A technique of synthesizing the excitation currents of planar arrays or apertures
TL;DR: In this article, a technique of synthesizing or reconstructing the excitation currents of a planar array of aperture-type antennas from the known near-field patterns of the radiating source is presented.
Abstract: A technique of synthesizing or reconstructing the excitation currents of a planar array of aperture-type antennas from the known near-field patterns of the radiating source is presented. This technique uses an exact solution to the fields radiated by the aperture antenna without disregarding the source currents. Typical numerical computations have been carried out to validate the analytical technique developed. Sensitivity and stability of the numerical computations performed have been studied. The available iterative bandlimited signal extrapolation technique is used to reconstruct the aperture excitation currents only if the far-field patterns of the radiating source are known. Far-field patterns of aperture antennas measured in the laboratory were also used to reconstruct the aperture electric field distribution in the principal plane. >
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TL;DR: In this article, an electric field integral equation (EFIE) is developed to relate the near fields to the equivalent magnetic currents, and the method of moments is used to transform the integral equation into a matrix one.
Abstract: An alternative method is presented for computing far-field antenna patterns from near-field measurements. The method utilizes the near-field data to determine equivalent magnetic current sources over a fictitious planar surface that encompasses the antenna, and these currents are used to ascertain the far fields. Under certain approximations, the currents should produce the correct far fields in all regions in front of the antenna regardless of the geometry over which the near-field measurements are made. An electric field integral equation (EFIE) is developed to relate the near fields to the equivalent magnetic currents. The method of moments is used to transform the integral equation into a matrix one. The matrix equation is solved with the conjugate gradient method, and in the case of a rectangular matrix, a least-squares solution for the currents is found without explicitly computing the normal form of the equation. Near-field to far-field transformation for planar scanning may be efficiently performed under certain conditions. Numerical results are presented for several antenna configurations. >
260 citations
TL;DR: In this article, a method for computing near and far-field patterns of an antenna from its near-field measurements taken over an arbitrarily shaped geometry is presented, where the measured data need not satisfy the Nyquist sampling criteria and an electric field integral equation is developed to relate the near field to the equivalent electric current.
Abstract: Presented here is a method for computing near- and far-field patterns of an antenna from its near-field measurements taken over an arbitrarily shaped geometry. This method utilizes near-field data to determine an equivalent electric current source over a fictitious surface which encompasses the antenna. This electric current, once determined, can be used to ascertain the near and the far field. This method demonstrates the concept of analytic continuity, i.e., once the value of the electric field is known for one region in space, from a theoretical perspective, its value for any other region can be extrapolated. It is shown that the equivalent electric current produces the correct fields in the regions in front of the antenna regardless of the geometry over which the near-field measurements are made. In this approach, the measured data need not satisfy the Nyquist sampling criteria. An electric field integral equation is developed to relate the near field to the equivalent electric current. A moment method procedure is employed to solve the integral equation by transforming it into a matrix equation. A least-squares solution via singular value decomposition is used to solve the matrix equation. Computations with both synthetic and experimental data, where the near field of several antenna configurations are measured over various geometrical surfaces, illustrate the accuracy of this method.
230 citations
Cites background from "A technique of synthesizing the exc..."
...Appel–Hansen presents a detailed description of planar, cylindrical, and spherical scanning in [11]....
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TL;DR: In this paper, a simple and effective procedure for the reduction of truncation errors in planar near-field measurements of aperture antennas is presented, which relies on the consideration that, due to the scan plane truncation, the calculated plane wave spectrum of the field radiated by the antenna is reliable only within a certain portion of the visible region.
Abstract: A simple and effective procedure for the reduction of truncation errors in planar near-field measurements of aperture antennas is presented. The procedure relies on the consideration that, due to the scan plane truncation, the calculated plane wave spectrum of the field radiated by the antenna is reliable only within a certain portion of the visible region. Accordingly, the truncation error is reduced by extrapolating the remaining portion of the visible region by the Gerchberg-Papoulis iterative algorithm, exploiting a condition of spatial concentration of the fields on the antenna aperture plane. The proposed procedure is simple and computationally efficient; it does not require any modification of the measurement procedure and it allows for the usual probe correction. Far-field patterns reconstructed from both simulated and measured truncated near-field data demonstrate its effectiveness and stability against measurement inaccuracies.
54 citations
Cites methods from "A technique of synthesizing the exc..."
...In fact, a similar iterative procedure was previously applied to determine, from far-field data, surface distortions in large reflector antennas [17], or the excitation currents of planar arrays or apertures for both pattern synthesis [18] and array antenna diagnosis and calibration [19], [20]....
