A low-loss non-planar split gap waveguide-rectangular waveguide transition structure

Abstract

This invention discloses a low-loss non-split gap waveguide-rectangular waveguide transition structure for terahertz devices. Addressing the problem in existing technologies where the vertical step at the connection between the upper and lower cavities requires manufacturing and assembly tolerances, resulting in large gaps that lead to electromagnetic leakage and transition losses, this invention introduces a pair of L-shaped chokes on the vertical sidewalls at the waveguide connection. This suppresses electromagnetic leakage caused by the split gap, achieving broadband, low-loss transition transmission between waveguides with different cross-sections. Furthermore, the structure of this invention reduces the requirements for processing and assembly precision. This invention offers advantages such as simple structure, reduced processing and assembly difficulty, and broadband, low-loss transmission.

Description

Technical Field

[0001] This invention belongs to the field of terahertz devices, and specifically relates to a low-loss heterogeneous split gap waveguide-rectangular waveguide transition structure. Background Technology

[0002] For high-frequency waveguide circuits, waveguides typically need to be split for fabrication. Due to insufficient fabrication and assembly precision, the waveguide profile cannot be perfectly flat, resulting in micron-level gaps. To reduce electromagnetic radiation / leakage caused by waveguide splitting, splitting is usually done at the center of the waveguide's E-plane. Splitting at the top of the waveguide or on the H-plane will lead to significant electromagnetic losses, which are more severe at high frequencies, such as submillimeter waves and terahertz bands.

[0003] In recent years, gap waveguides have been widely studied due to their ability to guide electromagnetic waves efficiently without electrical contact. Various E-plane and H-plane split gap waveguide passive components have been reported. However, traditional active chip packaging is mostly based on waveguide blocks with the center split of the E-plane of a rectangular waveguide. When using top-split E-plane gap waveguide components for chip packaging, the package module is fabricated as upper and lower metal cavities. The cross-sections of the gap waveguide and the rectangular waveguide are not on the same plane, and there is a height difference at their connection. To achieve a tight fit between the upper and lower cavities, the vertical step at their connection must retain manufacturing and assembly tolerances, resulting in a large gap. To reduce electromagnetic leakage and transition loss, a low-loss transition between the top-split E-plane gap waveguide and the center-split E-plane rectangular waveguide is required, but research on this issue is currently relatively scarce. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a low-loss non-planar split gap waveguide-rectangular waveguide transition structure. By introducing a pair of L-shaped chokes on the vertical sidewalls at the waveguide connection, electromagnetic leakage caused by the split gap is suppressed.

[0005] The technical solution adopted in this invention is as follows: a low-loss heterogeneous split gap waveguide-rectangular waveguide transition structure, comprising: an E-plane gap waveguide 4 and an E-plane rectangular waveguide 3, the E-plane gap waveguide 4 and the E-plane rectangular waveguide 3 having the same height, and their upper and lower bottom surfaces sharing the same plane, the cross-sections of the E-plane gap waveguide 4 and the E-plane rectangular waveguide 3 being on different planes, and the E-plane rectangular waveguide 3 being divided into two symmetrical parts, respectively denoted as: the first half-height E-plane rectangular waveguide 31 and the second half-height E-plane rectangular waveguide 32;

[0006] The transition structure is made of upper and lower parts, referred to as: upper cavity 1 and lower cavity 2 respectively;

[0007] The E-plane gap waveguide 4 and the second half-height E-plane rectangular waveguide 32 are fabricated on the lower cavity 2, and the first half-height E-plane rectangular waveguide 31 is fabricated on the upper cavity 1. There is a step at the connection between the upper cavity 1 and the lower cavity 2 where the E-plane gap waveguide 4 and the half-height E-plane rectangular waveguide are connected.

