Sda full-wave analysis of boxed multistrip lines of finite thickness embedded in a layered lossy medium

Spectral-domain approach (SDA) is applied to modeling propagation characteristics of multiconductor structure on superconducting strip lines with signal strips and ground planes of finite thickness in lossy layered media. Equivalent surface impedance is used to transform the superconducting strip of finite thickness into an infinitely thin strip. A novel procedure of a calculation of the equivalent surface impedance is proposed. Two sets of basis functions (Chebyshev and Legendre polynomials) are compared by their ability to accurate modeling of microwave losses in the structure. The model applicability is illustrated by numerical results compared with experimental and simulated data

Figure of Merit and Limiting Characteristics of Tunable Ferroelectric Microwave Devices

Abstract Microwave application of ferroelectrics is very promising for electrically tunable microwave devices based on the electric field dependence of the dielectric permittivity. Tunable filters and controllable phase shifters are successfully designed as integrated circuits based on multilayer structures containing thin epitaxial ferroelectric (FE) film. As a rule lumped ferroelectric capacitors are used as the tunable components. Quality of the capacitor can be evaluated using Commutation Quality Factor (CQF). There is a unique connection between th

Paraelectric in a Strong High-Frequency Field

A change in the effective permittivity of a ferroelectric film in the paraelectric phase under the action of a strong high-frequency field (nonequilibrium soft mode heating) is considered. It is shown that this effect must be most clearly pronounced far from the resonance (\omega_0 << \omega_sm), rather than for the external field frequency \omega_0 close to the soft mode frequency \omega_sm. The effective permittivity as a function of the high-frequency field amplitude is calculated using the phenomenological approach and within the microscopic theory based on the simple model of a displacement-type ferroelectric.Comment: 3 two-column page

High frequency polarization switching of a thin ferroelectric film

We consider both experimentally and analytically the transient oscillatory process that arises when a rapid change in voltage is applied to a $Ba_xSr_{1-x}TiO_3$ ferroelectric thin film deposited on an $Mg0$ substrate. High frequency ($\approx 10^{8} rad/s$) polarization oscillations are observed in the ferroelectric sample. These can be understood using a simple field-polarization model. In particular we obtain analytic expressions for the oscillation frequency and the decay time of the polarization fluctuation in terms of the material parameters. These estimations agree well with the experimental results

Microwave Current Imaging in Passive HTS Components by Low-Temperature Laser Scanning Microscopy (LTLSM)

We have used the LTLSM technique for a spatially resolved investigation of the microwave transport properties, nonlinearities and material inhomogeneities in an operating coplanar waveguide YBa_2Cu_3O_{7-\delta} (YBCO) microwave resonator on an LaAlO_3 (LAO) substrate. The influence of twin-domain blocks, in-plane rotated grains, and micro-cracks in the YBCO film on the nonuniform rf current distribution were measured with a micrometer-scale spatial resolution. The impact of the peaked edge currents and rf field penetration into weak links on the linear device performance were studied as well. The LTLSM capabilities and its future potential for non-destructive characterization of the microwave properties of superconducting circuits are discussed.Comment: 8 pages, 9 figures, 2-column format, presented at High Temperature Superconductors in High Frequency Fields 2004, Journal of Superconductivity (in press

Past Achievements and Future Challenges in 3D Photonic Metamaterials

Photonic metamaterials are man-made structures composed of tailored micro- or nanostructured metallo-dielectric sub-wavelength building blocks that are densely packed into an effective material. This deceptively simple, yet powerful, truly revolutionary concept allows for achieving novel, unusual, and sometimes even unheard-of optical properties, such as magnetism at optical frequencies, negative refractive indices, large positive refractive indices, zero reflection via impedance matching, perfect absorption, giant circular dichroism, or enhanced nonlinear optical properties. Possible applications of metamaterials comprise ultrahigh-resolution imaging systems, compact polarization optics, and cloaking devices. This review describes the experimental progress recently made fabricating three-dimensional metamaterial structures and discusses some remaining future challenges

A Miniaturized branc-line directional coupler on low temperature cofired ceramic board

This paper outlines the capability to develop a 3D compact-size branch-line directional coupler within the LTCC process. The substrate of Dupont Green Tape TM ceramic has been successfully utilized to manufacture 3-dB 9