Appeal No. 1999-1935
Application No. 08/754,270
Miyakoshi is concerned with specific spectrum characteristics. As to Ahamed, appellants
contend that this reference does not even relate to a sigma-delta modulation or a “one-bit
encoding system” [brief-page 7]. Appellants also contend that Ahamed originated at a
time prior to the development of one bit encoding systems.
Therefore, conclude appellants, the skilled artisan would not have been led to
modify the muting signal in Miyakoshi to provide spectrum characteristics that would
correspond to the stop-band frequencies of the low-pass filter of Miyakoshi based on the
“rather obscure description of the silence sequence in Ahamed at column 3, lines 6
through 25" [brief-page 8].
While we might agree with the examiner that it would have been obvious to put a
filter at the output terminal of Nishio, we agree with appellants that there would appear to
be no reason for the skilled artisan to have made the other modifications proposed by the
examiner. In accordance with the language of the claims, the finite impulse response (FIR)
filter means is chosen first and then the muting pattern signal is selected such that its
spectrum characteristics coincide with a plurality of stop-band frequencies of the FIR filter
and to include stop-band frequencies below a cut-off frequency of ½ Fs of the FIR filter
means. The examiner has made no showing that
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