A run-length limited coding algorithm with DC control

Describes a simple coding algorithm suitable for rotary-head digital magnetic recording channels. Under this method, a family of run-length limited (RLL) modulation codes for (1-D) channels (i.e. precoded by NRZ-I rules) and (1-D²) channels (i.e. precoded by interleaved NRZ-I rules) can be generated. For high-density recording, signal-to-noise ratio is low, jitter and phase shift are large, therefore, a modulation code with large window margin, is important. In the case of guardbandless recording, crosstalk noise from adjacent tracks is relatively high, hence, a small pulse width ratio, is favorable. The authors discuss a few examples of modulation codes constructed using the simple algorithm and show that code rate, pulse width ratio, and low-frequency suppression power can be compromised within the design rules