Field theoretical treatment of E-plane waveguide junctionswith anisotropic medium

E-plane waveguide junctions containing an anisotropic medium are analyzed. The analysis is based on the equivalence principle and on cavity field expansions. Using the equivalence principle, magnetic surface currents are introduced at the imaginary boundaries chosen between the central region of the junction and the waveguides. The electric displacement D in the junction is expressed in terms of a solenoidal set and an irrotational set. Matching the tangential magnetic field at the imaginary boundaries leads to a matrix equation, the unknown of which are the amplitudes of the scattered waveguide modes. Using this method, the performance of E-plane waveguide junctions with full-height and partial-height ferrite post is analyzed. The influence of the completeness terms G_oq on the numerical results of an empty E-plane Y-junction is shown. The numerical results are compared with previously published experimental and theoretical results     

Field theoretical CAD of open or aperture matched T-junctioncoupled rectangular waveguide structures

The rigorous computer-aided design of rectangular waveguide structures coupled by open or rectangular iris loaded E- or H-plane T-junctions is described. The design theory is based on the full wave mode-matching method for the key-building-block T-junction element associated with the generalized S-matrix technique for composite structures. The waveguide structures may be arbitrarily composed of the T-junction and already known key-building-block elements (such as the double step and the septum discontinuity) combined with homogeneous waveguide sections between them. The E- or H-plane T-junction effect, large apertures, finite iris or septum thicknesses, and higher-order mode interactions at all step discontinuities are rigorously taken into account. Typical design examples, like rectangular iris coupled T-junctions, narrow-stopband waveguide filters, high return loss E-plane T-junction diplexers, an elliptic function E-plane integrated metal insert filter and a simple ortho-mode transducer demonstrate the efficiency of the method. The theory is verified by measurements     

Mutual coupling in a slotted phased array, infinite inE-plane and finite in H-plane

The mutual admittance matrix is computed for a planar phased array of thin slots with assumed single-mode cosinusoidal aperture electric field. The array is of infinite extent in the E-plane and of finite extent in the H-plane. The H-plane excitation is arbitrary and the array is phase scanned in the E-plane. Resultant active row-port admittances and H-plane aperture distribution are in agreement with large strictly finite array calculations and with a Floquet mode infinite array model, for the example case of uniform H-plane excitation     

Numerical analysis of waveguide discontinuity problems using thenetwork model decomposition method

The use of the network model decomposition method for analyzing arbitrarily shaped H- and E-plane waveguide junctions is discussed. By using the polygon discretization technique previously introduced by the author (1990), the waveguide discontinuity region, which is surrounded by a metallic wall and the reference planes chosen, is first discretized; the topological model and the corresponding network model for the waveguide discontinuity are then established. In the formulation, equivalent current sources connected to the nodes on the boundary of the region are introduced to replace the effect of the field external to the region. The field internal to the region is approximated by the nodal voltage distribution of the network model, which can then be used to determine the scattering parameters of the waveguide junction. A diakoptic algorithm for the solution of the network model is also developed. Numerical results for various H- and E-plane junctions are given, and it is shown that the method compares favorably compares with other theories     

Mode charts for magnetized ferrite cylinders

Waveguide junction circulators using the E- and H-plane technique usually employ height-dependence ferrite modes. The most crucial parameter is the frequency splitting between two angle-dependent modes. It rises with the magnetic bias field until there is a maximum at about saturation. Mode charts are given to help the designer look up the resonance frequencies of the most important modes as a function of the external, measurable field. The unsaturated state of the ferrite material is also covered. These diagrams are in good accordance with experimental experience and have been helpful in interpreting circulator performance, especially for the identification of spurious resonances     

Numerical analysis of H-plane waveguide junctions bycombination of finite and boundary elements

A numerical method is formulated for the analysis of H-plane waveguide junctions with arbitrary cross sections. The junctions are loaded with arbitrarily shaped dielectric or ferrite. The method is a combination of the finite-element method and the boundary-element method, and is applied to the regions with and without dielectric or ferrite, respectively. To show the validity and usefulness of the method, a lossy dielectric post and a ferrite slab in a rectangular waveguide are investigated in detail, and the computed results are compared with earlier theoretical and experimental results     