[0008] The top of the stepped structure of the upper cavity 1 on both sides of the first half-height E-plane rectangular waveguide 31 includes a pair of L-shaped choke slots. The L-shaped choke slots are symmetrically distributed about the central axis of the first half-height E-plane rectangular waveguide 31. The two ends of the L-shaped choke slots are connected to the side wall of the first half-height E-plane rectangular waveguide 31 and the vertical side wall 82 of the stepped structure of the upper cavity 1, respectively.

[0009] The E-plane gap waveguide 4 specifically includes: a full-height E-plane rectangular waveguide groove, a stepped structure of the lower cavity 2 on both sides of the full-height E-plane rectangular waveguide groove, and a nail bed structure 5 located at the top of the stepped structure of the lower cavity 2.

[0010] The E-plane gap waveguide 4 is docked with the E-plane rectangular waveguide 3.

[0011] The upper and lower bottom surfaces of E-plane gap waveguide 4 and E-plane rectangular waveguide 3 share the same plane.

[0012] The first sidewall of the nail bed structure 5 is coplanar with the vertical sidewall 81 of the stepped structure of the lower cavity 2.

[0013] The second sidewall of the nail bed structure 5 is coplanar with the sidewall of the full-height E-plane rectangular waveguide groove.

[0014] The height of the stepped structure of the upper cavity 1 is equal to the sum of the height of the stepped structure of the lower cavity 2 and the height of the nail bed structure 5.

[0015] The beneficial effects of this invention are as follows: This invention proposes a low-loss non-planar split gap waveguide-rectangular waveguide transition structure. By introducing a pair of L-shaped choke slots on the vertical sidewalls at the waveguide connection, electromagnetic leakage caused by non-ideal surface contact between the upper and lower cavities of the waveguides with different profiles can be effectively suppressed in the terahertz band. This achieves broadband, low-loss transition transmission between waveguides with different profiles. The transition structure of this invention allows for gaps between the upper and lower cavities, reducing the requirements for processing and assembly accuracy. It has the advantages of simple structure, reduced processing and assembly difficulty, and broadband, low-loss transmission. Attached Figure Description

[0016] Figure 1 A three-dimensional structural diagram of the low-loss heterogeneous split gap waveguide-rectangular waveguide transition structure provided in Embodiment 1 of the present invention;

[0017] Figure 2A three-dimensional structural diagram of the upper cavity of the low-loss heterogeneous split gap waveguide-rectangular waveguide transition structure provided in Embodiment 1 of the present invention;

[0018] Figure 3 A three-dimensional structural diagram of the lower cavity of the low-loss heterogeneous split gap waveguide-rectangular waveguide transition structure provided in Embodiment 1 of the present invention;

[0019] Figure 4 This is a top view of the low-loss heterogeneous split gap waveguide-rectangular waveguide transition structure provided in Embodiment 1 of the present invention.

[0020] Figure 5 This is a side view of the low-loss heterospatial split gap waveguide-rectangular waveguide transition structure provided in Embodiment 1 of the present invention;

[0021] Figure 6 Electric field distribution at 220 GHz for the low-loss heterogeneous split gap waveguide-rectangular waveguide transition structure provided in Embodiment 1 of the present invention without an L-shaped choke.

[0022] Figure 7 Electric field distribution at 220 GHz for the low-loss heterogeneous split gap waveguide-rectangular waveguide transition structure provided in Embodiment 1 of the present invention, in the presence of an L-shaped choke.

[0023] Figure 8 Comparison of S-parameter simulation results for the low-loss heterogeneous split gap waveguide-rectangular waveguide transition structure provided in Embodiment 1 of the present invention with and without L-shaped chokes, applied to the WR-4.3 waveguide frequency band;

[0024] The explanations of the markings in the attached diagram are as follows:

[0025] 1: Upper cavity; 2: Lower cavity; 3: E-plane rectangular waveguide; 31: E-plane rectangular waveguide with first half height; 32: E-plane rectangular waveguide with second half height; 4: E-plane gap waveguide; 5: Bed of nails structure; 6: L-shaped choke groove; 61: Inner wall of L-shaped choke groove; 62: Outer wall of L-shaped choke groove; 7: Air gap; 81: Vertical sidewall of the stepped structure of lower cavity 2; 82: Vertical sidewall of the stepped structure of upper cavity 1. Detailed Implementation

[0026] To facilitate understanding of the technical content of this invention by those skilled in the art, the following description, in conjunction with the accompanying drawings, further illustrates the invention.

