An ultrawideband H-plane waveguide T-junction and its design method

Abstract

This invention provides an ultra-wideband H-plane waveguide T-junction and its design method, belonging to the field of microwave passive device technology. The T-junction includes an H-plane waveguide T-junction body and a cylindrical metal pillar disposed within the junction region. This invention introduces a single cylindrical metal pillar as an auxiliary reflection source between the junction region and the branch point. Utilizing the principle of two-point reflection cancellation, the reflection amplitude is controlled by independently adjusting the height of the metal pillar, and the reflection phase is controlled by adjusting its longitudinal position. This allows the reflected wave from the metal pillar and the reflected wave from the T-junction itself to vectorly superimpose and cancel each other out at the input port, thereby achieving excellent impedance matching over an extremely wide frequency band. This invention features a simple structure, ease of fabrication, low cost, and good consistency. It exhibits a return loss better than -18dB across the entire 8GHz~16GHz frequency band and supports arbitrary power division ratio designs. Parameters can be scaled proportionally to wavelength and applied to different frequency bands, making it widely applicable in engineering applications.

Description

Technical Field

[0001] This invention relates to the field of microwave passive device technology, and in particular to an ultrawideband H-plane waveguide T-junction and its design method. Background Technology

[0002] In the field of microwave circuits and systems, the T-junction is a key passive device for power distribution and combining, and is widely used in radar, communication, and electronic warfare systems. Traditional T-junction power dividers typically consist of one input transmission line and two output transmission lines, achieving ideal impedance matching and power distribution at a specific center frequency. However, their inherent narrowband characteristics become a major technical bottleneck. When the operating frequency deviates from the center frequency, impedance matching deteriorates sharply, leading to increased port reflection loss and a significant decrease in transmission efficiency, failing to meet the ultra-wideband requirements of modern microwave systems.

[0003] To extend operating bandwidth, existing technologies primarily employ cascaded multi-stage impedance transformers or gradient line structures of specific shapes. While multi-stage impedance transformers can extend bandwidth to some extent, they significantly increase device size and weight, while also introducing more insertion loss. Gradient line structures, although relatively compact, are difficult and costly to manufacture, and are highly sensitive to manufacturing tolerances, making consistency difficult to guarantee. Furthermore, most existing broadband T-junction designs are optimized for specific frequency bands; once the design is finalized, its operating frequency range is fixed, making it difficult to adapt to the bandwidth requirements of different application scenarios through simple adjustments, thus lacking design flexibility and reconfigurability.

[0004] Meanwhile, in ultra-wideband applications, achieving extreme wideband matching from DC to high frequencies, maintaining amplitude and phase consistency of the output branches at both ends, and achieving miniaturization and low loss remain the main challenges. Therefore, there is an urgent need to provide a T-junction power distribution / combining structure that is simple in structure, easy to fabricate, capable of achieving ultra-wideband impedance matching, and meets the requirements of miniaturization and low loss. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies, such as narrow bandwidth of traditional T-junctions, large size of multi-stage impedance transformers, and difficulty in processing gradient line structures, and to provide an ultra-wideband H-plane waveguide T-junction and its design method that is simple in structure, easy to process, low in cost, and has excellent broadband matching performance.

[0006] According to one objective of the present invention, an ultra-wideband H-plane waveguide T-junction is provided, comprising: The H-plane waveguide T-junction body consists of one input waveguide and two output waveguides intersecting at the H-plane to form a junction region; A cylindrical metal pillar is vertically disposed within the junction region and located between the input waveguide axis and the branch point; The height of the cylindrical metal pillar is less than the narrow side dimension of the waveguide and does not contact the opposite sidewall of the waveguide. The amplitude of its reflection coefficient is controlled by adjusting the height of the cylindrical metal pillar, and the phase of its reflection coefficient is controlled by adjusting the longitudinal position of the cylindrical metal pillar. This allows the reflected wave from the cylindrical metal pillar to vector cancel out the reflected wave from the T-junction body of the H-plane waveguide at the input port, thus achieving ultra-wideband impedance matching.

[0007] Furthermore, the cylindrical metal pillar is disposed on the center line of the wide side of the rectangular waveguide.

