Voltage and Current Measurements With a VNA and DMM

Vector Network Analyzers (VNAs) are used to measure the reflection and transmission coefficients, or S-parameters, of a Device Under Test (DUT). When the DUT is passive, the VNA may be the only tool necessary. But some devices are active and require an external power source for operation. In such active applications, it may be useful to perform voltage or current measurements of the DUT as the VNA generator sweeps over frequency or power.

For example, characterization of a log amplifier may involve measurement of the detector’s output voltage synchronously with measurement of its S11 Return Loss. An amplifier manufacturer can simultaneously measure the gain and current draw of an amplifier DUT while the VNA sweeps its transmitter through various RF power levels and frequencies. Generally, the measured voltage and current will depend on the RF frequency, RF input power, and DUT temperature, each of which can be monitored and plotted against the supplied voltage or current.