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TL;DR: In this article, a conformal waveguide array is used to generate and control the beam focus within the near-field treatment region for hyperthermia treatment in the K band (18-26 GHz).
Abstract: Microwave hyperthermia is rapidly evolving as a fourth modality in the fight against cancer, along with surgery, radiation and chemotherapy. This form of cancer treatment utilises a narrow microwave beam to heat the tumour volume to a temperature of ∼42°C; however, with minimal energy delivery to neighbouring healthy tissue, which is one of the main challenges in hyperthermia technology. Potentially, this application can be achieved by using a phased array of apertures or dipoles to generate and control the beam focus within the near-field treatment region. This paper describes another approach to near-field beam forming by using of a conformal waveguide array, operating in the K band (18–26 GHz). The array comprises a central movable element that acts as the focusing element, and surrounding fixed directing elements. The focusing element gives conformal property to the array and serves two purposes: firstly to obtain a sharp focus at a prescribed near-field location, and secondly the added flexibility to move the beam around the tumour. Several simulations and measurements have been performed on linear and planar configurations, which demonstrate the ability of the array to achieve beam widths as small as∼4 mm, with a maximum beam movement range of ∼15 mm.
17 citations
01 Nov 2006
TL;DR: In this article, a simple and effective procedure for the reduction of truncation error in planar near-field to far-field transformations is presented, where the actual scan plane truncation implies a reliability of the reconstructed plane wave spectrum of the field radiated by the antenna only within a certain region inside the visible range.
Abstract: A simple and effective procedure for the reduction of truncation error in planar near-field to far-field transformations is presented. The starting point is the consideration that the actual scan plane truncation implies a reliability of the reconstructed plane wave spectrum of the field radiated by the antenna only within a certain region inside the visible range. Then, the truncation error is reduced by a Maxwellian continuation of the reliable portion of the spectrum: after back propagating the measured field to the antenna plane, a condition of spatial concentration of the primary field is exploited to define a convergent iterative process which is also stable against moderately noisy data. Far-field patterns reconstructed from both simulated and measured near-field data demonstrate the effectiveness of the proposed procedure.
3 citations
Additional excerpts
...has already been applied to determine, from far-field data, surface distortions in large reflector antennas [17] and the individual element excitations of planar arrays for pattern synthesis [18] or array antenna diagnosis and calibration [19]....
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References
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Book•
01 Jan 1982
TL;DR: The most up-to-date resource available on antenna theory and design as mentioned in this paper provides an extended coverage of ABET design procedures and equations making meeting ABET requirements easy and preparing readers for authentic situations in industry.
Abstract: The most-up-to-date resource available on antenna theory and design Expanded coverage of design procedures and equations makes meeting ABET design requirements easy and prepares readers for authentic situations in industry New coverage of microstrip antennas exposes readers to information vital to a wide variety of practical applicationsComputer programs at end of each chapter and the accompanying disk assist in problem solving, design projects and data plotting-- Includes updated material on moment methods, radar cross section, mutual impedances, aperture and horn antennas, and antenna measurements-- Outstanding 3-dimensional illustrations help readers visualize the entire antenna radiation pattern
14,065 citations
Book•
01 Jun 1961
TL;DR: In this paper, a revised version of the Revised edition of the book has been published, with a new introduction to the concept of plane wave functions and spherical wave functions, as well as a detailed discussion of the properties of these functions.
Abstract: Foreword to the Revised Edition. Preface. Fundamental Concepts. Introduction to Waves. Some Theorems and Concepts. Plane Wave Functions. Cylindrical Wave Functions. Spherical Wave Functions. Perturbational and Variational Techniques. Microwave Networks. Appendix A: Vector Analysis. Appendix B: Complex Permittivities. Appendix C: Fourier Series and Integrals. Appendix D: Bessel Functions. Appendix E: Legendre Functions. Bibliography. Index.
5,655 citations
Book•
01 Jan 1981
TL;DR: In this paper, the authors present an approach for the synthesis of a single antenna array from a single-antenna array using a modified version of Taylor's Taylor diagram and a modified Taylor diagram with a modified ring side lobe topography.
