Appeal No. 2006-1690
Application No. 10/154,185
Regarding claims 11, 12, 14, 18, 19, 21, 23, and 27, appellants argue that
Park does not disclose all elements of the device, method, and medium of
independent claims 11, 14, and 21. Appellants essentially reiterate that Park's
power-based measures ERLE1 and ERLE2 merely indicate how well the filters
21 and 22 perform in canceling echo signals and do not necessarily indicate the
presence or absence of double-talk [brief, page 6]. Appellants also dispute the
examiner's assertion that when ERLE1 is greater than ERLE2 in step 887 in Fig.
8C of Park, such a condition will occur only if no double-talk is present [brief,
page 6]. Appellants also reiterate that Park does not disclose suspending
weights before portions of the first signal are filtered/canceled [id.]. The
examiner responds that during double-talk, the adaptive filter's ERLE drops well
below that of the fixed filter [answer, page 17].
We will sustain the examiner's anticipation rejection of claims 11, 12, 14,
18, 19, 21, 23, and 27. For the reasons stated previously, Park detects double-
talk and suspends replacement of the non-adaptive filter weights before portions
of the first signal are cancelled by the non-adaptive filter.
Regarding claims 20 and 22, appellants argue that Park does not disclose
distinguishing between double-talk and channel impulse response changes [brief,
page 7]. The examiner responds that Figs. 5 and 6 of Park show that the echo
canceller behaves differently in the presence of double-talk compared to echo
path change. Specifically, the examiner contrasts Fig. 5 with Fig. 6 and
emphasizes that only the adaptive filter's ERLE diverges from the true echo path
in Fig. 5, but both filters' ERLE decreases in Fig. 6 thus "signaling a divergence
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