Ultra-wideband terahertz waveguide attenuator and implementation method

Abstract

The application discloses an ultra-wideband terahertz waveguide attenuator and an implementation method thereof, which comprises the following steps: adopting tantalum nitride as a waveguide attenuator material; the attenuator comprises a support bottom plate, a side transition structure, a middle rectangular plate and a top branch, the support bottom plate is located at the bottom, and the remaining parts are constructed based on the support bottom plate; the side transition structure is in a slope shape, is used for optimizing impedance matching and improving transmission performance; the middle rectangular plate is located at a central position, so as to enhance signal attenuation efficiency. Through the synergistic design of the material and the structure, the application can realize efficient signal attenuation, and simultaneously meet the requirements of wide frequency band, good matching and practicability. The application adopts tantalum nitride in combination with an integrated structure, improves attenuation efficiency, and enhances mechanical stability and electrical contact reliability. The slope transition structure improves impedance gradient matching, expands the working bandwidth, supports 275GHz to 575GHz ultra-wideband application, and the relative bandwidth reaches 70%, so that the problems of narrow bandwidth, large volume and complex use of the traditional waveguide attenuator are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of terahertz, in particular to a super wideband terahertz waveguide attenuator and implementation method. BACKGROUND

[0002] A radio frequency attenuator is a kind of passive device used in the field of radio frequency and microwave, which functions to attenuate a radio frequency signal with excessive power for subsequent processing, such as application in testing of power devices: the output power of a 220GHz frequency band power amplifier measured is too large, for example, 400mW (26dBm), which exceeds the measuring instrument range of 200mW (23dBm). At this time, in order to avoid damaging the measuring instrument, a level attenuator is needed to attenuate the power to the range for measurement, and then the measured result is added to the attenuation value of the attenuator used.

[0003] The radar, communication and other transceiver systems in the terahertz frequency band (0.1THz-10THz, i.e. 100GHz-10000GHz) use waveguides for transmission, and there are standard waveguide interfaces.

[0004] At present, the mainstream waveguide attenuators are as follows:

[0005] The first type of attenuator is based on a terahertz waveguide directional coupler to realize the function of attenuation. The waveguide directional coupler is a four-port device, one port is the input port, the second port is the through port, the third port is the coupling port, and the fourth port is the isolation port. The attenuation function of the waveguide directional coupler is realized based on the coupling port. The signal is input from the first port, and a part of the energy is coupled to the coupling port through a small hole or a branch. Because the coupled energy is small, the waveguide directional coupler has the function of attenuator. For example, Comparative Document 1 (Publication No. CN118231984B, Patent Name: A High-Power Waveguide Attenuator) and Comparative Document 2 (Publication No. CN105070995B, Patent Name: A New Waveguide Attenuator). This type of attenuator has the following shortcomings:

[0006] 1. The structure is large in size, which needs to occupy system space

[0007] 2. The attenuator of this type is realized in a metal module, which requires high-precision machining process, and the attenuation value after machining is fixed and cannot be changed. The attenuation amount cannot be controlled according to the needs. (0049 in Comparative Document 1 shows that the attenuation of this attenuator is 30dB)

[0008] 3. Because the waveguide directional attenuator is a four-port device, only the input port and the coupling port are used for attenuation, and the through port and the isolation port still need to be connected to a load or a wave-absorbing material, which is troublesome to use. (Claim 7 of Comparative Literature 1)

[0009] 4. The bandwidth of this type of attenuator cannot be made super wideband. For example, in Comparative Literature 1, the operating frequency band is 50GHz-75GHz, the bandwidth is 25GHz, and the relative bandwidth is 40%, relative bandwidth=bandwidth (25GHz) / center frequency (62.525GHz).

[0010] The second form of attenuator is to insert a metal sheet into the waveguide gap through a mechanical control such as a telescopic arm, thereby achieving the effect of attenuation. For example, Comparative Literature 3 (Publication No. CN222763160U, Patent Name: A continuously adjustable high-power waveguide attenuator) and Comparative Literature 4 (Publication No. CN118801068A, Patent Name: An adjustable waveguide attenuator and a manufacturing method thereof). Compared with the first form of attenuator whose attenuation value cannot be adjusted, this form of attenuator can achieve the effect of adjustable attenuation by mechanically controlling the degree of insertion of the metal attenuation sheet into the waveguide gap. This type of attenuator has the following disadvantages:

[0011] 1. The structure is large and complex, as the mechanical structure such as the telescopic arm needs to be adjusted, which occupies a large amount of space and requires precise scales for adjustment.

[0012] 2. The bandwidth of this type of attenuator also cannot be made super wideband. For example, in Comparative Literature 3, the bandwidth is E-band, 60GHz-90GHz, the bandwidth is 30GHz, and the relative bandwidth is 40%. In Comparative Literature 4, the operating frequency band is 170GHz-260GHz, the bandwidth is 90GHz, and the relative bandwidth is 41.8%.

[0013] In addition, the waveguide attenuator can be in the form of a packaged attenuator chip. This form is to package the attenuator chip in a cavity and transmit through a transition structure using a waveguide. This form of attenuator adjusts the attenuation value through voltage, which requires additional power supply; at the same time, the packaging design of the chip needs to be considered, which is more troublesome than other ways; and it also cannot achieve super wideband and small size. SUMMARY

[0014] The purpose of the present application is to overcome the shortcomings of the prior art, provide a super wideband terahertz waveguide attenuator and implementation method, and solve the problems of narrow operating bandwidth, difficulty in achieving super wideband performance, complex structure, dependence on mechanical adjustment or additional power supply, resulting in integration difficulty and inconvenience of use of existing terahertz waveguide attenuators.

