A planar transmission line to rectangular waveguide transition structure

Abstract

This invention discloses a planar transmission line to rectangular waveguide conversion structure, comprising a multi-layer ground plane, a planar transmission line, a matching unit, and a rectangular waveguide. The multi-layer ground plane has standard waveguide aperture regions formed by cutouts at corresponding waveguide positions. The matching unit is arranged within the standard waveguide aperture regions and is E-shaped, comprising one transverse stub and three longitudinal stubs, with the middle longitudinal stub corresponding to the stripline. This invention utilizes the simple structure of the E-shaped matching unit. The two U-shaped portions formed by the three longitudinal stubs and one transverse stub of the E-shaped structure all possess capacitive characteristics, and these characteristics change little with frequency, resulting in better broadband matching performance. Compared to a conventional square matching structure, the E-shaped matching structure achieves a wider matching effect and reduces the precision requirements during actual assembly.

Description

Technical Field

[0001] This invention relates to the field of millimeter-wave technology, and more specifically to a planar transmission line to rectangular waveguide conversion structure. Background Technology

[0002] Millimeter waves have advantages such as wide usable bandwidth, large information capacity, good confidentiality, and small size, and are widely used in communications, electronic warfare, radar, and detection. In particular, the V-band (50-75GHz), E-band (60-90GHz), and W-band (75-110GHz) have received widespread attention in communications in recent years.

[0003] In millimeter-wave technology, the connection between the antenna and the radio frequency front end is generally achieved through a waveguide interface. Therefore, the antenna also needs a converter to transition the stripline to a standard waveguide.

[0004] For example, the invention patent "Stripline-Waveguide Converter" with authorization announcement number CN102074772B discloses a conversion structure whose excitation matching unit is a square structure similar to a microstrip antenna. While the structure is simple, its electrical performance varies significantly with frequency, resulting in insufficient operating bandwidth and thus requiring high precision during actual assembly. Furthermore, the lack of metal vias on both sides of the stripline causes some energy loss before the electromagnetic wave even reaches the excitation matching unit; the excitation matching unit is not directly connected to the end of the stripline but transmits the signal through coupling, further increasing losses.

[0005] For example, the invention application CN109449550A, entitled "A W-band waveguide-stripline conversion structure," uses a square patch to convert the TEM mode on the stripline into the TE10 mode on the rectangular waveguide, which also suffers from insufficient bandwidth. Furthermore, the stripline ends are also open-circuited, resulting in significant signal loss due to signal transmission via coupling.

[0006] Similarly, grounded coplanar waveguides and rectangular waveguides suffer from the same loss problem. Summary of the Invention

[0007] The purpose of this invention is to provide a planar transmission line to rectangular waveguide conversion structure that can achieve ultra-wideband transmission. This conversion structure realizes high-efficiency interconnection between striplines and standard waveguide devices, has wideband and low-loss conversion performance, and has a simple structure and low positioning accuracy requirements during assembly.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A planar transmission line to rectangular waveguide conversion structure includes a multi-layer ground plane, a planar transmission line, a matching unit, and a rectangular waveguide. The multi-layer ground plane has a standard waveguide aperture area formed by hollowing out the bottom layer corresponding to the waveguide position. The matching unit is disposed in the standard waveguide aperture area. The matching unit is E-shaped and includes one transverse branch and three longitudinal branches, with the middle longitudinal branch corresponding to the planar transmission line.

[0010] Furthermore, the end of the planar transmission line is directly connected to the matching unit.

[0011] Furthermore, the end of the planar transmission line is connected to the end of the intermediate longitudinal branch of the matching unit via a metallized via.

[0012] Furthermore, the planar transmission line is a stripline.

[0013] Furthermore, the multi-layer floor comprises, from top to bottom, a strip upper floor, an upper height plate, a signal line layer plate, a lower height plate, and a strip lower floor. The upper height plate, the signal line layer plate, and the lower height plate are hollowed out at the location of the waveguide to form the standard waveguide port area, and hollowed out in the area where the strip line is located to form a through groove. The strip line is distributed in the through groove of the signal line layer plate.

[0014] Furthermore, the planar transmission line is a grounded coplanar waveguide signal line.

[0015] Furthermore, the multi-layer floor includes a signal line layer, a height plate, and a grounding plate; the grounding coplanar waveguide signal lines are distributed in the signal line layer; the height plate is provided with through slots corresponding to the grounding coplanar waveguide signal lines, so that the grounding coplanar waveguide signal lines are at a certain height from the grounding plate.

[0016] Furthermore, each floor is connected via a second metallized via, which is distributed around the through slot and the standard waveguide port area.

