A center-fed single-layer open waveguide antenna

Abstract

This invention discloses a center-fed single-layer open waveguide antenna, comprising an analog PCB board and a waveguide antenna board. A lower open waveguide is disposed on the lower side of the waveguide antenna board, and an upper open waveguide is disposed on the upper side. The lower and upper open waveguides are connected by a through-hole located at the midpoint of the upper open waveguide. Taking the operating frequency band of an automotive millimeter-wave radar as an example, this invention demonstrates feasibility for mass production in the 77GHz operating frequency band.

Description

Technical Field

[0001] This invention relates to a waveguide antenna, and more particularly to a center-fed single-layer open waveguide antenna, belonging to the field of antenna technology. Background Technology

[0002] A single-layer waveguide antenna is an antenna design based on a waveguide structure. Compared to traditional multi-layer or complex antenna structures, it has advantages such as simple structure, low manufacturing cost, and ease of integration. In recent years, with the development of technologies such as 5G / 6G communication, millimeter-wave radar, and satellite communication, single-layer waveguide antennas have attracted widespread attention due to their excellent performance in the high-frequency band.

[0003] Chinese Patent No. CN117941173A discloses an open waveguide antenna and a system having an open waveguide antenna, comprising: an electromagnetic transition section (EM) having a transition region, a signal feed interface, and an open waveguide section; the EM transition section is configured to couple EM energy from the signal feed interface to a guiding waveguide mode of EM energy via the transition region to the open waveguide section; and a leaky waveguide antenna section configured to radiate electromagnetic energy received from the open waveguide section; wherein the EM transition section is electromagnetically coupled to the leaky waveguide antenna section, and the EM transition section is configured to support the transmission of electromagnetic energy from the signal feed structure to the leaky waveguide antenna section. The main innovation of this open waveguide antenna is the EM electromagnetic transition structure, where the waveguide transitions to a PCB transition to an open waveguide antenna. The antenna transition from waveguide to radiating structure requires a turning structure, but the slot of the turning structure is very small and difficult to manufacture, especially in the millimeter-wave band. Furthermore, the waveguide antenna uses a side-fed scheme, resulting in a large variation in the radiation pattern with frequency, leading to an asymmetrical radiation pattern.

[0004] Furthermore, the document "3653054 SYMMETRICAL TROUGH WAVEGUIDE ANTTENNA ARRAY RCACorporation Mar.28.1972 APPL .NP.84821" presents the radiation principle of an open waveguide antenna, but does not consider the antenna's fabrication and implementation, especially in the high-frequency range. The document "AN ELECTROMECHANTCALLY SCANNABLE TROUGH WAVEGUIDE ARRAY Air Force Cambridge Research Center Air Force And Development Command United States Air Force" presents the transmission and radiation principles of an open waveguide antenna, but also does not consider the antenna's fabrication and implementation, especially in the high-frequency range.

[0005] As can be seen from the existing technology, although the principle of open waveguides was discovered in the 1950s, it has mainly remained in the theoretical stage. To realize a physical object, especially in the millimeter wave band, significant innovations are needed in waveguide conversion, feed lines and radiation. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a center-fed single-layer open waveguide antenna, so as to realize the application of single-layer waveguide in the feed line and radiation of vehicle-mounted millimeter-wave radar, and the antenna has a good radiation pattern.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A center-fed single-layer open waveguide antenna includes an analog PCB board and a waveguide antenna board. A lower open waveguide is provided on the lower side of the waveguide antenna board, and an upper open waveguide is provided on the upper side of the waveguide antenna board. The lower open waveguide and the upper open waveguide are connected by a through-hole, which is located at the midpoint of the upper open waveguide.

[0008] Furthermore, the slot width of the lower open waveguide is 2.1 mm, the height of the middle spacer is 1 mm, and the width of the middle spacer is 0.5 mm.

[0009] Furthermore, one end of the lower open waveguide is connected to the waveguide port on the side of the waveguide antenna plate, and the other end of the lower open waveguide is connected to the through-hole through a three-stage impedance matching structure.

