Lectures on Cauchy’s Problem in Linear Partial Differential Equations. By J. Hadamard. Pp. viii+316. 15s.net. 1923. (Per Oxford University Press.)

This article presents a historical review of the research carried out on dielectric resonator antennas (DRAs) over the last three decades. Major research activities in each decade are highlighted. The current state of the art of dielectric-resonator-antenna technology is then reviewed. The achievable performance of dielectric resonator antennas designed for compactness, wide impedance bandwidth, low profiles, circular polarization, or high gain are illustrated. The latest developments in dielectric-resonator-antenna arrays and fabrication techniques are also examined.

Dielectric Resonator Antennas: A Historical Review and the Current State of the Art

Aspects of the subject disclosure may include an antenna having a feedline configured to receive a first signal and a second signal. A dielectric antenna body is configured to transmit the first signal as a first free space wireless signal and further configured to transmit the second signal as a first guided electromagnetic wave that is bound to a surface of a transmission medium, wherein the first guided electromagnetic wave propagates along the surface of the transmission medium without requiring an electrical return path. Other embodiments are disclosed.

Dual mode antenna systems and methods for use therewith

A tomographic time-domain reconstruction algorithm for solving the inverse electromagnetic problem is described. The application we have in mind is dielectric breast cancer detection but the results are of general interest to the field of microwave tomography. Reconstructions have been made from experimental and numerically simulated data for objects of different sizes in order to investigate the relation between the spectral content of the illuminating pulse and the quality of the reconstructed image. We have found that the spectral content is crucial for a successful reconstruction. The work has further shown that when imaging objects with different scale lengths it is an advantage to use a multiple step procedure. Low frequency content in the pulse is used to image the large structures and the reconstruction process then proceed by using higher frequency data to resolve small scale lengths. Good agreement between the results obtained from experimental data and simulated data has been achieved

Reconstruction Quality and Spectral Content of an Electromagnetic Time-Domain Inversion Algorithm

A novel dielectric resonator antenna design is presented for wideband applications in this letter. By using a dielectric resonator with an optimized H-shaped across section and an optimized trapezoidal patch adhered on the concave surface of the resonator as a feeding mechanism, an impedance bandwidth of about 62% (for VSWR les 2) , covering the frequency range of 3.6-6.85 GHz, is achieved. The measured results in terms of bandwidth and radiation pattern agree well with the simulated ones, confirming the theoretical design.

H-Shaped Dielectric Resonator Antenna for Wideband Applications

The letter proposes a novel cylindrical dielectric resonator antenna (DRA) geometry with low radiation Q-value facilitating wide band operation with conical radiation patterns. The DRA is fed by a microstrip transmission line with a vertical strip that is attached to the DRA surface. At optimum dimensions and position of the vertical strip on the horizontal microstrip, the DRA exhibits an impedance bandwidth ( $\vert {\rm S}_{11}\vert

A Wideband Conical Beam Cylindrical Dielectric Resonator Antenna

A coaxial-fed hexagonal dielectric resonator antenna (HDRA) producing circular polarization is investigated experimentally. Circular polarization is achieved by exciting the orthogonal HE11δ modes of the HDRA in phase quadrature. The return-loss, impedance, and radiation characteristics are studied. The results show that the antenna produces circular polarization in the elevation plane with an axial ratio less than 3 dB over a bandwidth of 14.84% and a beam width of 66°. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 581–582 2006; Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/mop.21413

Coaxial fed hexagonal dielectric resonator antenna for circular polarization

The paper presents an experimental investigation of a cylindrical dielectric resonator antenna (DRA) with a conducting strip loaded on its top surface enabling circular polarisation. A simple 50Ω microstrip transmission line excites the antenna. The reflection, polarisation, and radiation characteristics of the antenna are studied. The antenna exhibits circular polarisation with an axial ratio (AR) < 3 dB over a bandwidth of 3.14% and a beam width of 60°

A strip loaded dielectric resonator antenna for circular polarisation

Microwave technology plays a key role in diagnostic and therapeutic medicine. This paper presents a comprehensive study of dielectric properties of urine collected at different intervals of time at microwave frequencies. Measurement is done using cavity perturbation technique at the S-band of microwave frequency. Urine samples are collected from normal as well as persons with diabetes mellitus and the reported results provide an alternative in-vitro method of diagnosing diabetes mellitus. The same samples are subjected to investigations in the clinical laboratory for quantitative analysis. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 500–503, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20349

Dielectric properties of human urine at microwave frequencies

A novel technique for localizing the scatterer in microwave imaging of two-dimensional circularly symmetric dielectric scatterers using degree of symmetry and neural networks is presented. The degree of symmetry for a transmitter position is computed as a function of the difference between the first half and the spatially reflected second half of the measured scattered field vector. A Probabilistic Neural Network (PNN) classifier is trained with the degree of symmetry vectors for the different object configurations. It classifies the degree of symmetry vector of the unknown circularly symmetric scatterer presented to it into one of the classes that indicate the radius and location of the centre of the scatterer. Thus the scatterer is localized in the imaging domain. This not only reduces the degrees of freedom in the inversion for the unknown object, thereby aiding the global convergence of the solution, but also results in a reduction in computation time. The technique has been tested on synthetic data and the results are promising.

A Novel Technique for Localizing the Scatterer in Inverse Profiling of Two Dimensional Circularly Symmetric Dielectric Scatterers Using Degree of Symmetry and Neural Networks

K. T. Mathew

Papers

A Wideband Conical Beam Cylindrical Dielectric Resonator Antenna

Coaxial fed hexagonal dielectric resonator antenna for circular polarization

A strip loaded dielectric resonator antenna for circular polarisation

Dielectric properties of human urine at microwave frequencies

A Novel Technique for Localizing the Scatterer in Inverse Profiling of Two Dimensional Circularly Symmetric Dielectric Scatterers Using Degree of Symmetry and Neural Networks