[0015] The purpose of the present application is achieved by the following technical solutions:

[0016] A method for implementing an ultrawideband terahertz waveguide attenuator includes the following:

[0017] Tantalum nitride is used as the waveguide attenuator material;

[0018] The attenuator comprises a supporting base plate, side transition structures, a central rectangular plate, and a top stub. The supporting base plate is located at the bottom of the overall structure, upon which the rest of the structure is built. The side transition structures are sloped to optimize impedance matching and improve transmission performance. The central rectangular plate is located in the center to enhance signal attenuation efficiency. The top stub increases structural strength and ensures a tight fit with the waveguide wall.

[0019] Based on the operating frequency band and attenuation requirements, optimize the dimensional parameters of each component, including the length of the support base plate. Width b, height h, the slope angle and length of the side transition structure, and the size of the top branch.

[0020] As a preferred embodiment, the specific dimensions of the supporting base plate are: length =3.39mm, width b=0.538mm, height h=0.055mm.

[0021] As a preferred embodiment, the dimensional parameters of the intermediate rectangular plate are length and... Consistent, height a=1.016 mm, thickness w2=0.085 mm.

[0022] As a preferred embodiment, the thickness w3 of the top branch is 0.085 mm.

[0023] As a preferred embodiment, the slope length of the side transition structure To meet impedance gradient matching conditions and achieve low reflection and ultra-wideband performance in the 275GHz to 575GHz frequency band, its length must satisfy:

[0024] ;in, The slope length of the side transition structure; To correspond to the lowest operating frequency GHz guided wave wavelength, The calculation formula is:

[0025] ;in, m / s is the speed of light For operating frequency, This is the cutoff frequency for the transmission environment. The impedance gradient matching utilizes a continuously varying local characteristic impedance along the ramp direction. Implementation, in which These are the coordinates of the propagation direction along the slope from the starting point to the end point. Slope length. The impedance is determined by the higher impedance at the starting end. To the terminal characteristic impedance Rate of change: when The impedance change is sufficiently gradual, effectively suppressing local reflection of electromagnetic waves in the impedance transition region and reducing the integral reflection coefficient across the entire frequency band. The terminal characteristic impedance... Matching the dominant mode of the transmission environment (such as rectangular waveguides) The characteristic impedance of the modulus is expressed as:

[0026] ;in, The free-space wave impedance has a range of values. 377 is preferred. .

[0027] As a preferred method, the attenuation value can be adjusted by increasing the length of the support base plate or by cascading multiple attenuators.

[0028] As a preferred approach, the attenuation value is related to the length of the supporting base plate. and material loss factor The following relationship exists between them:

[0029] ;in, This represents the total attenuation value. This is the unit conversion factor, and its value range is... Preferred Used to convert neper to decibel, to meet ; To support the length of the base plate along the propagation direction;

[0030] Propagation attenuation constant The electrical conductivity of tantalum nitride material and operating frequency Together, under the good conductor approximation, the following conditions are met:

[0031] ;in, The conductivity of tantalum nitride, H / m is the permeability of free space. This refers to the operating frequency.

[0032] As a preferred method, two or more unit attenuators are directly placed in the waveguide and cascaded. The attenuation value of a single stage is 7dB, and the total attenuation value is accumulated by cascading.

[0033] An ultrawideband terahertz waveguide attenuator:

[0034] This includes the supporting base plate, side transition structure, middle rectangular plate, and top branches;

[0035] Tantalum nitride is used as a material due to its excellent electrical conductivity and mechanical stability;

[0036] The support base plate is rectangular in shape, which makes it easy to place in the waveguide;

[0037] The side transition structure is sloped to optimize impedance matching and improve transmission performance;

[0038] The central rectangular plate is located in the center position to enhance signal attenuation efficiency;

[0039] The top branch increases structural strength and ensures a tight fit with the waveguide wall;

[0040] The dimensions have been optimized to fit the operating frequency band from 275GHz to 575GHz, achieving ultra-wideband, miniaturization, flat attenuation curve and adjustable characteristics.

[0041] As a preferred embodiment, the operating frequency band is 275GHz to 575GHz, with a relative bandwidth of 70%, and the attenuation value is set to 7dB. The attenuation flatness is controlled within ±1dB in the ultra-wideband range.

[0042] The present invention has at least the following beneficial effects:

[0043] This invention proposes an ultra-wideband terahertz waveguide attenuator and its implementation method. Through the synergistic design of materials and structure, it achieves efficient signal attenuation while also meeting the requirements of wide bandwidth, good matching, and practicality. Using tantalum nitride as the loss medium, and combining it with an integrated structure of a supporting base plate, a ramp-shaped side transition, a central rectangular attenuator, and a top reinforcing branch, it not only improves attenuation efficiency but also enhances the mechanical stability and electrical contact reliability of the device in the waveguide. The ramp transition structure effectively improves impedance gradient matching, significantly expanding the operating bandwidth to support ultra-wideband applications from 275GHz to 575GHz, achieving a relative bandwidth of 70%. This solves the problems of narrow bandwidth, large size, and complex use of traditional waveguide attenuators. The overall structure requires no additional power supply or mechanical adjustment, facilitating mass production and system integration, and is suitable for high-density, wideband terahertz communication, radar, and test and measurement applications. Attached Figure Description

[0044] To reveal the technical details of the embodiments of the present invention, the accompanying drawings involved in the embodiments will be briefly described below. It should be emphasized that these drawings only present several embodiments of the present invention and should not be considered as defining the scope of the invention. For those skilled in the art, other related drawings can still be derived based on these drawings without inventive effort.

