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Although at first sight Eastern Christianity is not associated with Africa, the African continent has shaped the establishment and development of three of the four main Eastern Christian traditions. Through a sociological lens, we examine the identity of the above African churches, focusing on the socio-historical entanglements of their religious and ethnic features. Firstly, we study the identity of the Coptic Orthodox Church, the Ethiopian Orthodox Church, and the Eritrean Orthodox Church belonging to Oriental Orthodoxy. We focus on these African churches—and their diasporas in Western countries—as indigenous Christian paths in Africa. Secondly, we examine the identity of Africans and African-Americans within Eastern Orthodoxy. We consider both to have some inculturation issues within the Patriarchate of Alexandria and the development of an African-American component within Orthodoxy in the USA. Thirdly, we analyze the recent establishment and identity formation of African churches belonging to Eastern-rite Catholic Churches. In short, we aim to elaborate an overview of the multiple identities of African churches and one ecclesial community in Eastern Christianity, and to compare diverse sociological entanglements between religious and ethnic traits within them. A fruitful but neglected research subject, these churches' identities appear to be reciprocally shaped by their own Eastern Christian tradition and ethnic heritage. [ABSTRACT FROM AUTHOR]

The objective of this article is to describe the design of a new family of wideband filters in a rectangular waveguide based on hybrid couplings and a staircase configuration. The use of E-plane T-junctions and E-plane folded structures is also discussed, in order to enhance the out-of-band response and the selectivity of the filter with respect to the current state of the art. The design of several hybrid filter prototypes is discussed in detail, including manufacturing sensitivity and high-power analysis. Finally, simulations and measurements for an eight-pole filter prototype are also compared, showing very good agreement, thereby fully validating both the design procedure and the new filter topology that we propose. [ABSTRACT FROM AUTHOR]

In this article, we present a novel bandpass filter based on dual-mode resonators. The dual-mode operation is based on integrated coaxial and rectangular waveguide cavities. Furthermore, we also discuss a systematic design procedure for the selection of the dimensions of the various constituent elements of the filter, which is based on the well-known aggressive space mapping technique. The design of a five-pole bandpass filter operating in the X-band is discussed in detail, including the measured data. The comparison between simulations and measurement shows very good agreement, thereby fully validating both the new filter structure and the design procedure. [ABSTRACT FROM AUTHOR]

The article offers a first exploration of the recent religious phenomenon of conversions to Orthodox Christianity in Western Europe. According to latest sociological studies, it examines this novel trend focusing on the main patterns of religious change in Europe. Although for centuries Orthodox Christianity has been present in several Western European countries, only in the last two decades it developed encounters with host societies and conversions among natives. Starting from the leading case of Orthodox diasporas in Italy, some facets of this European Orthodox conversion' trend are examined. In particular, through references to Orthodox conversions' case in United States, and global processes that are re-shaping (Western European) religious landscapes. [ABSTRACT FROM AUTHOR]

This article explores the landscape of Christian immigration in Veneto, and outlines a picture of the Christian churches and parishes of immigrants in the region. It focuses also on the effects of immigration within the Catholic Church, analyzing recent developments in the Pastoral Centers for immigrants. The data comes from an ongoing research concerning the process of pluralization and differentiation of Christian religion in Veneto. The descriptive and exploratory aims of this work reflect the initial state of the project. The results suggest that in parallel to the Catholic hegemony – which historically characterizes our region – there is a quantitative expansion of the other two branches of Christianity. This growth appears to be favored by migratory flows to Veneto which are changing the balance of ethnic communities inside the Catholic church. [ABSTRACT FROM AUTHOR]

A technique is described to measure the generalized scattering matrix (GSM) of a waveguide device whose ports are multimodal. The device-under-test is placed in between suitable converters, thereby transforming multimodal ports into monomodal ports. The needed data are then measured using a standard vector network analyzer. A dedicated algorithm is finally used to recover the multimode GSM of the device. The experimental validation is reported in this paper for rectangular and square waveguides showing excellent agreement between theory and measured results. [ABSTRACT FROM PUBLISHER]

Satellite communications are used intensively today. Separating the different frequency channels requires high selectivity. Up to now, this high selectivity has been achieved by using circular filters placed in circular waveguides. However, circular waveguides require a complicated design process and are difficult to manufacture. In this article, a filtering method based on rectangular geometry and using the higher mode is presented. The synthesis procedure and its practical equivalent circuit are shown to create independent zeros to the right and/or left of the passband. To validate this new concept of filtering and the corresponding synthesis, applications on TE10/TE30 in-line rectangular filters are presented. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005. [ABSTRACT FROM AUTHOR]

Focuses on dual-mode filters using simple inductive discontinuities in a rectangular waveguide environment as basis. Employment of multimode equivalent network representations to analyze filters; Presentation of measure performance of several filter structures; Query on the efficiency of the model.

