Implicit Servo Channel Coding
Original Publication Date: 1985-Aug-01
Included in the Prior Art Database: 2005-Feb-19
In a read-only data storage system which uses a servo mechanism on the recording medium to keep the read head on the track, the servo signal can be an AC signal encoded on the data, using a special implicit servo channel code or, in other words, the servo can be generated by encoding the data using a code with an AC component. One simple such code is a block code, mapping 2 bits of data onto 6 bits of code. data code spectral contribution 00 ++-+-+ 1 +w -w2 -1 +w -w2 = 2 01 ++--+- 1 +w -w2 +1 -w +w2 = 2 10 +-+--+ 1 -w +w2 +1 +w -w2 = 2 11 -+---+ -1 +w -w2 +1 +w -w2 = 2 where w is the 6th root of 1 in the first quadrant, w2=w*w. Note that w**3=-1, w**4=-w, w**5=-w2, w-w2=1.