Terahertz frequency multiplier with gradient matching structure

Abstract

The invention discloses a terahertz frequency multiplier with a gradient matching structure. The terahertz frequency multiplier comprises an input waveguide for receiving a fundamental wave signal; the funnel-shaped E-plane input probe transition structure couples a fundamental wave signal to the microstrip input low-pass filter, and the design of the funnel-shaped gradual change structure reduces mode distortion at the joint of the waveguide and the microstrip line; the microstrip input low-pass filter filters high-frequency spurious signals and harmonic signals in fundamental wave signals transmitted by the funnel-shaped E-surface probe transition structure; the Schottky diode generates a higher harmonic signal according to the filtered fundamental wave signal; the boss shielding cavity provides electromagnetic shielding, prevents external interference and leakage of filtered fundamental wave signals and required higher harmonic signals, and prevents the conductive adhesive from seeping into the lower cavity. The circular matching microstrip realizes impedance gradient matching by adjusting the radius of a circle so as to achieve smooth transition of higher harmonic signal transmission; the E-plane output probe transition structure couples a higher harmonic signal output by the circular matching microstrip to the output waveguide; the output waveguide outputs a higher harmonic signal.

Description

Technical Field

[0001] The present invention belongs to the technical field of terahertz frequency multipliers, and in particular relates to a terahertz frequency multiplier with a gradient matching structure. Background Art

[0002] In terahertz technology research, the first challenge is to address the terahertz source. A terahertz frequency multiplication source, consisting of a terahertz frequency multiplier, amplifier, and filter, can effectively generate and amplify high-frequency signals, providing the terahertz band signals required for various applications. However, obtaining a high-efficiency, high-power, and high-frequency terahertz source remains a significant challenge in current terahertz technology.

[0003] Currently, the most common approach in solid-state frequency multipliers is to use varactor diodes or Schottky diodes. These diodes, due to their excellent nonlinear characteristics and frequency response, can effectively achieve frequency doubling of fundamental frequency signals. Reactive diodes, such as varactor diodes or fast recovery diodes, are only applicable to a very narrow bandwidth and have narrow-band characteristics. Resistive diodes, mainly Schottky diodes, are purely resistive and are unaffected by frequency, allowing them to operate stably over a wide frequency range. Schottky diodes have low high-frequency multiplication efficiency and are generally used for doubling or tripling. Therefore, one of the urgent issues to be addressed in frequency multipliers based on terahertz Schottky diodes is to improve frequency multiplication efficiency and output power through circuit structure design. The matching structure is the performance key to terahertz frequency multipliers. A good matching design can efficiently couple the fundamental wave energy to the nonlinear junction region of the Schottky diode and achieve efficient transmission of the target harmonics within a wide frequency band. In existing solutions, the input and output matching circuits mostly use multiple sections of high and low impedance microstrip lines. Each level of microstrip line needs to be independently optimized and the electromagnetic coupling effect between adjacent microstrip lines must be considered. Matching is achieved through impedance jumps of multiple sections of microstrip lines.

