A General Mode Matching Technique applied to Bandpass Radomes

A new method based on the mode matching technique and the finite element method (FEM) is presented. The method can handle a general thick frequency selective structure (FSS), that consists of an arbitraryn umber of aperture layers and dielectric layers. An aperture layer consists of a conducting plate with a periodic arrayof apertures. The order and the thickness of the layers can be arbitrary. The aperture can have arbitrary cross-section, and these cross-sections can be changed stepwise. The apertures can also be filled with a dielectric material. The method for the bandpass radomes is based on general mode matching technique and cascade coupling. The fields outside the FSS and inside the dielectric layers are expanded in Floquet modes. Inside the aperture layers the fields are expanded in waveguide modes, which are calculated with FEM. Bya mode matching technique, a scattering matrix is calculated for every boundarysurface and a propagation matrix is calculated for everyla yer. These matrices are cascade coupled to form a scattering matrix for the complete FSS. The method has been verified bycomparison with other methods and measurements

Closed-Form Approximation for Parallel-Plate Waveguide Coefficients

Simple closed-form formulas for calculating coefficients of modes excited in a parallel-plate waveguide illuminated by a planar wave are presented. The mode-matching technique and Green’s formula are used to arrive at a matrix-based expression for waveguide coefficients calculation. Simplified solution to this matrix is proposed to derive approximate mode coefficient formulas in closed-form for both TE and TM polarization. The results are validated by numerical simulations and show good accuracy for all incidence angles and in broad frequency range

Analysis of lateral leakage loss in silicon-on-insulator thin-rib waveguides

The lateral leakage behaviour of TM-based silicon-on-insulator thin-rib waveguides is analysed using mode matching technique. Both the TM-TE mode coupling properties and the leakage loss of propagating TM mode are investigated

A mode-matching analysis of dielectric-filled resonant cavities coupled to terahertz parallelplate waveguides

We use the mode-matching technique to study parallel-plate waveguide resonant cavities that are filled with a dielectric. We apply the generalized scattering matrix theory to calculate the power transmission through the waveguide-cavities. We compare the analytical results to experimental data to confirm the validity of this approach

Mode matching technique for computation of resonance frequencies of composite metal-dielectric resonator

Задача на власні коливання метало-діелектричного резонатора зведена до системи однорідних інтегральних рівнянь Фредгольма першого роду, яка розв’язана методом Галеркіна. Обчислювальна процедура ефективніша метода скінченних елементів. Показана висока чутливість резонансних частот нижчих типів коливань від величини повітряної щілини між металевою площиною та діелектриком, що може бути використано для створення компактних мікромеханічно-керованих резонансних елементів.The composite metal-dielectric resonator (CMDR) design is presented. An eigenproblem solution of the CMDR by mode matching technique is discussed. The problem is reduced to a set of homogeneous integral Fredholm equations of the first kind. The system is solved using Galerkin method. The technique is more efficient than FEM in terms of computational resources due to low rank of the system. It is shown that changing the air gap width between the dielectric and the metal plate provides the resonant frequency tuning. It is also shown that in order to achieve efficient electromechanical tuning of the CMDR resonant frequency, the resonant modes with a dominant electrical field component perpendicular to the air gap between the dielectric and the metal plate have to be selected. The tuning efficiency grows with the DR radius to thickness ratio and increasing permittivity. The CMDR can be used for creating compact high-Q micromechanical-tuned radiofrequency devices with wide tuning range.Задача о собственных колебаниях металло-диэлектрического резонатора сведена к системе однородных интегральных уравнений Фредгольма первого рода, которая решена методом Галеркина. Вычислительная процедура эффективнее метода конечных элементов. Показана высокая чувствительность резонансных частот низших типов колебаний от величины воздушного зазора между металлической плоскостью и диэлектриком, что может быть использовано для создания компактных микромеханически-перестраиваемых резонансных элементов

Electromagnetic Analysis of Horn Antennas in the Terahertz region

This thesis is concerned with the application of electromagnetic modelling techniques to the analysis of horn antenna characteristics over the terahertz range, 0.1 THz to 5 THz. The mode matching technique based on a scattering matrix approach to describe beam propagation in both the forward and backward direction is applied to the analysis of conical and pyramidal horn antenna both single and multi-moded, in particular the multi-moded pyramidal horn antenna array of the SAFARI instrument - a far infrared imaging spectrometer to be launched onboard the future SPICA mission. A second electromagnetic method - the finite integration technique is applied to the analysis of simple waveguide structures and characteristics associated with them through commercially available package CST. Where appropriate a quasi-optical approach to the analysis is also applied for comparison and verification of the results, namely Gaussian beam mode analysis. The underlying theory behind these analytical techniques and their implementation is provided along with descriptions of software packages used in the analysis, these are μWave Wizard a commercially available software package based on the mode matching technique, CST Microwave studio commercially available software utilising the finite integration technique and SCATTER code developed at NUI Maynooth using the mode matching technique. Gaussian beam mode propagation using both Gauss-Laguerre and Gauss-Hermite mode sets is implemented by code written within the Mathmatica environment. The effectiveness of each method in its application to particular structures to obtain accurate and computationally feasible results is discussed. Particular effects inherent is quasi-optical systems, crosstalk and standing wave effects are analysed in addition in later chapters. These effects are analysed both experimentally using a vector network analyser and within appropriate computational models