Analysis of high-speed interconnects using efficient multipointPade approximation

An efficient method is presented for analysis of large interconnect circuits including lossy coupled transmission lines. Based on multipoint Pade approximations and a new expansion point search algorithm, the method can obtain single close-form frequency-domain and transient solutions of the interconnect problem with a minimum of frequency expansion points     

A coupled efficient and systematic full-wave time-domain macromodeling and circuit Simulation method for signal integrity analysis of high-speed interconnects

This paper presents an accurate and systematic approach for analysis of the signal integrity of the high-speed interconnects, which couples the full-wave finite difference time domain (FDTD) method with scattering (S) parameter based macromodeling by using rational function approximation and the circuit simulator. Firstly, the full-wave FDTD method is applied to characterize the interconnect subsystems, which is dedicated to extract the S parameters of the subnetwork consisting of interconnects with fairly complex geometry. Once the frequency-domain discrete data of the S parameters of the interconnect subnetwork is constructed, the rational function approximation is carried out to establish the macromodel of the interconnect subnetwork by employing the vector fitting method, which provides a more robust and accurate solution for the overall problem. Finally, the analysis of the signal integrity of the hybrid circuit can be fulfilled by using the S parameters based macromodel synthesis and simulation program with integrated circuits emphasis (SPICE) circuit simulator. Numerical experiments demonstrate that the proposed approach is accurate and efficient to address the hybrid electromagnetic (interconnect part) and circuit problems, in which the electromagnetic field effects are fully considered and the strength of SPICE circuit simulator is also exploited.     

An integrated testbed for wireless multimedia computing

A testbed has been constructed to evaluate node architectures that support multimedia applications and services across a wireless network. Using this testbed, a low bitrate subband video compression algorithm has been prototyped in a field programmable gate array (FPGA) and evaluated for video networking across bandwidth-limited RF channels. A radio interface has been prototyped in an FPGA and a common applications programming interface (API) has been developed to allow experimentation with multiple radios. This testbed has been used to evaluate node performance under two different wireless applications: 1) simultaneous video and data networking (VTALK) and 2) TCP/IP utilities such as FTP and telnet. Based on this evaluation, the design of a battery-operated high throughput wireless multimedia node is presented.     

Efficient method for computing double matrix products

We introduce an efficient method for computing matrix products of the formY=AXB, whereA andB are sparse and constant. We analyze the complexity of the method, develop quantitative criteria for determining when it can be used effectively, and demonstrate its use in a Kalman filter.Part of this work was supported by the GE Aerospace Business Group while the authors were in residence at the GE Research and Development Center, Schenectady, New York 12301, USA.     

An efficient method for computing cell loss probability for heterogeneous bursty traffic in ATM networks

In this paper, we present an approximation for the probability of cell loss of heterogeneous bursty traffic in broadband integrated packet networks based on the asynchronous transfer mode. The sources considered here alternate between active and silent periods and are characterized by their peak and average transmission rates. The cell loss probability is obtained by considering only the number of active sources at a given time and computing the amount of traffic that exceeds the link capacity. Since the amount of buffered excess traffic is not considered in this computation, this approximation is actually an upper bound of the cell loss probability. The numerical efficiency of this bound enables it to be used as a measure based on which robust and simple resource allocation strategies can be developed for bursty sources. Comparison of this bound with the simulation results has shown that the bound is close to the actual loss probabilities especially for large burst lengths and high utilizations.     

A layout-based schematic method for very high-speed CMOS celldesign

In very high-speed CMOS cell design, the result of schematic simulation is inaccurate because of missing parasitic components, such as diodes and parasitic capacitances. Designer cannot pass enough information to the simulator by conventional transistor symbols, therefore, simulation error occurs. In this paper, we address a layout-based schematic (LBS) method for high-speed CMOS cell design. In this method, we introduce several types of MOS transistors and estimate parasitic wire capacitances by using layout knowledge. The simulation results show that the difference between LBS and real layout is much smaller, less than 3% in rise time, compared to in the worst case of up to 65% in the original schematic. This method can be applied to both digital and analog circuits and it is helpful for layout automation. Time and cost will be reduced in high-speed circuit design     

