阅读说明：本技术 一种宽带硅基金属波导矩-圆模式变换器 (Broadband silicon-based metal waveguide rectangular-circular mode converter ) 是由 杨瑾屏 李升� 宋艳汝 杨士成 王彩霞 朱忠博 刘志 于 2021-01-13 设计创作，主要内容包括：本发明涉及一种宽带硅基金属波导矩-圆模式变换器。所述模式变换器采用三段式结构,同时实现矩形TE-(01)模到圆形TE-(11)之间的电磁场波形变换和阻抗匹配。该模式变换器总长度小于四分之一波长,是目前已知长度最小的矩-圆模式变换器结构之一。该模式变换器具有99％能量转化效率的工作带宽为28％,对高次模的抑制度大于115dBc。(The invention relates to a broadband silicon-based metal waveguide rectangular-circular mode converter. The mode converter adopts a three-section structure and simultaneously realizes rectangular TE 01 Die to round TE 11 The electromagnetic field waveform transformation and impedance matching between them. The total length of the mode converter is less than a quarter wavelength, which is one of the presently known rectangular-circular mode converter structures with the smallest length. The mode converter has the working bandwidth of 28 percent of energy conversion efficiency of 99 percent, and the suppression degree of a high-order mode is more than 115 dBc.)

1. The utility model provides a broadband silica-based metal waveguide matrix-circle mode converter which characterized in that comprises input end rectangular waveguide, output end circular waveguide and the converter structure that is located between input end rectangular waveguide and the output end circular waveguide, wherein:

the input end rectangular waveguide and the output end circular waveguide are respectively consistent with the waveguide interface size of an external module or equipment;

the converter structure adopts a three-section structure:

the first section of the converter structure is a section of rectangular waveguide, the width of the rectangular waveguide is equal to the width a of the rectangular waveguide at the input end, and the height H of the rectangular waveguide is equal to the width a of the rectangular waveguide at the input end₁Height b of rectangular waveguide over input end for raising the fundamental mode TE seen from rectangular waveguide at input end₀₁Mode equivalent impedance to realize TE mode of fundamental mode of circular waveguide₁₁Impedance matching between the modes improves the efficiency of mode conversion energy conversion and the working bandwidth;

the third section of the converter structure is a section of truncated circular waveguide I, the diameter of the circular arc of the truncated circular waveguide I is the same as that of the circular waveguide at the output end, and the converter structure is used for reducing the TE of the fundamental mode seen from the circular waveguide at the output end₁₁Mode equivalent impedance and partial realization of a circle TE₁₁Modulus and moment TE₀₁Electromagnetic field wave mode transition between the modes further improves the efficiency and the working bandwidth of mode conversion energy conversion;

the second section of the converter structure is a section of truncated circular waveguide II, the height of the truncated circular waveguide II is equal to that of the rectangular waveguide, and the diameter of the circular arc of the truncated circular waveguide II is equal to the length of the diagonal line of the rectangular waveguide, so that the converter structure is used for realizing circular TE₁₁Modulus and moment TE₀₁The electromagnetic field modes between the modes transition and again extend the operating bandwidth of the converter structure.

2. A wideband silicon-based metal waveguide rectangular-circular mode converter as claimed in claim 1, wherein said output end circular waveguide, said converter structure and said input end rectangular waveguide are implemented by metallization of silicon wafer, or by direct use of conductive sheet material implemented by metallization of various types of metals or various types of metal alloys or surface metallization.

3. A broadband silicon-based metal waveguide rectangular-circular mode converter as claimed in claim 2, wherein the output end circular waveguide, the converter structure and the input end rectangular waveguide are fabricated by using wafer silicon chips with the same thickness, or by selecting and using wafer silicon chips with different thicknesses or stacking wafer silicon chips with a total number of more than 3 according to the actual operating frequency.

4. A wideband silicon-based metal waveguide rectangular-circular mode transducer as claimed in claim 1 wherein each silicon-based thickness of the three-section transducer structure is less than 1/12 wavelengths.

5. The broadband silicon-based metal waveguide rectangular-to-circular mode converter as claimed in claim 1, wherein the heights of the first truncated circular waveguide and the second truncated circular waveguide are determined by electromagnetic field simulation optimization results.