Analysis of E-H plane tee junction using avariational formulation

A three-port equivalent network for an E-H plane tee junction is determined taking into account the effect of waveguide wall thickness and considering the contribution of the dominant mode to the imaginary part of the self-reaction. The parameters of the three-port equivalent network are determined. From a knowledge of the equivalent network parameters, the net impedance loading, reflection coefficient, and coupling are evaluated for an E-H plane tee junction. A comparison between theoretical and experimental results is also presented     

A new six-port microwave network; six-port magic junction

A six-port junction is proposed that consists of an H-plane symmetrical waveguide Y-junction with a coaxial line on one side of its axis and a circular waveguide on its other. The scattering matrix of the junction in an ideal case is derived using the symmetry properties of the structure. If both the coaxial and the circular waveguide arm are matched without destroying the symmetry, the arms of the junction are automatically matched and isolated as well, similar to the side arms of a conventional magic T. Therefore, the proposed device is called a six-port magic junction. These properties are confirmed experimentally in X-band. Some interesting applications based on the properties of the six-port junction are discussed     

A rigorous variational formulation of an H planeslot-coupled tee junction

A rigorous analysis for the determination of an exact equivalent network for the slot-coupled H-plane tee junction that takes the effect of wall thickness into account is presented. A variational formulation is used for the determination of the parameters of the network. The parameters of the S-matrix as well as coupling are evaluated from the exact equivalent network. Comparisons between theoretical and experimental results are presented     

Parameter de-embedding accuracy dependency upon material sampledimensions

The sensitivity of the sample fit in rectangular waveguide fixtures is examined for constitutive parameter de-embedding. The sensitivity is characterized through a percent error figure between the de-embedded and known parameter values when an air gap exists between the sample and the side walls of the fixture. The de-embedding process assumed a completely filled waveguide in which rigorously calculated S parameters for material sample air gaps in either the E- or H-plane walls of the waveguide were used. The presence of an air gap was very noticeable for a E-plane gap. Commonly used gap correction factors provided limited improvement in reducing air gap related errors     

Performance of probe-fed microstrip-patch element phased arrays

The performance trends for large phased arrays with probe-fed microstrip-patch elements are discussed, with primary consideration given to single-probe (unbalanced) feed for rectangular grid arrays with rectangular patch geometry. The effects of substrate thickness and permittivity, patch dimensions, and element spacing are examined. Pronounced surface- and leaky-wave effects that tend to limit the scan volume are found. Interaction between the patch resonance at broadside scan and the leaky-wave resonances leads to an E-plane scan-bandwidth tradeoff. In the H-plane scan a transverse electric (TE)-type guided wave resonance is found that becomes pronounced when the H-plane dimension is a large fraction of the H-plane element spacing. This leads to a limitation of the H-plane patch dimension in the rectangular grid arrays. An element design procedure is proposed and illustrated for an element suitable for wide-angle scan over a ±5% frequency band     

A complete E-plane analysis of waveguide junctions usingthe finite element method

A complete finite-element analysis of inhomogeneous E-plane waveguide junctions is presented. It is shown that at least two field components are needed for the analysis. This method solves for the three components of the magnetic field in two dimensions and calculates the scattering parameters of the junction. Precalculated matrices are used for fast matrix assembly. Results for a metallic post agree very well with earlier published values. A dielectric post was also analyzed     

Effects of metal fences on the scan performance of an infinitedipole array

A theoretical method is presented to investigate the scan characteristics of a dipole array in the presence of thin metal fences along the H-plane. The basic idea of the analysis is to determine the current distribution on the dipole which interacts with the metal fence in the unit cell, so that the active impedance of the element can be computed. This was accomplished by using the moment method and imposing the boundary conditions on the tangential electric fields along the dipole and the metal fence. Since the scan performance in the H-plane is not affected by the fences, the discussion is concentrated on the E-plane behavior. It was found that for a given element spacing and dipole geometry there is an optimum fence height at which the E-plane performance can be most improved. For a typical dipole array geometry the optimum fence height is about 0.4 λ. It was thought that when the fences are to high and the beam is scanned too far from broadside, transverse magnetic (TM) surface waves propagating in the E-plane direction near the corrugated plane would be excited. However, no such sensitive cases were encountered in the study     

Optimum field theory design of broad-band E-plane branchguide phase shifters and 180° couplers