[0045] Figure 1 This is an overall diagram of the attenuator structure;

[0046] Figure 2 This is a simulation performance diagram of the attenuator according to an embodiment of the present invention;

[0047] Figure 3 This is a schematic diagram of the attenuator's exploded structure;

[0048] Figure 4 Simulation models of ramp transition structures: without ramp transition structure (left); with ramp transition structure (right).

[0049] Figure 5 Comparison of simulation results for the ramp transition structure;

[0050] Figure 6 Simulation models of the central rectangular plate: with the central rectangular plate (left); without the central rectangular plate (right);

[0051] Figure 7 The simulation results for the middle rectangular plate are shown in the comparison chart.

[0052] Figure 8 The simulation results for the attenuator length are shown in the figure.

[0053] Figure 9 This is a multi-stage attenuator cascade model;

[0054] Figure 10 The simulation results of cascading multi-stage attenuators are shown in the figure.

[0055] Figure 11 Waveguide field comparison diagram: without attenuator;

[0056] Figure 12 Comparison of waveguide conduction fields: Add attenuator;

[0057] Figure 13 This is an example of an attenuator application. Detailed Implementation

[0058] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.

[0059] In the following description, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. However, it should be understood that the present disclosure is not limited to the specific forms shown herein. Rather, it should be understood to encompass various variations, equivalents, and / or alternatives to the embodiments of the present disclosure. In illustrating the drawings, the same reference numerals will be used to denote similar components.

[0060] In this disclosure, terminology is used to describe specific embodiments and does not constitute a limitation thereof. In this context, the use of the singular form also encompasses the plural form, unless otherwise expressly stated herein. In the course of description, terms such as “comprising” or “having” are intended to indicate the presence of features, quantities, steps, operations, structural components, parts, or combinations thereof, and do not preclude the possibility or addition of one or more other features, quantities, steps, operations, structural components, parts, or combinations thereof.

[0061] It should be clarified that while the following description provides detailed specific information to aid in a comprehensive understanding of the exemplary embodiments, those skilled in the art will recognize that the exemplary embodiments can be implemented even without these specific details. For example, the system may be illustrated using block diagrams to avoid excessive detail that could obscure the clarity of the example. In other cases, to maintain the clarity of the example, unnecessary details of well-known processes, structures, and techniques may be omitted.

[0062] A method for implementing an ultrawideband terahertz waveguide attenuator includes the following:

[0063] Tantalum nitride (TaN) is used as the waveguide attenuator material because it has good electrical conductivity and mechanical stability, and can effectively absorb electromagnetic signals in the terahertz band.

[0064] The attenuator comprises a supporting base plate, side transition structures, a central rectangular plate, and a top stub. The supporting base plate is located at the bottom of the overall structure, upon which the rest of the structure is built. The side transition structures are sloped to optimize impedance matching and improve transmission performance. The central rectangular plate is located in the center to enhance signal attenuation efficiency. The top stub increases structural strength and ensures a tight fit with the waveguide wall.

[0065] Based on the operating frequency band and attenuation requirements, optimize the dimensional parameters of each component, including the length of the support base plate. The width b, height h, slope angle and length of the side transition structure, and size of the top branch are determined to achieve ultra-wide bandwidth, miniaturization, flat attenuation curve and adjustable characteristics.

[0066] Terahertz waveguide attenuators achieve their attenuation function by fabricating tantalum nitride (TaN) into a specific geometry. When electromagnetic waves propagate in the waveguide, they first pass through a ramp-shaped side transition structure, achieving impedance gradient matching, reducing reflection, and improving broadband transmission performance. The signal then passes through the central rectangular plate region, which is composed of tantalum nitride with high conductivity. Under the influence of the terahertz field, ohmic losses are generated, dissipating some electromagnetic energy and achieving signal attenuation. The supporting base plate serves as the foundation of the overall structure; its length directly affects the attenuation path and total attenuation value. Flexible attenuation design can be achieved by adjusting the length or cascading units. The top branch ensures that the device remains stably supported and in close contact with the waveguide wall even at a small scale, improving structural reliability and electrical contact continuity. By optimizing the dimensional parameters of each part, the overall structure achieves ultra-wideband, low-reflection, flat, and adjustable attenuation within the 275–575 GHz frequency band. Simultaneously, the structure is compact, requires no external power supply, and is easy to integrate and use.

[0067] In a preferred embodiment, the operating frequency band is 275GHz to 575GHz, the relative bandwidth reaches 70%, the attenuation value is set to 7dB, and the attenuation flatness is controlled within ±1dB in the ultra-wideband range.

[0068] Ultra-wideband terahertz waveguide attenuators are based on the synergistic effect of structure and materials. When a terahertz signal propagates in the waveguide, it first encounters the sloping transition structure on both sides. This gradual design smoothly guides the electromagnetic wave from the waveguide into the attenuator body, effectively reducing signal reflection caused by abrupt interface changes, thereby improving transmission efficiency and laying the foundation for ultra-wideband operation. After entering, the signal mainly passes through the central rectangular plate of tantalum nitride. Due to the excellent conductivity of tantalum nitride, it generates significant ohmic loss under the action of high-frequency alternating electromagnetic fields, converting some electromagnetic energy into heat energy, thus achieving stable signal attenuation. The supporting base plate not only supports the entire structure but also determines the effective operating length of the attenuator in the propagation direction. By adjusting its length or cascading multiple units, the total attenuation can be flexibly controlled. The design of the top branch enhances the mechanical strength of the overall structure, ensuring that the device remains firmly attached to the inner wall of the waveguide even in its small size, avoiding poor contact or performance fluctuations due to loosening. Through meticulous optimization of the dimensional parameters of each component, the entire device achieves excellent impedance matching and uniform attenuation response in a wide frequency range from 275 GHz to 575 GHz, with a relative bandwidth of 70%, an attenuation value set at 7 dB, and attenuation variation controlled within ±1 dB throughout the entire frequency band. It exhibits excellent broadband flatness characteristics and has the advantages of compact structure, no power supply required, and ease of use, making it suitable for highly integrated terahertz system applications.

