Fractional hold circuits for the design of positive realness discrete transfer functions

The appropriate use of fractional order holds (/spl beta/ - FROH) of correcting gains /spl beta/ /spl isin/ [-1,1 ] as an alternative to the classical zero and first order-holds (respectively, ZOH, FOH) is discussed related to the positive realness of the associate discrete transfer functions obtained from a given continuous transfer function. It is proved that the minimum direct input-output gain (i.e. the quotient of the leading coefficients of the numerator and denominator of the transfer function) needed for discrete positive realness may be reduced by the choice of /spl beta/ compared to that required for discretization via a ZOH.