Array Of Rectangular Waveguides Research Articles

Antenna Array Fault Diagnosis in the Presence of Mutual Coupling Using Excitations Optimization Technique: A Case Study of Rectangular Waveguide Array

Antenna Array Fault Diagnosis in the Presence of Mutual Coupling Using Excitations Optimization Technique: A Case Study of Rectangular Waveguide Array

A Recovery Performance Study of Compressive Sensing Methods on Antenna Array Diagnosis from Near-Field Measurements

Antenna testing consists locating the potential defaults from radiated field measurements. It has been established in literature, that compressive sensing methods provide faster results in failure detection from smaller number of measurement data compared to the traditional back-propagation mechanisms. Compressive sensing (CS) methods require a priori measurement of failure-free reference array and require small number of measurements for diagnosis. However, there are conflicting reports in literature regarding the choice of appropriate CS method, and there is no sufficient comparison study to justify which one is a better choice under a very harsh condition. In this study, recovery performance test of CS methods for the diagnosis of antenna array from few near-field measured data under various signal-to-noise ratios (SNRs) is presented. Specifically, we tested three prominent regularization procedures: total variation (TV), mixed l1/ l2 norm, and minimization of the l1 in solving diagnosis problems in antenna array. Linear system that relates the difference between near-field measured data from reference antenna (RA) array and array under test (AUT), and the difference that exist between coefficients of RA and the AUT, is solved by the three compressive sensing regularization methods. Numerical experiment of a 10 × 10 rectangular waveguide array under realistic noise scenario, operating at 10 GHz is used to conduct the test. Minimization l1 technique is more robust to additive data noise. It exhibits better diagnosis at 20 dB and 10 dB SNR, making it a better candidate for noisy measured data as compared to other techniques.

GLOBAL METHOD COMBINED WITH FLOQUET MODAL ANALYSIS TO MODEL AN ANTENNA BASED ON RECTANGULAR WAVEGUIDE ARRAY

In this study, we propose a new formulation based on a global method to model a rectangular waveguide array as antenna. Our method consists to combine the method of moment (MoM), the generalized equivalent circuit method (GECM) and Floquet modal analysis. Looking for rigor, simplicity and rapidity, we repose always on the simple discontinuity in an open rectangular waveguide. So, we extended our pervious works to study in first step an infinite rectangular waveguides array and we achieve with a finite one. For validation purpose, we consider two rectangular waveguides and we compered it whit the same structure studied by direct method in our previous study. Obtained numerical results are presented and discussed. A good agreement is shown and the boundary conditions are verified.

A compact polarization beam splitter based on an array of rectangular waveguides

In this paper a compact polarization beam splitter is proposed. The splitter consists of an array of four rectangular waveguides in a metal slab. The waveguides are designed to allow only the TE1,0 and the TE0,1 modes, which are responsible for the transmission of both polarizations of the input separately and thereby phase shifting each polarization independently based on the width and height of the waveguide. The finite difference time domain technique is used to simulate and verify the proposed structure. With proper choice of the dimensions of the waveguides and the thickness of the metal slab, the two polarizations were split by around 20° with extinction ratios of 36.2 and 34.6 dB.

An analysis of lower hybrid grill coupling using an efficient full wave code

Lower hybrid (LH) waves are very important for heating and current drive in tokamaks. Phased arrays of rectangular waveguides, generally called grills, are typically used as launchers. We develop a code which solves, in the 3D geometry of the grill structure, the problem of efficient coupling: the power density spectrum of the emitted waves, the power reflection coefficient, the power lost by the waves launched in the inaccessible region and the directivity of the waves transmitted into the accessible region. The code is also able to determine the 3D electric field in front of the grill. An efficient adaptive full wave solver is used to determine the wave propagation in a 1D plasma slab geometry. To evaluate the very large number of 2D k-space infinite integrals for the coupling elements, we have developed a method based on high order Gaussian quadratures combined with 2D B-splines in the accessible region for the plasma related part of the integrands. This method is well suited to handle large structures and many modes because the computational time is only weakly dependent on the size of the problem. An iterative evaluation of the integrands in the inaccessible region is adopted to handle the presently overlooked near singular behaviour of the integrands as well as the spectral power density associated with the eigenmodes. The role of collisions is clarified in this context. The code is applied to several COMPASS grills operating either at 1.3 GHz or at 3.7 GHz. First we thouroughly analyse the original 1.3 GHz, 8-waveguide conventional grill at various waveguide phasing. Then, the coupling of two grill designs for 3.7 GHz is solved. The suitability of all the grills is discussed, showing compatible grill and plasma parameter ranges.

