Design and realization of continuous-time wave digital filters

Digital signal processing in continuous-time can result in a number of advantages compared to classical sampled data systems, while the inherent advantages of digital implementations with respect to programmability and noise immunity are retained. It turned out however that a critical point of these systems is the implementation of the continuous-time delays, requiring a considerably larger chip area than the delays in sampled data systems. Thus structures with a minimum number of delay elements seem to be advantageous. In this contribution the implementation of continuous-time wave digital filters (WDFs) is considered. This filter type is well-known for its superior properties with respect to stability and sensitivity. Furthermore, by selecting a proper reference structure, WDFs can be implemented with a minimum number of delay elements for a given filter specification thus making them very attractive for continuous-time implementations. Due to the proposed concept a number of advantages are obtained and a very efficient realization in VLSI-technology becomes feasible.