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Author

K.K. Gullapalli

Other affiliations: Synopsys
Bio: K.K. Gullapalli is an academic researcher from Motorola. The author has contributed to research in topic(s): Harmonic balance & Krylov subspace. The author has an hindex of 7, co-authored 18 publication(s) receiving 280 citation(s). Previous affiliations of K.K. Gullapalli include Synopsys.

Papers
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Journal ArticleDOI

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Kuntal Joardar1, K.K. Gullapalli1, Colin C. McAndrew1, M.E. Burnham1, A. Wild1 
TL;DR: A new MOSFET model is presented that overcomes the errors present in state-of-the-art models and comparison with measured data is presented to validate the new model.
Abstract: Problems that have continued to remain in some of the recently published MOSFET compact models are demonstrated in this paper. Of particular interest are discontinuities observed in these models at the boundary between forward and reverse mode operation. A new MOSFET model is presented that overcomes the errors present in state-of-the-art models. Comparison with measured data is also presented to validate the new model.

135 citations

Patent

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21 Aug 1995
TL;DR: In this article, a model of a graded channel transistor having at least two channel portions of differing doping concentrations was generated by using a standard transistor model (100, 120) with junction voltages (64) resulting between the transistor models.
Abstract: The present invention generates a model of a graded channel transistor having at least two channel portions of differing doping concentrations. The present invention assumes a uniform doping concentration of each channel portion. Each of the channel portions is modeled using a standard transistor model (100, 120) with junction voltages (64) resulting between the transistor models. The junction voltages (64) are determined to be at a level such that the channel currents of the transistor models (60, 62) are equal. Once the junction voltages (64) are determined, the parameters of the transistor models (60, 62) are determined. Once the transistor models (60, 62) are determined, the models are combined to produce a composite transistor model (70) for the transistor using standard circuit reduction techniques. The composite model produced is scalable with respect to geometry, is continuous, and is differentiable. Steps are also disclosed for manufacturing integrated circuits using the modeling techniques of the present invention.

25 citations

Proceedings ArticleDOI

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08 Jun 1997
TL;DR: An experimental investigation of GMRES and QMR, two leading Krylov subspace methods as applied to the HB problem, and the problem of coordinating the linear solver's accuracy with the error at the nonlinear level is discussed.
Abstract: Harmonic balance (HB) is a steady-state simulation technique of primary interest for RF and microwave circuits. Krylov subspace methods promise efficient solution of the large linear systems that arise in HB simulators. This paper deals with an experimental investigation of GMRES and QMR, two leading Krylov subspace methods as applied to the HB problem. The problem of coordinating the linear solver's accuracy with the error at the nonlinear level is also discussed.

24 citations

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TL;DR: In this article, a new technique based on a continuation method for oscillator analysis using harmonic balance is presented, and the main contribution is a robust and efficient continuation method to obtain global convergence.
Abstract: In this paper, we present a new technique, based on a continuation method, for oscillator analysis using harmonic balance. With the use of Krylov subspace iterative linear solvers, harmonic balance has become a very powerful method for the analysis of general nonlinear circuits in the frequency domain. However, application of the harmonic balance method to the oscillator problem has been difficult. The strong dependence of the oscillator behavior on frequency, and the dependence of the frequency of oscillation on the circuit waveforms result in a very small region of convergence for harmonic balance. The main contribution of this paper is a robust and efficient continuation method to obtain global convergence.

21 citations

Patent

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K.K. Gullapalli1
30 Jun 2001
TL;DR: In this paper, the authors present a method for analyzing small signal response and noise in nonlinear circuits, which includes receiving a circuit description and circuit element models, generating circuit equations using the description and models, and determining a periodic stead-state response of the electrical circuit in the time domain.
Abstract: The present invention relates generally to analyzing small signal response and noise in nonlinear circuits. One embodiment relates to a computer implemented method for analyzing an electrical circuit. The method includes receiving a circuit description and circuit element models, generating circuit equations using the circuit description and models, and determining a periodic stead-state response of the electrical circuit in the time domain. The method further includes linearizing the circuit element models about the steady-state response, generating a time-varying linear system of equations, and representing a small signal solution to the time-varying linear system of equations in response to a sine wave input as an amplitude modulated sine wave. The method also includes discretizing the time-varying linear system of equations by discretizing only the amplitude modulation of the small signal solution and performing a time-varying small signal analysis of the electrical circuit using the discretized equations.

