Giacomo Guarnieri

Reduction of Patch Antenna Coupling by Using a Compact EBG Formed by Shorted Strips With Interlocked Branch-Stubs

This letter presents a new type of planar electromagnetic band-gap (EBG) surface composed of short-circuited microstrips densely coupled with each other through interlocked branch stubs. With respect to a conventional mushroom surface, this structure exhibits a better space-wave decoupling performance due to the soft nature of the surface. With respect to other soft surfaces, like shorted strip already introduced in the literature, the present solution possesses better miniaturization properties, thus allowing the use of lower permittivity and consequent improvements when integrated in planar dense arrays. The experimental results demonstrate a decoupling until 38 dB in both planes for patches separated by only one half free-space wavelength.

Large Depth of Field Pseudo-Bessel Beam Generation With a RLSA Antenna

The paper discusses the possibility of generating a pseudo-Bessel beam, with a propagation distance of several hundreds of wavelengths in microwave and millimeter frequency band, by using a radial line slot array (RLSA). A specific application for non-contact microwave detection of buried mines has been considered as test case. The design benefits of a holographic approach to assure the required aperture field distribution and makes use of an ad hoc optimization tool to control the antenna slot layout. The predicted and measured antenna behaviors show that high efficiency and polarization purity can be obtained by such a compact and flat antenna, achieving at the same time both manufacturing and setup simplicity.

An Efficient Perturbative Approach for Finite-Element Analysis of Microwave Devices Exhibiting Small Geometrical Variations

An innovative method for fast analysis of geometrical variations in electromagnetic wave problems is proposed. The method is based on a perturbative approach applied to the solution of the linear integro-differential operator of the electromagnetic problem in presence of small domain modifications. This approach has been embedded in a classical finite-element framework to achieve a very fast technique for field evaluation in synthesis or tolerance investigation of microwave passive devices. The proposed technique can handle geometrical variations without the need of re-meshing the domain and without any deformation of the original mesh of the problem.

The Parabolic Equation Method for the High-frequency Scattering from a Convex Perfectly Conducting Wedge with Curved Faces

The parabolic equation method permits one to develop valuable and flexible techniques to solve high frequency scattering problems in wedge shaped regions. This method is here applied to solve the two-dimensional problem of plane wave scattering from a convex perfectly conducting wedge with curved faces. The results provided by the parabolic model are compared on a test-case problem with the numerical results obtained by a hybrid Finite Element-based approach. These results prove that in the far-field scattering region the parabolic equation approach is able to provide results of the same quality of the hybrid Finite Element approach, but with a 96% reduction of the computational time.

A Domain Decomposition Technique for Efficient Iterative Solution of Nonlinear Electromagnetic Problems

An innovative method for fast analysis of electromagnetic problems comprising nonlinear dielectrics is proposed. The method is based on the combination of finite elements and domain decomposition methods. This latter technique allows for the separation of the problem in multiple subproblems which can be solved separately. By appropriately defining one of such subdomains as containing all the nonlinear dielectrics it is possible to restrict the application of an iterative algorithm for the numerical solution of nonlinear equations only to this latter, smaller, domain. Numerical results showing the accuracy and efficiency of this technique are presented in few 2D cases.

FE‐DD based permittivity tolerance analysis in microwave waveguide filters

Purpose – The papers aim is to devise a fast method for microwave waveguide filter permittivity tolerance analysis.Design/methodology/approach – A 2D finite elements (FEs) formulation is combined via a Schur complement‐based domain decomposition (DD) technique to reduce the tolerance affected part of the analysis to a smaller domain.Findings – The paper shows how to combine FEs and DD in an efficient way for material parameters tolerance analyses in microwave waveguide filters, showing speedup results.Research limitations/implications – The formulation here presented is 2D but can be easily extended to 3D.Originality/value – The application of DD to solve numerically large problem is well‐known, the idea and organization of the algorithm to allow iteration on parameter values on a single sub‐domain is here proposed.

An efficient finite elements electromagnetic analysis for geometries with small variations

In this work an innovative method for fast analysis of geometrical variations of electromagnetic field problems is proposed. The method is based on a geometrical perturbative approach for the solution of a linear differential operator in presence of small domain modifications. The perturbative theory is general, but in this contribution has been embedded in a classical finite element (FE) framework to achieve a very fast technique for the field evaluation in synthesis or tolerance investigation of electromagnetic problems.

Automated Waveguide Array - Integrated Design Environment (AWA-IDE): An Automated and Modular Tool for Planar [EM Programmer's Notebook] Waveguide Array Synthesis and Analysis

This article is focused on the development of an integrated framework for the synthesis and analysis of resonant waveguide planar arrays, aimed at improving every step of the design process of such devices. This tool has proven to be capable of dramatically speeding up the design and prototyping process: starting from geometrical and electrical specifications, the performance and layout of the designed structure can be quickly evaluated. Moreover, at the end of this process, a complete model is available for an electromagnetic final validation, and the mechanical construction process. The code takes advantage of different methods to face the different phases of the design process. An iterative simplex procedure is carried out for the aperture-synthesis step. An equivalent-magnetic-currents active-admittance-based waveguide model, for the internal problem, and an equivalent-magnetic-currents Method-of-Moments (MoM) model, for the exterior problem, are employed for the synthesis and analysis steps. The entire procedure is carried out through a custom user-friendly PyQt graphical interface environment. The code is entirely modular, and allows for reuse of legacy FORTRAN/C++ codes. New features, such as different solving methods or design procedures, can be easily added to the same tool chain. The proposed tool has been successfully employed in the design of some of the latest Selex-ES fl at-array radar antennas.

Patch arrays integrated with an EBG-surface

This paper presents results for an array of patch embedded in an EBG. The EBG surface is composed by short-circuited microstrips densely coupled each other through interlocked branch stubs. With respect to a conventional mushroom surface, this structure exhibits a better space-wave decoupling performance. The experimental results demonstrate decoupling till 38 dB in both planes for patches separated by only one half free-space wavelength.

A combined domain decomposition - model order reduction technique for fast finite element parametric sweeps

We have presented a combined DD-MOR method, which extends existing approaches by incorporating the DD in the generation process of the ROM. The DD method allows the efficient use of a multipoint MOR procedure, since only the subdomain containing parameter-dependent features has to be solved at the ROM interpolation points. In future work, we will extend our approach to frequency and geometry parameters, and demonstrate its efficiency in optimization scenarios.