The construction of mathematical models of micromechanical RF switches, taking into account their design features, the influence of technological factors, as well as the correct choice of materials, contributes to the most accurate design and creation of a switch with specified characteristics. The earlier analysis and study of the technological process of creating a MEMS switch made it possible to determine the groups of factors that have a significant impact on the electrophysical and frequency characteristics. Within the framework of assessing the influence of technological factors on their electrophysical and frequency properties, the influence of such technological parameters as the etching time of various layers and the processing temperature was established. The thickness of the dielectric layer and the membrane and the thickness of the gap between the membrane and the dielectric layer were set as design parameters. Also, a model of a MEMS switch was built, taking into account the influence of design and technological parameters on the characteristics of the switch in the on and off state. Aluminum was used as materials for conducting lines and electrodes, and silicon oxide was used as a dielectric layer. Measurements of the characteristics of the manufactured switches showed a low capacity ratio of the MEMS switch. As a result, it was decided to research and select the most suitable materials for this switch. This paper proposes a methodology for the selection of materials used in the design of an RF MEMS switch. The switches have been redesigned with new materials. Significantly better results were obtained by measuring the switches.
Effective design of micromechanical switches for operation in various frequency ranges is impossible without mathematical models including the correlation of electrophysical parameters with the design and technological parameters of their fabrication. This task is complicated by the fact that different technologies and materials are used to create RF MEMS switch. An earlier analysis of the creation of the MEMS switch allowed us to identify groups of factors that have a significant impact on the electrophysical and frequency characteristics. To assess the influence of technological factors on the electrophysical and frequency properties, technological parameters such as the etching time of various layers, the processing temperature, and material properties such as electrical conductivity, Young's modulus, permittivity, and electrical resistivity were selected. And as design parameters, changes in thickness during the formation of the dielectric layer and the membrane, the thickness of the gap between the membrane and the dielectric layer were considered. In this paper, we construct a MEMS switch model including the influence of design and technological parameters on the characteristics of the switch in the on and off state. Another task is to assess the impact of technological uncontrolled effects that occur under certain conditions in the fabrication of a switch. Electrodynamic modeling of the switch was performed by the finite element method using the mathematical model that includes design and technological parameters. The operation voltage, switching time, the frequency of natural vibrations of the membrane, and the voltage characteristic of the switch were studied. The mathematical model of a micromechanical switch, including the technological parameters of its fabrication, will allow developing technological processes for the fabrication of MEMS switches that match the requirements in the specified frequency ranges and have low losses.
A study of the microwave absorbing properties of coatings based on bulk samples of W-type hexaferites is presented. The link between dielectric and magnetic permeability makes it possible to control their magnetic properties by doping the original composition. Hexaferrites are the most stable system, showing a good rate of absorption and reflection of electromagnetic radiation in the microwave range. The substantiation of the choice of material for the manufacture an absorber of electromagnetic radiation and a brief description of the technology of obtaining a composite absorber based on W-type hexaferrite are given. The results of studying the characteristics of reflection and absorption of electromagnetic radiation based on W-type hexaferrite powder in the frequency range 1 MHz –40 GHz are presented. Recommendations are given on the use of the proposed composite material as an absorber of electromagnetic radiation. It is shown that the use of a composite material for shielding and absorbing EMP has great prospects, while the shielding efficiency depends, first of all, on the type of ceramic material.
The results of the influence of Ti4+ + Сo2+ ions on the magnetic properties of ferrites are presented. It is shown that the increase in the content of Со2+ + ions Ti4+ in the structure of spinel ferrites can be controlled to change as the values of magnetic permeability and temperature of the phase transition to the paramagnetic state. Magnetic and dielectric properties of ferrites are closely related to their chemical transformations during synthesis and temperature treatment. Temperature treatment, provides homogenization and formation of ceramic structure. The paper considers ferrite systems as phases of variable composition formed in the process of temperature treatment. Specific examples are given of modern ideas about the physic-chemical nature of the processes of synthesis of ceramics. The obtained samples are characterized by high density, micron size of crystallites, uniform distribution of alloying impurities, chemical homogeneity.
The paper presents an assessment of the accuracy of the method of choosing an integration variable for the numerical solution of the Cauchy problem in terahertz range. An example of using the method to determine ray paths in inhomogeneous media in the approximation of geometric optics is given. Unlike numerical methods of integration, where one pre-selected variable is used as an integration variable, in the considered method the integration variable is selected at each step. This approach reduces the risk of shifting to adjacent phase trajectories, which is especially important in the terahertz range. In addition, we note that using this approach allows you to effectively use computer resources. The integration method with the choice of the integration variable at each step is described. A feature of the method is that the variable with the highest rate of change is selected as the integration variable. The accuracy of the method is investigated by the example of a problem with a well-known analytical solution. The dependence of the relative error of the solution on the grid pitch is investigated. Extreme values of the grid pitch at which the relative error drops sharply are calculated. The dependence of the relative error of the solution on the direction of propagation of the rays is investigated. Shows the application of the numerical modeling algorithm for the example of constructing ray paths in inhomogeneous media in the approximation of geometric optics for geometry with three spatial coordinates. The ray paths in 3D space are presented.
