Multirate signal processing in Ptolemy

The use of two models of computation, synchronous dataflow (SDF) and dynamic dataflow (DDF), to design and implement signal processing applications with multiple sample rates is discussed. The SDF model is used for synchronous applications. SDF is amenable to compile-time scheduling, and hence is much more efficient at runtime. The design environment, Ptolemy, can simultaneously support multiple models of computation, so SDF and DDF can be combined in a single application. Hence, the implementation will incur the run-time cost of DDF only for those asynchronous portions that absolutely must incur such cost. As an illustration, the authors detail a synchronous application, sample-rate conversion using polyphase filters, and an asynchronous application, timing recovery for an amplitude-shift-keyed signal