Millimeter wave twin slot antennas on layered substrates

We have constructed a planar, monolithic twin slot antenna integrated with a bismuth microbolometer detector for operation near 94 GHz. In this paper, we briefly discuss the theory of operation for planar antennas on a dielectric stack. We then cover the fabrication details, including a short discussion of a photoresist bridge technique used to fabricate the microbolometer detectors. Measured receiver gain beam patterns are then compared with theoretical patterns for a number of cases.This work was supported by the National Science Foundation under grant number ECS-8552868 and by the Joint Services Electronic Program under grant number AFOSR 49620-89-0044.     

Physical principles of plasma dipole and slot antennas

Basic principles of plasma antennas operating on bulk and surface plasma waves are described. It is shown that the efficiency of plasma antennas is highly competitive with that of metal antennas and their controllability is far superior. Two types of plasma antennas are considered, i.e., the dipole ones operating on the surface plasma wave and the waveguide slot antennas operating on the bulk plasma wave.     

Analysis of the scattering properties of defects of layered substrates

The light scattering by defects of a layered substrate, such as foreign particles on a film and damages of the film itself, is analyzed. The analysis of the scattered light intensity is based on the generalization of the method of discrete sources. To identify defects of different kinds, it is proposed to use the integral scattering characteristics of polarized light.     

Formation and mobility of droplets on composite layered substrates

A mesoscale fluid film placed on a solid support may break up and form droplets. In addition, droplets may exhibit spontaneous translation by modifying the wetting properties of the substrate, resulting in asymmetry in the contact angles. We examine mechanisms for droplet formation and motion on uniform and terraced landscapes, i.e., composite substrates. The fluid film stability, droplet formation and velocity are studied theoretically in the isothermal case using a lubrication approach in one spatial dimension. The droplet properties are found to involve contributions from both the terraced layer thickness and molecular interactions via the disjoining potential.     

Modified slot antennas on high-permittivity substrates for the millimeter-wave range

We consider the possibility of manufacturing a planar antenna on the dielectric layer with high permittivity, which is intended for a monolithic planar detector of the millimeter-wave range. The previous design of the slot antenna on a foil-cladded dielectric with low permittivity (ε = 2.2) is analyzed. The simulation results show that a transition from the substrate with low dielectric permittivity to a semi-insulating GaAs substrate (ε ≈ 13) with the directivity kept at a level of about ∼10 at the resonant frequency is possible for antennas with external sizes comparable with the wavelength. The parameters of the planar detectors on semi-insulating GaAs substrates in the 3-mm wavelength range (94–97 GHz) were measured. Directional patterns of the planar antennas at the resonant frequencies reasonably coincide with the calculated data. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 10, pp. 864–871, October 2008.     

Resonant transmission of terahertz waves through metallic slot antennas on various dielectric substrates

We report on terahertz electromagnetic field transmission through metallic slot antennas supported on various dielectric substrates. The substrate effect strongly modifies the transmission resonance compared to the free-standing case, while the resonance can be determined systematically by introducing an effective refractive index. The relative contribution of the substrate index to the effective index has been measured for various substrates, and shows a good agreement with theoretical calculations based on a coupled mode method. In addition, the slot antenna arrays embedded in a flexible substrate show a transmission resonance governed by a substrate refractive index.     

Radiation of an electric dipole located on the “Coastline”

The radiation characteristics of a vertical electrical dipole located in a narrow transition domain with a different law of impedance variation, as calculated from [4] and [5], are compared with the results in [2]. The sense of the solutions formally obtained earlier is discussed [1, 2]. The process of radiowave propagation along tracks inclined slightly to the coastline is investigated numerically.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 91–95, September, 1972.     

A twin slot antenna on a layered substrate coupled to a microstrip feed line

A method is described for calculating the input impedance as seen by the detector for a twin slot antenna structure. This technique is then used to analyze several twin slot antenna configurations, leading to improved performance.     

Computation of electric dipole matrix elements for hydrogen fluoride

The electric dipole matrix elements of hydrogen fluoride have been calculated by numerical integration for transitions involving large quantum numbers υ, J. Overtones have been included through Δυ = 5. Molecular wave functions obtained by numerical integration of the Schrödinger equation were used. The influence of the mechanical motion on the matrix elements has been determined for Morse and Rydberg-Klein-Rees (RKR) potential functions. The influence of the electric dipole-moment function approximations has been investigated by a comparison of matrix elements obtained with approximations having the form of a truncated polynomial and a wave-function expansion. The inaccuracies in the matrix elements caused by uncertainties in the dipole-moment coefficients have been investigated.     

