阅读说明：本技术 一种圆极化同轴内嵌圆波导模式激励器 (Circular polarization coaxial embedded circular waveguide mode exciter ) 是由 李�浩 欧美玲 李殿亮 王克强 李天明 周翼鸿 汪海洋 胡标 于 2019-11-19 设计创作，主要内容包括：本发明公开了一种圆极化同轴内嵌圆波导模式激励器,属于模式激励器领域。该模式激励器为内导体为圆波导形式的同轴波导结构,包括依次连接的截止段、谐振段和辐射段,所述谐振段中,内导体波导壁上沿轴向设置有周期性螺旋分布的角向和轴向都满足布拉格谐振条件的耦合缝隙或者耦合孔阵列。本发明模式激励器具有结构简单、矢量模式纯度高、耦合效率大、高纯度带宽和杂模数目少的优点。(The invention discloses a circularly polarized coaxial embedded circular waveguide mode exciter, and belongs to the field of mode exciters. The mode exciter is a coaxial waveguide structure with an inner conductor in a circular waveguide form, and comprises a cut-off section, a resonance section and a radiation section which are sequentially connected, wherein a coupling gap or a coupling hole array which is periodically spirally distributed and meets the Bragg resonance condition in the angular direction and the axial direction is axially arranged on the waveguide wall of the inner conductor in the resonance section. The mode exciter has the advantages of simple structure, high vector mode purity, high coupling efficiency, high purity bandwidth and less number of stray modes.)

1. A circular polarization coaxial embedded circular waveguide mode exciter is a coaxial waveguide structure with an inner conductor in a circular waveguide form and comprises a cut-off section, a resonance section and a radiation section which are sequentially connected;

the cut-off section is a truncated cone-shaped coaxial waveguide structure with a constant radius of the inner conductor and a gradually expanded radius of the outer conductor; the resonance section is a uniform open type coaxial waveguide structure; the radiation section is also a truncated cone-shaped coaxial waveguide structure with a constant radius of an inner conductor and a gradually expanded radius of an outer conductor;

in the resonance section, a coupling slot or a coupling hole array which is periodically spirally distributed and meets the Bragg resonance condition in the axial direction and in the angular direction is arranged on the inner conductor waveguide wall along the axial direction.

Technical Field

The invention belongs to the field of mode exciters, and particularly relates to a circularly polarized coaxial embedded circular waveguide mode exciter.

Background

The gyrotron is a typical representative of a high-power millimeter wave source, and has the advantages of high power, long pulse and continuous wave output and the like. The method is mainly applied to the aspects of millimeter wave radar, communication, high-energy physics, controlled thermonuclear fusion, high-power microwave weapons, high-power electromagnetic heating and the like. The working mode in the gyrotron is usually a high-order side corridor mode or a high-order body mode, which is not convenient for direct utilization and transmission, and a quasi-optical mode converter is usually adopted to convert the working mode into a low-order mode which is easy to utilize and transmit. In order to accurately test the performance of the quasi-optical mode converter, a high-purity circularly polarized high-order mode exciter needs to be designed to simulate the output mode of the gyrotron.

