Comments on “A Note on Spectral Conditions for Positive Realness of Single-Input-Single-Output Systems With Strictly Proper Transfer Functions”

The necessary and sufficient conditions for (strict) positive realness of strictly proper transfer functions are derived in the above-mentioned paper [1]. Presenting a counter-example, we show that there are inconsistencies between definitions stated in Section II and main results proved in section III of [1]. Also, the required corrections in the main results of [1] are presented. Note however that the results in [1] are correct for the definition of SPR in the Circuit Theory sense.