[0004] However, the steps, corners, and other structures of conventional rectangular conductor microstrip lines introduce parasitic capacitance and inductance, leading to impedance mutations, signal reflections, and deterioration of the standing wave ratio in the overall circuit, which in turn increases energy dissipation and is not conducive to high-power applications. In addition, optimizing high- and low-impedance microstrip lines requires the simultaneous adjustment of multiple parameters such as the microstrip line width, length, and number of step layers, resulting in slow convergence of electromagnetic field simulations and extended design cycles. Summary of the Invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a terahertz frequency multiplier with a gradient matching structure. The technical problem to be solved by the present invention is achieved through the following technical solutions: An embodiment of the present invention provides a terahertz frequency multiplier with a gradient matching structure, the terahertz frequency multiplier comprising: The input waveguide is used to receive the fundamental signal of the terahertz band input from the outside; the funnel-shaped E-surface input probe transition structure is used to couple the fundamental signal output by the input waveguide to the microstrip input low-pass filter to convert the TE10 mode of the waveguide into the quasi-TEM mode of the microstrip, and the funnel-shaped gradient structure design reduces the mode distortion at the connection between the waveguide and the microstrip; the microstrip input low-pass filter is used to filter out the high-frequency stray and harmonic signals in the fundamental signal transmitted by the funnel-shaped E-surface probe transition structure; the Schottky diode is used to generate high-order harmonic signals according to the filtered fundamental signal; the microstrip input low-pass filter is also used to suppress the Schottky diode. The high-order harmonic signal generated by the FET diode is reflected back to the input waveguide; the boss shielding cavity is used to provide electromagnetic shielding to prevent external interference and leakage of the filtered fundamental signal and the required high-order harmonic signal, and to prevent the conductive glue from seeping into the lower cavity and affecting the circuit performance; the circular matching microstrip is used to achieve impedance gradient matching by adjusting the radius of the circle to achieve a smooth transition in transmitting high-order harmonic signals; the E-plane output probe transition structure is used to couple the high-order harmonic signal output by the circular matching microstrip to the output waveguide to convert the quasi-TEM mode of the microstrip into the TE10 mode of the waveguide; the output waveguide is used to output the high-order harmonic signal; wherein, The funnel-shaped E-plane input probe transition structure, the microstrip input low-pass filter, the Schottky diode, the circular matching microstrip, and the E-plane output probe transition structure are in the form of suspended microstrip lines within the boss shielding cavity.

[0006] In one embodiment of the present invention, the input waveguide includes an input standard waveguide and a gradient height reduction waveguide; wherein, The input standard waveguide is used to connect to an external device through a standardized interface flange to receive a fundamental wave signal in the terahertz band input from the outside; The gradually decreasing waveguide height is used to gradually reduce the waveguide height to achieve impedance gradient matching between the waveguide and the microstrip line.

[0007] In one embodiment of the present invention, the microstrip input low-pass filter uses a compact suspended microstrip resonant unit.

[0008] In one embodiment of the present invention, the Schottky diode is a multi-die gallium arsenide Schottky diode or a multi-die gallium nitride Schottky diode.

[0009] In one embodiment of the present invention, the Schottky diode is a series-connected six-die gallium arsenide Schottky diode or a series-connected six-die gallium nitride Schottky diode.

[0010] In one embodiment of the present invention, the radius of the circular matching microstrip is 20 μm to 100 μm.

[0011] In one embodiment of the present invention, the distance between the circular matching microstrip and the Schottky diode is 50 μm to 150 μm.

[0012] In one embodiment of the present invention, the output waveguide includes a gradually-expanded waveguide and an output standard waveguide; wherein, The gradually increasing height waveguide is used to gradually increase the waveguide height to achieve gradual impedance matching between the waveguide and the microstrip line; The output standard waveguide is used to connect to external equipment through a standardized interface flange to output high-order harmonic signals to the outside.

[0013] In one embodiment of the present invention, the operating frequency of the output standard waveguide is twice or three times the operating frequency of the input standard waveguide.

[0014] Beneficial effects of the present invention: The terahertz frequency multiplier with a gradient matching structure proposed in the present invention addresses the problems existing in existing terahertz frequency multipliers and makes improvements based on the circuit structure. Specifically, the input section adopts a funnel-shaped E-surface input probe transition structure to achieve mode conversion and impedance gradient, thereby reducing mode distortion at the connection between the waveguide and the microstrip and achieving efficient transmission and reflection suppression of high-frequency signals. A circular matching microstrip is introduced between the input section and the output section to solve the problems of impedance mutation, increased loss, and long design cycle caused by high- and low-impedance matching. Impedance gradient matching is achieved through arc transition to achieve a smooth transition of the electromagnetic field distribution, optimize the electric field distribution, effectively suppress additional parasitic parameters, reduce reflection and radiation losses, and expand the bandwidth. After the circular matching microstrip is introduced, the expected matching effect can be achieved by simply adjusting the radius of the circular matching microstrip, thereby achieving good impedance matching and enabling rapid design of the frequency multiplier while improving the efficiency and output power of the frequency multiplier. Experiments have shown that the terahertz frequency multiplier designed according to the present invention can achieve an efficiency of 18% and a maximum output power of 36.77mW, verifying that the proposed gradient matching structure can rapidly improve the performance of the terahertz frequency multiplier, and provide new ideas for applications such as sub-terahertz system optimization for 6G communications, and upgrades to high-resolution radar and imaging systems.

