Amanda Baker

Design optimization and implementation of bandpass filters with normally fed microstrip resonators loaded by high-permittivity dielectric

Different approaches for designing bandpass filters with transmission zeroes are investigated by using the transmission-line theory and the finite-difference time-domain method. The filters are composed of capacitively coupled uniform impedance microstrip resonators, stepped-impedance microstrip resonators, and tapped feed lines. Different design modifications are discussed and, as a result, a design with double-coupled resonators is proposed. Based on this structure, a miniaturized filter capacitively loaded by high-permittivity dielectric inclusions and fabricated by using low-temperature co-fired ceramic (LTCC) technology is presented. The measured and simulated S-parameter spectra of the LTCC-filter are in good agreement.

Hydrothermal-Assisted Cold Sintering Process: A New Guidance for Low-Temperature Ceramic Sintering

Sintering is a thermal treatment process that is generally applied to achieve dense bulk solids from particulate materials below the melting temperature. Conventional sintering of polycrystalline ceramics is prevalently performed at quite high temperatures, normally up to 1000 to 1200 °C for most ceramic materials, typically 50% to 75% of the melting temperatures. Here we present a new sintering route to achieve dense ceramics at extraordinarily low temperatures. This method is basically modified from the cold sintering process (CSP) we developed very recently by specifically incorporating the hydrothermal precursor solutions into the particles. BaTiO3 nano polycrystalline ceramics are exemplified for demonstration due to their technological importance and normally high processing temperature under conventional sintering routes. The presented technique could also be extended to a much broader range of material systems than previously demonstrated via a hydrothermal synthesis using water or volatile solutions. Such a methodology is of significant importance, because it provides a chemical roadmap for cost-effective inorganic processing that can enable broad practical applications.

New approaches for designing microstrip filters utilizing mixed dielectrics

A strategy is developed for designing capacitively loaded microstrip filters on low-temperature co-fired ceramic (LTCC) substrates with inclusions or superstrate layers of higher permittivity dielectrics. Finite-difference time-domain simulations of the field distribution at resonant frequencies are used to determine the optimal locations and size of capacitive loads. It is demonstrated that strategic capacitive load placement enables altering the center and attenuation pole frequencies, the shape and width of the passband, and input impedance of the filter by modification of selected resonant modes. Capacitive loading with higher permittivity dielectrics is shown to be very efficient in decreasing dimensions of microstrip filters with low-permittivity substrates. The designs of novel compact resonators and filters have been developed and the prototypes fabricated by using LTCC technology. The results of prototype measurements agree with the simulation results, which validates the proposed approach

Collegiate Recovery Communities: What They Are and How They Support Recovery

Nearly 2 million American men and women are annually treated for substance abuse (SAMHSA, 2002). Unfortunately, as most substance abuse patients will relapse within a year or even within the first few months (Weisner, Matzger, & Kaskutas, 2002; Bond, Kaskutas, & Weisner, 2003), it is clear that treatment alone does not translate into long-term abstinence. What appears to help many but certainly not all of those wishing to remain abstinent is affiliating with mutual help support groups, such as Alcoholics Anonymous (AA) or Narcotics Anonymous (NA) (Emrick, Tonigan, Montgomery, & Little, 1993; Tonigan, Miller, & Connors, 2000; Tonigan, Tocova, & Miller, 1996).

Delta-Shaped Piezoelectric Ultrasonic Motor for Two-Dimensional Positioning

By fabricating on from lambda-shaped motors, bimorph delta-shaped motors have been developed and tested. A delta motor consists of two piezoelectric layers (bimorph structure) with four input electrodes and one common ground electrode – separated by an inactive bar that aids dimensional control in the sintering process. Two driving sources with a 90° phase difference were used for the x-, z-, and diagonal-axis direction driving. The design of the motor was modified and optimized by changing the relative dimensions and angle of the motor with the aid of ATILA finite element method (FEM) software. The optimum design with a small bandwidth between resonance modes, which provides the largest elliptical displacement, was fabricated using thick films. The fabricated motor size was below 10 mm2 with several hundreds of nano meter motion at the tip. The speed of revolution, torque and efficiency in the two-dimensional space were measured.

Active Optical Fiber Alignment with a Piezoelectric Ultrasonic Motor Integrated Into Low Temperature Cofired Ceramics

The major goal of this research was to integrate an ultrasonic motor into a ceramic package for an active optical fiber alignment. Two degrees of freedom ultrasonic motor was successfully cofired with commercial low temperature cofired ceramic green tapes as well as with silver electrodes without encountering serious delamination, camber, and inter diffusion issues. High-power piezoelectric ceramics that can be sintered at 900°C was used for the ultrasonic motor. The motor successfully achieved fiber-to-laser optical alignment. Once alignment was achieved, a pre-stressed structure maintained the position of the fiber without any external electrical field or adhesive material. This package design provided a unique ability to adjust and realign an optical fiber.

Wearable patch antenna for voice communications with substrate composed of high contrast dielectrics

In this paper we describe a novel microstrip patch antenna with circular polarization based on the substrate of high contrast dielectrics. Engineering design targeted miniaturization and desired electric characteristics, mitigation of surface wave leakage, recovering of fringing fields and ease of fabrication.

Fabrication of Wound Capacitors Using Flexible Alkali-Free Glass

Alkali-free glasses, which exhibit high energy storage densities (~35 J/cc), present a unique opportunity to couple high temperature stability with high breakdown strength, and thus provide an avenue for capacitor applications with stringent temperature and power requirements. Realizing the potential of these materials in kilovolt class capacitors with >1 J/cc recoverable energy density requires novel packaging strategies that incorporate these extremely fragile dielectrics. In this paper, we demonstrate the feasibility of fabricating wound capacitors using 50-μm-thick glass. Two capacitors were fabricated from 2.8-m-long ribbons of thin (50 μm) glass wound into 125-140-mm-diameter spools. The capacitors exhibit a capacitance of 70-75 nF with loss tangents below 1%. The wound capacitors can operate up to 1 kV and show excellent temperature stability to 150 °C. By improving the end terminations, the self-resonance can be shifted to above 1 MHz, indicating that these materials may be useful for pulsed power applications with microsecond discharge times.

A novel, all-dielectric, microwave plasma generator towards development of plasma metamaterials

A proof of concept for a microwave microplasma generator that consists of a halved dielectric resonator is presented. The generator functions via leaking electric fields of the resonant modes — TE01δ and HEM12δ modes are explored. Computational results illustrate the electric fields, whereas the stability of resonance and coupling are studied experimentally. Finally, a working device is presented. This generator promises potentially wireless and low-loss operation. This device may find relevance in plasma metamaterials; each resonator may generate the plasma structures necessary to manipulate electromagnetic radiation. In particular, the all-dielectric nature of the generator will allow low-loss interaction with high-frequency (GHz–THz) waves.

Miniature filter with double-coupled horse-shoe microstrip resonators capacitively loaded by using high-permittivity material

A novel miniature band-pass filter with double coupled horse-shoe microstrip resonators capacitively loaded by using high-permittivity dielectric material is proposed. The transmission line theory and the finite difference time domain (FDTD) method based simulations are used to analyze the performance of filters with normally fed stepped impedance microstrip resonators (SIMR) and to develop the new design. It is demonstrated that the plugs of higher permittivity dielectric used for capacitive loading of stepped impedance sections provide for shrinkage the filter size down several times. The prototypes of the novel filter were fabricated by using the low temperature cofired ceramics (LTCC) technology.