Experimental Verification of Superconductor Digital Circuits
Doktorsavhandling, 2007

Abstract Superconducting digital technology based on Rapid Single Flux Quantum (RSFQ) logic offers a 50 times faster clock rate and 100 times less on chip power consumption than today's mainstream semiconductor electronics. This technology is attractive for many applications and in particular for Digital Signal Processing (DSP). The applications of the RSFQ DSPs are numerous and include multi-user detection in spread spectrum system, channel equalization for Multi-in, Multi-out (MIMO) systems, and blind detection and signal tracking for signal intelligence. At Chalmers we are developing a hybrid DSP with target performance of 30 giga operations per second. It consists of an RSFQ Multiply Accumulate unit (MAC), RSFQ fast cache memory, and an external semiconductor memory. The development of the complex high speed cryogenic digital system requires interface, packaging and testing solutions. The main difficulties are due to the 4 K operational temperature, the high magnetic field sensitivity of the RSFQ circuits, the multi-channel high bandwidth interface required in the hybrid architecture, and the high speed RSFQ digital core. The key steps towards addressing each of these problems are the subject of this thesis. The main emphasis is put on the experimental testing and interfacing of superconductor electronics. A large part of the work is connected to the experimental verification of DSP components and their incremental improvement towards functionality. The RSFQ circuits tested were fabricated using the four-metal layer VLSI processes available from NGST (8 kA/cm^2 Josephson junction critical current) and HYPRES (both 1 kA/cm^2 and HYPRES 4.5 kA/cm^2. The main results of the work are demonstrations of the RSFQ cache memory with more than 2,000 Josephson junctions, 33.5 GHz operation of the digital clock controller, and 20.48 GHz operation of the autocorrelator. In addition, various experiments have been done for investigation of parasitic effects in RSFQ circuits such as flux trapping and influence of the high current bias lines. At the final stage of the work, a unique high bandwidth 4 K cryocooler based experimental setup has been developed. The system, developed in close cooperation with Hypres Inc. USA, has 40 high speed I/Os with bandwidth of 2 Gbps, 64 DC bias channels, 4 high frequency clock lines, and 4 auxiliary control lines. It supports exchangeable test units for 10 mm x 10 mm and 20 mm x 20 mm Multi Chip Module (MCM) carriers. The availability of such a system is critical to demonstration of the hybrid DSP prototype and future commercialization.



Multi Chip Modules (MCM)

high frequency test

Rapid Single Flux Quantum (RSFQ) logic


Kollektorn, MC2, Chalmers University of Technology
Opponent: Dr. Donald Miller, Northrop Grumman Corporation, USA


Henrik Engseth

Chalmers, Mikroteknologi och nanovetenskap (MC2), Kvantkomponentfysik

RSFQ Digital Signal Processor for Interference Cancellation

Applied superconductivity conference,; (2004)

Paper i proceeding

High frequency test bench for Rapid Single Flux Quantum circuits

Superconducting Science and technology,; Vol. 19(2006)p. S376-S380

Artikel i vetenskaplig tidskrift

Scalable Matrix Multiplication with Hybrid CMOS-RSFQ Digital Signal Processor

oral presentation Applied Superconductivity Conference (ASC) Sept 2006, Seattle, will be published in IEEE Transactions on Applied Superconductivity June 2007,; Vol. June(2007)

Paper i proceeding

Influence of the Bias Supply Lines on the Performace of RSFQ Circuits

IEEE Transactions on Applied Superconductivity,; Vol. 15(2005)p. 276-279

Artikel i vetenskaplig tidskrift

Time-Delay Optimization of RSFQ Cells

IEEE Transactions on Applied Superconductivity,; Vol. 15(2005)p. 328-331

Artikel i vetenskaplig tidskrift

New Design of a RSFQ Parallel Multiply-Accumulate Unit

Superconducting Science and technology,; Vol. 19(2006)p. S381-S386

Artikel i vetenskaplig tidskrift

Optimization of Superconducting Microstrip Interconnects for Rapid Single-Flux-Quantum Circuits

Superconductor Science and Technology,; Vol. 18(2005)p. 1065-1072

Artikel i vetenskaplig tidskrift


Elektroteknik och elektronik



Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 2703

Technical report MC2 - Department of Microtechnology and Nanoscience, Chalmers University of Technology: 106

Kollektorn, MC2, Chalmers University of Technology

Opponent: Dr. Donald Miller, Northrop Grumman Corporation, USA