  In this paper we present a new approach towards global passive approximation
in order to find a passive transfer function G(s) that is nearest in some
well-defined matrix norm sense to a non-passive transfer function H(s). It is
based on existing solutions to pertinent matrix nearness problems. It is shown
that the key point in constructing the nearest passive transfer function, is to
find a good rational approximation of the well-known ramp function over an
interval defined by the minimum and maximum dissipation of H(s). The proposed
algorithms rely on the stable anti-stable projection of a given transfer
function. Pertinent examples are given to show the scope and accuracy of the
proposed algorithms.
