Dispersion characteristics of optically excited coplanarstriplines: pulse propagation

The propagation of optically excited picosecond electrical pulses on coplanar striplines is analyzed. A full-wave analysis method that includes dispersion and losses over terahertz bandwidths is outlined. Results of the full-wave analysis are interpreted in terms of the underlying physical phenomena. The full-wave analysis reveals the existence of peaks in the dispersion curve of the coplanar stripline. These are interpreted in terms of the onset and coupling of the substrate modes to the transmission line mode. Results of the full-wave analysis are in good agreement with those obtained by established theory. Pulse propagation is simulated using the dispersion and loss data obtained from the analysis and accounts for all the relevant mechanisms. Results of simulations are compared with previously published experimental data for normal as well as superconducting lines. It is demonstrated that the superconducting phenomena are not dominant, whereas modal dispersion and substrate losses dominate the evolution of the output pulse and must be included for accurate modeling of pulse propagation on coplanar striplines     

Full-wave simulation of electromagnetic coupling effects in RF and mixed-signal ICs using a time-domain finite-element method

This paper describes the computer simulation and modeling of distributed electromagnetic coupling effects in analog and mixed-signal integrated circuits. Distributed electromagnetic coupling effects include magnetic coupling of adjacent interconnects and/or planar spiral inductors, substrate coupling due to stray electric currents in a conductive substrate, and full-wave electromagnetic radiation. These coupling mechanisms are inclusively simulated by solving the full-wave Maxwell's equations using a three-dimensional (3-D) time-domain finite-element method. This simulation approach is quite general and can be used for circuit layouts that include isolation wells, guard rings, and 3-D metallic structures. A state-variable behavioral modeling procedure is used to construct simple linear models that mimic the distributed electromagnetic effects. These state-variable models can easily be incorporated into a VHDL-AMS simulation providing a means to include distributed electromagnetic effects into a circuit simulation.     

Circular-pad via model based on cavity field analysis

An equivalent circuit model of a circular-pad grounding via is proposed based on cavity modal analysis. The modes of the via are derived analytically. Each mode is represented by an equivalent circuit taking into account ohmic losses, as well as losses due to spatial and surface wave radiation. It is shown that the degradation of grounding via characteristics at high frequencies is caused by the multimode effects and radiation. The accuracy of the proposed semi-analytical via model is comparable with that of full-wave analysis up to 75 GHz. It is fast and is easily incorporated in high-frequency circuit simulators.     

Terahertz attenuation and dispersion characteristics of coplanartransmission lines

Experimental verification of analytic formulas for the dispersion and the attenuation of electrical transient signals propagating on coplanar transmission lines is presented. The verification is done in the frequency domain over a terahertz range although the experiments are in the time domain. The analytic formulas are obtained from fits to the full-wave analysis results. It is quantitatively verified that the full-wave steady-state solutions can be directly applied to the transient time-domain propagation experiments. Subpicosecond electrical pulses and an external electrooptic sampling technique are used to obtain the time-domain propagation data. From the Fourier transforms of the time-domain data both the attenuation and the phase information as a function of frequency are extracted. The dispersion and the attenuation characteristics are investigated for both coplanar waveguide and coplanar strip transmission lines. The investigation is carried out on both semiinsulating semiconductor and dielectric substrate materials. No observable losses caused by the semiconductor material are indicated     

Accurate and efficient computation of dielectric losses inmulti-level, multi-conductor microstrip for CAD applications

An approach to accurate and efficient computation of dielectric losses in complex microstrip structures is proposed. It can be used in lieu of lossy, full-wave solutions to provide accurate and efficient data for the CAD of multilevel, multiconductor MIC and MMIC structures. Results that are as accurate as lossy full-wave techniques over a wide range of frequencies, including the dispersive region, are obtained. In addition to providing accurate results, the method is up to three times faster, depending on the number and type of substrates or superstrates. Results for various multiconductor, multilevel structures that compare well with the lossy, full-wave approach and require significantly less computer time to compute are shown     

