From: debchat@vax2.concordia.ca (DEB CHATTERJEE)
Newsgroups: comp.cad.cadence
Subject: Lossy Xmission lines; Attn: MARK JOHNSON
Keywords: Lossy Xmission lines; EMI/ EMC aspects.
Date: 26 Jul 92 01:12:00 GMT
Distribution: na
Organization: Concordia University
News-Software: VAX/VMS VNEWS 1.41

************************* Mark's Questions ************************** 
From:	IN%"mjohnson@netcom.COM"  "Mark Johnson" 24-JUL-1992 12:08:20.03
To:	DEB CHATTERJEE <debchat@Vax2.Concordia.CA>
Subj:	RE: lossy multiconductor xmission lines


 >>  The analysis is so crucial in compaction of VLSI systems
 >>  that such codes must be listed on this group.

>Certainly you have strong feelings!

>Please make a posting to the network, setting forth your
>"threshold" criteria, where these effects become non-negligible.

   > * Clock frequency > X radians/sec
   > * Signal edge rate > Y volts/sec
   > * Time varying current density > J amps per square meter per second
   > * Q of resonant system > Z (dimensionless)
   > etc.

>...... (stuff deleted from Mark's original posting) ......

>Please post to the net rather than making an email reply to me.

************************** My Reply *************************************

 Hi Mark !

 Thanks for your questions. The reason I mentioned such codes, was not that
 I have hordes of information on them. The parameters you mentioned are just
 the ones that are getting attention in the recent times. I am not at all in
 a postion to make authorative comments on your questions. However, your
 questions fall into the broad category of EMC analysis of VLSI circuits that
 are connected via multiconductor transmission lines as high-speed interconnects
 as carriers of both analog (continuous) and logic (digital) waveforms. I had
 found numerous articles on IEEE Transactions on Electromagnetic Compatibility
 addressing this issue. The papers I looked into indicate a paucity in the
 work done for EMC planning in such systems. (The IEEE-T-EMC, May 1992 also
 discusses this. BTW, there is a very good review article on the EMI/EMC effects
 in such circuits.) IMHO, cross-talk models, signal distortions are the major
 effects studied by several researchers for the parameters you have questioned.

 My question: Does Cadence model accurately multiconductor xmission lines to
              consider EMI/ EMC effects ?

 IMO, the answer is NO. The proof: I have appended a list of refernces that I
 had collected earlier. My interest in this area is really academic - and is
 just out of curiosity - to know what's latest in CAD of microwave circuits.
 I have not worked in any industry to have profound knowledge in this area.
 I am including a \LaTex file of a brief write-up on the extension of the 
 CAD softwares to include EMI/ EMC modeling of large VLSI circuits. I hope 
 that it turns out to be useful for some !!

 (Please excuse my crude grammar !)

 - hope this helps,

   deb chatterjee

  e-mail: debchat@vax2.concordia.ca

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\centerline{\underline {\bf Modeling of VLSI interconnects for EMC planning\
                            in design of compact VLSI systems}}
\small
 Achieving high performance {\underline {and}} compaction {\em simultaneously} 
from any VLSI system is the ultimate objective in any design. A wide variety of 
VLSI circuits for use in computers, EW radars and bio-medical applications
need to be routinely developed meeting the above requirements as closely as
possible. There are many aspects in such a design - such as design of circuits
and also maintaining high quality of signal transmission throughout the VLSI
layout. In the recent years, introduction of GaAs and CMOS technology has 
allowed the user to operate at very high speeds, and often frequencies more
than 10 GHz are not uncommon with such techniques. It is a common procedure
to use state-of-the-art CAD tools in designing/ evaluating several candidate
systems before a choice can be made regarding its final production. 

 The quality of signal transmission has often been overlooked, and, as such 
this has placed serious problems in achieving the desired performance. The
recent work of Ruheli [1] and Chang [2,3] show that several factors contribute
to signal degradation. The major ones are: (i) cross-talk (ii) pulse delay and
(iii) signal distortion. (Other issues have also been discussed by Chang [2,3]
and hence are not discussed here). Chang has shown that such factors depend on
the signal line characteristics - which are either (a) open-microstrip or (b)
shielded microstrip (triplate) structures. Brews [7] has modeled lossy VLSI 
interconnections as waveguide junctions to study signal degradation. The short
list of references appended here reflect some of the recent work in this area.

