Search

It is shown that architectural design principles based on application of photonics methods have prospects for the development of ultra-wideband and ultrashort-pulse radars. Transmitting and receiving systems with optical controllers based on dispersing fiber-optic prisms are considered. Design versions of a photoconductive antenna excited by picosecond optical pulses and a wideband photoelectronic pattern shaper on the basis of analog vector modulation are presented. A method for compensation of antenna distortion effects arising during transmission of an ultrashort pulse with the use of an optical shaping technique is described.

It is shown that, in the frequency band 3–5.2 GHz, a tape of metal conductors supports slow waves. The field structure of the surface wave in an anisotropically conducting tape is studied experimentally. It is found that the electromagnetic field of the tape has three electric and two magnetic components. Intensity distributions of all field components, the slowing factor of the surface wave, and the loss per unit length are measured.

Two formulations of the problem on transporting microwave power by wave beams with various field distributions are considered. It is shown that, both when the intensity near the rectenna’s edge is limited and when the maximum field intensity on it is limited, beams with the Kelvin and Rayleigh field distributions exhibit better energy characteristics as compared to beams with the Gaussian distribution.

The effect (earlier discovered) of penetration of an electromagnetic-field power flux into a wall exhibiting perfect mixed anisotropic conductivity is considered in more detail. It is shown that the power transmitted into the screen through the nodes of conductivity lines and through resonance-length closed contours can be regarded as the limit value of the power absorbed in a wall characterized by an anisotropic impedance when the absorbing impedance approaches the values corresponding to the case of perfect mixed conductivity.

A variant of solution to the multiparametric problem of power transmission through a microwave beam in the Fresnel zone is proposed. Methods for the power transmission with the use of beams with a Gaussian field distribution and beams having zero intensity along the axis are analyzed. For a specified geometry of the transmit-receive system, a relationship between the maximum power and the admissible field intensity in the rectenna plane is obtained.

It is proposed to use such distribution of the radiated field in a wireless energy transportation system that is similar to the distribution of the modified TEM10 mode generated by a laser. It is shown that, in this case, the product of the aperture efficiencies of radiating and receiving apertures substantially exceeds the value of this parameter corresponding to the uniform and optimum Gaussian field distributions. It is found that, in this case, the potential energy output of the energy transportation system increases approximately by a factor of three and can reach about 15 GW at a wavelength of 5 cm for the antenna and rectenna diameters of 1.0 km and 7.4 km, respectively.

The frequency-selective properties of small screw helical coils are investigated. It is shown that, in a frequency band of 2–4 GHz, such coils have two resonances. The scattering patterns of helical coils are measured in the E and H planes. It is found that, at the zeroth-order resonance, a coil scatters a circularly polarized field with the maximum in the plane perpendicular to its longitudinal axis and that, at the frequency of the first resonance, the maximum of the scattered field is oriented along the longitudinal axis of the coil.

The prominent contribution of Academician V.A. Kotel’nikov to creation of an underground testing ground formed from a periodic sequence of phase equalizers (lenses and reflectors) is reported. A series of experiments that were performed on this unique facility and that involved laser-beam transmission with low loss over a line of a highly stable electric length are described. It is shown that the experience in investigations dealing with beam waveguides initiated research aimed at formation of wave beams with unique properties.

An algorithm for finding the parameters of the microwave beam used for power transportation from a space electric power station to the Earth is considered. It is shown that, for specified geometries of antenna and rectenna systems, it is possible to increase the received power if the density of the radiated power at the antenna center and the truncation parameter of the Gaussian field distribution are simultaneously increased. It is found that, in this case, the transmission efficiency decreases only slightly as compared to the case of optimum transmission.

Three types of elements with an anisotropically conducting surface—a strip, a cylinder, and a sphere—that are of interest for certain applications are considered. It is shown that these electrodynamic objects exhibit resonance properties even when their dimensions are small compared to the wavelength and that resonances occur in both 2D and 3D diffraction problems. It is found that the presence of low-frequency resonances provides for a wide variety of electrodynamic properties of the objects under study and of gratings formed from such elements. Examples of implemented waveguides, waveguide mode converters, frequency-selective circular-polarization antennas, and polarization transducers are presented.

A new method for calculating the radiation loss and chromatic dispersion of leaky modes propagating in microstructured (holey) optical fibers (MOFs) with circular air-filled channels is proposed and implemented numerically. It is shown that the results are in good agreement with both the known numerical data and with the experimental data obtained for two types of fabricated MOFs that contain, respectively, 30 and 60 channels.

The article examines new conditions for semitransparent boundaries in gratings where the period is much less than the wavelength. Solutions of the corresponding boundary-value problems are given.

A short overview of the results obtained by the authors and their colleagues for a long time in the field of the antenna synthesis theory and the related problems of the field transformation is presented. The main common subject in all problems are the free phase functions ascribed to the given amplitude patterns of the antennas, or appearing as the phase corrections in the quasi-optical field transformers. The systems of specific types such as wave beam transformers and antennas with semitransparent surfaces, in particular, resonant and leaky-wave antennas are described. It is shown that some nonlinear integral equations arisen in the antenna synthesis problems with free phase (and their generalizations) have analytical solutions.

The problem of power transmission via a long microwave beam is usually solved by means of the creation of the field that falls at the antenna edges and its focusing toward the rectenna center. It is shown that phase synthesis may be realized with the use of an extra distribution of the radiated field phase. That optimal phase correction provides some power increase when the uniform law describes a radiated field distribution.

A waveguiding structure in the form of a perfectly anisotropically conducting strip is investigated. Across the strip, the Vladimirskii boundary conditions are imposed. These boundary conditions are well justified for a small-period metal grating, provided that the values of the filling factor lie in a certain interval. Thus, an anisotropic strip can be implemented in the form of a system of parallel conductors. The problem of the description of the waves guided by an anisotropic strip is reduced to a homogeneous integral equation in a surface current along the conducting direction.

The authors consider a one-dimensional radiated aperture with a quadratic phase front. The field distribution over the observation plane (a Fresnel area) is analysed. It is required to modify an initially uniform radiated field, so that the diffraction lobes are eliminated over some area of the observation plane. A wave beam from the radiated aperture is focused onto the observation plane. The field distribution represents a general diffraction picture with alternate light and dark bands. The receiving antenna (rectenna) in that plane catches a portion of the microwave radiation and transforms it into direct current.

Resonant transformers of the spatial and polarization structures of waves are known that employ semitransparent surfaces with anisotropic conductance. We consider the problem of excitation of a dielectric ball with the electric dipole located at its center and directed along the z-axis.

A review is presented of some recent theoretical results in the research and development work on artificial spatially dispersive media and on structures possessing chiral properties in the microwave range. The results discussed are mainly obtained for chiral objects taken in the form of long helices of small radius to wavelength ratio, and of arrays of such helices. These structures display strong polarization-selective resonance effects which give rise to a rich variety of their electrodynamic properties.