The executive standard of class VI modules is eia/tia 568b 2-1. The most important parameters are insertion loss, return loss, near end crosstalk, etc.
Insert loss: due to the existence of transmission channel impedance, it will increase the attenuation of high-frequency components of the signal as the signal frequency increases. The attenuation is not only related to the signal frequency, but also related to the transmission distance. As the length increases, the letter
The attenuation of the signal also increases. It is measured by the amount of signal loss along the transmission channel in unit length, and represents the ratio of signal strength from the source transmitter to the receiver.
Return loss: due to the change of impedance in the product, local oscillation will occur, resulting in signal reflection. Part of the energy reflected to the transmitter will form noise, resulting in signal distortion and reduced transmission performance. Such as full duplex kilo
Megagrid will mistake the reflected signal for the received signal, causing fluctuations of useful signals and causing confusion. The less reflected energy means that the impedance consistency of the lines used in the channel is better, the more complete the transmission signal is, and the less noise is on the channel. echo
Calculation formula of loss RL: return loss = transmitted signal ÷ reflected signal.
In the design, the way to solve the return loss parameter failure is to ensure the whole line consistency of impedance and cooperate with the six types of cables with 100 ohm impedance.
For example, the uneven interlayer distance of PCB, the cross-section change of transmission line copper conductor, and the mismatch between the conductors in the module and the six types of cable conductors will cause the return loss parameters to change.
Near end crosstalk (next): next refers to the signal coupling between one pair of lines and another pair of lines in a pair of transmission lines, that is, when one line pair sends a signal, the signal received in another adjacent line pair. This crosstalk signal is mainly due to proximity
Coupled by capacitance or inductance.