 Multiconductor-microstrip structures - that carry different signals (digital/
analog) from one port to the other - are widely used for compaction reasons. 
Most of the work has been primarily related to modeling of such interconnections
as transmission line structures that operate in the TEM or quasi-TEM mode. For 
pulse propagation along such lossy lines (supporting quasi-TEM mode), transient
signal analysis has been performed [11-14, 20]. This aspect of signal quality
is important - as discussed by Pan {\em et al} [9]. However, as pointed out by
Ghione {\em et al}. [37], the transmission line model alone could be quite 
inadequate because it cannot model the radiation (EMI) from, and, surface wave 
losses (signal attenuation) in such structures. These are some drawbacks in
the current modeling techniques used in CAD of VLSI systems. The present trend
towards more speed in logic circuits thus dictates that more emphasis be placed
in understanding these and other related effects that cause signal degradation.

\centerline{\underline {\bf The nature of EMI in VLSI systems}}

 In general, from an EMI/ EMC point of view, the cross-talk is the major source
of EMI. This is manifested in the form of mutual coupling between signal lines.
The effects of this EMI are listed can be detrimental in several practical
applications.

 In high-speed computers, cross-talk between lines causes false triggering of
latching circuits causing a chain of total malfunction to occur. In life-saving
situations, such as monitoring a cardiac patient's pulse-rate, the counters are
expected to lock-in with the patients ECG signal-response. In this typical
case, the threshold signal level is quite low. Thus off-band radiation from a
particular signal line could definitely couple into the adjacent lines, causing
fatal consequences. Detection meters (hyperthermia) used for cancer-research
have also to have proper operational charactersistics. In EW (early warning)
radar systems, `false' target echoes may be identified when the signal 
processing circuitry responds to logic levels that do {\underline {not}}
correspond to real target echoes but are results of unwanted EMI due to the
cross-talk effects. In all these applications, the threshold level determination
for the receptor circuit is important. Quantitative knowledge of the EMI margin
is therefore another important parameter that needs to be introduced when 
doing the optimization for the circuit, via existing CAD tools, in the initial
design stages.

 Many circuits consist of either analog or digital components plus active
devices making nonlinear loads be operative at one end of the VLSI interconnect.
Moreover, since fabrication/ manafacturing processes allow more flexibility, the
general trend is to combine both analog and digital features into what is known
as a hybrid circuit. Thus there exists additional complication where signal 
lines carrying logic (pulsed) waveforms can be coupled to ones carrying any
arbitrary time waveform (analog). Thus, this brief exposure allows one to
appreciate the importance of EMI. Moreover, none of the CAD design tools used
for VLSI testing allow detailed EMC checks, so that the EMI susceptibility
remains as a major concern.

 The main problem addressed by detailed EMC studies is:

`{\em How close, physically, signal lines can be placed given a set of operating
conditions for a typical circuit}'

 A good suggestion for an answer to this problem is to begin by analysing the
cross-talk level(s) for VLSI interconnects under different conditions. The
knowledge is subsequently used in determining the threshold that can be 
tolerated by circuits/ signal-lines. This quantitative estimate may be used as
an independent parameter while using CAD tools for designing an optimum circuit.

\centerline{\bf {\underline {Scope for further work}}}

 The foregoing discussions may provide some interesting work for practical
applications to compact VLSI circuit design. Compaction dictates that the 
physical space be reduced. Thus, instead of straight VLSI interconnects, one
could have arbitrary configuration. Handling arbitrariness becomes a major
problem for engineering design applications.

 EMC planning for such systems shows that detailed computer analysis need to
be done considering several practical possibilities before any actual design
may be implemented. This makes a design successful. This is achieved by the
existing CAD tools which tend to obtain an optimized layout given a set of
input parameters. Again, the CAD tools contain solution to canonical problems.
Thus improvement of the existing CAD tools appear to be a important task. 

 The success of an analysis technique suitable for engineering applications
deepends on:

(1) generality of the formulation - which depends how closely the formulation
    models a physical reality, and,

(2) flexibility and cost-effectiveness of the formulation, {\em i.e}, how 
    adaptive the formulation is terms of (i) accuracy and (ii) c.p.u time
    consumption on any reasonable machine. 

