ABSTRACT
The zeros of the network determinant are called the natural frequencies. Their locations in the complexfrequency plane are extremely important in that they determine the stability of the network. A network is said to be stable if all of its natural frequencies are restricted to the open left-half side of the complexfrequency plane. If a network determinant is known, its roots can readily be computed explicitly with the aid of a computer if necessary, and the stability problem can then be settled directly. However, for a physical network there remains the difficulty of getting an accurate formulation of the network determinant itself, because every equivalent network is, to a greater or lesser extent, an idealization of the physical reality. As frequency is increased, parasitic effects of the physical elements must be taken into account. What is really needed is some kind of experimental verification that the network is stable and will remain so under certain prescribed conditions. The measurement of the return difference provides an elegant solution to this problem.
