Abstract
Most of the commercially available vector network analyzers have a high pass cut-off frequency in the higher kHz-range. One of the main reasons is the frequency limitation of the directional device used. In this paper, a simple directional bridge circuit with incorporated frequency conversion stage is presented. This DC-coupled circuit enables vector network analyzer receiver front-ends to work near DC, expanding the frequency range by several decades. The directivity is similar to these of directional bridges used in commercially available analyzers, but this in a frequency range down to DC.
