The mutual coupling between antenna elements affects the antenna parameters like terminal impedances, reflection coefficients and hence the antenna array performance in terms of radiation characteristics, output signal-to-interference noise ratio (SINR), and radar cross section (RCS). This coupling effect is also known to directly or indirectly influence the steady state and transient response, the resolution capability, interference rejection, and direction-of-arrival (DOA) estimation competence of the array. Researchers have proposed several techniques and designs for optimal performance of phased array in a given signal environment, counteracting the coupling effect. This paper presents a comprehensive review of the methods that model and mitigate the mutual coupling effect for different types of arrays. The parameters that get affected due to the presence of coupling thereby degrading the array performance are discussed. The techniques for optimization of the antenna characteristics in the presence of coupling are also included.
Contents 2.3 EM propagation in multilayered dielectric-metamaterial media 2.3.1 Reflection behaviour for dielectric-metamaterial layers 2.3.2 RF simulation inside a closed rectangular cavity 2.4 Antireflection and high-reflection dielectric/metamaterial coatings 2.4.1 EM propagation in a single slab 2.4.2 EM propagation in a multilayered structure 2.4.3 Antireflection coatings consisting of dielectrics 2.4.4 Antireflection coatings consisting of metamaterials 2.4.5 High-reflection coatings using dielectric and metamaterial 2.5 Conclusion References 3. Radar Cross Section of Phased Antenna Arrays 3.1 Introduction 3.2 Theoretical background 3.2.1 Antenna scattering 3.2.2 Formulation for antenna RCS 3.3 A phased array with a series feed network 76 3.3.1 RCS formulation with isotropic array elements 3.3.2 RCS pattern analysis 3.4 Phased array with parallel feed network 3.4.1 RCS formulation with isotropic array elements 3.4.2 RCS pattern analysis 3.5 Conclusion 122 References 124
Enormous progress has been made during the past five decades in the area of adaptive array processing. Increased computational power has resulted in many practical applications of optimum algorithms. The present paper deals with many facets of array signal processing and adaptive beam forming. It provides a comprehensive description of various beam-forming schemes, adaptive algorithms to adjust the required weighting on antenna elements, direction-of-arrival estimation methods, including their performance comparison. The effects of various types of errors on the performance of an array system are illustrated along with their remedial measures. Since array signal processing has widespread applications, the study is carried out across various disciplines.
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Metasurfaces are ultrathin, two-dimensional structures composed of periodic or quasi-periodic arrays of sub-wavelength scatterers. They possess the unique ability to comprehensively control the phase, amplitude and polarization of incident electromagnetic waves with added advantages such as ease of fabrication and less space consumption. On account of these factors, they are progressively replacing their three-dimensional counterparts, i.e. metamaterials in a wide gamut of fields such as signal multiplexing, stealth technology, holographic imaging, planar optical devices, polarization transformation devices and so on. Further, metasurfaces offer a strong and promising platform for aerospace applications due to their diversified functionalities and reduced weight penalties. Moreover, it has been widely used for the realization of thin, broadband and polarization independent radar absorbing structures (RAS). In this regard, this paper presents a concise review on the recent advancements in the field of metasurfaces specifically for stealth applications. Special emphasis has been laid on diffusion and coding metasurfaces due to their attractive properties towards the realization of low observable platforms. Furthermore, various types of metasurfaces as well as the different techniques used for the optimization of metasurfaces are also described in detail.
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