Some Necessary Conditions for a Non-Negative Unit Impulse Response and for a Positive Real Immittance Function

Abstract
The fact that the unit impulse response of a network is non-negative imposes certain conditions on the real part of the transfer or immittance function. Such conditions are derived in this paper. In addition, when the real part of the immittance function is non-negative, necessary conditions are imposed upon the impulse response. Such conditions are also presented here. These conditions are in a graphical form, which can be utilized without the necessity of lengthy calculations.