[0015] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 1 is a schematic top plan view of a terahertz frequency multiplier with a gradient matching structure provided by an embodiment of the present invention; Figure 2 This is a schematic diagram of the specific structure of the input waveguide and output waveguide in the terahertz frequency multiplier with a gradient matching structure provided by an embodiment of the present invention; Figure 3This is a schematic diagram of the three-dimensional structure of a terahertz frequency multiplier with a gradient matching structure provided by an embodiment of the present invention; Figure 4 This is a schematic diagram of the design process of a terahertz frequency multiplier with a gradient matching structure provided by an embodiment of the present invention; Figure 5 This is a schematic diagram of the E-plane input probe transition structure in a traditional terahertz frequency multiplier; Figure 6 is based on Figure 5 The S-parameter output diagram of port 1 and port 2 of the E-plane input probe transition structure is shown; Figure 7 2. This is a schematic structural diagram of a funnel-shaped E-plane input probe transition structure in a terahertz frequency multiplier with a gradient matching structure provided by an embodiment of the present invention; Figure 8 is based on Figure 7 Schematic diagram of S-parameter output of port 1 and port 2 of the funnel-shaped E-surface input probe transition structure shown Figure 9 Schematic diagram of the efficiency curve of the terahertz frequency multiplier with a gradient matching structure provided by an embodiment of the present invention at an input of 17 dBm; Figure 10 Schematic diagram of the output power curve of the terahertz frequency multiplier with a tapered matching structure provided by an embodiment of the present invention under an input of 24 dBm.

[0017] Description of reference numerals: 1-Input waveguide; 11-Input standard waveguide; 12-Gradually reduced height waveguide; 2-Funnel-shaped E-plane input probe transition structure; 3-Boss shielding cavity; 4-Suspended microstrip line; 5-Microstrip input low-pass filter; 6-Schottky diode; 7-Circular matching microstrip; 8-E-plane output probe transition structure; 9-Output waveguide; 91-Gradually expanded height waveguide; 92-Output standard waveguide. DETAILED DESCRIPTION

[0018] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

[0019] See Figure 1 An embodiment of the present invention provides a terahertz frequency multiplier with a gradient matching structure, the terahertz frequency multiplier comprising: The input waveguide 1 is used to receive the fundamental wave signal of the terahertz band input from the external input; the funnel-shaped E-surface input probe transition structure 2 is used to couple the fundamental wave signal output by the input waveguide 1 to the microstrip input low-pass filter to convert the TE10 mode of the waveguide into the quasi-TEM mode of the microstrip, and the funnel-shaped gradient structure design reduces the mode distortion at the connection between the waveguide and the microstrip, and maximizes the electric field coupling by utilizing the shape and position of the probe to reduce the insertion loss; the microstrip input low-pass filter 5 is used to filter out the high-frequency stray and harmonic signals in the fundamental wave signal transmitted by the funnel-shaped E-surface probe transition structure; the Schottky diode 6 is used to generate high-order harmonic signals according to the filtered fundamental wave signal; the microstrip input The low-pass filter 5 is also used to suppress the high-order harmonic signal generated by the Schottky diode 6 from being reflected back to the input waveguide 1; the boss shielding cavity 3 is used to provide electromagnetic shielding to prevent external interference and leakage of the filtered fundamental signal and the required high-order harmonic signal, and to prevent the conductive glue from seeping into the lower cavity and affecting the circuit performance; the circular matching microstrip 7 is used to achieve impedance gradient matching by adjusting the radius of the circle to achieve a smooth transition in transmitting high-order harmonic signals; the E-plane output probe transition structure 8 is used to couple the high-order harmonic signal output by the circular matching microstrip 7 to the output waveguide to convert the quasi-TEM mode of the microstrip into the TE10 mode of the waveguide; the output waveguide 9 is used to output the high-order harmonic signal; wherein, The funnel-shaped E-plane input probe transition structure 2 , the microstrip input low-pass filter 5 , the Schottky diode 6 , the circular matching microstrip 7 , and the E-plane output probe transition structure 8 are in the form of a suspended microstrip line 4 in the boss shielding cavity 3 .

