Ex Parte Golden et al

Board of Patent Appeals and Interferences

Aug 28, 2009

10958473 (B.P.A.I. Aug. 28, 2009)

UNITED STATES PATENT AND TRADEMARK OFFICE
____________

BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
____________

Ex parte STUART A. GOLDEN and NAIEL K. ASKAR
_____________

Appeal 2009-000110
Application 10/958,473
Technology Center 2800
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Decided: August 28, 2009
____________

Before JOSEPH F. RUGGIERO, ROBERT E. NAPPI,
and ELENI MANTIS MERCADER, Administrative Patent Judges.

MANTIS MERCADER, Administrative Patent Judge.

DECISION ON APPEAL

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STATEMENT OF THE CASE
Appellants seek our review under 35 U.S.C. § 134(a) of the Examiner’s final
rejection of claims 1-3, 5, 12-14, 16, 23-25, 27, 34-36, 38, and 40-43. We have
jurisdiction under 35 U.S.C. § 6(b).
We affirm.

INVENTION
Appellants’ claimed invention is directed to interference reduction by
correcting the offset of a received signal, wherein the offset may be modeled as
including a step function and the signal is corrected by removing the undesired step
function (Spec. 3:10-13).
Claim 1, reproduced below, is representative of the subject matter on appeal:
1. A method comprising:
observing a finite duration signal yn that comprises a representation of
a mixture of a desired signal and an undesired signal, the undesired signal
comprising an offset component based on time-variant interference of an
external interference source, the desired signal carrying information;
modeling the offset component of the undesired signal as comprising
a step function u defined by unknown step function parameters;
estimating the unknown step function parameters based on the
observations of finite duration signal yn; and
adjusting yn based on the estimated step function parameters.

THE REJECTIONS
The Examiner relies upon the following as evidence of unpatentability:
Chen US 2002/0197975A1 Dec. 26, 2002
(filed May 18, 2001)
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Kim US 2003/0109241A1 Jun. 12, 2003
(filed Dec. 12, 2001)

The following rejections are before us for review:
The Examiner rejected claims 1-3, 5, 12-14, 16, 23-25, 27, 34-36, 38, and
40-43 under 35 U.S.C. § 103(a) as being unpatentable over Chen.
Appellants argue the art rejection of claims 1-3, 5, 12-14, 16, 23-25, 27, 34-
36, 38, and 40-43 as a group with independent claims 1, 12, 23, and 34 as
representative (App. Br. 9-15).1 Accordingly, claims 2-3, 5, 13-14, 16, 24-25, 27,
35-36, 38, and 40-43, stand or fall with claims 1, 12, 23, and 34. See 37 C.F.R.
§ 41.37 (c)(1)(vii) (2004). We note that the Examiner withdrew the rejections
made under 35 U.S.C. § 101 (Ans. 8), and thus, we do not address Appellants’
arguments with respect to these rejections (Br. 16-20).

OBVIOUSNESS
ISSUE
With respect to claims 1, 12, 23, and 34, Appellants assert that Chen is
directed to the calibration of a receiver (Br. 9). Appellants also assert that Chen’s
receivers have different DC offsets associated with different gain settings, and
Chen seeks to determine the magnitude of these offsets for different gain settings
of the receiver, and then cancel the offsets (Br. 9). Appellants argue that Chen’s

