Publications
Note: Copyrights to the following papers are held by the publishers.
The PDF versions provided here are preprints. Please treat this material
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Journal Publications
 C. Christoffersen, T. Ngo, R. Song, Y. Zhou, S. Pichardo, and
L. Curiel, ``Quasi
ClassDE Driving of HIFU Transducer
Arrays,'' IEEE
Transactions On Biomedical Circuits And Systems, Vol. 13,
No. 1, 2019, pp. 214224, DOI
10.1109/TBCAS.2018.2888990. Link
to associated code at Code Ocean
 P. Luong, C. Christoffersen, C. RossiAicardi and C. Dualibe,
``Nanopower, Sub1 V,
CMOS Voltage References with DigitallyTrimmable Temperature
Coefficient,'' IEEE
Transactions On Circuits And Systems I: Regular Papers,
Vol. 64, No. 4, 2017, pp. 787798, DOI: 10.1109/TCSI.2016.2632072
 C. Christoffersen, W. Wong, S. Pichardo, G. Togtema and
L. Curiel, ``ClassDE Ultrasound
Transducer Driver for HIFU
Therapy,'' IEEE
Transactions On Biomedical Circuits And Systems, Vol. 10,
No. 2, April 2016, pp. 375382. DOI 10.1109/TBCAS.2015.2406119
 M. Kabir, C. Christoffersen, N. Kriplani,
``Transient Simulation Based on State
Variables and Waves,'', Int. Journal of RF and Microwave
ComputerAided Engineering, Vol. 21, No. 3, May 2011,
pp. 314324. DOI: 10.1002/mmce.20520
 Lei Zhu and Carlos E. Christoffersen,
``Transient and SteadyState Analysis
of Nonlinear RF and Microwave Circuits,''
EURASIP Journal on Wireless Communications and Networking,
Vol. 2006, Special Issue on CMOS RF Circuits for Wireless
Applications, Article ID 32097, pp. 111.
 W. Batty, C. E. Christoffersen, A. B. Yakovlev, J. F. Whitaker,
M. Ozkar, S. Ortiz, A. Mortazawi, R. Reano, K. Yang, L. P. B.
Katehi, C. M. Snowden and M. B. Steer,
``Global Coupled
EMElectricalThermal Simulation and Experimental Validation for a
Spatial Power Combining MMIC Array,'' IEEE Trans. on
Microwave Theory and Techniques, Vol. 50, No. 12, December 2002,
pp. 28202833. DOI: 10.1109/TMTT.2002.805142
 W Batty, C. E. Christoffersen, A. J. Panks, S. David,
C. M. Snowden and M. B. Steer,
``ElectroThermal CAD of Power
Devices and Circuits with Fully Physical TimeDependent Compact
Thermal Modelling of Complex Non Linear 3D Systems,''
IEEE Transactions on Components and Packaging Technology,
Vol. 34, No. 4, December 2001, pp. 566590. DOI: 10.1109/6144.974944
 C. E. Christoffersen and M. B. Steer,
``StateVariableBased Transient
Circuit Simulation Using Wavelets,'' IEEE Microwave and
Guided Waves Letters, April 2001, pp. 161163. DOI:
10.1109/7260.916330
 C. E. Christoffersen, U. A. Mughal and M. B. Steer,
``Object Oriented Microwave
Circuit Simulation,'' Int. Journal of RF and Microwave
ComputerAided Engineering, Vol. 10, Issue 3, 2000, pp.
164182.
 C. E. Christoffersen, M. Ozkar, M. B. Steer, M. G. Case and
M. Rodwell, ``State variablebased
transient analysis using convolution,'' IEEE Transactions
on Microwave Theory and Techniques, vol. 47, June 1999,
pp. 882889. DOI: 10.1109/22.769322
 C. E. Christoffersen and M. B. Steer,
``Implementation of the local reference
concept for spatially distributed circuits,'' Int.
Journal of RF and Microwave ComputerAided Engineering, Vol. 9,
Issue 5, 1999, pp. 376384.
 M. B. Steer, J. F. Harvey, J. W. Mink, M. N. Abdulla,
C. E. Christoffersen, H. M. Gutierrez, P. L. Heron, C. W. Hicks,
A. I. Khalil, U. A. Mughal, S. Nakazawa, T. W. Nuteson,
J. Patwardhan, S. G. Skaggs, M. A. Summers, S. Wang, and
A. B. Yakovlev,
``Global Modeling
of Spatially Distributed Microwave and MillimeterWave
Systems,''
IEEE Transactions on Microwave Theory and Techniques,
vol. 47, June 1999, pp. 830839. DOI: 10.1109/22.769316
Book Chapters
 Chapter in "Mathematics in Industry  Scientific Computing in
Electrical Engineering (SCEE 2008)", by Springer, 2010:
C. Christoffersen ``Transient Analysis
of Nonlinear Circuits Based on Waves,'' pp. 159166.
(Link
to publisher site)
 CoAuthor of Chapter in "Automatic Differentiation: Applications,
Theory, and Implementations", Lecture Notes in Computational Science
and Engineering Series, Springer, New York, NY, 2005: Frank P. Hart,
Nikhil Kriplani, Sonali Luniya, Carlos E. Christoffersen and Michael
B. Steer, "Streamlined Circuit Device Model Development with Freeda
and ADOLC",
pp. 295308.
(Link to publisher site)
Conference Publications