[0010] Furthermore, the three-stage impedance matching structure includes a first-step impedance matching structure, a second-step impedance matching structure, and a third-step impedance matching structure. The first-step impedance matching structure, the second-step impedance matching structure, and the third-step impedance matching structure are arranged sequentially along the direction close to the through-hole. The length of the first-step impedance matching structure is 0.74 mm, and the width of the first-step impedance matching structure is 0.9 mm. The length of the second-step impedance matching structure is 1.25 mm, and the width of the second-step impedance matching structure is 1.27 mm. The length of the third-step impedance matching structure is 0.93 mm, and the width of the third-step impedance matching structure is 0.47 mm.

[0011] Furthermore, the length of the through hole is 2mm and the width of the through hole is 1mm.

[0012] Furthermore, the upper open waveguide is provided with a first radiating slot group and a second radiating slot group. The first radiating slot group and the second radiating slot group are respectively located in the upper open waveguide on both sides of the through hole, and the first radiating slot group and the second radiating slot group are distributed symmetrically with respect to the center point of the through hole. The first radiating slot and the second radiating slot respectively include a first radiating slot, a second radiating slot, a third radiating slot and a fourth radiating slot. The first radiating slot, the second radiating slot, the third radiating slot and the fourth radiating slot are arranged sequentially along the direction away from the through hole, and the first radiating slot, the second radiating slot, the third radiating slot and the fourth radiating slot are alternately arranged on the left and right sides of the upper open waveguide.

[0013] Further, the length of the first radiating slot is 2.4 mm, the width of the first radiating slot is 0.75 mm, and the height of the first radiating slot is 0.4 mm; the length of the second radiating slot is 2.4 mm, the width of the second radiating slot is 0.75 mm, and the height of the second radiating slot is 0.5 mm; the length of the third radiating slot is 2.4 mm, the width of the third radiating slot is 0.75 mm, and the height of the third radiating slot is 1.1 mm; the length of the fourth radiating slot is 2.4 mm, the width of the fourth radiating slot is 0.75 mm, and the height of the fourth radiating slot is 1.4 mm; the depth of the upper open waveguide is 3.6 mm, the width of the upper open waveguide is 2.1 mm; the bottom surface of the first radiating slot is 3.6 mm from the upper surface of the waveguide antenna plate; the bottom surface of the second radiating slot is 3.7 mm from the upper surface of the waveguide antenna plate; the bottom surface of the third radiating slot is 3.7 mm from the upper surface of the waveguide antenna plate; and the bottom surface of the fourth radiating slot is 3.9 mm from the upper surface of the waveguide antenna plate.

[0014] Furthermore, eight metal blocks are disposed within the upper open waveguide. The positions of the eight metal blocks correspond one-to-one with the eight radiation slots of the first and second radiation slot groups, and are disposed on the opposite side of the upper open waveguide opposite to the corresponding radiation slots. The length of the metal blocks is equal to the length of the corresponding radiation slots, the sum of the width of the metal blocks and the width of the corresponding radiation slots is the width of the upper open waveguide, and the height of the metal blocks is equal to the height of the corresponding radiation slots.

[0015] Furthermore, a wave-blocking groove is provided on the outer side of the lower open waveguide, and choke grooves are provided on both sides of the upper open waveguide.

[0016] Furthermore, the lower open waveguide is provided with a turning structure, the turning spacer of the turning structure has a width of 0.5mm, a height of 1.05mm, a width of 2.1mm, and a depth of 3mm.

[0017] Compared with the prior art, the present invention has the following advantages and effects: 1. This invention provides a center-fed single-layer open waveguide antenna, which, taking the operating frequency band of vehicle-mounted millimeter-wave radar as an example, has the feasibility of mass production in the 77GHz operating frequency band; 2. The present invention uses a center-feed method in the open waveguide to provide strong frequency stability and a wide operating bandwidth for the radiation pattern. 3. The upper open waveguide of this invention eliminates the spacer of the traditional single-layer waveguide structure, increases the length, width and height of the radiation slot, and controls the transmission and radiation of electromagnetic waves, thereby improving the yield. 4. The waveguide antenna board of the present invention only requires one layer, eliminating the need for welding, thus reducing material costs and improving yield. 5. This invention transitions the turning structure to the lower side of the single-layer waveguide antenna, combined with the metal ground seal of the PCB, to reduce electromagnetic wave energy loss and antenna pattern jitter, and can be manufactured with high strength. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a center-fed single-layer open waveguide antenna according to the present invention.

