共查询到20条相似文献,搜索用时 328 毫秒
1.
Ahmed S. Raju D. Chaturvedi S. Jha R. 《Electromagnetic Compatibility, IEEE Transactions on》2005,47(1):171-182
We have analyzed the electromagnetic-mode structure inside a bounded-wave electromagnetic pulse (EMP) simulator. This has been done by the application of the singular value decomposition method to time-domain data generated by self-consistent, three-dimensional finite-difference time-domain simulations. This combination of two powerful techniques yields a wealth of information about the internal mode structure which cannot be otherwise obtained. To our knowledge, this is the first time such a comprehensive study has been done. In the absence of a test object, the transverse electromagnetic (TEM) mode is dominant throughout the simulator length. TM/sub 1/ dominates over other transverse electromagnetic (TM) modes over most of the length. Close to the termination, the TEM mode weakens marginally, while higher order TM modes become stronger. The enhancement of TM/sub 2/, and the weakening of TEM near the termination, have been explained in physical terms. Placement of a perfectly conducting test object in the parallel-plate section increases the strength of higher order TM modes, at the cost of TEM. Hence, the object is subjected to electromagnetic fields that deviate significantly from the desired TEM form. A physical interpretation has been provided for this phenomenon. The enhancement of electromagnetic fields near the top and bottom faces of the object are explained in terms of the Poynting flux distribution. 相似文献
2.
《Electromagnetic Compatibility, IEEE Transactions on》2009,51(4):1026-1033
3.
《Microwave Theory and Techniques》1987,35(12):1143-1149
The cylindrical cavity dual orthogonal transverse magnetic (TM) mode is introduced as a basic building block for the realization of microwave multiple-coupled-cavity bandpass filters. This concept is shown to offer significant advantages in the design of triple-mode filters and permits the design of the new quadruple-mode filter. Experimental verification is provided by the realization of a triple-mode, six-pole elliptic function bandpass filter with dual TM/sub 110/ and single TE/sub 211/ (transverse electric) modes and a quadruple-mode, eight-pole bandpass filter with dual TM/sub 110/ and dual TE/sub 112/ mode cavities. All units exhibit good agreement between theory and experiment. 相似文献
4.
高频开关电源EMC设计 总被引:3,自引:0,他引:3
介绍了我国和欧洲开关电源的电磁兼容标准,针对高频开关电源的工作特点,着重探讨了电磁脉冲设计、电源印制板EMC设计、EMI电源滤波器的设计和屏蔽等电磁干扰抑制方法,通过这些方法的实施,确保高频开关电源满足CISPR22 B级标准的要求. 相似文献
5.
《Microwave Theory and Techniques》1979,27(12):982-986
An appropriate modification of the shape of a cylindrical filter cavity has been used to separate the degenerate TM/sub 111/ (doublet) modes while at the same time providing a slight increase in the already high unloaded Q of the desired TE/sub 011/ mode. Experimental results of mode frequencies and unloaded Q's are tabulated for a family of shaped cavities. Two low-loss filters utilizing these cavities are discussed. The general correspondence between modes of spherical, cylindrical and rectangular cavities and waveguides is described in order to place the performance of intermediate shapes in perspective. 相似文献
6.
7.
On Solving Waveguide Junction Scattering Problems by the Conservation of Complex Power Technique 总被引:1,自引:0,他引:1
《Microwave Theory and Techniques》1981,29(4):337-343
Normal mode expansions are used to mode match the tangential electric field at the transverse junction of two cylindrical waveguides. Instead of mode matching the tangential magnetic field the principle of conservation of complex power is invoked and leads, without a matrix inversion, to an expression for the junction's input admittance matrix, as seen from the smaller guide. Simple matrix algebra and the reciprocity theorem then provide the generalized scattering matrix of the two-port (with higher order modes included). It is also shown that the solution satisfies the continuity condition for tangential magnetic field in the junction's aperture. Numerical results are given for parallel plate waveguides with TEM, TE/sub 1/, and TM/sub 1/ incident fields, numerical convergence being achieved with about ten modes in the smaller waveguide. 相似文献
8.
