Robert A. York

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This paper describes the design and fabrication of a distributed MEMS () transmission line DMTL , used to realize a transmission-line with a voltage-variable electrical length for microwave circuits. The DMTL is a coplanar waveguide periodically loaded with continuously-variable MEMS capacitors. A tunable bandpass filter was designed and fabricated on 700(More)
1993 iii Acknowledgments I would like to acknowledge the contributions of all those who made this work possible. I am especially grateful to Mark Rodwell for his never ending help and guidance throughout the last four years. He is remarkable for his broad outlook and quick thinking in just about all matters. Mark has been an instructor, manager, and friend.(More)
— This paper presents an electronically tunable impedance transformer and matching network for RF applications, utilizing thin-film Barium Strontium Titanate (BST) tunable capacitors in an integrated-passive network on sapphire. The impedance transformer can be electronically varied from a 4:1 to 2:1 transformation in a 50 Ohm environment. A slight(More)
—We derive a simple formula for the change in output when a device fails in a power-combining structure with identical matched devices. The loss is written in terms of the scattering coefficient of the failed device and reflection coefficient of an input port in the combining network. We apply this formula to several power combiners, including arrays in(More)
Forest structure, fuel characteristics, and fire regimes of mixed conifer forests in the Western United States (US) have been dramatically altered since the early 20th century. Fuel treatments have been suggested as a means to limit the size and intensity of wildfires but few experiments are available to analyze the ecological effects of different(More)
— Barium strontium titanate is a solid solution perovskite with a field-dependent permittivity. At microwave frequencies, its tunable dielectric constant and low loss make it a competitive choice for varactors and other tunable circuit elements. Much attention has been focused on the production of low-loss films for such applications, with little emphasis(More)
— High power, broad bandwidth, high linearity and low noise are among the most important features in amplifier design. Broadband spatial power combining technique addresses all these issues by combining the output power of a large quantity of microwave monolithic integrated circuit (MMIC) amplifiers in a broadband coaxial waveguide environment, while(More)
Experimental canopy gaps ranging in size from 0.1 to 1.0 ha (0.25 to 2.5 acres) were created in a mature mixed conifer forest at Blodgett Forest Research Station, California. Following gap creation, six species were planted in a wagon-wheel design and assessed for survival after two growing seasons. Study trees were measured after seven years to describe(More)