Reduction of electromagnetic field coupling to microwave microstrip circuits

The signals induced by an external electromagnetic field along a microstrip line on a multilayered dielectric substrate were studied. The main target of the work is not to introduce a new technique of study but to search for suitable combinations of the structural and geometrical characteristics of the printed geometry whereby the electromagnetic interference of the external field to the circuit would be reduced. This reduction is desirable in all modern applications. The results derived prove that this object can be achieved at high frequencies and when the substrate is multilayered.     

Modal analysis of the microwave frequency response and composite right‐/left‐handed operation of a rectangular waveguide loaded with double positive and double negative materials

This article presents a theoretical study of the electromagnetic wave propagation in a rectangular waveguide, loaded with double positive (DPS) and double negative (DNG) dielectrics. The frequency response of the waveguide is analyzed using a modal technique. The results show that when at least one of the dielectrics is a DNG material the cutoff frequency of the waveguide is much more lower than the cutoff frequency of the DPS loaded or the empty waveguide. This interesting property means that very low frequency signals could be guided by structures that have very small size. Properties of composite right‐ and left‐handed wave propagation are also observed as well as the characteristic stop‐band between the frequency regions in which RH and LH wave propagation occurs. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

On the treatment of wire antennas near an elliptic cylinder

Contents Presented in this paper are two hybrid methods for combining the method of moments (MM) with other techniques. Both these hybrid techniques treat the problem of thin linear antennas near an elliptic cylinder. The principle aim of this work was to compine the MM treatment of wire antennas with the GTD. The results are then verified using the hybrid moment method-eigenfunction solution (EIG-MM).—Results are shown for the radiation pattern and the input impedance of arrays of dipoles near an elliptic cylinder, as well as for a single dipole. For arrays, results for the mutual impedance are also shown.

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Behandlung von Draht-Antennen in der Nähe eines elliptischen Zylinders

Übersicht In dieser Arbeit werden, zum Vergleich der Momenten-Methode (MM) mit anderen Techniken, zwei Hybrid-Methoden präsentiert. Beide Hybrid-Techniken befassen sich mit dem Problem einer linearen Antenne in der Nähe eines elliptischen Zylinders.—Der Hauptpunkt dieser Veröffentlichung besteht darin, die Momenten-Methode zur Studie von Draht-Antennen mit der GTD-Methode zu kombinieren. Die Ergebnisse werden durch eine Eigenfunktionen-Lösung der Hybrid-Momenten Methode (EIG-MM) bestätigt.—Ergebnisse für das Strahlungsmuster und die Eingangsimpedanz, wie sie sowohl durch eine Anordnung von Dipolen in der Nähe eines elliptischen Zylinders, als auch durch einen einzelnen Dipol entstehen, werden präsentiert. Weiter werden Ergebnisse für die gegenseitige Impedanz angegeben.

     

Design of optimum gain pyramidal horn using self‐adaptive differential evolution algorithms

In this work, we apply classical and new self‐adaptive differential evolution (DE) algorithms to the design of optimum gain pyramidal horns. The application of DE algorithms to pyramidal horn design allows the accurate calculation of their physical dimensions in a short amount of time. Moreover, self‐adaptive DE does not require the prespecified choice of control parameters reducing significantly the users' effort. Representative examples demonstrate the applicability of our proposal. Our study shows that self‐adaptive DE algorithms outperform or produce similar results with other methods in the literature in terms of solution accuracy and convergence speed. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Analysis of a conformal array of slots on a perfectly — conducting elliptic cylinder

Contents In this paper the geometrical theory of diffraction is used to determine the mutual coupling and the received voltages from rectangular slots performing a conformal array in a perfectly conducting elliptic cylinder. Results for arrays with two and three slots show the practicality of such array in the direction finding. Especially it is shown that cylinders with large axial ratio give smoother results.

