The effects of both random and periodic cable impedance irregularities on the performance of baseband digital coaxial systems are considered. A cable-noise model in which these effects are statistically characterized as Gaussian-like noise is developed and related to system error rate. Based on relationships derived here between the backscattered signal and the attenuation distortion in the forward cable transmission path, the cable noise is then expressed in terms of return loss parameters. As an example of the utility of the resulting expression, a cable-noise criterion is formulated and applied in the assessment of coaxial cables intended for use in a 274-Mbit/s digital repeatered line.

Series representations, as well as exact expressions, are obtained for correlation functions and power density spectra of quantized Gaussian signals transmitted over discrete memoryless channels. The mean-square reconstruction error that results from linear filtering the received samples is expressed in terms of these power density spectra and is then examined.