On-chip clock technology for ultrafast digital superconducting electronics

An on-chip, low-jitter clock technology is essential for future multi-GHz digital electronics. In this article, we describe an on-chip clock technology for superconducting rapid single flux quantum (RSFQ) circuits built around an unshunted long Josephson junction (LJJ) oscillator that acts as a master clock source. The clock technology also includes clock frequency divider and selector circuits as well as a clock distribution network. These LJJ oscillators, implemented in linear and annular geometries using 3 mu m Nb technology, have quality factors of 10(6). This clock technology potentially has widespread use in 10-100 GHz superconducting digital circuits and systems, including analog-to-digital converters, time-to-digital converters, correlators, and processors for ultrahigh performance computers. (C) 2000 American Institute of Physics. [S0003-6951(00)04325-4].