At present, high-order exciters mainly comprise two types, namely waveguide mode excitation and quasi-optical mode excitation. The first type adopts a waveguide structure, realizes mode conversion by utilizing periodic disturbance, and has higher mode conversion efficiency when being used as a mode exciter. In 2006, the russian academy of sciences applied to the physical research institute a.a.bogdashov and m.yu.golov et al proposed a method of exciting higher order modes from a rotating circularly polarized mode within an axisymmetric cavity through a coaxial bi-periodic spiral perforated waveguide, ensuring total energy transfer of the system from the waveguide to the cavity by determining the relationship between dimensional parameters. According to the scheme, the research institute in 2007 designs the circular waveguide TE₁₁-coaxial waveguide TE₅₃Mode exciters and found in the published literature: the coupling efficiency reaches 98% within 29.75-30.25 GHz. A rectangular waveguide TE is designed according to the theory of cavity wall coupling of coaxial outer conductors and radial gradual change coupling of circular waveguides by Wangxiangguanjian of the university of electronic science and technology in 2010₁₀-circular waveguide TE₆₂A mode exciter. TE at a center frequency of 94GHz is given in the article₆₂The mode purity was 91.37% and the conversion efficiency was 91.27%. Gunny conductor and the like of institute of electronics of Chinese academy of sciences in 2017 design a W-band circular waveguide TE₆₂Mode exciter having a mode conversion sequence of rectangular waveguide TE₁₀-coaxial waveguideTE₆₁-circular waveguide TE₆₁-circularly polarized TE₆₁-circularly polarized TE₆₂The mode conversion efficiency was 90%, and the mode purity was not mentioned. The second type is the use of quasi-optical structures, presented in 1995 by Russian Alexandrov and Denisov et al to excite a circular waveguide mode TE in a coaxial resonator using quasi-optical techniques at a low power level of 118GHz_22,6The quasi-optical mode exciting structure consists of a corrugated Gaussian horn, two microwave reflecting mirrors, a coaxial resonant cavity and a fixed structure, and the method comprises the steps of searching a proper ratio of inner radius to outer radius of the coaxial resonant cavity by analysis, separating adjacent modes, determining the important size of the resonant cavity and obtaining TE_22,6The mode spectrum of the optimum resonance frequency of 118.06GHz shows good mode purity. In 2000, d.wagner and m.blank et al suggested that the performance of quasi-optical mode converters in cold-side gyrotron necessitates excitation of high order gyrotron cavity modes at low power levels, and for this purpose a quasi-optical solution was devised, i.e. a gaussian beam generated by a scalar feed horn was focused to the specified mode's caustic in the waveguide using two cylindrical dielectric lenses and a quasi-parabolic metal mirror, and high output mode purity and quality factor could be achieved through cavity profile optimization. In 2006, T.S.Chu and M.blank et al introduced a quasi-optical TE of 95GHz_22,6The design and implementation of the mode exciter introduces the design that the input beam enters the cavity through the hole wall of the resonant cavity by parabolic mirror reflection, which only gives a scanning picture of the output port of the mode exciter and does not give specific purity and conversion efficiency. 2011, Zhao Xiao Na, university of electronic technology, designed three-stage TE by using boundary slowly-variable cross section condition₆₂A resonant cavity, a quasi-paraboloid designed by geometric optics theory and Gaussian beam approximation theory, and a quasi-paraboloid mirror for feeding the plane beam provided by the excitation source into the coaxial resonant cavity to directly couple out circularly polarized TE₆₂And calculating the mode purity to be 96% and the conversion efficiency to be 45.45%. In 2016, the university of electronic technology in the morning was designed a set of quasi-optical TE including a Gaussian horn, a convex lens, a cylindrical lens, a quasi-parabolic mirror and a coaxial resonant cavity₆₂The mode exciter system has 95% of mode purity obtained by simulation and 90% of actually measured purity. 2018, electronic departmentThe Li palace of technology university designs a set of plug-in board type coaxial waveguide mode exciters which realize coaxial TEM-circular waveguide TE at 14GHz₆₂The mode conversion efficiency and the mode purity of the mode exciter at the central frequency can reach more than 99 percent, but the designed polarization mode is linear polarization, and a plurality of intermediate transition devices are required to realize the conversion from the linear polarization to the circular polarization when the mode exciter is applied to a gyrotron.

Disclosure of Invention

The invention provides a circularly polarized coaxial embedded circular waveguide mode exciter, aiming at the problems of complex structure, high assembly precision requirement, excessive transition devices, low conversion efficiency and low mode purity of the existing high-order mode exciter.

The invention is realized by the following technical scheme:

a circularly polarized coaxial embedded circular waveguide mode exciter is a coaxial waveguide structure with an inner conductor in a circular waveguide form and comprises a cut-off section, a resonance section and a radiation section which are sequentially connected.

