Transient response of microstrip step discontinuities on anisotropic substrate

In this paper, we present the numerical simulation of transient response of short pulse propagating through a microstrip step junction on anisotropic substrate having a tilted optical axis. In the simulation, the FD-TD method is extended to treat the cases having tilted optical axis expressed by a permittivity tensor with off-diagonal elements. The results show that the dispersion of transient signal caused by microstrip step discontinuities is quite significant and the dependence of transient characteristics of microstrip lines on the tilted angle of optical axis for anisotropic substrate can not be neglected.     

Transient analysis of microstrip lines with ferrite substrate by extended FD-TD method

In this paper, the wide band transient signal propagation characteristics along microstrip lines with ferrite substrate are presented. In the analysis how the frequency dependent media such as ferrite may be genearally fomulated by FD-TD method is described. the distortions of transient signal in Gaussian shape propagating along uniform or step junction microstrip are simulated by the extended FD-TD method. Results show the distinctive influence of applied DC magnetic field and magnetizaton on the dispersion of transient signal.     

一种有损非均匀传输线时域分析方法

提出利用等效电路法解决电磁脉冲注入下有损非均匀传输线及其网络端接非线性负载的时域响应问题。采用分段逼近级联方法建立了有损非均匀传输线的等效电路模型。利用设计的快沿电磁脉冲源对有损非均匀微带线端接电阻、瞬态抑制二极管的响应进行了试验和仿真对比分析,验证了该等效电路模型的正确性和解决非线性负载响应问题上的有效性。通过与FDTD法对更复杂的有损非均匀传输线、不等长有损非均匀传输线、有损非均匀传输线网络的仿真结果和计算机运行时间进行对比分析,进一步验证了该等效电路法的正确性以及在解决有损非均匀传输线问题上的普遍适用性和高效性。     

Effects of substrate anisotropy on the dispersion of transient signals in microstrip lines

The analysis of dispersion characteristics of transient signal in microstrip lines with anisotropic substrate is developed here, with particular attention directed toward the effects of arbitrary orientations of the principal optical axis in anisotropic substrates. Numerical simulations are carried out for the propagation of transient signals, square or Guassian pulses, along microstrips with anisotropic substrates. It is shown that the dispersion characteristics is substantially affected by the change of the orientation angle of the principal optical axis in the substrate.     

Distributed variable-capacitance microstrip lines for microwave applications

Variable-capacitance microstrip lines are easily prepared on semiconducting substrate by use of IC-technology yielding a form of distributed nonlinear transmission line for high-frequency operation. Its cross section may be adequate to that of any varactor diode. Wave propagation determined by a very slow TM-surface mode is described by a general equivalent circuit thus characterizing the nonlinear properties of such lines. Optimum performance together with attainable configurations and possible applications are discussed.     

The Propagation of Transient Signals Along the Microstrip Using Wavelet Transformations

In this paper, we study the propagation property of the transient signals traveling along the microstrip using the method of the wavelet transform. This method has the advantages of improving the computation speed and localizing the waveform at any time and at any point along the transmission line to zoom in compared with the conventional Fourier transform. We give the dispersion of the Gaussian signal and the rectangle pulse signals on the microstrip. The results can be a reference in the study of the propagation of the ultra-high-speed and ultra-wide-band transient signals and in the design of MIC and MMIC.     

Frequency and peak discontinuities in self-pulsations of a CO2 laser with feedback

We show that self-pulsations observed in a CO₂ laser with feedback display two types of recurrent period discontinuities when control parameters are changed. Periodic self-pulsations emerge organized in wide adjacent phases in which oscillations differ by a constant number of peaks in their period. The number of peaks increases through characteristic pulse deformations of the signal that we describe in detail. The passage across the boundaries delimiting adjacent phases is abrupt and not mediated by windows of chaos. In addition, we provide an explicit criterion for locating the discontinuity boundaries between adjacent phases.     

