Frequency response of generalized sampled-data hold functions

Alternatives to the zero order hold known as generalized sampled-data hold functions have been proposed by several authors. More recently, it has been noticed that these new holds incur intersample behavior penalties in many cases. In studying such behavior, one of the issues of relevance is the "frequency response" of the hold; for example, it is known that "nonminimum phase" zeros of the hold impose design tradeoff in the continuous-time response to disturbances of the sampled-data system. This paper goes deeper into the analysis of the frequency response of these devices, and provides some preliminary results on zero location and integral constraints satisfied by the hold. We give a number of circumstances in which nonminimum phase zeros may occur and, furthermore, we show that holds with zeros off the j/spl omega/-axis will tend to have poor frequency responses properties.