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Linear Josephson Sampler

IP.com Disclosure Number: IPCOM000047962D
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Anderson, JC: AUTHOR

Abstract

Sampling by means of a pulse generator and an in-line gate comparator makes possible the measuring of waveforms of high speed, low temperature Josephson devices without the need for a feedback circuit. Fig. 1 shows the sampler circuit, made up of a pulse generator 1 and an in-line gate comparator 2, which has a linear threshold region. (An asymmetric two-junction interferometer can also be used since it has a linear region in the threshold curve like the in-line gate.) An in-line gate threshold curve is shown in Fig. 2 with the pulse and waveform to be measured. The pulses from the pulse generator 1 are narrow (N20 ps) with a frequency of about 10 MHz. The gate current Ig is ramped at the rate of about 1-10 KHz so that the gate current ramp is sampled between 1,000-10,000 times by the pulse.

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Linear Josephson Sampler

Sampling by means of a pulse generator and an in-line gate comparator makes possible the measuring of waveforms of high speed, low temperature Josephson devices without the need for a feedback circuit. Fig. 1 shows the sampler circuit, made up of a pulse generator 1 and an in-line gate comparator 2, which has a linear threshold region. (An asymmetric two-junction interferometer can also be used since it has a linear region in the threshold curve like the in-line gate.) An in-line gate threshold curve is shown in Fig. 2 with the pulse and waveform to be measured. The pulses from the pulse generator 1 are narrow (N20 ps) with a frequency of about 10 MHz. The gate current Ig is ramped at the rate of about 1- 10 KHz so that the gate current ramp is sampled between 1,000-10,000 times by the pulse. When the comparator switches, the gate current and time delay of its pulse are measured and stored. Since the threshold curve is linear, the gate current that switches the comparator is linearly related to the current waveform being measured. The pulse generator is swept in time at about 1-10 Hz so that there are about 1000 points in both the time axis and in the signal amplitude axis. When the gate current Ig(s) at which the comparator switches is plotted as a function of the pulse delay time, the inverse of the current waveform is produced. The waveform can be averaged 10 times in a few seconds time. The linear sampler may be automated much like th...