包含非线性组件的系统级电磁效应分析方法

提出一种包含非线性组件的场线耦合分析模型,在此基础上建立了包含非线性组件的系统级电磁效应分析方法。采用基于黑箱模型的非线性散射参数对非线性组件进行建模,给出了非线性散射参数的实验提取方法。利用焊接在微带传输线上的并联反向HSMS-282C型肖特基二极管构成非线性器件,并搭建原理性实验系统测量了电磁波辐射下连接在微带线上的该非线性器件输出端口的频谱和功率。实验结果与该分析方法的计算结果相吻合,证明了该方法的有效性和可行性,为系统级电磁效应分析提供了一种有效途径。     

包含非线性组件的系统级电磁效应分析方法

提出一种包含非线性组件的场线耦合分析模型,在此基础上建立了包含非线性组件的系统级电磁效应分析方法。采用基于黑箱模型的非线性散射参数对非线性组件进行建模,给出了非线性散射参数的实验提取方法。利用焊接在微带传输线上的并联反向HSMS-282C型肖特基二极管构成非线性器件,并搭建原理性实验系统测量了电磁波辐射下连接在微带线上的该非线性器件输出端口的频谱和功率。实验结果与该分析方法的计算结果相吻合,证明了该方法的有效性和可行性,为系统级电磁效应分析提供了一种有效途径。     

Simulation and design of a bandpass filter on metasubstrates

This work presents an analysis of the microstrip bandpass filter on metamaterial substrates. The filter is composed of two ring resonators with quarter-wavelength side-coupled sections. The filter input is provided, as well as the output port, using a quarter-wavelength side-coupled microstrip line section. Simulations by finite element method have been carried out to verify the effect of the metamaterial substrate properties on the filter performance, and to compare these results to those obtained considering isotropic substrate.     

On observability of the ac Stark effect line splitting in case of beams of finite size

The small signal gain distortions in the field of a Gaussian pump beam were investigated theoretically and experimentally in a Λ-type quantum system depending on the size and power of the pump beam. The strong pump beam induces a change of refraction index of a methanol model material, depending on the frequency of the signal. It leads to a nonlinear active waveguiding effect causing distortion (narrowing and shift) of the signal line shape. In case of Stark splitting, the induced nonlinear active waveguiding effect manifests itself in the disappearance of the line split, for narrow pump beams. Collision induced frequency shift of the signal line depending on the pressure of the methanol gas was observed.     

The nonlinear study of microstrip lines containing ferrite dielectric layers

In this paper, the transient responses of microstrip containing ferrite dielectric layers are studied by using extended FD-TD method. When the microwave signal propagating along the microstrip is comparable with the applied DC magnetic field on the ferrite, the nonlinearity of ferrite medium is represented. The propagating procedure of Gaussian pulse in the microstrip are simulated. It is shown that the effects of the pulse amplitude on the transmission distortion of Gaussian pulse is pronounced.     

基于二极管Ka波段的新型可调预失真器

为了补偿不同类型功放的非线性特性,设计应用于Ka波段的可调预失真器,该电路基于三支线定向耦合器、肖特基二极管、微带线和负载电阻,产生预失真信号。通过调节肖特基二极管的偏置电压、微带线电长度及负载电阻可以提供不同的幅度和相位组合以满足不同类型的功率放大器线性化要求。仿真及实测结果表明,该预失真器在29～31 GHz频段范围内,用于行波管(TWTAs)线性化时可提供约6.5 dB的增益扩展和46的相位扩张;用于固态功率放大器(SSPAs)线性化时可提供约11 dB的增益扩展和35的相位压缩。     

Reference deconvolution. Elimination of distortions arising from reference line truncation

Reference deconvolution (G. A. Morris; J. Magn. Reson. 80, 547 (1988)) or reference lineshape adjustment (J. M. Wouters and G. A. Petersson, J. Magn. Reson. 28,81 (1977); J. M. Wouters, G. A. Petersson, W. C. Agosta, F. H. Field, W. A. Gibbons, H. Wyssbrod, and D. Cowburn, J. Magn. Reson. 28, 93 (1977)) relies on extracting the signal of a known reference material from an experimental spectrum and using a comparison between the experimental reference signal and that predicted by theory to correct instrumental contributions to the full experimental spectrum. Truncation of the reference line can produce unwanted artifacts and distortions in the final spectrum. The source of these anomalies usually lies in the dispersion-mode rather than in the absorption-mode data, as discontinuities are formed when the dispersion “wings” are truncated. These discontinuities can be reduced by a numerical extrapolation covering the lost region; this is sufficient to provide adequate results in most cases, but fails where spectra have baseline errors. A method of recreating the full dispersion signal directly from the corresponding adsorption data, based on the Hilbert transform relationship between the real and imaginary parts of a Fourier transform, is demonstrated here. This method results in the removal of truncation distortions from the deconvoluted spectrum, thus extending the range of application of the reference deconvolution technique.     

