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Superconductor Analog-to-Digital Converters

Explore the potential of superconductor circuits and Josephson junctions for fast and accurate data conversion between analog and digital domains. Learn about the commercialization of superconductor microelectronics and their applications. Discover how this technology enables 'pure' software radio architectures.

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Superconductor Analog-to-Digital Converters

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  1. Part 3 Superconductor Analog-to-Digital Convertersby : Mahdi Sadjadieh

  2. Ultra fast switching speed low power natural quantization of magnetic flux quantum accuracy superconductor circuits enable fast and accurate data conversion between the analog and digital domains

  3. Commercialization of superconductor microelectronics technology promise to be a key enable of ‘pure’ software radio architectures • This chapter provides a description of the underlying technology and its potential in both commercial and defense wireless systems

  4. Josephson junctions exhibit switching speeds of the order of a few picoseconds or less Superconductor ADCs are based on some of the special properties of superconductivity and Josephson junctions and circuits

  5. 1908- liquefied helium First discovered in mercury by Kamerlingh-Onnes in 1911. Critical temperature 4.21K. Nobel Prize in 1913. Zero Resistivity E=0 inside the superconductor!

  6. Meissner Effect • B=0 inside the superconductor • Superconductor is not just perfect conductor! • Supercurrent flowing around the surface to shield the B field. • Supercurrent is a superfluid.

  7. High Temperature Superconductor

  8. Josephson Junction • Josephson Effect: In superconducting state of certain metals, electrons are attracted by each other and form bound pairs, called Cooper pairs. When these pairs of electrons tunnel through a thin insulating barrier placed between two superconductors, the whole is called Josephson junction.

  9. Josephson Junction Characteristics • Control currents Ic, • Josephson threshold Im. • Gate current Ig, I-V Curve Threshold Curve

  10. - In order to create digital circuits, an active superconductor component is needed : the Josephson junction (JJ) * I < Ic : device exhibits no resistance * I > Ic : JJ becomes briefly resistive

  11. - Design consideration for Josephson junctions in RSFQ circuits is that they be sufficiently damped to prevent hysteresis upon exceeding the critical current, so that the junction quickly return to the Zero voltage - Rapid voltage pulse corresponds to a single flux quantum

  12. Current Magnetic field q Insulator (~1 nm) Damping Parameter bc > 1 bc < 1 IC IC Josephson Tunnel Junction SFQ Technology

  13. A SQUID is a Superconducting Quantum Interference Device Construction SQUID is an inductive loop with one or more Josephson junctions What is a SQUID?

  14. Circuit Characteristics • In RSFQ circuits, it in not a static voltage level, but the presence or absence of quantized • magnetic flux (fluxons) that represents information bits • The basic RSFQ structure is a superconducting ring that contains one Josephson junction • plus a resistive shunt outside it

  15. Emerging Applications – Software Defined Radio - in communications, dispersion-free, ultra-high Q superconductor microwave filters are used in cellular base stations - the use of superconductor material allows the very high Qs to be maintained, while microminiaturizing the overall filter size - the ultra-sharp filter 'skirts' that result enable increased channel selectivity and, with a cooled LNA, yield increased sensitivity as well - an increasingly embraced solution to surmount these obstacles and lies in the concepts of software radio - realization of software radio systems presents a host of challenges - chief among them the unprecedented requirement on analog-to-digital converter (ADC) performance - this is the area where superconductor microelectronics represents an emerging solution - with demonstrated ADC, DAC, and DSP components, this technology may well become a key enabling technology for software radio

  16. (table)  summarizes the performance already achieved with such superconducting • devices to date • - military radio requirements are far more demanding than those for commercial systems

  17. the number of required comparators is , one for each quantization level. In contrast, a superconductor flash ADC, based on SQUID comparators, provides a unique solution for drastic reductionof circuit complexity, and at the same time, allows fastersampling Superconductor Nyquist ADC: Flash ADC

  18. The current is a periodic function Vs the applied input current part of ADC When a clock signal is applied to the sampler, one of these two sampling junctions switches to the resistive state. For a clockwise current ILoop , J2 switches making the output a logical “1,” whereas a counterclockwise current ILoop causes J1 to switch producing a “0” output

  19. Flash ADC

  20. 1) Counting ADC (V/F ADC) 2) Counting ADC (Flux-Quantizing ADC) 3) PMD ADC 4) Delta ADC 5) Low-Pass Sigma–Delta ADC 6) Band-Pass Sigma–Delta ADC Superconductor Oversampling ADCs

  21. the firstJosephson ADCs were based on the voltage-to-frequency(V/F) conversion Acts as a voltage-controlled oscillator (VCO) The signal sampling process is performed by counting the number of generated SFQ pulses over a time interval low-passfirst-order sigma–delta modulation Counting ADC (V/F ADC)

  22. Counting ADC (V/F ADC)

  23. The pulse counting process is done using toggle flip-flops forming a ripple counter, which are the fastest elements in RSFQ technology In order to avoid strong nonlinearities of such a VCO at low input signal, it is necessary to operate the VCO at some input offset. This offset also helps to accommodate positive and negative signals

  24. Counting ADC (Flux-Quantizing ADC)

  25. In order to solve the problem of the quantizer hysteresis, a dc voltage-biased single-junction SQUID quantizer was introduced PMD ADC

  26. Delta ADC

  27. 5) Low-Pass Sigma–Delta ADC

  28. Second order Sigma–Delta ADC

  29. Band-Pass Sigma–Delta ADC

  30. Superconducting DigitizerFor Radio Astronomy Hypres, Inc. Elmsford, NY JPL 93 Phase II INNOVATION Produced a superconducting analog to digital converter for radio astronomy applications • ACCOMPLISHMENTS • Demonstrated a 10 GHz 2-bit digitizer for • radio astronomy •  Technology provides high sensitivity analog • to digital conversion, at very low levels of • power consumption •  High efficiency allows placement behind sensor • array in cryogenic environment • COMMERCIALIZATION •  Received a $1.5 million contract with the • Navy to develop technology for a very sensitive, • high performance radar Picture 40 Meter Radio Telescope at Owens Valley Radio Observatory Near Bishop, CA GOVERNMENT/ SCIENCE APPLICATIONS  Radio astronomy and space deployed telescopes operating in the x-ray and ultraviolet range of the spectrum EuroPKI 2005

  31. Refrences 1)Superconductor Analog-to-Digital converters OLEG A. MUKHANOV, SENIOR MEMBER, IEEE, DEEPNARAYAN GUPTA, SENIOR MEMBER, IEEE, ALAN M. KADIN, AND VASILI K. SEMENOV 2)http://en.wikipedia.org/wiki/Superconductivity 3)Josephson Junction Digital Circuits - Challenges and Opportunities Marc J. FELDMAN

  32. Thanks for your attention

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