Bdo. Anderson et Id. Landau, LEAST-SQUARES IDENTIFICATION AND THE ROBUST STRICT POSITIVE REAL-PROPERTY, IEEE transactions on circuits and systems. 1, Fundamental theory andapplications, 41(9), 1994, pp. 601-607
Certain problems of adaptive systems revolve round finding a transfer
function q(s) (which is not proper) such that a set of transfer functi
ons q(s)/b(s) - 1/2 is strictly positive real for all polynomial b(s)
in a certain set. This paper treats this and some related problems.