[0020] See Figure 2 In this embodiment of the present invention, the input waveguide 1 includes an input standard waveguide and a gradually decreasing waveguide. The input standard waveguide 11 is used to connect to an external device via a standardized interface flange to receive an externally input terahertz band fundamental wave signal, reducing reflection loss. The gradually decreasing waveguide 12 is used to gradually reduce the waveguide height to achieve gradually changing impedance matching between the waveguide and the microstrip line, reduce signal reflections caused by sudden size changes, and optimize the standing wave ratio within the bandwidth. The output waveguide 9 includes a gradually increasing waveguide height and an output standard waveguide. The gradually increasing waveguide height 91 is used to gradually increase the waveguide height to achieve gradually changing impedance matching between the waveguide and the microstrip line, ensuring low-loss signal transmission to the external system. The output standard waveguide 92 is used to connect to an external device via a standardized interface flange to output higher-harmonic signals to the outside.

[0021] In the embodiment of the present invention, the microstrip input low-pass filter 5 uses a compact suspended microstrip resonant unit.

[0022] In the embodiment of the present invention, the Schottky diode 6 is a multi-die gallium arsenide (GaAs) Schottky diode or a multi-die gallium nitride (GaN) Schottky diode. More preferably, the Schottky diode 6 is a series-connected six-die gallium arsenide Schottky diode or a series-connected six-die gallium nitride Schottky diode.

[0023] In the embodiment of the present invention, the distance between the circular matching microstrip 7 and the Schottky diode 6 is 50 μm to 150 μm.

[0024] In the embodiment of the present invention, the operating frequency of the output standard waveguide 92 is twice or three times the operating frequency of the input standard waveguide 11 .

[0025] See Figure 3 The terahertz frequency multiplier with a gradient matching structure proposed in this invention can be more intuitively understood from a three-dimensional perspective. The input waveguide 1, the funnel-shaped E-plane input probe transition structure 2, and the microstrip input low-pass filter 5 constitute the input section. The E-plane output probe transition structure 8 and the output waveguide 9 constitute the output section. The circular matching microstrip 7 connects the input and output sections.

[0026] See Figure 4 The embodiment of the present invention provides a method for designing a terahertz frequency multiplier with a gradient matching structure, which is specifically as follows: The dimensions of the input standard waveguide 11 and the output standard waveguide 92 are selected according to the operating frequency band, and the corresponding gradually decreasing waveguide 12 and gradually increasing waveguide 91 are selected so that the operating frequency of the output standard waveguide 92 is twice or three times the operating frequency of the input standard waveguide 11; and suitable multi-tube gallium arsenide (GaAs) or gallium nitride (GaN) Schottky diodes are selected, such as six-tube gallium arsenide (GaAs) or gallium nitride (GaN) Schottky diodes connected in series, to improve power capacity and voltage resistance.

[0027] Modeling the boss shielding cavity 3 and the suspended microstrip line 4. All other microstrip structures except the waveguide are arranged on the dielectric substrate of the suspended microstrip line 4. The Schottky diode 6 is inverted on the suspended microstrip line 4, and both sides are connected to the cavity ground with conductive glue.