[0027] Example 1

[0028] This embodiment provides a low-loss non-planar split gap waveguide-rectangular waveguide transition structure operating in the 170–260 GHz frequency band, as shown in the following figure. Figures 1-5As shown, the transition structure is fabricated by dividing it into upper and lower metal cavities. The E-plane gap waveguide 4 and the E-plane rectangular waveguide 3 have the same height, and their upper and lower bottom surfaces share the same plane. The cross-sections of the E-plane gap waveguide 4 and the E-plane rectangular waveguide 3 are on different planes. The cross-section of the E-plane gap waveguide 4 is located at the top of the E-plane gap waveguide 4, and the cross-section of the E-plane rectangular waveguide 3 is located at the center of the E-plane rectangular waveguide 3. There is a step at the connection between the E-plane gap waveguide 4 and the E-plane rectangular waveguide 3. The E-plane rectangular waveguide 3 is divided into two symmetrical parts, which are respectively denoted as: the first half-height E-plane rectangular waveguide 31 and the second half-height E-plane rectangular waveguide 32. The E-plane gap waveguide 4 and the second half-height E-plane rectangular waveguide 32 are fabricated on the upper cavity 1, and the first half-height E-plane rectangular waveguide 31 is fabricated on the lower cavity 2.

[0029] like Figure 2 As shown, the lower cavity 2 specifically includes: an E-plane gap waveguide 4 and a second half-height E-plane rectangular waveguide 32, the E-plane gap waveguide 4 being connected to the second half-height E-plane rectangular waveguide 32; the E-plane gap waveguide 4 specifically includes: an E-plane rectangular waveguide groove, a stepped structure of the lower cavity 2 located on both sides of the E-plane rectangular waveguide groove, and a nail bed structure 5 located at the top of the stepped structure of the lower cavity 2.

[0030] The E-plane gap waveguide 4 is docked with the E-plane rectangular waveguide 3, and the upper and lower bottom surfaces of the E-plane gap waveguide 4 and the E-plane rectangular waveguide 3 are located on the same plane.

[0031] The first sidewall of the nail bed structure 5 is coplanar with the vertical sidewall 81 of the stepped structure of the lower cavity 2.

[0032] The second sidewall of the nail bed structure 5 is coplanar with the sidewall of the full-height E-plane rectangular waveguide groove.

[0033] like Figure 3 As shown, the upper cavity includes: a first half-height E-plane rectangular waveguide 31, a stepped structure of the upper cavity 1 located on both sides of the first half-height E-plane rectangular waveguide 31, and a pair of connected L-shaped chokes 6 on the stepped structure of the upper cavity 1; the pair of L-shaped chokes 6 are symmetrically distributed about the central axis of the first half-height E-plane rectangular waveguide 31, and the two ends of the L-shaped chokes 6 are connected to the side wall of the first half-height E-plane rectangular waveguide 31 and the vertical side wall 82 of the stepped structure of the upper cavity 1, respectively.

[0034] The height of the vertical sidewall 81 of the stepped structure of the lower cavity 2 is equal to the sum of the height of the vertical sidewall 82 of the stepped structure of the upper cavity 1 and the height of the nail bed structure 5.

[0035] Those skilled in the art will understand that in the art, a full-height waveguide refers to a waveguide aperture cross-section with a side length ratio of 2:1, and a half-height waveguide refers to a waveguide aperture cross-section with a side length ratio of 1:1. In this invention, the E-plane gap waveguide 4 and the E-plane rectangular waveguide 3 are full-height waveguides, and the width and narrow sides of their internal cavities are equal, with a width-to-narrow side ratio of 2:1. In this embodiment, the waveguide apertures of the full-height E-plane gap waveguide 4 and the full-height E-plane rectangular waveguide 3 are of model WR-4.3, with dimensions of 1.092mm × 0.546mm.

