Search

An (N + 1 )-port junction endowed with complete rotational symmetry with respect to the first N ports is analyzed by a partial spectral decomposition of its S-matrix. This approach produces N/2 one-port boundary value problems, as well as a single two-port problem, which can be easily solved by means of standard full-wave simulators. The practical example of a coaxially fed 36-way power divider was easily analyzed by this method, and the results were nearly indistinguishable from those obtained by analyzing the device as a whole. Index Terms--Electromagnetic analysis, power combiners, power dividers.

This paper introduces a general method for the analysis of the individual blocks forming a complex circuit by measurements or simulations carried out on the whole. This is useful in those situations where the analysis of the single blocks is difficult. Paradoxically, the analysis of more complex structures, which contain individual elements, as subcircuits is, in some circumstances, easier to perform or may even be the only way to acquire information about the individual elements. Under certain conditions, the elements can be combined to obtain different circuits according to classic segmentation technique. Owing to its formulation, the method is applicable to both simulation and measurement problems. Index Terms--Calibration, circuit topology, electromagnetic analysis, electromagnetic measurements.

The filter prototype of side-coupled coaxial filters, which we recently proposed, has been modified to suit an arrangement in which the coupling apertures are placed on the side opposite the coaxial end gaps. In this situation, the modified prototype fits the physical counterpart better, resulting in a further design simplification. In addition, the feeds have also been modeled and included into the prototype, thus enhancing the correspondence between the prototype and physical structure. A practical design, concerning a WIMAX application, shows the reliability of this solution. Index Terms--Coaxial filters, prototype.

This paper presents a method for the design of compact diplexers, where the common junction is considered part of the filters, thus reducing the diplexer length by roughly one cavity. Starting from two filter prototypes satisfying the desired specifications, the technique provides the design equations in closed form. Effectiveness and accuracy of the proposed method are demonstrated by means of a practical example. Index Terms--Diplexer, filter, prototype.

A strategy for the full-wave analysis of slotted waveguide planar arrays is presented and demonstrated. The core of the method is a suitable segmentation of the antenna into two fundamental regions: an 'internal' one, formed by the waveguide circuit, and the 'external' one, consisting of the half space above the plate where the radiating slots are located. The internal region is further segmented into several blocks, connected to each other via their generalized admittance matrices (GAMs). The latter are calculated by means of either a commercial or a home made tool. The front plate is considered as a whole and analyzed by the moment method, in terms of modes of the slots. The latter are considered as short sections of waveguide whose length is just the conductor thickness, connecting the internal and external regions. The approach has been applied with success to a number of large planar arrays, both in rectangular and ridge waveguide. Index Terms--Generalized admittance matrix (GAM), generalized scattering matrix (GSM), method of moments (MoM), slotted waveguide 2-D arrays.

This paper presents a novel kind of circuit prototype suitable for modeling of coaxial cavity filters, where all cavities are coupled sidewise. Initially, the parameters of the prototype are explicitly derived from those of the classical Cohn's inline filter, which is assumed as the starting point. The main feature of the proposed adaptive model is its one-to-one correspondence to the physical structure, making design feasible without additional optimizations or expensive tuning. Another feature lies in that the prototype is adapted to the structure along the way in the synthesis process. A practical example shows the merits and the accuracy of the proposed prototype. The relationships between the proposed method and existing techniques are also discussed. Index Terms--Coaxial filters, prototype.

This paper addresses the problem of deriving an actual coupled-line model from the 'spot frequency' characteristics of transmission media derived by means of a numerical electromagnetic simulator. For a given set of coupled lines, possibly asymmetric and lossy, one of the main issues is to recover a model whose parameters are physically and practically meaningful. In order to satisfy the requirements, the model ought to basically yield a natural generalization of the well-known even/odd and c/[pi] modes for couples of lines, and collapse to a set of uncoupled lines when coupling is negligible. Hence, part of this study is devoted to discussing and evaluating models that satisfy such requirements. The end result is a Weissfloch-type equivalent circuit made up of uncoupled lines and input and output ideal transformers. The algorithm is then applied to the network parameters of coupled lines. The latter are evaluated by a full-wave method of moments approach, and a subsequent short-open calibration (SOC) procedure. Finally, a new algorithm is introduced that is able to evaluate and remove the contribution of the naked discontinuity due to ports, usually not directly available from the SOC routine. Index Terms--Calibration, coupled lines, method of moments (MoM).

The field nearby a thin iris discontinuity can be found in an exact manner by solving the wave equation in an appropriate coordinate system. To this end, it is necessary to select a coordinate system that fits the iris boundary. As an example, capacitive and inductive irises in rectangular waveguides have been solved by considering the Helmholtz equation in the elliptic-cylinder coordinate system. The presence of the wave-guide environment is then enforced either by using the aperture field solution in a variational expression of the equivalent shunt susceptance or by taking images. The advantage of the new solution is that a single term solution, apart from being very accurate and numerically efficient, also contains the correct frequency dependence; thus providing results over the entire band. Moreover, wide-band equivalent circuits with frequency independent elements of the Foster's canonical form descend directly from the field analysis.

This work addresses the problem of the fundamental limitations to the optimum performance of diplexers employing three-port junctions and preassigned branching filters. In this situation it is a common misconception that optimum results are achieved by utilizing a good power divider closed by two good branching filters. From the properties of the S-matrix of a three-port junction, we show this not to be the case and derive a set of necessary conditions to be satisfied in order that the junction be successfully employed in the realization of diplexers. We derive explicit expressions for the positions at which the filters must be placed in the junction arms for optimum diplexer performance, resulting in considerable simplification of the difficult diplexer synthesis problem. A theorem on the maximum achievable bandwidth is proved and validated by means of two practical examples.

Photolithographic techniques permit the realization of complex circuits totally confined to the E-plane of millimetric rectangular guides with high precision and low cost. This work contains a detailed analysis of an E-plane diplexer configuration recently introduced. Its main feature is the matching section of the three port junction, a simple abrupt E-plane one tuned by means of an inductive post realized on the same mask as the branching filters. On the basis of this analysis, we also demonstrate the application of a recently developed diplexer synthesis technique. Many prototypes, in [K.sub.a]-band were designed and tested, showing good performances and good agreement between theory and experiment.

Recent research on computer aided design (CAD) of rectangular waveguide elements is presented. It reports on a novel broadband equivalent circuit model of inductive posts in waveguide filters for precise CAD synthesis of such filters. The model, which was developed on a personal computer, considers only the post configuration and hasthe ability to characterize higher mode interactions also.