[0069] In a preferred embodiment, see Figure 3 The specific dimensions of the supporting base plate are its length. =3.39mm, width b=0.538mm, height h=0.055mm. The slope angle and length of the side transition structure were optimized using HFSS simulation software to achieve the best impedance matching effect. The dimensional parameters of the middle rectangular plate are length and... Consistent with height a = 1.016 mm and thickness w2 = 0.085 mm. The thickness w3 of the top branch is 0.085 mm. This is achieved by increasing the length of the supporting base plate. Increasing the diameter from 3.39mm to 4.65mm improves the attenuation value from 7dB to approximately 9dB.

[0070] The structural parameters of the terahertz waveguide attenuator have been meticulously designed and optimized through simulation to achieve high-performance broadband attenuation. The supporting base plate, serving as the foundation of the entire device, has dimensions of 3.39 mm in length, 0.538 mm in width, and 0.055 mm in height. These dimensions not only ensure structural stability but also precisely match the internal space of the waveguide, ensuring reliable installation and participation in electromagnetic field control. The sloping transition structures on both sides have been repeatedly optimized using HFSS simulation software to determine suitable slope angles and lengths. This allows electromagnetic waves to transition smoothly upon entering the attenuator, effectively reducing signal reflections caused by abrupt structural changes, thereby improving transmission performance and expanding the operating bandwidth. The central rectangular plate, with the same length as the supporting base plate and a height of 1.016 mm, extends fully to the region of strongest electric field in the waveguide's dominant mode. Combined with 0.085 mm thick tantalum nitride material, it significantly enhances the absorption capacity of electromagnetic energy and is the core component for achieving a 7 dB attenuation effect. The top branch, also 0.085 mm thick, not only forms a continuous structure with the central rectangular plate but also enhances the overall mechanical strength, ensuring that the device remains tightly fitted to the waveguide inner wall even at a small scale, preventing loosening or poor contact. When higher attenuation is required, the length of the support base plate is increased from 3.39 mm to 4.65 mm, extending the propagation path of electromagnetic waves in the lossy material, thereby increasing the attenuation value from 7 dB to approximately 9 dB. This demonstrates that the structure can flexibly adjust its attenuation performance through simple dimensional adjustments in practical applications, balancing high performance, scalability, and engineering practicality.

[0071] To further optimize the energy dissipation efficiency of tantalum nitride (TaN) attenuation structures in the terahertz band, this invention proposes an equivalent loss region depth model based on the skin effect. This model is used to guide the thickness of the intermediate rectangular plate. The determination of the skin depth ensures that electromagnetic wave energy is primarily absorbed within the effective loss depth of the material, avoiding material waste or insufficient absorption. Under the influence of high-frequency electromagnetic fields, the current in a conductor tends to concentrate near the surface, forming the skin effect. For highly conductive materials like tantalum nitride, the skin depth directly determines the main area of ​​electromagnetic energy penetration and loss in the terahertz band. If the thickness of the central rectangular plate is less than the skin depth, energy cannot be fully absorbed.

[0072] Therefore, the equivalent loss region depth is defined. for:

[0073] ;in, It is the depth of the equivalent loss zone, in meters (m); It is the propagation attenuation constant. When the material thickness... At that time, more than 98% of the electromagnetic energy will be dissipated in the material, achieving efficient absorption.

[0074] In a preferred embodiment, the side transition structure is configured by setting a ramp length. This achieves gradual impedance matching to reduce electromagnetic wave reflections in the 275 GHz to 575 GHz frequency band, thereby improving broadband transmission performance. It is important to clarify the ramp length in the side transition structure. This is not the length of the supporting base plate. The side transition structures on both sides of the central rectangular plate are symmetrical, including the central waveguide wall section and two ramp sections on the left and right. The ramp length here refers to the horizontal extension length of each ramp in the electromagnetic wave propagation direction, that is, the distance along the z-axis from the thicker (thinner) end of the ramp to the thinner (thicker) end. There is a ramp of length L on each of the left and right sides, whose function is to achieve gradual impedance matching. Design Requirements This ensures that the impedance change is sufficiently gradual at the lowest operating frequency of 275GHz, effectively suppressing reflections and improving broadband transmission performance in the 275–575GHz band.

[0075] Specifically, propagation coordinates are defined along the slope direction. The local characteristic impedance of this structure Higher impedance from the starting end Characteristic impedance that varies continuously to the terminal Slope length This determines the rate of change of impedance: if If the impedance is too short, the abrupt change in impedance will cause strong reflection of electromagnetic waves in the transition region; if... Sufficient length results in a gradual change in impedance, which can significantly suppress reflection.

[0076] To achieve effective matching across the entire frequency band, the ramp length must satisfy:

[0077] ;in Minimum operating frequency GHz corresponds to the guided wave wavelength. The calculation formula is:

[0078] ;in, m / s is the speed of light The operating frequency (Hz) The cutoff frequency of the transmission environment, measured in Hertz (Hz), is determined by the geometry and dielectric properties of the transmission structure (such as a rectangular waveguide). It is the local characteristic impedance along the slope direction, starting from the higher impedance at the beginning. Waveguide characteristic impedance that gradually changes to the terminal This creates a smooth impedance transition; This is the characteristic impedance of the dominant mode of the rectangular waveguide, measured in ohms (Ω), i.e., the termination impedance. Matching the dominant mode of the transmission environment (such as rectangular waveguides) The inherent characteristic impedance of the modulus is expressed as:

[0079] ;in, The free-space wave impedance has a range of values. 377 is preferred. Through the above design, the impedance is... The smooth transition within the length minimizes the integral of reflected energy over a wide bandwidth, resulting in a return loss better than 15dB, thus achieving ultra-wideband, low VSWR transmission performance.