Technical Field

The invention relates to a silicon substrateA metal waveguide mode converter, especially a rectangular waveguide TE₀₁Mode conversion into circular waveguide TE₁₁The circuit structure of the die.

Background

Metal waveguides are one of the indispensable devices for microwave circuitry, especially high power microwave circuits, due to their low transmission loss. The waveguide is conventionally machined, specifically including Computer Numerical Control (CNC) machining and electroforming machining. These machining methods have high accuracy, but the above methods have disadvantages that the machining is difficult, the cost is high, and the direct integration with other parts is difficult when the methods are applied to waveguide parts with complicated structures such as a corrugated horn antenna. In addition, in order to ensure the machining accuracy, the conventional machining method generally adopts a method of machining one by one. This approach is inefficient when array antennas or complex structures such as sum and difference networks need to be fabricated. Silicon etching is an important technology in the semiconductor industry, along with the development of a silicon etching process, the processing of a silicon substrate is not limited to the surface any more, but develops towards the direction of three-dimensional processing, and the deep silicon etching technology capable of realizing high aspect ratio is more widely applied to the preparation process of various Micro Electro Mechanical Systems (MEMS). This process readily achieves machining accuracies better than 1 micron. Therefore, if the deep silicon etching technology is adopted to process complicated structures such as holes, channels, cavities and the like on the silicon substrate and the silicon substrate is stacked into a whole like a sandwich, the silicon-based metal waveguide which meets the application requirements from microwave to working frequency above terahertz can be realized. The implementation method of the stacked metal waveguide structure overcomes many defects of direct machining to a certain extent, and can be conveniently integrated with a waveguide structure or a Monolithic Microwave Integrated Circuit (MMIC).

The basic steps of the process flow required by the silicon-based metal waveguide comprise: 1) coating photoresist on the surface of a bulk silicon wafer; 2) transferring the pattern of the mask plate to a photoresist layer of the bulk silicon wafer through ultraviolet irradiation; 3) the photoresist at the transferred pattern is dissolved and washed away; 4) carrying out potassium hydroxide (KOH) solution or Deep Reactive Ion Etching (DRIE) etching on the processed bulk silicon wafer in the last step according to actual requirements to form functional structures such as a horn, corrugations, waveguides, Braille marks, scribing grooves, positioning grooves and the like; 5) cleaning the etched silicon wafer, and sputtering gold on the surface; 6) bonding the corresponding bulk silicon wafer; 7) scribing the bonded silicon wafer according to the scribing groove; 8) the dicing sidewalls are metallized.

An important field of application for silicon-based metal waveguides is waveguide horn antennas, in particular conical waveguide horn antennas. Most millimeter wave/terahertz modules adopt rectangular waveguides as input/output ports, and especially the input/output ports of various standard test instruments such as a vector network analyzer are also rectangular waveguides. Therefore, the conical waveguide horn antenna must pass through the rectangular-to-circular mode converter to be connected to these modules or devices.

Disclosure of Invention

The purpose of the invention is: a broadband rectangular-circular mode converter for silicon-based metal waveguide applications is provided.

In order to achieve the above object, the present invention provides a broadband silicon-based metal waveguide rectangular-circular mode converter, which is characterized by comprising an input end rectangular waveguide, an output end circular waveguide, and a converter structure located between the input end rectangular waveguide and the output end circular waveguide, wherein:

the input end rectangular waveguide and the output end circular waveguide are respectively consistent with the waveguide interface size of an external module or equipment;

the converter structure adopts a three-section structure:

the first section of the converter structure is a section of rectangular waveguide, the width of the rectangular waveguide is equal to the width a of the rectangular waveguide at the input end, and the height H of the rectangular waveguide is equal to the width a of the rectangular waveguide at the input end₁Height b of rectangular waveguide over input end for raising the fundamental mode TE seen from rectangular waveguide at input end₀₁Mode equivalent impedance to realize TE mode of fundamental mode of circular waveguide₁₁Impedance matching between the modes improves the efficiency of mode conversion energy conversion and the working bandwidth;

