Antennas everywhere - from space to undersea - design, optimizations and new techniques for spaceborn, ground based and marine antennas

The present dissertation gathers the most significant researches and achievements of its author in the antenna domain. The text is organised in three main parts that are intended to guide the reader through a theoretical and technological excursus on antennas solutions, from space to undersea. Each part aims at showing the answer to each of the following questions, respectively: How a spaceborne antenna shall be? How a ground-based antenna shall be? How a media penetrating antenna shall be? In the frame of a collaboration with the European Space Research and Technology Centre (ESTEC) of the European Space Agency (ESA), the author has been involved, after completing on site (in The Netherlands) his M.Sc. degree in 2011, in a research on the optimisation of the scanning properties of confocal dual reflector antenna systems for spaceborne applications. As part of his permanent assignment, since 2012, as consultant at the ESA’s European Space Operations Centre (ESOC), Germany, the author is responsible of different sustaining and investment projects on existing and new ground antenna terminals for space missions. Some of the projects are presented in this work. Together with the group of electromagnetism of the University La Sapienza of Rome, the author has treated problems related to the electromagnetic deep penetration of lossy media using deep penetrating new antenna solutions. The text is organized into five chapters. Chapter 1 is an introduction and deals with the historical background of modern antennas technologies and layouts and with the fundamental parameters for the analysis of antenna systems related to space and terrestrial contexts. Chapter 2 presents the major achievements of a study on a dual confocal offset antenna configuration for space applications. In particular the optical aberrations caused by the offset arrangement are analysed in order to validate the system introduced as an interesting solution for compact, light and simple payload antennas. Chapter 3 introduces to the world of ground based antennas and provides some interesting hints on a wide range of ground antenna types. Several designing solutions are proposed with the aim of optimizing the desired available gain for the various applications, from the tracking of a space launcher to the communication with spacecraft at the edge of the solar system. An in-depth study is presented on the upgrade of a radio telescope into a ground terminal for the support of deep space missions, addressing to the required versatility of the antenna layouts and to the sustainability of the ground station environment. In Chapter 4, the possibility of achieving the electromagnetic deep penetration of lossy media is analysed. A new design solution, able to generate inhomogeneous waves, similarly to what performed by leaky wave antennas, is introduced. This layout is of extreme interest for its flexibility and for its potentiality of application, as for instance the deep penetration of seawater. Chapter 5 recaps the conclusions of the entire dissertation showing that the world of antennas is much wider than one may think at first sight and innovative solutions are always behind the corner

Electromagnetic compatibility and interference practical analyses for beam waveguide ground antennas

The Sardinia Radio Telescope (SRT) is currently operated by the Italian astrophysics institute (INAF). Following its upgrade to transmission (TX) capabilities, planned by the Italian Space Agency (ASI) for the commanding of deep space probes, an electromagnetic compatibility (EMC) analysis is performed in order to evaluate the impact on the reception (RX) capabilities currently used by the radio astronomers. Using the same simulation AIDS, an electromagnetic interference (EMI) study is performed with respect to the main auxiliary ground station equipment and in the event of overflying aircrafts. The biological hazard is finally evaluated on human beings

ON THE SCANNING PROPERTIES OF IMAGING ANTENNAS BASED ON DUAL CONFOCAL PARABOLOIDAL REFLECTORS

In this paper the scanning properties of dual reflector antenna systems constituted by two confocal paraboloidal reflectors fed by a planar array are investigated. This antenna architecture combines the interesting features of reflectors and array antennas. Because of the offset configuration the radiation pattern exhibits an anomalous deviation in the beam pointing when the beam is scanned out of the boresight direction. Heuristic equations, representing an extension of the linear equations available in the literature, are derived, which permit predicting the pointing direction of the overall system as a function of the pointing direction of the feeding array in a significant field of view

Launcher Tracking Support from ESTRACK

Launcher tracking support implies vehicle telemetry reception and distribution and is indispensable for flight safety and accurate spacecraft separation. Technical and operational challenges are the uncertainty of launcher trajectory dispersion for acquisition, the high speed pointing target of the launcher, autotrack diversity operations on two different frequencies, synchronous telemetry data reception, real-time telemetry processing and distribution. ESA’s Tracking Station Network (Estrack) was up-graded to support with dedicated stations the tracking of Ariane-5, Soyuz and Vega. Therefore, a new station on the Island of Santa Maria, Azores, Portugal was developed for Ariane-5 mission support and an existing ESA 15m antenna in Perth, West Australia was up-graded even to feature launcher tracking and satellite first acquisition simultaneously. Several launches have been supported successfully since then