1 Only arguments made by Appellants have been considered in this decision.
Arguments which Appellants could have made but did not make in the Brief have
not been considered and are deemed waived. See 37 C.F.R. § 41.37(c)(1)(vii)
(2004).
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gain settings and their associated offsets are internal to the receiver and unrelated
to the properties of any external signal (Br. 9-10). Appellants assert that Chen
describes that the calibration “is preferably not performed while a signal is being
received” (Br. 10).
Appellants argue that it would not have been obvious to one skilled in the art
to turn to receiver calibration techniques to adjust a signal that includes a
representation of a mixture of an undesired signal and a desired signal carrying
information (Ans. 10).
Appellants further argue that Chen intentionally selects periods when no
information of interest is received to make the observations necessary for
estimating the alleged unknown step function parameters (Br. 12). Appellants
argue that this is contrary to an estimation of unknown step function parameters
based on the observations of a finite duration signal that comprises a desired signal
carrying information of interest (Br. 12).
Appellants further argue that the superposition of Kim’s unknown DC
offsets with Chen’s known offsets will yield an unknown DC offset and Chen’s
receiver cannot calculate the system response parameters a, b, and c using
unknown DC offsets (Br. 14).
The Examiner responds that Chen in paragraph [0005] teaches that the DC
offset is caused, for instance, by current leakage from the local oscillator, which
suggests that the DC offset is due to external interference (Ans. 5). The Examiner
further finds that Chen is concerned with canceling DC offset in a way that at least
takes local oscillator leakage into consideration (Ans. 5).
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The Examiner further finds that Kim in paragraph [0040] teaches, “factors
that cause the DC offset component, e.g., external interference, local oscillator
leakage, etc.” (Ans. 5). The Examiner concludes that since Chen is concerned with
canceling DC offset, one of ordinary skill in the art at the time of invention would
have recognized the benefits of modification of Chen to cancel DC offset that was
a function of external interference, local oscillator leakage, inter alia, as addressed
in the rejection (Ans. 5).
The Examiner also finds that in paragraph [0051], Chen teaches,
“[c]alibration according to the present invention may be performed while a signal
is present in the receiver” and in paragraph [0052], Chen further teaches that it is
preferable to perform the calibration algorithm “only when signals carrying data of
interest are not being received” (Ans. 6). The Examiner contends that Chen
teaches that performing the algorithm while the signal is being received “may
cause data corruption and/or increased error rate” and that one solution to properly
time the performance of the algorithm is to perform the calibration between bursts
of data being transmitted to the receiver (Ans. 6). The Examiner concludes that the
discussion above essentially supports that the desired signal of Chen actually
involves data of interest and therefore, the method of invention carefully ensures
that the timing of the application of the calibration algorithm is applied in a way
that attempts to prevent data corruption and increased error rate (Ans. 6).
The issue, then, is whether the Appellants have shown that the Examiner
erred by finding that Chen in combination with Kim teaches the limitation of: “the
undesired signal comprising an offset component based on time-variant
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interference of an external interference source, the desired signal carrying
information” recited in claim 1, and similarly recited in claims 12, 23, and 34.

FINDINGS OF FACT
The following relevant findings of fact (FF) are supported by a
preponderance of the evidence:
1. Chen teaches that “the occurrence of the calibration cycle should be
controlled so that calibration is performed only when signals carrying data of
interest are not being received . . . and calibration may be performed
between data bursts” (¶ [0052]).
2. Chen teaches that “[c]alibration according to the present invention may be
performed while a signal is present at the receiver” (¶ [0051]).
3. Chen teaches that the undesired DC offset is removed when a signal is
present at the receiver (¶¶ [0051] and [0052]).
4. Chen teaches that the invention pertains to a calibration method that is
effective in the presence of a time-varying system response to an abrupt
change in an input (¶ [0008]).
5. Chen teaches that the receiver 100 has an antenna 102 for receiving an
external RF signal (¶ [0022]; Fig. 1) which is mixed with a local oscillator
signal (¶ [0022]).
6. Chen recognizes that DC offset appears at the mixer output and that one of
the causes of the DC offset is leakage from the local oscillator to the mixer
(¶¶ [0005], [0006]).
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7. Chen teaches that the DC offset correction can be performed by the
capacitors 112a, and 112b (¶¶ [0022], [0006], [0007]), and that gain
correction may cause an additional abrupt change to “the DC offset” that is
not immediately filtered out by the capacitors (¶¶ [0007], [0024]) leading to
the need for calibration (¶ [0008]) of the gains so as to correct the DC offset.
8. Kim teaches that factors that cause DC offset component include external
interference and local oscillator leakage (¶ [0040]) and that such interference
is time-variant (¶ [0006], [0008], and [0014]).

PRINCIPLES OF LAW
The Examiner bears the initial burden of presenting a prima facie case of
obviousness, and Appellant has the burden of presenting a rebuttal to the prima
facie case. In re Oetiker, 977 F.2d 1443, 1445 (Fed. Cir. 1992). Appellant has the
burden on appeal to the Board to demonstrate error in the Examiner’s position. See
Kahn, 441 F.3d at 985-86.

