The eleven antenna: a compact low-profile decade bandwidth dual polarized feed for reflector antennas

A novel dual polarized ultrawide-band (UWB) feed with a decade bandwidth is presented for use in both single and dual reflector antennas. The feed has nearly constant beam width and 11 dBi directivity over at least a decade bandwidth. The feed gives an aperture efficiency of the reflector of 66% or better over a decade bandwidth when the subtended angle toward the sub or main reflector is about 53°, and an overall efficiency better than 47% including mismatch. The return loss is better than 5 dB over a decade bandwidth. The calculated results have been verified with measurements on a linearly polarized lab model. The feed has no balun as it is intended to be integrated with an active 180° balun and receiver. The feed is referred to as the Eleven antenna because its basic configuration is two parallel dipoles 0.5 wavelengths apart and because it can be used over more than a decade bandwidth with 11 dBi directivity. We also believe that 11 dB return loss is achievable in the near future

Tomorrow's Metamaterials: Manipulation of Electromagnetic Waves in Space, Time and Spacetime

Metamaterials represent one of the most vibrant fields of modern science and technology. They are generally dispersive structures in the direct and reciprocal space and time domains. Upon this consideration, I overview here a number of metamaterial innovations developed by colleagues and myself in the holistic framework of space and time dispersion engineering. Moreover, I provide some thoughts regarding the future perspectives of the area

Disseny i mesura de teixits apantallants / antiradiació electromagnètica per a protecció

In recent years several studies regarding metamaterials have been carried out. The possibility of reaching new properties further from the ones offered by conventional materials has opened new ways of study. Among the different fields of investigation in which metamaterials and frequency selective surfaces are involved, applying them on fabrics and creating wearable structures is one of the newest, and still few investigation has been done on it since, although its potential applications, it is still difficult to reach good results. For this reason, and in order to prove that this is an important field in which very interesting results can be obtained by means of conventional procedures, in this thesis a FSS based on fabric and conductive thread is designed. To do so, the first step is to optimize the geometry using computer simulations until reaching the desired electromagnetic properties. Once done that, the designed unit cell is applied in a larger surface, which is tested and the obtained results compared to the ones given by the simulation. By doing this, it is proved that, although the final crafted surface is not exactly the same that the designed one because of the imperfections inherent in any construction process the properties reached are almost the same, offering similar levels of absorption and a small shift of frequency. Since the surface tested in this thesis is relatively small, testing bigger surfaces in order to better approximate the infinite extension hypothesis and improve the construction process are the logical steps to follow in order to improve a technology which has already been proved to be useful, possible and within reach

Radio measurements for determining the energy scale of cosmic rays

This work is about Tunka-Rex, a radio detector for air showers in Siberia. After calibrating the detector and developing a reconstruction method for air shower events, three results are presented, obtained from the 2012-2014 data of Tunka-Rex: - a method for measuring the energy with a single antenna station. - a validation of the CoREAS code for simulation of radio emission. - a comparison of dofferent experiments\u27s energy scales via the radio signal

A New Wideband, Fully Steerable, Decametric Array at Clark Lake

A fully steerable, decametric array for radio astronomy is under construction at the Clark Lake Radio Observatory near Borrego Springs, California. This array will be a T of 720 conical spiral antennas (teepee-shaped antennas, hence the array is called the TPT), 3.0 km by 1.8 km capable of operating between 15 and 125 MHz. Both its operating frequency and beam position will be adjustable in less than one millisecond, and the TPT will provide a 49-element picture around the central beam position for extended source observations. Considerable experience was gained in the operation of completed portions of the array, and successful operation of the final array is assured. The results are described of the tests which were conducted with the conical spirals, and the planned electronics and data processing systems are described

Characteristic Functions Describing the Power Absorption Response of Periodic Structures to Partially Coherent Fields

Many new types of sensing or imaging surfaces are based on periodic thin films. It is explained how the response of those surfaces to partially coherent fields can be fully characterized by a set of functions in the wavenumber spectrum domain. The theory is developed here for the case of 2D absorbers with TE illumination and arbitrary material properties in the plane of the problem, except for the resistivity which is assumed isotropic. Sum and difference coordinates in both spatial and spectral domains are conveniently used to represent the characteristic functions, which are specialized here to the case of periodic structures. Those functions can be either computed or obtained experimentally. Simulations rely on solvers based on periodic-boundary conditions, while experiments correspond to Energy Absorption Interferometry (EAI), already described in the literature. We derive rules for the convergence of the representation versus the number of characteristic functions used, as well as for the sampling to be considered in EAI experiments. Numerical examples are given for the case of absorbing strips printed on a semi-infinite substrate.Comment: Submitted to JOSA

Passive Components for Ultra-Wide Band (UWB) Applications

UWB technology brings the convenience and mobility of wireless communications to very high-speed interconnects in the home and office due to the precision capabilities combined with the low power. This makes it ideal for certain radio frequency sensitive environments such as hospitals and healthcare as well as radars. UWB intrusion-detection radar is used for detecting through the wall and also used for security with fuse avoidance radar, precision locating and tracking (using distance measurements between radios), and precision time-of-arrival-based localization approaches. The FCC issued a ruling in 2002 that allowed intentional UWB emissions in the frequency range between 3.1 and 10.6 GHz, subject to certain restrictions for the emission power spectrum. Other definitions for ultra-wideband range of frequency are also used such as any device that has 500 MHz bandwidth or fractional bandwidth greater than 25% is considered an UWB enable high data rate to be transferred with a very low power that does not exceed −41.3 dBm