Abstract: Foreword to the Revised Edition. Preface to the Revised Edition. Preface. I SOURCE-FIELD RELATIONS SINGLE ANTENNA ELEMENTS. 1 The Far-Field Integrals, Reciprocity, Directivity. 1.1 Introduction. 1.2 Electrostatics and Magnetostatics in Free Space. 1.3 The Introduction of Dielectric, Magnetic, and Conductive Materials. 1.4 Time-Varying Fields. 1.5 The Retarded Potential Functions. 1.6 Poynting's Theorem. 1.7 The Stratton-Chu Solution. 1.8 Conditions at Infinity. 1.9 Field Values in the Excluded Regions. 1.10 The Retarded Potential Functions: Reprise. 1.11 The Far Field: Type I Antennas. 1.12 The Schelkunoff Equivalence Principle. 1.13 The Far Field: Type IL Antennas. 1.14 The Reciprocity Theorem. 1.15 Equivalence of the Transmitting and Receiving Patterns of an Antenna. 1.16 Directivity and Gain. 1.17 Receiving Cross Section. 1.18 Polarization of the Electric Field. 2 Radiation Patterns of Dipoles, Loops, and Helices. 2.1 Introduction. 2.2 The Center-Fed Dipole. 2.3 Images in a Ground Plane. 2.4 A Monopole Above a Ground Plane. 2.5 A Dipole in Front of a Ground Plane. 2.6 The Small Current Loop. 2.7 Traveling Wave Current on a Loop. 2.8 The End-Fire Helix. 3 Radiation Patterns of Horns, Slots and Patch Antennas. 3.1 Introduction. 3.2 The Open-Ended Waveguide. 3.3 Radiation from Horns. 3.4 Center-Fed Slot in Large Ground Plane. 3.5 Waveguide-Fed Slots. 3.6 Theory of Waveguide-Fed Slot Radiators. 3.7 Patch Antennas. II ARRAY ANALYSIS AND SYNTHESIS. 4 Linear Arrays: Analysis. 4.1 Introduction. 4.2 Pattern Formulas for Arrays with Arbitrary Element Positions. 4.3 Linear Arrays: Preliminaries. 4.4 Schelkunoff's Unit Circle Representation. 5 Linear Arrays: Synthesis. 5.1 Introduction. 5.2 Sum and Difference Patterns. 5.3 Dolph-Chebyshev Synthesis of Sum Patterns. 5.4 Sum Pattern Beamwidth of Linear Arrays. 5.5 Peak Directivity of the Sum Pattern of a Linear Array. 5.6 A Relation Between Beamwidth and Peak Directivity for Linear Arrays. 5.7 Taylor Synthesis of Sum Patterns. 5.8 Modified Taylor Patterns. 5.9 Sum Patterns with Arbitrary Side Lobe Topography. 5.10 Discretization of a Continuous Line Source Distribution. 5.11 Bayliss Synthesis of Difference Patterns. 5.12 Difference Patterns with Arbitrary Side Lobe Topography. 5.13 Discretization Applied to Difference Patterns. 5.14 Design of Linear Arrays to Produce Null-Free Patterns. 6 Planar Arrays: Analysis and Synthesis. 6.1 Introduction. 6.2 Rectangular Grid Arrays: Rectangular Boundary and Separable Distribution. 6.3 Circular Taylor Patterns. 6.4 Modified Circular Taylor Patterns: Ring Side Lobes of Individually Arbitrary Heights. 6.5 Modified Circular Taylor Patterns: Undulating Ring Side Lobes. 6.6 Sampling Generalized Taylor Distributions: Rectangular Grid Arrays. 6.7 Sampling Generalized Taylor Distributions: Circular Grid Arrays. 6.8 An Improved Discretizing Technique for Circular Grid Arrays. 6.9 Rectangular Grid Arrays with Rectangular Boundaries: Nonseparable Tseng-Cheng Distributions. 6.10 A Discretizing Technique for Rectangular Grid Arrays. 6.11 Circular Bayliss Patterns. 6.12 Modified Circular Bayliss Patterns. 6.13 The Discretizing Technique Applied to Planar Arrays Excited to Give a Difference Pattern. 6.14 Comparative Performance of Separable and Nonseparable Excitations for Planar Apertures. 6.15 Fourier Integral Representation of the Far Field. III SELF-IMPEDANCE AND MUTUAL IMPEDANCE, FEEDING STRUCTURES. 7 Self-Impedance and Mutual Impedance of Antenna Elements. 7.1 Introduction. 7.2 The Current Distribution on an Antenna: General Formulation. 7.3 The Cylindrical Dipole: Arbitrary Cross Section. 7.4 The Cylindrical Dipole: Circular Cross Section, Hallen's Formulation. 7.5 The Method of Moments. 7.6 Solution of Hallen's Integral Equation: Pulse Functions. 