Design rule development for microwave flip-chip applications

This paper presents a novel experimental approach for the analysis of factors to be considered when designing a flip-chip package. It includes the design of an experiment and statistical analysis of the outputs and uses both test-structure measurements and full-wave simulation techniques in the 1-35-GHz frequency range. The most significant factors are found to be, from the most to least important, the length of the area where the device and substrate overlap (referred to as conductor overlap), the bump diameter, and the width of the coplanar-waveguide transmission-line launch. These results are valid for conductor overlaps between 300-500 μm. For a lower value (120 μm), the significance level of the overlap decreases and the bump height also becomes significant. Test-structure measurements in the 120-200-μm overlap range validate this result and demonstrate the decrease in the significance level. The substrate thickness in the 10-25-mil interval is found to be statistically insignificant, therefore, it can be eliminated from further analysis. This approach provides a foundation for development of a set of design rules for RF and microwave flip-chip similar to RF integrated-circuit design rules     

Full-wave spectral-domain analysis of compensation of microstripdiscontinuities using triangular subdomain functions

A full-wave spectral-domain analysis of compensation for a variety of microstrip discontinuities, including open-ends, bounds and T-junctions, is presented. To properly model the discontinuities with miters as well as 90° corners, vector-valued triangular subdomain functions are used as both expansion and testing functions in the moment method procedure. Special consideration is given to the numerical treatment of the reaction integral between two triangular subdomains such that rather complicated geometrical configurations can be handled very efficiently. Comparison of some numerical results with available experimental data shows excellent agreement. The losses due to radiation and surface waves for some discontinuities are also included     

Characterization of MIS structure coplanar transmission lines forinvestigation of signal propagation in integrated circuits

A full-wave analysis of metal-insulator-semiconductor (MIS) structure micron coplanar transmission lines on doped semiconductor substrates is carried out using a finite-difference time-domain approach. Metal conductor loss is taken into account in the analysis. Line parameters and electromagnetic field distributions are calculated over a wide frequency range involving slow-wave and dielectric quasi-transverse-electromagnetic mode limits. Measurements of these line parameters, varying substrate resistivity from 1 to 1000 Ω-cm, in the frequency range up to 40 GHz are also presented, and these agree with the analysis quite well. On the basis of these results, an equivalent circuit line model is induced and some considerations on the relationship between line structure and properties made     

The Method of Lines for the Analysis of Microstrip Lines on the Finite Width Substrate

A full-wave analysis of the electrical characteristics of the microstrip lines on the finite width substrate is presented. The substrate layer of the microstrip line must be treated as an inhomogeneous layer. The effects of the substrate width to the characteristics of the microstrip line are now exactly investigated, which are often avoided by other methods. The results are in good agreement with those published results.     

Modelling finite-size PCBs for radiated EMI analysis

Typical printed circuit boards (PCBs) in the EMI regulated frequency range 30-1000 MHz are electrically finite-sized. The conventional full-wave method is not suitable for modelling finite-sized PCBs because of the assumption of infinite ground and substrate. The authors present a full-wave moment method approach for computing radiated electromagnetic interference produced by realistic finite-size PCBs. Numerical agreement with another approach is demonstrated     

Design and simulation of integrated inductors on porous silicon in CMOS-compatible processes

We present a comprehensive approach of designing on-chip inductors using a CMOS-compatible technology on a porous silicon substrate. On-chip inductors realized on standard CMOS technology on bulk silicon suffer from mediocre Q-factor values partly because of the loss created by the Si substrate at higher frequencies, in addition to the metal losses. We examine the alternative of using porous Si as a thick layer isolating the Si substrate from the metallization in an otherwise standard CMOS technology. We present theoretical designs produced with full-wave Method-of-Moments simulations, verified by measurements in standard 0.18 μm CMOS technology using Al metallization. When porous Si is introduced in that technology, the same inductor metallization produced Q-factor enhancements of the order of 50%, compared to the same inductor on bulk crystalline silicon. We also produce optimized single-ended inductor designs using Cu on porous Si, in a 0.13 μm-compatible CMOS technology. The resulting Q-factors are enhanced by a factor of 2 and reach values of 30 or more in the 2–3 GHz frequency range. Even higher quality factors can be obtained in this technology when differential designs are used.     

