Pd. Dresselhaus et al., Modulation and demodulation of 2 GHz pseudo random binary sequence using SFQ digital circuits, IEEE APPL S, 9(2), 1999, pp. 3585-3589
The high speed and low power needed for Spread Spectrum communications lead
s to a desirable application of digital superconductivity. Low temperature
Nb/AlOx/Nb digital Single Flux Quantum (SFQ) circuits have been designed an
d fabricated in our facility, which compose critical subcircuits of the sup
erconductive Spread Spectrum Modem. Four- and 6-bit Pseudo Random Binary Se
quence (PRBS) generators with output latching amplifiers have been produced
and operated at up to 5.4 GHz, On chip modulation and de-modulation of the
se PRBS codes have been performed with time resolution of less than one chi
p of the code. High-speed off-chip data was XORed with the on-chip PRBS at
up to 3.7GHz to produce the modulated pattern, Rapid synchronization allows
the code to start within one clock cycle of being fully reset, and the lat
ching output amplifier gives enough power to do real time room temperature
measurements of high-speed SFQ circuits.