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1.
Designs of compact quasi-periodic and aperiodic TE0n-TE 0n-1 circular waveguide converters for use with gyrotrons in an electron cyclotron heating (ECH) system are developed by analytically and numerically solving the coupled-mode differential equations. Quasi-periodic mode transducer designs which convert the TE02 mode to the TE01 mode, and in some cases also include a taper (waveguide radius reduction), are developed. A 60-GHz aperiodic mode converter-taper combines a 6.35-cm-2.779-cm waveguide diameter taper and a TE02-TE01 mode converter. A 140-GHz aperiodic mode converter-taper combines a 6.35-cm-2.779-cm waveguide diameter taper and a TE03-TE02-TE01 mode converter. The resulting designs are highly efficient (conversion efficiencies ⩾99.4%), are shorter, have a broader bandwidth than previous designs, and have a waveguide radius greater than or equal to 1.389 cm over the entire length of the transducer to allow for high-power transmission. Experimental results consistent with theoretical calculations are presented  相似文献   

2.
A single-period 60 GHz TE02-TE01 mode converter for use in an electron cyclotron heating (ECH) system for magnetically confined plasmas is presented. The mode converter is very compact and has a broad bandwidth and a theoretical conversion efficiency of 97.6%. A method of computing the reflection from converters is presented and used to show that reflection from the single-period mode converter is minimal. Experimental results are consistent with theoretical calculations  相似文献   

3.
A theoretical parametric study of TE11 to HE11 mode conversion in highly oversized, circumferentially corrugated circular waveguides with different inner diameters is presented for various frequencies in the range of 28 to 140 GHz. The depth of the annular slots is tapered gradually from one half to one quarter wavelength. Computer-aided optimization of converter length, shape of corrugations, and nonlinear slot depth variation has been achieved with a scattering matrix code employing the modal field matching techniques (modular analysis concept). Relatively short mode transducers with matched converter lengths are feasible. The optimum conversion lengths are L1≈0.5λB (short converter) and L2≈1.2λB (long converter), where λB is the beat wavelength of the TE11 and TM11 modes in the corresponding smooth-walled circular waveguide. The predicted performances of short and long mode transducers are practically identical. Experimental results taken at 70 GHz (i.d.=27.79 mm) are in excellent agreement with the theoretically predicted performance data. In all cases the HE11 output mode purity is 99% to 99.5%. The maximum cross-polarization and input-reflection levels are below -29 dB and -50 dB, respectively  相似文献   

4.
An efficient method for the determination of the scattering matrix of TE11-to-HE11 corrugated cylindrical waveguide mode converters has been developed, based on the representation of the fields inside the corrugations by a small number of radial waveguide modes. Numerical results show that the method, when compared to the usual mode-matching techniques, reduces the computation time without loss of accuracy  相似文献   

5.
In this paper, we report the design methodology and numerical results for two mode converters that are suitable for high-power microwave applications. Both converters are designed to operate at 11.424 GHz and utilize periodic serpentine structures to convert between modes with different azimuthal-mode indexes. The first converts about 98.5% of an incident linearly polarized TE12 mode to the TE 01 mode when oriented as an H-plane bend, but has just 1% mode conversion to all modes when oriented as an E-plane bend. The second device converts a linearly polarized TE11 mode to a TM 01 mode with over 99.99% effectiveness. The performance of both devices with respect to parametric variations is detailed. Experimental measurements of the radiation patterns from the TE12 -to-TE01-mode converter are consistent with the theoretical predictions  相似文献   

6.
In this paper, a numerical study of direct TM01-TE11 mode converters in highly overmoded, bent smooth, circular waveguides is presented for high-power millimeter waves. The various shapes of bent waveguides are elaborately chosen, and their optimized geometrical dimensions have been achieved with a general optimization code employing the coupled mode theory. The mode converters designed can have high conversion efficiencies over 98% and wide bandwidths of 28%  相似文献   

7.
It is shown that due to the similarity of the structures of the TEM cell and the finned waveguide, the closed-form expression for the cutoff frequency of the TE10 mode in the finned waveguides can be used to calculate the cutoff frequency of the TE01 mode in the symmetric TEM cells. The results obtained by the expression given agree with various numerical methods to within 1%. The results calculated by this expression are compared with those obtained by an approximate analytical expression  相似文献   