The RCS of a microstrip antenna on an in-plane biased ferritesubstrate

The numerical solutions for the RCS of a microstrip patch on an in-plane biased ferrite substrate are presented. The peaks in the RCS can be moved with respect to frequency by changing the magnetic bias field. We consider a monostatic RCS with various incident angles and examine all four elements of the cross-section matrix. For the case of an unmagnetized ferrite substrate the cross-polarized RCS components are zero. When the ferrite is magnetized, the cross-polarized RCS components become as significant as do the copolarized RCS components. It is also shown that a loaded patch has the effect of significantly reducing RCS at resonances. The analysis used is based on a full-wave moment method with the exact spectral-domain Green's function     

A generalized method for distinguishing between radiation andsurface-wave losses in microstrip discontinuities

A generalized method for calculating both radiation and surface-wave losses is developed for microstrip discontinuities. The losses are determined by a rigorous Poynting vector analysis where the current distribution over the microstrip discontinuities is a result of a full-wave moment method solution. The power loss mechanism of such microstrip discontinuities as open-end, right-angle-bend, gap and stub lines, EMC lines, and rectangular patches are investigated. A self-consistency check of the result based on power conservation is performed to confirm the numerical results. It is found that, above a certain frequency, the surface-wave loss becomes more important than the radiation loss     

宽带硅衬底RF片上螺旋电感物理模型

针对高损耗硅衬底,源自部分元等效电路方法考虑了趋肤效应和邻近效应对螺旋电感中串联电感L_s、串联电阻R_s频率特性的制约,并基于全耦合变压器模型计入了复杂的衬底涡流损耗,从而建立了一种新的片上螺旋电感物理模型.通过与全波分析方法对比,验证了在20GHz范围内由该模型导出的等效电感L_eff、等效电阻R_eff和Q值误差仅在7%以内.该模型可望用于硅基射频集成电路中电感进一步的理论探讨和优化设计.     

Frequency-dependent mutual resistance and inductance formulas for coupled IC interconnects on an Si-SiO2 substrate

A highly accurate closed-form approximation of frequency-dependent mutual impedance per unit length of a lossy silicon substrate coplanar-strip IC interconnects is developed. The derivation is based on a quasi-stationary full-wave analysis and Fourier integral transformation. The derivation shows the mathematical approximations which are needed in obtaining the desired expressions. As a result, for the first time, we present a new simple, yet surprisingly accurate closed-form expression which yield accurate estimates of frequency-dependent mutual resistance and inductance per unit length of coupled interconnects for a wide range of geometrical and technological parameters. The developed formulas describe the mutual line impedance behaviour over the whole frequency range ( i.e. also in the transition region between the skin effect, slow wave, and dielectric quasi-TEM modes). The results have been compared with the reported data obtained by the modified quasi-static spectral domain approach and new CAD-oriented equivalent-circuit model procedure.     

A time-domain full-wave extraction method of frequency-dependentequivalent circuit parameters of multiconductor interconnection lines

A time-domain full-wave method for the extraction of frequency-dependent equivalent circuit parameters of multiconductor interconnection lines is presented in this paper. The circuit parameters extracted by this method can be inserted into circuit simulation software to investigate time-domain responses of a high-speed IC system with multiconductor interconnects. Because the definitions of the voltage and the current are not unique in full-wave analysis, transformation among circuit parameters according to different definitions of the voltage and current is also presented. The method is based on the finite-difference time-domain (FDTD) method, and the reliability of this method is illustrated by its application to representative problems     

Hankel transform domain analysis of open circular microstrip radiating structures

A full-wave analysis of a circular disk conductor printed on a dielectric substrate backed by a ground plane is presented. The method is based on the Galerkin's method applied in the Hankel transform domain and is numerically quite efficient. Several numerical examples are compared with available experimental data. The agreement is found to be quite good and the validity of the present method is confirmed.     

A WH/GSMT-based full-wave analysis for planar transmission linesembedded in multilayered dielectric substrates

A new full-wave analysis method, referred to as the WH/GSMT, is developed to solve multilayered planar transmission line problems. First, the scattering of an obliquely incident parallel plate mode (PPM) by a PEC half plane embedded in a multilayered isotropic dielectric substrate within a PEC parallel plate region is analyzed via the Wiener-Hopf (WH) technique. The solution is then incorporated into the generalized scattering matrix technique (GSMT) to find the (complex) propagation constant and characteristic impedance of the planar transmission lines. The lateral power leakage is taken into account rigorously in the WH/GSMT. Numerical results including the microstrip line, conductor-backed slotline, coupled microstrip lines, and antipodal finlines are presented along with a discussion of the advantages/disadvantages of this method     

Dispersion characteristics of cylindrical coplanar waveguides

A full-wave analysis of the coplanar waveguide (CPW) printed on a cylindrical substrate is presented, and the dispersion characteristics of the cylindrical CPW are studied. Numerical results of the effective relative permittivity are calculated using a Galerkin's moment-method calculation. Experiment is also conducted, and the measured data are in good agreement with the theory