Broadband Interfacing of Superconducting Digital Systems to Room Temperature Electronics

We have developed and tested simple and inexpensive electronics for interfacing Rapid Single-Flux-Quantum (RSFQ) Josephson-junction circuits to room temperature digital systems. Voltage-level (Non-Return-to-Zero) bit signals with a swing of ~150 uV, developed on-chip by standard SFQ/DC converters, and in some cases amplified to 1.5mV swing by HUFFLE-type circuits, are passed to the 300K environment using a high density (40 channel) flexible coplanar waveguide assembly. AC-coupled, 2-3 stage microwave Si-biploar amps, and Emitter-Coupled-Logic (ECL) buffers accomplish voltage level translation to the standard ECL levels. Using this technique, data rates in excess of 1Gb/s per channel can be achieved at low cost per channel.