[0080] The terahertz waveguide attenuator's side transition structure, through a cleverly designed ramp length L, achieves smooth impedance matching from high to low frequencies, significantly reducing electromagnetic wave reflections in the 275GHz to 575GHz band and improving broadband transmission performance. Specifically, defining the propagation coordinate z along the ramp direction, the structure's local characteristic impedance Z(z) changes from a higher impedance at the initial end... The standard waveguide characteristic impedance gradually changes to the terminal. This gradual design avoids the strong reflection problem caused by traditional abrupt structures. The ramp length L is a key parameter: if L is too short, the impedance change is too drastic, leading to strong reflection; while a sufficiently long L can make the impedance change more gradual, effectively suppressing the reflection phenomenon.

[0081] To ensure good impedance matching across the entire operating frequency band, the ramp length L needs to meet a certain condition: L should be greater than or equal to one-quarter of the guided wave wavelength corresponding to the lowest operating frequency. This ensures that the impedance change is sufficiently slow at the lowest operating frequency of 275 GHz, allowing for a smooth transition of electromagnetic waves and reducing reflections. The characteristic impedance Z(z) gradually transitions from the high impedance at the beginning to the standard waveguide characteristic impedance at the end. This creates a smooth transition region. Termination impedance It matches the inherent characteristic impedance of the rectangular waveguide master mode (such as the TE_10 mode) to ensure efficient signal transmission throughout the entire frequency band.

[0082] Through the above design, the side transition structure not only achieves a smooth transition from high impedance to standard waveguide characteristic impedance, but also minimizes reflection energy, resulting in a return loss better than 15dB. This enables ultra-wideband, low VSWR transmission performance in the 275GHz to 575GHz frequency band. This optimized design allows the entire system to maintain stable and efficient signal transmission over a wide bandwidth, while improving the overall system reliability and practicality. Ultimately, through careful design and optimization, this attenuator not only possesses high-performance broadband matching capabilities but also allows for flexible adjustment of the attenuation value, making it suitable for various high-density, wide-band terahertz applications.

[0083] In a preferred embodiment, the attenuation value is adjusted by increasing the length of the support base plate or by cascading attenuators. Increasing the length of the support base plate or using a cascading approach allows for flexible adjustment of the attenuation value of the terahertz waveguide attenuator to meet the needs of different application scenarios. When electromagnetic waves pass through tantalum nitride material, energy loss occurs due to its conductivity, and this loss accumulates as the signal propagates through the material. When the length of the support base plate increases, the tantalum nitride attenuation region in the middle also extends in the propagation direction, resulting in a longer loss path for the electromagnetic wave and thus enhancing the overall attenuation effect. For example, increasing the length from 3.39 mm to 4.65 mm can increase the attenuation value from 7 dB to approximately 9 dB. This method is equivalent to lengthening the absorption region and is a direct and effective method for adjusting the attenuation through geometric dimension control. Furthermore, multiple standardized attenuation units can be connected in series and placed in the waveguide to form a cascaded structure. Each unit provides a fixed attenuation (e.g., 7dB). As the signal passes through multiple units sequentially, the attenuation effect accumulates progressively, and the total attenuation is the sum of the attenuation values ​​of each unit. For example, two cascaded units can achieve an attenuation of approximately 14dB. This cascading method does not require structural redesign, facilitates modular use, and is particularly suitable for systems requiring large attenuation or flexible configuration. Both methods do not rely on external power supplies or complex mechanical structures, offering advantages such as simple implementation, stable performance, and high reliability, while maintaining both adjustable attenuation and broadband performance.

[0084] In a preferred embodiment, the attenuation value (in dB) is related to the length of the support base plate. and material loss factor The following relationship exists between them:

[0085] ;in, This represents the total attenuation value, expressed in decibels (dB). This is the unit conversion factor, and its value range is... ,for Used to convert neper (Np) to decibel (dB) to satisfy ; The length of the base plate along the propagation direction is measured in meters (m).

[0086] Propagation attenuation constant The electrical conductivity of tantalum nitride material and operating frequency Together, under the good conductor approximation, the following conditions are met:

[0087] ;in, The electrical conductivity (S / m) of tantalum nitride H / m is the permeability of free space. The operating frequency is Hz.

[0088] The attenuation of a terahertz waveguide attenuator is closely related to its structural dimensions and material properties. When an electromagnetic wave propagates in the waveguide and passes through an attenuation structure made of tantalum nitride, the material's conductivity causes ohmic loss under the influence of a high-frequency alternating electromagnetic field. This loss converts some electromagnetic energy into heat, dissipating it and thus attenuating the signal. This loss effect is not instantaneous but accumulates as the signal travels a longer distance within the material. Therefore, the length of the support plate along the propagation direction directly affects the overall attenuation—the longer the length, the longer the path the signal travels in the attenuating material, the more energy is absorbed, and the greater the overall attenuation. Simultaneously, the conductivity of tantalum nitride itself determines its "absorption capacity" for electromagnetic waves; higher conductivity results in stronger loss at the same frequency. Furthermore, the operating frequency also affects the attenuation effect; higher frequencies exhibit a more pronounced skin effect, concentrating energy on the material surface and leading to increased attenuation per unit length. In summary, the total attenuation value is determined by the inherent loss characteristics of the material and the geometric length of the device. By reasonably selecting material parameters and precisely controlling the length of the support base plate, the attenuation can be accurately designed and flexibly adjusted to meet the specific attenuation level requirements of different application scenarios.