[0028] The input-side E-plane input probe transition structure is designed with a funnel-shaped gradient to improve return loss characteristics. The output-side E-plane output probe transition structure 8 also consists of a probe microstrip line. Simply optimizing the width of this microstrip line enables excellent high-harmonic extraction and power transmission. The probe microstrip line is inserted vertically from the center of the waveguide broadside. The distance between the probe and the waveguide short-circuit surface is 1 / 4 of the wavelength corresponding to the waveguide cutoff frequency to achieve good impedance matching.

[0029] The microstrip input low-pass filter 5 uses a compact suspended microstrip resonant unit to pass the fundamental signal while suppressing the reverse leakage of high-order harmonics generated by the Schottky diode 6 to the input waveguide 1.

[0030] By modeling a circular matching microstrip 7 and adjusting the radius R of the circular matching microstrip 7, efficient and fast matching can be achieved. As can be seen from the process, the present invention only needs to determine the center position of the circular matching microstrip 7 in HFSS (High Frequency Structure Simulator) and then optimize the value of the radius R. Figure 4 The process indicated by the dashed line is the traditional high-low impedance matching process. As can be seen from the flowchart: the high-low impedance matching design process is relatively cumbersome and requires joint simulation of ADS (Advanced Design System) and HFSS. After multiple iterations and multiple parameter optimizations, the matching target can be achieved. This results in slow convergence of electromagnetic field simulation and a long design cycle. If the high-low impedance microstrip line has a stepped structure, the stepped structure will force the current line to bend at the junction of wide and narrow, resulting in a local increase in current density and reduced circuit reliability. Compared with the traditional high-low impedance matching method, the design method of the present invention significantly reduces the number of iterations in the design process and shortens the length of the microstrip matching circuit. At the same time, it effectively suppresses harmonic reflections and parasitic losses, improves energy conversion efficiency and achieves high power output.

[0031] The inventors proposed the above-mentioned terahertz frequency multiplier with a gradient matching structure because the inventors found that the matching microstrip circuit design connecting the input and output sections of the terahertz frequency multiplier in a large number of current documents and patent designs mostly relies on adjusting the ideal microstrip line in ADS to achieve rapid optimization. However, since there is no accurate model of the boss shielding cavity 3 and the suspended microstrip line 4 in ADS, the ideal microstrip line model in ADS has no shielding cavity and does not contain bosses. Therefore, when using traditional high-low impedance transformation for matching, it is only possible to set multiple sections of rectangular microstrip lines in ADS to optimize the length and width for preliminary parameter adjustment, and then model the corresponding rectangular microstrip in HFSS for further parameter scanning optimization. The optimization process is cumbersome and it is difficult to achieve the design goal of low loss. Therefore, the present invention proposes a terahertz frequency multiplier with a gradient matching structure, which takes into account the adverse effects of circuit reliability and microstrip structure mutations on electromagnetic field strength, mode and energy transmission. A funnel-shaped E-surface input probe transition structure 2 is used at the input end to reduce the mode distortion at the connection between the waveguide and the microstrip, thereby achieving efficient transmission and reflection suppression of high-frequency signals. More importantly, a new circular microstrip line is introduced, and the radius of the circular matching microstrip is 20μm~100μm. After determining the position of the circular matching microstrip line 7 relative to the center of the Schottky diode 6, the distance between the circular matching microstrip 7 and the Schottky diode 6 is ensured to be 50μm~150μm. This is because a distance that is too short is not conducive to processing and assembly, and a distance that is too long is not conducive to reducing losses. Since the circular matching microstrip 7 structure only has one variable, the radius R, it can be directly optimized in HFSS to achieve fast and efficient matching. The circular matching structure adopted achieves optimization of the electromagnetic field distribution through smooth impedance transition, reducing reflection loss. Experiments have also proved the feasibility of this solution.

[0032] Through the above design, it can be ensured that the designed terahertz frequency multiplier meets all index requirements.

[0033] In order to verify the effectiveness of the terahertz frequency multiplier with a gradient matching structure provided by the embodiment of the present invention, the following experiments were conducted for verification.