16 citations


Cited by
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TL;DR: A concise survey of the literature on cyclostationarity is presented and includes an extensive bibliography and applications of cyclostatedarity in communications, signal processing, and many other research areas are considered.
Abstract: In this paper, a concise survey of the literature on cyclostationarity is presented and includes an extensive bibliography. The literature in all languages, in which a substantial amount of research has been published, is included. Seminal contributions are identified as such. Citations are classified into 22 categories and listed in chronological order. Both stochastic and nonstochastic approaches for signal analysis are treated. In the former, which is the classical one, signals are modelled as realizations of stochastic processes. In the latter, signals are modelled as single functions of time and statistical functions are defined through infinite-time averages instead of ensemble averages. Applications of cyclostationarity in communications, signal processing, and many other research areas are considered.

861 citations

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TL;DR: A summary of physical insights gained into three-dimensional linear instability through solution of the two-dimensional partial-differential-equation-based nonsymmetric real or complex generalised eigenvalue problem is presented in this article.
Abstract: A summary is presented of physical insights gained into three-dimensional linear instability through solution of the two-dimensional partial-differential-equation-based nonsymmetric real or complex generalised eigenvalue problem. The latter governs linear development of small-amplitude disturbances upon two-dimensional steady or time-periodic essentially nonparallel basic states; on account of this property the term BiGlobal instability analysis has been introduced to discern the present from earlier global instability methodologies which are concerned with the analysis of mildly inhomogeneous two-dimensional basic flows. Alternative forms of the two-dimensional eigenvalue problem are reviewed, alongside a discussion of appropriate boundary conditions and numerical methods for the accurate and efficient recovery of the most interesting window of the global eigenspectrum. A number of paradigms of open and closed flow systems of relevance to aeronautics are then discussed in some detail. Besides demonstrating the strengths and limitations of the theory, these examples serve to demarcate the current state-of-the-art in applications of the theory to aeronautics and thus underline the steps necessary to be taken for further progress to be achieved.

442 citations

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TL;DR: In this paper, the authors describe the latest and most advanced surface potential-based model jointly developed by The Pennsylvania State University and Philips, which includes model structure, mobility and velocity saturation description, further development and verification of symmetric linearization method, recent advances in the computational techniques for the surface potential, modeling of gate tunneling current, inclusion of the retrograde impurity profile, and noise sources.
Abstract: This paper describes the latest and most advanced surface-potential-based model jointly developed by The Pennsylvania State University and Philips. Specific topics include model structure, mobility and velocity saturation description, further development and verification of symmetric linearization method, recent advances in the computational techniques for the surface potential, modeling of gate tunneling current, inclusion of the retrograde impurity profile, and noise sources. The emphasis of this paper is on incorporating the recent advances in MOS device physics and modeling within the compact modeling context

334 citations

Proceedings ArticleDOI

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04 Mar 2002
TL;DR: The efficacy of this linear-centric methodology further improves with increasing model complexity, the inclusion of interconnect parasitics and other analyses that are otherwise difficult with traditional nonlinear models.
Abstract: In this paper, we propose a new harmonic balance simulation methodology based on a linear-centric modeling approach. A linear circuit representation of the nonlinear devices and associated parasitics is used along with corresponding time and frequency domain inputs to solve for the nonlinear steady-state response via successive chord (SC) iterations. For our circuit examples, this approach is shown to be up to 60/spl times/ more run-time efficient than traditional Newton-Raphson (N-R) based iterative methods, while providing the same level of accuracy. This SC-based approach converges as reliably as the N-R approaches, including for circuit problems which cause alternative relaxation-based harmonic balance approaches to fail. The efficacy of this linear-centric methodology further improves with increasing model complexity, the inclusion of interconnect parasitics and other analyses that are otherwise difficult with traditional nonlinear models.

158 citations

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TL;DR: The present bibliography represents a comprehensive list of references on cyclostationarity and its applications by listing most of the existing references up to the year 2005 and by providing a detailed classification group.
Abstract: The present bibliography represents a comprehensive list of references on cyclostationarity and its applications. An attempt has been made to make this bibliography complete by listing most of the existing references up to the year 2005 and by providing a detailed classification group.

143 citations