waveguide radiation unit with a rectangular cross-section, and two radiation slots; the E-plane feeding waveguide includes an input port and an output port, and the output port is connected to the E-plane waveguide impedance transformer; the output end of the E-plane waveguide impedance transformer is connected to a long-side sidewall of the waveguide radiation unit; the upper part of the waveguide radiation unit is open to form a radiation aperture; the first radiation slot and the second radiation slot are respectively loaded on the sidewalls of the two long sides of the waveguide radiation unit, wherein the first radiation slot is on the opposite side of the E-plane feeding waveguide and deviates from the center of the waveguide radiation unit by a certain position along the direction close to the E-plane feeding waveguide of the waveguide, and the second radiation slot is on the same side of the E-plane feeding waveguide and deviates from the center of the waveguide radiation unit by a certain position along the direction away from the E-plane feeding waveguide; electromagnetic waves are input from the E-plane feeding waveguide through the E-plane waveguide impedance transformer into the waveguide radiation unit, and then radiated outward through the radiation aperture and the radiation slots.

[0007] Further, on both sides of the intersection position of the waveguide radiation unit and the second radiation slot, it is recessed inward to form a waveguide impedance transformer, and the shape of the recessed part is a cuboid with the same height as the waveguide radiation unit.

[0008] Further, the position of the second radiation slot relative to the recessed part is adjustable, and the loading position of the second radiation slot moves with the recess of the waveguide radiation unit.

[0009] Further, a reference plane xoy is established on the horizontal plane. The waveguide wide surface of the E-plane feeding waveguide is perpendicular to the reference plane xoy, and the waveguide narrow surface is parallel to the reference plane xoy; similarly, the waveguide wide surface of the E-plane waveguide impedance transformer is also perpendicular to the reference plane xoy, and the waveguide narrow surface is also parallel to the reference plane xoy, and the waveguide height is equal to the height h of the E-plane feeding waveguide, and the value of h is between half a wavelength and one wavelength; the waveguide wide surface of the E-plane waveguide impedance transformer and the waveguide radiation unit are perpendicular to each other and the intersection surface is perpendicular to the reference plane xoy.

[0010] Further, the radiation aperture exceeds the heights of the E-plane feeding waveguide and the E-plane waveguide impedance transformer by d. The width and length of the radiation aperture are L and W respectively. The height d and the cross-sectional dimensions L and W together form the upper aperture part, where W > L, and the value of W is between half a wavelength and one wavelength; the width of the remaining cavity part of the waveguide radiation unit excluding the aperture part is L, and the length is W 1 , W 1 <W.

[0011] Further, the first radiation slot and the second radiation slot are of cuboid or "L" type structure.

[0012] Furthermore, the feeding end of the antenna, i.e., the input end of the E-plane feeding waveguide, adopts waveguide feeding or coaxial-to-waveguide feeding.

[0013] Furthermore, the antenna can be laterally expanded through the E-plane parallel feeding waveguide feeding network to form a one-dimensional multi-element array.

[0014] Compared with the prior art, the remarkable advantages of the present invention are as follows:

[0015] (1) The present invention realizes the circular polarization performance with a wide axial ratio. Both the axial ratio bandwidth and the impedance bandwidth exceed those of most other technologies.

[0016] (2) Compared with the prior art, the present invention can be laterally expanded through the E-plane parallel feeding waveguide feeding network, making it easier to construct a low-loss array.

[0017] (3) The present invention can adopt traditional machining, which not only avoids complex processing techniques, has a low cost, but also does not affect the internal field distribution of the waveguide, thus there is no electromagnetic wave leakage.

[0018] (4) The present invention simultaneously has the advantages of single-layer circular polarization realization, low loss, wide impedance bandwidth, wide axial ratio bandwidth, easy array construction and low cost.

[0019] (5) As a basic structure, the present invention can achieve different forms and different degrees of extended innovation on its basis, and has a wide application prospect.

[0020] (6) The present invention can be applicable to different frequency bands within a certain range.