Decay of initial nonlinear Alfvén wave discontinuities in a collisionless plasma

A system of Whitham equations for the derivative nonlinear Schrödinger equation in the Riemann form was used to analyze possible types of decay of discontinuities which accompany the overturning of the simplest quasilongitudinal nonlinear Alfvén wave. A whole class of structures is found which are formed when the discontinuities decay into two simple collisionless shock waves without forming a plateau between them. Different types of decay of the initial discontinuities are considered for cases when the overturning of the Alfvén wave is modulationally stable.Checheno—Ingushk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 110–117, July, 1994.     

The new method of time-domain analysis of a planar transmission line with discontinuity

In this paper, the new technique of time-domain analysis of discontinuities in a planar transmission line is presented. In the process of time-domain analysis, the analysis model of system and the concept of transfer function are employed and the frequency-domain method of lines and the technique of the fast Fourier transform are used. The results of time-domain data and frequency-domain characteristics for the shielded microstrip with step discontinuity are given and compared with the published results of other authors.     

光纤通信用的发光管非线性P-I特性分析研究

本文综合分析了作者从制造光纤通信用的GaAs-GaAlAs发光二极管(LED)到应用这些LED制作端机系统所遇到的P-I非线性特性。文中深入地讨论了P-I非线性特性产生的原因及它对光信号失真的影响,并提出了解决办法。     

Dissipative structure in interplanetary plasma

Dissipative structures in hot interplanetary plasma are considered, which are formed due to a resonance interaction of long-wave longitudinal perturbations with nonlinear Alfven waves propagating along the magnetic field. The form of the structures is found by averaging known solutions of the derivative Schrodinger equation over the fast field phase. It is established that the dissipative structures are shaped as smooth parts of the envelope of the magnetic field, and that they are shock wave trains separated by rotational discontinuities. An equation is found which describes the structure of rotational discontinuities, and a simple step-like solution is found which fits well the obtained structures. These solutions agree with observations of rotational discontinuities in interplanetary plasma.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 104–108, August, 1991.     

Electromagnetic waves scattering by cylindrical dielectric structures: Application to microwave devices design

A method which allows us to analyze the electromagnetic scattering characteristics of multiple discontinuities in shielded dielectric waveguides is presented. There are not restrictions both geometry of the cross section and electrical parameters of the dielectrics which are assumed to be linear, inhomogeneous, isotropic and free from losses. Each discontinuity is analyzed combining a modal matching technique with a generalized telegraphist's equations formulation; in this way, we obtain its scattering matrix. By using the concept of the generalized scattering matrix of two discontinuities, the equivalent generalized scattering matrix (EGSM) of the cascaded set is calculated. Theoretical and experimental results were obtained for different dielectric structures such as dielectric posts, isolated and coupled, as well as dielectric waveguides with circular cross section connected by means of abrupt and gradual transitions. The experimental values for the scattering properties show a good agrement with the theoretical ones. This study has shown the possibility of using cylindrical dielectric structures to design microwave devices such as: resonators, power-dividers and filters.     

Numerical Study of a Microstrip Line with a Two-Layer Dielectric Substrate of Finite Width

An open microstrip line with a two-layer substrate of SiO₂ and Al₂O₃, employed in millimeter-wave range mikroelectronic devices, has been numerically studied. The dependences of the characteristic electrodynamical properties of this line upon its geometrical parameters were calculated. For computations, the method of singular integral equations in the quasistatic approximation was applied. Double complexity was introduced: with respect to time and to coordinates. This method allows taking into account even very large losses in the material of the microstrip line substrate. The computation algorithm permitted us to take into account the finite strip conductor thickness and substrate width.