 Thus, given a formulation - part (1), it becomes quite important to obtain
numerical answers by employing different analysis techniques. A comparison
of the results techniques will determine the `{\em figure-of-merit}' for any
CAD analysis.

 Therefore, a general numerical comparison of the solution techniques, for any
specified model (formulation) is definitely an useful work for advancement of
CAD techniques. This applies to any type of modeling technique.

 Development of improved models for VLSI interconnects is another aspect of the
work. This is more time consuming. In the recent past, multiconductor lines,
modeling VLSI interconnects, were analysed via a two-dimensional technique. This
means that the lines were considered to be of arbitrary cross-section but were
{\em infinitely} long. One of the practical models that can be developed for a
realistic assessment of EMI analysis is by considering the finiteness of the
line length. This work remains to be done, and, to this end the application of
finite-element techniques appear to be useful. This is because the technique
allows arbitrary physical structures to be modeled by triangular grids. However,
application of the technique to high-speed analog and digital VLSI signal lines
remain a very challenging task.

\vfill\eject

\input double

\Large{\centerline{\bf SELECTED REFERENCES}}

\normalsize

\centerline{\underline {\bf {Multiconductor Transmission lines and VLSI\
                             Interconnections}}}

[1] A.E.Ruheli,``Survey of Computer-aided electrical analysis of integrated
circuit interconnections'',{\em IBM J.Res. Development}, vol. 23, pp. 626-639, 
Nov. 1979

[2] C.S.Chang,`Transmission Lines',in {\em Advances in CAD for VLSI},vol. 3,
part 2,(A.E.Ruheli ed.) Amsterdam: Elsevier, 1987, sec. 11.3, pp. 292-332.

[3] C.S.Chang,`Printed Circuit Board Signal Line Electrical Design', in {\em
Principles of Electronic Packaging}, (ch. 4), D.L.Seraphim, R.C.Lasky and C-Y Li
(eds.), McGraw-Hill Book Company, 1989.

[4] R.H.Katyl and J.G.Simek,`Electrical Design Concepts in Electronic Packaging
',(ch. 3),{\em ibid.}.

[5] V.Dorvak,``Computer Simulation of signal propagation through a non-uniform
transmission line'',{\em IEEE Transaction on Circuit Theory},vol. CT-20, Sept.
1973, pp. 580-583.

[6] R.Wang \& O.Wing,``Transient analysis of dispersive VLSI interconnects
terminated in non-linear loads'', (paper to communicated in {\em IEEE Trans.
Computer-Aided Design}.)

[7] J.R.Brews,``Transmission line models for lossy waveguide interconnections 
in VLSI'',{\em IEEE Trans. Electron Devices},vol. 33, pp. 1356-1365, Sept. 1986.

[8] H.Hasegawa \& S.Seki,``On-chip pulse transmission in very high speed 
LSI/VLSIs'', Microwave \& Monolithic Circuits Symposium (MCS), 1984, pp. 29-33.

[9] G.-W Pan, K.S.Olson, and B.K.Gilbert,``Improved algorithmic methods for the
prediction of wavefront propagation behavior in multiconductor transmission 
lines for high frequency digital signal processors'',{\em IEEE Trans. Computer-
Aided Design},vol. 8, pp. 608-621, June 1989. 

[10] C.L.Seitz (ed.),{\em Advanced Research in VLSI}, Proceedings of Dicenneial
Caltech Conference, 1989, The MIT Press, Cambridge, MA 1989

[11] R.Wang \& O.Wing,``A Circuit Model of a System of VLSI Interconnects for
Time Response Computation'',{\em IEEE Transactions on Microwave Theory \&
Techniques},vol. 39, no. 4, April 1991, pp. 688 - 694

[12] T.Razaban,``Time-domain transient analysis of partially coupled lines;
applications to VLSI/VHSIC interconnections'', {\em IEEE Transactions on
Microwave Theory \& Techniques}, May 1987, pp. 530-533

[13] K.D.Marx \& R.I.Eastin,``A configuration-oriented SPICE model for 
multiconductor transmission lines with homogeneous dielectrics'',{\em IEEE Trans
on Microwave Theory \& Techniques}, vol. 38, no. 8, Aug. 1990, pp. 1123-1129

[14] J.E.Schutt-Aine \& R.Mittra,``Scattering parameter transient analysis of
transmission lines loaded with nonlinear loads'',{\em IEEE Trans. on Microwave
Theory \& Techniques},March 1988, pp. 529-536

[15] M.A.Mehalic \& R.Mittra,``Investigation of Tapered Multiple Microstrip
Lines for VLSI Circuits'',{\em IEEE Trans. Microwave Theory \& Techniques},
vol. 38, no. 11, November 1990, pp. 1559 - 1568.

