Pavan Gunupudi

Passive interconnect reduction algorithm for distributed/measured networks

This paper presents an efficient algorithm for the transient simulation of multiport distributed interconnect networks in the presence of nonlinear subcircuits. The proposed multilevel multipoint model-reduction algorithm combines the merits of recently proposed Krylov-space techniques and block complex frequency-hopping to generate compact time-domain macromodels. The method overcomes the difficulty of slower transient simulation caused by redundant poles in reduced-order models obtained by Krylov-space methods. Also, it provides an efficient means to translate Krylov-space-based reduced models of distributed/measured networks with frequency-dependent descriptions into time-domain macromodels. In addition, a strategy to preserve the passivity of macromodels during multilevel reduction is presented. An important advantage of the proposed algorithm is that it can directly handle distributed stamps such as transmission lines described by Telegraphers equations, frequency-dependent parameters, full-wave, and measured subnetworks.

Passive parameterized time-domain macromodels for high-speed transmission-line networks

There is a significant need for efficient and accurate macromodels of components during the design of microwave circuits. Increased integration levels in microwave devices and higher signal speeds have produced the need to include effects previously neglected during circuit simulations. Accurate prediction of these effects involve solution of large systems of equations, the direct simulation of which is prohibitively CPU expensive. In this paper, an algorithm is proposed to form passive parametrized macromodels of large linear networks that match the characteristics of the original network in time, as well as other design parameters of the circuit. A novel feature of the algorithm is the ability to incorporate a set of design parameters within the reduced model. The size of the reduced models obtained using the proposed algorithm were less than 5% when compared to the original circuit. A speedup of an order of magnitude was observed for typical high-speed transmission-line networks. The algorithm is general and can be applied to other disciplines such as thermal analysis.

Analysis of transmission line circuits using multi-dimensional model reduction techniques

This paper presents a new technique to reduce the order of transmission line circuits simultaneously with respect to multiple parameters. The reduction is based on multi-dimensional congruence transformation. The proposed algorithm provides efficient means to estimate the response of large distributed circuits simultaneously as a function of frequency and other design parameters.

Multi-dimensional model reduction of VLSI interconnects

Recently there have been numerous publications for developing reduced-order macromodels for linear circuits. However, all these techniques perform model reduction with respect to a single parameter such as frequency. This paper presents a new technique to reduce the order of the linear system simultaneously with respect to multiple parameters. The reduction is based on multidimensional congruence transformation. The proposed algorithm provides efficient means to estimate the response of large circuits simultaneously as a function of frequency and other design parameters.

Nonlinear circuit-reduction of high-speed interconnect networks using congruent transformation techniques

A new algorithm based on Krylov subspace methods is proposed for efficient simulation of large interconnect networks with nonlinear terminations. Reduction is obtained by projecting the original system described by nonlinear differential equations into a subspace of a lower dimension. The reduced circuit can be simulated using conventional numerical integration techniques. Significant reduction in computational expense is achieved as the size of the reduced equations is much less than that of the original system. The new algorithm is potentially useful for analysis of lossy coupled transmission lines with nonlinear terminations.

Simulation of high-speed distributed interconnects using Krylov-space techniques

Accurate simulation of large interconnect networks has become a necessity to address signal integrity issues in high-speed designs. Recently, several model-reduction techniques based on Krylov-space methods have been proposed for efficient simulation of large linear networks, However, these methods treat the distributed networks in terms of their lumped representations. In order to overcome this difficulty, a new technique based on congruent transformation is presented in this paper to directly include distributed systems described by Telegraphers partial differential equations,.

Model-reduction of nonlinear circuits using Krylov-space techniques

A new algorithm based on Krylov subspace methods is proposed for model-reduction of large nonlinear circuits. Reduction is obtained by projecting the original system described by nonlinear differential equations into a subspace of a lower dimension. The reduced model can be simulated using conventional numerical integration techniques. Significant reduction in computational expense is achieved as the size of the reduced equations is much less than that of the original system.

Self-Consistent Simulation of Opto-Electronic Circuits Using a Modified Nodal Analysis Formulation

This paper addresses the need for self-consistent simulation of mixed electrical and optical circuits and systems. Drawing on the use of modified nodal analysis (MNA) techniques ubiquitous in circuit simulation, an optical node is formulated which includes the magnitude and phase of the optical signal being simulated. This node consists of two propagating complex envelopes one for the forward direction and the other for the reverse direction. Using this formulation models are developed for a variety of devices including: lasers, photodiodes, multimode fiber, and optical connectors. The formulation allows for definition of multiple optical channels at different carrier frequencies, enables quick simulation of systems with large optical delays and optical interference effects. Several numerical examples are presented in this paper to illustrate the capability of the proposed framework and where practicable the results were compared to commercial simulators. These examples include a multimode fiber optical link, an integrated array of laser sources and a feedback controlled laser source used in a optical link with modulation achieved by the use of an electro-absorption device.

Efficient sensitivity analysis of transmission-line networks using model reduction techniques

An analysis method, based on congruent transformation and model reduction, is described for evaluation of frequency and time domain sensitivity of networks which include lossy coupled transmission lines. The sensitivity can be calculated with respect to network components and parameters of transmission lines. The proposed algorithm provides a significant decrease in computational expense for sensitivity analysis.

Efficient sensitivity analysis of transmission-line networks using model-reduction techniques

An efficient algorithm, based on congruent transformation and model reduction, is proposed for evaluation of frequency- and time-domain sensitivity of large linear networks containing lossy coupled transmission lines. The sensitivity of the voltage and current waveforms can be calculated with respect to lumped components and parameters of transmission lines. The algorithm is based on projecting the adjoint network equations on a reduced-order subspace that preserves the circuit moments. The proposed algorithm provides a significant decrease in the computational expense for sensitivity analysis.