ANALYSIS
At the outset, we note that Appellants’ assertion that Chen describes that the
calibration “is preferably not performed while a signal is being received” (Br. 10)
is over inclusive. Chen teaches that “the occurrence of the calibration cycle should
be controlled so that calibration is performed only when signals carrying data of
interest are not being received” and in between data bursts (emphasis added) (FF
1). Thus, the calibration is not done when the data signals are being received, but
that does not mean that calibration is prevented when a signal that does not contain
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the data is present at the receiver (i.e., a signal devoid of bursts of useful data). As
stated in Chen, “[c]alibration according to the present invention may be performed
while a signal is present at the receiver” (FF 2). Thus, Chen teaches that
calibration is performed when a signal is present at the receiver and in between the
signals carrying data of interest (FF 1-2). Furthermore, the undesired DC offset is
removed when a signal is present at the receiver (i.e., absent a signal carrying data
of interest) (FF 3). Accordingly, Chen teaches “a representation of a desired signal
carrying information” (i.e., signal carrying data) and an “undesired signal
comprising an offset component” (i.e., signal present at the receiver and in between
data bursts). Note, that nothing in the claim language requires that the two types of
signals (i.e., signals with and without useful data) are processed
contemporaneously. Thus, we are not persuaded by Appellants’ argument that
Chen’s invention is contrary to an estimation of unknown step function parameters
based on the observations of a finite duration signal that comprises a desired signal
carrying information of interest (Br. 12), because the claims do not require that the
these parameters are being determined contemporaneously with the desired signal
carrying information.
Furthermore, Chen teaches that the invention pertains to a calibration
method that is effective in the presence of a time-varying system response to an
abrupt change in an input (FF 4). Thus, the claim language of an “offset
component based on time-variant interference” is met by Chen’s calibration
method which pertains to a correction of the DC offset in the presence of “a time-
varying system.” The question remaining to be answered is whether that
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interference is based on “an external interference source” as required by claims 1,
12, 23, and 34.
Chen teaches that the receiver 100 has an antenna 102 for receiving an
external RF signal which is mixed with a local oscillator signal (FF 5).
Furthermore, Chen recognizes that DC offset appears at the mixer output and that
one of the causes of the DC offset is leakage from the local oscillator to the mixer
(FF 6) (i.e., leakage of the external signal causing external DC offset interference).
Chen teaches that the DC offset correction can be performed by the capacitors
112a, and 112b and that gain correction may cause an additional abrupt change to
“the DC offset” that is not immediately filtered out by the capacitors leading to the
need for calibration of the gains so as to correct the DC offset (FF 7). Thus, we
agree with the Examiner (Ans. 5) that Chen’s DC offset is caused, for instance, by
current leakage from the local oscillator (i.e., caused by external interference). In
other words, while the DC offset is further abruptly changed by gain control, the
underlying reason for that DC offset is the leakage of the external RF signal from
the oscillator, and as such the undesired DC offset signal is based on time-variant
interference of an external interference source.
Furthermore, Kim teaches that factors that cause DC offset component
include external interference and local oscillator leakage and that such interference
is time-variant (FF 8). Chen is concerned with eliminating the DC offset, and thus,
it would have been obvious to one skilled in the art that Chen’s method would
remove that DC offset component whether caused internally or externally and as
such apply the method to situations where the DC offset was caused by external
interference as explained by the Examiner (Ans. 4 and 5). Therefore, even if we
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were to agree with Appellants that the source of the interference is internal rather
than external (Br. 9-10), Chen’s teaching value is the removal of the DC offset
component, and one skilled in the art would recognize that the method could be
extended to removing externally rather than internally caused interference.
Accordingly, Chen in combination with Kim teaches the limitation of: “the
undesired signal comprising an offset component based on time-variant
interference of an external interference source, the desired signal carrying
information” recited in claim 1, and similarly recited in claims 12, 23, and 34.
For the foregoing reasons, Appellants have not persuaded us that the
Examiner erred in rejecting claim 1 and claims 2-3, 5, 12-14, 16, 23-25, 27,
34-36, 38, and 40-43 which fall with claim 1.

CONCLUSION
Under 35 U.S.C. § 103, Appellants have not shown that the Examiner erred
by finding that Chen in combination with Kim teaches the limitation of: “the
undesired signal comprising an offset component based on time-variant
interference of an external interference source, the desired signal carrying
information” recited in claim 1, and similarly recited in claims 12, 23, and 34.
Similarly, Appellants have not persuaded us that the Examiner erred in rejecting
claims 2-3, 5, 13-14, 16, 24-25, 27, 35-36, 38, and 40-43 which fall with claims 1,
12, 23, and 34.

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ORDER
The decision of the Examiner to reject claims 1-3, 5, 12-14, 16, 23-25,
27, 34-36, 38, and 40-43 under 35 U.S.C. § 103, is affirmed.
No time period for taking any subsequent action in connection with this
appeal may be extended under 37 C.F.R. § 1.136(a)(1)(iv).

AFFIRMED

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