Synthesis of antenna arrays with shaped-beam patterns

A method for the synthesis of the amplitude-phase distribution of an antenna array, which uses embedded element patterns, is developed. In the general case, the method ensures formation of an arbitrary shaped-beam pattern. Features of the synthesis of shaped-beam patterns of antenna arrays with elliptical polarization and vector patterns are considered. The numerical analysis of the synthesis method, which is performed for an array of rectangular waveguides with vector patterns, confirms the efficiency of the proposed approach.

Synthesis of multilobe array-antenna patterns with controlled levels, phases, and polarization of the pattern maxima

A method for the synthesis of the amplitude-phase distribution over an array antenna, which uses embedded element patterns and ensures formation of a multilobe pattern with controlled levels, phases, and polarization of the lobe maxima, is developed. Numerical studies are performed by the example of an array of rectangular waveguides with vector patterns. The results of these studies confirm the efficiency of the proposed solutions.

Excitation of a Parallel Plate Waveguide by an Array of Rectangular Waveguides

The problem of exciting a parallel plate waveguide by a linear array of rectangular waveguides is considered. Coupled integral equations are formulated for the aperture electric field at the junction. The integral equations are solved by the method of moments. Numerical results for the reflection coefficient as a function of scan angle are presented. Vertical and horizontal polarizations in the parallel plate guide are realized by TE10 and TE01 modes of excitation in the rectangular waveguides, respectively. E-plane and H-plane coupling between elements is presented. The method of moments results for a large finite array have been validated by comparing its reflection coefficients with corresponding results for an infinite array generated by the commercial finite element code, HFSS.

New applications of the theorem on the extremal properties of the characteristic numbers of a sheaf of Hermitian forms in optimization problems for multifunction antenna arrays

It is shown that optimization problems for multifunction antenna systems can be solved via reduction of new nonclassical functionals to a ratio of Hermitian forms with subsequent application of the theorem on the extremal properties of the characteristic numbers of a sheaf of Hermitian forms. Numerical investigations are performed with an array of rectangular waveguides with vector radiation patterns. The results obtained confirm the high efficiency of the proposed solutions.

Light-Induced Array of Three-Dimensional Waveguides in LithiumNiobate by Employing Two-Beam Interference Field

We propose a novel approach to fabricate an array of three-dimensionalwaveguides in lithium niobate by employing illuminations of a pair ofmutually coherent or incoherent two-beam interference patterns.Adjusting periods of the patterns and the angle between the gratingvectors of the two patterns, we find that arrays of square, rectangularor parallelogrammic waveguides can be created. An array of rectangularwaveguides is demonstrated in an iron doped lithium niobate by the doubleexposures of two-beam interference patterns with differentorientations. The measured index distribution and the guiding testresults show that the waveguide array is successfully fabricated.

An efficient method of radiation attenuation through aircraft cooling vents

Some critical avionic systems require cooling air via vents on the side of the aircraft, thus creating leakage points for high-intensity electromagnetic radiation. This paper presents a novel application of high-intensity radiated field (HIRF) shielding using a rectangular waveguide array, while maintaining cooling airflow requirements. Signal attenuation versus frequency and depth of the array has been calculated using closed-form equations. The simulation and measurement results are in good agreement with the calculated values. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 130–132, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20566

Formation of Nulls in Vector Beam Patterns of Monopulse Arrays of Rectangular Waveguides by Correcting Currents in Some Array Elements

In this paper, we consider a method for null synthesis in the vector sum and difference beam patterns of a monopulse array of rectangular waveguides. The synthesis of nulls is reached due to variation of complex currents in some elements. The proposed method eliminates shifts of the primary maximum and the nulls of the sum and difference beam patterns, respectively, of a monopulse array. Numerical studies confirming the efficiency of the proposed method are described.

Truncated floquet wave full-wave (T(FW)/sup 2/ ) analysis of large periodic arrays of rectangular waveguides

A new hybrid technique has been recently proposed for the analysis of large periodic arrays. This method is based on a high-frequency representation of the active Green's function of a finite array, involving a Floquet wave (FW) expansion with the relevant edge and vertex diffracted ray fields originating at the array border. Using this representation, the unknown current of an appropriate fringe integral equation is expanded in terms of a few basis functions shaped as FW-induced diffracted rays. This representation drastically reduces the numerical effort and provides a physical insight into the mechanism of the array truncation. In this paper, this method is applied to the analysis of large arrays of rectangular waveguides opened on an infinite ground plane. Numerical results are shown to demonstrate the effectiveness and the numerical efficiency of the method.

