Waveguide Port Approach in EM Simulation of Microwave Antennas

This chapter generalizes a recently proposed MoM-based approach to waveguide port excitation (WPE) problems on arbitrary conducting and composite geometries. This approach combines the canonical aperture coupling approach with the EFIE-PMCHWT formulation for composite structures. Each WPE problem in this approach is divided into equivalent sub-problems for internal and external regions, which are solved using the MoM. Internal WPE problems are solved using waveguide modal expansion in the port plane, while external problems are solved using the equivalence principle to reduce these problems to the systems of algebraic equations for unknown electric and magnetic currents. The developed approach is validated on radiation and coupling problems for coaxial ports by comparing simulated results with those obtained by other approaches and measurements. An excellent agreement between the simulated and measured results is demonstrated. Finally, this approach is applied to practical EMC problems for microwave antennas fed by coaxial ports

GO-PROMTO Illuminates Protein Membrane Topologies of Glycan Biosynthetic Enzymes in the Golgi Apparatus of Living Tissues

The Golgi apparatus is the main site of glycan biosynthesis in eukaryotes. Better understanding of the membrane topology of the proteins and enzymes involved can impart new mechanistic insights into these processes. Publically available bioinformatic tools provide highly variable predictions of membrane topologies for given proteins. Therefore we devised a non-invasive experimental method by which the membrane topologies of Golgi-resident proteins can be determined in the Golgi apparatus in living tissues. A Golgi marker was used to construct a series of reporters based on the principle of bimolecular fluorescence complementation. The reporters and proteins of interest were recombinantly fused to split halves of yellow fluorescent protein (YFP) and transiently co-expressed with the reporters in the Nicotiana benthamiana leaf tissue. Output signals were binary, showing either the presence or absence of fluorescence with signal morphologies characteristic of the Golgi apparatus and endoplasmic reticulum (ER). The method allows prompt and robust determinations of membrane topologies of Golgi-resident proteins and is termed GO-PROMTO (for GOlgi PROtein Membrane TOpology). We applied GO-PROMTO to examine the topologies of proteins involved in the biosynthesis of plant cell wall polysaccharides including xyloglucan and arabinan. The results suggest the existence of novel biosynthetic mechanisms involving transports of intermediates across Golgi membranes

Validation of Hybrid MoM Scheme for Composite Geometries with Layered Structures

In this work, the previously developed hybrid MoM scheme with special Green\u27s function is applied to modeling the composite geometries with layered structures. A good matching of simulated results obtained by this approach with direct multi-dielectric MoM approach and with measurements is demonstrated. The computational efficiency of hybrid MoM approach against the direct MoM is concluded

Analysis and Design of Multiport Waveguide Junctions with Artificial Inclusions Made of Cylindrical Rods

A rigorous electromagnetic theory is developed to analyze multiport waveguide junctions with artificial inclusions made of cylindrical rods and placed in the main arm. The scattering characteristics of a 3-port junction are discussed with the numerical examples for the SWR maps, the power reflection and transmission coefficients, and the 3D plots of near fields inside the junction area. A strategy to optimize matching properties of the 3-port waveguide junctions is also described

DEVELOPMENT AND APPLICATION OF AN ENHANCED MOM SCHEME WITH INTEGRATED GENERALIZED N-PORT NETWORKS

Abstract—This paper proposes an enhanced MoM scheme to integrate arbitrary N-port networks into geometry models. This scheme is based on the incorporation of network equations into the standard MoM scheme. The suggested scheme is validated by comparison of the characteristics of a linear amplifier with those obtained by PSPICE. A general application of the enhanced MoM scheme is to handle complicated antenna or EMC problems including various types of network devices. Its potential to handle antenna-amplifier systems, automotive or other EMC problems is outlined. 1