Examines a full-wave computer-aided design (CAD) of a microwave filter with integrated coaxial excitation. Uses of coaxial waveguide in microwave subsystems; Elements required in the implementation of a CAD tool; Composition of the filter structure.

Deals with a study that presented an alternative approach for the design of open-ended waveguide array antennas. Details on the basic admittance formulation; Improving computational efficiency; `Filter' design of waveguide phased-array antennas; Conclusions.

Describes two multimode network representations for the analysis of radiating array of thick parallel plates. Integral equation approach; Direct calculation of the element of the coupling matrix; Numerical validation of the study; Conclusion.

Looks at a study which focuses on the analysis of waveguides of different cross sections, with the multimode network representation (MMNR) approach. Indepth look at the modal analysis; Detailed information on the coupling coefficients; Further detailed information on the study.

Analyzes the full wave network representation for rectangular, circular and elliptical to elliptical waveguide junctions. Convergency of the propagation constant; Elements of the matrices; Comparison between simulation and measurements for an elliptical iris in a circular waveguide.

Examines the utilization of the components in uniform bends in rectangular waveguide in microwave subsystems for ground and space application, while looking at their performance. Transition from straight to curve waveguide; Relation between simulation, theoretical and experimental data; Transformation of Helmholtz equation by Galerkin method; Contributions of Rice, Cochran, Bates, Lewin Carle, Accatino and Weisshaar.

Since the 1990s, there has been conflictual interactions between Orthodox Christian churches and human rights in South Eastern Europe, especially during the process of European integration. In this work, I shall concentrate on the case of the Romanian Orthodox Church and explore its current position towards human rights that has developed within the context of EU membership. Focusing on the influence that European integration has had on the Romanian Orthodox Church, I hypothesise a re-orientation of the latter from a position of closure and a general rejection of human rights in the direction of their partial acceptance, with this being related to its attempt to develop a European identity. [ABSTRACT FROM AUTHOR]

This article analyses the topic of Globalization and Orthodox Christianity. Starting with Victor Roudometof’s work (2014b) dedicated to this subject, the author’s views are compared with some of the main research of social scientists on the subject of sociological theory and Eastern Orthodoxy. The article essentially has a twofold aim. Our intention will be to explore this new area of research and to examine its value in the study of this religion and, secondly, to further investigate the theory of religious glocalization and to advocate the fertility of Roudometof’s model of four glocalizations in current social scientific debate on Orthodox Christianity. [ABSTRACT FROM AUTHOR]

In this article, we describe a new family of multiband waveguide filters based on a folded topology. The folded topology allows to use the filters of different orders and the introduction of transmission zeros. The design of the multiband filter is based on the aggressive space mapping (ASM) technique and is able to take into account manufacturing details, such as round corners and tuning elements. The filter structure is validated by designing, manufacturing, and measuring a triband filter. The agreement between simulations and measurements is shown to be excellent, thereby fully validating both the filter topology and the design process. [ABSTRACT FROM AUTHOR]

This article describes the design procedure of a compact wideband waveguide filter, based on stepped impedance resonators (SIRs) and a combined usage of capacitive and inductive coupling irises, that provides a significant improvement in the out-of-band response of the filter with respect to the state-of-the-art. In addition to theory, several filter prototypes have been designed and manufactured. A detailed sensitivity analysis has also been carried out. Finally, simulations and measurements are compared, showing very good agreement, thereby fully validating the new filter topology. [ABSTRACT FROM AUTHOR]

The objective of this article is to describe a new family of microwave bandpass filters in the rectangular waveguide based on resonant apertures, which can be used to implement both single- and dual-band transfer functions. The use of capacitive stubs and a staircase configuration is also discussed in order to enhance the out-of-band response and the selectivity of the filter with respect to the state of the art. Finally, simulations are compared with measured results, showing very good agreement, thereby fully validating both the new filter topologies and the design procedure. [ABSTRACT FROM AUTHOR]

