Magneto-Electric Dipole Antenna Arrays

A planar magneto-electric (ME) dipole antenna array is proposed and demonstrated by both full-wave analysis and experiments. The proposed structure leverages the infinite wavelength propagation characteristic of composite right/left-handed (CRLH) transmission lines to form high-gain magnetic radiators combined with radial conventional electric radiators, where the overall structure is excited by a single differential feed. The traveling-wave type nature of the proposed ME-dipole antenna enables the formation of directive arrays with high-gain characteristics and scanning capability. Peak gains of 10.84 dB and 5.73 dB are demonstrated for the electric dipole and magnetic-dipole radiation components, respectively.Comment: 9 pages, 17 figure

Performance of hemielliptic dielectric lens antennas with optimal edge illumination

The role of edge illumination in the performance of compact-size dielectric lens antennas (DLAs) is studied in accurate manner using a highly efficient algorithm based on the combination of the Muller boundary integral equations and the method of analytical regularization. The analysis accounts for the finite size of the lens and directive nature of the primary feed placed close to the center of the lens base. The problem is solved in a two-dimensional formulation for both E- and H-polarizations. It is found that away from internal resonances that spoil the radiation characteristics of DLAs made of dense materials, the edge illumination has primary importance. The proper choice of this parameter helps maximize DLA directivity, and its optimal value depends on the lens material and feed polarization. Index Terms: Beam collimation, dielectric lens antenna, directivity improvement, edge illumination, edge taper, hemielliptic lens.Comment: 5 pages, 9 figure

Maximum Gain, Effective Area, and Directivity

Fundamental bounds on antenna gain are found via convex optimization of the current density in a prescribed region. Various constraints are considered, including self-resonance and only partial control of the current distribution. Derived formulas are valid for arbitrarily shaped radiators of a given conductivity. All the optimization tasks are reduced to eigenvalue problems, which are solved efficiently. The second part of the paper deals with superdirectivity and its associated minimal costs in efficiency and Q-factor. The paper is accompanied with a series of examples practically demonstrating the relevance of the theoretical framework and entirely spanning wide range of material parameters and electrical sizes used in antenna technology. Presented results are analyzed from a perspective of effectively radiating modes. In contrast to a common approach utilizing spherical modes, the radiating modes of a given body are directly evaluated and analyzed here. All crucial mathematical steps are reviewed in the appendices, including a series of important subroutines to be considered making it possible to reduce the computational burden associated with the evaluation of electrically large structures and structures of high conductivity.Comment: 12 pages, 15 figures, submitted to TA

Political Broadside Ballads in Seventeenth-Century England: A Critical Bibliography (Pickering and Chatto: London, 2011)

Ballads on ‘affairs of state’ have been largely eschewed by scholars of popular political history, despite the growing digital availability of ballad literature. McShane’s extensive critical bibliography makes these texts accessible for the first time by providing a systematically and rigorously researched bibliography of all recorded and published broadside ballads on affairs of state between the outbreak of the Bishops’ Wars in 1639 to the Glorious Revolution in 1688. Based on comprehensive research into all the major holdings in the UK and USA, the bibliography locates, dates and fully indexes more than 3,100 ballad sheets. McShane, an authority on English print culture, also provides a 10,000-word introduction based on this original research. It sets out the history of printing background of the genre; the importance of typographical and material analysis in helping to understand the broadside as a marketed medium; and the significance of its collecting history to any notion of the ballad as representative of popular political mentalites. A reviewer notes, ‘this comprehensive bibliographic survey, which often corrects previous errors on dating and in its notes offers invaluable contextual information, will open up new research pathways’ (English Historical Review, 2013). McShane has been invited to speak on this research on numerous occasions, including Reading University’s Early Modern Research Centre Colloquium, ‘Printed Image and Decorative Print, 1500–1750′ (2013); the 8th Bildlore Congress, Bassano, Italy (2012); for the international panel on Popular Culture and Media Diversity at the ESSHC Conference, Glasgow University (2012); the ‘Popular Music Participation and the People’ symposium, Goldsmiths (2012); and Leeds University ‘Text and Orality’ research seminar (2011). She is currently a consultant to the JISC-funded Integrating Broadside Ballad Archives project, Bodleian Library (2011–13), and the Popularisation and Media Strategies 1700–1900 project, Utrecht University, funded by the Netherlands Organisation for Scientific Research (2010–14)

A Large Along-Track Baseline Approach for Ground Moving Target Indication Using TanDEM-X

In the paper a new method for ground moving target indication (GMTI) using two satellites (i.e. the TerraSAR-X and the TanDEM-X satellite) together is presented. The along-track baseline between the satellites is chosen to be in the order of several kilometres, so that each satellite observes the same moving vehicles at different times in the order of one to several seconds. The proposed method allows the estimation of the ground velocity of the moving targets as well as the estimation of the broadside positions without the need of complex bistatic processing techniques

Pencil-Beam Single-point-fed Dirac Leaky-Wave Antenna on a Transmission-Line Grid

Leaky-wave antennas (LWAs) are widely used as single-point-fed linear antenna arrays. The extension of LWAs to 2D implies that they can be used as single-point-fed 2D antenna arrays without requiring a complex feeding network. However, generating a pencil beam from 2D LWAs is not straightforward and due care has to be taken for the design of the LWA. On the other hand, transmission-line (TL) grids have demonstrated interesting behaviors, such as an effective negative refractive index and growing of evanescent waves. In this paper, a singlepoint-fed TL-grid 2D Dirac leaky-wave antenna (DLWA) design is proposed that generates a pencil beam at both broadside and slightly tilted angles. The TL-grid unit cell is analytically treated in light of its scattering and impedance matrices. The optimized TL-grid unit cell is shown to exhibit a closed bandgap in the dispersion relation which is also linearly varying with frequency (hence it is a DLWA). The proposed 2D DLWA design is fabricated and the experimental results are presented

Frequency invariant beamforming for two-dimensional and three-dimensional arrays

A novel method for the design of two-dimensional (2-D) and three-dimensional (3-D)arrays with frequency invariant beam patterns is proposed. By suitable substitu- tions, the beam pattern of a 2-D or 3-D arrays can be regarded as the 3-D or 4-D Fourier transform of its spatial and temporal parameters. Since frequency invariance can be easily imposed in the Fourier domain, a simple design method is derived. Design examples for the 2-D case are provided