CRC Press eBooks

Superconducting Analog-to-Digital Converters

Alan M. Kadin, Oleg A. Mukhanov

Published May 17, 2022• 0 citations

Abstract

Analog-to-digital converters (ADCs) are electronic circuits that convert an electrical signal from the analog domain to the digital domain of binary numbers, which can then be processed by computers. A digital-to-analog converter (DAC) functions in the reverse direction, converting a sequence of binary numbers into a continuous electrical signal, and high-performance superconducting DACs are still being developed. A time-to-digital converter (TDC) digitizes time and resembles in some ways ADCs. Superconducting TDCs are simpler than ADCs and are being developed mostly for integration with cryogenic sensor arrays. Quantization refers to the selection of a discrete value for the magnitude when the signal is sampled, and is carried out by a quantizer. A high sampling rate with good linearity is necessary for high fidelity to the desired signal, and a DAC can be characterized by parameters of SNR and SFDR in much the same way as an ADC.

DOI: 10.1201/9781003139638-53

Related papers

Superconductor analog-to-digital converters and their applications

Deepnarayan Gupta, Amol Inamdar, Dmitri E. Kirichenko +2 more

A wide variety of applications, ranging from radio-frequency (RF) receivers for broadband communications and signal detection, on earth and in space, would benefit from high-performance superconductor analog-to-digital converters (ADCs), based on magnetic flux quantization and fast switching Josephson junctions. Superconductor ADCs are capable of very high sample rates (100 GHz or more), very high linearity, and high sensitivity. Nyquist-rate ADCs use the high sample rate to digitize a wide instantaneous bandwidth (tens of GHz) and are useful for wideband spectrum monitoring as well as high-end scientific instrumentation. Delta and delta-sigma oversampling ADCs use the high linearity to achieve programmable trade-off between dynamic range and instantaneous bandwidth. These lowpass and bandpass ADCs have been used for direct digitization of narrower (tens to hundreds of MHz) RF bands in the 1-20 GHz range for a variety of communications, intelligence, electronic warfare, and radar applications. Another application area of these cryogenic ADCs is for outputs of cryogenic sensor arrays and terahertz mixers. Recent advances in various classes of ADCs for different applications are described.

IEEE MTT-S International Microwave Symposium digestJun 1, 201121 citations

Superconductor analog-to-digital converters

Oleg A. Mukhanov, Deepnarayan Gupta, Alan M. Kadin +1 more

Ultrafast switching speed, low power, natural quantization of magnetic flux, quantum accuracy, and low noise of cryogenic superconductor circuits enable fast and accurate data conversion between the analog and digital domains. Based on rapid single-flux quantum (RSFQ) logic, these integrated circuits are capable of achieving performance levels unattainable by any other technology. Two major classes of superconductor analog-to-digital converters (ADCs) are being developed - Nyquist sampling and oversampling converters. Complete systems with digital sampling at rates of /spl sim/20 GHz and above have been demonstrated using low-temperature superconductor device technology. Some ADC components have also been implemented using high-temperature superconductors. Superconductor ADCs have unique applications in true digital-RF communications, broadband instrumentation, and digital sensor readout. Their designs, test results, and future development trends are reviewed.

Proceedings of the IEEESep 20, 2004185 citations

Superconducting delta ADC with on-chip decimation filter

Vasili K. Semenov, Y.A. Polyakov, Timur V. Filippov

Last year we presented the first fully operational superconducting Analog-to-Digital Converter (ADC) with on-chip Digital Signal Processing (DSP). Here we review this device and introduce completed and prospective innovations required to exceed the performance of the best semiconductor counterparts. The ADC chip contains 2 basic parts: a "fundamental" ADC operating at about 20 GHz sampling rate and a digital decimation filter which attenuates high-frequency noise components and reduces the sampling rate to match it with the bandwidth of an input signal. Our short term goal is to achieve 14 bits Spurious Free Dynamic Range (SFDR) for 60 MHz signal bandwidth by using the standard 1000 A/cm/sup 2/ Nb-trilayer fabrication technology commercially available at HYPRES, Inc.

IEEE Transactions on Applied SuperconductivityJun 1, 199926 citations

High-Resolution Analog-to-Digital Converters toward Software-Defined-Radio Receivers

Akira Fujimaki

We describe three types of software-defined-radio (SDR) receivers based on superconducting technologies. The superconducting analog bandpass filters are essential for all types of the receivers. Another key component is an analog-to-digital converters (ADCs), which are required to have high resolution with a broad band width. The complementary A ADC based on the single-flux-quantum circuit is a promising candidate for the SDR receivers because it has a practical nature together with above-mentioned requirements. The experimentally obtained signal-to-noise ratio (SNR) and sensitivity, which are closely related to the resolution, are 34 dB and 20 μA for a quarter of the full-scale input with a band width of about 20 MHz. If we use the optimum decimation filter, the ADC is expected to have the SNR of 82 dB and the sensitivity of 300 nA. These values meet the requirements of the easiest type of the SDR receiver. After new fabrication process has been introduced and the architecture of the ADC has been improved, all types of recievers could be realized based on suoerconductors.

IEICE Transactions on ElectronicsFeb 1, 20064 citations

An SFQ digital to analog converter

Robert D. Sandell, Bruce J. Dalrymple, A.D. Smith

We have developed and demonstrated a digital to analog converter DAC which uses an SFQ counter to precisely divide an input reference oscillator to produce a set of binary frequencies/voltages. The binary input gates the output SFQ pulses of the counter flip flops to a passive summing network, producing an analog output current. The DAC is asynchronous (no clock to reset latching circuits), low power, and requires only N equal matched resistors. We have built and tested a 4-bit Nb DAC with data clocking rates up to 1 GHz. Using the DAC we have generated arbitrary wave forms including ramps and sine waves. By measuring the harmonic content of sine wave outputs, we deduce values for the DAC linearity.

IEEE Transactions on Applied SuperconductivityJun 1, 19973 citations

SUPERCONDUCTING DIGITAL MULTIPLEXERS FOR SENSOR ARRAYS

Alan M. Kadin, DARREN K. BROCK, Deepnarayan Gupta

Arrays of cryogenic microbolometers and other cryogenic detectors are being developed for infrared imaging. If the signal from each sensor is amplified, multiplexed, and digitized using superconducting electronics, then this data can be efficiently read out to ambient temperature with a minimum of noise and thermal load. HYPRES is developing an integrated system based on SQUID amplifiers, a high-resolution analog-to-digital converter (ADC) based on RSFQ (rapid single flux quantum) logic, and a clocked RSFQ multiplexer. The ADC and SQUIDs have already been demonstrated for other projects, so this paper will focus on new results of a digital multiplexer. Several test circuits have been fabricated using Nb Josephson technology and are about to be tested at T = 4.2 K, with a more complete prototype in preparation.

Oct 2, 20161 citation