Two-Level Block Encoding for Digital Transmission

Communication channels with no transmission at dc require data encoding to eliminate dc from the signal. Many coding schemes have been developed for this purpose. The scheme discussed here uses code blocks with equal numbers of plus and minus pulses, according to a previously published algorithm. This code is compared to a three-level "bipolar" coding scheme in terms of spectral characteristics, efficiency, crosstalk noise, power requirements, and hardware requirements. Circuitry is described for coders, decoders, and repeaters. Extensions to other code types are discussed briefly.