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1.
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
2.
Vermeulen F.E. Wang T. James C.R. Robinson A.M. 《Lightwave Technology, Journal of》1993,11(12):1956-1964
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
3.
Tien-Jung Chen Shu-Hsia Chen 《Lightwave Technology, Journal of》1995,13(8):1698-1705
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
4.
McDermott D.B. Pretterebner J. Chong C.K. Kinney C.F. Razeghi M.M. Luhmann N.C. Jr. 《Microwave Theory and Techniques》1996,44(2):311-317
Broadband linearly polarized waveguide mode converters have been developed to transform the high-order cylindrical TEm1 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 mc=4 and mc =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% 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.
An evanescent-mode tester for ceramic dielectric substrates 总被引:1,自引:0,他引:1
The TE01 mode in a cylindrical waveguide at a frequency below cutoff is used to probe a ceramic dielectric substrate located on the central plane between input and output cooling loops. Maximum transmission occurs at a frequency determined by the waveguide radius, the substrate thickness, and the dielectric constant. The dielectric constant and loss tangent are obtained from the resonant frequency and the absorption bandwidth. The measurement is insensitive to the position of the substrate in the gap between waveguide sections, and no intimate contact is required 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.
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 L 1≈0.5λB (short converter) and L 2≈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
9.
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
10.
Optical bistability in reflective fiber gratings 总被引:3,自引:0,他引:3
Chao-Xiang Shi 《Quantum Electronics, IEEE Journal of》1995,31(11):2037-2043
Optical bistability in a nonlinearly reflective fiber grating through the mode coupling between the LP01 and counter propagation LP02 modes (i,e., the reflective LP01&rlhar2;LP02 mode converter) is investigated by using the coupled-mode theory. Both the transmissive and the reflective properties of this nonlinear device are analyzed, which show that the output-versus-input relation exhibits the optical bistability. The switching power and the bistable hysteresis performances are also discussed. In addition, the comparison between the nonlinearly reflective mode converter (LP01&rlhar2;LP02) and the nonlinear fiber Bragg grating reflector (i,e., the LP01 and counter-propagation LP01 modes) is also presented. It is shown that the former has much lower switching power than the latter 相似文献
11.
A quasi-optical mode converter with a bifocal mirror 总被引:1,自引:0,他引:1
This paper presents the design procedure of a quasi-optical mode converter to transform any kind of TEmn mode into a Gaussian wave beam and experimental results obtained in the particular case of the TE64 mode at 110 GHz. The quasi-optical system consists of a helical-cut launcher and a bifocal mirror, which is designed, using the techniques of geometric optics, to focus the radiation of the launcher into a Gaussian focal spot. Such a system was fabricated and tested for the transformation of the TE64 mode. The experimental results showed that about 80% of the power incident in the focal plane is focused into a small Gaussian-like spot of less than 20 mm diameter, while 97% of the power is contained into the main TE64 lobe 相似文献
12.
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
13.
为了实现光电子器件小型化和多功能化,进一步提高信息传输容量和速度,提出了一种基于光子晶体双波长电光调制和模分复用的片上集成器件。该集成器件的电光调制模块由硅基光子晶体波导和两个L3型复合腔组成,模分复用模块由硅基非对称平行纳米线波导组成,两个模块的连接处采用硅基光子晶体波导。采用L3型复合腔和PN掺杂结构实现两个波长TE0模的调制,采用非对称定向耦合结构将两个波长的TE0模转换为TE1模。应用基于三维时域有限差分法(3D-Finite Difference Time Domain,3D-FDTD)的Lumerical软件进行仿真分析,结果表明,在调制电压为1.05 V时,该集成器件可以实现中心波长为1 552.1 nm和1 556.1 nm的 TE0模、TE1模通断调制及两模式模分复用功能。该器件的消光比高达24.67 dB,调制深度均为0.99,插入损耗小于0.57 dB,信道串扰小于?34.68 dB,调制速率最低为17.54 GHz。该集成器件结构紧凑,可望应用于高速大容量光通信系统。 相似文献
14.
Vermeulen F.E. Robinson A.M. James C.R. McMullin J.N. 《Microwave Theory and Techniques》1994,42(10):1932-1938
An asymptotic form of the characteristic equation that describes wave propagation at near-infrared wavelengths in small core hollow circular waveguides is developed. Analytic solutions for the transverse and axial propagation constants are obtained. These demonstrate the transition of the TE11 and TM01 modes to surface waves as the guide radius is increased to values much greater than at cutoff. Relative power density distributions illustrating these mode transitions are shown 相似文献
15.
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
16.
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 TE01δ 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 相似文献
17.
A new polarimetric interferometer has been developed on the basis of the phase difference between transverse electric (TE)0 and transverse magnetic (TM)0 modes in a composite optical waveguide (OWG). The composite OWG consists of a single-mode potassium ion-exchanged planar waveguide overlaid with a high-index thin film that has two tapered ends and supports only the TE0 mode. Applying tapered velocity coupling theory, we found that the TE0 and TM0 modes coexisting in the potassium ion-exchanged layer were separated in the thin film region of the composite OWG: the TE0 mode was coupled into the thin film while the TM0 mode was confined in the potassium ion-exchanged layer. Interference occurs between TE- and TM-polarized output components when a single output beam is passed through a 45°-polarized analyzer. The phase difference φ between both orthogonal output components is very sensitive to the superstrate index nc in the thin film region. Our experimental results indicate that a slight change of Δnc=3.71×10-6 results in the phase-difference variation of Δφ=1° for a 5-mm-long TiO 2/K+ composite OWG with a 34-nm-thick TiO2 film. Such a simple polarimetric interferometer can be applied to chemical or biological sensors by modifying the upper film surface of the composite OWG with a chemically or biologically active substance 相似文献
18.
The use of triple mode TE01δ 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 TE01δ filters 相似文献
19.
Tate J.P. Hezhong Guo Naiman M. Leemian Chen Granatstein V.L. 《Microwave Theory and Techniques》1994,42(10):1910-1917
Proof-of-principle results for a mode selective input coupler are presented. Transmission and reflection measurements for the TE02 cylindrical waveguide mode are given along with the output mode pattern. The results show good agreement for the cutoff frequency, mode pattern general behavior and variation with frequency for signals above cutoff. A maximum passband of 1.2 GHz (~7%) has been achieved. Comparisons with theory for overall frequency response (from 15 to 18 GHz) and mode pattern characteristics (at 17.5 GHz) are also presented. The design and concept are promising for harmonic gyrotron-traveling-wave-tube amplifier and phase-locked gyrotron oscillator applications 相似文献
20.
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