Ex Parte Ding et al

Patent Trial and Appeal Board

Mar 27, 2013

11166659 (P.T.A.B. Mar. 27, 2013)

UNITED STATES PATENT AND TRADEMARK OFFICE
____________________

BEFORE THE PATENT TRIAL AND APPEAL BOARD
____________________

Ex parte LI DING, PEIVAND FALLAH-TEHRANI,
and ALIREZA KASNAVI
____________________

Appeal 2010-008476
Application 11/166,6591
Technology Center 2100
____________________

Before JOSEPH F. RUGGIERO, MARC S. HOFF, and
CAROLYN D. THOMAS, Administrative Patent Judges.

HOFF, Administrative Patent Judge.

DECISION ON APPEAL
STATEMENT OF THE CASE
Appellants appeal under 35 U.S.C. § 134 from a Final Rejection of
claims 1-8, 10-16, and 18-21.2 We have jurisdiction under 35 U.S.C. § 6(b).
We reverse.
Appellants’ invention is a method and apparatus for generating a
model for a circuit cell timing analysis and for signal integrity analysis

1 The real party in interest is Synopsys, Inc.
2 Claims 9 and 17 have been cancelled.
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(Spec. 1). A behavioral model for a circuit cell is automatically generated by
modeling the current in the circuit cell as a function of the input voltage,
output voltage, and the history of the current. The history of the current may
be calculated incrementally using a recursive convolution at each time step.
The behavioral model may be, e.g., a gate current model, which includes,
e.g., an output terminal capacitor and a current source, which is a function of
the input voltage, the output voltage, and the history of at least one of the
current, voltage, and charge of the cell (Spec. 4-5).
Claim 1 is exemplary of the claims on appeal:
1. A method of modeling a circuit cell in integrated circuit design; the
method being performed in a computer, the method comprising:
automatically generating a behavioral model for the circuit cell;
automatically calculating a current in the model for the circuit cell as a
function of an input voltage, an output voltage and a history of at least one
of the current, voltage and charge values of the model for the circuit cell;
and
reporting the determined current in the model for the circuit cell.
The Examiner relies upon the following prior art in rejecting the
claims on appeal:
Barford US 5,946,482 Aug. 31, 1999
Igor Keller et al., A Robust Call-Level Crosstalk Delay Change
Analysis, INT’L CONF. ON COMPUTER AIDED DESIGN 147 (2004).
Seonghearn Lee, Empirical Nonlinear Modeling for RF MOSFETs, 14
INT’L J. RF & MICROWAVE COMPUTER-AIDED ENG’G 182 (2004).
ALAN V. OPPENHEIM ET AL., SIGNALS & SYSTEMS (2d ed. 1997).
Claims 1, 4, 6-8, 10, 11, 13-16, and 19-21 stand rejected under 35
U.S.C. § 103(a) as being unpatentable over Keller in view of Barford.
Claims 2, 3, 12, and 18 stand rejected under 35 U.S.C. § 103(a) as
being unpatentable over Keller in view of Barford and Lee.
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Claim 5 stands rejected under 35 U.S.C. § 103(a) as being
unpatentable over Keller in view of Barford and Oppenheim.
Throughout this decision, we make reference to the Appeal Brief
(“App. Br.,” filed June 3, 2009), the Reply Brief, (“Reply Br.,” filed Dec. 1,
2009), and the Examiner’s Answer (“Ans.,” mailed June 1, 2010) for their
respective details.

ISSUES
Appellants argue, inter alia, that because Keller teaches calculating
current for a circuit model as a function only of the input voltage and output
voltage, and not of any history values, Keller’s principle of operation is
inconsistent with using a history of currents, voltages, or charges (App. Br.
18). Appellants argue that the proposed modification of Keller in view of
Barford would thus require a change in the principle of operation of Keller,
and that the teachings of the references are not sufficient to render the claims
prima facie obvious (App. Br. 19).
Appellants’ contentions present us with the following issues:
1. Does the combination of Keller and Barford teach or fairly suggest
automatically calculating a current in a model for a circuit cell as a function
of an input voltage, an output voltage, and a history of at least one of the
current, voltage, and charge values of the model?
2. Would the Examiner’s proposed modification require a change in
the principle of operation of Keller?

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PRINCIPLE OF LAW
If the proposed modification or combination of the prior art would
change the principle of operation of the prior art invention being modified,
then the teachings of the references are not sufficient to render the claims
prima facie obvious. In re Ratti, 270 F.2d 810, 813 (CCPA 1959).

ANALYSIS
CLAIMS 1, 4, 6-8, 10, 11, 13-16, AND 19-21
Independent claims 1, 10, 11, 16, and 21 each recite calculating a
current in the model for the circuit cell as a function of an input voltage, an
output voltage, and a history of at least one of the current, voltage, and
charge values of the model.
We are persuaded by Appellants’ argument that the proposed
combination of Keller with Barford would require a change in the principle
of operation of Keller (App. Br. 19-20). Keller teaches a voltage in, voltage
out (ViVo) current model for each gate in the standard cell library (p. 149).
Keller explicitly teaches that the current table from ViVo “is a function of
instantaneous voltages on input and output and [is] not dependent on
transition history” (id.). Because of this non-dependence on transition
history, Keller teaches that its model may be pre-characterized, and its
generation done through DC simulations using Spice (id.).
We agree with Appellants that if the recursive convolution disclosure
of Barford were combined with Keller, Keller could no longer use a ViVo
model in which each gate is pre-characterized (App. Br. 20).
We do not agree with the Examiner’s assertion that Keller merely
describes one method of describing a pre-characterized current model, “not
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the only method that will work with or is required by the Keller
methodology” (Ans. 14). Keller states at Section 3 that its pre-characterized
current model is a “major component” of the proposed methodology (p.
149).
Because we find that the Examiner’s proposed modification of Keller
would require a change in Keller’s principle of operation, we find that the
teachings of Keller in combination with Barford are not sufficient to render
claims 1, 4, 6-8, 10, 11, 13-16, and 21 prima facie obvious. We will not
sustain the Examiner’s § 103 rejection.
CLAIMS 2, 3, 5, 12, AND 18
These claims variously depend from independent claims 1, 11, and 16.
As explained above, we do not sustain the rejection of those claims. We
have reviewed Lee and Oppenheim, and we find that they do not remedy the
deficiencies of Keller in combination with Barford. Thus, we will not sustain
the Examiner’s § 103 rejections of claims 2, 3, 5, 12, and 18, for the reasons
expressed with respect to claims 1, 11, and 16.

CONCLUSIONS
1. The combination of Keller and Barford does not teach or fairly
suggest automatically calculating a current in a model for a circuit cell as a
function of an input voltage, an output voltage, and a history of at least one
of the current, voltage, and charge values of the model.
2. The Examiner’s proposed modification would require a change in
the principle of operation of Keller.

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ORDER
The Examiner’s rejection of claims 1-8, 10-16, and 18-21 is reversed.

REVERSED

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