This paper demonstrates the development of the analytical method of suppression of radiation pattern (RP) side lobes which is based on Woodward-Lawson method with three basic functions. The considered method allows to suppress the side lobes of the RP in a wide range of angles. It also allows to suppress RP side lobes in a desired direction. This approach can be used in digital antenna systems and the multibeam active phased antenna arrays. In the first part of the paper, linear phased antenna array (LPAA) consisting of isotropic equispaced radiators and methods of suppression of side lobes and creation of the operated minimum in a LPAA radiation pattern are considered. In the second part of the paper partial diagram method is considered. It is shown how to control the RP side lobes in wide range of angles. In the third part of the paper it is shown how to suppress RP side lobes in a desired direction. The fourth part of the paper shows how to synthesize amplitude and phase distribution to control RP side lobes. The method presented in this work allows to reduce the level of the side lobes of the radiation pattern by more than 50 dB in a wide range of angles, or in a given direction. Expressions for calculating the amplitude and phase distributions forming a minimum RP in a given direction are presented. Using LPAA with a given number of emitters, the use of the technique is demonstrated.
Development of the integration variable selection method for the numerical solution of the Cauchy problem is demonstrated. This method is applicable for the simulation of electromagnetic wave propagation in inhomogeneous media by geometric optics approximation. Usually, in the methods of the numerical solution of the Cauchy problem, the integration is carried out according to one pre-selected variable. This approach does not seem to be the most cost-efficient in terms of computing resources.
The equations of rays and eikonal in finite differences are considered, taking into account the anisotropy of the refractive index. The paper presents a block diagram of the algorithm for choosing the variable of integration. The integration is carried out on the variable selected at the current step, which is assigned the specified step value. The increments of the remaining variables are calculated by expressions depending on the selected integration variable so that the increments on the remaining variables do not exceed the value of the integration variable. The integration variable is selected again and the increments are calculated. This method saves computational resources and minimizes the risk of transition to adjacent phase trajectories. The paper presents a general flowchart of the selection algorithm and expressions for calculating the increments of other variables at each step. The algorithm for calculating increments for each variable is demonstrated. The variable selection algorithm is developed for the case of a 7-dimensional phase space. It includes the projection of the pulse on the three axes of the Cartesian coordinate system, the projection of the coordinate and the phase component. The phase component describes the phase of the wave at the selected point and is analogous to the time dependence.
The 2D electromagnetic modeling distribution of electric fields for stationary and non-stationary scattering process in the time domain mode was developed. The distributing system of the optical type was expressed. Given system allows to form 5-beam directional pattern (DP) for receiving active phased antenna radar (APAR).
At reduction of the sizes of the distributing system, distance between its output reduce in once, in contrast with distance between radiators APAR. In such event corner deflections of the ray in DP APAR will corner of the deflection less in distributing system in n once also. For considered systems reduction factor of the geometric sizes n has formed the order 7. In corresponding to number once and was increased a corner of the deflection of the ray α in distributing system.
The creation of effective procedures for the design and fabrication of RF MEMS switches with specified electrophysical properties for operation in different frequency ranges is an urgent task. This is due to the widespread use of RF MEMS in various fields of microelectronics. The task is complicated by the fact that, based on the areas of application, different variants of technologies, materials, topological and structural solutions are used to create RF MEMS switches. The article proposes a method of design and fabrication of RF MEMS switch with specified properties based on creating a model of micromechanical switch, taking into account significant technological parameters, properties of materials and options for structural and topological solutions. For the selected three groups of factors, the analysis of the main characteristics and parameters affecting the electrophysical and frequency properties of RF MEMS switch is carried out. The analysis of technological processes of fabrication allowed determining the influence of the non-etched photoresist layer on such electrophysical characteristics as the capacity of the switch in the up- and down-state. The analysis of the properties of materials, the influence of thickness changes in the formation of the dielectric layer and membrane, as well as the thickness of the gap between the membrane and the dielectric layer on the electrophysical and frequency properties of RF MEMS switch. It is established that the most significant parameters affecting the formation of the frequency characteristics of the switch is the change in its geometric dimensions. The developed model RF-MEMS switch, which takes into account the interaction highlighted important properties and relations with the electrical and frequency characteristics of RF MEMS switch. Modeling and analysis of the following characteristics (consequences of the model) RF MEMS switch.
The results of numerical electrodynamic modeling and experimental research of slotted waveguide radiator is presented. The operational frequency was decreased on 25%. It was found that the differences between the experimental and calculated characteristics are associated with the following factors: the inaccuracy of manufacture of the geometric dimensions of the slotted waveguide radiator, methodical error of the finite element method in calculating the characteristics, inaccuracy of the values of the relative permittivity and magnetic permeability.
The results of the study saturation magnetization and crystallographic anisotropy doped with diamagnetic ions of hexagonal ferrites are presented. It is shown that the impedance matching properties of ferrimagnetic fillers depend on equality values of magnetic and dielectric permittivity composite material in the working wave band. The contribution of the proposed replacement complexes to the magnetic and dielectric permittivity resulting materials is determined. Magnetostatic and electrodynamic properties of composites based on doped hexaferrites type M and Z are studied. Hexagonal ferrites, which play the role of an impedance matching medium in frequency range 0.1-3 GHz, are obtained. Recommendations are offered on the possibility using impedance matching composite hexagonal ferrites in the development filtering and frequency separation systems.
The usage of impedance matching materials for millimeters waves in antenna systems is a promising direction in the development of modern radar stations that allows unifying nomenclature of radiating elements. One of possible appliances of impedance matching materials is transfer of working frequencies of radiating elements to bands with greater wavelength. The usage of several impedance matching mediums, for example, with εr=μr=2, εr=μr=4, εr=μr=8, εr=μr=10 allows to extend waveband of the radiating element by 2, 4, 8 and 10 times.
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