Exploiting dimensionality and defect mitigation to create tunable microwave dielectrics

The miniaturization and integration of frequency-agile microwave circuits-relevant to electronically tunable filters, antennas, resonators and phase shifters-with microelectronics offers tantalizing device possibilities, yet requires thin films whose dielectric constant at gigahertz frequencies can be tuned by applying a quasi-static electric field. Appropriate systems such as BaxSr1-xTiO3 have a paraelectric-ferroelectric transition just below ambient temperature, providing high tunability. Unfortunately, such films suffer significant losses arising from defects. Recognizing that progress is stymied by dielectric loss, we start with a system with exceptionally low loss-Srn+1TinO3n+1 phases-in which (SrO)2 crystallographic shear planes provide an alternative to the formation of point defects for accommodating non-stoichiometry. Here we report the experimental realization of a highly tunable ground state arising from the emergence of a local ferroelectric instability in biaxially strained Srn+1TinO3n+1 phases with n = 3 at frequencies up to 125 GHz. In contrast to traditional methods of modifying ferroelectrics-doping or strain-in this unique system an increase in the separation between the (SrO)2 planes, which can be achieved by changing n, bolsters the local ferroelectric instability. This new control parameter, n, can be exploited to achieve a figure of merit at room temperature that rivals all known tunable microwave dielectrics.Peer Reviewe

Electro-thermo-mechanical model for bulk acoustic wave resonators

We present the electro-thermo-mechanical constitutive relations, expanded up to the third order, for a BAW resonator. The relations obtained are implemented into a circuit model, which is validated with extensive linear and nonlinear measurements. The mathematical analysis, along with the modeling, allows us to identify the dominant terms, which are the material temperature derivatives and two intrinsic nonlinear terms, and explain, for the first time, all observable effects in a BAW resonator by use of a unified physical description. Moreover, the terms that are responsible for the second-harmonic generation and the frequency shift with dc voltage are shown to be the same.Peer ReviewedPostprint (published version

Electro-thermo-mechanical model for bulk acoustic wave resonators

We present the electro-thermo-mechanical constitutive relations, expanded up to the third order, for a BAW resonator. The relations obtained are implemented into a circuit model, which is validated with extensive linear and nonlinear measurements. The mathematical analysis, along with the modeling, allows us to identify the dominant terms, which are the material temperature derivatives and two intrinsic nonlinear terms, and explain, for the first time, all observable effects in a BAW resonator by use of a unified physical description. Moreover, the terms that are responsible for the second-harmonic generation and the frequency shift with dc voltage are shown to be the same.Peer Reviewe

Accurate assessment of articular cartilage roughness

SIGLEAvailable from British Library Document Supply Centre- DSC:DXN1403 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Three-port frequency-selective absorptive limiter

©2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This letter describes a novel three-port absorptive limiter for frequency-selective circuits based on a configuration similar to a conventional 90° hybrid coupler. This circuit uses the switching behavior of common diodes to change between the nonlimiting and absorptive limiting states. Theoretical descriptions and designs are presented along with prototypes based on PIN diodes. Measurements of the limiting performance of the devices at approximately 2 GHz as a function of power demonstrate the viability of the concept.Peer ReviewedPostprint (author's final draft

Superconducting Multiplexer Filter Bank for a Frequency-Selective Power Limiter

This work proposes a superconducting multiplexer filter bank configuration to be used as a frequency-selective power limiter. The proposed configuration limits narrowband high-power signals within a single frequency band without degrading the signal performance in the rest of the frequency bands. To accomplish this, we need to calculate the limiting power of superconducting filters implemented by means of half-wavelength transmission line resonators. The limiting power is obtained as a function of the resonator geometry, filter bandwidth, and filter order. Practical issues occurring in superconducting filters operating at high power, such as the reduction of the quality factors and de-tuning, are also analyzed and shown to not adversely affect the overall multiplexer power limiter performance.Peer Reviewe

Three-port frequency-selective absorptive limiter

©2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This letter describes a novel three-port absorptive limiter for frequency-selective circuits based on a configuration similar to a conventional 90° hybrid coupler. This circuit uses the switching behavior of common diodes to change between the nonlimiting and absorptive limiting states. Theoretical descriptions and designs are presented along with prototypes based on PIN diodes. Measurements of the limiting performance of the devices at approximately 2 GHz as a function of power demonstrate the viability of the concept.Peer Reviewe