Diamagneto-Dielectric Anisotropic Wide Angle Impedance Matching Layers for Active Phased Arrays

Abstract

Abstract-In this paper, we present the full process of designing anisotropic metamaterial (MM) wide angle impedance matching (WAIM) layers. These layers are used to reduce the scan losses that occur in active phased arrays for large scanning angles. Numerical results are provided to show the improvement in performances that such layers can ensure. The proposed anisotropic MM-WAIM layers achieve an improvement of about 1 dB of more radiated power at θ = 70 • from broadside, in a 13% of fractional bandwidth on the azimuthal plane φ = 90 • . Weaker improvements are obtained in the other azimuthal planes, however keeping the active reflection coefficient below −9 dB for all azimuthal planes up to θ = 60 • and up to θ = 70 • off-axis for planes φ = 45 • , 90 • in the whole operational band.

A theoretical investigation on reciprocity-inspired wide-angle spectrally-selective THz absorbers augmented by anisotropic metamaterials

“…In this fashion, the EM properties of the anisotropic layer, i.e. the wave impedance and normal component of the wave vector, can be written as 47 Moreover, the addition of the anisotropic layer also re-defines Eq. (6) considering the multiple reflections occurring between the nearby interfaces 49 in which…”

“…The equivalent tensor parameters of the multilayer dielectric system are retrieved in the absence of the array of dipole resonators. This is a common practice in analyzing the anisotropic superstrates loading a periodic array 47 . Based on the effective medium theory 57,58 , the equivalent tensor components of the dielectric permittivity can be derived as Table 1 for incident angles θ ranging from 0° to 90° in (a) ϕ = 0 and (b) ϕ = 90 planes.…”

“…Here, a combined version of the wide-angle matching layer in phased-array antennas 47 , and reciprocity theorem 48 from classical electromagnetics is theoretically established to address a spectrally selective semiomnidirectional THz absorber. We will serve magneto-electric anisotropy as an additional degree of freedom to provide the required wave-absorber impedance matching at near grazing angles.…”

Experimental demonstration of metamaterials application for mitigating scan blindness in phased array antennas

“…They have been proposed for multiple antenna applications such as enhanced gain superstrates [8], to reduce the coupling between antenna elements [9], or to enhance the efficiency of electrically small antennas [10] to name a few. More recently, metamaterial inspired anisotropic WAIMs have been theoretically proposed for an array of open-ended waveguides antennas [11] and for improving the performance at large scanning angles for a phased array antenna [12]. In both cases, the WAIM was designed in absence of extreme impedance conditions (grating lobes) which permits the matching for the targeted scanning angles while keeping other directions and cardinal planes unaltered.…”

“…A solution similar to the one proposed in [11,12] is considered here, with the additional difficulty that the onset of a grating lobe lies within our region of interest introducing a pronounced impedance mismatch between the antenna and the free-space. In our case of study, the presence of grating lobes gives rise to a very steep impedance profile hindering the matching within a wide frequency band and operation angle.…”