Encoders and decimation filters for superconductor oversampling ADCs

Modulators of superconductor ADCs can operate at very high sampling rates, ranging from 20 GHz (today's technologies) to 400 GHz (prospective sub-micron technologies). Such devices are too fast and therefore impractical without other superconductor devices capable of processing the data streams at such rates. We discuss various structures of such devices, in particular demultiplexers and decimation filters. We also analyze possible hybrid devices, in which only the front stages contain superconductor components. Encoders and decimation comb filters for single-comparator and time-interleaved modulators were designed, fabricated (at HYPRES, Inc.) and successfully tested. The most recent designs of the decimation filters have a unique modular structure, which allows an assembly of various comb filters handling clock frequencies of about 20 GHz (for a 1 kA/cm/sup 2/ fabrication technology).