the third section of the converter structure is a section of truncated circular waveguide I, the circular arc diameter of the truncated circular waveguide I and the diameter of the output end circular waveguide ISame for reducing the fundamental mode TE seen from the output circular waveguide₁₁Mode equivalent impedance and partial realization of a circle TE₁₁Modulus and moment TE₀₁Electromagnetic field wave mode transition between the modes further improves the efficiency and the working bandwidth of mode conversion energy conversion;

the second section of the converter structure is a section of truncated circular waveguide II, the height of the truncated circular waveguide II is equal to that of the rectangular waveguide, and the diameter of the circular arc of the truncated circular waveguide II is equal to the length of the diagonal line of the rectangular waveguide, so that the converter structure is used for realizing circular TE₁₁Modulus and moment TE₀₁The electromagnetic field modes between the modes transition and again extend the operating bandwidth of the converter structure.

Preferably, the output end circular waveguide, the converter structure and the input end rectangular waveguide are implemented by metallization of a silicon wafer, or are directly implemented by conductive sheet materials implemented by metallization of various metals or various metal alloys or surface metallization.

Preferably, the output end circular waveguide, the converter structure and the input end rectangular waveguide are processed by using wafer silicon wafers with the same thickness, or are formed by selecting and using wafer silicon wafers with different thicknesses or stacking wafer silicon wafers with a total number of more than 3 according to the actual working frequency.

Preferably, each section of silicon-based thickness of the three-section transducer structure is less than 1/12 wavelengths.

Preferably, the heights of the first truncated circular waveguide and the second truncated circular waveguide are determined through electromagnetic field simulation optimization results.

The invention has the following beneficial effects:

1. the rectangular-circular mode converter provided by the invention is manufactured by adopting a silicon-based metal waveguide processing technology and has the advantages of high processing precision, small insertion loss and the like. Meanwhile, the device can be easily seamlessly connected with devices such as a conical horn antenna and the like which are manufactured by the silicon-based metal waveguide process.

2. The silicon-based metal waveguide rectangular-circular mode converter provided by the invention simultaneously realizes gradual change of a physical structure from a rectangular structure to a circular structure and gradual change of an electromagnetic field waveform mode. Thereby avoiding generating excessive high-order modes, and realizing the efficient conversion from the rectangular TE01 mode to the circular TE11 mode and the wide working bandwidth.

3. The moment-circle mode converter provided by the invention adopts a three-section structure, the variable parameters of each section of structure are the height and the length of the structure, and the height and the length respectively have definite corresponding relations with the equivalent impedance and the electrical length of the structure, so that the electromagnetic field equivalent circuit modeling and the simulation optimization are facilitated.

4. The total length of the part of the rectangular-circular mode converter provided by the invention is less than a quarter wavelength, and the rectangular-circular mode converter is one of the rectangular-circular mode converter structures with the minimum length known at present.

5. The typical working bandwidth of the rectangular-circular mode converter provided by the invention after optimization is 28%, the energy conversion efficiency in the working frequency band is more than 99%, and the energy conversion efficiency at the central frequency is more than 99.99936%.

Drawings

FIG. 1 is a graph of the electric field distribution for a rectangular waveguide (left) and a circular waveguide (right);

FIG. 2 is a schematic diagram of a Si-based metal waveguide rectangular-circular mode transducer;

FIGS. 3a and 3b are electromagnetic field simulation results of the SMW-SMW converter, where FIG. 3a is TE₀₁To the circle TE₁₁A mode change result; FIG. 3b is a moment TE₀₁To the circle TM₀₁/TE₂₁And (5) mode conversion results.

Detailed Description

The invention is further illustrated by the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.

