Terahertz branch waveguide coupler with reconfigurable coupling degree

Abstract

The invention belongs to the field of terahertz waveguide devices, and particularly provides a terahertz branch waveguide coupler with a reconfigurable coupling degree, which is used for realizing the reconfigurable design of the coupling degree of the branch waveguide coupler. The filter comprises two main waveguides arranged side by side, a staggered branch waveguide structure located between E surfaces of the two main waveguides, and a rectangular compensation cavity correspondingly connected with the staggered branch waveguide structure, the rectangular compensation cavity is introduced on the basis of the staggered branch waveguide structure, the resonance mode of the TE201 mode of the staggered branch waveguide structure is compensated through the rectangular compensation cavity, and correction of the center frequency and the coupling unevenness is achieved; more importantly, the reconfigurable design of the coupling degree of the coupler in the terahertz frequency band is achieved for the first time through the design of the rectangular compensation cavity, and it is guaranteed that the coupler has excellent bandwidth performance and coupling unevenness at the same time.

Description

Technical Field

[0001] This invention belongs to the field of terahertz waveguide devices, specifically providing a terahertz branch waveguide coupler with reconfigurable coupling. Background Technology

[0002] Waveguide directional couplers are four-port passive components used for power distribution or detection. They have advantages such as high port matching, high isolation, low insertion loss, and high power capacity. They are widely used in electronic countermeasures, communication systems, radar systems, and measuring instruments, and play an indispensable role in important microwave measuring instruments such as vector network analyzers and reflectometers.

[0003] Existing E-plane branched waveguide directional couplers are designed based on traditional branched waveguide structures. Their operating bandwidth can be increased by increasing the number of branches. However, as the number of branches increases, the height of each branch waveguide decreases drastically, significantly increasing the manufacturing difficulty and cost. For example, in 2017, Alvaro Gonzalez et al. disclosed a 12-branched waveguide directional coupler operating in the 275 GHz–500 GHz range in the IEEE Transactions on Terahertz Science and Technology article “275–500 GHz Waveguide Diplexer to Combine Local Oscillators for Different Frequency Bands.” Under the premise of meeting the required operating bandwidth, the height of each branch waveguide was only 30 micrometers, making manufacturing extremely difficult, and manufacturing errors had a significant impact on the coupler's performance.

[0004] In recent years, with the in-depth research on high-frequency resonant modes in branched waveguide couplers, misaligned branched waveguides have been proposed. Utilizing their higher-order resonant modes, the bandwidth of branched waveguide couplers can be maximized while reducing fabrication difficulty. For example, patent document CN117525802A discloses an ultra-wideband E-plane branched waveguide coupler based on a misaligned branched waveguide structure, the structure of which is as follows... Figure 1As shown, the structure includes two main waveguides arranged side by side and a misaligned branch waveguide structure located between the E-planes of the two main waveguides. The main waveguides are standard rectangular waveguides with a wide side dimension of a and a narrow side dimension of b. The height of the misaligned branch waveguide structure is defined as the signal propagation direction within the main waveguides, and the height of the misaligned branch waveguide structure is denoted as h. The width of the misaligned branch waveguide structure is defined as the wide side dimension a of the main waveguides, and a stepped misalignment is formed along the height direction at a / 2 of the width, with the stepped misalignment offset denoted as m. The distance between the two main waveguides is t, which is the length of the misaligned branch waveguide structure. The period of the misaligned branch waveguide structure is w. The ultra-wideband E-plane branch waveguide coupler utilizes the high-order resonant mode TE201 to achieve a coupler effect across the entire frequency band, and the fabrication difficulty is greatly simplified compared to traditional structures.