Inhomogeneous waves generation for the electromagnetic deep penetration into lossy media

The generation of inhomogeneous electromagnetic waves in a lossless medium is generally associated to leaky-wave antennas. In the present paper it is shownhow such waves can be also easily generated bythe transmission of a homogeneous wave through a dissipative dielectric layer. In particular,a dissipative triangular prisminthe free space, whose first interface is fedby ahomogeneous wave can be employed to generatean inhomogeneous wave emerging atthe second interface. The phase and attenuation vectors obtained are evaluated against the geometry and the material of the prism.The results illustrate a novel approach in generating inhomogeneous waves in lossless media which finds applications for the deep penetration of lossy materials

Generation of inhomogeneous electromagnetic waves by a lossy prism

The generation of inhomogeneous electromagnetic waves in free space is associated to the leaky-wave antennas. On the other hand, in the present paper, we show how an inhomogeneous wave can be also generated by the transmission of a homogeneous wave incident on a dissipative material with a spatial inhomogeneity. In fact, if we consider a dissipative material immersed in free space, with the first interface illuminated by a homogeneous wave, the spatial inhomogeneity gives to the wave different attenuations in the transverse direction; consequently the wave obtains an attenuation component tangential to the second interface, that imply the generation of an inhomogeneous wave in the free space. In particular, we consider a prism made of dissipative material illuminated by a horn tapered antenna. We present the phase and attenuation vectors' magnitudes, and the transmission angle of the inhomogeneous wave. The phase and attenuation vectors showing a strong dependence on the incident angle. Moreover, we found the optic path of the wave inside the prism during multiple reflections, in order to find the positions of the secondary lobs of the antenna. The possibility to generate inhomogeneous waves with strong attenuation finds applications for the deep penetration of electromagnetic waves in lossy materials

TT&C Upgrade of Sardinia Radio Telescope - BWG Optical Design Solutions and EMC with the Radio-Astronomy Receivers

The Sardinia Radio Telescope (SRT) is a fully steerable and versatile 64-m antenna, recently completed in Sardinia, Italy. SRT is currently commissioned by INAF. Following its upgrade to TT&C capabilities financed by ASI, SRT will be able to support communication to/from Deep Space probes. The paper deals with the preliminary analyses done in order to implement a TT&C BWG layout for X-band and Ka-band. The proposed BWG layout is optimized, using GRASP by TICRA, to compensate the beam squint phenomenon, which may occur with critical space missions. Consistent improvements are shown for Ka-band, which represents the most critical case. Moreover, the optical system of mirrors, together with the feeding structures are dimensioned to guarantee the electromagnetic compatibility (EMC) with the Radio-Astronomy instrumentation, for the nominal case and applying a beam squint correction through mechanical rotation of dedicated mirrors. Strategies and solutions, both mechanical and electromagne

The Sardinia Radio Telescope Upgrade to Telemetry, Tracking and Command: Beam Squint and Electromagnetic Compatibility Design

This paper describes the most recent improvements for the upcoming upgrade to telemetry, tracking and command (TT&C) capabilities for the Sardinia Radio Telescope (SRT), a 64-m antenna tailored for radio-astronomical observations of cosmic radio sources located in the outer space. Due to the TT&C improvement, the SRT will represent one of the Europe's main establishments for the support of present and future deep space missions. The first part of this paper is dedicated to the Gaussian Beam synthesis of the SRT feeding system, called beam waveguide, fashioned to maximize the antenna illumination and spillover efficiency. The best design parameters have been retrieved through a rapid and efficient optimization analysis and verified by means of physical optics simulations. In accordance with the obtained results from the Gaussian formulation, further in-depth studies have been undertaken in order to investigate a technique able to overcome the so-called beam squint issue, a typical drawback that occurs during the tracking process of active spacecrafts. The proposed approach manages to automatically attain and quickly the best antenna beam steering strategy to correct the squint issue by means of a field-matching algorithm. Finally, this paper reports the analyses developed for electromagnetic hazard predictions, which shall be carefully taken into consideration for the safety of personnel working close to the high-power radiating installations and for preventing the astronomical receivers located near the Prime and the Gregorian foci from being damaged when the antenna is transmitting