Topic
Phased array
About: Phased array is a(n) research topic. Over the lifetime, 19428 publication(s) have been published within this topic receiving 229231 citation(s). The topic is also known as: Phased Array Radar, PAR.
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TL;DR: Methods for simultaneously acquiring and subsequently combining data from a multitude of closely positioned NMR receiving coils are described, conceptually similar to phased array radar and ultrasound and hence the techniques are called the “NMR phased array.”
Abstract: We describe methods for simultaneously acquiring and subsequently combining data from a multitude of closely positioned NMR receiving coils. The approach is conceptually similar to phased array radar and ultrasound and hence we call our techniques the “NMR phased array.” The NMR phased array offers the signal-to-noise ratio (SNR) and resolution of a small surface coil over fields-of-view (FOV) normally associated with body imaging with no increase in imaging time. The NMR phased array can be applied to both imaging and spectroscopy for all pulse sequences. The problematic interactions among nearby surface coils is eliminated (a) by overlapping adjacent coils to give zero mutual inductance, hence zero interaction, and (b) by attaching low input impedance preamplifiers to all coils, thus eliminating interference among next nearest and more distant neighbors. We derive an algorithm for combining the data from the phased array elements to yield an image with optimum SNR. Other techniques which are easier to implement at the cost of lower SNR are explored. Phased array imaging is demonstrated with high resolution (512 × 512, 48-cm FOV, and 32-cm FOV) spin-echo images of the thoracic and lumbar spine. Data were acquired from four-element linear spine arrays, the first made of 12-cm square coils and the second made of 8-cm square coils. When compared with images from a single 15 × 30-cm rectangular coil and identical imaging parameters, the phased array yields a 2X and 3X higher SNR at the depth of the spine ( ∼ 7 cm). © 1990 Academic Press, Inc.
2,202 citations
Book•
30 Nov 1993
TL;DR: Details of Element Pattern and Mutual Impedance Effects for Phased Arrays and Special Array Feeds for Limited Field of View and Wideband Arrays are presented.
Abstract: Phased Arrays in Radar and Communication Systems. Pattern Characteristics and Synthesis of Linear and Planar Arrays. Patterns of Nonplanar Arrays. Elements, Transmission Lines, and Feed Architectures for Phased Arrays. Summary of Element Pattern and Mutual Impedance Effects. Array Error Effects. Special Array Feeds for Limited Field of View and Wideband Arrays.
2,001 citations
TL;DR: It is shown that the waveform diversity offered by such a MIMO radar system enables significant superiority over its phased-array counterpart, including much improved parameter identifiability, direct applicability of adaptive techniques for parameter estimation, as well as superior flexibility of transmit beampattern designs.
Abstract: We have provided a review of some recent results on the emerging technology of MIMO radar with colocated antennas. We have shown that the waveform diversity offered by such a MIMO radar system enables significant superiority over its phased-array counterpart, including much improved parameter identifiability, direct applicability of adaptive techniques for parameter estimation, as well as superior flexibility of transmit beampattern designs. We hope that this overview of our recent results on the MIMO radar, along with the related results obtained by our colleagues, will stimulate the interest deserved by this topic in both academia and government agencies as well as industry.
1,820 citations
Book•
02 Dec 2009
TL;DR: In this paper, the authors present an overview of the history of connected arrays and their applications in the field of pattern synthesis, and present a detailed analysis of the connections and their properties.
Abstract: Preface to the First Edition. Preface to the Second Edition. 1 Introduction. 1.1 Array Background. 1.2 Systems Factors. 1.3 Annotated Reference Sources. References. 2 Basic Array Characteristics. 2.1 Uniformly Excited Linear Arrays. 2.2 Planar Arrays. 2.3 Beam Steering and Quantization Lobes. 2.4 Directivity. References. 3 Linear Array Pattern Synthesis. 3.1 Introduction. 3.2 Dolph Chebyshev Arrays. 3.3 Taylor One-Parameter Distribution. 3.4 Taylor N-Bar Aperture Distribution. 3.5 Low-Sidelobe Distributions. 3.6 Villeneuve N-Bar Array Distribution. 3.7 Difference Patterns. 3.8 Sidelobe Envelope Shaping. 3.9 Shaped Beam Synthesis. 3.10 Thinned Arrays. Acknowledgment. References. 4 Planar and Circular Array Pattern Synthesis. 4.1 Circular Planar Arrays. 4.2 Noncircular Apertures. Acknowledgment. References. 5 Array Elements. 5.1 Dipoles. 5.2 Waveguide Slots. 5.3 TEM Horns. 5.4 Microstrip Patches and Dipoles. Acknowledgments. References. 6 Array Feeds. 6.1 Series Feeds. 6.2 Shunt (Parallel) Feeds. 6.3 Two-Dimensional Feeds. 6.4 Photonic Feed Systems. 6.5 Systematic Errors. Acknowledgments. References. 7 Mutual Coupling. 7.1 Introduction. 7.2 Fundamentals of Scanning Arrays. 7.3 Spatial Domain Approaches to Mutual Coupling. 7.4 Spectral Domain Approaches. 7.5 Scan Compensation and Blind Angles. Acknowledgment. References. 8 Finite Arrays. 8.1 Methods of Analysis. 8.2 Scan Performance of Small Arrays. 8.3 Finite-by-Infinite Array Gibbsian Model. References. 9 Superdirective Arrays. 9.1 Historical Notes. 9.2 Maximum Array Directivity. 9.3 Constrained Optimization. 9.4 Matching of Superdirective Arrays. References. 10 Multiple-Beam Antennas. 10.1 Introduction. 10.2 Beamformers. 10.3 Low Sidelobes and Beam Interpolation. 10.4 Beam Orthogonality. Acknowledgments. References. 11 Conformal Arrays. 11.1 Scope. 11.2 Ring Arrays. 11.3 Arrays on Cylinders. 11.4 Sector Arrays on Cylinders. 11.5 Arrays on Cones and Spheres. Acknowledgments. References. 12 Connected Arrays. 12.1 History of Connected Arrays. 12.2 Connected Array Principles. 12.3 Connected Dipole Currents. 12.4 Connection by Reactance. 12.5 Connected Array Extensions. References. 13 Reflectarrays and Retrodirective Arrays. 13.1 Reflectarrays. 13.2 Retrodirective Arrays. References. 14 Reflectors with Arrays. 14.1 Focal Plane Arrays. 14.2 Near-Field Electromagnetic Optics. References. 15 Measurements and Tolerances. 15.1 Measurement of Low-Sidelobe Patterns. 15.2 Array Diagnostics. 15.3 Waveguide Simulators. 15.4 Array Tolerances. Acknowledgment. References. Author Index. Subject Index.
1,106 citations
TL;DR: In this paper, the concept of optical phase discontinuities is applied to the design and demonstration of aberration-free planar lenses and axicons, comprising a phased array of ultrathin subwavelength spaced optical antennas.
Abstract: The concept of optical phase discontinuities is applied to the design and demonstration of aberration-free planar lenses and axicons, comprising a phased array of ultrathin subwavelength spaced optical antennas. The lenses and axicons consist of radial distributions of V-shaped nanoantennas that generate respectively spherical wavefronts and non-diffracting Bessel beams at telecom wavelengths. Simulations are also presented to show that our aberration-free designs are applicable to high numerical aperture lenses such as flat microscope objectives.
1,046 citations