8.
一种使用TE11为过渡模的TE01-HE11模式变换器设计   总被引:1,自引:0,他引:1  
基于弯曲圆波导耦合理论和规则圆波导突变结构模式匹配法, 利用MATLAB软件编写的相关数值计算程序得到波导模式转换结构的优化参量, 最终使用CST软件对模型进行了仿真和验证.该系统主要由三部分组成: 一个TE01-TE01的过渡器, TE01-TE11和TE11-HE11的圆波导模式转换器.计算结果表明, 该TE01-HE11模式转换系统在24.13 GHz的频率有5%的带宽、转换效率超过了99%.计算结果、仿真结果和实物冷测结果是一致的.  相似文献   

9.
Collinear acoustooptic TM-TE mode conversion is experimentally investigated in proton exchanged Ti:LiNbO3 optical waveguides. Their birefringence is adjusted by an appropriate annealing to allow phase matching at surface acoustic wave frequencies of about 90 MHz and 180 MHz, respectively. A planar mode converter with an efficiency of up to 90 percent is presented (87 MHz, 175 MHz). Furthermore, a combined acoustical/optical strip waveguide structure is developed as mode converter, leading to strongly reduced power requirements; only 0.3-mW acoustic power is sufficient to achieve a conversion efficiency of 50 percent  相似文献   

10.
In this paper, the resonant disk turnstile is introduced and analyzed. The disk turnstile differs from Dicke's full-waveguide turnstile in that four of the six ports are coaxial cable ports, yielding a much more compact turnstile, which is easier to construct. The disk turnstile operation is explained as a superposition of the disk TM01 mode (nonradiating) and the disk TM11 mode which couples directly to the circular waveguide (dominant) TE11 mode. A useful operating fractional bandwidth of 3% is possible as compared to a Dicke turnstile bandwidth of about 6%  相似文献   

11.
Brener  I. Chou  M.H. Peale  D. Fejer  M.M. 《Electronics letters》1999,35(14):1155-1157
A wideband wavelength converter is presented which is based on a cascaded second-order nonlinearity in periodically-poled LiNbO3 waveguides pumped at 1.5 μm. The converter uses counter-propagating beams in order to improve conversion efficiency and pump rejection. An internal conversion efficiency of -10 dB and a conversion bandwidth of 68 nm have been obtained in a 4 cm long device  相似文献   

12.
Theoretical and numerical results are presented on the propagation of infrared radiation in TE01-, TM01-, and TE11-like modes in an empty cylindrical, gold-coated waveguide of micron dimensions. Low-loss propagation is possible for the TE01-like mode, whose configuration is similar to that of the TE01 mode in a guide with perfectly conducting walls. Propagation is more lossy for the TM01- and TE11-like modes. While for small guide radii these modes resemble the TM01 and TE11 modes in a guide with perfectly conducting walls, they transform into surface waves as the guide radius is increased, with losses that are independent of guide radius  相似文献   

13.
A method employing appropriately placed parallel-metallic plates in the aperture of a TM01 mode circular waveguide source so as to have it produce pencil-beam radiation is described and analyzed. Programmed computations, with experimental verification, are given for the case of a C-Band TM01 source flared out to a conical horn so as to produce moderate (22 dBi) gain. Means of extending the method to achieve higher gains (40 dBi to 60 dBi) and to modify the plate arrangement so as to produce the same effect with a TE01 mode are briefly outlined  相似文献   

14.
张天钟  喻胜  张颜颜  牛新建  李宏福 《电子学报》2015,43(12):2360-2367
准光模式变换器是大功率输出回旋管的关键部件.采用高转换效率的准光模式变换器可以横向输出电磁波,增大收集极的尺寸,提高回旋管的输出功率,提高整管效率.该文设计的回旋管内置准光模式变换器由Denisov辐射器天线和四个反射镜组成,输入频率为94GHz,模式为TE6,2模.采用耦合波理论分析和优化了Denisov辐射器内的场分布,并根据矢量绕射理论编制数值模拟程序计算了各个反射镜上的场分布,其输出功率转换效率达97.2%.利用三维全波仿真软件feko6.0进行对比分析,最后加工所设计的结构并内置于回旋振荡管进行热测实验,结果表明其输出场分布与理论计算结果基本一致.  相似文献   