[16] L.Carin \& K.J.Webb,``Isolation effects in single- and dual-plane VLSI 
interconnects'',{\em IEEE Trans. on Microwave Theory \& Techniques}, April 1990,
vol. 38, pp. 396-404.

[17] L.Carin \& K.J.Webb,``An Equivalent Circuit Model for Terminated Hybrid-
Mode Multiconductor transmission lines'',{\em IEEE-T-MTT}, Nov. 1989, pp. 1784-
1793

[18] R.-B Wu,``Interperiod Capacitance Calculations for Three-Dimensional 
Multiconductor Systems'',{\em IEEE Trans. on Microwave Theory \& Techniques}, 
vol. 36, no. 11, Nov. 1988, pp. 1515-1521.

[19] O.Palusinski \& A.Lee,``Analysis of Transients in Nonuniform \& Uniform 
Multiconductor Transmission lines'',{\em IEEE Trans. Microwave Theory \& 
Techniques}, vol. 37, no. 1, January 1989, pp. 127-138. 

[20] A.R.Djordjevi\'c, T.K.Sarkar and R.F.Harrington,``Time Domain Response of
Multiconductor Transmission Lines'',{\em Proceedings of the IEEE}, v. 75, 1987,
pp. 743-763, 1987

[21] J.J.Yang, G.E.Howard and Y.L.Chow,``A Simple Technique for Calculating the
Propagation Dispersion of Multiconductor Transmission Lines in Multilayer 
Dielectric Media'',{\em IEEE-T-MTT}, April 1992, pp. 622-627.

[22] G.E.Howard, J.J.Yang and Y.L.Chow,``A Multipipe model of General strip
transmission lines for Rapid Convergence of Integral Equation Singularities'',
{\em ibid.}, pp. 628-636.

[23] J-F Mao and Z-F li,``Analysis of time response of Multiconductor
transmission lines with Frequency-Dependent losses by Method of Convolution
Characteristics'',{\em ibid.}, pp. 637-644. 

[24] R-B Wu, C-N Kuo and K.K.Chang,``Inductance, Resistance Computations for
Three-Dimensional Multiconductor Interconnection Structures'',{\em IEEE-T-MTT},
vol. 40, no. 2, Feb. 1992, pp. 263-271.

[25] E.G.Farr, C.H.Chan and R.Mittra,``A frequency-dependent coupled mode
analysis of multiconductor microstrip lines with applications to VLSI 
interconnection problems'',{\em IEEE-T-MTT}, vol. 34, pp. 307-310, Feb. 1986.

[26] J.P.Webb,``Absorbing Boundary Conditions for Finite Element Analysis of
Planar Devices'', {\em IEEE-T-MTT}, Sept. 1990, vol. 38, no. 9, pp. 1328-1332.

[27] P.Silvester,``TEM properties of microstrip lines'',{\em Proc. IEE}, v. 115,
pp. 93-98, 1968.

[28] Z.Pantic and R.Mittra,``Quasi-TEM analysis of microwave transmission lines
by the finite element method'',{\em IEEE-T-MTT}, vol. 34, pp. 1086-1103, 1986.

[29] R.E.Collin,{\em Field Theory of Guided Waves},(ch. 4),IEEE Press, N.Y.,1991

[30] P.Silvester and R.L.Ferrari,{\em Finite Elements for Electrical Engineers},
(2nd. ed.), Cambridge University Press, 1990 

[31] C.A.J Fletcher,{\em Computational Galerkin Methods}, Springer-Verlag, N.Y.,
1984.

