A novel self-correcting waveguide coupler

Abstract

The application belongs to the technical field of sub-terahertz-terahertz communication, and relates to a waveguide coupler, and particularly provides a novel self-correcting waveguide coupler, which comprises two main waveguides arranged side by side, a coupling window structure connected between the two main waveguides, and two rows of parallel branches, the two rows of parallel branches are respectively arranged on the outer side surfaces of the main waveguides and symmetrically arranged; the application starts from the electromagnetic field regulation and control mechanism level, proposes a distributed branch compensation mechanism based on the parallel branch array with a specific topological structure introduced in the coupling area of the main waveguide, so that the structure can effectively utilize the phase reconstruction capability of the branch unit and dynamically offset the electromagnetic field distribution distortion caused by the machining error.

Description

Technical Field

[0001] This invention belongs to the field of Asia-Pacific Hertz-Terahertz communication technology, and relates to waveguide couplers, specifically providing a novel self-calibrating waveguide coupler. Background Technology

[0002] With the rapid development of 6G communication, terahertz imaging, and high-precision radar systems, the demand for devices operating in the millimeter-wave to terahertz frequency band (above 100 GHz) has increased dramatically. Within this band, the limitations in processing accuracy and the surge in high-frequency losses caused by the shrinking size of traditional microwave devices have become increasingly prominent. In particular, the performance of waveguide passive devices is significantly more sensitive to machining errors. As a core component for signal distribution, power combining, and system calibration, the performance stability of waveguide couplers directly determines the reliability of the entire communication link. However, in the terahertz band, the physical size of waveguide structures has shrunk to the sub-millimeter level, placing extremely stringent requirements on cavity processing accuracy. The misalignment of the upper and lower cavities must be controlled within ±5 μm, while the repeatability of existing commercial precision CNC machine tools is generally at the ±10 μm level. This gap between manufacturing capabilities and design requirements has become one of the main bottlenecks restricting the practical application of terahertz devices.

[0003] Traditional waveguide couplers are mostly based on rectangular waveguide structures, using coupling slots or branch lines to distribute energy. In the terahertz band, the limitations of this design are mainly reflected in two aspects: First, the miniaturization of the coupling structure at high frequencies leads to an exponential amplification of the disturbance to the electromagnetic field distribution caused by manufacturing errors. For example, when the operating frequency exceeds 200 GHz, the width of some coupling slots usually needs to be compressed to below 50 μm. At this time, a manufacturing deviation of ±10 μm can cause the coupling coefficient to fluctuate by more than ±1.5 dB. Second, cavity assembly errors (such as misalignment of upper and lower cavities) will disrupt the continuity of the waveguide boundary, triggering higher-order mode excitation and parasitic resonance, resulting in fluctuations in insertion loss and deterioration of flatness in the passband. To address these challenges, the industry has attempted to improve tolerance through structural optimization or additional tuning mechanisms. For example, mechanical adjustment of the dielectric pillar position can compensate for manufacturing errors, but the moving parts introduced by this approach are prone to micro-discharge under high-frequency vibration environments, and the adjustment response speed is insufficient to meet real-time correction requirements. Another approach uses electromagnetic compensation technology, adding a resonant unit outside the coupling region to offset the error by adjusting the resonant frequency. However, this method requires an additional 30% or more of the layout area and results in a bandwidth reduction of approximately 40%, making it difficult to meet the needs of wideband systems. More fundamentally, existing technologies mostly focus on "passively adapting" to errors rather than achieving "active correction" through physical mechanisms, leading to an irreconcilable contradiction between compensation efficiency and bandwidth characteristics. In recent years, surface plasmon polariton (SSPP) coupling structures, due to their unique field localization effect and anti-interference capabilities, have been considered a breakthrough direction for terahertz coupler design. SSPP waveguides achieve surface wave propagation through a periodic subwavelength structure, with the field distribution concentrated near the metal-dielectric interface. Theoretically, they are less sensitive to lateral misalignment of the cavity. However, in practical applications, the performance of SSPP couplers is still limited by two major problems: First, the dispersive characteristics of the SSPP mode lead to significant phase mismatch during broadband coupling, especially in multi-section cascaded designs. Manufacturing errors can cause cumulative phase deviations between sections, ultimately resulting in increased passband ripple. Second, the SSPP structure is extremely sensitive to assembly errors. Misalignment between the upper and lower cavities can disrupt the symmetry of the surface wave propagation path, causing an irreversible decrease in coupling efficiency. When the misalignment exceeds ±10µm, the in-band ripple of a conventional SSPP coupler will exceed 1.5dB and cannot be recovered through subsequent tuning. Summary of the Invention

