Wide angle impedance matching metamaterials for waveguide-fed phased-array antennas

Abstract

This work investigates the gains realisable through the use of artificially structured materials, otherwise known as metamaterials, in the wide angle impedance matching (WAIM) of waveguide-fed phased-array antennas. The authors propose that the anisotropic properties of a metamaterial layer, when designed appropriately, can be employed to achieve impedance matching at a wide contiguous range of phased-array antenna transmission angles. Simulation and numerical results show that an optimised impedance match over a broad angular range can be readily achieved using a doubly uniaxial (magnetic and electric) anisotropic layer, an outcome not found accomplishable when an optimised isotropic dielectric layer is used. The authors propose the possibility of using metamaterials to achieve anisotropic WAIM layer configurations, and the authors show, using two simple uniaxial designs, that a metamaterial layer over the phased-array gives performance characteristics similar to its homogeneous anisotropic effective medium counterpart.

The Role of Substrate Elastic Modulus in the Strain-Dependent Behavior of Electromagnetic Metamaterials: Analytic Description, Multiphysics Modeling, and Test Results

“…These previous studies imparted the simplifying assumption that the stiffness (Elastic/Young's modulus) of the substrate was on the order of the stiffness of the conductive traces (in this case, copper). This assumption is valid for a wide range of envisioned metamaterial implementations, particularly those where the metamaterial will be integrated directly into a load-bearing structure [13,14,15] This simplification imparts a near uniform in-plane strainprofile throughout the metamaterial unit cell (E ij ≈ ∈ ij ); i.e. the differential term for the in-plane mechanical strain is constant throughout the unit cell, and identical to the global value.…”

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

“…Due to their birefringent behaviour, homogeneous anistropic layers can be exploited to match the angular dependence of the active impedance of phased arrays, giving further degrees of freedom in the WAIM layers design [7][8][9]. The definition of proper constraints and cost-function, is essential for the design of anisotropic WAIM layers.…”

“…The definition of proper constraints and cost-function, is essential for the design of anisotropic WAIM layers. Previous works on the topic have dealt either with only dielectric anisotropic material models [8,9] or, although presenting ideal cases of dielectric-magnetic MM, with final MM structures that exhibit only a dielectric behaviour [7]. The aim of this paper is to present a design approach for MM-WAIM structures based on requirements in terms of angular coverage and bandwidth, highlighting the issues and the limits in the realization of MMs.…”

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.…”