Nonlinear Loss Model In Absorptive-Type Ferrite Frequency-Selective Limiters

Absorptive-type ferrite-based frequency-selective limiters (FSLs) utilize nonlinear (NL) phenomena in magnetized ferrites to provide real-time analog signal processing of RF/microwave electromagnetic (EM) signals. There are no commercially available modeling tools that simulate these interactions, and the development and optimization of FSLs are largely done experimentally. FSL modeling and design is complicated by NL, multiscale, and Multiphysics nature of operation. In this article, an NL loss model in a ferrite is proposed and implemented in an efficient numerical algorithm. The equivalent linear magnetic loss tangent is represented in a closed form. A full-wave numerical EM model with high-fidelity meshing is set up so that material properties are assigned to each mesh element and are iteratively adjusted depending on the local magnetic field. The numerical model is sliced along the EM wave propagation, and an NL eigenvalue is obtained for each slice as a function of frequency, power, and external magnetic bias field and stored in lookup tables. The slices are cascaded, and power attenuation is calculated with loss changing along the wave path according to the lookup tables. The resulting data are processed to be suitable for equivalent circuit models. Numerical results for coplanar waveguide FSL are validated by measurements. The proposed modeling approach is useful for engineering FSL devices

Full-wave EMC Simulations Using Maxwell Garnett Model For Composites With Cylindrical Inclusions

Four different models for effective dielectric properties of biphasic composite containing random or aligned cylindrical inclusions are considered in this paper. These models are based on the Maxwell Garnett (MG) mixing rule. The effects of distribution and orientation of cylindrical inclusions in a composite material is studied. An equivalent averaged material with Debye-like frequency characteristics, suitable for time-domain full-wave numerical electromagnetic simulations is retrieved. This Debye model is derived from the Maxwell Garnett formulation. The numerical model test structure consists of a composite slab inserted in a rectangular waveguide. Simulations are run for the frequency range above the cut-off frequency of the fundamental mode TE10. The differences between the proposed models are quantified using the Feature Selection Validation (FSV) tool. The comparison of the models provides an insight on the effect of inclusion orientation and distribution. © 2011 IEEE

External Parasitic Inductance in Microstrip and Stripline Geometries of Finite Size

An external parasitic ground (return) plane inductance, or a mutual inductance associated with fringing magnetic fields in planar transmission line structures, is the culprit of common-mode voltage (ground plane noise) that leads to parasitic radiation of the corresponding unintentional antennas in high-speed electronic equipment. Mutual inductance of this sort in microstrip and stripline structures is studied here using an analytical quasi- magnetostatic approach and FDTD modeling. Closed-form expressions for mutual inductance in symmetrical and asymmetrical microstrip and stripline structures are presented

Mutual External Inductance in Stripline Structures

The Method of Edge Currents (MEC) proposed in our previous paper [1] is applied herein for calculating the mutual external inductance associated with fringing magnetic fields that wrap ground planes of a stripline structure. This method employs a quasi-static approach, image theory, and direct magnetic field integration. The resultant mutual external inductance is frequency-independent. The approach has been applied to estimating mutual inductance for both symmetrical and asymmetrical stripline structures. Offset of the signal trace from the centered position both in horizontal and vertical directions is taken into account in asymmetrical structures. The results are compared with numerical simulations using the CST Microwave Studio Software

Method of Edge Currents for Calculating Mutual External Inductance in a Microstrip Structure

Mutual external inductance (MEI) associated with fringing magnetic fields in planar transmission lines is a cause of socalled ground plane noise , which leads to radiation from printed circuit boards in high-speed electronic equipment. Herein, a Method of Edge Currents (MEC) is proposed for calculating the MEI associated with fringing magnetic fields that wrap the ground plane of a microstrip line. This method employs a quasi-magnetostatic approach and direct magnetic field integration, so the resultant MEI is frequency independent. It is shown that when infinitely wide ground planes are cut to form ground planes of finite width, the residual surface currents on the tails that are cut off may be redistributed on the edges of the ground planes of finite thickness, forming edge currents. These edge currents shrink to filament currents when the thickness of the ground plane becomes negligible. It is shown that the mutual external inductance is determined by the magnetic flux produced by these edge currents, while the contributions to the magnetic flux by the currents from the signal trace and the finite-size ground plane completely compensate each other. This approach has been applied to estimating the mutual inductance for symmetrical and asymmetrical microstrip lines

Electrical Material Property Measurements using a Free-Field, Ultra-Wideband System [Dielectric Measurements]

We present nondestructive measurements of material properties using TEM horn antennas and an ultra-wideband measurement system. Time-domain gating and genetic algorithms are used to process the data and extract the dielectric properties of the material under test

Contrast joints of glass-fibre with carbon-fibre reinforced low density polyethylene composite bonded by microwave irradiation

This paper contrasts the loss tangent, durability of reinforcement and the lap shear strengths of 33 percent by weight random glass fibre reinforced low density polyethylene matrix composite [LDPE/GF (33%)] with 33 percent by weight random carbon fibre reinforced low density polyethylene matrix composite [LDPE/CF (33%)] bonded using microwave irradiation. Fixed (2.45 GHz) and variable (2 – 18 GHz) frequency microwave (VFM) facilities are used to bond the two composites. With a given power level, the composites were exposed to various exposure times to microwave irradiation. The primer or coupling agent used for joining the glass-fibre-reinforced composite was 5-minute two-part adhesive, Araldite. No filler was used in joining the carbon-fibre-reinforced composite

Modeling of shielding composite materials and structures for microwave frequencies

Abstract—Composites containing conducting inclusions are required in many engineering applications, especially, for the design of microwave shielding enclosures to ensure electromagnetic compatibility and electromagnetic immunity. Herein, multilayer shielding structures are studied, with both absorbing and reflecting composite layers. In this paper, fiber-filled composites are considered. For modeling absorbing composites with low concentration of conducting cylindrical inclusions (below the percolation threshold), the Maxwell Garnett theory is used. For reflecting layers, when concentration of inclusions is close to or above the percolation threshold, the McLachlan formulation is used. Frequency dependencies for an effective permittivity are approximated by the Debye curves using a curve-fitting procedure, in particular, a genetic algorithm. Corresponding author: M. Y. Koledintsev