[0034] Figure 5 It is the E-plane input probe transition structure in the traditional terahertz frequency multiplier. Figure 6 To adopt Figure 5 The structure shown is the return loss S(1,1) curve at port 1 and the transmission coefficient S(2,1) curve at port 2. Figure 6The horizontal axis represents the frequency range of the terahertz frequency multiplier in GHz, and the vertical axis represents the return loss S(1,1) at port 1 and the transmission coefficient S(2,1) at port 2 in dB. The return loss S(1,1) is greater than -7.14dB in the range of 75GHz to 110GHz, indicating serious impedance mismatch. The transmission coefficient S(2,1) is between -2.25dB and -0.95dB, indicating significant circuit loss. While keeping other structures and parameters unchanged, the Figure 7 The funnel-shaped E-surface input probe transition structure 2 shown in FIG. 1 corresponds to the return loss S(1,1) curve at port 1 and the transmission coefficient S(2,1) curve at port 2. Figure 8 As shown, Figure 8 The horizontal axis represents the frequency range of the terahertz frequency multiplier in GHz, and the vertical axis represents the return loss S(1,1) at port 1 and the transmission coefficient S(2,1) at port 2 in dB. The return loss S(1,1) is less than -10dB, and the transmission coefficient S(2,1) is greater than -0.45dB in this frequency band. The input port is well matched, energy reflection is small, and the RF signal can be well transmitted. Figure 5 and Figure 7 The linear parameter sweep setting setup1 is used for both, and the frequency is swept from 60 GHz to 120 GHz in steps of 0.5 GHz to obtain the S-parameter curves of port 1 and port 2 respectively.

[0035] Furthermore, a 170GHz frequency multiplier based on a six-die GaAs Schottky diode was designed. Figure 9 This is the efficiency curve of the terahertz frequency multiplier at 17dBm input. Figure 9 The horizontal axis represents the frequency range of the terahertz multiplier in GHz, and the vertical axis represents the efficiency at 17dBm input in %. Figure 10 This is the output power curve of the terahertz frequency multiplier at 24dBm input. Figure 10 The horizontal axis represents the frequency range of the terahertz multiplier in GHz, and the vertical axis represents the output power at 24dBm input in mW. Figure 9 It can be seen that the terahertz frequency multiplier proposed in the present invention can achieve a maximum efficiency of 18% at an input of 17dBm, and the efficiency is greater than 5% within a bandwidth exceeding 62GHz. Figure 10 It can be seen that when the terahertz frequency multiplier proposed in the present invention is used and the input power is increased to 24 dBm, the maximum output power can reach 36.77 mW.

[0036] In summary, the terahertz frequency multiplier with a gradient matching structure proposed in the embodiment of the present invention addresses the problems existing in the existing terahertz frequency multiplier and makes improvements based on the circuit structure. Specifically, the input section adopts a funnel-shaped E-surface input probe transition structure to achieve mode conversion and impedance gradient, thereby reducing the mode distortion at the connection between the waveguide and the microstrip, and achieving efficient transmission and reflection suppression of high-frequency signals. A circular matching microstrip is introduced between the input section and the output section to solve the problems of impedance mutation, increased loss, and long design cycle caused by high and low impedance matching. Impedance gradient matching is achieved through arc transition to achieve a smooth transition of the electromagnetic field distribution, optimize the electric field distribution, effectively suppress additional parasitic parameters, reduce reflection and radiation losses, and expand the bandwidth. After the circular matching microstrip is introduced, it is only necessary to adjust the radius of the circular matching microstrip to achieve the expected matching effect, realize good impedance matching, and realize rapid design of the frequency multiplier while improving the efficiency and output power of the frequency multiplier. Experiments have shown that the terahertz frequency multiplier designed according to the present invention can achieve an efficiency of 18% and a maximum output power of 36.77mW, verifying that the proposed gradient matching structure can rapidly improve the performance of the terahertz frequency multiplier, and provide new ideas for applications such as sub-terahertz system optimization for 6G communications, and upgrades to high-resolution radar and imaging systems.