7.7 Solution of Halle'n's Integral Equation: Sinusoidal Basis Functions. 7.8 Self-Impedance of Center-Fed Cylindrical Dipoles: Induced EMF Method. 7.9 Self-Impedance of Center-Fed Cylindrical Dipoles: Storer's Variational Solution. 7.10 Self-Impedance of Center-Fed Cylindrical Dipoles: Zeroth and First Order Solutions to Hallen's Integral Equation. 7.11 Self-Impedance of Center-Fed Cylindrical Dipoles: King-Middleton Second-Order Solution. 7.12 Self-Impedance of Center-Fed Strip Dipoles. 7.13 The Derivation of a Formula for the Mutual Impedance Between Slender Dipoles. 7.14 The Exact Field of a Dipole: Sinusoidal Current Distribution. 7.15 Computation of the Mutual Impedance Between Slender Dipoles. 7.16 The Self-Admittance of Center-Fed Slots in a Large Ground Plane: Booker's Relation. 7.17 Arrays of Center-Fed Slots in a Large Ground Plane: Self-Admittance and Mutual Admittance. 7.18 The Self-Impedance of a Patch Antenna. 8 The Design of Feeding Structures for Antenna Elements and Arrays. 8.1 Introduction. 8.2 Design of a Coaxially Fed Monopole with Large Ground Plane. 8.3 Design of a Balun-Fed Dipole Above a Large Ground Plane. 8.4 Two-Wire-Fed Slots: Open and Cavity-Backed. 8.5 Coaxially Fed Helix Plus Ground Plane. 8.6 The Design of an Endfire Dipole Array. 8.7 Yagi-Uda Type Dipole Arrays: Two Elements. 8.8 Yagi-Uda Type Dipole Arrays: Three or More Elements. 8.9 Frequency-Independent Antennas: Log-Periodic Arrays. 8.10 Ground Plane Backed Linear Dipole Arrays. 8.11 Ground Plane Backed Planar Dipole Arrays. 8.12 The Design of a Scanning Array. 8.13 The Design of Waveguide-Fed Slot Arrays: The Concept of Active Slot Admittance (Impedance). 8.14 Arrays of Longitudinal Shunt Slots in a Broad Wall of Rectangular Waveguides: The Basic Design Equations. 8.15 The Design of Linear Waveguide-Fed Slot Arrays. 8.16 The Design of Planar Waveguide-Fed Slot Arrays. 8.17 Sum and Difference Patterns for Waveguide-Fed Slot Arrays Mutual Coupling Included. IV CONTINUOUS APERTURE ANTENNAS. 9 Traveling Wave Antennas. 9.1 Introduction. 9.2 The Long Wire Antenna. 9.3 Rhombic and Vee-Antennas. 9.4 Dielectric-Clad Planar Conductors. 9.5 Corrugated Planar Conductors. 9.6 Surface Wave Excitation. 9.7 Surface Wave Antennas. 9.8 Fast Wave Antennas. 9.9 Trough Waveguide Antennas. 9.10 Traveling Wave Arrays of Quasi-Resonant Discretely Spaced Slots [Main Beam at theta0= arccos(beta/k)]. 9.11 Traveling Wave Arrays of Quasi-Resonant Discretely Spaced Slots (Main Beam Near Broadside). 9.12 Frequency Scanned Arrays. 10 Reflectors and Lenses. 10.1 Introduction. 10.2 Geometrical Optics: The Eikonal Equation. 10.3 Simple Reflectors. 10.4 Aperture Blockage. 10.5 The Design of a Shaped Cylindrical Reflector. 10.6 The Design of a Doubly Curved Reflector. 10.7 Radiation Patterns of Reflector Antennas: The Aperture Field Method. 10.8 Radiation Patterns of Reflector Antennas: The Current Distribution Method. 10.9 Dual Shaped Reflector Systems. 10.10 Single Surface Dielectric Lenses. 10.11 Stepped Lenses. 10.12 Surface Mismatch, Frequency Sensitivity, and Dielectric Loss for Lens Antennas. 10.13 The Far Field of a Dielectric Lens Antenna. 10.14 The Design of a Shaped Cylindrical Lens. 10.15 Artificial Dielectrics: Discs and Strips. 10.16 Artificial Dielectrics: Metal Plate (Constrained) Lenses. 10.17 The Luneburg Lens. APPENDICES. A. Reduction of the Vector Green's Formula for E. B. The Wave Equations for A and D. C. Derivation of the Chebyshev Polynomials. D. A General Expansion of cosm v. E. Approximation to the Magnetic Vector Potential Function for Slender Dipoles. F. Diffraction by Plane Conducting Screens: Babinet's Principle. G. The Far-Field in Cylindrical Coordinates. H. The Utility of a Csc2 theta Pattern. Index.
1,023 citations