Electronics plays a vital role in each of the
subsystems inside a disk drive. Signals to and
from the head-disk assembly are processed mainly
by the preamplifier (read/write amplifier) and
the channel chips. Overall control and interface
to the outside world are performed by a combination
of the microprocessor and the controller, supported
by attached memory. The controller chip also
handles the very important function of error
correction during data recovery from the disk.
For high performance drives, an additional digital
signal processor is required to help the microprocessor
speed up calculation of the servo information.
As their names indicate, the spindle motor and
the actuator controllers handle the main components
of the mechanical subsystem.
At Hitachi San Jose Research Center, research
is conducted on the entire signal path, both
on algorithm development and on hardware implementation.
This research has resulted in high-performance
preamplifier designs, advanced data detection
channels, and efficient error-correction methods.
A main objective is to assure continued data
recovery reliability while supporting high data
rates and lowest possible power dissipation.
These objectives must also be consistent with
aggressive low-cost requirements of the disk
drive industry, which is characterized by rapidly
decreasing cost per megabyte of storage. Signal
processing research is closely coordinated with
recording head,recording physics and architecture
for disk drives activities to achieve an optimized
high-capacity, high-performance design.