Elastic properties of layered crystals

The characteristic features of the elastic properties of layered crystals and their dependence on temperature and pressure are analyzed. The relations between the elastic constants of hexagonal layered crystals are given. It is shown that the anomalous behavior of the elastic constants in the temperature region of a phase transition affects both the magnitude and sign of the thermal expansion coefficients of layered crystals. From analyzing the pressure and temperature dependences of the elastic constants, it is found that the anharmonicity of the bonding forces between the layers is much greater than the anharmonicity of the intralayer forces. The contribution from thermal expansion to the variations of the elastic constants with temperature is estimated.     

Magnetic properties of two-dimensional and layered systems

We consider two-dimensional magnetic systems and compare our results with experimental data on (C₂H₅NH₃)₂CuCl₄.     

Synthesis and properties of layered perovskite compounds

Bi₂A _{n ? 1} B _n O_{3n + 3} ceramics are fabricated where A and B are ions of Ti, W, Pb, Nb, and Mo. The process of synthesis is studied, and the changes in the charge mass and volume during sintering are determined. The ceramic production process is optimized. The dielectric properties of the ceramics are investigated, and the factors affecting the diffuseness of phase transitions are revealed.     

磁偶极和电四极在磁各向异性介质中的辐射功率

在经典电动力学的框架下,研究了磁各向异性介质中的电磁辐射问题,得到了磁偶极和电四极在磁各向异性介质中的辐射功率表达式.进一步地,通过把各向同性介质中的μrii代入所得辐射功率表达式,得到了与文献相符合的结果,验证了所得结果的正确性.研究结果表明磁偶极和电四极在磁各向异性介质中的辐射功率大小与磁各向异性介质的μrii大小有关,对判断磁偶极和电四极在磁各向异性介质中的辐射效果有较大的帮助.     

Isoscalar monopole and dipole transition matrix elements from inelastic alpha scattering

Using an implicit folding procedure, isoscalar monopole and dipole transition matrix elements are expressed in terms of deformation parameters and moments of the optical potential forα-scattering. Application to monopole states in light nuclei gives good agreement with data determined electromagnetically. For isoscalar dipole states, the method gives information on 〈r ³〉 matrix elements which cannot be obtained otherwise.     

曲率对有限曲面狭缝阵列传输特性的影响

扩展互导纳法用于研究有限曲面狭缝阵列的传输特性,分析了一维弯曲效应以及单元列数、曲率等因素对磁流分布、散射方向图及频率响应曲线的影响.结果表明,曲面张角是衡量弯曲效应的主要参数. 当曲面张角较大时(120°以上),弯曲效应显著,单元磁流分布剧烈起伏,散射方向图波束展宽且副瓣电平升高,谐振频率、传输带宽及功率透射系数等频率响应特性均发生较大变化.当曲面张角较小时(60°以下),仅边缘附近的单元磁流分布受到曲率影响,散射方向图与传输特性均接近于有限平面阵列,表明此时可近似忽略弯曲效应. 关键词： 频率选择表面 狭缝阵列 传输特性 曲率     

Radiation stability of nanoscale ferromagnetic memory elements

Computer-simulation data on the radiation-induced processes in nanoscale ferromagnetic clusters exposed to charged and neutral particles are presented. An instability-zone radius that characterizes the material’s radiation stability is estimated for an atom knocked out from a lattice site. Temperature and thermoelastic effects in the clusters and their influence on the defect structure of the irradiated objects are considered.     

Wetting properties of rare gases on weak substrates

Since the original prediction that liquid He does not wet Cs at low temperatures and the soon after experimental observation of a wetting transition on this system, noble gases on alkalis have become model systems for the study of wetting transitions and of their accompanying line of prewetting transitions off coexistence. Here we review very briefly the theory of wetting and prewetting and discuss some results on the properties of rare gases adsorbed on alkali surfaces obtained with the use of the density functional theory and of accurate adsorbate-substrate potentials.