[0005] However, whether it is an E-plane branch waveguide directional coupler designed based on traditional branch waveguide structures or a novel branch waveguide coupler designed based on misaligned branch waveguides, the device can only achieve a single coupling degree after fabrication. However, in application scenarios such as power detection and step attenuators, couplers with multiple coupling degrees are usually required. Therefore, how to achieve reconfigurable coupling degree of branch waveguide couplers in broadband is the research focus of this invention. Summary of the Invention

[0006] The purpose of this invention is to provide a terahertz branch waveguide coupler with reconfigurable coupling, so as to realize the reconfigurable design of the branch waveguide coupler.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A terahertz branched waveguide coupler with reconfigurable coupling includes: two main waveguides arranged side by side, a misaligned branched waveguide structure located between the E-planes of the two main waveguides, and a rectangular compensation cavity corresponding to and connected to the misaligned branched waveguide structure; wherein, the rectangular compensation cavity is connected to the misaligned branched waveguide structure in a one-to-one correspondence, all rectangular compensation cavities are located on the same side, and each rectangular compensation cavity and the misaligned branched waveguide structure are arranged in the same direction, with the misaligned branched waveguide structure located at the middle position of the rectangular compensation cavity.

[0009] Furthermore, the stepped misalignment offset of the misaligned branch waveguide structure is m, and the width of the rectangular compensation cavity is s. m and s are used as adjustment parameters to jointly realize the coupling degree reconstruction of the terahertz branch waveguide coupler.

[0010] Furthermore, the height of the rectangular compensation cavity is the same as that of the misaligned branch waveguide structure, and the length of the rectangular compensation cavity is greater than its height and width.

[0011] Furthermore, the number of misaligned branch waveguide structures is N, N≥1, and the staircase misalignment direction of all misaligned branch waveguide structures is consistent.

[0012] Furthermore, all main waveguides are standard rectangular waveguides.

[0013] Based on the above technical solution, the beneficial effects of the present invention are as follows:

[0014] This invention proposes a terahertz branch waveguide coupler with reconfigurable coupling. It employs a novel compensation technique, introducing a rectangular compensation cavity into the misaligned branch waveguide structure. The rectangular compensation cavity compensates for the resonant mode of the TE201 mode in the misaligned branch waveguide structure, thereby correcting the center frequency and coupling unevenness. More importantly, the rectangular compensation cavity design achieves reconfigurable coupling of the coupler in the terahertz band for the first time, while ensuring that the coupler simultaneously possesses excellent bandwidth performance and coupling unevenness. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of an ultrawideband E-plane branched waveguide coupler based on a misaligned branched waveguide structure in the prior art.

[0016] Figure 2 This is a schematic diagram of the terahertz branch waveguide coupler with reconfigurable coupling in this invention.

[0017] Figure 3 This is a prototype model diagram of a terahertz branch waveguide coupler with reconfigurable coupling in an embodiment of the present invention, wherein 1 is the upper cavity, 2 is the lower cavity, and 3 is the reconfiguration knob device.

[0018] Figure 4 This is a schematic diagram illustrating the working principle of a prototype model of a terahertz branch waveguide coupler with reconfigurable coupling in an embodiment of the present invention.

[0019] Figure 5 This is a schematic diagram of the protruding tooth-like structure in the prototype model of the terahertz branch waveguide coupler with reconfigurable coupling in an embodiment of the present invention.

[0020] Figure 6 The figure shows the simulation results of the traditional 4-branch waveguide coupler in Comparative Example 1.

[0021] Figure 7 The figure shows the simulation results of the ultrawideband E-plane branched waveguide coupler based on the misaligned branched waveguide structure in Comparative Example 2.

[0022] Figure 8 The figure shows the simulation results of the terahertz branch waveguide coupler with reconfigurable coupling in an embodiment of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0024] This embodiment proposes a terahertz branch waveguide coupler with reconfigurable coupling. It improves upon the misaligned branch waveguide structure of the TE201 resonant mode by introducing a wide-side compensation cavity to correct the center frequency shift of the coupler and avoid deterioration of coupling unevenness. More precisely, the structure of the terahertz branch waveguide coupler with reconfigurable coupling is as follows: Figure 2 As shown, it includes: two main waveguides arranged side by side, a staggered branch waveguide structure located between the E-planes of the two main waveguides, and a rectangular compensation cavity corresponding to and connected to the staggered branch waveguide structure; the number of staggered branch waveguide structures is N, N≥1; the rectangular compensation cavities are connected one-to-one with the staggered branch waveguide structures, and all rectangular compensation cavities are located on the same side; each rectangular compensation cavity and the staggered branch waveguide structure are arranged in the same direction, and the staggered branch waveguide structure is located in the middle of the rectangular compensation cavity; the height of the rectangular compensation cavity is the same as that of the staggered branch waveguide structure, and the length of the rectangular compensation cavity is greater than its height and width;

