AC and DC bipolar voltage source using quantized pulses

Details AC and DC bipolar voltage source using quantized pulses AC and DC bipolar voltage source using quantized pulses

1999-07-02

2001-05-22

JeanPierre, Peguy (Department: 2819)

Coded data generation or conversion

Analog to or from digital conversion

With particular solid state devices

C341S143000

Reexamination Certificate

active

06236344

ABSTRACT:

This invention relates to a circuit for waveform generation wherein arrays of Josephson junctions are biased by combining a broadband two-level digital code and a sinusoidal frequency to produce a highly accurate bipolar voltage source.
BACKGROUND OF THE INVENTION
A wide variety of instrumentations exist to measure voltage. All of these instrumentations must be calibrated to provide accurate measurements. In the field of ac and dc metrology, instruments are devised to provide exact measurements of voltage so that other instruments can be calibrated to them. The Josephson junction has been utilized in metrology to take advantage of its quantum mechanical characteristics wherein time integrated areas of every generated voltage pulse are exactly the same regardless of the shape of the pulse as long as the device is driven at or above the critical current. When biased with a sinusoidal microwave frequency f, each junction exhibits constant voltage steps at V=nf/K
J
. The Josephson frequency to voltage ratio K
J
is a defined constant equal to 2 e/h which is the ratio of twice the electron charge and Planck's constant. K
J
is equal to 483,597.9 GHz/V. When biased on each nth step, a junction generates exactly n quantized voltage pulses for each microwave period. For an array of N junctions, the time average dc voltage of the n
th
step is Vn=nNf/K
J
where N is the number of Josephson junctions.
Synthesized voltage sources utilizing Josephson technology have been proposed and developed for unipolar ac and dc voltages that control pulses of a single polarity. The object of this invention is to devise a Josephson circuit for accurate, stable, arbitrary waveform generation with a predetermined frequency spectrum which will enable synthesis of both ac and dc bipolar waveforms where voltage pulses of both positive and negative polarity are precisely controlled and used to increase the output voltage.
SUMMARY OF THE INVENTION
Briefly stated, this invention is a circuit which provides a Josephson junction or series array of junctions driven with the combination of a sinusoidal microwave frequency and digital pulses. The digital pulses correspond to the mathematical model of a desired waveform. That waveform may be an ac waveform or any dc waveform that can be generated using a digital code of appropriate pattern and length. The combination of the sinusoidal drive and the digital pulses is used to current bias a Josephson quantizer. Output of the quantizer is fed into a standard filter to remove unwanted noise and thereby produce the desired waveform. Knowledge of the digital code, the drive frequency and the number of Josephson junctions is sufficient to precisely calculate the waveform output and in that manner enable highly accurate physical reproductions of the mathematical model.


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