Appeal No. 1999-1742
Application No. 08/730,674
from the occupant is received by receiver 809 and fed into
pre-amplifier 811. This reflected or return signal has the same
modulation frequency, 144 MHZ, as the transmitted signal but now
is out of phase with the transmitted signal by an angle x due to
the path that the signal took from the transmitter to the
occupant and back to the receiver. The output from
pre-amplifier 811 is fed to a second mixer 812 along with the
144.15 MHZ signal 3f2. The output from mixer 812 is amplified
and fed into filter 814. The filter 814 eliminates all
frequencies except for the 150 KHz difference or beat frequency
in a similar manner as was done by filter 808. The resulting
150 KHz frequency, however, has a phase angle x relative to the
signal from filter 808. Both 150 KHz signals are fed into a
phase detector 815 which determines the magnitude of the phase
angle x. The phase angle x is used to determine the distance
from the transmitting diode to the occupant. See col. 12, ll.
26-65.
With regard to claims 1 and 9, the examiner acknowledges
(answer, p. 4) that Blackburn does not disclose a step of or
means for mixing signals having a first frequency from the
-8-8
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