《Microwave Theory and Techniques》1981,29(2):107-114
The reflection and the scattering properties of even TE and TM surface waves incident in an abruptly ended dielectric slab waveguide are analyzed. The discontinuity is regarded as a junction between two open waveguides namely the dielectric slab waveguide and the free space waveguide. The boundary conditions acting together with the orthogonality provide singular coupled integral equations on the discrete and the continuous wave amplitudes at the discontinuity. These singular coupled intergral equations with Cauchy kernels and infinite limits of integration are solved by iteration via the Neuman series. Numerical results are presented for the reflectivity of the even TE/sub 0/ and TM/sub 0/ fundamental modes, together with their mode conversion on even TE/sub 2/ and TM/sub 2/ in a slab where two guided modes can propagate. Reflectivity and mode conversion of higher order excitations are also investigated 相似文献
9.
《Microwave Theory and Techniques》1966,14(5):233-239
The coupling coefficient between the TE/sub 11/ mode and the TM/sub 11/ mode in tapered circular waveguides is derived, and at cutoff frequency it tends to approach an infinity of the order of 0/sup -1/4/. It is surprising to discover that the corresponding coupling coefficient between the TE/sub 10/ mode and the TM/sub 12/ mode in tapered rectangular waveguides approaches instead a zero of the order of 0/sup 1/4/ at cutoff frequency. Accordingly, for the modes concerned, the choice of using circular or square waveguides as tapers for transition at and near cutoff frequency is significant in reducing mode conversion level. At and near cutoff frequency a "synthesized" square taper is better in that it is shorter than a "synthesized" circular taper for the same mode conversion levels. On the other hand, for frequencies far away from cutoff the choice is insignificant. Design procedures for "synthesized" waveguide tapers at and near cutoff are presented, and the results of measurements are in agreement with the theoretical calculations. 相似文献
10.
Edward Kai-Ning Yung Ze Ming Xie Ru Shan Chen 《Microwave Theory and Techniques》2000,48(10):1707-1711
The Green's functions for determining the electromagnetic fields inside a semiinfinite coaxial line due to a radially directed, infinitesimally thin, and short-current element have been derived. In addition to the TEM mode, TE and TM modes are also considered. Based on the Green's functions, a closed-form formula for determining the input impedance of a probe in a coaxial line terminated at an arbitrary load has been derived. Good agreement is observed between the theoretical results and experimental measurements over a wide frequency band for several configurations of interest. At low frequencies where the TEM mode is dominating, there is practically no difference between the results obtained by the rigorous analysis and those by a simple formula derived from the transmission-line theory. However, at frequencies where TE and TM modes are no longer insignificant, there is a noticeable discrepancy between the results obtained by the rigorous and not-so-rigorous methods 相似文献
11.
反激式开关稳压电源传导干扰研究 总被引:1,自引:0,他引:1
开关式直流稳压电源的电磁干扰不仅对电网产生干扰,导致在同一电网上供电的其它设备不能正常工作,而且严重的谐波电压电流会在开关电源内部产生电磁干扰,从而造成开关电源内部工作不稳定,使开关电源性能降低。文中以反激式开关稳压电源为研究对象,主要分析了传导测试中,差模、共模传导两种方式噪声源的产生机理,建立了开关电源传导干扰模型,采用EMI滤波器即共模滤波和差模滤波,并详细研究了加入π型滤波器、输入x电容、共模扼流圈等对开关稳压电源传导干扰的抑制效果,得出传导干扰抑制在标准限制范围的改进措施,整改后可让传导干扰强度从100μV降低到200 nV并通过认证。研究结果表明该措施对抑制开关稳压电源传导干扰是有效的。 相似文献
12.
在要求低漏电流的电子设备中使用的开关电源不能采用Y电容,但无Y电容的开关电源往往难以通过EMC测试。文中通过分析开关电源中造成电磁干扰问题的原因和解决方法,提出利用吸收电路来抑制无Y电容情况下开关电源的电磁干扰。测试表明,这种方法可以有效解决无Y电容的开关电源中EMI问题。 相似文献
13.