An alternative configuration for an infinite coaxially end-fed waveguide phased-array antenna is explored. In the proposed configuration, the integration of the end-fed launcher and the output waveguide, rather than the waveguide in itself, acts as a basic radiator. This allows the design of more compact antenna elements. In order to analyze and optimize the structure, an accurate full-wave simulation tool based on the multimode admittance matrix representation is developed. Results are validated against state-of-the-art commercial CAD software. Numerical simulations involving singly and doubly tuned configurations are presented and discussed to illustrate the potential convenience of the proposed configuration and of the CAD tool developed. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 276–281, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10437 [ABSTRACT FROM AUTHOR]

This paper describes a number of broadside-coupled microstrip structures and their use for the implementation of high-selectivity multilayered filters. The broadside configuration allows for the introduction of cross couplings between nonadjacent resonators. The cross couplings can then be used to implement transmission zeros that can significantly increase the selectivity of the filters. Furthermore, the investigation shows that the amount of coupling can be considerably increased if the resonators are broadside coupled, thus easily allowing the implementation of broadband filters. Measured results are shown to agree with predictions, thereby fully validating the new structures described. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 295–302, 2001. [ABSTRACT FROM AUTHOR]

In this article, we describe several alternative inline implementations for combline filters with transmission zeros (TZs) located both below and above the passband. A systematic design procedure is also presented using a lumped-element equivalent circuit. Following the design procedure that we propose, up to $N+1$ TZs can be implemented with an inline filter of order $N$. The generation of the TZs is explained physically in terms of mixed inductive and capacitive couplings. Several filters are also manufactured and tested. Good agreement between the measured and simulated results is demonstrated, thereby fully validating the new filter concepts. [ABSTRACT FROM AUTHOR]

In this article, we show how the multimode equivalent network (MEN) technique can be extended to the analysis of multilayer boxed planar microwave circuits that are built using a thick metallization. This analysis is carried out considering the thick metallic circuit as a length of the uniform waveguide. The problem is then divided into two waveguide steps (or junctions). We first obtain the equivalent network of the two junctions. Then, we cascade them to obtain the MEN of the complete circuit, thereby including the effect of finite thickness rigorously. A key aspect of the formulation that we propose is that it includes ports in the transverse plane of the circuit. In addition to theory, several shielded microwave filters using a thick metallization are also analyzed. An in-depth study of the numerical convergence is also performed for two practical examples. Simulation results are shown to be in good agreement with both commercial simulation tools and measurements, thereby fully validating our theoretical formulation. [ABSTRACT FROM AUTHOR]

The multimode equivalent network (MEN) formulation has been originally developed for the efficient and accurate analysis of waveguide devices. In this article, we extend the use of the MEN to the analysis of zero-thickness, planar printed circuits in a metallic enclosure. The formulation is developed for metallic areas of arbitrary shape and includes both internal and external ports in the transverse plane to model connections to external components, and coaxial input/output ports. The boundary integral resonant mode expansion (BI-RME) method is used for the analysis of the arbitrary shape metallizations. On this basis, shielded multilayered microstrip circuits of complex geometry are analyzed in the common frame of the MEN technique. To validate the theoretical formulation, several boxed microstrip structures are analyzed, including multilayered configurations with several metallization interfaces, showing good agreement with respect to both other commercial tools, and measurements. [ABSTRACT FROM AUTHOR]

Space mapping (SM) and aggressive SM (ASM) techniques are widely used in the synthesis and design of microwave filters. Their popularity stems from the inherent simplicity of the procedures and from their effectiveness. The objective of this article is to extend the state of the art of these techniques by discussing how they can also be used very effectively to tune microwave filters. In addition to the theory, the successful tuning of a six-pole inductive waveguide filter is discussed in detail, thereby fully validating the proposed SM techniques. [ABSTRACT FROM AUTHOR]

