Empirical Relations for Capacitive and Inductive Coupling Coefficients of Coupled Microstrip Lines

Empirical relations for inductive and capacitive coupling coefficients are proposed. The functional relationships are based on the physical mechanism of coupling in microstrip lines. Values of coupling coefficients computed from even- and odd-mode impedances and phase velocities, available in the literature, are compared with those computed from the proposed relations. Microstrip couplers have been designed on the basis of coupling coefficients to meet the desired coupling and isolation.     

Design of grating-assisted waveguide couplers with weightedcoupling

The design of grating-assisted, channel waveguide codirectional couplers is demonstrated using the Gel'fand-Levitan-Marchenko inverse scattering method. Weighted coupling coefficients are computed from rational expression for the desired wavelength response. Approximate formulas that relate the waveguide and grating geometries to the computed coupling coefficients are derived. The technique is illustrated by designing a directional coupler with a third-order Butterworth filter characteristic and a 130 Å full-width-half-maximum bandwidth     

A Complete Solution of the Inductive Iris with TE/sub k0/ Incidence in Rectangular Waveguide

A TE/sub k0/ wave incident on an inductive metal iris in a rectangular waveguide excites a reflected and a transmitted wave in the TE/sub k0/ mode. The reflection and transmission coefficients describing these waves are computed. In addition to the incident mode, a number of other modes are excited by the discontinuity. The amount of coupIing to these other modes, given by coupling coefficients, is determined using the variational technique. The method developed makes it possible to find the coupling to any desired mode without first finding the coupling to any other mode or group of modes. The analysis shows under what conditions certain modes can be suppressed or eliminated. The method should be applicable to other problems of interest where modes other than the incident one are excited. Since the reflection, transmission, and coupling coefficients are known, the total field at any point in the waveguide can be computed. As an example, the total field at the discontinuity when the TE/sub 10/ mode is incident is calculated. The result closely resembles the expected result (of zero electric field over the metal iris).     

Exact calculations of scattering parameters of a step slot width discontinuity in a unilateral fin-line

The dominant and the first four higher-order modes in a unilateral fin-line are accurately described from a thorough spectral-domain approach. Then, coupling coefficients between eigenmodes at a step slot width discontinuity to be used in the generalised scattering matrix formulation are directly computed in the spectral domain. Scattering parameters of the dominant mode in the Ka band are presented.     

Normal-Mode Parameters of Microstrip Coupled Lines of Unequal Width (Short Paper)

Empirical relations for the capacitive and inductive coupling coefficients have been used to compute normal-mode parameters of non-identical microstrip coupled lines. The computed values of mode velocities and mode impedances are compared with available results from the literature and experimental results on nonidentical microstrip couplers to test the applicability of the empirical relations.     

Theoretical of and Experimental Investigation Finline Discontinuities

The dominant and the first-five higher order modes in a unilateral finline are precisely described from a thorough spectral-domain approach. Then, using the modal analysis, coupling coefficients between eigenmodes at a discontinuity that have to be introduced into the scattering matrix formulation are directly computed in the spectral-domain, and, consequently, the equivalent circuit parameters of the discontinuity are determined. Finafly, finline discontinuities often used for impedance transformation are investigated and a good agreement between theoretical and experimental results is reported.     

Accurate Analysis of Tapered Planar Transmission Lines for Microwave Integrated Circuits

A broad class of nonuniform transmission lines is analyzed through the method of coupled modes accompanied by the spectral domain solution of uniform lines. This combination offers efficient computation of the coupling coefficients. Small coupling allows the rigorous field theory of the spectral domain approach to give explicitly the scattering matrix of the taper. Several structures, including microstrip to coplanar waveguide taper and waveguide to fin-line taper, are successfully analyzed. The computed values of reflection coefficients are compared with the values derived by a simple impedance method and with the measured values. Results from the experimentally investigated tapers show that the theory is in good agreement.     

