Methods of test waveform synthesis for high speed data communication devices

When testing ISDN (integrated services digital network) and other high-data-rate communications devices, stimulus waveforms will often emulate signals that a device under test (DUT) will process in its final application. When conventionally architected digital-signal-processor-based instrumentation is used to provide these waveforms, there exist test conditions which can easily overburden machine capabilities. The author explores an instrument architecture in use, based on a composite test signal model, which provides for extremely efficient generation of combinational analog/digital test stimuli. This technique is suitable for transmitting extremely long data sequences to DUTs using a hardware modulator scheme which mixes the logical and physical components of a mixed-signal waveform at run time. The limitations of this technique are concerned with to what extent the length of the filter can be implemented; these limitations, however, can be overcome with either additional processing or hardware filters