This paper describes a new family of all-metallic radiators based on below-cutoff apertures fed by evanescent-mode ridge-waveguide filters. The passband of the filters and the polarization of the apertures are configured to radiate orthogonal signals at a different center frequencies. The simultaneous operation of these radiators in an array configuration results in interleaved apertures producing overlapped fields. This strategy reduces the volume and weight of the antenna system, which is an especially appealing characteristic in satellite antennas. Each isolated evanescent-mode filter ends in a small-size aperture and is designed following a novel synthesis procedure. Next, the radiating elements are combined, and the resulting array is analyzed as a multiplexer from the input ports to the free-space region, thus accounting for all mutual couplings between different apertures. To validate the theoretical formulations, a prototype has also been manufactured. The results obtained show very good agreement between simulation and measurements in terms of reflection coefficient, sidelobe level, and realized gain, thereby fully validating the new family of radiating arrays. [ABSTRACT FROM AUTHOR]

Low-loss performance is one of the main drivers in the design of microwave filters and diplexers. In this paper, we propose a simple, low-cost solution to this problem. Measured responses of specific designs are also included, indicating that the solution proposed is indeed practical and cost effective. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 27: 7–9, 2000. [ABSTRACT FROM AUTHOR]

This paper reports on the experimental measurement of power threshold levels for the multipactor effect between samples of ferrite material typically used in the practical implementation of L- and S-band circulators and isolators. For this purposes, a new family of wideband, nonreciprocal rectangular waveguide structures loaded with ferrites has been designed with a full-wave electromagnetic simulation tool. The design also includes the required magnetostatic field biasing circuits. The multipactor breakdown power levels have also been predicted with an accurate electron tracking code using measured values for the secondary electron yield (SEY) coefficient. The measured results agree well with simulations, thereby fully validating the experimental campaign. [ABSTRACT FROM AUTHOR]

The objective of this paper is to advance the state of the art of aggressive space mapping (ASM) by demonstrating how, for resonant structures, and microwave filters in particular, an ASM-based optimization procedure may converge to the desired target performance in just one step. This behavior is first justified in physical terms, using the electromagnetic cavity perturbation theory, and is then investigated numerically. Several practical filter design demonstrations are also presented. This paper is concluded with a conceptual definition of Space Alignment in the context of ASM. [ABSTRACT FROM AUTHOR]

Summary: This paper presents a technique for the efficient design of bandpass waveguide microwave filters using a segmentation technique applied to an equivalent circuit. The technique is based on first developing an equivalent circuit that synthesizes the desired transfer function. Then, the different parts of the real physical structure are optimized by segmenting this equivalent circuit. The technique was originally developed for in‐line filters, and the main contribution of this paper is in the combination of this technique with the coupling matrix formalism. In this way, we adapt for the first time this design strategy to the design of complex coupling topologies, beyond the in‐line configuration. As an example, a complex sixth‐order dual‐mode filter, implemented in all‐inductive waveguide technology, is designed using the new coupling matrix segmentation technique, showing the effectiveness of the presented theory. A prototype of the filter has been manufactured, and the accuracy of the design technique is verified by measurements on the real prototype. [ABSTRACT FROM AUTHOR]

Numerical methods are widely used to analyze and design microwave components for communication applications. In the implementation of any numerical technique, however, there are always a set of parameters that must be properly adjusted in order to obtain, at the same time, computational efficiency and numerical accuracy of the results. In this context, therefore, we focus in this paper on the multimode equivalent network formulation for waveguide devices, and we propose a more intuitive and efficient strategy for choosing these parameters. Following our approach, setting only one global numerical variable is sufficient to adjust automatically the specific convergence parameters of each discontinuity to give a specific level of numerical accuracy of the results. As a consequence, the computational efficiency is significantly increased. In addition, the user experience is significantly improved since our approach eliminates all lengthy convergence tests previously needed to assure good numerical accuracy. In addition to theory, we discuss in this paper a number of numerical results that clearly demonstrate how the new strategy is very effective, thereby fully validating the theoretical formulation. [ABSTRACT FROM PUBLISHER]

This paper provides the guidelines for the practical development of novel advanced test beds for passive intermodulation (PIM) measurements. The proposed test beds show high performance and are flexible, allowing for the measurement of several PIM signals of different orders, with two or more input carriers. In contrast to classic test beds for satellite hardware, based on the cascaded connection of several elements, an integrated solution involving the minimum number of hardware pieces is proposed. The result is a lower number of flanged interconnections, thus reducing residual PIM level and insertion losses. In addition, return loss degradation and harmful spurious generation in the interconnections are also avoided. Measurement test beds for conducted and radiated PIM, in both transmitted and reflected directions, are discussed, highlighting the benefits and drawbacks of each configuration. Design guidelines for the key components are fully discussed. Illustrative application examples are also reported. Finally, excellent experimental results obtained from low-PIM measurement setups, working from C-band to Ka-band, are shown, thus fully confirming the validity of the proposed configurations. [ABSTRACT FROM PUBLISHER]