《Microwave Theory and Techniques》1971,19(4):386-392
Part I of this work investigates the phenomenon of mode reordering in circular waveguides containing one or more dielectrics. Specifically, conditions are established, be they ranges of dimensions, dielectric constants, or frequency, under which the sequence, TM/sub 01/, TE/sub 01/, TE/sub 11/, and TE/sub 21/ is obtained instead of the conventional TE/sub 11/, TM/sub 01/, TE/sub 21/, and TE/sub 01/. The desired effect is the reversal of the order of propagation between the normally dominant TE/sub 11/ mode and the circularly symmetric low-loss TE/sub 01/. Bandwidth regimes are drawn and the credibility of the dielectric model is examined and found to be satisfactory for the application of the phenomenon to the design of digital ferrite phase shifters operating in the TE/sub 01/ mode. 相似文献
14.
Simple Approximate Expressions for Higher Order Mode Cutoff and Resonant Frequencies in TEM Cells 总被引:1,自引:0,他引:1
《Electromagnetic Compatibility, IEEE Transactions on》1986,28(3):125-130
Simple approximate expressions for determining the cutoff frequencies of the first few higher order modes and the associated resonant frequencies in transverse electromagnetic (TEM) cells are presented. Both symmetric (seven TE and two TM modes) and asymmetric (three TE modes) cells are discussed. 相似文献
15.
《Microwave Theory and Techniques》1967,15(5):314-317
In an axially straight multimode circular waveguide taper excited with a pure TE/sup /spl circle// /sub 11/ dominant mode, the first and only converted mode at and near cutoff is the TM/sup/spl circle// /sub 11/ mode. It is shown that in an axially straight multimode square waveguide taper excited with a pure TE/sup/spl square// /sub 10/ dominant mode, the TM/sup/spl square// /sub 12/ mode corresponding to the TM/sup/spl circle// /sub 11/ mode in circular case is not the only first converted mode at and near cutoff. The overall behavior or coupling mechanism of waveguides is similar whether the waveguide is rectangular, square, circular, or elliptical: i.e., the overall coupling coefficient at cutoff of a converted mode or modes approaches an ininfinity of the order 0/sup -1/4/. 相似文献
16.
17.
Tse K.K. Henry Shu-Hung Chung Ron Hui S.Y. So H.C. 《Industrial Electronics, IEEE Transactions on》2002,49(3):618-627
A rigorous mathematical analysis and a comparative study of carrier-frequency modulation (CFM) techniques for the conducted electromagnetic interference (EMI) suppression in pulsewidth-modulated converters is presented. CFM techniques dither the switching period with a small amplitude variation around the nominal value, so that the harmonic power is redistributed over the spectrum of concern. Two types of dithering signals, including the periodic and random signals, are investigated in this paper. The operational characteristics as well as the input and output power spectra of the converters with the two modulating signals are compared. In particular, their characteristics in the low- and high-frequency harmonic power redistribution will be depicted. It is shown that random CFM (RCFM) gives a more effective way to disperse the harmonics around the switching frequency than the periodic CFM (PCFM) with the same frequency deviation. However, RCFM introduces higher low-frequency harmonics than the PCFM at the converter output. Furthermore, effects of the resolution filter bandwidth in the electromagnetic compatibility analyzer on conducted EMI measurement is discussed. The validity of the analyses is confirmed experimentally by using a dc/dc buck converter operating in continuous conduction mode 相似文献
18.
A Fast Stroud-Based Collocation Method for Statistically Characterizing EMI/EMC Phenomena on Complex Platforms 总被引:1,自引:0,他引:1
《Electromagnetic Compatibility, IEEE Transactions on》2009,51(2):301-311
19.
Ishaaya A.A. Davidson N. Machavariani G. Hasman E. Friesem A.A. 《Quantum Electronics, IEEE Journal of》2003,39(1):74-82
Intra-cavity binary phase elements are incorporated into a Q-switched Nd:YAG laser resonator to obtain efficient high-order transverse mode selection. The resonator configuration is analyzed using the propagation-matrix diagonalization method and the Fox-Li algorithm, and a simple model for predicting the relative output powers of the selected modes is developed. The predicted results are verified experimentally with binary phase elements for selecting the TEM/sub 01/, TEM/sub 02/ and TEM/sub 03/, degenerate Laguerre-Gaussian modes. The output energy per pulse was 15 mJ for the TEM/sub 01/, 16.5 mJ for TEM/sub 02/ and 18.3 mJ for TEM/sub 03/, all higher than the 10 mJ for the TEM/sub 00/. The performance in Q-switched operation was found to be similar to that in free-running operation. The numerical calculations, experimental procedure and experimental results are presented. 相似文献