[0004] The purpose of this invention is to provide a novel self-calibrating waveguide coupler. Starting from the electromagnetic field modulation mechanism, a distributed stub compensation mechanism is proposed. By introducing a parallel stub array with a specific topology into the coupling region of the main waveguide, the structure can effectively utilize the phase reconstruction capability of the stub units to dynamically offset the electromagnetic field distribution distortion caused by processing errors.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A novel self-calibrating waveguide coupler includes two main waveguides arranged side by side and a coupling window structure connecting the two main waveguides. The self-calibrating waveguide coupler further includes two rows of parallel stubs, which are respectively and symmetrically arranged on the outer surfaces of the main waveguides. A coordinate system is established with the wide side direction of the main waveguide as the X-axis, the long side direction as the Z-axis, and the signal propagation direction within the main waveguide as the Y-axis. The number of parallel stubs in each row is N+1, where N is the number of coupling windows. Along the XOY plane, each parallel stub is arranged perpendicular to the outer surface of the main waveguide, and there is a corresponding coupling window between two adjacent parallel stubs.

[0007] Furthermore, the X-axis dimensions of the parallel stubs are all the same, specifically λ / 8, where λ is the wavelength corresponding to the center operating frequency of the waveguide coupler.

[0008] Furthermore, the Z-axis dimensions of the parallel stubs are all the same, specifically the long side dimension of the main waveguide.

[0009] Furthermore, the main waveguide is a rectangular waveguide, and the main waveguide and the coupling window structure together constitute an E-plane branch waveguide directional coupler.

[0010] Based on the above technical solution, the beneficial effects of the present invention are as follows:

[0011] This invention provides a novel self-calibrating waveguide coupler, creatively proposing a parallel stub design. Through the design of a parallel stub array, an adaptive electromagnetic field reconstruction network is formed, which not only improves the electric field strength in the coupling region of the waveguide coupler but also enhances the coupler's adaptability to various manufacturing errors. Compared to the complex external tuning mechanisms required by traditional waveguide couplers, this invention achieves a fully integrated self-calibration function. Within a misalignment range of ±10μm, the coupler not only maintains efficient energy coupling but also ensures in-band insertion loss and frequency response flatness. Furthermore, this self-calibrating waveguide coupler exhibits significant advantages in wideband performance. Therefore, this invention, through its innovative parallel stub structure, enables the coupler to maintain stable operating characteristics over a wide frequency range, significantly reducing insertion loss fluctuations caused by frequency variations, ensuring reliable signal transmission, optimizing the coupler's transmission efficiency, and making the waveguide coupler more flexible and efficient in practical applications.

[0012] More importantly, this invention effectively improves the assembly error tolerance of waveguide couplers. In traditional designs, the reliability of signal transmission is often limited by stringent processing precision. However, the self-calibration mechanism of this invention significantly expands the manufacturing process and provides a new technical path for the large-scale, low-cost manufacturing of terahertz devices. By reducing the reliance on high-precision machining, the self-calibrating waveguide coupler in this invention provides a more convenient solution for industrial production and will promote the widespread application of related technologies.

[0013] In summary, the self-calibrating waveguide coupler provided by this invention not only improves the tolerance for assembly errors and the stability of operation, but also provides a solid foundation for the future development of terahertz communication, imaging, and high-precision radar systems. Attached Figure Description

[0014] Figure 1 This is a top view of the model of the novel self-calibrating waveguide coupler in this invention.

[0015] Figure 2 This is a three-dimensional structural diagram of the novel self-calibrating waveguide coupler of the present invention.

[0016] Figure 3 The simulation results of S21 and S31 of the novel self-calibrating waveguide coupler in this invention are shown. Detailed Implementation

[0017] 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.

[0018] This embodiment provides a novel self-calibrating waveguide coupler, the structure of which is as follows: Figure 1 and Figure 2 As shown, the self-calibrating waveguide coupler includes two main waveguides arranged side by side and a coupling window structure connecting the two main waveguides (E-plane). Taking the 170GHz~260GHz frequency band as an example, the main waveguides are rectangular waveguides, and the two rectangular main waveguides cover the entire frequency band of 170GHz~260GHz. Functionally, four ports are defined. Port1 is the input port, which receives electromagnetic waves from the signal source; Port2 is a through port, which transmits a signal with the same amplitude as the input signal but without passing through the coupling window; Port3 is the coupling port, which is used to output a signal with power distribution; and Port4 is the isolation port, designed to maintain high isolation characteristics in the system and avoid signal interference and feedback. Through the design of the coupling window structure, after the input electromagnetic wave enters from Port1, the coupling window evenly distributes the signal to Port2 and Port3, ensuring the output of a constant amplitude signal, thereby effectively meeting the needs of signal processing.