[0089] In a preferred embodiment, by cascading two or more unit attenuators in a waveguide, the attenuation of a single stage is 7dB, and the cascading allows the total attenuation to be accumulated. By sequentially connecting two or more identical attenuator units in series within a waveguide, the total attenuation can be flexibly expanded; this method is called cascading. Each attenuator unit is made of tantalum nitride, has fixed structural dimensions and material properties, and can generate stable energy loss for the passing terahertz signal; a single stage can achieve an attenuation effect of approximately 7dB. When the electromagnetic wave passes through the first unit, its power is attenuated once; as it continues to propagate into the second unit, it undergoes the same loss process again, further reducing the power. Since each unit acts independently and has consistent performance, the total attenuation effect is the sum of the attenuation values ​​of each unit. For example, cascading two 7dB units can achieve a total attenuation of approximately 14dB, three close to 21dB, and so on. This cascading method does not require complex adjustments to individual devices; simply increasing the number of units as needed allows for modular expansion of the attenuation. Meanwhile, the units are naturally connected by waveguides, resulting in a compact structure that requires no additional power supply or mechanical adjustment. It has the advantages of simple implementation, stable performance, and easy integration, making it particularly suitable for terahertz system applications that require large dynamic range attenuation or flexible configuration of attenuation.

[0090] In a preferred embodiment, the attenuator can be directly used in a WR4.3 standard waveguide without additional installation or adjustment. The terahertz waveguide attenuator is designed with compatibility with standard waveguide systems in mind, allowing direct use in a WR4.3 standard waveguide without additional installation structures or on-site adjustments. Its overall dimensions precisely match the internal cavity of the WR4.3 waveguide, with the support base plate, side transition structure, and top branch forming a self-aligned mechanical structure. When electromagnetic waves propagate in the waveguide, upon encountering the attenuator structure, they sequentially pass through the impedance transition region and loss region along a preset path, achieving stable signal attenuation. The entire process requires no changes to the waveguide interface or the addition of fixing components. This "plug-and-play" design greatly simplifies the usage process, avoiding the complex calibration and mechanical adjustments required by traditional adjustable attenuators, while improving system reliability and repeatability. It is particularly suitable for rapid deployment and replacement in high-frequency, highly integrated terahertz testing and communication systems.

[0091] In a preferred embodiment, the performance of all attenuators was verified using HFSS electromagnetic simulation software to ensure excellent performance over the ultra-wideband range. After the design was completed, all performance parameters of the terahertz waveguide attenuator were comprehensively verified using HFSS (High Frequency Structure Simulator) electromagnetic simulation software. HFSS is a high-precision three-dimensional electromagnetic field simulation tool capable of realistically reproducing the propagation, reflection, and loss behavior of electromagnetic waves in complex metal structures at the terahertz frequency band. By establishing an accurate three-dimensional model of the attenuator in the WR4.3 waveguide, including all details such as the supporting base plate, the ramp transition structure, the intermediate rectangular plate, and the top branches, and setting parameters such as the conductivity of the tantalum nitride material, the simulation can accurately predict the actual operating performance of the device in the 275GHz to 575GHz wideband range. The simulation results focused on verifying whether the return loss was sufficiently low (i.e., low reflection), whether the insertion loss was stable, whether the attenuation flatness was controlled within ±1dB, and whether the overall attenuation met the design target. This pre-simulation verification method can optimize structural parameters before actual manufacturing, avoid trial and error costs, and ensure that the final device has good impedance matching, stable attenuation characteristics and high reliability under ultra-wideband conditions, thereby ensuring its effective application in terahertz systems.

[0092] An ultrawideband terahertz waveguide attenuator:

[0093] This includes the supporting base plate, side transition structure, middle rectangular plate, and top branches;

[0094] Tantalum nitride (TaN) is used as the material due to its excellent electrical conductivity and mechanical stability;

[0095] The support base plate is rectangular in shape, which makes it easy to place in the waveguide;

[0096] The side transition structure is sloped to optimize impedance matching and improve transmission performance;

[0097] The central rectangular plate is located in the center position to enhance signal attenuation efficiency;

[0098] The top branch increases structural strength and ensures a tight fit with the waveguide wall;

[0099] The dimensions have been optimized to fit the operating frequency band from 275GHz to 575GHz, achieving ultra-wideband, miniaturization, flat attenuation curve and adjustable characteristics.

[0100] The ultra-wideband terahertz waveguide attenuator achieves efficient and stable signal attenuation through the synergistic design of structure and materials. The device uses tantalum nitride (TaN) as the core material, which possesses moderate conductivity and good mechanical strength, effectively absorbing terahertz wave energy while facilitating fabrication into miniaturized structures. The entire attenuator consists of a supporting base plate, side transition structures, a central rectangular plate, and a top branch, and is embedded within a WR4.3 standard waveguide. Upon entering the waveguide, the electromagnetic wave first passes through the sloping side transition structures on both sides. This gradual design ensures a smooth impedance transition, significantly reducing signal reflection and thus extending the operating bandwidth to support ultra-wideband applications from 275GHz to 575GHz. The signal then passes through the central tantalum nitride rectangular plate, the main loss region, where ohmic losses occur under the influence of high-frequency electromagnetic fields, converting some energy into heat and achieving signal attenuation. The rectangular support base plate not only facilitates positioning and installation but also determines the length of the attenuation path; its dimensions allow for flexible control of the attenuation amount. The top branch enhances the overall structural rigidity, preventing deformation or loosening of the device within a small space, thus improving stability and repeatability. All structural parameters have been optimized through HFSS simulation, achieving wide bandwidth, low reflection, flat attenuation, and scalable performance while ensuring miniaturization. It requires no additional power supply or mechanical adjustment, offering advantages such as plug-and-play capability, high reliability, and ease of integration, making it suitable for high-frequency, highly integrated terahertz communication, radar, and test systems.

