A Novel CAD Probe for Bidirectional Impedance and Stability Analysis

Bidirectional impedance probes such as the ADS SProbe2 (Keysight) and the MWO Gprobe2 (AWR) suffer from a loss of accuracy when subjected to feedback across their terminals. Being originally developed to facilitate stability analysis, these traditional probes are actually based on an incorrect conceptual model that lacks the generality needed to provide accurate results when embedded within networks with potentially high levels of feedback. In realistic networks, there can exist layers of intentional and unintentional feedback paths around your active devices and across the probes used to compute in-situ bidirectional impedances and assess local stability. It is critical, therefore, that the bidirectional impedance probe is capable of providing accurate results under the most extreme feedback conditions. To this end, a novel CAD probe has been developed that is based on a simple, but general model of feedback and is accurate when subjected to arbitrary levels of feedback across its terminals and can be used to accurately determine both in-situ bidirectional impedances and local loop stability.