The cut-off section is a truncated cone-shaped coaxial waveguide structure with a constant radius of the inner conductor and a gradually expanded radius of the outer conductor; the resonance section is a uniform open type coaxial waveguide structure, and the intrinsic value of a waveguide mode can be adjusted by changing the ratio of the inner radius to the outer radius of the coaxial waveguide so as to improve the mode isolation; the radiation section is a truncated cone-shaped coaxial waveguide structure with a section of inner conductor with constant radius and gradually expanded radius of the outer conductor.

TE in the cut-off section, in the cavity₅₃The mode is totally reflected back to the cavity, and simultaneously the low order mode is transmitted out through cutting off the port to this Q value that reduces the low order mode suppresses the resonance of miscellaneous mode at the cavity.

In the resonance section, a coupling slot or a coupling hole array which is periodically spirally distributed and meets the Bragg resonance condition in the axial direction and in the angular direction is arranged on the inner conductor waveguide wall along the axial direction. The proper ratio of the inner radius to the outer radius of the coaxial waveguide is selected to ensure that the coaxial TE₅₃The ratio of the difference between the eigenvalues of a mode and its neighboring mode eigenvalues corresponds to the TE in the circular waveguide₅₃The difference between the eigenvalues of the mode and its neighboring modes is large, then TE is present₅₃The difference in phase constant between the mode and the hetero mode is also large, so that the coaxial waveguide is more advantageous for separating the hetero mode than the circular waveguide.

The radiation section is TE₅₃Transition section of the die, not only can enable TE in the cavity₅₃The mode part is reflected back to the cavity to form standing wave resonance and TE₅₃The mode radiates in a traveling wave through the radiation port. Meanwhile, TE cannot be generated after the radius of the radiation port is expanded₅₃Higher order modes of the mode, i.e. TE₅₃The mode cannot be converted to another mode.

The invention has the advantages that:

(1) the coaxial waveguide is adopted as the prototype of the mode exciter, and is more favorable for separating the mixed modes than the circular waveguide.

(2) A bragg resonance condition is employed which provides a one-time transition possibility for the waveguide mode exciter to transition from a lower order mode exciter to a higher order mode.

(3) The open resonant cavity is adopted, so that stable oscillation modes with high Q values can be excited, radiation to the surrounding space can be realized, and the problem of dense oscillation frequency spectrum of the closed resonant cavity is solved.

(4) Compared with a circularly polarized aperture coupling coaxial embedded circular waveguide mode exciter, the coupling efficiency of the circularly polarized aperture coupling coaxial embedded circular waveguide mode exciter is obviously improved, and the coaxial waveguide TE is inhibited to a certain extent₅₃Mode right hand circularly polarized component exciting more pure left hand circularly polarized coaxial waveguide TE₅₃And (5) molding.

Drawings

FIG. 1 is a schematic diagram of an open coaxial resonant cavity structure;

FIG. 2 is a schematic diagram of a mode exciter model of a pinhole-coupled coaxial embedded circular waveguide;

FIG. 3 is an aperture-coupled coaxial waveguide TE₅₃A mode cross-section electric field schematic;

FIG. 4 is a diagram of a circularly polarized TE of an aperture-coupled coaxial embedded circular waveguide mode exciter₁₁A power reflection diagram of a mode;

FIG. 5 is a schematic diagram of the coupling efficiency of the energy coupling of the aperture-coupled coaxial embedded circular waveguide mode exciter into the coaxial resonant cavity;

FIG. 6 is a schematic diagram of a slot-coupled coaxial embedded circular waveguide mode exciter model;

FIG. 7 is a slot-coupled coaxial waveguide TE₅₃A mode cross-section electric field schematic;

FIG. 8 is a slot-coupled coaxial embedded circular waveguide mode exciter circularly polarized TE₁₁A reflection diagram of a mode;

FIG. 9 is a schematic diagram of the coupling efficiency of the energy coupling of a slot-coupled coaxial embedded circular waveguide mode exciter into a coaxial resonant cavity.

Description of reference numerals: 1 denotes a coupling hole; and 2 denotes a coupling slot.

Detailed Description

In order to make the technical solutions and advantages of the present invention clearer, the present invention is further described in detail below with reference to the accompanying drawings in combination with specific embodiments.