[0101] In a preferred embodiment, the operating frequency band is 275GHz to 575GHz, with a relative bandwidth of 70%, and the attenuation value is set to 7dB. The attenuation flatness is controlled within ±1dB in the ultra-wideband range. The specific dimensions of the supporting base plate are: length l = 3.39mm, width b = 0.538mm, and height h = 0.055mm. The slope angle and length of the side transition structure are optimized using HFSS simulation software to achieve the best impedance matching effect. The dimensions of the middle rectangular plate are: length a = 1.016mm, width w1 = 0.127mm, and height c = 0.847mm.

[0102] In summary, the waveguide attenuator material of this invention is tantalum nitride (TaN), and the attenuator structure is as follows: Figure 1 As shown. In one embodiment, an ultra-wideband terahertz waveguide attenuator with an operating frequency band of 275GHz-575GHz is provided. The operating bandwidth is 300GHz, the relative bandwidth reaches 70%, the attenuation value is 7dB, and the attenuation flatness within the ultra-wideband range is ±1dB. Wherein, l=3.39mm, h=0.055mm, b=0.538 mm, w1=0.127mm, a=1.016 mm, c=0.847mm, w2=0.085mm, w3=0.085mm, and it can be directly placed in a WR4.3 standard waveguide. Specific dimensions correspond to...Figure 3 As shown. Based on the above parameters, the following is obtained: Figure 2 The simulation performance diagram of the attenuator is shown.

[0103] The overall attenuator structure mainly consists of five parts:

[0104] 1. Support base plate: The support base plate is located at the bottom of the overall structure. It is a cuboid with length l, width b, and height h, which facilitates its placement in the waveguide. The rest of the structure is designed based on the support base plate, and its length l is the total length of the entire attenuator structure.

[0105] 2. Side Transition Structure: The side transition structure is a crucial part of the attenuator. Its ramped transition optimizes impedance matching and improves overall transmission performance, while also providing some attenuation. The following simulation uses the electromagnetic simulation software HFSS to simulate the function of the ramped transition structure, comparing the performance differences between structures with and without a ramped transition. The simulation model is as follows: Figure 4 As shown.

[0106] Simulation results are as follows Figure 5 As shown, the results indicate that in the 275GHz-575GHz frequency range, the S11 without a ramp transition structure is approximately -6dB, while the S11 with a ramp transition structure is approximately -18dB. The simulation results show that the ramp transition structure significantly optimizes the S11 level, improving it by approximately 12dB. In terms of transmission efficiency, without a ramp transition structure, 25% of the input signal is reflected back. For example, with a 100mW input signal, 25mW of signal returns to the input port, potentially causing direct burnout of the input device. In contrast, with the ramp transition design, only 1.5% of the signal is reflected back to the input port. For example, with a 100mW input signal, only 1.5mW of signal returns to the input port, causing no damage to the input.

[0107] 3. The central rectangular plate, located at the center of the overall structure, is where the waveguide transmission field is strongest, thus improving attenuation efficiency. The electromagnetic simulation software HFSS is used to simulate the function of the central rectangular plate, comparing the performance differences with and without it. The simulation model is established as follows: Figure 6 As shown.

[0108] Simulation results are as follows Figure 7As shown, the results indicate that in the 275GHz-575GHz frequency range, the signal attenuation (S21) is approximately -3dB without the intermediate rectangular plate structure, and approximately -7dB with the intermediate rectangular plate structure. The simulation results demonstrate that the design of the intermediate rectangular plate structure significantly improves the S21 level. From the perspective of attenuation efficiency, without the intermediate rectangular plate, the attenuation value is 3dB, meaning 50% of the signal is attenuated; for example, a 100mW input signal results in approximately a 50mW output signal. With the intermediate rectangular plate, the attenuation value is 7dB, meaning 80% of the signal is attenuated; for example, a 100mW input signal results in approximately a 20mW output signal. This shows that, with the overall structural length remaining constant, the design of the intermediate rectangular plate can improve the attenuation efficiency of the attenuator.

[0109] 4. Top branch: The top branch increases the overall structural strength, making the overall structure less prone to deformation and ensuring that the side of the attenuator can be tightly attached to the waveguide wall, thus improving the robustness of the overall structure. This structural design has no impact on the RF attenuation performance of the attenuator.

[0110] The attenuation value of the attenuator of this invention is adjustable, and there are two methods:

[0111] The first method: Increase the overall length during the design phase. The value of increases the absorption area of ​​the signal, thereby improving the attenuation efficiency. Figure 8 yes Simulation results at 3.39mm and 4.65mm indicate that the attenuator length is suitable for the 275GHz-575GHz range. When the attenuator length increases from 3.39mm to 4.65mm, S21 drops from -7dB to approximately -9dB, meaning the attenuator length... An increase of approximately 1.3mm improves the attenuation value by 2dB. During manufacturing, multiple attenuators of different lengths are designed for direct replacement during use.

