Multirate sampling techniques are used to sharpen and extend the concept of "frequency response" for discretely excited continuous systems. Frequency response, in this case, pertains to steady-state response of continuous variables at the input frequency and its positive aliases. Simple expressions are given for computing the amplitude ratios and phase angles as a function of these frequencies. Results are presented in terms of the familiar Bode plot. This Bode plot must be interpreted in a novel way, however. Similar expressions, appropriate for interpreting frequency response data obtained from sampled records of continuous responses, are also given. These frequency response methods apply for analysis of both open-loop and closed-loop discretely controlled continuous system responses, and are useful for assessing intersample ripple effects. M(s) s T w w' z z