New design of single-bit all-digital RSFQ autocorrelator

We present a new design of a Rapid Single-Flux-Quantum all-digital one-bit autocorrelator for submillimeter spectrometry applications, featuring 4 GHz input signal bandwidth, double oversampling quantizer, and 16 Mbps-per-channel output rate. The delay line of the autocorrelator is based on a circular shift register with XOR gates performing multiplication of the delayed and undelayed single-bit signals at every stage. The multiplication results are accumulated by room-temperature electronics after being prescaled in on-chip binary counters consisting of 10 T flip-flops per stage. We report results of experimental testing of a 16-stage autocorrelator delay line with multiplication and for a linear array of 8 low-power T flipflop binary counters, all fabricated in HYPRES' standard 3.5-mu m 1000-A/cm(2) Nb-trilayer process. We also discuss physical and technical limits of the minimal power dissipation in RSFQ circuits.