Vector network analyzers (VNA) are instruments that measure the magnitude and phase of signals as they pass through and/or are reflected from devices under test (DUTs). Typically, a DUT is connected to the VNA at connectors with short lengths of cable; however, there are some applications where the connectors of the DUT are very far away, and it is not feasible to connect the DUT connectors to the VNA with test port cables. For instance, if the DUT is coaxial cable installed in a building, one end of the cable may be hundreds of meters away from the other. The DUT could also be a radio link with transmitting and receiving antennas positioned very far apart.
There is a need for network analyzers capable of measuring transmission magnitude and phase (s21) through DUTs that have input and output ports very far apart.