[0037] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0038] Although the present invention is described herein in conjunction with various embodiments, those skilled in the art may understand and implement other variations of the disclosed embodiments by reviewing the specification and accompanying drawings in the process of implementing the claimed invention. In the specification, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude multiple components or steps. The fact that certain measures are described in different embodiments does not mean that these measures cannot be combined to produce good results.

[0039] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A terahertz frequency multiplier with a gradient matching structure, characterized in that: The terahertz frequency multiplier comprises: The input waveguide is used to receive the fundamental signal of the terahertz band input from the outside; the funnel-shaped E-surface input probe transition structure is used to couple the fundamental signal output by the input waveguide to the microstrip input low-pass filter to convert the TE10 mode of the waveguide into the quasi-TEM mode of the microstrip, and the funnel-shaped gradient structure design reduces the mode distortion at the connection between the waveguide and the microstrip; the microstrip input low-pass filter is used to filter out the high-frequency stray and harmonic signals in the fundamental signal transmitted by the funnel-shaped E-surface probe transition structure; the Schottky diode is used to generate high-order harmonic signals according to the filtered fundamental signal; the microstrip input low-pass filter is also used to suppress the Schottky diode. The high-order harmonic signal generated by the FET diode is reflected back to the input waveguide; the boss shielding cavity is used to provide electromagnetic shielding to prevent external interference and leakage of the filtered fundamental signal and the required high-order harmonic signal, and to prevent the conductive glue from seeping into the lower cavity and affecting the circuit performance; the circular matching microstrip is used to achieve impedance gradient matching by adjusting the radius of the circle to achieve a smooth transition in transmitting high-order harmonic signals; the E-plane output probe transition structure is used to couple the high-order harmonic signal output by the circular matching microstrip to the output waveguide to convert the quasi-TEM mode of the microstrip into the TE10 mode of the waveguide; the output waveguide is used to output the high-order harmonic signal; wherein, The funnel-shaped E-plane input probe transition structure, the microstrip input low-pass filter, the Schottky diode, the circular matching microstrip, and the E-plane output probe transition structure are in the form of suspended microstrip lines within the boss shielding cavity.

2. The terahertz frequency multiplier with a gradient matching structure according to claim 1, characterized in that: The input waveguide includes an input standard waveguide and a gradually decreasing height waveguide; wherein, The input standard waveguide is used to connect to an external device through a standardized interface flange to receive a fundamental wave signal in the terahertz band input from the outside; The gradually decreasing waveguide height is used to gradually reduce the waveguide height to achieve impedance gradient matching between the waveguide and the microstrip line.

3. The terahertz frequency multiplier with a gradient matching structure according to claim 1, characterized in that: The microstrip input low-pass filter uses a compact suspended microstrip resonant unit.

4. The terahertz frequency multiplier with a gradient matching structure according to claim 1, characterized in that: The Schottky diode is a multi-die gallium arsenide Schottky diode or a multi-die gallium nitride Schottky diode.

5. The terahertz frequency multiplier with a gradient matching structure according to claim 4, characterized in that: The Schottky diodes are six-core gallium arsenide Schottky diodes connected in series or six-core gallium nitride Schottky diodes connected in series.

6. The terahertz frequency multiplier with a gradient matching structure according to claim 1, characterized in that: The radius of the circular matching microstrip is 20 μm to 100 μm.

7. The terahertz frequency multiplier with a gradient matching structure according to claim 1, characterized in that: The distance between the circular matching microstrip and the Schottky diode is 50 μm to 150 μm.

8. The terahertz frequency multiplier with a gradient matching structure according to claim 2, characterized in that: The output waveguide includes a gradually expanded waveguide and an output standard waveguide; wherein, The gradually increasing height waveguide is used to gradually increase the waveguide height to achieve gradual impedance matching between the waveguide and the microstrip line; The output standard waveguide is used to connect to external equipment through a standardized interface flange to output high-order harmonic signals to the outside.

9. The terahertz frequency multiplier with a gradient matching structure according to claim 8, characterized in that: The operating frequency of the output standard waveguide is twice or three times the operating frequency of the input standard waveguide.

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