Inter-CNT capacitance in mixed CNT bundle interconnects for VLSI circuits

This article presents a realistic inter-carbon nanotube (CNT) electrostatic coupling capacitance and tunnelling conductance model for a mixed CNT bundle. The change of potential across such a bundle necessitates the need to consider the inter-CNT capacitance in the equivalent circuit of CNT interconnects for very large scale integration circuits. The equivalent transmission line circuit model of a unit bundle containing one single-walled CNT (SWCNT) and one multi-walled CNT (MWCNT) has been shown. This new model is then used to calculate the delay induced by the inter-CNT capacitance and tunnelling conductance, which predicts the relative positioning of MW/SWCNTs in mixed CNT bundle.     

An efficient communication protocol for high-speed packet-switchedmultichannel networks

A media-access protocol for high-speed packet-switched multichannel networks that are based on a broadcast topology, such as optical passive star networks using wavelength-division multiple access, is described. The protocol supports connection-oriented traffic with or without bandwidth reservation, as well as datagram traffic to integrate transport-layer functions with the media-access layer. It uses the bandwidth efficiently while keeping the processing requirements low by requiring stations to compute their transmission and reception schedules only at the start and end of each connection. Analysis results show that low blocking probabilities for connections and high network throughput can be achieved     

A simple but efficient analog computer for simulation of high-speed integrated circuits

An analog computer is described which performs transient simulation of nonsaturated transistor circuits with little expense of time. The computer contains models of bipolar transistors and Schottky-barrier diodes as well as variable capacitors and resistors, all realized in plug-in technique. The parameters of the semiconductor devices are directly and continuously adjustable. Therefore, no special knowledge is required to operate the computer. For the display, a dual-trace oscilloscope with low bandwidth is sufficient because the analog time range lies above 0.1 ms. Compared with the digital computer simulation, this analog method has the advantages of lower costs and less simulation time, the latter allowing fast interaction between designer and computer. The good accuracy of the described simulation method is demonstrated by comparing the simulated and the directly measured transient response of an integrated subnanosecond E/SUP 2/CL gate. Also it is shown how the delay time of this gate depends on the transistor parameters.     

Analysis of high-speed interconnects in the presence ofelectromagnetic interference

This paper describes an efficient algorithm based on moment-matching techniques for simulation of high-speed circuits in the presence of electromagnetic interference (EMI). The proposed method is based on the recently developed complex frequency hopping (CFH) technique for interconnect analysis. The new technique is useful for susceptibility analysis and is two to three orders of magnitude faster than conventional simulation techniques. In addition, it can be extended to the analysis of interconnects with frequency-dependent parameters and nonlinear terminations     

An efficient algorithm for computing global reliability of anetwork

Global reliability of a network is defined and then evaluated using spanning trees of the network graph. An algorithm for generating spanning trees (termed, appended spanning trees) that are mutually disjoint is proposed. Each appended spanning tree represents a probability term in the final global reliability expression. The algorithm gives the global reliability of a network directly. It is illustrated with an example. The algorithm is fast, requires very little memory, is adaptable to multiprocessors, and can be terminated at an appropriate stage for an approximate value of global reliability     

An efficient method for calculating bounces in the irregular power/ground plane structure with holes in high-speed PCBs

The eigenmode expansion method (EEM) is a convenient technique for characterizing a power/ground (P/G) plane pair structure. The requirements of the plane pair's shape, however, and a double-infinite series in its equation limit its applications. To overcome its disadvantages and extend its applications, this paper proposes some techniques for the EEM and makes some modifications to it. First, by employing the newly presented inverted composition method and the segmentation method, the improved EEM can be used to characterize a holey P/G plane pair with irregular shapes. Second, by employing a trigonometric Fourier series and a particular Pade approximation method-the /spl eta/-algorithm, the double-infinite series in EEM can be changed into a single one and its convergence can be accelerated apparently so that the computation efficiency of the EEM is greatly improved. An example is considered to compare the numerical data of the new EEM with corresponding measurement results, thus demonstrating the good accuracy. The computation time of the proposed method is compared with that of the finite-element method (FEM), which shows that the new method has higher efficiency.     

