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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.