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Research was conducted to design and simulate two-loop Delta-Epsilon modulators capable of greater than 100 dB of signal-to-noise ratio for a 10 MHz input bandwidth. Each modulator was capable of operating at 10 GHz. Current state-of-the-art analog-to-digital converters have approximately 85 dB of dynamic range at 10 MHz input bandwidth. The modulators offer the opportunity for increased resolution.

The application of thin-film transformers to microwave circuits is described. A low-frequency lumped-element analysis of the devices including calculations of their bandwidth was conducted. An alternative model for the transformer where each part of the patterned circuit is treated as a distributed element is presented. Numerical simulations based on the distributed model were in excellent agreement with data taken on actual devices.

Circuits for receiving and transmitting bits generated by Single Flux Quantum circuits have been developed using shunted Nb-AlOx-Nb junctions. A series array of dc SQUIDs driven into the voltage state was used as a transmitter and inductively coupled with the receiver circuit. The transmitter generated a maximum peak-to-peak amplitude of 296 micro V at a clock rate of 2.5 GHz and 187 micro V at 5 GHz.

Three types of high-transition-temperature magnetometers are developed with the use of a YBa2Cu3O7-x-SrTiO3-YBa2Cu3O7-x multilayer process. These are multiturn flux transformers combined with single layer direct current superconducting quantum interference devices (SQUIDs) in flip-chip arrangements, multiturn flux transformers integrated with dc SQUIDs and multiloop magnetometers.

The feasibility of using a high-critical temperature superconducting quantum interference device (SQUID) in obtaining high frequency magnetic microscopic images is evaluated through experimental procedures. A SQUID-based microscope is designed and employed in imaging subsurface defects in metal structures at frequencies ranging from zero to 200 GHz. Results show that the SQUID-based microscope is a very useful tool for nondestructive testing of metals.

The operating characteristics of yttrium barium copper oxide superconducting quantum interference devices (SQUIDs) fabricated on a single SrTiO3 bicrystal substrate were studied. The SQUIDs' current-voltage properties were measured in a liquid nitrogen environment under the presence of an ambient magnetic field. An electronic modulation scheme was then employed to reduce the SQUIDs' white noise emission to a useful level. Results reveal that the use of the current reversal scheme decreased the white noise level by at least two orders of magnitude.

We have designed and measured single flux quantum (SFQ) circuits for data switching at 2.5 Gbps. A fully functional 2/spl times/2 switching node is presented. The node can be used to form a larger switching fabric (4/spl times/4, 8/spl times/8, etc.). The node accepts data streams at either or both inputs, routing the data based on address bits present in the data stream. This approach allows the data to be self-routing and the switch to be self-synchronous. In addition, the switch can route data correctly on an active input line if the other is idle. [ABSTRACT FROM PUBLISHER]

Examines YBa[sub 2]Cu[sub 3]O[sub 7-x] thin film magnetometer. Use of photolithographic processing to pattern layers; Operation of the magnetometer; Determination of the flux transformer critical current; Measurement of the device magnetic field sensitivity.

Evaluates picovoltmeters based on a high transition temperature direct current superconducting quantum interference device (SQUID). Connection of the voltage source to a calibrated resistor and a coil coupled to a SQUID; Components of the coil; Determination of the lowest voltage noise achieved.

Investigates the noise performance of YBa[sub 2]Cu[sub 3]O[sub 7-x] direct current superconducting quantum interference devices (SQUID). Absence of effect in the white noise of the devices at 77 Kelvin; Increase in the magnitude of the spectral density of the 1/f noise; Impact of the increase in noise on SQUID operated in the field of the earth.

Details the fabrication of direct current (dc) superconducting quantum interference device (SQUID) magnetometers with single film YBa[sub 2]Cu[sub 3]O[sub 7-x] flux transformers. Attachment of the transformer to a loop directly coupled to a dc SQUID; Values of the lowest magnetic field noise achieved; Applications of the device.

Fabricates the direct current superconducting quantum interference device (SQUID) magnetometers from YBa[sub 2]Cu[sub 3]O[sub 7-x] thin films. Use of flux modulation to measure the magnetometer noise; Relationship between magnetic field sensitivity and hole size; Effect of reducing SQUID inductance on magnetic field resolution.

Examines the production of magnetic images of eddy currents in patterned copper thin films using a scanning magnetic flux microscope. Use of weak applied fields in small structure imaging; Application of the superconducting quantum interference device in the image production; Induction of eddy currents in the samples.

Describes the fabrication and testing of an integrated thin-film magnetometer with two superconducting layers. Use of superconducting quantum interference device as flux transformer crossunder; Sequence of deposition and photolithographic patterning of the layers; Measurement of magnetic flux and field noise; Use of x-ray diffraction technique.

Evaluates magnetic microscopy through liquid nitrogen cooled YBa[sub 2]Cu[sub 3]O[sub 7] superconducting quantum interference device. Production of two-dimensional images of magnetic fields; Development of magnetic flux microscope; Presentation of magnetic images.