[0017] Furthermore, the second metallized via is arranged in a double row.

[0018] Furthermore, the multi-layer floor is a metal plate, with GH-100 dielectric material filling the spaces between each metal plate.

[0019] By adopting the above technical solution, the present invention has the following advantages compared with the prior art:

[0020] 1. The E-type matching unit of the present invention has a simple structure and low positioning accuracy requirements during assembly. The two U-shaped parts formed by the three longitudinal branches and one transverse branch of the E-type structure have capacitance characteristics, and the capacitance characteristics change little with frequency, resulting in better broadband matching performance. Compared with the ordinary square matching structure, the E-type matching structure 8 achieves a wider matching effect.

[0021] 2. In this invention, the signal is directly connected to the E-type matching unit, and the electromagnetic signal is directly transmitted to the matching unit, resulting in low loss;

[0022] 3. The present invention provides metal vias on both sides of the signal line to reduce the loss of electromagnetic waves when propagating in a planar transmission line; in addition, the present invention also uses two rows of metal vias to further reduce the attenuation of electromagnetic waves. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention;

[0024] Figure 2 This is another structural schematic diagram of Embodiment 1 of the present invention;

[0025] Figure 3 This is another structural schematic diagram of Embodiment 1 of the present invention;

[0026] Figure 4 This is a simulation diagram illustrating the application of Embodiment 1 of the present invention;

[0027] Figure 5 This is a schematic diagram of the structure of Embodiment 2 of the present invention;

[0028] Figure 6 This is another structural schematic diagram of Embodiment 2 of the present invention;

[0029] Figure 7 This is another structural schematic diagram of Embodiment 2 of the present invention;

[0030] Figure 8 This is a simulation diagram of Embodiment 2 of the present invention.

[0031] Explanation of reference numerals in the attached figures:

[0032] Floor 100, strip floor 110, lower height plate 120, signal line plate 130, upper height plate 140, strip floor 150;

[0033] Strip line 200;

[0034] Matching unit 300, longitudinal branch 310, longitudinal branch 320, longitudinal branch 330, lateral branch 340;

[0035] Rectangular waveguide 400, standard waveguide port area 410;

[0036] Second metallized via 500;

[0037] Floor 600: First floor 610, second floor 620, third floor 630, fourth floor 640, fifth floor 650, sixth floor 660, seventh floor 670, eighth floor 680;

[0038] Grounded coplanar waveguide signal line 700;

[0039] First metallized via 800. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Furthermore, it should be noted that:

[0041] The terms “upper,” “lower,” “left,” “right,” “vertical,” “horizontal,” “inner,” and “outer” are based on the orientation or positional relationship shown in the accompanying drawings and are used merely for the convenience of describing the present invention and simplifying the description. They are not intended to indicate or imply that the device or element of the present invention must have a specific orientation and therefore should not be construed as a limitation of the present invention.

[0042] When an element is referred to as being "fixed to," "set on," or "contained on" another element, it can be directly on or indirectly on that other element. When an element is referred to as being "connected to," it can be directly connected to or indirectly connected to that other element.

[0043] Unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0044] Example 1

[0045] Please refer to Figures 1-3 As shown, the present invention discloses a planar transmission line to rectangular waveguide conversion structure to realize the interconnection between stripline and rectangular waveguide, which includes a multilayer ground plane 100, a stripline 200, a matching unit 300 and a rectangular waveguide 400.

[0046] In this embodiment, the multi-layer floor 100 includes, from top to bottom, a strip upper floor 150, an upper height plate 140, a signal line plate 130, a lower height plate 120, and a strip lower floor 110. Each floor 100 is a metal plate, and the spaces between the metal plates are filled with GH-100 dielectric material.

[0047] The strip floor 110 has a standard waveguide opening area 410 formed by hollowing out the corresponding rectangular waveguide 400. The matching unit 300 is arranged in the standard waveguide opening area 410 of the strip floor 110. The matching unit 300 is E-shaped and includes a transverse branch 340 and three longitudinal branches (310, 320 and 330). The middle longitudinal branch 310 corresponds to the strip line 200.

[0048] The matching unit 300 is tuned to the operating frequency. The two U-shaped parts formed by the three longitudinal branches (310, 320 and 330) and one transverse branch 340 in the matching unit 300 all have capacitive characteristics, and the capacitive characteristics change little with frequency. Thus, the broadband matching performance is better. Compared with the ordinary square matching structure, the E-type matching structure achieves a wider matching effect and reduces the accuracy requirements of actual assembly.