Coupling parameters for a side-coupled ring resonator and amicrostrip line

A ring resonator side coupled to a microstrip line shows two close but distinct resonance peaks. These are identified as due to even-mode (magnetic field) and odd-mode (electric field) coupling. Equivalent circuit models for both cases have been proposed and coupling parameters are calculated using piecewise, coupled-line approximations. The calculated coupling coefficients for the two cases are compared with the experimentally-measured coupling coefficients and show very good agreement with the models used     

Mutual coupling in arrays of coaxial waveguides and horns

A solution is presented for the mutual coupling between the modes of different-sized circular coaxial aperture arrays, which are used as direct radiators and feed antennas. This solution is expressed in terms of integral transforms and the mutual admittances for the cross coupling between all three mode types, TE, TM, and TEM, are obtained. The accuracy of this new integral formulation is demonstrated by comparing computed results with measured data for a three-element test array. Excellent agreement is obtained between theory and experiment for both coupling coefficients and radiation patterns. Results are also presented for a coaxial feed array for the Lovell radio telescope.     

Singularity expansion method analysis of regular polygonal loops

The singularity expansion method parameters (natural frequencies, natural modes, and coupling coefficients) for regular planar polygonal loops (equilateral triangle, square, regular pentagon, and regular hexagon) are computed and compared to those determined for the regular 60-gon (pseudo-circular) loop. Common characteristics of these geometries are compared and contrasted with respect to their use as radiating antenna structures or scatterers. The approach results in new insights for these canonical loop structures     

失调腔之间的模式耦合与转换

本文理论分析了谐振腔之间调节不好,它们的光轴之间同时存在平行移位和倾斜时,光腔之间的模式耦合和转换.用相对失调参数的函数形式给出了基模到低阶横模之间的模式耦合系数.结果发现,当腔之间失调存在时,厄米-高斯光束奇偶模之间存在耦合;当腔失配和失调满足一定条件时,基模到低阶横模之间的功率耦台系数达到极大值.     

Characteristics of Coupled Microstrip Transmission Lines-I: Coupled-Mode Formulation of Inhomogeneous Lines

This paper consists of two parts. In Part I, coupled-mode theory is employed to determine the effects of reflection at the various ports and unequal inductive and capacitive coupling coefficients on the coupling and directivity of two coupled lines. Since couplers utilizing microstrip lines generally have unequal inductive and capacitive coupling coefficients, the results presented here should be useful in explaining the behavior of microstrip coupled lines. It is shown how the difference in the coupling coefficients leads to finite directivity and, under certain conditions, to "codirectional" instead of "contradirectional coupling." In Part II, the coupling coefficients and other parameters of various microstrip-line geometries are presented. Using these parameters in the results obtained here leads to an improved understanding of and design criteria for coupled microstrip lines.     

Prediction of delays induced by in-band RFI in CMOS inverters

Delays induced by radio frequency interference (RFI) in CMOS inverters are measured under radiated and capacitively coupled interference. Experimental and theoretical investigations of the effects of the RFI coupling mode (capacitive versus inductive) on the amount of induced delay are presented and a worst-case coupling mode is identified. A formula to predict delays caused by in-band low-level RFI in CMOS inverters is introduced. This formula uses experimentally determined parameters which are dependent on the coupling mode. The change in delay is computed as a function of the induced voltage disturbance, which in turn can be computed from the incident field using linear frequency-domain analysis. The formula accounts for the dependence of the induced delay on the phase and amplitude of the RFI signal as well as on the slew rate of the logic transitions. A delay growth phenomenon in a string of inverters is identified and characterized. A correction to the delay prediction formula is proposed in order to take this growth into account in worst-case predictions     

Coupling coefficients of step-impedance resonators in stripeline band-pass filters of array type

There are researched specificities of electromagnetic coupling coefficients at main and higher resonance frequencies between step-impedance resonators, fabricated from symmetric stripe transmission lines with open ends. It is shown, modification of step resonators parameters can result in modification of the coupling coefficient at main resonance frequency in wide range, that allows to realize band-pass filters of array type. It is stated in case of several values of parameters of stripe resonators their coupling coefficients values at frequencies higher than main one are zero. It is proposed a new method of expansion of suppressed frequency band of pass-band filters of array type, which is based on suppression of the first parasitic pass band due to zero coupling coefficient.     