[0019] Figure 2 This is a schematic diagram of the lower side of the waveguide antenna plate of the present invention.

[0020] Figure 3 This is a schematic diagram of the upper side of the waveguide antenna plate of the present invention.

[0021] Figure 4 This is a lower schematic diagram of a waveguide antenna plate according to another embodiment of the present invention.

[0022] Figure 5 This is a schematic diagram of the turning structure of the present invention.

[0023] Figure 6 This is a comparison diagram of S-parameters of a center-fed single-layer open waveguide antenna of the present invention with and without a simulated PCB board.

[0024] Figure 7 This invention relates to a center-fed single-layer open waveguide antenna with an analog PCB board and an antenna radiation pattern.

[0025] Figure 8 This invention relates to a center-fed single-layer open waveguide antenna without a simulated PCB board, which shows the antenna pattern.

[0026] Figure 9 This is a simulation diagram of the gap tolerance at the end of a center-fed single-layer open waveguide antenna according to the present invention.

[0027] Figure 10 This is a comparison diagram of S-parameters of a center-fed single-layer open waveguide antenna with and without a simulated PCB board, representing the turning structure of the present invention.

[0028] Figure 11 This invention relates to a center-fed single-layer open waveguide antenna with and without a PCB board, showing the antenna radiation pattern at different gaps. Detailed Implementation

[0029] To illustrate in detail the technical solutions adopted by the present invention to achieve the intended technical objectives, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Furthermore, the technical means or technical features in the embodiments of the present invention can be replaced without creative effort. The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0030] like Figure 1 As shown, a center-fed single-layer open waveguide antenna of the present invention includes an analog PCB board 1 and a waveguide antenna board 2, with the waveguide antenna board 2 disposed on the upper side of the analog PCB board 1.

[0031] like Figure 2 and Figure 3 As shown, a lower open waveguide 3 is provided on the lower side of the waveguide antenna plate 2, and an upper open waveguide 4 is provided on the upper side of the waveguide antenna plate 2. The lower open waveguide 4 and the upper open waveguide 3 are connected by a through-hole 5, which is located at the midpoint of the upper open waveguide 4. This invention uses a center-fed method in the upper open waveguide for feeding, resulting in a radiation pattern with strong frequency stability and a wide operating bandwidth.

[0032] The slot width of the lower open waveguide 3 is 2.1 mm, the height of the middle spacer 6 is 1 mm, and the width of the middle spacer 6 is 0.5 mm. The middle spacer 6 divides the waveguide into two parts. When the left and right parts are completely identical, the height and thickness of the middle spacer meet the cutoff height, and the open waveguide is in transmission mode.

[0033] One end of the lower open waveguide 3 is connected to the waveguide port 7 on the side of the waveguide antenna plate 2, and electromagnetic waves are excited by the waveguide port 7. The other end of the lower open waveguide 3 is connected to the through hole 5 through a three-stage impedance matching structure.

[0034] The three-stage impedance matching structure includes a first-step impedance matching structure 8, a second-step impedance matching structure 9, and a third-step impedance matching structure 10. The first-step impedance matching structure 8, the second-step impedance matching structure 9, and the third-step impedance matching structure 10 are arranged sequentially along the direction close to the through hole 5. The length of the first-step impedance matching structure 8 is 0.74 mm, and the width of the first-step impedance matching structure 8 is 0.9 mm. The length of the second-step impedance matching structure 9 is 1.25 mm, and the width of the second-step impedance matching structure 9 is 1.27 mm. The length of the third-step impedance matching structure 10 is 0.93 mm, and the width of the third-step impedance matching structure 10 is 0.47 mm.

