公开(公告)号：CA961117A

公开(公告)日：1975-01-14

申请号：CA130470

申请日：1971-12-20

Applicant: IBM

Inventor： SHA RICHARD T ,  TANG DONALD T

IPC: H04L25/03

Abstract: An automatic equalizer with extremely fast convergence is disclosed. The weight setting procedure or algorithm is basically an iterative operation which can be conveniently expressed by cascaded equalizers. One form of the apparatus utilized consists of a plurality of equalizer stages which have their tap settings changed after successive iterations (the first iteration adjusts the first equalizer stage, the second iteration adjusts the second equalizer stage and so on) such that after n iterations a given initial distortion D is reduced to at most D2 . The algorithm involved and the method of operating the equalizer is also disclosed.

公开(公告)号：CA951425A

公开(公告)日：1974-07-16

申请号：CA100733

申请日：1970-12-16

Applicant: IBM

Inventor： KOBAYASHI HISASHI ,  TANG DONALD T

IPC: H03M7/00 ,  G11B20/10 ,  G11B5/09

Abstract: A digital magnetic recording system which uses conventional NRZI coding and a readback channel of conventional design operates, in effect, as a precoding and correlative level coding process that is characterized by a transfer function of 1-D (where "D" is a delay operator). Under these conditions, the minimum spacing that can be permitted between adjacent digit symbols in the magnetic recording medium without incurring excessive intersymbol interference during readback is rather large and severely limits the recording density. The present invention uses interleaved NRZI coding and a special filter in the readback channel to provide a precoding and correlative level coding scheme characterized by a transfer function 1-D2. This mode of operation permits much denser packing of the data in the recording medium without causing excessive intersymbol interference during readback.

公开(公告)号：CA762119A

公开(公告)日：1967-06-27

申请号：CA762119D

Applicant: IBM

Inventor： TANG DONALD T