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In this paper, an alternative approach to design controlled switches at millimeter and sub-millimeter waves, based on coupled tunable Bessel-beam launchers in the radiative near field region, is proposed. In particular, we investigate the possibility of tuning the electromagnetic properties of the radiating apertures through the application of a driving voltage in order to dynamically switch the cover distance of the launchers. Such a controlled switch is intended to work in a bi-stable mode: when the control signal is high (low), the launchers exhibit an efficient (a poor) electromagnetic coupling through the Bessel-beam main lobe. Therefore, the device acts as a switching transistor, i.e., as in digital applications, and also as an opto-isolator at lower frequencies.

Scattering of Bessel beams can be matter of great interest in many practical areas such as near-field radar cross section (RCS) measurement, ground penetrating radar (GPR) and optical microscopy. In this contribution, we explore the advantages of performing inverse scattering through Bessel beams to obtain better results when compared to standard inversion approaches dealt with standard incident fields such as plane waves, current filaments or fields radiated by dipoles/loops in tridimensional imaging. Preliminary numerical assessments are given towards metallic scatterers by exploiting the well-known standard back-propagation technique.

In this paper, we present a simple technique to achieve electronically-controlled beam scanning, by properly acting on the exhibited average surface susceptances placed in correspondence of the sidewalls of a slotted rectangular waveguide. Such an approach allows to avoid the surface susceptance spatial modulation, thus it inherently simplifies the active elements biasing-network design. The preliminary results in the case of a 1D traveling-wave array demonstrates the concept and paves the way for the full development of 2D scanning arrays and for surface reactance synthesis by means of active elements, such as PIN diodes.

In this paper we provide explicit formulas to calculate the phase center location of an arbitrary antenna. Such a formulation allows the description of the phase center dependence from the observation aspect and from the frequency.

In this paper, we deal with the proper definition of the near-field wireless power transfer efficiency between two antennas, by adopting both spatial and spectral approaches to evaluate it. Such a figure of merit allows the evaluation of wireless link performances in the radiating near-field by using RLSA launchers. Numerical results to establish the performances of uniform, zero- th order Bessel, and zero- th order first kind Hankel wireless links are presented. In the final part of the paper, an example of RHCP RLSA Bessel beam launcher at f = 30 GHz implementing a zero-th order, first kind Hankel aperture distribution is proposed as building block for a near-field wireless link, showing that its performances can be considered satisfactory in terms of efficiency, provided that a suitable distance between transmitting/receiving antennas is chosen.

In this paper, an automatic procedure based on physical optics (PO) for the design and optimization of a sectoral pattern shaped reflector at millimeter waves is proposed. As a starting guess for the PO-based iterative procedure, a fast optimization based on geometrical optics (GO) has been developed. In order to preserve the smoothness of the reflector shape, a reduced set of control points on its surface is defined, and an interpolation is performed between them. The results show the effectiveness of the proposed technique, that can profitably find applications in the design of RADAR antennas for surveillance purpose.