The objective of this paper is to use electromagnetic-based computer-aided design (CAD) tools to investigate the maximum tuning range of channel filters, typically used in satellite payloads. Both circular and rectangular waveguide technologies are investigated. The results of the investigation show that single-mode rectangular waveguide implementations offer substantially wider tuning range, as opposed to classical dual-mode circular waveguide implementations. In addition to simulations, measurements are also presented indicating very good agreement with theory, thereby fully validating the CAD procedure. [ABSTRACT FROM PUBLISHER]

In this paper, two novel compact diplexers for satellite applications are presented. The first covers the Ku-band with two closely spaced channels (Ku-transmission band: 10.7–13 GHz and Ku-reception band: 13.75–14.8 GHz). The second is wider than the first (overall bandwidth up to 50%) achieves the suppression of the higher order modes, and covers the Ku/K-band with a reception channel between 17.2 and 18.5 GHz. Both diplexers are composed of two novel bandpass filters, joined together with an E-plane T-junction. The bandpass filters are designed by combining a low-pass filtering function (based on $\lambda $ /4-step-shaped band-stop elements separated by very short waveguide sections) and a high-pass filtering structure (based on the waveguide propagation cutoff effect). The novel diplexers show a very compact footprint and very relaxed fabrication tolerances, and are especially attractive for wideband applications. A prototype Ku/K-band diplexer has also been fabricated by milling. Measurements show a very good agreement with simulations, thereby demonstrating the validity and manufacturing robustness of the proposed topology. [ABSTRACT FROM PUBLISHER]

This communication describes a multimode equivalent network (MEN) representation of a finite array of open-ended lossless waveguides on an infinite ground plane. The derivation is based on an integral equation formulated at the interface between the waveguides and the free-space region. The MEN is formulated using the concept of accessible and localized modes, and includes ports for the free-space plane waves. The MEN derived can be easily combined with the MENs of other microwave components, thus allowing for the accurate analysis and design of more complex systems composed of waveguide elements and radiating apertures. Both simulated and experimental results are presented showing a very good agreement, thereby fully validating the proposed equivalent network representation. [ABSTRACT FROM AUTHOR]

The design and physical implementation of hybrid folded rectangular waveguide filters providing multiple transmission zeros (TZs) below the passband are considered in this paper. These structures offer great flexibility to locate the TZs in a wide frequency range. Different implementations have been considered, each one offering certain advantages in terms of ease of manufacture, number of TZs, and their separation from the passband. A simple design procedure is also described. Measurements of a manufactured five-pole filter prototype and simulations fully validate the novel configurations proposed in this study. [ABSTRACT FROM PUBLISHER]

The design of manifold-coupled multiplexers for wideband applications is considered in this paper. A systematic procedure, based on the sequential connection of filters to the manifold and subsequent adjustment of the interconnection elements, is presented. The filters are attached to the manifold without using stubs in order to minimize the effect of spurious resonances. The interconnection elements, the manifold, and the remaining filters are considered as the first inverter of each new filter that is attached. This technique has been applied to several practical examples. The obtained results validate the proposed design methodology. [ABSTRACT FROM PUBLISHER]

In this paper, a new systematic technique to design manifold-coupled multiplexers in waveguide technology is proposed. The new technique uses generalized low-order electromagnetic (EM) distributed models, which constitute a half-way point between the fast, but imprecise, analytical models, and the more accurate, but costly, full-wave EM models. The method can be applied to contiguous and noncontiguous channel multiplexers, in both E-plane or H-plane configurations. This paper covers the complete design procedure for manifold multiplexers, starting from the required specifications and finishing with the physical dimensions. After explaining the general design technique for multiplexers with channel filters based on transmission-line resonators, the method is specialized for the design of classic multiplexers with circular-waveguide dual-mode filters. As a further application example, the same methodology is also used for the design of a nonconventional tuningless wideband multiplexer with a new type of rectangular waveguide filters. This paper is concluded with a comparison between simulation and measurements for the wideband multiplexer. Excellent agreement between measurements and simulations are demonstrated, thereby validating the complete design procedure. [ABSTRACT FROM AUTHOR]

