A 2-TRACK MATCHED SPECTRAL-NULL CODE WITH RATE 3 4 FOR THE BINARY DICODE CHANNEL/

Matched spectral-null modulation codes were recently introduced as a m ethod to improve the reliability of digital data storage in digital re cording systems. These codes are also dedicated to noisy partial-respo nse channels with input alphabet of finite size. We present here a two -track matched spectral-null code of rate 3/4 derived from the cross p roduct of two canonical diagrams that characterize sequences with a sp ectral null at zero frequency. This code provides a 3 dB distance gain over the dicode channel and limits to 1 the maximum runlength of zero samples at the output of the channel. It is also designed to perform simple two-track by two-track maximum-likelihood detection in the pres ence of severe additive intertrack interference. Its implementation in corporates a 4-state encoder, a 12-state Viterbi detector and a state- independent sliding-block decoder.