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A latest demonstration of superconductor oscillator/counter A/D Converter up through twelve Giga-Sample per second (12 GS/s) with 3 effective bits of signal-to-noise ratio at that sample rate is presented along with analysis of its performance. This A/D Converter incorporates a new technique for defining the aperture using inter-Josephson transmission line single-flux-quantum repulsion.

Performance results of a static divide-by-two circuit, an NbN Single Flux Quantum (SFQ) T-flip-flop (TFF), are reported.

It is argued that series biasing is a viable solution to the problem of powering large rapid single flux quantum (RSFQ) chips and systems. Two approaches to resolving the obstacle of differential SFQ signal transfer are proposed.

A study of oscillator/counter analog-to-digital converters is presented with emphasis on their theoretical aspects and performance. The advantages such as low power of a basic model and its variations are examined.

Single flux quantum gates were used for designing a crossbar switch. The performance of the 4x4 prototype switch and that of an individual crosspoint element were identified. A new double-edge-triggered direct-current single flux quantum converter design was also proposed and its output amplification requirements determined. The switch well was successfully tested up to 3 Gbps.

A digital superconducting frequency synthesizer was designed, fabricated and and tested. The chip, which features a 12-bit pipelines MVTL incremental phase accumulator, is based on superconducting Nb Josephson technology. Connectivity and process control monitor testing reveal the potential of new superconducting direct digital synthesizers. The performance goals and achievement of current tests are presented.

The layout and design of a modified variable threshold logic gate using NbN that has optimum margin and fanout for 10 K operation is studied. The method is based on an experimental design that efficiently searches for a multi-dimensional parameter space for the optimum gate design and performs a sensitivity analysis of each parameter. Results can be applied to other logic families.

The gate performance of Modified Variable Threshold Logic (MVTL) circuits is studied at multi-GHz frequencies. Bit error rate measurements are performed using a single-chip 4-bit direct digital synthesizer system as the test sample. The measured data suggest that there are several parameters that should be optimized to improve the gate performance of MVTL devices. These include the circuits' gain behavior, power dissipation and time delay characteristics.

Error rate measurements of a binary ripple counter made of Josephson single flux quantum circuits are reported in a quantitative performance analysis of their memory and logic operations. Observations showed the bit error rate to be around 0.22 for every million binary operations. It remains unaffected by the bit pattern and bit rate up to 100 MHz but relies heavily on the counter cell operating point, according to the study.

A superconducting digital to analog (D/A) converter based on the Josephson effect was developed. Magnetic coupling of the digital input lines was added to simplify the input interface. Conversion to a balanced two superconducting quantum interference device (SQUID) unit cell was also effected to allow for input-to-output voltages. Results demonstrate the first balanced Josephson D/A circuit based on magnetic control and magnetic excitation of SQUID's.

The high-performance operation of a simple series array interferometer logic gate, a modified exclusive OR (EXOR), as an ideal phase shift keying modulator of a 1 GHz carrier is demonstrated. The gate had a phase shift accuracy of better than 2 degrees and an amplitude imbalance of less than 0.25 decibels. The EXOR's excellent performance makes it an ideal interface for room temperature electronics.

The distributed Josephson inductance (DJI) transmission line phase shifter features high fault tolerance, low control power and wide band signal processing. The DJI is an eight-centimeter long superconducting microstrip magnetically coupled to 1600 superconducting quantum interference devices (SQUID) and is fabricated using niobium integrated circuit technology. Tests show that a radio frequency (RF) signal undergoes a 60 degree phase shift at 10 gigaHertz (GHz) while broad band operation is achieved at 5-15 GHz. Wave velocity, and hence, phase shift are controlled either by magnetic induction or a direct current supply to the microstrip.

Presents information on a study in which a digital superconducting frequency synthesizer was designed, fabricated and tested, on a 1-cm square substrate in niobium technology. What can be provided by digital synthesis; Most significant 10-bits of the accumulated phase.