Appeal No. 1999-1935
Application No. 08/754,270
The examiner cites Miyakoshi for its disclosure of a delta-sigma modulator in
Figure 15 and an idle signal generator with a selection made between them responsive to
a muting signal, citing column 7, lines 55-61 for the suggestion that the muting signal
may be any frequency as long as the pulse signal has a 50% duty cycle, thus limiting
suitable idling signals.
Finally, the examiner relies on Ahamed, column 3, lines 15-25, for the teaching of
silence sequences that generate components at the harmonic frequencies as one “would
expect” [brief-page 3].
Appellants’ response is that Nishio has no filter in the output signal corresponding
to the analog FIR filter 5 of the instant application and that Ahamed relates to a noise
suppression circuit for a delta modulation speech encoding system with no filter in the
encoded signal output line.
Moreover, appellants point out, in the instant claimed invention, the frequency
characteristics of the muting pattern signal are specifically chosen so that the spectrum
characteristics of the muting pattern signal coincide with a plurality of stop-band
frequencies of the finite impulse response filter which exist below the cut-off frequency of
the low-pass filter. The position of appellants is that, clearly, neither Nishio nor
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