Blindness removal in arrays of rectangular waveguides using dielectrically loaded hard walls

We analyze an infinite planar array of open-ended rectangular waveguides in which the E-plane walls are loaded with dielectric slabs in order to create a hard boundary condition. The analysis is done by using the mode-matching method with Floquet modes in the exterior region. The results show that the hard walls remove the blind spots otherwise present in the element patterns of wide-angle scanning arrays. This occurs both for rectangular and for triangular lattices. In addition, the array becomes better matched to free-space in a rectangular lattice. In limited-scan arrays of large square waveguides, the use of the hard walls increases the array gain by 0.9 dB, it reduces the grating lobe level in the H plane by 11 dB and considerably decreases the difference between the array characteristics in the E and H planes.

Moment method model of a slot immersed in a planar array of waveguide slot radiators

A moment method analysis applied directly to a planar distribution of shunt slot radiators fed by an array of rectangular waveguides is described. The method intrinsically accommodates both the internal and external mutual interactions between the radiators, and the influence of these interactions on the resonance characteristics of slots embedded within a typical slot array is explicitly demonstrated. Low height and dielectric-loaded waveguide arrays are also examined and in these cases it is observed that additional care must be exercised in the selection of a representative basis function series to model the slot field distribution. Also, by employing entire domain basis functions the processor time demanded by these calculations, which are computationally intensive even for relatively small numbers of slots, can be substantially reduced. Computational efficiency gains of this description are essential if the procedure described is to have a real impact on the development of computer aided design packa...

Generalized moment method analysis of planar reactively loaded rectangular waveguide arrays

A combined modal expansion and moment method is applied for analyzing finite planar arrays of rectangular waveguides in an infinite ground plane including reactively loaded waveguide elements. The analysis, which is based on the moment method for solving the aperture problem, in combination with the modal analysis for the reactively loaded waveguide cavities or feeding waveguides, extends the network formulation of single apertures to multiple waveguide arrays including reactively loaded elements. Two orthogonally polarized sets of basic functions are utilized to model the expansion into the complete set of eigenmodes is used to formulate the waveguide cavity problem. The theory is applied to a finite planar array of arbitrarily spaced rectangular waveguides, where reactive loads are realized by placing sliding electrical conductors at specified distances in each of the unfed waveguides. Numerical design examples show that beamforming, beamsteering, and the improvement of the crosspolarization behavior is possible by a suitable choice of the geometrical parameters. The theory is verified by results available from the literature as well as newly performed experimental measurements. >

Electric field distributions of waveguide arrays for local tumor hyperthermia.

Total electric field distributions in muscle and fat tissues, due to colinear rectangular waveguide arrays at 2.45 GHz and 915 MHz were calculated. The effect of phase difference between incident phases on the field pattern is shown. Phase adjustment is capable of furnishing control of either field-size or focused-field performance of the multi-element, direct-contact applicator. The tissue-applicator junction is analyzed by means of the Generalized Scattering Matrix (GSM) of the generalized 2-port discontinuity, assuming that the lossy homogeneous tissue is immersed in a large waveguide. This method provides an exact calculation of multimodal fields, as well as reflection and coupling coefficients in the apertures.

Mutual coupling in finite coplanar rectangular waveguide arrays

Mutual admittance expressions are given for all possible combinations of mode coupling in an array of identical collinear rectangular waveguides opening into an infinite ground plane. Specific results are presented for the worst case of E-plane coupling between identical square waveguide to show that significant high-order mode excitation can occur. Some of these modes are a source of crosspolarisation, making mutual coupling important to the prediction of the crosspolar pattern of a rectangular waveguide array.

Moment method analysis of finite rectangular waveguide phased arrays

A method of moments formulation for small finite planar phased arrays of rectangular waveguides in an infinite ground plane is investigated. Piecewise sinusoidal-uniform surface patches are used as the basis and testing functions for the unknown equivalent magnetic currents of each aperture. The block-Toeplitz symmetry property for rectangular grid arrays is utilized in the solution of the system of equations. Data are presented for 11 \times 11 arrays with various element sizes, element spacings, and scan angles. Good agreement with data in the literature is shown. The analysis is particularly efficient for E - plane and H -plane scans for arrays having rectangular waveguide-fed apertures excited by the dominant mode.

Mutual coupling in a linear array of rectangular waveguides

Asymptotic decay of the mutual coupling coefficient (C) aS a function of interelement distance (S) is measured in a linear array of rectangular waveguides with and without dielectric loadings. It is found that for dielectric plug loading, a plug thickness of half the guide wavelength in the dielectric (λge) gives the strongest mutual coupling between the elements of the array. This plug thickness matches an isolated guide opening in a ground plane. For no dielectric loading and for plugs, the decay law is C ∞ Sp, p being some constant.