Title: Recoverable Energy of Dissipative Electromagnetic Systems,
Abstract: Ambiguities in the definition of stored energy within distributed or
radiating electromagnetic systems motivate the discussion of the well-defined
concept of recoverable energy. This concept is commonly overlooked by the
community and the purpose of this communication is to recall its existence and
to discuss its relationship to fractional bandwidth. Using a rational function
approximation of a system's input impedance, the recoverable energy of lumped
and radiating systems is calculated in closed form and is related to stored
energy and fractional bandwidth. Lumped circuits are also used to demonstrate
the relationship between recoverable energy and the energy stored within
equivalent circuits produced by the minimum phase-shift Darlington's synthesis
procedure.