Side lobe

About: Side lobe is a research topic. Over the lifetime, 4422 publications have been published within this topic receiving 34058 citations.

A Current Distribution for Broadside Arrays Which Optimizes the Relationship between Beam Width and Side-Lobe Level

Abstract: A one-parameter family of current distributions is derived for symmetric broadside arrays of equally spaced point sources energized in phase. For each value of the parameter, the corresponding current distribution gives rise to a pattern in which (1) all the side lobes are at the same level; and (2) the beam width to the first null is a minimum for all patterns arising from symmetric distributions of in-phase currents none of whose side lobes exceeds that level. Design curves relating the value of the parameter to side-lobe level as well as the relative current values expressed as a function of side-lobe level are given for the cases of 8-, 12-, 16-, 20-, and 24-element linear arrays.

Antenna theory and design

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.

The theory and design of chirp radars

Abstract: A new radar technique has been developed that provides a solution for the conflicting requirements of simultaneous long-range and high-resolution performance in radar systems. This technique, called Chirp at Bell Telephone Laboratories, recognizes that resolution depends on the transmitted pulse bandwidth. A long high-duty-factor transmitted pulse, with suitable modulation (linear frequency modulation in the case of Chirp), which covers a frequency interval many times the inherent bandwidth of the envelope, is employed. The receiver is designed to make optimum use of the additional signal bandwidth. This paper contains many of the important analytical methods required for the design of a Chirp radar system. The details of two signal generation methods are considered and the resulting signal waveforms and power spectra are calculated. The required receiver characteristics are derived and the receiver output waveforms are presented. The time-bandwidth product is introduced and related to the effective increase in the performance of Chirp systems. The concept of a matched filler is presented and used as a reference standard in receiver design. The effect of amplitude and phase distortion is analyzed by the method of paired echoes. One consequence of the signal design is the presence of time side lobes on the receiver output pulse analogous to the spatial side lobes in antenna theory. A method to reduce the time side lobes by weighting the pulse energy spectrum is explained in terms of paired echoes. The weighting process is described, and calculated pulse envelopes, weighting network characteristics and dele-???

Design of line-source antennas for narrow beamwidth and low side lobes

Abstract: It is well known that the phenomenon of radiation from line-source antennas is very similar to that of the diffraction of light from narrow apertures. Unlike the optical situation, however, antenna design technique permits the use of other-than-uniform distributions of field across the antenna aperture. Line source synthesis is the science of choosing this distribution function to give a radiation pattern with prescribed properties such as, for example, narrow angular width of the main lobe and low side lobes. In the present article the mathematical relationships involved in the radiation calculation are studied from the point of view of function theory. Some conclusions are drawn which outline the major aspects of synthesis technique very clearly. In particular, the problem of constructing a line source with an optimum compromise between beamwidth and side-lobe level (analogous to the Dolph - Tchebycheff problem in linear array theory) is considered. The ideal pattern is cos π √ {u /sup 2/ - A/sup 2/} , where u = (2a/λ) cos θ, a is the half-length of the source, and cosh π A is the side-lobe ratio. Because of theoretical limitations, this pattern cannot be obtained from a physically realizable antenna; nevertheless its ideal characteristics can be approached arbitrarily closely. The procedure for doing this is given in detail.

The Delay Multiply and Sum Beamforming Algorithm in Ultrasound B-Mode Medical Imaging

Abstract: Most of ultrasound medical imaging systems currently on the market implement standard Delay and Sum (DAS) beamforming to form B-mode images. However, image resolution and contrast achievable with DAS are limited by the aperture size and by the operating frequency. For this reason, different beamformers have been presented in the literature that are mainly based on adaptive algorithms, which allow achieving higher performance at the cost of an increased computational complexity. In this paper, we propose the use of an alternative nonlinear beamforming algorithm for medical ultrasound imaging, which is called Delay Multiply and Sum (DMAS) and that was originally conceived for a RADAR microwave system for breast cancer detection. We modify the DMAS beamformer and test its performance on both simulated and experimentally collected linear-scan data, by comparing the Point Spread Functions, beampatterns, synthetic phantom and in vivo carotid artery images obtained with standard DAS and with the proposed algorithm. Results show that the DMAS beamformer outperforms DAS in both simulated and experimental trials and that the main improvement brought about by this new method is a significantly higher contrast resolution (i.e., narrower main lobe and lower side lobes), which turns out into an increased dynamic range and better quality of B-mode images.