A New Active Balun Reflectometer Concept for DC to Microwave VNA Applications

A new reflectometer concept based on a resistive bridge and an active balun is presented. High bandwidth and performance can be achieved by resistive low-loss voltage monitoring structures, inherent symmetry of bridge and waveguide transitions, an optimized resistor geometry for improved source match, and even-mode suppression at the IF instead of using an RF balun. First demonstrators in hybrid microstrip technology are simulated and realized using GaAs FETs and silicon BJTs as active devices.