A New Approach for Constructing FSSM Modeled Encoders to Satisfy Spectral Constraints

Constrained codes are widely used in digital transmission systems and digital recording systems to generate constrained sequences with properties that comply with the given physical characteristics of the transmission or recording channels. The power spectral density (PSD) of encoded signals often plays an important role in the design of constrained codes. In this article the authors introduce a new approach for constructing finite-state sequential machine (FSSM) modeled encoders to satisfy desired spectral constraints. This approach involves constructing either a Mealy or a Moore FSSM to represent the encoder, and evaluating the state transition probabilities and codeword values in order that the PSD of the encoded signal meets a predefined shape.