[0025] In terms of working principle:

[0026] This invention improves upon the misaligned branch waveguide structure. The misaligned branch waveguide structure excites the TE201 resonant mode through the discontinuity introduced by the stepped misalignment. The location of the transmission zero point is closely related to the coupling strength of the TE201 resonant mode, that is, the coupling degree is strongly correlated with the characteristic impedance of the branch waveguide. Therefore, this invention introduces a rectangular compensation cavity corresponding to the misaligned branch waveguide structure; the signal propagation direction within the main waveguide is taken as the height direction of the misaligned branch waveguide structure, and the height of the misaligned branch waveguide structure is denoted as h; the width dimension of the main waveguide is a, and the width direction of the main waveguide is taken as the width direction of the misaligned branch waveguide structure, and the width of the misaligned branch waveguide structure is the same as the width dimension a of the main waveguide, and a stepped misalignment is formed along the height direction at a / 2 of the width, and the stepped misalignment offset is denoted as m; the distance between the two main waveguides is t, which is the length of the misaligned branch waveguide structure; the width of the rectangular compensation cavity is s, and the height is h, which is the same as that of the misaligned branch waveguide structure; through the coordinated design of the stepped misalignment offset m of the novel misaligned branch waveguide in this invention and the width s of the rectangular compensation cavity, the position of the transmission zero point can be flexibly adjusted, providing theoretical support for realizing the reconfigurable coupling degree of the terahertz ultra-wideband branch waveguide coupler.

[0027] In a traditional branched waveguide structure, assuming the height of the middle waveguide stub is h0 and the width is a, and the length of the branched waveguide between the two main waveguides is t, then the characteristic impedance Z0 of the branched waveguide is expressed as:

[0028]

[0029] Among them, Z TEM =120π, where λ0 is the wavelength corresponding to the working center frequency;

[0030] As the width of the branch waveguide increases, higher-order modes are introduced into the branch waveguide structure. The characteristic impedance Z0′ of the novel misaligned branch waveguide proposed in this invention can be expressed as:

[0031]

[0032] At this point, assuming that the characteristic impedances of the two branch waveguides are the same, i.e., Z0′=Z0, the relationship between the heights of the intermediate waveguide stubs of the two branch waveguides can be obtained as follows:

[0033]

[0034] In terms of operating frequency, the length t of the novel misaligned branch waveguide in the branched waveguide coupler proposed in this invention is related to the operating center frequency of the coupler, and is theoretically equal to λ0 and 4. Based on this, the structural parameters of the novel misaligned branch waveguide in this invention theoretically satisfy the following relationship:

[0035]

[0036] Based on the above theoretical derivation, this invention can correct the center frequency shift caused by the change in the offset at the center of the upper and lower coupler cavities by adjusting the width s of the rectangular compensation cavity, and avoid the deterioration of coupling non-flatness. Thus, it achieves reconfigurable coupling without sacrificing bandwidth performance or coupling non-flatness. Furthermore, it should be noted that the coordinated adjustment process of the stepped misalignment offset m and the width s of the rectangular compensation cavity can be completed by combining the above theoretical relationship with existing simulation optimization methods in this field.

[0037] The beneficial effects of the present invention will be explained in detail below with reference to simulation tests.

[0038] like Figure 3 The diagram shows a prototype model of the terahertz branch waveguide coupler with reconfigurable coupling in this embodiment. A three-layer partitioning method is used to maximize the preservation of common cavity sections, simplifying the coupling reconfiguration process. The prototype model includes: an upper cavity 1, a lower cavity 2, and a reconfiguration knob device 3. The upper cavity 1 and lower cavity 2 are closed to form the main waveguide and the upper half of the staggered branch waveguide structure located between the two main waveguide E-planes. The reconfiguration knob device 3 selects a protruding tooth-like structure corresponding to a preset coupling degree and inserts it into a designated position in the upper and lower cavities, forming the lower half of the staggered branch waveguide structure between the two main waveguide E-planes and a rectangular compensation cavity connected to it. Figure 4As shown. In this embodiment, the switching of six pre-defined toothed structures is achieved through a reconfigurable knob device, corresponding to a reconfigurable coupler design with coupling degrees of 10dB, 12dB, 14dB, 16dB, 18dB, and 20dB respectively.