 Carlos Christoffersen, Thinh Ngo, Ruiqi Song, Yushi Zhou, Samuel
Pichardo, Laura Curiel ``Suboptimal
Class DE Operation for Ultrasound Transducer Arrays,''
Proceedings of the 2018 IEEE NEWCAS Conference, Montreal, June
2018, pp. 14. DOI: 10.1109/NEWCAS.2018.8585596
 R. Song, C. Christoffersen, Samuel Pichardo, Laura Curiel ,
``
An integrated fullbridge ClassDE ultrasound transducer driver for
HIFU applications,'' Proceedings of the
2016 IEEE NEWCAS Conference, Vancouver, June
2016, pp. 14. DOI: 10.1109/NEWCAS.2016.7604776
 P. Luong, C. Christoffersen, C. RossiAicardi and C. Dualibe,
``Sub1 V, 4 nA CMOS Voltage References
with DigitallyTrimmable Temperature Coefficient,''
Proceedings of the 2014 IEEE NEWCAS Conference, Trois Rivieres, June
2014, pp. 345348. DOI: 10.1109/NEWCAS.2014.6934053
 W. Wong, C. Christoffersen, Samuel Pichardo, Laura Curiel ,
``An Integrated Ultrasound
Transducer Driver For HIFU Applications,'' Proceedings of the
2013 IEEE Canadian Conference on Electrical and Computer Engineering,
Regina, May 2013. DOI: 10.1109/CCECE.2013.6567791
 M. Kabir, C. Christoffersen,
``WaveBased Transient
Analysis Using Block NewtonJacobi,'' Proceedings of the 2011
IEEE Canadian Conference on Electrical and Computer Engineering,
Niagara Falls, May 2011, pp 669673. DOI: 10.1109/CCECE.2011.6030537
 C. E. Christoffersen, G. Toombs and A. Manzak,
``An UltraLow Power CMOS PTAT
Current Source,'' Proceeedings of the ArgentineUruguay
Conference on MicroNanoelectronics, Technology and Applications,
October 78 2010, Montevideo, Uruguay,
pp. 3540. URL
 C. E. Christoffersen ``Transient Analysis
of Nonlinear Circuits Based on Waves,'' Proceeedings of the 7th
International Conference on Scientific Computing in Electrical
Engineering (SCEE 2008), September 28  October 3 2008, Helsinki
Institute of Technology, Finland.
 C. E. Christoffersen, M. Condon and T. Xu, ``A new method for the determination of the
locking range of oscillators,'' Proceeedings of the 2007
European Conference on Circuit Theory and Design (ECCTD07),
Seville, August 2007, pp. 575578. DOI: 10.1109/ECCTD.2007.4529661
 Zhou Wang and Carlos Christoffersen,
``SteadyState Analysis of Circuits
with Multiple Adaptive Grids,'' 2007 IEEE Canadian Conference
on Electrical and Computer Engineering Digest, Vancouver, April
2007. DOI: 10.1109/CCECE.2007.34
 S. Luniya, W. Batty, V. Caccamesi, M. Garcia, C. Christoffersen,
S. Melamed, W. R. Davis and
M. Steer, "Compact
Electrothermal Modeling of an Xband MMIC," 2006 IEEE
Int. Microwave Symp. Digest, June 2006, pp. 651654. DOI:
10.1109/MWSYM.2006.249698
 C. Christoffersen, "Implementation
of Exact Sensitivities in a Circuit Simulator Using Automatic
Differentiation", 20th European Conference on Modelling and
Simulation, May 2006, pp. 238243.
 M. B. Steer, N. M. Kriplani, S. Luniya, F. Hart, J. Lowry and
C. Christoffersen ``fREEDA: An Open Source Circuit Simulator,''
2006 International Workshop on Integrated Nonlinear Microwave and
MillimeterWave Circuits, pp. 112115. DOI: 10.1109/INMMIC.2006.283523
 Lei Zhu and Carlos Christoffersen, ``Adaptive Harmonic Balance Analysis of
Oscillators using Multiple Time Scales,'' 3rd International
IEEE Northeast Workshop on Circuits and Systems Digest, June 2005,
pp. 187190. DOI: 10.1109/NEWCAS.2005.1496738
 Lei Zhu and Carlos Christoffersen, ``Fast Transient Analysis of Oscillators
using Multiple Time Scales with Accurate Initial Conditions,''
2005 IEEE Canadian Conference on Computer and Electrical Engineering
Digest, Saskatoon, May 2005, pp. 700703. DOI: 10.1109/CCECE.2005.1557030
 Sonali Luniya, Michael B. Steer and Carlos Christoffersen, "High Dynamic Range Transient Simulation of
Microwave Circuits," 2004 IEEE Radio and Wireless Conference
Digest, September 2004, pp. 487490. DOI: 10.1109/RAWCON.2004.1389183
 Frank P. Hart, Nikhil Kriplani, Sonali Luniya, Carlos
E. Christoffersen and Michael B. Steer, "Streamlined Circuit Device Model Development
with Freeda and ADOLC," 4th International Conference on
Automatic Differentiation, Chicago, USA, July 2004.
 Carlos Christoffersen and Jude Alexander, ``An Adaptive Time Step Control Algorithm For
Nonlinear Time Domain Envelope Transient,''
2004 IEEE Canadian Conference on Electrical and Computer
Engineering Digest, Niagara Falls, May 2004,
pp. 08830886. DOI: 10.1109/CCECE.2004.1345256

