BS EN 50289-1-11 is a safety standard on communication cables.
BS EN 50289-1-11 details the test methods to determine characteristic impedance, input impedance and return loss of cables used in analogue and digital communication systems.
BS EN 50289-1-11 is to be read in conjunction with EN 50289-1-1, which contains essential provisions for its application.
BS EN 50289-1-11 on characteristic impedance, input impedance, return loss is relevant to:
In practice for real cables which always have structural variations, the characteristic impedance is described by the mean characteristic impedance which is derived from the measurement of the velocity of propagation (EN 50289-1-7) and the mutual capacitance (EN 50289-1-5).
BS EN 50289-1-11 describes the method which is only applicable for frequencies above 1 MHz and non-polar insulation materials (i.e., materials having a dielectric permittivity that does not change over frequency). The mean characteristic impedance approaches at sufficiently high frequencies (≈100 MHz) an asymptotic value Z∞. The characteristic impedance is expressed as the propagation coefficient divided by the shunt admittance. BS EN 50289-1-11 also assists the user with input impedance which is measured at the near end (input) when the far end is terminated with its own impedance. In practice, this is the case when the round-trip attenuation is greater than 40 dB at any measured frequency. This property considers structural variations in the cable. BS EN 50289-1-11 provides guidance on return loss which is measured at the near end (input) when the far end is terminated by a load resistance of value equal to the system nominal impedance ZR. It quantifies the reflected signal caused by impedance variations. The (operational) return loss considers the structural variations along the cable length and the mismatch between the reference impedance and the (mean) characteristic impedance of the cable (pair).
Overall, BS EN 50289-1-11 is useful as it aids with the method that is applied for cables having non-polar insulation materials (e.g., PE, PTFE), i.e., materials having a dielectric permittivity that does not change over frequency. Or in other words, this method is applied to cables having a mutual capacitance that does not change over frequency.
EN 50289-1-11:2016