Numerical Results for the System Noise Temperature of an Aperture Array Tile and Comparison with Measurements

The purpose of this report is to document the noise performance of a complex beamforming array antenna system and to characterize the recently developed noise measurement facility called THACO, which was developed at ASTRON. The receiver system includes the array antenna of strongly coupled 144 TSA elements, 144 Low Noise Amplifiers (LNAs) (Tmin =35-40K) and the data recording/storing facilities of the initial test station that allow for off-line digital beamforming. The primary goal of this study is to compare the measured receiver noise temperatures with the simulated values for several practical beamformers, and to predict the associated receiver noise coupling contribution, antenna thermal noise and ground noise pick-up (due to the back radiation).Comment: ASTRON repor

Aperiodic Array Synthesis for Multi-User MIMO Applications

This paper demonstrates the advantages of aperiodic arrays in multi-user multiple-input multiple-output systems for future mobile communication applications. We propose a novel aperiodic array synthesis method which account for the statistics of the propagation channel and the adaptive beamforming algorithm. Clear performance gains in line-of-sight dominated propagation environments are achieved in terms of the signal-to-interference-plus-noise ratio, the sum rate capacity, as well as the spread of the amplifier output power as compared to their regular counterparts. We also show that the performance is not sacrificed in rich scattering environments. Hence, aperiodic array layouts can provide performance gains in millimeter-wave applications with a dominating line-of-sight component.Comment: Manuscript submitted to IEEE Trans. Antennas Propag. on March 18, 2017; published and defended as part of the PhD dissertation Aperiodic Array Synthesis for Telecommunications on May 31, 2017, Goteborg, Sweden, candidate: Carlo Bencivenni, Chalmers University of Technology, faculty opponent: Andrea Massa, ELEDIA cente

Conceptualization of the experience of the individual in the educational space in the light of scientific rationality as a problem of professional identity in global and sociocultural dynamics

As a problem, professional identity associated with the educational space is investigated from the position of belonging to professional groups. The contradictory state of education in the modern world actualizes the problem of identity in the educational space from the perspective of classical modern European rationality with its focus on the scientific forms of cognition, knowledge. The current situation in the world educational space is developed in the ambiguity of the idea of the world, which is expressed in the crisis of universalism and cognitive integrity: the place of rational knowledge in culture is replaced by mythic ideas. The way of thinking exists independently of the individual. The transfer of thinking is a learning task. However, at the present stage, with a sharp increase in the amount of information reported, the emphasis is on formalizing of the educational process, rather than constructivizing. The teacher’s responsibility as a carrier of scientific rationality, which primarily defines the universal meaning of human activity in the transmission of social experience and knowledge, is growing. The level of education of a person is a measure of implementation of the possibility of his/her formation, taking into account the dichotomous nature of the individual's socialization and professional identity based on it. Such a holistic perception of the world will allow gaining a deep understanding of the essence of things, fitting science into the cultural context of modernity

A System-Performance-Based Comparison of Sparse Regular and Irregular Antenna Arrays for Millimeter-Wave Multi-User MIMO Base Stations

A system-level study was conducted that evaluated the system performance of various dense and sparse antenna array configurations for application in millimeter-wave multi-user multiple-input multiple-output base stations. The performance was evaluated by investigating the probability that a user experiences an outage when a zero-forcing pre-coder is used in a random line of sight scenario. This paper shows that the outage probability significantly decreased when irregular sparse arrays were used rather than regular sparse or regular dense arrays. A re-configurable linear array was designed and realized as a demonstrator. It used 3D-printed aluminum box horn antenna elements that had wide scanning range in the azimuthal plane and a small scanning range in the elevation plane. For the demonstrator, it was shown that the outage probability was reduced from 3.85% to 0.64% by moving from a sparse regularly spaced array to a sparse randomly spaced array. This amounted to an improvement of a factor of six. The sparse topology allowed for the usage of large antenna elements that had an increased gain and still achieved wide-angle scanning, while reducing mutual coupling to a minimum

The concept of violence in the philosophy of Aristotle

The idea that the concept of 'violence' was part and is still viewed as part of a broad philosophical category may seem strange. However, the problem is resolved by referring to the concept of 'force,' which is lost in modern philosophy. The exception was the works in which we find some “traces” of this concept, including the works of Aristotle, which need to be free from modernizing interpretation

Wide bandwidth integrated 1-4 GHz feed development for VLBI and SKA

Wide-band single pixel feeds such as the wide-band Eleven feed developed in Europe through Onsala Space Observatory/Chalmers are rapidly increasing in maturity. Compared to the traditional octave bandwidth feeds, wide bandwidth feeds, such as the Eleven feed, will create the possibility of significantly larger instantaneous frequency coverage observations with existing radio telescopes, such as those used in the VLBI networks, and for future radio telescopes, such as the Square Kilometre Array. This Project is supported by RadioNet3, Developments In VLBI Astronomy (DIVA)

An Axi-Symmetric Segmented Composite SKA Dish Design: Performance and Production Analysis

A concept of an axi-symmetric dish as antenna reflector for the next generation radio telescope - the Square Kilometre Array (SKA) - is presented. The reflector is based on the use of novel thermoplastic composite material (reinforced with carbon fibre) in the context of the telescope design with wide band single pixel feeds. The baseline of this design represents an array of 100's to 1000's reflector antennas of 15-m diameter and covers frequencies from <1 to 10 GHz. The purpose of our study is the analysis of the production cost of the dish and its performance in combination with a realistic wideband feed (such as the 'Eleven Antenna' feed) over a wide frequency band and a range of elevation angles. The presented initial simulation results inidicate the potential of the proposed dish concept for low-cost and mass production and demonstrate sensitivity comparable to that of the presently considered off-set Gregorian reflector antenna with the same projected aperture area. We expect this observation to be independent of the choice of the feed, as several other single-pixel wideband feeds (that have been reported in the literature) have similar beamwidth and phase center location, both being rather constant with frequency.Comment: Invited paper for the Asia-Pacific Microwave Conference 2011 (APMC 2011), Melbourne, 5-8 Dec., Australia, 201

APERTIF, a focal plane array for the WSRT

In this paper we describe a focal plane array (FPA) prototype, based on Vivaldi elements, developed for the Westerbork Synthesis Radio Telescope (WSRT) to increase its instantaneous field of view by a factor 25 and double its current bandwidth. This prototype is the first step in a project that has the ambition to equip most of the WSRT antennas with FPAs to improve the survey speed of the telescope. Examples of scientific applications are surveys of the northern sky in polarised continuum and HI emission, and efficient searches for pulsars and transients.Comment: 7 pages, 6 figures. Presented at "The Evolution of Galaxies through the Neutral Hydrogen Window", Feb 1-3, 2008, Arecibo Observatory, Puerto Rico. High resolution versions of figures available in jpg-forma

Innovative Multi-Feed-Per-Beam Reflector Antenna for Space-Borne Conical-Scan Radiometers

We present an antenna for use on conical-scan space-borne radiometers in C band and demonstrate that stringent radiometric requirements can be met. The antenna consists of a 5 m offset reflector fed by a focal plane array in a multi-feed-per-beam configuration, so far never used in ocean observation missions. We use distinct element beams and two optimization routines for obtaining element excitation amplitudes and phases, and with either routine, and in both x- and y-polarization, compliant beams, with footprint &lt; 20 km, distance to coast &lt; 20 km and accuracy &lt; 0:25 K, are obtained. These results may pave the way for use of focal plane arrays with digital beamforming in future radiometric ocean observation missions