[0008] Furthermore, the reflection coefficient phase of the cylindrical metal column is close to +90°, and the reflection coefficient phase of the H-plane waveguide T-junction body is close to -90°.

[0009] Furthermore, the reflection coefficient amplitude of the cylindrical metal column is approximately equal to the reflection coefficient amplitude of the H-plane waveguide T-junction body.

[0010] Furthermore, the reflection frequency characteristics of the cylindrical metal pillar are approximately consistent with the reflection frequency characteristics of the H-plane waveguide T-junction body.

[0011] Furthermore, the H-plane waveguide T-junction body is a standard rectangular waveguide structure.

[0012] Furthermore, the cylindrical metal column is installed and fixed through the opening in the waveguide cover plate without changing the main structure of the waveguide.

[0013] Furthermore, the T-junction operates in the frequency band of 8GHz to 16GHz, and the input port return loss is ≤-18dB within the entire operating frequency band.

[0014] Furthermore, the height of the cylindrical metal column is 2mm, and the electrical length corresponding to the longitudinal position is equal to the narrow side dimension of the waveguide aperture, which is 10.16mm.

[0015] According to a second objective of the present invention, the present invention provides a design method for an ultrawideband H-plane waveguide T-junction, comprising the following steps: S1. Determine the dimensional parameters of the H-plane waveguide T-junction body according to the operating frequency band; S2. Simulation calculation of the reflection coefficient Γ of the H-plane waveguide T-junction in the operating frequency band. j The amplitude and phase characteristics; S3. Place a cylindrical metal pillar between the input waveguide axis and the branch point within the junction region, and adjust its height to achieve the desired reflection coefficient Γ. p The amplitude and Γ j The amplitudes are approximately equal; S4. Adjust the longitudinal position of the cylindrical metal column so that Γ pThe phase after electrical length transmission and Γ j The phase difference is approximately 180°; S5. Simulate and verify the return loss performance of the overall structure, and fine-tune the parameters of the metal column until the design specifications are met.

[0016] This invention overcomes the technical bottleneck of traditional T-junction narrowband matching, eliminating the need for bulky multi-stage impedance transformers or complex gradient line structures. Ultra-wideband impedance matching can be achieved simply by introducing a single cylindrical metal pillar in the junction region. This structure utilizes two independent degrees of freedom—the height and longitudinal position of the metal pillar—to precisely control the amplitude and phase of the reflected wave. Based on the principle of two-point reflection cancellation, the two reflected waves vectorly cancel each other out at the input port. Its structure is simple, the cylindrical shape allows for easy control of machining tolerances, and it is low-cost and highly consistent. It can be directly mounted via a waveguide cover without modifying the waveguide body, exhibiting excellent process compatibility. Furthermore, it features miniaturization, low loss, and supports designs with arbitrary power ratios. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of the ultra-wideband H-plane waveguide T-junction of the present invention; Figure 2 This is a schematic diagram showing the height and longitudinal position of the cylindrical metal column in this invention; Figure 3 This is a schematic diagram of a traditional H-plane waveguide T-junction. Figure 4 Simulation curves of return loss for a traditional H-plane waveguide T-junction in the 8GHz~16GHz frequency band; Figure 5 The simulation curves of the return loss of the ultra-wideband H-plane waveguide T-junction of this invention in the 8GHz~16GHz frequency band are shown.

[0019] In the figure: 1. Input waveguide; 2. First output waveguide; 3. Second output waveguide; 4. Junction region; 5. Cylindrical metal pillar. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0022] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0023] Example 1 like Figure 1 and Figure 2 As shown, this embodiment of an ultra-wideband H-plane waveguide T-junction includes an H-plane waveguide T-junction body and a cylindrical metal pillar 5, wherein: The H-plane waveguide T-junction consists of an input waveguide 1, a first output waveguide 2, and a second output waveguide 3 intersecting in the H-plane to form a junction region 4. A cylindrical metal pillar 5 is vertically positioned within the junction region 4, located between the axis of the input waveguide 1 and the branch point.