[0036] The E-plane gap waveguide 4 has two rows of square nails on each side of its nail bed structure, with the inner row of square nails aligned with the corresponding waveguide wall. The height of the nail bed structure is one-quarter wavelength. In this embodiment, the height of the nail bed structure is 0.32 mm, the side length of the square nails is 0.32 mm, and the spacing is 0.2 mm.

[0037] The height of the vertical sidewall 81 of the stepped structure of the lower cavity 2 is half the waveguide height, which is 0.546 mm in this embodiment. A gap of 0.02 mm is left between the vertical sidewalls connecting the upper and lower cavities to facilitate assembly.

[0038] The L-shaped choke grooves 6 are symmetrically distributed on both sides of the full-height E-plane rectangular waveguide. The two sides of the "L" are of equal length, meaning the two vertical groove segments of the L-shaped choke groove 6 are of equal length. The length, width, and depth of the two vertical groove segments of the L-shaped choke groove 6 are all within the range of 1 / 16 to 1 / 8 of the wavelength. In this embodiment, the inner wall 61 of the L-shaped choke groove has a length of 0.14 mm, the width of the L-shaped choke groove 6 is 0.1 mm, and the depth of the L-shaped choke groove 6 is 0.2 mm. The width of the L-shaped choke groove 6 is the distance between the inner wall 61 and the outer wall 62 of the L-shaped choke groove 6.

[0039] This embodiment uses 3D electromagnetic simulation software to precisely design the dimensions of the low-loss transition between the top-split E-plane gap waveguide and the rectangular waveguide. To facilitate verification of the performance of the low-loss transition structure proposed in this embodiment, transition structures with and without the L-shaped choke were simulated and compared in the 170–260 GHz frequency band corresponding to the WR-4.3 waveguide. To accurately simulate the situation where the upper and lower cavities are not tightly connected in actual assembly, a 0.01 mm gap was reserved between the horizontal contact surfaces of the upper and lower cavities, and a 0.02 mm gap was reserved between the vertical contact surfaces. The simulated electric field distributions of the transition structures without and with the L-shaped choke are as follows: Figures 6-8 As shown in the figure, a comparison reveals that the electric field of the transition structure without the L-shaped choke leaks outwards along the cross-section, while the electric field of the transition structure with the L-shaped choke is confined near the waveguide wall at the cross-section, preventing effective leakage and thus achieving a low-loss transition. The simulated S-parameters are compared as follows: Figure 8As shown, in the full waveguide band of 170–260 GHz, the input return loss of both transitions exceeds 30 dB. The loss without the L-shaped choke is about 0.1 dB, while the loss with the L-shaped choke is basically less than 0.05 dB, reducing the loss to half of the original, which proves the effectiveness of the structure.

[0040] The working principle of the low-loss non-planar split gap waveguide-rectangular waveguide transition structure of the present invention is as follows:

[0041] For the top-split E-plane gap waveguide 4, when there is a splitting gap at the top, due to the presence of the bed of nails structure, the cross-section of the E-plane gap waveguide 4 forms a high-resistivity surface, and electromagnetic waves in a specific frequency range cannot propagate to the surroundings, thereby reducing the transmission loss of the E-plane gap waveguide 4. For the center-split E-plane rectangular waveguide 3, according to the current distribution of the TE10 mode of the main mode of the E-plane rectangular waveguide 3, waveguide splitting in this plane will not cut off the current lines and will not affect the current flow direction of the TE10 mode, thereby achieving low-loss transmission of the E-plane rectangular waveguide 3. At the connection between the gap waveguide 4 and the E-plane rectangular waveguide 3, the top cross-section cannot achieve electromagnetic leakage due to the presence of the bed of nails. If there are no electromagnetic leakage suppression measures in the center cross-section, the waveguide discontinuity introduced by the vertical cross-section will cause the current on the waveguide surface to propagate from the center cross-section to the surroundings. However, the introduction of the L-shaped choke groove of the present invention cuts off the path for the current to continue radiating to the surroundings from the waveguide discontinuity, preventing the electric field from propagating further outwards, thereby achieving low-loss transmission of the waveguide transition.