C. Christoffersen, S. Velu and M. B. Steer,
`` A Universal Parameterized Nonlinear
Device Model Formulation for Microwave Circuit
Simulation,'' 2002 IEEE Int. Microwave Symp. Digest,
June 2002, pp 21892192. DOI: 10.1109/MWSYM.2002.1012306

W. Batty, C. E. Christoffersen, A. B. Yakovlev, J. F. Whitaker,
M. Ozkar, S. Ortiz, A. Mortazawi, R. Reano, K. Yang, L. P. B. Katehi,
C. M. Snowden and M. B. Steer, ``Global Coupled EMElectricalThermal
Simulation and Experimental Validation for a Spatial Power Combining
MMIC Array,'' 2002 IEEE Int. Microwave Symp. Digest,
June 2002, pp. 21772180. DOI: 10.1109/MWSYM.2002.1012303

M. B. Steer, C. Christoffersen, S. Velu and N. Kriplani, ``Global Modeling of RF and
Microwave Circuits,'' Mediterranean Microwave
Conf. Digest, June 2002.

W. Batty , C. E. Christoffersen, C. M. Snowden and M. B. Steer,
`` Fully Physical Coupled
ElectroThermal Modelling of Power Devices and Circuits,''
PSSD conference Digest, Ilkley, UK, March 2002.

C. E. Christoffersen and M. B. Steer, ``Comparison of Wavelet and
TimeMarchingBased Microwave Circuit Transient Analyses ,''
2001 IEEE Int. Microwave Symp. Digest, May 2001,
pp. 447450. DOI: 10.1109/MWSYM.2001.966927

M. B. Steer and C. E. Christoffersen, ``Generalized circuit formulation for the transient
simulation of circuits using wavelet, convolution and timemarching
techniques ,'' Proc. of the 15th European Conference on
Circuit Theory and Design, Aug 2001, pp. 205208.

W. Batty, C. E. Christoffersen, S. David, A. J. Pan ks, R. G.
Johnson, C. M. Snowden and M. B. Steer, ``Global Electrothermal
CAD of Complex Non Linear 3D Sy stems Based on a Fully Physical
Timedependent Compact Thermal Model,'' 2001 IEEE
Int. Microwave Symp. Digest, May 2001, pp. 667670. DOI:
10.1109/MWSYM.2001.966982

W. Batty, C. E. Christoffersen, S. David, A. J. Panks, R. G. Johnson,
C. M. Snowden and M. B. Steer, ``Fully
physical, timedependent thermal modelling of complex 3dimensional
systems for device and circuit level electrothermal CAD''
(extended abstract), SemiTherm XVII, San Jose, March 2001.

W. Batty, C. E. Christoffersen, S. David, A. J. Panks, R. G. Johnson,
C. M. Snowden and M. B. Steer, ``Predictive
microwave device design by coupled electrothermal simulation based on
a fully physical thermal model'' (extended abstract), EDMO
2000, Glasgow UK, November 2000. DOI: 10.1109/EDMO.2000.919042

W. Batty, C. E. Christoffersen, S. David, A. J. Panks, R. G. Johnson,
C. M. Snowden and M. B. Steer, ``Steadystate and transient
electrothermal simulation of power devices and circuits based on a
fully physical thermal model,'' THERMINIC 2000 Digest,
Budapest, September 2000.