[0024] In waveguide theory, any structural abrupt change is equivalent to a lumped or distributed parallel admittance connected to the transmission line. A standard H-plane T-junction exhibits electric field concentration at the branch point, equivalent to a parallel inductive admittance Y. j Its reflection coefficient Γ jThe phase is typically close to -90° (i.e., the reflected wave phase lags), and the amplitude changes gradually with frequency. In this case, the cylindrical metal post 5 inserted at the center of the wide side of the rectangular waveguide primarily exhibits parallel capacitive admittance Y. p Its reflection coefficient Γ p The phase is close to +90° (the reflected wave phase is ahead), and the amplitude can be adjusted by changing the height of the metal column.

[0025] The total reflection coefficient Γ observed from the input port total for: Γ total =Γ j +Γ p e -j2βd ; Where β is the propagation constant and d is the longitudinal distance between the cylindrical metal column 5 and the branch point (i.e., the electrical length between the two reflecting surfaces).

[0026] To achieve destructive reflection, the following two conditions must be met simultaneously: 1. Amplitude condition: |Γ j |≈|Γ p |; 2. Phase condition: ∠Γ j +π≈∠(Γ p e -j2βd ; The core of this invention lies in the fact that the cylindrical metal column 5 serves as a distributed parameter structure, and its reflection coefficient Γ p The trend of frequency variation and the reflection coefficient Γ of the T-junction itself j The trends with frequency variation are basically consistent. Therefore, as long as the above amplitude and phase conditions are met at the center frequency, the vector difference between the two (the residual reflection after cancellation) can be kept very small within a relatively wide frequency band near the center frequency, thereby maintaining the return loss at a high level and achieving ultra-wideband matching.

[0027] The height h of the cylindrical metal column 5 is mainly used to adjust the reflection coefficient Γ. p The higher the altitude, the stronger the capacitance and the greater the reflection amplitude. The longitudinal position d is mainly used to adjust the phase of the reflected wave. By changing the path length of the reflected wave, Γ... p At the input port, exactly Γ j They are in phase, thus achieving complete cancellation. The relationship between the electrical length θ and the height h is: θ=(2π / λ) h; Where λ is the operating wavelength.

[0028] In a preferred embodiment of the present invention, an ultra-wideband H-plane waveguide T-junction operating in the 8GHz~16GHz frequency band is designed. A standard WR-90 rectangular waveguide is adopted, with a wide side dimension of 22.86mm and a narrow side dimension of 10.16mm. The cylindrical metal pillar 5 has a diameter of 2mm, a height h of 2mm, and an electrical length corresponding to the longitudinal position d equal to the narrow side dimension of the waveguide opening, 10.16mm.

[0029] like Figure 3 and Figure 4 As shown, traditional H-plane waveguide T-junctions exhibit poor return loss in the 8GHz~16GHz frequency range, and none meet the engineering application requirement of S11≤-18dB. However, as... Figure 5 As shown, the ultra-wideband H-plane waveguide T-junction of this invention exhibits excellent broadband matching performance with return loss almost always below -20dB across the entire 8GHz to 16GHz frequency band. Simultaneously, the power distribution ratio of the two output ports is close to 1:1, with good amplitude-phase consistency and insertion loss of less than 0.1dB.

[0030] It should be noted that the above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention. For example, by adjusting the width of the two output waveguides or introducing appropriate matching structures in the output waveguides, the present invention can achieve designs with arbitrary power distribution ratios; by scaling the waveguide dimensions and metal pillar parameters according to the wavelength ratio, the present invention can be applied to T-junction designs in microwave, millimeter-wave, and even terahertz frequency bands.

[0031] Compared with the prior art, the present invention has the following beneficial effects: This invention features a simple structure and is easy to manufacture. It only requires inserting a cylindrical metal pillar near the junction region, eliminating the need for complex multi-section gradient or multi-stage impedance transformation structures. The cylindrical shape is the simplest to machine and has the easiest tolerance control, resulting in low manufacturing costs and good consistency. Furthermore, the metal pillar can be directly installed through openings in the waveguide cover plate without altering the main waveguide structure, offering excellent process compatibility.

[0032] This invention offers superior broadband matching performance. Based on the principle of two-point reflection cancellation, it utilizes the two independent design degrees of freedom (height and longitudinal position) provided by a cylindrical metal pillar to precisely control the amplitude and phase of the reflected wave, allowing the two reflected waves to vectorly superimpose and cancel each other out at the input port. Since the reflection frequency characteristics of the metal pillar are approximately identical to those of the T-junction itself, it maintains excellent impedance matching performance over an extremely wide frequency band. Within an octave range of 8GHz to 16GHz, the input port return loss is almost entirely below -20dB, far superior to traditional T-junctions.