[0021] The present invention will be further described in detail below with reference to the accompanying drawings. Description of the Drawings

[0022] Figure 1 It is a perspective three-dimensional view of Embodiment 1.

[0023] Figure 2 It is a front view plan view of Embodiment 1.

[0024] Figure 3 It is a front view plan view of an alternative scheme of Embodiment 1.

[0025] Figure 4 It is a top view plan view of Embodiment 1.

[0026] Figure 5 It is a perspective view of the overall structure of Embodiment 1 with the feeding structure added.

[0027] Figure 6 It is a simulation diagram of the reflection coefficient of Embodiment 1.

[0028] Figure 7 It is a simulation diagram of the axial ratio of Embodiment 1.

[0029] Figure 8 The simulation diagram of the circular polarization gain varying with frequency for Embodiment 1.

[0030] Figure 9 The far - field simulation pattern of Embodiment 1 at 28 GHz.

[0031] Figure 10 The far - field simulation pattern of Embodiment 1 at 38 GHz.

[0032] Figure 11 The top - view plan view of Embodiment 2. Specific implementation manners

[0033] In order to make the objectives, technical solutions and advantages of the present application more clear and understandable, the following further describes the present application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0034] It should be noted that if there are directional indications (such as up, down, left, right, front, back,...) involved in the embodiments of the present invention, the directional indications are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly.

[0035] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0036] In one embodiment, in combination with Figures 1 to 4, the present invention provides a broadband millimeter-wave circularly polarized open waveguide antenna, which includes an E-plane feeding waveguide 2 wrapped by an external metal 1, an E-plane waveguide impedance transformer 3, a waveguide radiation unit 4, and two radiation slots 5; the E-plane feeding waveguide 2 includes an input port and an output port, and the output port is connected to the E-plane waveguide impedance transformer 3; the output end of the E-plane waveguide impedance transformer 3 is connected to a long-side side wall of the waveguide radiation unit 4; the upper part of the waveguide radiation unit 4 is open to form a radiation aperture 6; a first radiation slot 5-1 and a second radiation slot 5-2 are respectively loaded on the side walls of two long sides of the waveguide radiation unit 4, wherein the first radiation slot 5-1 is on the side opposite to the E-plane feeding waveguide 2 and deviates from the center of the waveguide radiation unit 4 by a certain position along the direction close to the E-plane feeding waveguide 2, and the second radiation slot 5-2 is on the same side as the E-plane feeding waveguide 2 and deviates from the center of the waveguide radiation unit 4 by a certain position along the direction away from the E-plane feeding waveguide 2; electromagnetic waves are input from the E-plane feeding waveguide 2 to the waveguide radiation unit 4 via the E-plane waveguide impedance transformer 3, and then radiated outward by the radiation aperture 6 and the radiation slots 5.

[0037] Here, the external metal can be selected from pure metals such as aluminum or copper.

[0038] Further, in one embodiment, the positions on both sides of the intersection of the waveguide radiation unit 4 and the second radiation slot 5-2 are recessed inward to form a waveguide impedance transformer, and the shape of the recessed part is a cuboid that is the same height as the waveguide radiation unit 4. The position of the second radiation slot 5-2 relative to the recessed part is adjustable, and the loading position of the second radiation slot 5-2 moves with the recess of the waveguide radiation unit 4.

[0039] Here, the form of adjusting impedance matching is based on the matching window in waveguide theory, which neither occupies extra space nor can achieve better impedance matching; however, there are still more adjustment and matching methods available for use.

[0040] Here, preferably, both the first radiation slot 5-1 and the second radiation slot 5-2 are cuboids, and at the same time, the first radiation slot 5-1 and the second radiation slot 5-2 can also be bent into an "L" shape to save the occupied space.

[0041] Further, in one embodiment, a reference plane xoy is established on the horizontal plane, the waveguide wide face of the E-plane feeding waveguide 2 is perpendicular to the reference plane xoy, and the waveguide narrow face is parallel to the reference plane xoy; similarly, the waveguide wide face of the E-plane waveguide impedance transformer 3 is also perpendicular to the reference plane xoy, and the waveguide narrow face is also parallel to the reference plane xoy, and the waveguide height is equal to the height h of the E-plane feeding waveguide 2, and the value of h ranges from half a wavelength to one wavelength; the waveguide wide face of the E-plane waveguide impedance transformer 3 and the waveguide radiation unit 4 are perpendicular to each other and the intersection plane is perpendicular to the reference plane xoy.

