Robert A. York

Christopher Sanabria2
Stacia Keller2
2Christopher Sanabria
2Stacia Keller
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— 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)
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)
— 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)
—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)
This paper presents an analytic approach to spontaneous emission in resonators with distributed Bragg reflectors (DBR's). The foundation of our analysis is the hard mirror (or penetration depth) approximation, which we extend to radiation with both angular and frequency distributions. This has allowed us to derive approximate analytic expressions for the(More)
— A C-band MMIC oscillator in GaN HEMT technology with Ba x Sr 1-x TiO 3 (BST) film capacitors integrated as DC block capacitors has been designed, fabricated and characterized. The lumped LC resonator works with the common gate HEMT to generate negative resistance. The oscillator, based on AlGaN/GaN HEMT with 0.7um gate length and 200um gate width,(More)
— 5 GHz MMIC GaN oscillators based on AlGaN/GaN HEMTs are presented. By using field-plated HEMT structures, both the output power and dc-to-RF efficiency were improved from the oscillator with non-field-plated GaN HEMT. An oscillator using AlGaN/GaN HEMT with 0.5 mm of gate width and 1.1 µm field-plate extension, delivers 1.9 W output power with dc-to-RF(More)
Arrays of coupled oscillators have recently been considered for millimeter-wave power-combining. Such systems possess a number of interesting and potentially useful nonlinear dynamical phenomena. A new theory describing arrays of coupled millimeter-wave oscillators is presented , and two important applications of such arrays-CW power combining, and a new(More)
Phase shifters are important components in many microwave subsystems used for radar and communication. Current technology makes phase shifters very costly, and inhibits widespread adoption of devices such as phased-array antennas. Barium strontium titante (BST) thin-film varactor technology enables the creation of low cost analog phase shifters. Research is(More)