Compact 90-degree over-mode waveguide TE01-TM11 mode converter

Abstract

The invention discloses a compact 90-degree over-mode waveguide TE01-TM11 mode converter, and belongs to the technical field of microwaves and millimeter waves. The mode converter comprises a first transition section, an over-mode corrugated groove turning section, an over-mode smooth mode conversion section and a second transition section which are connected in sequence, and the joints of inner cavities of the sections are in smooth transition; the over-mode corrugated groove turning section is formed by periodically arranging a plurality of circular ring grooves on the inner wall of the smooth over-mode circular waveguide, and the turning angle is the turning radius R; and the turning angle of the over-mode smooth mode conversion section is the turning radius R. While 90-degree turning is realized, the working mode is converted from the TE01 mode to the TM11 mode, and meanwhile, the waveguide mode converter has the functions of a waveguide mode converter and an elbow, so that the use of transmission devices is reduced, and the efficiency of the whole system is improved.

Description

Technical Field

[0001] This invention belongs to the field of microwave and millimeter-wave technology, specifically relating to a high-power millimeter-wave overmode waveguide bend structure TE 01 -TM 11 Mode converter. Background Technology

[0002] With the rapid development of technologies such as electronic warfare, microwave weapons, and radar communications, high-power millimeter-wave technology has gradually become a research hotspot in the fields of military defense and large scientific facilities. Gyrotron traveling-wave tubes (TWTs), due to their advantages of high peak power, high average power, and wide operating bandwidth, are the most representative high-power millimeter-wave amplification sources, and are widely used in long-range high-resolution radar, deep-space communications, and electronic warfare. Currently, TWTs can achieve power output levels in the hundreds of kilowatts within 10% of their bandwidth. TE 01 The TE mode, characterized by its angularly uniform, symmetrical field distribution concentrated in a ring-shaped region, facilitates interaction between the electron beam and the field, making it a commonly used operating mode for cyclotron traveling wave tubes. However, TE... 01 The radiation field of the mode is hollow and has no polarization characteristics. It cannot be directly used as the radiation mode of the antenna. It usually needs to be converted into a Gaussian or Gaussian-like mode with linear polarization characteristics by the transmission system before it can be fed into the antenna system.

[0003] There are two common waveguide mode conversion methods in transmission systems: (1) TE 01 Mode (Gyrotron Traveling Wave Tube Output Mode) - TE 11 Mode (Intermediate Mode) - HE 11 (2) TE (Gaussian-like pattern) 01 Mode (Gyrotron Traveling Wave Tube Output Mode) -TM 11 Mode (Intermediate Mode) - HE 11 Mode (Gaussian-like mode). The first mode transform sequence achieves TE through serpentine periodic perturbation along the waveguide axis. 01 To TE 11 The mode switching has the advantage of easily making the input and output ports coaxial, but the disadvantage is that TE... 01 -TE 11 Mode conversion is inefficient with a single cycle, requiring multiple cycles to achieve high-efficiency conversion, resulting in a long structure and narrow bandwidth. The second mode conversion method uses a smooth circular waveguide with a curved axis to convert the TE... 01 Schema to TM 11 The pattern is then implemented using a gradient corrugated groove waveguide to transmit the TM signal. 11 Schema conversion to HE 11 Mode. TE in a circular waveguide 01 Pattern and TM 11The modes are a pair of degenerate modes. According to mode coupling theory, these two modes undergo a full conversion when the waveguide axis bends. The full conversion angle is related to the waveguide aperture and the operating frequency. This scheme has a significant bandwidth advantage, but in the millimeter-wave band, when using over-mode circular waveguide transmission, TE... 01 Model to TM 11 The angle at which the mode undergoes a full conversion will be an acute angle. The existence of irregular angles does not meet the design requirements for a compact system and the structural requirements for simple installation, causing great inconvenience to practical use. The literature “Xiaoyi Liao; Zewei Wu; Yu Zhang; Minxing Wang; Youlei Pu; Wei Jiang; Yong Luo, “A90-degree Oversized Broadband TE01-to-TM11 Mode Converter for High-Power Transmission Line”, IEEE Transactions on Microwave Theory and Techniques, 2019, 67(12):4692-4699” uses an elliptical waveguide structure embedded in the waveguide turning structure to reverse the TE 01 Pattern and TM 11 The relative phase of the modes controls the angle of mode switching, achieving a 90-degree TE transition between input and output. 01 -TM 11 Mode converter. However, due to the insertion of the elliptical waveguide phase reversal structure, the mode converter is relatively large, and the phase reversal bandwidth of the elliptical waveguide is limited, thus restricting the operating bandwidth of the entire scheme. Summary of the Invention

[0004] Regarding the existing TE in the background technology 01 -TM 11 Mode conversion techniques suffer from limitations such as limited operating bandwidth and irregular output angles. This invention provides a compact, broadband, and efficient 90-degree-of-mode waveguide TE. 01 -TM 11 Mode converter, in converting TE 01 Efficiently converting MOSFETs to TMs 11 While maintaining the same mode, it can also make a 90-degree turn, which facilitates the realization of a compact, high-power millimeter-wave system.