[0042] Here, the height of the radiation aperture 6 exceeding the E-plane feed waveguide 2 and the E-plane waveguide impedance transformer 3 is set to d. The radiation aperture size parameters are L and W. The height d and the cross-sectional dimensions L and W together form the aperture part 7 of the upper layer, where W > L, and the value of W ranges from half a wavelength to one wavelength. The remaining cavity part 8 of the waveguide radiation unit 4 excluding the aperture part 7 has the same width L as the aperture part 7 but a different length W 1 , where, W 1 < W.

[0043] Here, the remaining cavity part 8 is selected to have a different width from the aperture part 7 to change the lower cavity size of the waveguide radiation unit 4, thereby adjusting the position of the resonance point to increase the impedance bandwidth; in addition to changing the value of W 1 , structures such as "ridges" can also be added inside the remaining cavity part 8 to adjust the cavity size to achieve the same effect.

[0044] Furthermore, in one of the embodiments, the feed end of the broadband millimeter-wave circularly polarized open waveguide antenna can be diversified, and waveguide feeding or coaxial-to-waveguide feeding and other methods can be adopted.

[0045] Here, coaxial waveguide conversion method 9 is used for feeding at the input end of the E-plane feed waveguide 2.

[0046] Furthermore, in one of the embodiments, the broadband millimeter-wave circularly polarized open waveguide antenna can be laterally expanded through the E-plane parallel-feed waveguide feeding network 12 to form a one-dimensional multi-unit array.

[0047] As a specific example, the broadband millimeter-wave circularly polarized open waveguide antenna that can be realized in a single layer of the present invention is further verified and described.

[0048] In this example, Embodiment 1 is provided as Figures 1 to 5As shown, the broadband millimeter-wave circularly polarized open waveguide antenna includes an E-plane feeding waveguide 2, an E-plane waveguide impedance transformer 3, a waveguide radiation unit 4, and two radiation slots 5 wrapped by an external metal 1; the E-plane feeding waveguide 2 includes an input port and an output port, and the output port is connected to the E-plane waveguide impedance transformer 3; the output end of the E-plane waveguide impedance transformer 3 is connected to the wider sidewall of the waveguide radiation unit 4; the upper part of the waveguide radiation unit 4 is open to form a radiation aperture 6; the first radiation slot 5-1 and the second radiation slot 5-2 are respectively loaded on the two wider sidewalls of the waveguide radiation unit 4; the first radiation slot 5-1 is on the opposite side of the E-plane feeding waveguide 2 and deviates from the unit center by a certain position along the direction close to the E-plane feeding waveguide 2; the second radiation slot 5-2 is on the same side of the E-plane feeding waveguide 2 and deviates from the unit center by a certain position along the direction away from the E-plane feeding waveguide 2; the waveguide radiation unit 4 is recessed inward at the position where it intersects with the second radiation slot 5-2, and the shape of the recessed part is a cuboid with the same height as the waveguide radiation unit 4, and its corresponding length and width are m and n respectively; the loading position of the second radiation slot 5-2 moves with the recess of the waveguide radiation unit 4; the position of the second radiation slot 5-2 relative to the recessed part is adjustable; electromagnetic waves are input from the E-plane feeding waveguide 2 to the waveguide radiation unit 4 via the E-plane waveguide impedance transformer 3, and then radiated outward by the radiation aperture 6 and the radiation slots 5. Here, the external metal can be selected from pure metals such as aluminum or copper.