[0035] The length of the through hole 5 is 2mm, and the width of the through hole 5 is 1mm.

[0036] The upper open waveguide 4 contains a first radiating slot group and a second radiating slot group. These groups are located on either side of the through-hole 5 within the upper open waveguide 4, and are point-symmetrically distributed with respect to the center point of the through-hole 5. The first and second radiating slots each comprise a first radiating slot 11, a second radiating slot 12, a third radiating slot 13, and a fourth radiating slot 14. These slots are arranged sequentially along a direction away from the through-hole 5, and are alternately positioned on the left and right sides of the upper open waveguide 4. The height of the radiating slots corresponds to the intensity of the radiated energy. The alternating arrangement ensures a 180° phase difference between the radiating elements, controlling the antenna to be a directional beam and achieving low sidelobes. Due to the structural symmetry, the antenna pattern is symmetrical in the plane parallel to the radiating slots.

[0037] The first radiation slot 11 has a length of 2.4 mm, a width of 0.75 mm, and a height of 0.4 mm. The second radiation slot 12 has a length of 2.4 mm, a width of 0.75 mm, and a height of 0.5 mm. The third radiation slot 13 has a length of 2.4 mm, a width of 0.75 mm, and a height of 1.1 mm. The fourth radiation slot 14 has a length of 2.4 mm, a width of 0.75 mm, and a height of 1.4 mm. The upper open waveguide 4 has a depth of 3.6 mm and a width of 2.1 mm. The bottom surface of the first radiating slot 11 is 3.6 mm away from the upper surface of the waveguide antenna plate 2, that is, the bottom surface of the first radiating slot 11 coincides with the bottom surface of the upper open waveguide 4. The bottom surface of the second radiating slot 12 is 3.7 mm away from the upper surface of the waveguide antenna plate 2. The bottom surface of the third radiating slot 13 is 3.7 mm away from the upper surface of the waveguide antenna plate 2. The bottom surface of the fourth radiating slot 14 is 3.9 mm away from the upper surface of the waveguide antenna plate 2.

[0038] Eight metal blocks are disposed within the upper open waveguide 4. These eight metal blocks are positioned on the opposite side of the upper open waveguide, corresponding one-to-one with the eight radiating slots of the first and second radiating slot groups. The length of each metal block is equal to the length of its corresponding radiating slot, and the sum of the width of the metal block and the width of its corresponding radiating slot equals the width of the upper open waveguide. The height of each metal block is equal to the height of its corresponding radiating slot. The introduction of symmetry disruption on both sides of the waveguide causes the transmission mode to switch to a radiation mode. Therefore, the radiating slots are alternately arranged, and metal blocks of half-wavelength length are alternately placed along the edges of the radiating slot disks, creating a 180° phase difference. By adjusting the height of the metal blocks, the amount of radiated energy can be controlled, thereby achieving low sidelobes.

[0039] The aforementioned key dimensions can all achieve good manufacturability, improving the yield of open waveguide antennas. The radiation pattern performance of open waveguide antennas is strongly correlated with the dimensions of the radiating structure. Therefore, the manufacturability of this structure directly determines whether the waveguide antenna can function properly. In order to further achieve manufacturability redundancy, the radiating structure of this invention abandons the spacer of the traditional single-layer waveguide structure, increases the length, width and height of the radiating slot, and controls the transmission and radiation of electromagnetic waves.

[0040] A wave-blocking groove 15 is provided on the outer side of the lower open waveguide 3. The wave-blocking groove 15 surrounds the lower open waveguide 3 on three sides. In this invention, the lower open waveguide of the waveguide antenna plate is combined with the wave-blocking groove, which can significantly reduce the height of the channel and improve the tolerance of the gap, while improving the feasibility of processing and increasing the yield.

[0041] Choke slots 16 are provided on both sides of the upper open waveguide 4.

[0042] Figure 6 The image shows a comparison of the S-parameters of a single-layer open waveguide antenna with and without a PCB board on the underside. In both cases, the standing wave ratio of the antenna is below -10dB in the 76-81GHz range.

