Design of short high-power TE11-HE11 modeconverters in highly overmoded corrugated waveguides

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≈0.5λ_B (short converter) and L₂≈1.2λ_B (long converter), where λ_B 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     

同轴TE11模与矩波导TE10模的耦合计算

首先建立同轴TE11模与圆波导TE11模的等效关系。进而将同轴TE11模与矩波导TE10模的耦合问题转化为其等效圆波导TE11模与矩波导TE10模的耦合问题。实验证明,理论计算与实测结果吻合。     

Broadband linearly polarized beat-wave TEm1/TE11 mode converters

Broadband linearly polarized waveguide mode converters have been developed to transform the high-order cylindrical TE_m1 output wave from harmonic gyrotron amplifiers into the more useful TE₁₁ fundamental waveguide mode. The converter's corrugation period is equal to the beat between the two waves and the bandwidth is predicted to be inversely proportional to the number of periods. Four-period TE ₃₁/TE₁₁ and TE₄₁/TE₁₁ converters with an azimuthal perturbation of m_c=4 and m_c =5, respectively, have yielded a peak conversion efficiency of 98% with a bandwidth greater than 3% and a one-period beat-wave converter has been designed to yield 12% bandwidth. However, it has been observed in measurements that the strong coupling in a short converter can lead to a shift of the center-frequency with an accompanying reduction of the efficiency and bandwidth. A two-period TE₄₁/TE₁₁ converter with 5% bandwidth displayed a 5% frequency shift and a conversion efficiency of only 86%     

Thick circular iris in a TE11 mode circular waveguide

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     

Compact quasi-periodic and aperiodic TE0n modeconverters in overmoded circular waveguides for use with gyrotrons

Designs of compact quasi-periodic and aperiodic TE_0n-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     

Ka波段紧凑型TE01-TE11椭圆波导模式转换器的研究(英文)

本文对椭圆波导TE₀₁-TE₁₁模式转换器进行了研究。选择了合适的椭圆波导截面,在椭圆波导纵轮廓线函数中采用了相位重匹配方法,并利用粒子群算法进行了纵轮廓线优化,所设计的椭圆TE₀₁-TEs₁₁模式转换器在28 GHz时的转换效率为99.16%,在27～29.3 GHz模式变换器的效率大于90%,相对带宽为8.2%。所设计的TE₀₁-TEs₁₁椭圆模式转换器的转换段为现有长度的一半。将设计的椭圆模式转换器与两个过渡段相连,并在CST中进行仿真和验证,其结果与理论计算一致。设计出了一个中心频率点为28 GHz的高效、紧凑、高功率椭圆波导TE₀₁-TE₁₁模式转换器。     

Radiation characteristics of a corrugated circular cylindricalwaveguide horn excited in the TE11 mode

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     

Two port analysis of dielectric resonator antennas excited in TE01 mode

Results of a numerical and experimental study of the transmission and input reflection coefficients of a two element array of half-split cylindrical dielectric resonator (CDR) antennas are presented. The antenna elements are situated on a ground plane and fed by a coaxial probe. A procedure based on the method of moments (MoM) for the coupling of a body of revolution (BOR) to a non-BOR geometry together with classical microwave network theory is implemented. Some of the numerical results are verified experimentally     

Microwave Hall effect in a TE11p cylindrical cavity

A microwave Hall effect signal produced by a TE_11p degenerate cylindrical cavity is considered. The analysis presented identifies the cavity end walls as the source of the Hall signal, and a formula relating the Hall output power to the dimensions of the cavity is derived. Experimental results from the measurement of the empty cavity signal at 9.5 GHz are reported     

一种同轴波导TE01模到圆波导TE02模变换器的数值模拟

该文对一种同轴波导TE01(°)模到圆波导TE02(°)模变换器进行数值模拟研究.通过分析同轴波导与圆波导对接产生的模式转换效果,探讨尖劈模式变换段改善工作模式转换系数和工作频带以及抑制寄生模式的作用.利用Ansoft HFSS对模型进行的数值模拟计算结果表明,这种结构能够实现最大将89.3%输入信号能量转换到TE02(°)模,-3dB带宽约820MHz,带内对主要干扰模式TE01(°)的抑制在10dB以上.     