The electric field distribution of the rectangular waveguide and the circular waveguide can be as shown in fig. 1, and both have the characteristics of bilateral symmetry, large central strength and sequential reduction of two sides. The similarity of the distribution structure is that the two electromagnetic field modes can directly carry out mode conversion workAnd (4) a foundation. On the other hand, a rectangular waveguide fundamental mode TE₀₁Equivalent impedance of the mode Zr and fundamental mode TE of the circular waveguide₁₁The modulus Zc can be calculated using the following formula:

in the formulas (1) and (2), a and b are respectively the width and height of the standard rectangular waveguide, eta₀Is the impedance of the vacuum wave, λ₀For vacuum wavelength, r is the circular waveguide radius. Since the ratio of the width a to the height b of the standard rectangular waveguide is generally 2:1, it can be known from the equations (1) and (2) that the equivalent impedance between the circular waveguide and the standard rectangular waveguide has significantly different resistance values and dispersion characteristics. Therefore, the broadband moment TE is to be realized with high efficiency₀₁Die to round TE₁₁Mode conversion of the mode must be achieved simultaneously with mode conversion of the electromagnetic field and equivalent impedance matching.

The structure of the silicon-based metal waveguide rectangular-circular mode converter provided by the invention is composed of three parts as shown in figure 2, namely, a rectangular waveguide at an input end, a circular waveguide at an output end and a converter structure between the rectangular waveguide and the circular waveguide. The rectangular waveguide and the circular waveguide are respectively consistent with the waveguide interface size of an external module or equipment. The converter structure adopts a three-section structure:

the first section is a rectangular waveguide with a width equal to the width a of the rectangular waveguide at the input end, but a height H₁The height b of the rectangular waveguide above the input end. Its main function is to raise the fundamental mode TE seen from the input end of the rectangular waveguide₀₁Mode equivalent impedance, primary realization and TE of circular waveguide fundamental mode₁₁And the impedance matching between the modes improves the efficiency and the working bandwidth of the mode conversion energy conversion.

The third section is a truncated circular waveguide, and can be regarded as that the upper end and the lower end of the circular waveguide at the output end are partially flattened. The diameter of the arc and the circle of the output endThe waveguides have the same diameter and the height H₂. The main function of the truncated circular waveguide is to reduce the TE of the fundamental mode seen from the output end of the circular waveguide₁₁Mode equivalent impedance and partial realization of a circle TE₁₁Modulus and moment TE₀₁The modes of the electromagnetic field between the modes transition. Further improving the efficiency and the working bandwidth of the mode conversion energy conversion.

The second section is also a section of truncated circular waveguide, the height of the second section is equal to that of the first section of rectangular waveguide, and the diameter of the circular arc of the second section is equal to the length of the diagonal line of the first section of rectangular waveguide. The main function of the truncated circular waveguide is to realize a circular TE₁₁Modulus and moment TE₀₁The electromagnetic field modes between the modes transition and again extend the operating bandwidth of the converter.

Each section of thickness L of three-section structure₁、L₂、L₃And height H₁、H₂The thickness of the single wafer silicon chip and the electromagnetic field simulation optimization result are jointly determined.

The material of the rectangular-circular mode converter structure provided by the invention is preferably realized by metalizing silicon wafer wafers and processing the silicon wafer wafers with the same thickness, but the rectangular-circular mode converter structure can also be formed by stacking the silicon wafer wafers with different thicknesses or the silicon wafer wafers with the total number of more than 3 according to the actual working frequency. Other conductive sheet materials which are directly made of various metals or metal alloys and are realized by surface metallization of plastics, high polymer materials and the like are also in the protection scope of the patent.

Take a conical corrugated horn antenna rectangular-circular mode converter with a center working frequency of 43GHz as an example. The rectangular waveguide is WR19 straight waveguide, and the width a and the height b of the inner side cross section are 4.8mm and 2.4mm respectively. The radius r of the circular waveguide is determined to be 3.25mm according to the design requirements of the conical corrugated horn antenna, electromagnetic field modeling and simulation optimization are carried out according to electromagnetic field simulation results, and a better result is obtained, wherein the structural size of the circular waveguide is L₁＝₂＝₃0.635mm (actual thickness 0.64mm, taking into account the thickness of the gold-plated layer), H₁＝3.85mmH₂4.25 mm. Its total length is 1.92mm less than (rectangular/circular) quarter wavelength.

The electromagnetic field simulation results can be seen in FIGS. 3a and 3b below, with the mode converter operating at 28% bandwidth with 99% energy conversion efficiency for TM₀₁、TE₂₁The suppression degree of the higher order mode is more than 115 dBc.