C. E. Christoffersen and M. B. Steer, ``Transient analysis of a spatial power combining
amplifier,'' 1999 IEEE Int. Microwave Symp. Digest,
June 1999, pp. 791794. DOI: 10.1109/MWSYM.1999.779878

H. Gutierrez, C. E. Christoffersen and M. B. Steer, ``An integrated environment for the simulation of
electrical, thermal and electromagnetic interactions in
highperformance integrated circuits,'' Proc. IEEE 6th
Topical Meeting on Electrical Performance of Electronic Packaging,
Sept. 1999. DOI: 10.1109/EPEP.1999.819229

C. E. Christoffersen, M. B. Steer and M. A. Summers,
``Harmonic balance analysis for systems
with circuitfield interactions,'' 1998 IEEE Int. Microwave
Symp. Digest, June 1998, pp. 11311134. DOI:
10.1109/MWSYM.1998.705193

M. A. Summers, C. E. Christoffersen, A. I. Khalil, S. Nakazawa,
T. W. Nuteson, M. B. Steer and J. W. Mink, ``An integrated
electromagnetic and nonlinear circuit simulation environment for
spatial power combining systems,'' 1998 IEEE Int. Microwave
Symp. Digest, June 1998, pp. 14731476. DOI: 10.1109/MWSYM.1998.700653

M. B. Steer, C. E. Christoffersen, H. Gutierrez, S. Nakazawa,
M. Abdulla, and T. W. Nutesson, ``Modelling of Large NonLinear
Systems Integrating Thermal and Electromagnetic Models,''
European Gallium Arsenide and related IIIV Compounds Application
Symposium, October 1998, pp. 169174.

M. B. Steer, M. Ozkar, and C. E. Christoffersen, ``Circuit level
modelling of spatially distributed mm and sub mmWave Systems,''
Proc. 1998 IEEE Sixth Int. Conf. on Terahertz Electronics
Proceedings, September 1998, pp. 2124. DOI: 10.1109/THZ.1998.731654

M. B. Steer, M. N. Abdulla, C. E. Christofersen, M. Summers,
S. Nakazawa, A. Khalil and J. Harvey, ``Integrated Electromagnetic
and Circuit Modeling of Large Microwave and MillimeterWave
Structures,'' IEEE APS, June 1998.

F. Nusseibeh, T. W. Nuteson, J. Patwardhan, M. A. Summers,
C. E. Christoffersen, J. Kreskovsky, and M. B. Steer, ``Computer
Aided Engineering Environment for Spatial Power Combining
Systems,'' IEEE MTTS Int. Microwave Symp. Dig.,
pp.~10731076, June 1997. DOI: 10.1109/MWSYM.1997.602987

J.F. Harvey, T.W. Nuteson, J. Patwardhan, M.A. Summers,
C.E. Christoffersen, F. Nusseibeh, J. Kreskovsky, and M.B. Steer,
``A Unified Electromagnetic, Nonlinear Circuit, and Thermal
Analysis for Complex Spatial Power Combining Architectures,''
Proc. WRI Int. Symp. on Directions for the next Generation of MMIC
Devices and Systems, June 1997.

C. E. Christoffersen, L. A. Lahoz and M.I Schiavon, ``Extracción de los Elementos Parásitos de
un Circuito Integrado a Partir del Layout'' (Integrated
circuit parasitic elements extraction from the layout, in
Spanish), Segundo Simposio de Microelectrónica, Rosario,
9 y 10 de noviembre de 1995.

C. . E. Christoffersen, L. A. Lahoz and M.I Schiavon, ``Detección de los Transistores de un Circuito
Integrado a Partir del Layout'' (Integrated circuit
transistors detection from the layout, in Spanish), Terceras
Jornadas de Investigación de las Universidades del Grupo de
Montevideo, Concordia  Salto, 27, 28 y 29 de septiembre de
1995.
Thesis Reports

C. E. Christoffersen, ``Global Modeling of
Nonlinear Microwave Circuits,'' Ph.D. Dissertation, North
Carolina State University, 2000.

C. E. Christoffersen, ``State variable
harmonic balance simulation of a quasioptical power combining
system,'' Master's thesis, North Carolina State University,
1998.

C. E. Christoffersen, ``Programa Estimador
de Parametros de Transistores Bipolares y de Efecto de Campo de
Juntura'' (Program to estimate parameters for BJTs and
FETs, in Spanish), Proyecto final de ingeniería,
Universidad Nacional de Rosario, 1993.
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Last Updated: 07/2022