15.
The propagation behavior of the four lower-order modes, HE11 , TE01, TM01, and HE21, in a radially anisotropic cylindrical waveguide with liquid crystal cladding is studied both theoretically and experimentally. The cylindrical waveguide is a doubly-clad fiber with an isotropic core and inner cladding and a radially anisotropic outer cladding made of nematic liquid crystal. Theoretically, the propagation and decay constants for the TE01 and TM01 modes are obtained by solving the wave equations exactly, while those for the HE11 and HE 21 modes are derived using perturbation techniques under the weakly guiding approximation. It is predicted that in such a structure the guided TE01 mode can be separated from the leaky HE11, TM01, and HE21 modes. The theoretical results show good agreement with the experimental observations for a 3 cm long fiber cell with a 5 μm inner cladding radius  相似文献   

16.
针对微波带通滤波器小型化、高性能的应用需求,提出使用双/三模方形基片集成波导和共面波导混合结构设计带通滤波器.通过改变双模基片集成波导中TE102和TE201的谐振频率和外部耦合的强弱,可实现具有近似椭圆、非对称和无传输零点响应的双模滤波器;两个相同尺寸的共面波导作为谐振器蚀刻在基片集成波导表面,与TE102和TE201共同形成一个通带,设计具有多样性响应的四阶滤波器.在具有非对称响应四阶滤波器的基础上,使主模TE101频率移动到该通带附近,设计更宽带宽的五阶滤波器.并对设计的滤波器进行加工和测试.测试结果与仿真结果吻合,表明了该混合结构设计高性能滤波器方法的可行性.  相似文献   

17.
The TE11-mode excitation of a concentric circular iris of finite thickness in a circular waveguide is analyzed by Galerkin's method with even and odd excitation. Agreement between calculated and measured dominant mode scattering parameters is generally within experimental accuracy  相似文献   

18.
For a TM01δ mode dielectric rod resonator placed coaxially in a TM01 cutoff circular waveguide, characteristics such as the resonant frequency, its temperature coefficient, the unloaded Q, and the other resonances are discussed on the bases of accurate calculations using the mode-matching method. The results show that this resonator compares favorably with a conventional TE01δ mode dielectric resonator, particularly for realization of a high unloaded Q. Analytical results also verify that interresonator coupling between these two resonators can be expressed equivalently by a capacitively coupled LC resonant circuit. A four-stage Chebyshev filter having a ripple of 0.035 dB and an equiripple bandwidth of 27 MHz at a center frequency of 11.958 GHz was fabricated using these resonators. Its insertion loss is 0.5 dB, which corresponds to an unloaded Q of 17000, and no spurious response appears in the frequency range below 17 GHz  相似文献   

19.
The transverse mode propagation and amplification characteristics of a large electrode area, planar waveguide carbon dioxide laser amplifier have been investigated. Amplification of an imperfectly mode-matched input produces varying output beam quality with changing discharge conditions, through the modification of the propagation constants of the waveguide modes by the gas thermal lens. For improved mode-matching to the amplifier, a near ideal TE1 output is obtained without discharge-induced variations. The maximum gain coefficient for propagation in the fundamental mode is shown to be dependent on the radio frequency discharge conditions through the frequency dependence of the minimum stable power density. At 81 MHz, a gain coefficient of 0.65 m-1 at 50 torr pressure is obtained  相似文献   

20.
The design and experimental studies on a corrugated circular cyclindrical waveguide antenna that is feed-excited in the TE11 mode with suppressed far-out sidelobes are reported. To reduce the spillover in the region 90°⩽&thetas;⩽180°, an attempt was made to introduce circumferential corrugations on the outer surface of the waveguide wall. The design criterion used was that a minimum of 11 corrugations per wavelength were used, and in all there were 25 corrugations. The reason for selecting 25 corrugations was to ensure that the conduction currents induced on the outer walls of the guide were attenuated substantially and did not contribute to the far-out sidelobes. Measured E-plane and H-plane radiation patterns of the feeds and the corrugated waveguide are presented  相似文献   

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