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Analyse einer gleichförmigen Spaltenanordnung auf einem perfektleitenden elliptischen Zylinder

Übersicht In dieser Arbeit wird die geometrische Beugungstheorie zur Bestimmung der gegenseitigen Kopplung und der empfangenen Spannung an rechteckigen Spalten, welche in einem perfekt leitenden elliptischen Zylinder eine gleichförmige Anordnung bilden, benutzt. Die Ergebnisse für Anordnungen mit zwei oder drei Spalten zeigen die praktische Anwendbarkeit solcher Anordnungen für die Funkpeilung. Insbesondere wird gezeigt, daß Zylinder mit langen Achsverhältnissen glattere Ergebnisse liefern.

     

A simplification of the synthesis of parallel wire antenna arrays

Using the moment method, a wire antenna array pattern is expressed in a form similar to that of a point source. The synthesis is thus reduced to that using well-known methods. The method is applied to linear as well as to planar arrays. Examples presented for several arrays how excellent agreement between the desired and the resulting patterns. The uncorrected patterns (without taking into account the mutual coupling) give similar results to the desired ones for arrays with many dipoles and equidistance greater than 0.50 λ. A method to improve the uncorrected pattern is proposed that is based on the addition of two parasitic elements     

Theoretical approach of the assessment of the EM field in the vicinity of aperture antennas

In this work, an assessment of the influence of the field probes on the uncertainty in the measurements of the electric and magnetic field in the vicinity of aperture antennas is presented. A uniform aperture distribution is considered because the field of a tapered distribution aperture can be reduced to that of a uniform one. Moreover, the effect of probe size and configuration is presented through a comparison between the theoretically calculated and the expected values. Field probes of a single or more perpendicular dipoles are investigated. The maximum permissible length of the dipoles for an accurate field assessment depends on the field's gradient. In the regions where the relative amplitude and phase of the electric field along the measuring device does not exhibit considerable variation, even half-wavelength dipoles can be used. It is also found that probes with sizes less than 0.1/spl lambda/ ensure measurement uncertainty less than 0.5 dB for field variation up to 7 dB//spl lambda/.     

An antenna array synthesis technique by the help of Chebyshev polynomials

Contents A method for synthesis of antenna arrays with a given number of sidelobes and sidelobe levels is discussed. The pattern is given as a multiplication of a Chebyshev polynomial of n^th degree with the one of first degree. The radiation pattern of a wire antenna in a form similar to that of an array with point sources is also given by the method of moments. So the synthesis procedure can be reduced. Several examples show the applicability of the method.

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Eine Methode für den Entwurf von Hilfe der Chebyschevschen Polynome

Übersicht In der vorliegenden Arbeit wird eine Methode für den Entwurf von strahlungsgekoppelten Drahtstrukturen mit vorgegebener Anzahl der Nebenzipfel und Nebenkeulendämpfung behandelt. Das Richtdiagramm wird als Produkt eines Chebyshevschen Polynomsn-ten Grades mit einem Polynom ersten Grades angesehen. Außerdem wird mit Hilfe der Momentenmethode die Strahlungscharakteristik einer Drahtantenne in Form einer aus Punktquellen bestehenden strahlenden Linie angegeben. Dadurch wird der Entwurf auf letztere zurückgeführt. Mehrere Beispiele deuten die Anwendbarkeit dieser Methode an.

     

Artificial neural network based design of a three-layered microstrip circular ring antenna with specified multi-frequency operation

This paper deals with the utilization of Artificial Neural Networks (ANN) methodology in the design of microstrip antennas having a priori defined operational features. A printed annular ring antenna, textured by slits, was designed in a multilayered dielectric substrate. The width and the position of the slits along with the values of the structural parameters and the feed position of the antenna affect directly its frequency performance. The inverse problem, namely to find out the proper combination of all these parameter values which would yield the desired frequency response, was solved via a Multiple Layer Perceptron (MLP) Neural Network.