[0049] After the electromagnetic wave is transmitted from the stripline 200 to the matching unit 300, the energy is concentrated around the gaps formed at both ends of the matching unit 300 and the wide side of the standard waveguide opening. In addition, the electric field direction in the two gaps is consistent and perpendicular to the wide side of the standard waveguide, so as to match the electric field direction of the main transmission mode TE10 in the rectangular waveguide 400, thereby exciting the main mode transmission of the rectangular waveguide 400 and realizing the transmission mode conversion between the stripline 200 and the rectangular waveguide 400.

[0050] In this invention, the end of the stripline 200 is directly connected to the matching unit 300. Specifically, the end of the stripline 200 is connected to the end of the intermediate longitudinal branch 310 of the matching unit 300 through a first metallized via 800. Electromagnetic signals are directly transmitted to the matching unit 300. Compared with the conventional method of connecting the stripline 200 in an open-circuit coupling manner, this invention reduces the loss of electromagnetic signal transmission.

[0051] The upper height plate 140, signal line layer plate 130, and lower height plate 120 are hollowed out at the location of the rectangular waveguide 400 to form a standard waveguide aperture region 410. A certain width of metal is hollowed out in the area where the stripline 200 is located to form a through slot. The stripline 200 is distributed in the through slot of the signal line layer plate 130. In this embodiment, the width of the through slot of the signal line layer plate 130 is 0.075-0.1 mm. Thus, the upper height plate 140, signal line layer plate 130, and lower height plate 120 adjust the impedance of the stripline 200 and better confine electromagnetic waves propagating on the stripline 200, thereby reducing the transmission loss of the stripline 200.

[0052] The upper strip floor 150 and the lower strip floor 110 are connected by a second metallized via 500 extending from the upper strip floor 150 to the lower strip floor 110. The second metal via is distributed around the through slot and the standard waveguide port area 410.

[0053] The second metallized via 500 connecting the upper ground plane 150 and the lower ground plane 110 of the stripline can both avoid affecting the TEM mode transmission of the stripline 200 and block the propagation of electromagnetic waves whose polarization direction is parallel to the axis of the metallized via. That is, the upper height plate 140, the lower height plate 120, and the first metallized via 800 form a back cavity, guiding the electromagnetic waves to propagate in the direction of the rectangular waveguide without generating unnecessary higher-order modes.

[0054] In addition, the present invention also provides a second metallized via 500 in the surrounding area of ​​the through slot, which reduces the loss of electromagnetic waves on the path from the stripline 200 to the matching unit 300.

[0055] In a preferred embodiment, the second metallized via 500 is arranged in two rows. The use of two rows of metal vias better reduces the attenuation of electromagnetic waves and further reduces losses.

[0056] Please refer to Figure 4 As shown, the horizontal axis represents bandwidth, and the vertical axis represents loss. Curve S11 represents return loss, and S21 represents insertion loss. Simulation results show that, with the structure of this invention, the return loss is less than -15dB and the insertion loss is less than -0.45dB in a very wide (31.5%) frequency band of 61.5GHz-83.5GHz; and the return loss is less than -20dB and the insertion loss is less than -0.4dB in a frequency band of 73.4GHz-82.3GHz. Therefore, the planar transmission line to rectangular waveguide conversion structure provided by this invention can not only operate simultaneously in the V, E, and W bands, but also has excellent conversion characteristics in the 76GHz-81GHz frequency band used in automotive radar applications.

[0057] Example 2

[0058] Please refer to Figures 5-7 As shown, the present invention also discloses a planar transmission line to rectangular waveguide conversion structure to realize the interconnection of coplanar waveguide and rectangular waveguide, which specifically includes: a multilayer ground plane 600, a grounded coplanar waveguide signal line 700, a matching unit 300 and a rectangular waveguide 400.

[0059] The multi-layer floor 600 is a PCB metal board, with GH-100 dielectric material filling the spaces between each metal board. In this embodiment, the floor 600 has 8 layers.

[0060] The eight floor panels are arranged from bottom to top: the bottom floor panel (first floor panel 610, second floor panel 620, and third floor panel 630) is hollowed out in the standard waveguide port area 410; the sixth floor panel 660 is the grounding plate for the grounded coplanar waveguide; the seventh floor panel 670 is a height plate with a 0.4mm-0.5mm wide metal cutout to allow the grounded coplanar waveguide signal line 700 (coplanar waveguide transmission line) to be at a certain height from the sixth floor panel 660, approximately 0.21mm; the eighth floor panel 680 is a signal line layer, with the grounded coplanar waveguide signal line 700 distributed in the hollowed-out area of ​​the eighth floor panel 680, and the matching unit 300 is arranged in the standard waveguide port area 410 of the first floor panel 610, with the end of the grounded coplanar waveguide signal line 700 and the end of the intermediate branch 310 of the matching unit 300 connected through the first metallized via 800. Two rows of second metallized vias 500 are arranged at a certain distance around the area occupied by the grounded coplanar waveguide signal line 700 and the waveguide port. The second metallized vias 500 penetrate each ground plane (i.e., from the first ground plane 610 to the eighth ground plane 680), thereby forming a back cavity. The rectangular waveguide 400 (standard W12 waveguide) is connected to the standard waveguide port area 410 in the first ground plane 610.