[0042] In summary, the low-loss transition between the top-split E-plane gap waveguide and the rectangular waveguide proposed in this embodiment allows for gaps in the waveguide profile, reducing the requirements for processing and assembly accuracy. It has the advantages of simple structure, reduced processing and assembly difficulty, and wide bandwidth with low loss.

[0043] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the scope of the claims of the invention.

Claims

1. A low-loss non-planar split gap waveguide-rectangular waveguide transition structure, characterized in that, include: The E-plane gap waveguide (4) and the E-plane rectangular waveguide (3) have the same height and their upper and lower bottom surfaces share the same plane. The cross-section of the E-plane gap waveguide (4) is located at the top of the E-plane gap waveguide (4), and the cross-section of the E-plane rectangular waveguide (3) is located at the center of the E-plane rectangular waveguide (3). The E-plane rectangular waveguide (3) is divided into two symmetrical parts, which are denoted as: the first half-height E-plane rectangular waveguide (31) and the second half-height E-plane rectangular waveguide (32); The transition structure is made of upper and lower structures, which are respectively referred to as: upper cavity (1) and lower cavity (2); There is a step at the connection between the upper cavity (1) and the lower cavity (2) and the E-plane gap waveguide (4) and the E-plane rectangular waveguide (3); The E-plane gap waveguide (4) and the second half-height E-plane rectangular waveguide (32) are fabricated on the upper cavity (1), and the first half-height E-plane rectangular waveguide (31) is fabricated on the lower cavity (2); the E-plane gap waveguide (4) specifically includes: a full-height E-plane rectangular waveguide groove, a stepped structure of the lower cavity (2) on both sides of the full-height E-plane rectangular waveguide groove, and a bed of nails structure (5) located on top of the stepped structure of the lower cavity (2); The top of the stepped structure of the upper cavity 1 on both sides of the first half-height E-plane rectangular waveguide (31) includes a pair of L-shaped choke slots (6). The L-shaped choke slots are symmetrically distributed about the central axis of the first half-height E-plane rectangular waveguide (31). The two ends of the L-shaped choke slots (6) are connected to the side wall of the first half-height E-plane rectangular waveguide (31) and the vertical side wall (82) of the stepped structure of the upper cavity (1), respectively.

2. The low-loss irregularly split gap waveguide-rectangular waveguide transition structure according to claim 1, characterized in that, The height of the stepped structure of the upper cavity (1) is equal to the sum of the height of the stepped structure of the lower cavity (2) and the height of the nail bed structure (5).

3. The low-loss irregularly split gap waveguide-rectangular waveguide transition structure according to claim 2, characterized in that, The height of the nail bed structure (5) is one-quarter of a wavelength.

4. The low-loss heterogeneous split gap waveguide-rectangular waveguide transition structure according to claim 3, characterized in that, The first sidewall of the nail bed structure (5) is coplanar with the vertical sidewall (81) of the stepped structure of the lower cavity (2).

5. The low-loss heterogeneous split gap waveguide-rectangular waveguide transition structure according to claim 4, characterized in that, The second sidewall of the nail bed structure (5) is coplanar with the sidewall of the full-height E-plane rectangular waveguide groove.

6. The low-loss heterogeneous split gap waveguide-rectangular waveguide transition structure according to claim 5, characterized in that, The two vertical sections of the L-shaped choke (6) are of equal length.

7. A low-loss heterogeneous split gap waveguide-rectangular waveguide transition structure according to claim 6, characterized in that, The length, width, and depth of the two vertical grooves of the L-shaped choke (6) are all within the range of 1 / 16 to 1 / 8 of the wavelength.

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