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This paper presents the implementation of the Bayesian inversion method for the characterization and estimation of different dielectric material properties. The scattering parameters of single and multi-layer materials are measured using a free-space experimental setup using a standard gain horn antenna and a Vector Network Analyzer (VNA) at Ka-band (26–40 GHz). The relative permittivity, material thickness, and material positioning error are defined as model parameters and estimated using the observed (measured) data. The FR4 Epoxy, Rogers RT/Duriod 5880, and Rogers AD600 with different relative permittivities and thicknesses are used in the measurement setup. The results displayed good agreement between model parameters and estimated properties of the presented materials, while the corresponding eigenvectors provided a level of confidence in model parameter values. The results were compared with different reported techniques to showcase the possible use of the presented method in microwave imaging, non-destructive testing, and similar applications. [ABSTRACT FROM AUTHOR]

Transformation optics is a powerful tool allowing remapping a generic domain into another yet maintaining a correspondence of the solution of Maxwell's equations within the two domains. Transformation optics has been used in the past to conveniently solve for modes in a generic waveguide by transforming its cross‐section into a circular one. Such a transformation needs particular care in enforcing boundary conditions in the transformed, circular, domain. In this paper, a theoretical treatment of boundary conditions is presented, allowing for an accurate computation of all field components in a generic waveguide. [ABSTRACT FROM AUTHOR]

This article proposes a multibody electromagnetic (EM) model for the quantitative evaluation of the influence of multiple human bodies in the surroundings of a radio link. Modeling of human-induced fading is the key element for the development of real-time device-free (or passive) localization (DFL) and human presence-aware systems (HPS) based on the processing of the received signal strength (RSS) data recorded by radio frequency devices. The proposed physical–statistical model is able to relate the RSS measurements to the position, size, orientation, and random movements of people located in the link area. This novel EM model is thus instrumental for crowdsensing, occupancy estimation, and people counting applications for indoor and outdoor scenarios. This article presents the complete framework for the generic N-body scenario where the proposed EM model is based on the knife-edge approach that is generalized here for multiple targets. The EM-equivalent size of each target is then optimized to reproduce the body-induced alterations of the free-space radio propagation. The predicted results are then compared against the full EM simulations obtained with a commercially available simulator. Finally, experiments are carried out to confirm the validity of the proposed model using IEEE 802.15.4-compliant industrial radio devices. [ABSTRACT FROM AUTHOR]

A general design procedure for inline waveguide filters with frequency-variant couplings (FVCs) is presented. The goal of the design is the introduction of transmission zeros (TZs) in the filter response. The filter design starts with the synthesis of a low-pass prototype with FVC, adopting a method that recently appeared in the literature. The low-pass prototype is then denormalized to obtain an equivalent circuit of the filter suitable for waveguide implementation. The last step of the design consists of the dimensioning of the physical structure of the filter, including the frequency-dependent couplings, by exploiting the equivalence with the synthesized equivalent circuit. The design procedure can be applied independently on the specific structure implementing the FVCs. In the case of narrowband filters, the resulting structure may not require any further refinements by means of numerical optimization based on full-wave modeling. A design example illustrates the details of the procedure implementation. The validation of the procedure is presented through the design and fabrication of a substrate integrated waveguide (SIW) filter with two coincident TZs. [ABSTRACT FROM AUTHOR]

This study introduces the conic section arc elements in 2D and 2.5D finite element method (FEM). Elements are obtained by deforming an edge in a standard triangular element through a coordinate transformation. This allows to completely eliminate the geometrical error in structures composed of circular, elliptical, hyperbolic and parabolic arcs. The element order is defined independently of the geometrical description of the boundary, allowing the use of simple meshers. Previously available FEM codes can be straightforwardly modified to introduce the conic section boundaries. [ABSTRACT FROM AUTHOR]

This article presents an analytical method for the synthesis of a low-pass prototype filter constituted by cascaded ${n}$ -tuplets, including resonant node (RN) and nonresonant node (NRN). The method extends the features of previously published solutions, limited to RNs only or that allow the inclusion of NRNs but in rigid configurations. The method begins with extracted-pole synthesis, arbitrarily defining the transmission zeros (TZs). Then, a filter topology transformation is applied by grouped node blocks to obtain the desired topology, with each ${n}$ -tuplet characterized by the assigned TZs. The procedure overcomes the ad hoc techniques currently available in the literature. Moreover, the novel filter transformation presented here (from extracted-pole to cross-coupled topology) provides an additional degree of freedom for filter synthesis, which can be further exploited by filter designers. Several examples are presented to validate the novel synthesis procedure. [ABSTRACT FROM AUTHOR]