[0005] The technical solution of this invention is:

[0006] A compact 90-degree overmode waveguide TE 01 -TM 11The mode converter includes a first transition section, a through-mode corrugated groove turning section, a through-mode smooth mode conversion section, and a second transition section connected in sequence, with smooth transitions at the internal cavity connections of each section.

[0007] The first transition section is used to transfer the TE of the preceding system. 01 The pattern is transmitted to the turning section of the over-molded corrugated groove;

[0008] The overmode corrugated groove turning section is a section of overmode corrugated groove waveguide with a bent axis, used to transfer the input TE 01 The mode is transmitted to the overmode smoothing mode conversion section; the overmode corrugated waveguide is composed of several annular grooves periodically arranged on the inner wall of the smooth overmode circular waveguide, and its turning angle is... The turning radius is R;

[0009] The overmode smoothing transition segment is a section of smooth overmode circular waveguide with a curved axis, used to transform the TE mode. 01 Mode conversion to TM 11 The mode is then transmitted to the second transition section; the turning radius of the overmode smoothing mode conversion section is the same as that of the overmode corrugated groove waveguide, and the turning angle is...

[0010]

[0011] Where λ0 is the free-space wavelength corresponding to the center frequency, and a is the waveguide radius, and

[0012] The second transition section is used to transfer TM 11 The mode is transmitted to the subsequent system.

[0013] Preferably, in the turning section of the corrugated groove, the period (center distance between adjacent grooves) of the annular groove is λ0 / 10 to λ0 / 5, and the duty cycle is 7:3. Since there are slight dimensional differences in the width of the annular groove at the inner and outer diameters of the turning section of the corrugated groove, in actual processing, to reduce processing difficulty and save costs, the annular groove is processed to have a uniform width.

[0014] Preferably, the depth of the annular groove is λ0 / 6 to λ0 / 4.

[0015] Preferably, the first transition section is a smooth overmode circular waveguide with a gradually decreasing aperture, the input aperture being the same as the output aperture of the preceding system, and the output aperture being the same as the aperture of the overmode corrugated groove turning section.

[0016] Preferably, the second transition section is a smooth overmode circular waveguide with a gradually increasing aperture, the input aperture being the same as that of the smooth mode conversion section, and the output aperture being the same as that of the subsequent system.

[0017] Preferably, in the mode converter, each segment is divided into two symmetrical parts along the electromagnetic wave propagation direction and processed separately, and adjacent segments are connected by waveguide flanges; in order to ensure installation accuracy, pins are provided at the waveguide flange opening.

[0018] Preferably, the mode converter further includes a support frame; the support frame is used to support and fix each section of the structure to maintain the stability of the overall structure.

[0019] Preferably, the mode converter is made of stainless steel, copper, or aluminum.

[0020] The working principle of the mode converter is as follows:

[0021] When electromagnetic waves travel at TE 01 After the mode enters the first transition section from the pre-stage system, it sequentially passes through the over-mode corrugated groove turning section, the over-mode smoothing mode conversion section, and the second transition section, where the mode state changes. Finally, the TM is output externally through the second transition section. 11 The model, specifically as follows:

[0022] In the first transition phase, the waveguide inner diameter decreases linearly and slowly without bending of the axis, therefore the mode distribution remains unchanged and remains at TE. 01 Mode. After the electromagnetic wave enters the turning section of the overmode corrugated groove, due to the periodically distributed annular groove structure inside the waveguide, TE 01 Pattern and TM 11 Mode degeneracy is de-optimized, and mode coupling strength is greatly reduced. TE 01 The majority of power in this mode will not be coupled to the TM. 11 Modes and other parasitic modes to achieve TE 01 High-purity transmission of the mode. Furthermore, due to TE... 01 The mode is also the intrinsic mode of the corrugated groove bend section; therefore, no transition structure is needed between the circular waveguide of the first transition section and the overmode corrugated groove bend section, and they can be directly connected. The TE output of the overmode corrugated groove bend section... 01 After the mode enters the overmode smoothing mode transition segment, due to the bending of the circular waveguide axis, TE 01 The model is gradually shifting towards TM 11 Mode coupling is implemented, and complete mode conversion is achieved at the output of the overmode smoothing mode conversion section. Afterwards, the output is sent to the subsequent system via a second transition section.