[0033] This invention boasts strong scalability and versatility, with a universal design principle. By scaling waveguide dimensions and metal pillar parameters according to wavelength, it can be easily applied to waveguide T-junction designs across different frequency bands. Furthermore, this structure supports designs with arbitrary power division ratios, meeting the needs of various application scenarios.

[0034] This invention features miniaturization and low loss. Compared to multi-stage impedance transformers, its structure is more compact, with higher space utilization, significantly reducing the size and weight of the device. Furthermore, due to the introduction of only a single metal pillar obstacle, insertion loss is extremely low, effectively improving the system's transmission efficiency.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A T-junction for an ultrawideband H-plane waveguide, characterized in that, include: The H-plane waveguide T-junction body consists of one input waveguide and two output waveguides intersecting at the H-plane to form a junction region; A cylindrical metal pillar is vertically disposed within the junction region and located between the input waveguide axis and the branch point; The height of the cylindrical metal pillar is less than the narrow side dimension of the waveguide and does not contact the opposite sidewall of the waveguide. The amplitude of its reflection coefficient is controlled by adjusting the height of the cylindrical metal pillar, and the phase of its reflection coefficient is controlled by adjusting the longitudinal position of the cylindrical metal pillar. This allows the reflected wave from the cylindrical metal pillar to vector cancel out the reflected wave from the T-junction body of the H-plane waveguide at the input port, thus achieving ultra-wideband impedance matching.

2. The ultra-wideband H-plane waveguide T-junction according to claim 1, characterized in that, The cylindrical metal pillar is positioned on the center line of the wide side of the rectangular waveguide.

3. The ultra-wideband H-plane waveguide T-junction according to claim 1, characterized in that, The reflection coefficient of the cylindrical metal column is close to +90°, and the reflection coefficient of the H-plane waveguide T-junction body is close to -90°.

4. The ultra-wideband H-plane waveguide T-junction according to claim 1, characterized in that, The reflection coefficient amplitude of the cylindrical metal column is approximately equal to the reflection coefficient amplitude of the H-plane waveguide T-junction body.

5. The ultra-wideband H-plane waveguide T-junction according to claim 1, characterized in that, The reflection frequency characteristics of the cylindrical metal pillar are approximately the same as those of the H-plane waveguide T-junction body.

6. The ultra-wideband H-plane waveguide T-junction according to claim 1, characterized in that, The H-plane waveguide T-junction body is a standard rectangular waveguide structure.

7. The ultra-wideband H-plane waveguide T-junction according to claim 1, characterized in that, The cylindrical metal column is installed and fixed through the opening in the waveguide cover plate without changing the main structure of the waveguide.

8. The ultra-wideband H-plane waveguide T-junction according to claim 1, characterized in that, The T-junction operates in the frequency band of 8GHz to 16GHz, and the input port return loss is ≤-18dB within the entire operating frequency band.

9. The ultra-wideband H-plane waveguide T-junction according to claim 8, characterized in that, The cylindrical metal column has a height of 2 mm, and the electrical length corresponding to the longitudinal position is equal to the narrow side dimension of the waveguide aperture, which is 10.16 mm.

10. A design method for an ultrawideband H-plane waveguide T-junction, characterized in that, Includes the following steps: S1. Determine the dimensional parameters of the H-plane waveguide T-junction body according to the operating frequency band; S2. Simulation calculation of the reflection coefficient Γ of the H-plane waveguide T-junction in the operating frequency band. j The amplitude and phase characteristics; S3. Place a cylindrical metal pillar between the input waveguide axis and the branch point within the junction region, and adjust its height to achieve the desired reflection coefficient Γ. p The amplitude and Γ j The amplitudes are approximately equal; S4. Adjust the longitudinal position of the cylindrical metal column so that Γ p The phase after electrical length transmission and Γ j The phase difference is approximately 180°; S5. Simulate and verify the return loss performance of the overall structure, and fine-tune the parameters of the metal column until the design specifications are met.

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