[0043] Figure 7 The antenna pattern is shown when there is a PCB board on the underside of a single-layer open waveguide antenna. The peak gain of the antenna is greater than 15dB in the 76-79GHz frequency band, the sidelobes on the elevation plane are all less than -20dB, and the back lobe is less than -30dB.

[0044] Figure 8 The image shows the antenna pattern when there is no PCB board on the bottom of the single-layer open waveguide antenna. The peak gain of the antenna is greater than 14.5dB in the 76-79GHz frequency band, the sidelobes on the elevation plane are all less than -20dB, and the back lobe is less than -12dB. Without the PCB board, there is some energy leakage, which causes the peak gain of the antenna to decrease by about 0.5dB. At the same time, the back lobe of the antenna will be raised to a certain extent.

[0045] When a single-layer open waveguide antenna has a PCB board underneath, and considering only the installation with large screws without considering soldering, a certain gap will inevitably occur between the single-layer open waveguide antenna and the PCB. Figure 9 The figure shows the gap tolerance simulation of a single-layer waveguide antenna. When the gap between the PCB and the antenna is 0.1 mm and 0.2 mm, respectively, the peak gain of the antenna drops by only 0.15 dB and 0.3 dB, and the back lobe of the antenna does not rise significantly.

[0046] like Figure 4 and Figure 5 As shown, the lower open waveguide 3 is provided with a turning structure 17. The turning spacer 18 of the turning structure 17 has a width of 0.5 mm, a height of 1.05 mm, a width of 2.1 mm, and a depth of 3 mm.

[0047] When the height of the middle spacer and the structures on both sides of the middle spacer are symmetrical, the open waveguide is the transmission mode. However, when the transmission line bends, it is difficult to ensure that the structures on both sides of the middle spacer are symmetrical, thus leakage is inevitable. In traditional solutions, the bend structure and the antenna's radiation structure are on the same side, and the leaked electromagnetic waves and the electromagnetic waves radiated by the antenna superimpose, leading to a deterioration in the antenna's radiation pattern performance. This invention designs the bend structure of all antenna channels on the lower side of the waveguide antenna board 2, and there is a simulated PCB board 1 below, which reduces the electromagnetic wave leakage of the bend structure and the impact of electromagnetic waves on the antenna radiation pattern.

[0048] Figure 10The S-parameters of a single-layer waveguide antenna with and without a PCB board and with different gaps from the PCB board are presented. The backlash loss S11 is good in all cases, remaining below -17dB in the 74-81GHz bandwidth. When there is no PCB board at the bottom of the single-layer waveguide 2, the antenna's transmission coefficient S21 is approximately 0.35dB. Figure 11 As shown, when the gap between the PCB board and the single-layer waveguide 2 is 0mm, 0.1mm and 0.2mm respectively, the transmission coefficients are 0.06dB, 0.15dB and 0.25dB respectively, which improve electromagnetic wave leakage to varying degrees.