[0023] The present invention has the following advantages:

[0024] 1. The over-mode waveguide elbow of the present invention can achieve a 90-degree turn while changing the working mode from TE. 01 Convert to TM 11 This mode combines the functions of a waveguide mode converter and an elbow, which helps reduce the use of transmission devices and improve the efficiency of the entire system.

[0025] 2. The mode of this invention achieves efficient conversion over a wide frequency band.

[0026] 3. The structure is simple and compact, and the whole is symmetrical, which makes it easy to process and assemble. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0028] Figure 2 This is a schematic diagram of the turning section of the corrugated groove of the present invention;

[0029] Figure 3 This is a schematic diagram of the periodic distribution of the embedded teeth inside the overmolded corrugated groove of the present invention;

[0030] Figure 4 TE is an embodiment of the present invention. 01 -TM 11 The conversion efficiency of the mode converter;

[0031] Figure 5 TE is an embodiment of the present invention. 01 -TM 11 The distribution of parasitic modes at the output port and the reflection at the input port of the mode converter.

[0032] Explanation of reference numerals in the attached diagram: 1 is the input port; 2 is the first transition section; 3 is the bend section of the mold corrugated groove; 4 is the transition section of the mold smooth mode; 5 is the second transition section; 6 is the support frame; 7 is the pin; 8 is the flange; and 9 is the output port. Detailed Implementation

[0033] 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 this embodiment.

[0034] With a 90-degree turn TE 01 -TM 11 As an example, a mode converter is used. Figure 1 As shown, the mode converter consists of a first transition section, a mode-passing corrugated groove turning section, a mode-passing smooth mode conversion section, a second transition section, and a support structure. The internal connections of each section are smoothly transitioned. The electromagnetic wave sequentially passes through the first transition section, the mode-passing corrugated groove turning section, the mode-passing smooth mode conversion section, and the second mode conversion section. After passing through a 90-degree curved structure, the input TE wave is converted... 01 Mode conversion to TM 11 model.

[0035] The first transition section is used to transfer the TE of the preceding system. 01 The pattern is transmitted to the turning section of the over-mode corrugated groove.

[0036] The overmode corrugated groove turning section is a section of overmode corrugated groove waveguide with a bent axis, used to transfer the input TE 01 The mode is transmitted to the overmode smoothing mode conversion section; the overmode corrugated waveguide is composed of several annular grooves periodically arranged on the inner wall of the smooth overmode circular waveguide, and its turning angle is... The turning radius is R.

[0037] The overmode smoothing transition segment is a section of smooth overmode circular waveguide with a curved axis, used to transform the TE mode. 01 Mode conversion to TM 11 The mode is then transmitted to the second transition section; the turning radius of the overmode smoothing mode conversion section is the same as that of the overmode corrugated groove waveguide, and the turning angle is...

[0038]

[0039] Where λ0 is the free-space wavelength corresponding to the center frequency, and a is the waveguide radius, and

[0040] The second transition section is used to transfer TM 11 The mode is transmitted to the subsequent system.

[0041] The support frame is used to support and fix each section of the structure to maintain the stability of the overall structure. At the same time, for actual processing, each section is divided into two symmetrical parts along the electromagnetic wave propagation direction and processed separately. Adjacent sections are connected by waveguide flanges. To ensure installation accuracy, pins are provided at the opening of the waveguide flange.

[0042] The simulation structure parameters and simulation results for a specific embodiment of the Ka band are given below:

[0043] The center frequency f of the Ka band is set to 34 GHz, and the corresponding wavelength λ is 8.8 mm.

[0044] In the design, the structure of the overmode smoothing transition section is first determined. The waveguide radius r2 of the overmode smoothing transition section is 12mm, and the turning radius R is 500mm. According to formula (1), the turning angle is...

[0045] like Figure 2 As shown, the waveguide radius of the turning section of the over-die corrugated groove is set to 12mm, the turning radius R is 500mm, and the turning angle is... The period p of the annular groove is 1.5 mm, and each corrugation cycle is converted into an angle of... The total number of annular grooves is The corrugated duty cycle is 7 (air):3 (metal); the depth h of the annular groove is one-sixth of the wavelength, i.e., 1.5mm; since the width variation of the annular groove at the inner and outer diameters of the corrugated groove turning section is less than 0.05mm, in actual processing, in order to reduce processing difficulty and save costs, the annular groove is processed to have a uniform width.

