Appeal No. 98-0130 Page 7
Application No. 08/631,793
The examiner and appellant are also in agreement that
Snow discloses (col. 1, lines 43-48) that it was known in the
prior art to provide amplitude modulation of a carrier signal
with feedback information, both recognizing that Snow’s
invention is directed to pulse position modulation (See Reply
Brief, pages 2 and 3; and Answer, page 4). Accordingly, the
issue is whether it would have been obvious to one of ordinary
skill in the art to have replaced the pulse position circuitry
of Snow with circuitry for modulation of a carrier signal as
noted by Snow to have been known in the art.
We find that Snow discloses (Spec. col. 1, lines 40-47)
that an approach taken was “to amplitude modulate a high
frequency carrier signal with the desired feedback
information. . . However, this latter approach has often
required in addition to a complex integrated circuit, several
“modulating a carrier, as required by claim 1, is not pulse width modulation
(or PWM). Carrier modulation provides continuous, instantaneous feedback of
the error signal, while PWM does not module modulate a carrier and provides
feedback of only sampled error signals.” The examiner’s position (Answer,
page 4) is that “Gillett et al teaches a power converter including
mechanically separable components but not including magnetically coupled
feedback via a modulated carrier.” The examiner further states (Answer, pages
5 and 6) that Snow teaches “pulse width modulation that Snow felt was superior
to modulating a carrier signal.”
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