In this paper, we propose a systematic procedure for the accurate design of classical dual-mode filters in circular waveguide technology. The design procedure is based on the previous synthesis of an intermediate distributed model, which links the standard lumped (or coupling matrix) elements circuit with the practical waveguide realization. We then show how the equivalent distributed model can be directly used to obtain the physical dimensions of these filter components (typically rectangular and cross-shaped irises, as well as tuning and coupling screws). The value of this paper lies in the fact that the proposed design strategy provides the final dimensions of these complex structures with unprecedented levels of accuracy and numerical efficiency, as it is shown through two dual-mode filter designs for narrowband applications, and measurements of a manufactured prototype. [ABSTRACT FROM PUBLISHER]

In this paper, the design of a novel planar narrowband microstrip filter is presented. The structure is designed and manufactured in microstrip technology, and it is formed by set of pairs of resonators of different lengths. The length of one resonator in each pair is adjusted so that a suitable odd resonance is tuned to the center frequency of the filter. The length of the other resonator is adjusted so that the next even resonance is tuned again to the center frequency of the filter. The different path of the signal in each resonator produces a cancellation of energy at a given frequency, therefore implementing a transmission zero in the insertion-loss response of the filter. First, this paper presents a design example of a single set of resonators (basic unit cell) working at the fifth and sixth resonances. Then, two basic unit cells working at the first and second resonances are first optimized, and then they are cascaded to show how higher-order filter responses can be implemented. The measured results confirm the theoretical predictions, and validate the new structures for high-selectivity applications. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 450–455, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20499 [ABSTRACT FROM AUTHOR]

Reports on a time-domain analog in microwave lines to the spatial Fraunhofer (far-field) diffraction in paraxial conditions. Use of microstrip lines to design filtering configurations acting as spectrum analyzers; Maximum frequency resolution achievable under the situation.

Examines the shielded multilayered printed circuits composed of arbitrarily shaped metallic areas using the method of moments/boundary integral-resonant-mode expansion method. Basis of the analysis; Approach in obtaining the integral equation; Feasibility of the method.

Focuses on a parallel-coupled-line microstrip bandpass filter with suppressed spurious passband. Design of the filter; Modulation of wave impedance; Different values of the perturbation amplitude; Effective rejection of the harmonic passband.

In this contribution, we describe the design of bandpass filters using evanescent mode waveguides and dielectric resonators implemented with additive manufacturing techniques. Two C-band Chebyshev evanescent mode waveguide filters of order five have been designed using a low cost commercial dielectric material (ABSplus), widely used by Fused Deposition Modeling (FDM) 3D printers. The housings of the filters have been manufactured using traditional computer numerical control (CNC) machining techniques. Practical manufacturing considerations are also discussed, including the integration of dielectric and metallic parts. We first discuss two breadboards using two different resonator geometries. We then demonstrate how different transfer functions can be easily implemented by changing the 3D printed parts in the same metallic housing. Breadboards show fractional bandwidths between 3% and 4.6% with return losses better than RL = 18 dB, and spurious free ranges of SFR = 1 GHz. Insertion losses are better than IL = 4.3 dB. Even though dielectric losses from the plastic material are shown to be high, the measured results are quite satisfactory, thereby clearly showing that this strategy maybe useful for the fast production of low cost microwave filters implementing complex geometries. [ABSTRACT FROM AUTHOR]

In this work, we propose an integral equation technique for the efficient analysis of capacitive step discontinuities in rectangular waveguides. The method allows for the inclusion of a number of arbitrarily shaped posts in the vicinity of the step discontinuity. The posts can be both metallic or composed of homogeneous dielectric materials. The integral equation formulation is based on the Surface Equivalence Principle, and uses the parallel plate Green's functions that take into account for the boundary conditions imposed by the host waveguide. The formulation is written in the mixed spatial-spectral frequency domain, and takes advantage of the symmetry of the problem by reducing the original three dimensional (3D) problem to a so called 2.5D problem. The numerical technique has been validated with simulation examples, namely, two lowpass filters that use conducting and dielectric posts of different shapes as impedance inverters. The results provided by the method that we propose have been also compared to those obtained with a commercial full-wave software tool (ANSYS HFSS), showing in all cases a very good agreement with substantially higher computational efficiency. [ABSTRACT FROM AUTHOR]