Isolation of a splitter or directional coupler is measured with respect to which port?

Isolation in the context of a splitter or directional coupler refers specifically to the ability of the device to prevent signal leakage from one port to another. When assessing isolation, the measurement is commonly taken with respect to the common port. This is because the common port serves as the primary point where the signals are either combined or split, and it is essential to assess how much the signals from the other ports interfere or affect the common port.

By defining isolation in relation to the common port, it is possible to determine how effectively the device maintains separation between the different pathways of signal transmission. This measurement is critical in applications where maintaining signal integrity is paramount, as any unwanted signal leakage could lead to interference and degradation of performance in network systems.

The common port becomes the reference point for measuring isolation, as it helps in determining the efficiency of the device in segregating outputs and minimizing interference between the various ports.