Title :
Linewidth measurements and phase locking of Josephson oscillators using RSFQ circuits
Author :
Dubash, N.B. ; Yongming Zhang ; Ghoshal, U. ; Perng-Fei Yuh
Author_Institution :
Conductus Inc., Sunnyvale, CA, USA
Abstract :
We present a technique for linewidth measurement and phase-locking of Josephson oscillators using digital rapid single-flux-quantum (RSFQ) circuits. The oscillator consists of a resistively shunted 6 /spl mu/m/spl times/6 /spl mu/m Nb/AlO/sub x//Nb Josephson tunnel junction that is integrated with RSFQ input and output circuits. A cascade of RSFQ T flip-flops is used to directly monitor the output of the Josephson oscillator. Spectral characteristics have been measured directly for oscillator frequencies ranging from 10-50 GHz. The linewidth can be reduced by over 100 times by phase-locking the oscillator to an RSFQ pulse train generated by an external sinusoidal signal. These Josephson oscillators can be used as on-chip stable high frequency clocks for RSFQ circuits.
Keywords :
clocks; flip-flops; integrated circuit measurement; microwave measurement; microwave oscillators; millimetre wave measurement; millimetre wave oscillators; phase locked oscillators; superconducting device testing; superconducting integrated circuits; superconducting logic circuits; superconducting microwave devices; 10 to 50 GHz; Josephson oscillators; Nb-AlO-Nb; RSFQ T flip-flops; RSFQ circuits; RSFQ pulse train; digital rapid single-flux-quantum circuits; linewidth measurement; on-chip stable high frequency clocks; oscillator frequencies; phase locking; resistively shunted Nb/AlO/sub x//Nb Josephson tunnel junction; spectral characteristics; Clocks; Flip-flops; Frequency measurement; Integrated circuit measurements; Monitoring; Niobium; Oscillators; Phase measurement; Pulse generation; Signal generators;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