[0049] Combined with Figure 1 , a reference plane xoy is established on the horizontal plane. The waveguide wide surface of the E-plane feeding waveguide 2 is perpendicular to the reference plane xoy, and the waveguide narrow surface is parallel to the reference plane xoy; similarly, the waveguide wide surface of the E-plane waveguide impedance transformer 3 is also perpendicular to the reference plane xoy, and the waveguide narrow surface is also parallel to the reference plane xoy, and the waveguide height is equal to the height h of the E-plane feeding waveguide 2, and the value of h is between half a wavelength and one wavelength; the input end of the E-plane waveguide impedance transformer 3 is connected to the input end of the E-plane feeding waveguide 2; in this embodiment, a rectangular waveguide radiation unit is selected, and the sidewall where the longer side of the waveguide radiation unit 4 is located is connected to the output end of the E-plane waveguide impedance transformer 3, and their waveguide wide surfaces are perpendicular to each other and the intersection surface is perpendicular to the reference plane xoy. Combined with Figure 2 , the radiation aperture 6 exceeds the heights of the E-plane feeding waveguide 2 and the E-plane waveguide impedance transformer 3 and is set as d. The radiation aperture size parameters are L and W. The height d and the cross-sectional dimensions L and W together constitute the upper aperture part 7, where W > L, and the value of W is between half a wavelength and one wavelength. The remaining cavity part 8 of the waveguide radiation unit 4 excluding the aperture part 7 has the same width L as the aperture part 7 but different length W 1 , where, W 1<W. Here, the remaining cavity part 8 is selected to have a different width from the aperture part 7 in order to change the lower cavity size of the waveguide radiation unit 4, thereby adjusting the position of the resonance point to increase the impedance bandwidth; combined with Figure 3 , in addition to changing the value of W 1 , structures such as "ridges" can also be added inside the remaining cavity part 8 to adjust the cavity size to achieve the same effect.

[0050] Combined with Figure 4 , select the other sidewall of the waveguide radiation unit 4 that is wider and on the opposite side of the E-plane feeding waveguide 2, and load the first radiation slot 5-1 at a position deviated from the unit center by l offsEt1 along the direction close to the waveguide E-plane feeding waveguide 2; the first radiation slot 5-1 extends outward by a length of l s1 and extends downward by a depth of h s1 , and its width is w s1 ; select the sidewall of the waveguide radiation unit 4 that is wider and on the same side as the E-plane feeding waveguide 2, and load the second radiation slot 5-2 at a position deviated from the unit center by l offsEt2 along the direction away from the waveguide E-plane feeding waveguide 2. The second radiation slot 5-2 is opposite to the deviation direction of the first radiation slot 5-1, extends outward by a length of l s1 , extends downward by a certain depth of h s1 , and its width is w s2 . Both the first radiation slot 5-1 and the second radiation slot 5-2 are rectangular parallelepipeds. At the same time, the first radiation slot 5-1 and the second radiation slot 5-2 can also be bent into an "L" shape to save the occupied space; after the radiation slot 5 is bent, the transverse part plays a role in guiding the current, thereby further enhancing the field strength at the longitudinal slot.

[0051] The waveguide radiation unit 4 is recessed inward at the position where it intersects with the second radiation slot 5-2, and the shape of the recess is a rectangular parallelepiped that is consistent with the height of the waveguide radiation unit 4; the loading position of the second radiation slot 5-2 moves with the recess of the waveguide radiation unit 4; the position of the second radiation slot 5-2 relative to the recessed part is adjustable, so as to achieve impedance matching after loading the second radiation slot 5-2. Combined with Figure 4 , the length and width of the recessed part are m and n. Here, the form of adjusting impedance matching is based on the matching window in waveguide theory, which neither occupies extra space nor can achieve better impedance matching; however, there are still many other adjustment and matching methods available for use.

[0052] The feeding end of the single-layer broadband millimeter-wave circularly polarized aperture waveguide antenna can be diversified, and waveguide feeding or coaxial-to-waveguide feeding can be adopted. Combined with Figure 5, the input end of the E-plane feeding waveguide 2 of the present invention is fed by a coaxial waveguide conversion method 9. The E-plane feeding waveguide 2 and the coaxial probe 10 are connected through another E-plane waveguide impedance transformer 11 to achieve better impedance matching.