Mode-coupling analysis of depolarization effects in a multimodeoptical fiber

A method of analyzing depolarization effects in a multimode fiber has been developed. A new expression for degree of polarization (DOP) in terms of fiber parameters, incident polarization condition, and mode coupling coefficients has been derived. The numerical results for DOP for various fiber lengths, coupling coefficients, and normalized angular spacings `q' have been obtained     

Computation of bipolar transistor base parameters for general distribution of impurities in base

A procedure is suggested by which dc and ac base gain parameters can be computed for general impurity distributions in the base. The procedure consists of solving the current equation as series in the recombination time (1/τ). The series expansion coefficients are computed for a Gaussian distribution up to first order, along with the resulting base alpha transport factor and the transit time. Mobility variation with impurity concentration is also taken into account. Explicit expressions for cutoff frequencies and excess phase shift (omega_{T}, omega_{alpha}, omega_{beta}, m) are developed using the coefficients of the series expansion up to the second order. Computation of these parameters for the case of an exponential distribution, with and without assumption of diffusion coefficient variation, results in new expressions and values.     

Effect of Surface Profile Length on the Backscattering Coefficients of Bare Surfaces

The root mean square (rms) height s and autocorrelation length l are commonly used as the surface roughness input parameters to surface scattering models. Whereas it is well known that the surface roughness parameters of a natural soil surface are underestimated with a short surface profile, it is not clear how much the underestimated surface parameters affect the backscattering coefficients of the surface for various incidence angles and polarizations. In this paper, the backscattering coefficients of simulated and measured surface profiles are computed using the integral equation method and analyzed to answer this question. A 4000lmacr-long rough surface is generated numerically, where lmacr is the true correlation length of the surface, and the backscattering coefficients of the surface are computed and analyzed for various conditions. The rms error of the backscattering coefficient at a medium range of incidence angles is less than 1.5 dB for vv-polarization and 0.5 dB for hh-polarization if the profile length is larger than 5lmacr for a surface with ks=1.0, kl=10.0, and epsiv _r=(10.0,2.0). Similar results are obtained from numerous simulations with various roughness conditions and various wavelengths. It is also shown that the rms error of the backscattering coefficients between 5- and 1-m-long measured surface profiles is 1.7 dB for vv-polarization and 0.5 dB for hh-polarization at a medium range of incidence angle (15deglesthetasles70deg), whereas the surface roughness parameters are significantly reduced from 2.4 to 1.5 cm for the rms height s and from 35.1 to 10.0 cm for the autocorrelation length l     

异构耦合谐振器耦合系数的提取

为寻找异构耦合谐振器耦合系数提取电路的设计原则,本文将提取同构耦合谐振器耦合系数的电路模型一般化,在电路仿真软件中分析其各项参数变化对特征频率的影响方式,从中总结异构耦合谐振器耦合系数提取电路的设计原则与注意要点。设计了一对特定异构耦合谐振器耦合系数的提取电路,通过其提取的耦合系数在一个双频带带通滤波器设计中发挥了重要...     

通带耦合特性独立可调的双频微带滤波器设计

引入一种新型双通带滤波器耦合结构,采用微带线型SIR结构分别设计了切比雪夫型和准椭圆函数型2.4GHz/5.2GHz双频带通滤波器。运用电磁数值分析软件讨论了结构参数对双通带滤波器耦合性能的影响,以及准椭圆函数型滤波器耦合结构参数对其传输零点位置的影响,并在文中给出其变化规律。基于该耦合结构的新型双频带滤波器,设计自由度更高,两个通带所需耦合系数可以独立调节。根据以上结构参数所制备的样品,其性能测试结果与仿真结果吻合良好。     

Surface acoustic waves and SAW materials

Material parameters necessary for optimum design of surface-acoustic-wave (SAW) devices are reviewed. Velocity, coupling coefficient, power flow angle, temperature coefficients, propagation loss (including air loading, diffraction, and beam steering), and equivalent circuit parameters are considered. A brief introduction to the nature of surface waves is followed by sufficient theoretical information to allow full understanding and derivation of the properties and parameters cited above. A convenient tabular summary of important SAW material properties is included.