A single-period TE02-TE01 mode converter in ahighly overmoded circular waveguide

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     

A note on the cutoff frequency of TE01 mode in TEM cells

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     

Design of triple mode TE01δ resonator transmissionfilters

The use of triple mode TE_01δ cubic resonators for the design of transmission mode filters is presented. Frequency tuning and coupling between modes are studied experimentally. The tunability of all inter-cavity couplings, necessary for the realization of a wide range of transfer functions, is demonstrated with a 6th degree, 5 MHz wide filter at 2 GHz. With an insertion loss of 0.7 dB in a volume of 260 cm³, the filter presents a 2:1 volume reduction over conventional TE_01δ filters     

Study of TE0 and TM0 modes in dielectricresonators by a finite difference time-domain method coupled with thediscrete Fourier transform

An application of a numerical method of finite differences in the time domain (FDTD) coupled with the discrete Fourier transform is presented to determine the resonant frequencies of the TE₀ and TM₀ modes of axially symmetric dielectric resonators closed in a cavity. The technique is conceptually and computationally simple, and it allows access at once to information on the entire modal spectrum by means of the fast Fourier transform (FFT) applied to the time series. The cylindrical cavity dielectrically loaded at the base and the resonant frequency of the TE_01δ mode are analyzed in two systems: a cylindrical cavity with a cylindrical dielectric resonator of variable radius, and the shielded dielectric resonator on a microstrip substrate. The results obtained are compared with the rigorous (exact) theoretical solutions and with experimental results     

X波段速调管功率合成输出结构研究(TE01模输出窗设计)

在对X波段高峰值功率微波源迫切需求的牵引下,该文为X波段高峰值功率速调管功率合成输出结构设计了一个工作在9GHz的TE01模输出窗,输出窗相对带宽大于7%,通带内插入驻波比小于1.2.此外,该文还建立了TE01模输出窗窗片稳态温度分布的计算方法.理论分析表明,该输出窗传输50MW的高峰值功率不会由于温升而出现窗片的破裂.     

TE21模回旋返波振荡的起振分析

该文基于回旋行波放大器的线性理论,对TE₂₁模回旋返波振荡起振长度和起振频率随导引中心半径、电压、速度比、注电流及工作磁场等参数的变化进行了详细的数值模拟,并给出了相应的物理解释,分析了TE₂₁模基波和二次谐波回旋返波振荡特点,研究了分布损耗对回旋返波振荡的抑制效果。所得结果对回旋行波放大器和回旋返波振荡器的设计有参考意义。     

Design and Optimization of TE011 Resonant Modes in Metallic-Dielectric Cavities

In this work, we present an innovative approach for designing small-scale microcavity resonators. By introducing a gold cladding around the structure, we may significantly reduce the mode volume and simultaneously increase the cavity's quality Q-factor. By making use of the TE₀₁₁ mode, as opposed to the more traditional HE₁₁₁ mode, we may further reduce the mode volume while taking advantage of decreased loss into the metal layer due to the optimal polarization choice. We demonstrate a means to design and optimize the cavity geometry to obtain desired spectral characteristics through the use of particle swarm optimization, and we present a cavity operating at 1.5 mum with a Q value exceeding 300 000 and a modal volume of less than 0.9(lambda/n)³.     

Ka波段TE_（01）模回旋速调管带新型渐变段输出腔设计

利用正余弦拟合的方法和半径渐变波导的耦合波理论,设计出一种Ka波段TE01模回旋速调管带该新型渐变段输出腔。通过Matlab数值计算和HFSS仿真优化,研究了该新型渐变段的传输参数、反射参数、对杂模的抑制等性能指标。仿真结果表明：在渐变段长度为80mm、口径由14mm变化到32mm的情况下,在33～35GHz的范围内该新型渐变的传输参数大于-0.016dB,反射参数小于-55dB,对TE02模的耦合为-25dB和对TE03模抑制在-55dB以下;而该输出腔的中心频率为34.075GHz,Q值为109.6,工作模式TE01模式的模式纯度大于0.94。     

Novel TE10δ rectangular-waveguide-type resonatorsand their bandpass filter applications

New dielectric-filled rectangular-waveguide-type TE_10δ resonators are presented. A dielectric-filled rectangular waveguide section (WGS) has inductive impedance at the open-end faces. Using this property and the frequency dependency of the wave impedance of the WGS, we calculated the resonant frequency and the slope parameter of the waveguide-type resonators. The resonant frequency depends strongly on the width of the WGS and loosely on the height and the length. The calculated resonant frequencies agree well with measured data. One of the proposed bandpass filters shows highly reduced spurious up to three times the center frequency. Quality factors of the resonator and effects of a housing are also discussed     

Precision measurement of coupling between microstrip and TE01 mode dielectric resonator

The coupling between a microstrip transmission line and a dielectric resonator with a relative dielectric constant of 80 has been measured as a function of the distance between the resonator and the microstrip. Precision measurement involves the TRL de-embedding procedure, and data fitting to a fractional linear transformation on a complex plane. A comparison is made of covered and uncovered resonators, demonstrating the influence of radiation