[0053] According to the above embodiment, during the processing of the present invention, it can be divided into upper and lower plate machining from the longitudinal middle height. The present invention does not need to use the relatively expensive lamination diffusion bonding technology to solve the electrical contact problem. Since the feeding part uses an E-plane waveguide, the longitudinal middle height of the antenna corresponds to the center line of the wide side of the waveguide. Based on this, the entire structure is divided into two parts up and down. The dividing line neither affects the field distribution nor cuts the waveguide wall current, so it will not cause electromagnetic leakage. At the same time, the cost is low and it is easy to process. In addition, 3D printing technology can also be used for this solution;

[0054] In the embodiment 1, the values of L and W of the aperture part 7 of the waveguide radiation unit 4 are 3.8 mm and 5.7 mm respectively, the height d of the aperture part 7 is 0.25 mm, the width of the remaining cavity part 8 is the same as that of the aperture part 7, and the length W 1 The value is 5.2 mm; the length and width m and n of the cut-off waveguide impedance transformer 9 are 3.5 mm and 0.8 mm respectively; the length l s1 , width w s1 , depth h s1 and offset position l offsEt1 are 2.3 mm, 1.2 mm, 2.35 mm and 1.6 mm respectively; the length l s2 , width w s2 , depth h s2 and offset position l offsEt2 of the radiation slot 5-2 are 3.2 mm, 1.4 mm, 4.8 mm and 0.25 mm respectively; the height h of the E-plane feeding waveguide 2 and the E-plane waveguide impedance transformer 3 is 6.3 mm, and this value can be further optimized and adjusted within the range of half wavelength to one wavelength. The widths of the E-plane feeding waveguide 2 and the E-plane waveguide converter 3 are 1.3 mm and 0.8 mm respectively; the antenna is fed by a coaxial probe to waveguide method. The coaxial probe 10 of the feeding structure 9 is first connected to the E-plane waveguide impedance transformer 11 and then to the E-plane feeding waveguide 2. The diameter of the probe is 0.64 mm, the diameter of the external medium is 1.28 mm, the length of the probe extending into the E-plane waveguide impedance transformer 11 is 0.89 mm, and the width of the E-plane waveguide impedance transformer 11 is 1 mm.

[0055] Figure 6 The reflection coefficient simulation diagram of the example embodiment 1 is given. It can be seen from the figure that the relative bandwidth less than -10 dB is 50%, showing broadband characteristics.

[0056] Figure 7 The axial ratio simulation diagram of Example 1 of this embodiment is given. It can be seen that the axial ratio range less than 3 dB covers the frequency from 24.9 GHz to 40 GHz, with an axial ratio bandwidth of 47%.

[0057] Figure 8 The simulation curve of the actual gain of Example 1 changing with frequency is shown. It can be seen that within the entire frequency band from 24 GHz to 40 GHz, the actual gain of the antenna is above 6 dBic; taking the frequencies of 28 GHz and 38 GHz as examples, the actual gains obtained by simulation are 6.7 dBic and 6.9 dBic.

[0058] In addition, Figure 9 and Figure 10 are the far - field patterns in the E - plane and H - plane at 28 GHz and 38 GHz for Example 1.

[0059] When Example 1 is laterally expanded in a single layer according to the same rule, a one - dimensional array antenna with the number of elements being a multiple of 2 can be obtained. This example provides Example 2 - a 1×4 wide - axial - ratio circularly polarized array obtained by lateral expansion, as Figure 11 shown. The array antenna can adopt different feeding methods such as waveguide feeding or coaxial - to - waveguide feeding. In this Example 2, the coaxial - to - waveguide feeding method is adopted. The electromagnetic wave is transmitted from the input end of the E - plane waveguide feeding network 12 to each waveguide radiation unit 4 and radiates outward. This array antenna operates in the TE 10 mode and satisfies single - mode transmission.

[0060] In summary, the present invention has the advantages of single - layer circular polarization realization, low loss, wide impedance bandwidth, wide axial - ratio bandwidth, easy array construction, and low cost.

