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Limited I/O Josephson Sampler

IP.com Disclosure Number: IPCOM000048267D
Original Publication Date: 1982-Jan-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 3 page(s) / 38K

Publishing Venue

IBM

Related People

Anderson, CJ: AUTHOR [+3]

Abstract

Josephson samplers are useful diagnostic tools affording high resolution due to the very fast switching speed of the Josephson device. Sampling circuits of this type can make high resolution waveform measurements and high resolution time interval measurements between two different high speed signals. Additionally, the comparators used in the sampling circuit can be used to make low frequency measurements. However, the number of I/O (input/output) lines is a serious constraint in the design of these Josephson sampling circuits. Three techniques are described for reducing the amount of I/O that is required.

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Limited I/O Josephson Sampler

Josephson samplers are useful diagnostic tools affording high resolution due to the very fast switching speed of the Josephson device. Sampling circuits of this type can make high resolution waveform measurements and high resolution time interval measurements between two different high speed signals. Additionally, the comparators used in the sampling circuit can be used to make low frequency measurements. However, the number of I/O (input/output) lines is a serious constraint in the design of these Josephson sampling circuits. Three techniques are described for reducing the amount of I/O that is required.

To decrease the amount of I/O, the pulse generator and DC bias can be incorporated on the same I/O line by using a high-pass/low-pass filter arrangement. Additionally, a number of comparators can be arranged in series on one I/O line, with each comparator having a different I(mo) to allow one to distinguish between them. Further, the comparators can be distributed around the logic and other chips, for example, by being buried in the wiring channels.

The proposed sampling scheme is shown in Fig. 1. The pulse generator requires one I/O line, the DC bias/feedback requires one I/O line 12, and the multiple comparators require only one I/O line 14. The pulse generator is triggered by a sharp pulse. The pulse generator consists of two Josephson functions with critical currents I1 and I2, where I1 is larger than I2. The pulse/DC bias lines can go to the comparators C1, C2, C3 and C4 in parallel or in series. The comparators are connected in series. Each comparator can monitor several signal lines. The room temperature electronics can distinguish between the different comparators because each comparator has a different I(mo). An in-line gate can be used for the comparator instead of a two-junction interferometer. By changing the polarity of the control current with respect to the in-line gate, two in- line gates can have the same I(mo), and the in-line gate that is used in the sampler is determined by the polarity of the DC bias and the pulse generator pulse.

In Fig. 2, representative comparator 1 is accessed by using a positive DC bias and pulse, while representative comparator 2 is accessed by using a negative DC bias and pulse. A possible pulse generator and...