Appeal No. 2000-1259
Application 08/815,894
Figures 2A and 2B, each radial servo spoke 17 on the disk
contains recorded servo control information consisting of a
preamble 5 to allow the gain control circuitry to acquire the
read signal, a servo sync mark 7 to signal the beginning of the
servo data, and the servo data 3. Id. at 9, ll. 3-10. The
specification further explains that "[s]imilar to the servo data
sectors, the user data sectors 15 also comprise an acquisition
preamble 68 and a sync mark 70 to signal the beginning of a user
data field 72 as shown in Figure 2B." Id. at 10, ll. 3-5.
The prior-art sampled amplitude read channel illustrated by
Appellants' Figure 1 includes a gain control circuit 50, a timing
recovery circuit 28, a DC offset circuit 1, and a discrete time
sequence detector 34. Appellants' brief explains that the gain
control, timing recovery, and DC offset circuits are decision-
directed feedback loops whose coefficients are adjusted depending
on whether the read channel is reading a preamble field or a data
field. Brief at 2. Specifically, when reading the preamble
field, the loop bandwidth is increased to provide a fast
transient response in order to minimize the time and number of
bits required to obtain the preamble field; when reading the data
field, the loop bandwidth is decreased to attenuate noise and
gain variance. Id. at 2-3. Furthermore, the discrete time
sequence detector comprises a large buffer for storing a survivor
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