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Narrowband microstrip filters are fabricated from YBa2Cu3O7-delta high-temperature superconducting films via the laser ablation technique. The filters are of the low-pass design and exhibit low insertion loss and high power-handling capabilities. They have a fractional bandwidth of 1.2% at 2.0 GHz and are capable of operating at temperatures up to 45 degrees Kelvin without any degradation in performance.

A forward-coupled microstrip filter is developed cellular communication applications at frequency bands of 9000 MHz and 2.0 GHz. The filter consists of a parallel array of fully aligned half-wave resonators that provides the even- and odd-mode phase velocity difference required to achieve optimal coupling. It is fabricated by depositing superconducting YBa2Cu3O7 thin films onto LaAlO3 substrates.

The impact of etching on the surface resistance and surface morphology of sputtered and laser ablated thin films of YBa2Cu3O(7-delta) were investigated. Specifically, reflection high energy electron diffraction and atomic force microscopy methods were used together with microwave measurements to characterize the films prior to and after etching with citric acid, nitric acid, Br-methanol, EDTA, disodium EDTA and ion milling. The experiments revealed that ion milling resulted in the most severe degradation of surface crystallinity and highest rise in surface resistance.

A standardized neighbor removal experiment was conducted in 12 plant communities located on three continents to test the null hypothesis that competition intensity (CI) was independent of the amount of plant biomass present. Six plots were chosen in each community to cover the range of local variation in plant biomass. In each plot the relative growth rate (RGR) of transplanted Poa pratensis (Poaceae) seedlings was compared in the presence and absence of neighbors. Neighbors were removed experimentally using herbicide. Removing neighbors increased RGR of transplants significantly in most plots. CI increased with an increase in the amount of neighbor biomass present in one community where the range of neighbor biomass was greater than in any other community. In contrast, CI did not change significantly with an increase in neighbor biomass in other communities where the range of neighbor biomass was smaller. For the communities combined, CI was not related to neighbor biomass in a consistent fashion. These results indicate that competition may reduce growth over a wide range of habitat productivity, but the relationship between CI and neighbor biomass may differ among communities.

The optical properties and thermal conductivity of YBCO thin film bolometers fabricated on silicon substrates were studied. YBCO films were deposited on silicon substrates and the resulting structures were subsequently subjected to weak pulse irradiation. The devices' infrared transmission was then measured at low temperatures. Results indicate that silicon outperforms other available materials as substrate for epitaxial-YBCO film bolometers.

We have constructed a five-bit high temperature superconductive digital instantaneous frequency measurement (DIFM) subsystem capable of determining the frequency of unknown signals over a 500-MHz bandwidth, centered on 4 GHz, with a resolution of 17.8 MHz. The system consists of three parts: a limiting amplifier and filter, a comparator and data processing unit operating at room temperature, and a cryogenic subsystem containing five discriminator modules based on superconductive delay lines, GaAs mixers and power dividers. With a single-tone CW input between -40 dBm and +10 dBm, the frequency quantization boundaries of the subsystem are, on average, 3.1 MHz from their design values. This system was built for the High-Temperature Superconductor Space Experiment, Phase II (HTSSE II). It has passed all required qualification tests for vibration, shock and thermal cycling. The system is currently scheduled for satellite launch in fall 1996. Compared to a conventional system, the superconductive version of the DIFM is considerably smaller and provides enhanced resolution. In addition, the technology employed can be readily extended to a system with additional bits and wider instantaneous bandwidth. The system built demonstrates the potential for system-level applications of high-temperature superconductive electronics in instrumentation, communications, radar, and electronic warfare. [ABSTRACT FROM AUTHOR]

Investigates the delay of electrical picosecond pulses in YBa[sub2]Cu[sub 3]O[sub 7] (YBCO) spiral delay line. Fabrication of kinetic inductance delay lines from high-temperature superconducting thin films; Effects of applied current on the kinetic inductance of YBCO delay line.

Presents a technique for fabricating high transition temperature superconductor-normal metal-superconductor microbridges. Use of a step edge to define the normal metal length; Measurement of the critical current-normal resistance; Demonstration of Josephson effects.

Focuses on the issue of magnetic field dependence anisotropy of the critical current density in a unique composite structure of pattern YBCO thin films with normal-metal overlayers. Preparation of films in situ by pulsed laser ablation; Definition of directions of current flow, field and crystalline axes.