Stanislav I. Maslovski

On artificial magnetodielectric loading for improving the impedance bandwidth properties of microstrip antennas

The effect of artificial magnetodielectric substrates on the impedance bandwidth properties of microstrip antennas is discussed. We review the results found in the literature and then focus on practically realizable artificial magnetic media operating in the microwave regime. Next, a realistic dispersive behavior of a practically realizable artificial substrate is embedded into the model. It is shown that frequency dispersion of the substrate plays a very important role in the impedance bandwidth characteristics of the loaded antenna. The impedance bandwidths of reduced size patch antennas loaded with dispersive magnetodielectric substrates and high-permittivity substrates are compared. It is shown that unlike substrates with dispersion-free permeability, practically realizable artificial substrates with dispersive magnetic permeability are not advantageous in antenna miniaturization. This conclusion is experimentally validated.

Modeling of isotropic backward-wave materials composed of resonant spheres

A possible realization of isotropic artificial backward-wave materials is theoretically analyzed. An improved mixing rule for the effective permittivity of a composite material consisting of two sets of resonant dielectric spheres in a homogeneous background is presented. The equations are validated using the Mie theory and numerical simulations. The effect of a statistical distribution of sphere sizes on the increase of losses in the operating frequency band is discussed and some examples are shown.

A Stepwise Nicolson–Ross–Weir-Based Material Parameter Extraction Method

Approaches of automated evaluation of electromagnetic material parameters have received a lot of attention in the literature. Among others, one method is to retrieve the material parameters from the reflection and transmission measurements of the sample material. Compared to other methods, this is a rather wideband method, but suffers from an intrinsic limitation related to the electrical thickness of the measured material. In this letter, we propose a novel way to overcome this limitation. Although being based on the classical Nicolson-Ross-Weir (NRW) technique, the proposed extraction technique does not involve any branch seeking and is therefore capable of extracting material parameters from samples thicker than λ/2, a measure that would otherwise cause problems in the NRW extraction technique. The proposed derivative of the NRW extraction technique is then used to study the effect of thermal noise on the extracted material parameters.

ARTIFICIAL MAGNETIC MATERIALS BASED ON THE NEW MAGNETIC PARTICLE: METASOLENOID

New possibilities to design artificial magnetic materials for microwave frequencies are considered. Such composites can be used in microwave engineering at frequencies where no natural lowloss magnetic materials are available. A new magnetic particle (metasolenoid) formed by a stack of many parallel and very closely spaced single broken loops is proposed and analyzed analytically, numerically, and experimentally. It is shown that the effective permeability can reach reasonably high values over a wide frequency range when using such inclusions.

Phase conjugation and perfect lensing

The concept of the perfect lens introduced by Pendry [Phys. Rev. Lett. 85, 3966 (2000)], i.e., a possibility to achieve optical resolution well below the wavelength limit using a backward wave (also called Veselago or double-negative) material slab lens, is reinvestigated. It is shown that there is a direct analogy between the phenomena taking place at the slab interfaces and at a couple of phase-conjugating planes placed in free space. Thus, this work introduces an alternative to Pendry’s device. The physics behind the idea is discussed and certain directions of possible realizations are outlined.

Optimization of radiative heat transfer in hyperbolic metamaterials for thermophotovoltaic applications

Using our recently developed method we analyze the radiative heat transfer in micron-thick multilayer stacks of metamaterials with hyperbolic dispersion. The metamaterials are especially designed for prospective thermophotovoltaic systems. We show that the huge transfer of near-infrared thermal radiation across micron layers of metamaterials is achievable and can be optimized. We suggest an approach to the optimal design of such metamaterials taking into account high temperatures of the emitting medium and the heating of the photovoltaic medium by the low-frequency part of the radiation spectrum. We show that both huge values and frequency selectivity are achievable for the radiative heat transfer in hyperbolic multilayer stacks.

Nonlocal permittivity from a quasistatic model for a class of wire media

A simple quasi-static model applicable to a wide class of wire media is developed that explains strong non-locality in the dielectric response of wire media in clear physical terms of effective inductance and capacitance per unit length of a wire. The model is checked against known solutions and found to be in excellent agreement with the results obtained by much more sophisticated analytical and numerical methods. Special attention is given to suppression of the spatial dispersion effects in wire media.

Near-field enhancement and imaging in double planar polariton-resonant structures

It is shown that a system of two coupled planar material sheets possessing surface mode (polariton) resonances can be used for the purpose of evanescent field restoration and, thus, for sub-wavelength near-field imaging. The sheets are placed in free space so that they are parallel and separated by a certain distance. Due to interaction of the resonating surface modes (polaritons) of the sheets an exponential growth in the amplitude of an evanescent plane wave in the system can be achieved. This effect was predicted earlier for backward-wave (double-negative or Veselago) slab lenses. The alternative system considered here is proved to be realizable at microwaves by grids or arrays of resonant particles. The necessary electromagnetic properties of the resonating grids and the particles are investigated and established. Theoretical results are supported by microwave experiments that demonstrate amplification of evanescent modes.

Three-dimensional isotropic perfect lens based on LC-loaded transmission lines

An isotropic three-dimensional flat lens of subwavelength resolution (“perfect lens”), based on the cubic meshes of interconnected transmission lines and bulk loads is proposed. The lens is formed by a slab of a loaded mesh placed between two similar unloaded meshes. The dispersion equations and the characteristic impedances of the eigenwaves in the meshes are derived analytically, with an emphasis on generality. This allows the designing of transmission-line meshes with desired dispersion properties. The required backward-wave mode of operation in the lens is realized with simple inductive and capacitive loads. An analytical expression for the transmission through the lens is derived and the amplification of evanescent waves is demonstrated. The factors that influence the enhancement of evanescent waves in the lens are studied and the corresponding design criteria are established. A possible realization of the structure is outlined.

Veselago Materials: What is Possible and Impossible about the Dispersion of the Constitutive Parameters

Basic physical limitations on the material constitutive parameters of artificial passive materials with negative real parts of the effective parameters are reviewed. It is shown that field solutions in hypothetical materials with negative and nondispersive parameters are unstable. The energy density and field solutions in active metamaterials with nondispersive negative parameters are also considered