High Permittivity Dielectric Materials Research Articles

Planar SIR microwave bandpass filter using high-permittivity ceramics

High-permittivity dielectric ceramic materials have been applied in the fabrication of a planar stepped-impedance resonator (SIR) microwave bandpass filter. The input/output ports of the filter are formed with transmission lines directly tapped to the resonators. The admittance matrix for the equivalent circuit of the filter has been derived and transformed to the scattering matrix to initially determine the required spec. Losses and other EM effects are taken into account to further modify the actual dimension of the designed filter. The designed structures are simulated using an IE3D simulator. Fabricated filters are measured by an HP8510B network analyzer. Sample results of the filter performances demonstrate responses in good agreement with the computer simulations. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 26: 410–413, 2000.

Ferroelectrics and high permittivity dielectrics for memory applications

In this paper an overview will be given of the field of non-volatile ferroelectric memories with the emphasis on material and processing aspects for high density applications. The emerging field of high permittivity dielectric materials for dynamic random access memories, applying materials closely related to those for ferroelectric memories, will be treated as well.

A nonlinear least-squares solution with causality constraints applied to transmission line permittivity and permeability determination

A technique for the solution of one-port and two-port scattering equations for complex permittivity and permeability determination is presented. Using a nonlinear regression procedure, the model determines parameters for the specification of the spectral functional form of complex permittivity and permeability. The method is based on a nonlinear regression technique and uses the fact that a causal, analytic function can be represented by poles and zeros. The technique allows the accurate determination of many low- and high-permittivity dielectric and magnetic materials in either the low- or high-loss range. The model allows for small adjustments, consistent with the physics of the problem, to independent variable data such as angular frequency, sample length, sample position, and cut-off wavelength. The model can determine permittivity and permeability for samples where sample length, sample position, and sample holder length are not known precisely. The problem of local minima is discussed. >

Tilt sensor for resolving left–right ambiguity in underwater acoustic detection systems

A sensor for resolving the left-right ambiguity encountered in horizontal line hydrophone arrays consists of an orthogonal pair of dipole hydrophones, a monopole hydrophone, and a tilt sensor, the tilt sensor connecting the dipole hydrophones so as to provide a single dipole hydrophone which is always oriented horizontally. The tilt sensor consists of two variable capacitors made from hollow cylinders of high permittivity dielectric material, partially filled with a quantity of liquid mercury which forms the variable inner electrodes of the capacitors. The outer electrodes of the capacitors, on the outside of the cylinders, having a sinusoidally-shaped perimeter and being oriented at right angles to each other, are connected to the crossed dipoles in order to provide the required horizontal dipole hydrophone.

Resonance properties of dielectric-loaded short unipoles

Measurements are presented that show that the input impedance of a coaxially fed short unipole can be brought to resonance by encasing the antenna in a slab of high-permittivity dielectric material. The physical action and likely application of this new antenna configuration are discussed.

Temperature-stable low-loss microwave filters using dielectric resonators

Recently developed high-permittivity low-loss temperature-stable dielectric materials have been used as resonators in microwave filters. The resulting low-loss filters possess extremely good temperature stability. Proper design and the use of metal-screw mode suppressors have eliminated the further problem in dielectric-resonator filters of spurious modes just above the passband.