Giuseppe Di Massa

Antennas for Modern Small Satellites

Modern small satellites (MSS) are revolutionizing the space industry. They can drastically reduce the mission cost, and can make access to space more affordable. The relationship between a modern small satellite and a ldquoconventionalrdquo large satellite is similar to that between a modern compact laptop and a ldquoconventionalrdquo work-station computer. This paper gives an overview of antenna technologies for applications in modern small satellites. First, an introduction to modern small satellites and their structures is presented. This is followed by a description of technical challenges in the antenna designs for modern small satellites, and the interactions between the antenna and modern small satellites. Specific antennas developed for modern small-satellite applications are then explained and discussed. The future development and a conclusion are presented.

A Compact High Gain Antenna for Small Satellite Applications

The development of a circularly-polarized compact high-gain antenna to be used for the European Student Earth Orbiter small satellite mission is described. The antenna is realized stacking two coaxial shorted annular patches and placing the top one at half a wavelength from the lower one. At variance of other similar configurations proposed in the past, the one presented in this paper has several important features which can be extremely useful for application in the space environment. In particular, it can be easily fabricated employing suspended technology and its radiation characteristics are to some extent controllable by opportunely varying the geometry. In the following, a straightforward design procedure will be presented detailing the criteria to optimize top and bottom radiating elements. Both numerical and measured results will show that the proposed design satisfies the specifications and presents characteristics comparable to other larger and heavier solutions usually more difficult to design. Specifically, it will be shown that with this configuration it is possible to obtain gain values higher than 12 dB using ground plane of moderate size and that a further improvement up to 15dB can be obtained employing larger ground planes

NEAR-FIELD TO FAR-FIELD TRANSFORMATION WITH PLANAR SPIRAL SCANNING

A transformation procedure directly computing the antenna far-field pattern from near-field samples acquired on a planar spiral is proposed in this paper. The convolution property of the radiation integral is exploited to efficiently perform the evaluation by taking advantages of the Fast Fourier Transform, without the need of any intermediate interpolation process. Validations on circular arrays of elementary dipoles are presented to show the effectiveness of the method.

Hybrid Array Antenna for Broadband Millimeter-Wave Applications

A hybrid array configuration suitable for wideband millimeter-wave applications is presented in this work. The proposed structure is based on the use of circular waveguide elements electromagnetically coupled trough circular apertures to a stripline distribution network. The adopted excitation mechanism avoids the use of transition components generally reducing the overall antenna efficiency. Simulated and measured results on a Ka-band prototype are discussed to prove the wideband radiation behavior.

An integrated probe for phaseless near-field measurements

A novel approach for phaseless near-field measurements is presented. The squared amplitudes received by two co-planar probes simultaneously scanning a near-field planar surface are used to retrieve the near-field phase information and subsequently to perform the near-field/far-field transformation. The approach is advantageous with respect to both microwave holography and existing phase retrieval techniques, since it does not require any increase in the cost of the measurement facility or in the scan time, so conventional low-cost near-field equipments can be used. The effectiveness of the technique is shown by reporting experimental validations on measurements of a microstrip patch antenna for SAR applications.

POTENTIALITIES OF USRP-BASED SOFTWARE DEFINED RADAR SYSTEMS

Software Deflned Radar is the latest trend in radar development. To handle enhanced radar signal processing techniques, advanced radars need to be able of generating various types of waveforms, such as frequency modulated or phase coded, and to perform multiple functions. The adoption of a Software Deflned Radio system makes easier all these abilities. In this work, the implementation of a Software Deflned Radar system for target tracking using the Universal Software Radio Peripheral platform is discussed. For the flrst time, an experimental characterization in terms of radar application is performed on the latest Universal Software Radio Peripheral NI2920, demonstrating a strongly improved target resolution with respect to the flrst generation platform.

Hybrid Microwave Approach for Phaseless Imaging of Dielectric Targets

A hybrid approach for phaseless imaging of dielectric targets is proposed in this letter. A two-probe measurement strategy with the related phase-retrieval method is adopted in conjunction with an inversion procedure based on an inexact-Newton method to give an efficient and low-cost imaging setup, avoiding the need of multiple acquisition surfaces. A preliminary experimental validation on real input data is presented.

Software-Defined Radar System for Landslides Monitoring

An integrated system for landslides early warning, based on a flexible network architecture and including different sensors, is described to monitoring landslides evolution in critical scenarios. Particular focus is devoted on the experimental assessment of an L-band Software Defined Radar sensor, specifically designed for the application, by discussing the measurement results obtained on a real landslide scenario located on the A3 highway in Calabria (Italy). In particular, a mathematical estimator useful for the proper detection of landslide movements is defined and applied to the measured range profiles, thus demonstrating the usefulness of the proposed radar monitoring approach.

SIMPLIFIED DESIGN FLOW OF QUASI-OPTICAL SLOT AMPLIFIERS

Quasi-optical (QO) techniques have been extensively studied in recent years because of the promise they hold for medium and high power generation at millimeter- and sub-millimeter- wave frequencies, demonstrating higher e-ciency than conventional approaches. In this work a step-by-step ∞ow process is proposed for the design of a slot-based QO amplifler. The proposed design procedure is based on full-wave analysis of the individual building blocks, which are then cascaded to represent the whole system. An experimental assessment is proposed based on the design and on experimental analysis of the behavior of a C-band QO unit cell.

Low-Cost Radars Integrated into a Landslide Early Warning System

Radar activities performed at University of Calabria in the framework of a national project on “Landslides Early Warning” are described in this contribution. After a brief outline of the whole Landslides Early Warning Integrated System, two compact and low-cost radar configurations, the first one based on the adoption of a software radio platform, the second one using a compact Vector Network Analyzer as SFCW scatterometer module, are deeply described. Experimental results are discussed as validation tests to demonstrate the radars range detection capabilities.