[0046] The first transition section and the second transition section are structurally symmetrical. The input radius of the first transition section and the output radius of the second transition section are r. 1＝ 16mm, the output radius of the first transition section and the input radius of the second transition section are r. 2＝ 12mm, both with a length of L1 = 100mm.

[0047] Figure 4 TE is an embodiment of the present invention. 01 -TM 11 The transmission characteristics of the mode converter are as follows: Efficiency greater than 95% with a relative bandwidth of 27% in the 29GHz-38GHz range, reaching maximum efficiency of 98% at 31.5GHz.

[0048] Figure 5 TE is an embodiment of the present invention. 01 -TM 11 The distribution of parasitic modes at the output port and the reflection at the input port of the mode converter. The main parasitic mode is TE. 01 The mode content is less than 3% in the 29GHz-38GHz range, and the TE at the output port is visible. 01 The mode content is extremely small, TE 01 Efficiently convert patterns into TM 11 Mode. Other parasitic mode content is less than 1%. Input port TE in the 28GHz-38GHz range. 01 The reflection coefficients of all modes are below -30dB, indicating that the designed mode converter has good low reflection characteristics over a wide bandwidth.

Claims

1. A compact 90-degree overmode waveguide TE 01 -TM 11 Mode converter, characterized in that, It includes a first transition section, a corrugated groove turning section, a smooth mode conversion section, and a second transition section connected in sequence, with smooth transitions at the internal cavity connections of each section. The first transition section is used to transfer the TE of the preceding system. 01 The pattern is transmitted to the turning section of the over-molded corrugated groove; The overmode corrugated groove turning section is a section of overmode corrugated groove waveguide with a bent axis, used to transfer the input TE 01 The mode is transmitted to the overmode smoothing mode conversion section; the overmode corrugated waveguide is composed of several annular grooves periodically arranged on the inner wall of the smooth overmode circular waveguide, and its turning angle is... The turning radius is R; The overmode smoothing transition segment is a section of smooth overmode circular waveguide with a curved axis, used to transform the TE mode. 01 Mode conversion to TM 11 The mode is then transmitted to the second transition section; the turning radius of the overmode smoothing mode conversion section is the same as that of the overmode corrugated groove waveguide, and the turning angle is... Where λ0 is the free-space wavelength corresponding to the center frequency, and a is the waveguide radius, and The second transition section is used to transfer TM 11 The mode is transmitted to the subsequent system.

2. A compact 90-degree overmode waveguide TE as described in claim 1 01 -TM 11 Mode converter, characterized in that, In the turning section of the overmolded corrugated groove, the period p of the annular groove takes the value of λ0 / 10 to λ0 / 5, and the duty cycle is 7:

3.

3. A compact 90-degree overmode waveguide TE as described in claim 2 01 -TM 11 Mode converter, characterized in that, The depth of the annular groove is λ0 / 6 to λ0 / 4.

4. A compact 90-degree overmode waveguide TE as described in claim 2 or 3 01 -TM 11 Mode converter, characterized in that, The first transition section is a smooth overmode circular waveguide with a gradually decreasing aperture. The input aperture is the same as the output aperture of the preceding system, and the output aperture is the same as the aperture of the overmode corrugated groove turning section.

5. A compact 90-degree overmode waveguide TE as described in claim 4 01 -TM 11 Mode converter, characterized in that, The second transition section is a smooth overmode circular waveguide with a gradually increasing aperture. The input aperture is the same as that of the smooth mode conversion section, and the output aperture is the same as that of the input aperture of the subsequent system.

6. A compact 90-degree overmode waveguide TE as described in claim 5 01 -TM 11 Mode converter, characterized in that, In the mode converter, each segment is divided into two symmetrical parts along the electromagnetic wave propagation direction and processed separately. Adjacent segments are connected by waveguide flanges. To ensure installation accuracy, pins are provided at the waveguide flange opening.

7. A compact 90-degree overmode waveguide TE as described in claim 6 01 -TM 11 Mode converter, characterized in that, The mode converter also includes a support frame; the support frame is used to support and fix each section of the structure to maintain the stability of the overall structure.

8. A compact 90-degree overmode waveguide TE as described in claim 7 01 -TM 11 Mode converter, characterized in that, The mode converter is made of stainless steel, copper, or aluminum.

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