[0061] like Figure 8 As shown, simulation results indicate that the return loss is less than -15dB and the insertion loss is less than -0.65dB in the wide (8.8%) frequency band of 75.15GHz-82.04GHz; and the return loss is less than -20dB and the insertion loss is less than -0.55dB in the frequency band of 76GHz-81GHz. The grounded coplanar waveguide to planar transmission line to rectangular waveguide conversion structure provided by this invention can not only operate simultaneously in the V, E, and W bands, but also has excellent conversion characteristics in the frequency band of automotive radar applications in the 76GHz-81GHz range.

[0062] The working principle of this invention is as follows: the signal at the end of the grounded coplanar waveguide signal line 700 is directly connected to the matching unit 300 of the underlying E-type structure through the first metallized via 800, and the electromagnetic signal is directly transmitted to the matching unit 300; the second metallized via 500 connecting the eighth ground plane 680 and the first ground plane 610 can not only not affect the TEM mode transmission of the grounded coplanar waveguide, but also block the propagation of electromagnetic waves whose polarization direction is parallel to the axis of the metallized via. That is, the eighth ground plane 680, the sixth ground plane 660, and the second metallized via 500 form a back cavity, guiding the electromagnetic wave through the first metallized via 800 to propagate to the E-type structure above the rectangular waveguide, without generating unnecessary higher-order modes; the use of two rows of second metallized vias 500 further reduces the attenuation of electromagnetic waves.

[0063] The E-type matching unit 300 tunes the operating frequency. The two U-shaped sections formed by the three longitudinal branches (310, 320, 330) and one transverse branch 340 in the unit all have capacitive characteristics, and the capacitive characteristics change little with frequency, resulting in better broadband matching performance. Compared with the ordinary square matching structure, the matching unit 300 achieves a wider matching effect. After passing through the E-type matching unit 300, the energy is concentrated around the gaps formed at both ends of the matching unit and the wide side of the standard waveguide port area 410. The electric field directions in the two gaps are consistent and perpendicular to the wide side of the standard waveguide, matching the electric field direction of the main transmission mode TE10 in the standard waveguide, thereby exciting the transmission of the main mode of the standard waveguide and realizing the conversion between the grounded coplanar waveguide and the rectangular waveguide transmission mode.

[0064] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A planar transmission line to rectangular waveguide conversion structure, comprising a multilayer ground plane, a planar transmission line, a matching unit, and a rectangular waveguide, characterized in that: The matching unit is E-shaped and includes one horizontal stub and three vertical stubs. The end of the planar transmission line is connected to the end of the middle vertical stub of the matching unit through a first metallized via. The planar transmission line is a stripline; The multi-layer ground plane, from top to bottom, includes a stripline upper ground plane, an upper height plate, a signal line layer plate, a lower height plate, and a stripline lower ground plane. The upper height plate, signal line layer plate, and lower height plate have cutouts at the locations of the rectangular waveguides to form standard waveguide opening areas, and cutouts in the areas where the striplines are located to form through slots. The striplines are distributed in the through slots of the signal line layer plate. The matching unit is disposed in the standard waveguide opening area. Each floor panel is connected via a second metallized via, which is distributed around the through slot and the standard waveguide port area; The second metallized via is arranged in a double row.

2. The planar transmission line to rectangular waveguide conversion structure as described in claim 1, characterized in that: The planar transmission line is a grounded coplanar waveguide signal line.

3. The planar transmission line to rectangular waveguide conversion structure as described in claim 2, characterized in that: The grounded coplanar waveguide signal lines are distributed in the signal line layer; the height plate is provided with through slots corresponding to the grounded coplanar waveguide signal lines, so that the grounded coplanar waveguide signal lines are at a certain height from the upper floor of the strip and the lower floor of the strip.

4. The planar transmission line to rectangular waveguide conversion structure as described in claim 1, characterized in that: The multi-layer floor is a metal plate, with GH-100 medium material filling between each metal plate.

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