Optimum rectangular waveguide E-plane branch guide phase shifters and 180° branch guide couplers are designed with the rigorous method of field expansion into normalized eigenmodes. The design includes both the higher order mode interaction between the step discontinuities and the finite step and branch heights. The phase shifter design applies the Schiffman principle to branch guide couplers where two ports are short-circuited. The 180° coupler design combines the advantage of the broadband potential of multiple-branch couplers with the low-insertion-loss qualities of E-plane stub-loaded phase shifters. A computer-optimized phase shifter prototype for the waveguide Ku-band (12-18 GHz) shows a 90°±1° differential phase shift with reference to an empty waveguide within about 23% bandwidth. Five-branch three-stub coupler prototypes, designed for 3±0.2 dB coupling, for the waveguide Ku- and Ka-bands (26-40 GHz) achieve a 180°±1° differential phase shift at the output ports within about 19% bandwidth, as well as more than 30 dB isolation and return loss. The theory is verified by measured results     

Antenna designer's notebook-approximate location of scan-blindnessangle in printed phased arrays

An approximate equation for the computation of scan blindness in the E-plane of a printed phased array is given. The scan blindness occurs before the onset of the grating lobe, requiring the recalculation of the element spacing to keep the scan blindness out of the required scanned area. As an example, the case of an infinite array of printed radiators designed for a maximum scan angle of 30° in the E-plane and a maximum scan angle of 45° in the H-plane is considered     

Mode orthogonality in chirowaveguides

The orthogonality relations for modes supported by a general cylindrical chirowaveguide are derived. These waveguiding structures are cylindrical waveguides containing chiral materials. It is pointed out that one of these relations is valid for lossless waveguides, whereas the other holds for the lossy as well as the lossless case. It is demonstrated that the orthogonality relations can be used to express an arbitrary electric or magnetic field within a chirowaveguide in terms of the mode functions. As in conventional waveguides, the orthogonality relations reported can be used to expand an arbitrary E or H field within a chirowaveguide in terms of a complete set of mutually orthogonal modes in the waveguide     

New boundary integral equations for CAD of waveguide circuits:guided-mode extracted integral equations

Novel boundary integral equations which are applicable to the analysis of many kinds of waveguide circuits are presented. The new integral equations can treat the waveguide discontinuity problems like the scattering by the isolated finite-sized metallic objects or cavity problems and do not use normal-mode expansion techniques. They are suitable for the basic theory of CAD software for various waveguide circuits. The two-port and H-plane waveguide discontinuity problems which satisfy the single-mode and two-mode conditions are treated. The case of waveguide corner bend is considered as an example. Numerical examples are shown in order to confirm the validity of the new integral equations     

A rigorous and efficient method of moments solution for curvedwaveguide bends

An accurate and computationally efficient method of moments solution together with a mode-matching technique for the analysis of curved bends in a general parallel-plate waveguide is presented. In order to exemplify the techniques, the method is applied to study the transmission characteristics of single and cascaded curved E- and H-plane bends in a rectangular waveguide. It is shown that the effect of the orientation of cascaded bends on the transmission properties can be significant, and examples to demonstrate this effect are included. Results of the convergence with increasing number of expansion functions illustrate that only a few terms need to be considered for accurate evaluation of the transmission characteristics of structures with single and multiple bends. Comparison with measurements for single and cascaded curved H-plane bends in a WR-90 waveguide show good agreement with the predicted result     

Modal S-matrix design of metal finned waveguide componentsand its application to transformers and filters

Optimized all-metal E-plane finned waveguide components are designed with the rigorous method of modal field expansion into the ridged eigenmodes, which includes both the higher order mode interaction between the step discontinuities and the finite thickness of the fins. The design, which combines the advantage of constant fin thickness with that of the optimum matching potential of different waveguide inner cross-section dimensions and fin heights, achieves very broadband transformers and evanescent-mode filters with improved performance. Computer optimized data demonstrate the efficiency of the method by typical design examples: compact transformers for WR112, WR42, WR15, and WR12 input waveguides to E-plane finned waveguides, corrugated lowpass filters designed for a cutoff frequency in the waveguide Ku and U bands, and an evanescent-mode bandpass filter with unequal fin heights. The theory is verified by available measurements