An analysis method for high-speed circuit systems

A new method for analyzing high-speed circuit systems is presented. The method adds transmission line end currents to the circuit variables of the classical modified nodal approach. Then the matrix equation describing high-speed circuit system can be formulated directly and analyzed conveniently for its normative form. A time-domain analysis method for transmission lines is also introduced. The two methods are combined together to efficiently analyze high-speed circuit systems having general transmission lines. Numerical experiment is presented and the results are compared with that calculated by Hspice.     

The modeling of resistive interconnects for integrated circuits

Techniques for analyzing the signal transmission properties of long resistive interconnects on integrated circuits are presented. Because accurate measurements of propagation characteristics on chip are difficult to make, RC transmission line theory is used to establish exact performance. The results of various simulations are compared to this theoretical performance. Guidance is provided for selecting the number of elements needed to accurately simulate performance under various conditions.     

A simple formula for the estimation of the capacitance of two-dimensional interconnects in VLSI circuits

A simple formula for the estimation of the capacitance of a single interconnection line in VLSI circuits is presented. It is shown that the approximation agrees favorably with the results obtained from much more costly two-dimensional simulations. The approximation is also simpler and more accurate than other approximations that have been proposed.     

Physically consistent transmission line models for high-speed interconnects in lossy dielectrics

The development of a physically consistent multiconductor transmission line model for high-speed interconnects in lossy, dispersive dielectrics is presented. Based on this model, a methodology is presented which constructs SPICE-compatible equivalent circuits that take into account dielectric loss and dispersion. Simulations using wideband measurement data of alumina demonstrate the effect of the Debye based permittivity model.     

An efficient method for computing optical waveguides with discontinuous refractive index profiles using spectral collocation method with domain decomposition

An accurate and efficient solution method using spectral collocation method with domain decomposition is proposed for computing optical waveguides with discontinuous refractive index profiles. The use of domain decomposition divides the usual single domain into a few subdomains at the interfaces of discontinuous refractive index profiles. Each subdomain can be expanded by a suitable set of orthogonal basis functions and patched at these interfaces by matching the physical boundary conditions. In addition, a new technique incorporating the effective index method and the Wentzel-Kramers-Brillouin method for the a-priori determination of the scaling factor in Hermite-Gauss or Laguerre-Gauss basis functions is introduced to considerably save computational time without experimenting with it. This method shares the same desirable property of the spectral collocation method of providing a fast and accurate solution but avoids the oscillatory solutions and improves the poor convergence problem of the simple spectral collocation method with single domain where regions of discontinuous refractive index profiles exist. Applications to several two- and three-dimensional waveguide structures having exact or accurate approximate solutions are given to test the accuracy and efficiency; all the results are found to be in excellent agreement.     

An integral equation method for the evaluation of conductor anddielectric losses in high-frequency interconnects

An integral equation method is developed to solve for the complex propagation constant in multilayer planar structures with an arbitrary number of strip conductors on different levels. Both dielectric losses in the substrate layers and conductor losses in the strips and ground plane are considered. The Green's function included in the integral equation is derived by using a generalized impedance boundary formulation. The microstrip ohmic losses are evaluated by using an equivalent frequency-dependent impedance surface which is derived by solving for the fields inside the conductors. This impedance surface replaces the conducting strips and takes into account the thickness and skin effect of the strips at high frequencies. The effects of various parameters such as frequency, thickness of the lines, and substrate surface roughness on the complex propagation constant are investigated. Results are presented for single strips, coupled lines, and two-level interconnects. Good agreement with data available in the literature is shown     

An efficient method for L-filter design

For a given or estimated noise type, the determination of optimal L-filter coefficients is computationally intensive and extremely time consuming. Thus, even though the L-filters obtained are very successful in restoring signals corrupted by non-Gaussian noise, their on-line design in real-time applications is not practical. In this paper, a new methodology for the design of L-filters is presented in which the L-filter coefficients are obtained by approximating the covariance matrix of the ordered samples through the use of Taylor expansion. The paper also presents several examples that compare the proposed approach to the classical approach. The simulations show the value of the proposed approach.