The Effects of Cable Impedance Irregularities on Baseband Digital Coaxial Systems

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.