Characterising Stability Implying Properties that are Preserved under Feedback

The passivity approach to the design of large networks is based on preserving the passivity property under different types of interconnection: parallel and negative feedback. Since the passivity property implies stability, this allows large and topologically complex networks to be constructed on the basis of simple local rules without the need for global stability analysis. In this paper we characterise two different stability implying properties that are preserved under negative feedback. The first generalises the passivity approach to electrical network design to other classes of minimum phase impedance functions. The second allows for networks with, for example, Laplacian structures in the feedback loop, to be designed using only local models.