This article applies a new method to analyze modes in empty waveguides having perfectly conducting walls and a rather generic cross‐section. The method is based on a coordinate transformation that maps the generic profile of the waveguide cross‐section to a circular waveguide (CW) filled with an anisotropic material. Modes in this latter waveguide can be represented as a series over the corresponding free‐space CW modes. This representation is particularly useful if used as a modal expansion over the port of a 2.5D or 3D device treated with a transformation optics approach. The method is particularly efficient when the waveguide is "similar" to a CW. Applications are shown to the analysis of some waveguides of arbitrary cross‐section with a view on practical applications. [ABSTRACT FROM AUTHOR]

In this article, we introduce a synthesis-based design approach for waveguide filters, including singlets. As is known, a singlet block comprises one resonator coupled to source and load plus an additional coupling between source and load. In this way, a pole–zero pair is produced, thus allowing the introduction of a transmission zero in the frequency response. Structure making that uses cascaded singlets (especially implemented in waveguide technology) has been successfully used to realize compact and quasi-in-line pseudoelliptic filters. The design of this configuration suffers, however, from a severe drawback; while an isolated singlet can be exactly synthesized, when these blocks are put in cascade, nonresonating nodes (NRNs) are required to allow the cascade connection. Consequently, the resulting topology includes both cross couplings and NRNs, for which no exact synthesis solution is till now available (all the design solutions proposed in the literature are based on optimization). The new design procedure here proposed overcomes this drawback, allowing the synthesis of the equivalent circuit of the cascaded-singlet topology. Once this circuit is obtained, the dimensioning of the singlets can be carried out by exploiting a full-wave simulator according to the procedure described in the article. The proposed design approach allows a very accurate initial dimensioning of the filter, which represents an excellent starting point for final adjustments/optimizations. A detailed design example is presented in the article showing how to practically implement the novel procedure. This new approach is also experimentally validated by a waveguide filter prototype, previously designed by optimization and fabricated. It is shown how this filter can be redesigned with the novel procedure, obtaining very similar physical dimensions in a noticeably shorter time. [ABSTRACT FROM AUTHOR]

An elementary dipole in presence of a perfectly conducting wedge radiates a field whose analytic expression can be written in terms of a double infinite series. A dipole located at a point characterized by complex coordinates behaves in the real space as a directive source akin to a Gaussian beam in the paraxial region. In this article, the series solution, originally conceived for a dipole located at a point characterized by real coordinates, is extended to the case of a complex coordinates source, hence providing an analytical solution approximating the problem of a wedge illuminated by a Gaussian beam. [ABSTRACT FROM AUTHOR]

This article presents a novel method for the wideband analysis of lossless arbitrary multimode waveguide junctions. The analysis is based on a compact model obtained by the frequency response at the ports only. The model makes use of the generalized scattering matrix (GSM) and its frequency derivative and is capable to deal with a large number of modes (also below cutoff) with a small number of frequency samples. [ABSTRACT FROM AUTHOR]

In this paper, we propose the design of two perfect multilayered linear transpolarization structures working in transmission. These linear polarization converters are capable to rotate the polarization 90° independently from the direction of the input linear polarization. Results show an excellent conversion ratio. [ABSTRACT FROM AUTHOR]

The well‐known symmetry property of the scattering matrix relative to propagating modes becomes tricky in the case of arbitrary polarization or arbitrary complex modal functions, as in the case of waveguide polarizers and ortho‐mode transducers. A straightforward transformation between different modal bases for the guided waves leads to a loss of symmetry. Only by gaining a deeper insight on the properties of the scattering matrices and with separate transformations for the incident and reflected waves is symmetry recovered. [ABSTRACT FROM AUTHOR]

This paper describes a new method to analyze elliptical horns. The method is based on a coordinate transformation, which maps the elliptical shape to a circular shape, allowing to use the 2.5-D body-of-revolution finite-element method formulation with a greatly improved efficiency over 3-D methods. Applications are shown to the analysis and design of shaped arbitrary axial ratio horns. [ABSTRACT FROM AUTHOR]

The field generated by an elementary dipole in presence of a perfectly conducting wedge can be expressed analytically through a double infinite series. The series convergence gets critical when the observation point and the source are close to each other. In this letter, an improvement of that analytic solution, attained by extracting Green's function singularity, is presented, speeding up series convergence and allowing efficient computation of fringe currents, which are the corrective terms, taking into account diffraction, to physical optics current. [ABSTRACT FROM AUTHOR]