[0019] More importantly, this embodiment introduces several parallel stubs into the traditional waveguide coupler to implement a dynamic compensation mechanism, effectively offsetting the phase shift and field distribution distortion caused by lateral misalignment due to assembly errors of the upper and lower cavities; such as Figure 1 and Figure 2 As shown, a coordinate system is established with the wide side of the main waveguide as the X-axis, the long side of the main waveguide as the Z-axis, and the signal propagation direction inside the main waveguide as the Y-axis. The side of the main waveguide connected to the coupling window structure (E-plane) is called the inner side of the main waveguide, and the other side is called the outer side of the main waveguide. The self-calibrating waveguide coupler also includes two rows of parallel stubs, which are respectively arranged on the outer side of the main waveguide and symmetrically. The number of parallel stubs in each row is N+1, where N is the number of coupling windows. Along the XOY plane, each parallel stub is arranged perpendicular to the outer side of the main waveguide, and there is a corresponding coupling window between two adjacent parallel stubs.

[0020] The X-axis dimensions of all parallel stubs are identical, specifically λ / 8, where λ is the wavelength corresponding to the center operating frequency of the waveguide coupler. The Z-axis dimensions of all parallel stubs are also identical, specifically the same as the long side dimension (Z-axis dimension) of the main waveguide. It should also be noted that in traditional waveguide couplers, multiple coupling windows are not uniformly distributed along the Y-axis, and the gap dimensions (Y-axis dimension) of each coupling window are not entirely the same, requiring simulation optimization based on the actual application scenario. Therefore, in the parallel stub structure proposed in this invention, as long as parallel stubs are provided on both sides (Y-axis direction) of each coupling window, the specific position and Y-axis dimension of each parallel stub can be adaptively adjusted using conventional simulation optimization methods in the art to match the corresponding coupling window design.

[0021] In practical applications, waveguide couplers are fabricated using the H-plane. When there is a lateral (Y-axis) misalignment error in the assembly of the upper and lower cavities, the physical gap size (Y-axis dimension) of the coupling window structure will change accordingly, causing phase shift and field distortion. Simultaneously, the Y-axis dimension of the parallel stub structures located on both sides of the coupling window will also adjust with the change in the gap size of the coupling window structure. This dynamic compensation mechanism effectively counteracts the phase shift and field distortion caused by lateral misalignment, ensuring that the power distribution accuracy of the output port is stably maintained within ±0.2dB across the entire frequency band. Figure 3The figure shows the simulation results of S21 and S31 of the self-calibrating waveguide coupler in this embodiment. As can be seen from the figure, when the upper and lower cavities are misaligned by ±10μm, the flatness deterioration is controlled within 0.2dB. Compared with the neutral state (red line), the coupler exhibits excellent robustness when subjected to processing errors. This shows that the parallel stub design in this invention enables the coupler to adapt to complex assembly conditions and ensures efficient and stable signal transmission.

[0022] 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 novel self-calibrating waveguide coupler, comprising two main waveguides arranged side-by-side and a coupling window structure connecting the two main waveguides; characterized in that, The self-calibrating waveguide coupler also includes two rows of parallel stubs, which are respectively arranged symmetrically on the outer surface of the main waveguide. A coordinate system is established with the wide side direction of the main waveguide as the X-axis direction, the long side direction of the main waveguide as the Z-axis direction, and the signal propagation direction inside the main waveguide as the Y-axis direction. The number of parallel stubs in each row is N+1, where N is the number of coupling windows. Along the XOY plane, each parallel stub is arranged perpendicular to the outer surface of the main waveguide, and there is a corresponding coupling window between two adjacent parallel stubs.

2. The novel self-calibrating waveguide coupler according to claim 1, characterized in that, The X-axis dimensions of all the parallel stubs are the same, specifically λ / 8, where λ is the wavelength corresponding to the center operating frequency of the waveguide coupler.

3. The novel self-calibrating waveguide coupler according to claim 1, characterized in that, The Z-axis dimensions of the parallel stubs are all the same, specifically the long side dimension of the main waveguide.

4. The novel self-calibrating waveguide coupler according to claim 1, characterized in that, The main waveguide is a rectangular waveguide, and the main waveguide and the coupling window structure together form an E-plane branch waveguide directional coupler.

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