Anisotropic artificial substrates for microwave applications

The perfect electromagnetic conductor (PEMC) boundary is a novel fundamental electromagnetic concept. It is a generalized description of the electromagnetic boundary conditions including the perfect electric conductor (PEC) and the perfect magnetic conductor (PMC) and due to its fundamental properties, it has the potential of enabling several electromagnetic applications. However, the PEMC boundaries concept had remained at the theoretical level and has not been practically realized. Therefore, motivated by the importance of this electromagnetic fundamental concept and its potential applications, the first contribution of this thesis is focused on the practical implementation of the PEMC boundaries by exploiting Faraday rotation principle and ground reflection in the ferrite materials which are intrinsically anisotropic. As a result, this thesis reports the first practical approach for the realization of PEMC boundaries. A generalized scattering matrix (GSM) is used for the analysis of the grounded-ferrite PEMC boundaries structure. As an application of the PEMC boundaries, a transverse electromagnetic (TEM) waveguide is experimentally demonstrated using grounded ferrite PMC (as particular case of the PEMC boundaries) side walls. Perfect electromagnetic conductor boundaries may find applications in various types of sensors, reflectors, polarization convertors and polarization-based radio frequency identifiers.;Leaky-wave antennas perform as high directivity and frequency beam scanning antennas and as a result they enable applications in radar, point-to-point communications and MIMO systems. The second contribution of this thesis is introducing and analysing a novel broadband and highly directive two-dimensional leaky-wave antenna. This antenna operates differently in the lower and higher frequency ranges. Toward its lower frequencies, it allows full-space conical-beam scanning while at higher frequencies, it provides fixed-beam radiation (at a designable angle) with very low-beam squint, which makes it particularly appropriate for applications in wide band point-to-point communication and radar systems. The antenna is constituted of a mushroom type anisotropic magneto-dielectric artificial grounded slab with uniaxially anisotropic permittivity and permeability tensors. A spectral transmission-line model based on Green functions approach is chosen for the analysis of the structure. A rigorous comparison between the isotropic and anisotropic leaky-wave antennas is performed which reveals that as opposed to anisotropic slabs, isotropic slabs show weak performance in leaky-wave antennas.;The properties of planar antennas such as low profile, low cost, compatibility with integrated circuits and their conformal nature have made them appropriate antennas for communications systems. In parallel, bandwidth and miniaturization requirements have increased the demand for millimeter-wave wireless systems, such as radar, remote sensors and highspeed local area networks. However, as frequency increases towards millimeter-wave regime, the radiation efficiency of planar antennas becomes an important issue. This is due to the increased electrical thickness of the substrate and therefore increased number of the excited surface modes which carry part of the energy of the system in the substrate without any efficient contribution to radiation. Therefore, these antennas suffer from low radiation efficiency. This has motivated the third contribution of the thesis which is the interpretation and analysis of the radiation efficiency behavior of the planar antennas on electrically thick substrates. A novel substrate dipole approach is introduced for the explanation of the efficiency behavior. This dipole models the substrate and reduces the problem of the horizontal electric source on the substrate to an equivalent dipole radiating in the free-space. In addition, in this work, some efficiency enhancement solutions at the electrical thicknesses where the radiation efficiency is minimal are provided. Following the obtained knowledge about the radiation efficiency behavior of the planar antennas printed on the isotropic (conventional) substrates, finally, the effect of the anisotropy of the substrate on the planar antenna radiation efficiency is studied. (Abstract shortened by UMI.).