[0061] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above - mentioned embodiments. What is described in the above - mentioned embodiments and the specification only illustrates the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A broadband millimeter-wave circularly polarized open waveguide antenna, characterized in that, the antenna comprises an E-plane feeding waveguide (2) wrapped by an external metal (1), an E-plane waveguide impedance transformer (3), a waveguide radiation unit (4) with a rectangular cross-section, and two radiation slots (5); the E-plane feeding waveguide (2) includes an input port and an output port, and the output port is connected to the E-plane waveguide impedance transformer (3); the output end of the E-plane waveguide impedance transformer (3) is connected to a long-side side wall of the waveguide radiation unit (4); the upper part of the waveguide radiation unit (4) is open to form a radiation aperture (6); a first radiation slot (5-1) and a second radiation slot (5-2) are respectively loaded on the side walls of two long sides of the waveguide radiation unit (4), wherein the first radiation slot (5-1) is on the side opposite to the E-plane feeding waveguide (2) and deviates from the center of the waveguide radiation unit (4) by a certain position along the direction close to the E-plane feeding waveguide (2), and the second radiation slot (5-2) is on the same side as the E-plane feeding waveguide (2) and deviates from the center of the waveguide radiation unit (4) by a certain position along the direction away from the E-plane feeding waveguide (2); electromagnetic waves are input from the E-plane feeding waveguide (2) to the waveguide radiation unit (4) via the E-plane waveguide impedance transformer (3), and then radiated outward by the radiation aperture (6) and the radiation slots (5); both sides of the intersection position of the waveguide radiation unit (4) and the second radiation slot (5-2) are recessed inward to form a waveguide impedance transformer, and the shape of the recessed part is a cuboid with the same height as the waveguide radiation unit (4).

2. The broadband millimeter-wave circularly polarized open waveguide antenna according to claim 1, characterized in that, the position of the second radiation slot (5-2) relative to the recessed part is adjustable, and the loading position of the second radiation slot (5-2) moves along with the recess of the waveguide radiation unit (4).

3. The broadband millimeter-wave circularly polarized open waveguide antenna according to claim 1, characterized in that, a reference plane xoy is established on the horizontal plane, the waveguide wide surface of the E-plane feeding waveguide (2) is perpendicular to the reference plane xoy, and the waveguide narrow surface is parallel to the reference plane xoy; similarly, the waveguide wide surface of the E-plane waveguide impedance transformer (3) is also perpendicular to the reference plane xoy, and the waveguide narrow surface is also parallel to the reference plane xoy, and the waveguide height is equal to the height h of the E-plane feeding waveguide (2), and the value of h ranges from half a wavelength to one wavelength; the waveguide wide surface of the E-plane waveguide impedance transformer (3) is perpendicular to the waveguide wide surface of the waveguide radiation unit (4), and the intersection surface is perpendicular to the reference plane xoy.

4. The broadband millimeter-wave circularly polarized open waveguide antenna according to claim 1, characterized in that, The radiation aperture (6) exceeds the height of the E-plane feed waveguide (2) and the E-plane waveguide impedance transformer (3) by d. The width and length of the radiation aperture are L and W respectively. The height d, and the cross-sectional dimensions L and W together constitute the upper aperture part (7), where W > L, and the value of W ranges from half a wavelength to one wavelength; the width of the remaining cavity part (8) of the waveguide radiation unit (4) excluding the aperture part (7) is L, and the length is W 1 , W 1 < W.

5. The broadband millimeter-wave circularly polarized open waveguide antenna according to claim 1, characterized in that, the first radiation slot (5-1) and the second radiation slot (5-2) are of cuboid or "L" type structure.

6. The broadband millimeter-wave circularly polarized open waveguide antenna according to claim 1, characterized in that, the feeding end of the antenna, i.e., the input end of the E-plane feeding waveguide (2), adopts waveguide feeding or coaxial-to-waveguide feeding mode.

7. The broadband millimeter-wave circularly polarized aperture waveguide antenna according to claim 1, characterized in that, the antenna can be laterally extended through an E-plane parallel-fed waveguide feeding network to form a one-dimensional multi-element array.

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