Exploring the ability of oscillation based test for testing continuous-time ladder filters

In this work, we present an exploratory study on the ability of oscillation-based test (OBT) for testing continuous-time low-pass ladder filters. Particularly, fifth and seventh order Butterworth and elliptic filters are addressed. We devote our effort in determining the efficiency of OBT for detecting deviation-faults in the filters components, using signal-flow graphs for modeling the filters. For implementing the OBT oscillators, we use non-linear elements in the feedback paths. The describing function approach is adopted for the mathematical treatment of the nonlinear elements. Additionally, the oscillation conditions are established with a very good precision using Bode plots. For characterizing our OBT schemes, we inject arbitrary deviation-faults and then establish the fault coverage. An alternative approach is also suggested in the paper, based in the assessment of the lowest deviations in each circuit parameter able to be detected using the proposed oscillators. In this way, it is possible to determine the hard-to-verify components