Large antenna arrays and millimeter-wave (mmWave) frequencies have been attracting growing attention as possible candidates to meet the high requirements of future 5G mobile networks. In view of the large path loss attenuation in these bands, beamforming techniques that create a beam in the direction of the user equipment are essential to perform the transmission. For this purpose, in this pape...

If A q (β, α, k) is the scattering amplitude, corresponding to a potential q ∈ L 2 (D), where D ⊂ R 3 is a bounded domain, and e ikα·x is the incident plane wave, then we call the radiation pattern the function A(β) := A q (β, α, k), where the unit vector α, the incident direction, is fixed, and k > 0, the wavenumber, is fixed. It is shown that any function f (β) ∈ L 2 (S 2), where S 2 is the u...

In this paper, grating metal structures with broad and flat back-scattering field patterns are studied for possible applications in a vehicle collision avoidance system. The two-dimensional TE scattering of a planar grating structure and a curved grating structure are analyzed at a frequency of 77 GHz. For the planar structure, the method of moment together with Floquet’s theorem is used to sol...

A novel method for the design of two-dimensional (2-D) and three-dimensional (3-D) arrays with frequency invariant beam patterns is proposed. By suitable substitutions, the beam pattern of a 2-D or 3-D arrays can be regarded as the 3-D or 4-D Fourier transform of its spatial and temporal parameters. Since frequency invariance can be easily imposed in the Fourier domain, a simple design method i...

This paper presents applications of the laser induced shear wave directivity pattern in the thermoelastic regime, to the detection and the in-depth profiling of overthickness and closed cracks perpendicular to the surface. Some results on academic samples and first measurements of actual depth profilings of welds are presented and discussed.

We develope a No Response Test for the reconstruction of some polyhedral obstacle from one or few time-harmonic electromagnetic incident waves in electromagnetics. The basic idea of the test is to probe some region in space with waves which are small on some test domain and, thus, do not generate a response when the scatterer is inside of this test domain. This is the first formulation of the N...

It is shown that any desired radiation pattern f (β) ∈ L 2 (S 2), where S 2 is the unit sphere in R 3 , can be generated by a suitable distribution of small, acoustically soft particles D m ⊂ D, 1 ≤ m ≤ M , in an a priori given bounded domain D ⊂ R 3. In this theory the geometrical shape of a small particle D m is arbitrary, the boundary S m of D m is Lipschitz uniformly with respect to m. The ...

If A q (β, α, k) is the scattering amplitude, corresponding to a potential q ∈ L 2 (D), where D ⊂ R 3 is a bounded domain, and e ikα·x is the incident plane wave, then we call the radiation pattern the function A(β) := A q (β, α, k), where the unit vector α, the incident direction, is fixed, and k > 0, the wavenumber, is fixed. It is shown that any function f (β) ∈ L 2 (S 2), where S 2 is the u...