Appeal No. 2006-1777
Application No. 10/206,704
Walker
Claims 14 and 15 are rejected under 35 U.S.C. § 102 as being anticipated by
Walker. (Answer at 5-6.) Appellant contends that Walker lacks an impedance
“mismatch detection circuit.” According to appellant, the current measured in Walker
does not correspond to the mismatch between a reference electrical impedance and an
actual electrical impedance of the sound transducer. (Brief at 12.)
Walker describes an operational amplifier 40 (Fig. 2) that amplifies a difference
signal derived from the output of operational amplifier 30 and the voltage applied to the
loudspeaker system 20. Col. 2, ll. 49-62.
The circuit uses negative current feedback and works as follows. The
current driving the loudspeaker system 20 causes a voltage drop across
the current-sensing resistor 21, which is amplified by the operational
amplifier 30. The gain of the amplifier 30 is chosen so that in operating
conditions in which no mechanical resonances occur in the loudspeaker
system 20, the output voltage of the amplifier 30 is equal in magnitude and
phase to the voltage applied to the loudspeaker system.
Walker col. 3, ll. 5-14.
In our view, Walker’s disclosure provides adequate support for the examiner’s
findings. Operational amplifier 40 has an output corresponding to the mismatch
between a reference electrical impedance (from operational amplifier 30) and an actual
electrical impedance (from loudspeaker system 20) with respect to loudspeaker system
20. We are not persuaded by appellant’s bare assertion that the relevant portions of the
Walker circuit of Figure 2 do not disclose a “mismatch detection circuit” as claimed.
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