ABSTRACT This article presents a modular reciprocal multiplexer in which the number of channels can be reduced or expanded. The proposed configuration is based on reactive loads designed to substitute channel filters. This is at the same time easy to manufacture and easy to reconfigure as reactive loads are conceived, so as not to modify the characteristics of the active channels if a channel is added or removed. Additional filter tuning after a reconfiguration is not required. The proposed reciprocal design allows for both low costs and low losses since it does not require circulators or additional components, such as hybrid junctions, usually present in reconfigurable multiplexers, although maintaining a good degree of flexibility. A prototype of the proposed design has been fabricated and measured. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:538-546, 2016. [ABSTRACT FROM AUTHOR]

This paper describes the generalized 2.5-D finite-element method (FEM), a powerful method to analyze a class of waveguide components. The method is based on 2-D FEM in combination with a sinusoidal variation of the field in the third dimension. We discuss the application of the method to an $E$ -plane branched ortho-mode transducer, a septum polarizer, and a waffle-iron low-pass filter. [ABSTRACT FROM PUBLISHER]

The scattering problem of the electromagnetic field generated by an elementary dipole in the presence of a perfectly conducting wedge is here addressed in terms of a Sommerfeld integral which can be expressed by an infinite summation. The analytic solution presented is valid also in the case in which the dipole, the observation point, or both are close to the edge of the wedge. Approximations are also presented, and comparison with the uniform geometrical theory of diffraction (UTD) solution provided. [ABSTRACT FROM PUBLISHER]

In this paper, we first present a novel synthesis method based on an even- and odd-mode decomposition. This method is capable of synthesizing a network under very general hypotheses and is, therefore, suitable for lossy filter design. To exploit the increased flexibility of this new synthesis method over the traditional lossy design techniques, we then introduce a new approach to the design of lossy filters based on the characteristic polynomials evaluation. This new technique can offer many advantages over traditional techniques, and the main one is that, once the transmission function of the filter is known using traditional methods, the reflection function can be constrained with a certain degree of freedom. A tradeoff between additional constraints and redundancy in the final network must be accepted. Finally, we present design examples and a practical realization, which validate this novel approach to the design of lossy filters. [ABSTRACT FROM AUTHOR]

In this paper the electromagnetic coupling between a corrugated horn and a reflector dish is analyzed with a new hybrid perturbative technique. This coupling may produce significant modifications especially in the return loss and in the cross-polar pattern of the feed. The hybrid perturbative approach combines three different techniques: a mode matching (MM) technique for the propagation inside the horn, a method of moments (MoM) technique for the radiation of the horn taking into account the external part of the horn itself, and a fast Gaussian beam asymptotic physical optics (FGBAPO) technique for the interactions between the feed and the reflector. Some measurements and the comparison with rigorous numerical results demonstrate the accuracy of the new hybrid technique and the effects of this electromagnetic coupling on the feed performance. [ABSTRACT FROM AUTHOR]

Presents the multiport analysis of arbitrary circular-rod insets in rectangular waveguide by the generalized admittance matrix (GAM). Basis of an efficient computation of GAM; Efficiency by solving an uncoupled two-dimensional problems; Assessment by comparing results obtained.

Presents information on a study which analyzed electromagnetic inversion applied to pavement profiling by using monostatic ground penetrating radar. Equivalent model of a transfers electromagnetic horn antenna; Electromagnetic inversion; Experimental results; Conclusion.

A line integral perturbative analysis of deformed waveguides is discussed. As compared to available perturbative formulas, the line integral formula proposed has comparable accuracy and a much simpler implementation. [ABSTRACT FROM PUBLISHER]

The effect of undercutting on the electrical parameters of general single and coupled quasi-TEM lines in a multilayered dielectric is studied by an efficient quasistatic numerical method. Results are presented for characteristic impedance, propagation constant, and attenuation constant in single lines; two symmetrical coupled lines; and a four-line system. In all cases studied a significant increase of losses has been observed. [ABSTRACT FROM AUTHOR]

Describes a rigorous Green's function analysis of rectangular microstrip patch antennas enclosed in a rectangular cavity. Formulation of the rectangular microstrip antennas; Results of the experimental data; Conclusion of the study.

Studies the broad-band stripline circulators by means of a mixed numerical technique which employs both integral and segmentation methods. Method of characterization; Contour integral and segmentation methods; Implementation of the mixed method; Performance evaluation of tracking circulators; Conclusion of the study.