[0039] More accurately, such as Figure 5 The diagram shows the above-mentioned protruding tooth structure. The size design of the protruding tooth structure can achieve coordinated adjustment of the stepped misalignment offset m and the width s of the rectangular compensation cavity. For example, in this embodiment, h = 0.21 mm, t = 0.45 mm, a = 1.5 mm, and m = 0.11 mm are set. The size parameters of the protruding tooth structure with coupling degrees of 10 dB, 12 dB, 14 dB, 16 dB, 18 dB, and 20 dB are shown in Table 1. Among them, four misaligned branch waveguide structures are realized by three protruding teeth. They are labeled from left to right as the first misaligned branch waveguide structure to the fourth misaligned branch waveguide structure. w1 to w3 represent the distance between the branches of adjacent misaligned branch waveguide structures, n1 to n3 represent the height of the corresponding misaligned branch waveguide structure, and s1 and s2 represent the width of the corresponding misaligned branch waveguide structure.

[0040] Table 1

[0041] Coupling [n1 (mm)] [n2 (mm)] [n3 (mm)] [s1 (mm)] [s2 (mm)] w1 (mm) <![CDATA[w2(mm)]]> <![CDATA[w3(mm)]]> 10dB 0.185 0.21 0.18 0.31 0.31 0.485 0.49 0.5 12dB 0.08 0.21 0.1 0.28 0.26 0.57 0.49 0.6 14dB 0.105 0.21 0.13 0.1 0.18 0.67 0.49 0.49 16dB 0.09 0.21 0.12 0.05 0.04 0.69 0.49 0.49 18dB 0.02 0.21 0.105 0.04 0.03 0.74 0.49 0.49 20dB 0.01 0.21 0.095 0.035 0.02 0.75 0.49 0.49

[0042] Using a traditional 4-branch waveguide coupler as comparative example 1, and an ultrawideband E-plane branch waveguide coupler based on a staggered branch waveguide structure as comparative example 2, as follows... Figure 6 , Figure 7 , Figure 8 The figures shown are simulation results for Comparative Examples 1, 2, and 3, respectively. As can be seen from the figures, the present invention, based on the rectangular compensation cavity design, can compensate for the resonant mode of the TE201 mode, and achieve correction of the center frequency and coupling unevenness. The coupling unevenness is controlled within ±0.3dB across the entire D-band (110GHz~170GHz), and the coupling degree is reconfigurable. Compared with Comparative Examples 1 and 2, the present invention has excellent bandwidth and coupling unevenness while achieving coupling degree reconfigurability.

[0043] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A terahertz branched waveguide coupler with reconfigurable coupling, comprising: The system comprises two main waveguides arranged side by side, a staggered branch waveguide structure located between the E-planes of the two main waveguides, and a rectangular compensation cavity corresponding to and connected to the staggered branch waveguide structure; characterized in that the rectangular compensation cavity is connected to the staggered branch waveguide structure in a one-to-one correspondence, all rectangular compensation cavities are located on the same side, and each rectangular compensation cavity and the staggered branch waveguide structure are arranged in the same direction, with the staggered branch waveguide structure located in the middle position of the rectangular compensation cavity.

2. The terahertz branched waveguide coupler with reconfigurable coupling according to claim 1, characterized in that, The stepped misalignment offset of the misaligned branch waveguide structure is m, and the width of the rectangular compensation cavity is s. m and s are used as adjustment parameters to jointly realize the coupling degree reconstruction of the terahertz branch waveguide coupler.

3. The terahertz branched waveguide coupler with reconfigurable coupling according to claim 1, characterized in that, The height of the rectangular compensation cavity is the same as that of the misaligned branch waveguide structure, and the length of the rectangular compensation cavity is greater than its height and width.

4. The terahertz branched waveguide coupler with reconfigurable coupling according to claim 1, characterized in that, The number of misaligned branch waveguide structures is N, N≥1, and the stair misalignment direction of all misaligned branch waveguide structures is consistent.

5. The terahertz branch waveguide coupler with reconfigurable coupling according to claim 1, characterized in that, The main waveguides are all standard rectangular waveguides.

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