[0049] This invention provides a center-fed single-layer open waveguide antenna. Taking the operating frequency band of a vehicle-mounted millimeter-wave radar as an example, it is feasible for mass production in the 77GHz operating frequency band. This invention uses a center-fed method in the open waveguide, resulting in a strong frequency stability and a wide operating bandwidth for the radiation pattern. The upper open waveguide eliminates the spacers of the traditional single-layer waveguide structure, increasing the length, width, and height of the radiating slot while controlling electromagnetic wave transmission and radiation, thus improving yield. The waveguide antenna board of this invention only requires one layer, eliminating the need for welding, reducing material costs and improving yield. This invention transitions the turning structure to the lower side of the single-layer waveguide antenna, combined with the metal ground seal of the PCB, reducing electromagnetic wave energy loss and antenna pattern jitter, and also offering strong fabrication capabilities.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments without departing from the scope of the present invention, based on the technical essence of the present invention and within the spirit and principles of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A centrally fed single-layer open waveguide antenna, characterized by: It includes an analog PCB board and a waveguide antenna board. The lower side of the waveguide antenna board is provided with a lower open waveguide, and the upper side of the waveguide antenna board is provided with an upper open waveguide. The lower open waveguide and the upper open waveguide are connected by a through hole, which is located at the midpoint of the upper open waveguide. One end of the lower open waveguide is connected to the waveguide port on the side of the waveguide antenna plate, and the other end of the lower open waveguide is connected to the through-hole through a three-stage impedance matching structure. The upper open waveguide contains a first radiating slot group and a second radiating slot group. The first and second radiating slot groups are located within the upper open waveguides on both sides of the through-hole and are point-symmetrically distributed with respect to the center point of the through-hole. The first and second radiating slots respectively include a first radiating slot, a second radiating slot, a third radiating slot, and a fourth radiating slot. Four radiating slots are arranged sequentially along the direction away from the through-hole, and the first, second, third, and fourth radiating slots are alternately arranged on the left and right sides of the upper open waveguide. Eight metal blocks are arranged inside the upper open waveguide. The positions of the eight metal blocks correspond one-to-one with the eight radiating slots of the first and second radiating slot groups and are arranged on the opposite side of the upper open waveguide to the corresponding radiating slot. The length of the metal block is equal to the length of the corresponding radiating slot, the sum of the width of the metal block and the width of the corresponding radiating slot is the width of the upper open waveguide, and the height of the metal block is equal to the height of the corresponding radiating slot.

2. A centrally fed single-layer open waveguide antenna according to claim 1, characterized in that: The slot width of the lower open waveguide is 2.1 mm, the height of the middle spacer is 1 mm, and the width of the middle spacer is 0.5 mm.

3. A centrally fed single-layer open waveguide antenna according to claim 1, characterized in that: The three-stage impedance matching structure includes a first-step impedance matching structure, a second-step impedance matching structure, and a third-step impedance matching structure. The first-step impedance matching structure, the second-step impedance matching structure, and the third-step impedance matching structure are arranged sequentially along the direction close to the through hole. The length of the first-step impedance matching structure is 0.74 mm, and the width of the first-step impedance matching structure is 0.9 mm. The length of the second-step impedance matching structure is 1.25 mm, and the width of the second-step impedance matching structure is 1.27 mm. The length of the third-step impedance matching structure is 0.93 mm, and the width of the third-step impedance matching structure is 0.47 mm.

4. A centrally fed single-layer open waveguide antenna according to claim 1, characterized in that: The through hole is 2mm long and 1mm wide.

5. The centrally fed single-layer open waveguide antenna according to claim 1, characterized in that: The first radiating slot has a length of 2.4 mm, a width of 0.75 mm, and a height of 0.4 mm. The second radiating slot has a length of 2.4 mm, a width of 0.75 mm, and a height of 0.5 mm. The third radiating slot has a length of 2.4 mm, a width of 0.75 mm, and a height of 1.1 mm. The fourth radiating slot has a length of 2.4 mm, a width of 0.75 mm, and a height of 1.4 mm. The upper open waveguide has a depth of 3.6 mm and a width of 2.1 mm. The bottom surface of the first radiating slot is 3.6 mm from the upper surface of the waveguide antenna plate. The bottom surface of the second radiating slot is 3.7 mm from the upper surface of the waveguide antenna plate. The bottom surface of the third radiating slot is 3.7 mm from the upper surface of the waveguide antenna plate. The bottom surface of the fourth radiating slot is 3.9 mm from the upper surface of the waveguide antenna plate.

6. The centrally fed single-layer open waveguide antenna according to claim 1, characterized in that: A wave-blocking groove is provided on the outer side of the lower open waveguide, and choke grooves are provided on both sides of the upper open waveguide.

7. The centrally fed single-layer open waveguide antenna according to claim 1, characterized in that: The lower open waveguide is provided with a turning structure. The turning spacer of the turning structure has a width of 0.5 mm, a height of 1.05 mm, a width of 2.1 mm, and a depth of 3 mm.

Images