The key role of Giovanni Giorgi in developing the MKSA system of units

The International System of units used nowadays in most of the word experienced a turning point in the first half of the XX century with the introduction of the ampere (A) as a fourth unit in addition to the original length (M – meter), mass (K – kilogram) and time (S – second), hence turning from a MKS to a MKSA system. This addition was a non-trivial and lengthy process mainly carried on by the Italian engineer Giovanni Giorgi. This contribution retraces this revolution in the measurement system

The life and work of Giovanni Giorgi. The rationalization of the units of measurement system

This column focuses on Giovanni Giorgi (Figure 1), the Italian scientist who clarified the necessity to augment the existing system of three fundamental units to a fourth electrical one, leading to the International System of Units (SI units) of measurement, now universally accepted. The statement of the physical problem is first briefly recalled. The confusing historical context at the end of the 19th century is examined, and the terms of the problems are clarified. The evolution of the concept of an absolute system, the rationalization of the system and the introduction of a fourth electrical unity, and the contributions of the other scientists before Giorgi (like Carl Friedrich Gauss, Wilhelm Eduard Weber, James Clerk Maxwell, and Oliver Heaviside) are reviewed, and the results of the subsequent various conferences held to organize the matter are considered. Then, Giorgi's intuition and the characteristics of his proposal are described. Finally, some notes about the life and the various scientific and technical activities of Giovanni Giorgi are summarized, showing the contributions given by him in different fields, such as relativity

Phase-Only Synthesis for Large Planar Arrays via Zernike Polynomials and Invasive Weed Optimization

International audienceA synthesis method for the design of large planar array antennas with phase-only control is here presented. The synthesis is based on the use of Zernike polynomials, as global basis function for the phase, to reduce the number of optimization variables with respect to the number of elements of the array. Invasive weed optimization (IWO) is applied to polynomial coefficientsand#x2019; optimization to circumvent non-linearity and local trapping issues typical of phase-only problems. The periodicity of the array factor is exploited to reduce the optimization to a Voronoi cell of the grating-lobesand#x2019; lattice and non-uniform meshing is introduced to best adapt the control stations to the beam shape requirements. The technique is applied to the design of shaped beams for continental coverage from geostationary satellites. IEE

A compact and lightweight ultra-wideband interferometer for direction finding applications

In this work it is proposed the design of a couple of UWB two-arm sinuous antennas working in 2-18 GHz (Antenna A) and 6-18 GHz (Antenna B) frequency bands assembled in a ultra-wideband array for direction finding applications. Both antennas work with a slant 45° polarization ensuring good matching impedance and stable radiation characteristics in the considered frequency bands. The design has been optimized in order to reduce the geometrical dimensions. The proposed antennas have been manufactured and tested in order to validate the simulation performances. Finally the evaluation of accuracy performances in estimating the direction of arrival of an incoming wave-front is presented