Cross Talk / NEXT FEXT

Noise that one signal line receives from another signal line in multiplex signal transmission/multiplex transmission line. The name of the telephone communication era remains as it is, and in Japanese it is called cross talk. The unit is mainly dB, which is the ratio of the magnitude of the original signal (20log[V1/V2] or 10log[w1/w2]).

Near-end crosstalk = NEXT when the noise source and observation end are on the same side, and far-end crosstalk = FEXT when they are on opposite ends. The main factor is the coupling between lines, but it also increases due to reflection due to disturbance of characteristic impedance, so it is important to reduce impedance disturbance, especially in high-speed transmission connectors.