[32] L.E.Scales,{\em Introduction to Non-linear Optimization},New-York:Springer-
Verlag, 1985

\centerline{\underline {\bf Modeling of Crosstalk on Multiconductor Lines}}

[33] C.R.Paul,``Solution of Transmission Line Equations for Three-Conductor
Lines in Homogeneous Media'',{\em IEEE Trans. on Electromagnetic Compatibility},
vol. 20, pp. 216 -222, Feb. 1978

[34] C.R.Paul \& J.A.McKnight,``Prediction of Crosstalk Involving Twisted pairs
of wires, Part II, A Simplified Low-Frequency Prediction Model'',{\em IEEE Trans
on Electromagnetic Compatibility},vol. 21, pp. 105-114, May 1979

[35] S.Seki and H.Hasegawa,``Analysis of crosstalk in very high speed LSI/ VLSI
using coupled multiconductor MIS microstrip line'',{\em IEEE Trans. Microwave
Theory Tech.},vol. 34, pp. 1715-1720, Dec. 1986

[36] S.P.Castillo, C.H.Chan \& R.Mittra,``Analysis of N-conductor transmission
line systems with non-linear loads with application to CAD design of digital
circuits'', in {\em Proc. Int. Symp. Electromagnetic Compatibility}, Sept. 1986,
pp. 174-175.

[37] G.Ghione, I.Miao and G.Vecchi,``Modeling of Multiconductor buses and
analysis of crosstalk, propagation delay and pulse distortion in high-speed GaAs
logic circuits'',{\em IEEE-T-MTT}, March 1989, pp. 445 - 456.

[38] T.Fang, J.J.Whalen and G.K.C Chen,``Using NCAP to Predict RFI Effects in
Linear Bipolar Circuits'',{\em IEEE Trans. on Electromagnetic Compatibility},
vol. 22, pp. 191-202, Aug. 1980

[39] J.E. DeFalco,``Reflection and cross-talk in logic circuit interconnects'',
{\em IEEE Spectrum}, pp. 616-626, June 1970.

[40] {\em `Integrated Circuit Electromagnetic Compatibility Handbook'}, Report
MDC E 1929, 1 August 1979, McDonnell Douglas Company

\centerline {\underline {\bf Computer-Aided Analysis, Simulation and Design\
                              of VLSI Circuits}}

[41] J.W.Bandler \& S.H.Chen,``State of the art review of circuit optimization
of microwave CAD'',{\em IEEE Trans. on Microwave Theory \& Techniques},Feb. 1988
pp. 424-443

[42] V.Rizzoli \& E.Marazzi,``A general purpose program for nonlinear microwave
circuit design'',{\em IEEE Trans. on Microwave Theory \& Techniques},Sept. 1983,
pp. 762-770

[43] V.Rizzoli \& A.Lipparini,``General stability analysis of periodic steady-
state regimes in nonlinear microwave circuits'',{\em IEEE Trans. on Microwave
Theory \& Techniques},Jan. 1985, pp. 30-37

[44] V.Rizzoli \& A.Neri,``State of art and present trends in nonlinear 
microwave circuit design'',{\em IEEE Trans. on Microwave Theory \& Techniques},
Feb. 1988, pp. 343-365

[45] K.S.Kundert and A.L.Sangiovanni-Vintcelli,``Simulation of nonlinear 
circuits in the frequency domain'',{\em IEEE-T-MTT}, vol. 5, 1986, pp. 521-535.

[46] R.Unbehauen and A.Cichocki,{\em MOS: Switched-Capacitor and Continous-Time
Integrated Circuits and Systems: Analysis and Design}, Springer-Verlag, Berlin,
1989.	

[47] W.Banzhof,{\em Computer-Aided Circuit Analysis using SPICE},Prentice-Hall,
Englewood-Cliffs.,N.J.,1989 

[48] L.O.Chua \& P.M.Lin,{\em Computer Aided Analysis of Electronic Circuits:
Algorithms and Computational Techniques}, Prentice-Hall, Englewood Cliffs.,N.J.,
U.S.A, 1975. (ref. [7] was obtained from [2])

[49] D.D.Weiner and J.F.Spina,{\em Sinusoidal Analysis and Modeling of Weakly
Nolinear Circuits}, New York: Van-Nostrand, 1980.

\vfill\eject
\centerline{\underline {\bf Relevant Ph.D Theses}}

[50] J.E.Schutt-Aine,``Modeling \& simulation of high-speed digital circuit
interconnections'',Ph.D dissertation, Electromagnetic Communication Laboratory,
University of Illinois, Urbana, IL, 1988

[51] R.Wang,``Computation of transient response of dispersive multiconductor
systems'',Ph.D thesis, Columbia University, New York, NY 1990.

\end{document}
Newsgroups: comp.cad.cadence