[0112] 2. The second method: such as Figure 9 As shown, multiple attenuators can be directly cascaded into the waveguide. The cascade simulation results are available in (see...). Figure 10 This indicates that the single-stage attenuation value is 7dB, and the attenuation values ​​of two cascaded stages can be accumulated. Multiple unit structures can be processed (e.g., a single structure is 2dB). When using them, multiple stages can be directly placed according to the requirements.

[0113] Figure 12 and Figure 11 The images show a comparison of the waveguide electric field with and without an attenuator. As can be seen from the waveguide transmission electric field strength, the signal strength is significantly reduced when the attenuator of this invention is added (the field strength color changes from dark to light). The attenuator structure of this invention has good attenuation performance.

[0114] In summary, compared with existing waveguide attenuator technologies, the terahertz waveguide attenuator of this invention has the advantages of ultra-wideband (275GHz-575GHz, relative bandwidth 70%, traditional structure 40%), miniaturization (directly placed in the system waveguide transmission line, traditional structure requires the fabrication of a separate module), flat attenuation curve (attenuation flatness is ±1dB in the 275GHz-575GHz ultra-wideband range), and adjustable attenuation (the attenuator length can be increased or multiple small attenuation attenuators can be cascaded according to different needs, traditional structure requires additional high-precision robotic arms for control).

[0115] Figure 13 This is a component of the terahertz receiver front-end system, consisting of two stages. The first stage is a frequency multiplier, outputting a signal with a power of 8dBm. The subsequent stage is a mixer, which receives the output signal from the frequency multiplier and drives it. The local oscillator drive of the mixer can withstand a power range of 0-3dBm; excessive power will cause the mixer to burn out. Therefore, an attenuator needs to be cascaded after the frequency multiplier output. Traditional solutions use a single 7dB directional coupler for attenuation, increasing the overall length of the front-end. The overall system volume is only the size of two components. Therefore, the waveguide attenuator of this invention is used, which is directly placed in the connecting waveguide, without occupying any space.

[0116] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention. The above descriptions are merely preferred embodiments of the invention and are not intended to limit the invention. It should be noted that any modifications, equivalent substitutions, and improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A method for implementing an ultra-wideband terahertz waveguide attenuator, characterized in that, Includes the following: Tantalum nitride is used as the waveguide attenuator material; The attenuator includes a supporting base plate, side transition structures, a central rectangular plate, and a top stub. The supporting base plate is located at the bottom of the overall structure, and the rest of the structure is built upon it. The side transition structures are sloped to optimize impedance matching and improve transmission performance. The central rectangular plate is located in the center to enhance signal attenuation efficiency. The top branch increases structural strength and ensures a tight fit with the waveguide wall; Based on the operating frequency band and attenuation requirements, optimize the dimensional parameters of each component, including the length of the support base plate. Width b, height h, the slope angle and length of the side transition structure, and the size of the top branch.

2. The method for implementing an ultra-wideband terahertz waveguide attenuator according to claim 1, characterized in that: The specific dimensions of the supporting base plate are its length. =3.39mm, width b=0.538mm, height h=0.055mm.

3. The method for implementing an ultra-wideband terahertz waveguide attenuator according to claim 2, characterized in that: The dimensions of the intermediate rectangular plate are length and... Consistent, height a=1.016 mm, thickness w2=0.085 mm.

4. A method for implementing an ultra-wideband terahertz waveguide attenuator according to any one of claims 1-3, characterized in that: The thickness of the top branch is w3 = 0.085 mm.

5. The method for implementing an ultra-wideband terahertz waveguide attenuator according to claim 1, characterized in that: The slope length of the side transition structure To meet impedance gradient matching conditions and achieve low reflection and ultra-wideband performance in the 275GHz to 575GHz frequency band, its length must satisfy: ； in, The slope length of the side transition structure; To correspond to the lowest operating frequency GHz guided wave wavelength, The calculation formula is: ； in, m / s is the speed of light For operating frequency, This is the cutoff frequency for the transmission environment.

6. The method for implementing an ultra-wideband terahertz waveguide attenuator according to claim 1, characterized in that: The attenuation value can be adjusted by increasing the length of the support base plate or by cascading multiple attenuators.

7. The method for implementing an ultra-wideband terahertz waveguide attenuator according to claim 6, characterized in that: Attenuation value and support base plate length and material loss factor The following relationship exists between them: ； in, This represents the total attenuation value. This is the unit conversion factor, and its value range is... Used to convert neperts to decibels, to meet... ; To support the length of the base plate along the propagation direction; Propagation attenuation constant The electrical conductivity of tantalum nitride material and operating frequency Together, under the good conductor approximation, the following conditions are met: ； in, The conductivity of tantalum nitride, H / m is the permeability of free space. This refers to the operating frequency.

8. The method for implementing an ultra-wideband terahertz waveguide attenuator according to claim 1, characterized in that: By cascading two or more unit attenuators in a waveguide, the attenuation of a single stage is 7dB, and the total attenuation is accumulated through cascading.

9. An ultra-wideband terahertz waveguide attenuator, characterized in that: This includes the supporting base plate, side transition structure, middle rectangular plate, and top branches; Attenuators are fabricated using tantalum nitride as the material. The supporting base plate is rectangular in shape; The side transition structure is sloped to optimize impedance matching and improve transmission performance; The central rectangular plate is located in the center position to enhance signal attenuation efficiency; The top branch increases structural strength and ensures a tight fit with the waveguide wall.

10. The ultra-wideband terahertz waveguide attenuator according to claim 9, characterized in that: The operating frequency band is 275GHz to 575GHz, with a relative bandwidth of 70% and an attenuation value set at 7dB. The attenuation flatness is controlled within ±1dB in the ultra-wideband range.

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