Ant Colony Optimisation-based radiation pattern manipulation algorithm for Electronically Steerable Array Radiator Antennas

A new algorithm for manipulating the radiation pattern of Electronically Steerable Array Radiator Antennas is proposed. A continuous implementation of the Ant Colony Optimisation (ACO) technique calculates the optimal impedance values of reactances loading different parasitic radiators placed in a circle around a centre antenna. By proposing a method to obtain a suitable sampling frequency of the radiation pattern for use in the optimisation algorithm and by transforming the reactance search space into the search space of associated phases, special care was taken to create a fast and reliable implementation, resulting in an approach that is suitable for real-time implementation. The authors compare their approach to analytical techniques and optimisation algorithms for calculating these reactances. Results show that the method is able to calculate near-optimal solutions for gain optimisation and side lobe reduction.     

Analysis of the effect of the shape of the radiation pattern on the accuracy of azimuth measurements by the monopulse method

The effect of the shape of the radiation pattern of the difference channel of a monopulse antenna on the accuracy of angular-coordinate measurements is estimated. The least root mean square deviation is obtained using a radiation pattern with a Chebyshev amplitude distribution. Of the practical amplitude distributions a “parabola on a pedestal” of 0.1–0.316 is preferable. Translated from Izmeritel'naya Tekhnika, No. 4, pp. 53–54, April, 1998.     

Optimised design of multi-band cellular base station antenna array for GSM and UMTS deployment

A tri-band dual polarised printed patch array is designed for GSM and UMTS cellular deployment using an efficient moment method code driven by a marginal distribution optimisation algorithm. Novel techniques are introduced to expedite analysis while maintaining adequate accuracy, and two methods are used to aggregate elements into an array for pattern synthesis: unequal spacing and phasing. Optimisation criteria such as crosspolar isolation, return loss and radiation pattern characteristics are successfully achieved in simulation, and a measured prototype element supports the antenna concept.     

Taking into account the radiation pattern of a practical feed for a Luneberg lens

A method of taking into account the real feed radiation pattern for a Luneberg lens is proposed. According to this, the field of a feed with the given radiation pattern is expanded into series in spherical harmonics. Using this approach, it is possible to introduce the radiation patterns of real feeds into strict electrodynamic solution for a Luneberg lens, thus significantly refining a mathematical model of the antenna.     

Heat loss in the channel of a plasmatron

A mathematical model is constructed and a computational experiment is carried out to determine the characteristics of a longitudinally blown electric arc in the channel of a plasmatron under conditions of local thermal equilibrium. A feature of the model is that it makes allowance for radiation transfer in the real spectrum of an electric- arc plasma. An algorithm for solving the problem is presented and the effect of radiation reabsorption on the radiation and conductive heat loss in the plasmatron channel is shown.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 58, No. 3, pp. 505–511, March, 1990.     

The behavior of the instantaneous Poynting vector of symmetrical laser beams

In this work we investigate the behavior of the instantaneous Poynting vector of symmetrical paraxial laser beams, namely the modification of the instantaneous Poynting vector and the radiation pattern during propagation in free space for a variety of such beams. As an example, we have investigated in detail the behavior of the instantaneous Poynting vector and the radiation pattern of the paraxial Gaussian and Bessel beams.     

Study of the correlation between administered activity and radiation committed dose to the thyroid in 131I therapy of Graves' disease

Substantial reduction in the thyroid volume (up to 70-80%) after 131I therapy of Graves' disease has been demonstrated and reported in the literature. Recently a mathematical model of thyroid mass reduction during the first month after therapy has been developed and a new algorithm for the radiation committed dose calculation has been proposed. Reduction of the thyroid mass and the radiation committed dose to the gland depend on a parameter k, defined for each subject. The calculation of k allows the prediction of the activity to administer, depending on the radiation committed dose chosen by the physician. In this paper a method for calculating k is proposed. The calculated values of k are compared to values derived from measurements of the changes in thyroid mass in twenty-six patients treated by 131I for Graves' disease. The radiation committed dose to the thyroid can be predicted within 21%, and the radioiodine activity to administer to the patient can be predicted within 22% using the calculated values of k. The thyroid volume reduction during the first month after therapy administration can be also predicted with good accuracy using the calculated values of k. The radiation committed dose and the radioiodine activity to administer were calculated using a new, very simple algorithm. A comparison between the values calculated by this new algorithm and the old, classical Marinelli-Quimby algorithm shows that the new method is more accurate.     

Optimizing the radiation pattern of sparse periodic linear arrays

We have developed a method for designing sparse periodic arrays. Grating lobes in the two-way radiation pattern are avoided by using different element spacings on transmission and reception. The transmit and receive aperture functions are selected such that the convolution of the aperture functions produces a desired effective aperture. A desired effective aperture is simply an aperture with an appropriate width, element spacing, and shape such that the Fourier transform of this function gives the desired two-way radiation pattern. If a synthetic aperture approach is used, an exact solution to the problem is possible. However, for conventional imaging, often only an approximation of the desired effective aperture can be found. Different strategies for obtaining these approximate solutions are described. The radiation pattern of a sparse array designed using the effective aperture concept is compared experimentally with the radiation patterns of a dense array, and sparse arrays with periodic and random element spacing. We show that the number of elements in a 128-element linear array can be reduced by at least four times with little degradation of the beam forming properties of the array     

Method for Realizing the Possibilities of the Dulkyn Low-Frequency Gravitational-Wave Detector

A system is proposed for self-compensating low-frequency noise in the Dulkyn pentagonal laser-interferometer low-frequency gravitational-wave detector. For a signal-to-noise ratio at the output of the optical part of the scheme of no better than 10^–7, the system makes it possible to operate in real time after roughly 25 periods of a detected gravitational-wave signal. With the orbital motion of the Earth this will make it possible to implement an antenna (a response of the detector to gravitational radiation) having an artificial aperture and a radiation pattern width of a few minutes of arc.     

Mathematical Simulation of Radiation Instability and a Possible Method of Taking Instability into Account in Realization of the Unit of Power of Laser Radiation and Dissemination of the Unit of Power

The present study is devoted to mathematical simulation of the instability of laser radiation. An algorithm for establishing the shape of continuous laser radiation received at the input of a measuring system is presented.     

Directional Modulation Based on a Quantum Genetic Algorithm for a Multiple-Reflection Model

Directional modulation is one of the hot topics in data security researches. To fulfill the requirements of communication security in wireless environment with multiple paths, this study takes into account the factors of reflections and antenna radiation pattern for directional modulation. Unlike other previous works, a novel multiple-reflection model, which is more realistic and complex than simplified two-ray reflection models, is proposed based on two reflectors. Another focus is a quantum genetic algorithm applied to optimize antenna excitation in a phased directional modulation antenna array. The quantum approach has strengths in convergence speed and the globe searching ability for the complicated model with the large-size antenna array and multiple paths. From this, a phased directional modulation transmission system can be optimized as regards communication safety and improve performance based on the constraint of the pattern of the antenna array. Our work can spur applications of the quantum evolutionary algorithm in directional modulation technology, which is also studied.     

On the Study of Partial Coherence via Diffraction Experiments

The radiation pattern of a circular aperture illuminated both uniformly and non-uniformly by partially coherent light is calculated in the diffraction limit. Furthermore, the angular resolution of a circular lens is examined for four reasonable correlation functions. Also the effects of the parameters—partial coherence, misalignment, and non-uniform illumination—on the diffraction pattern of a double slit are considered for a particular mathematical model of the radiation field. The results of this analysis are used to discuss the the use of diffraction experiments in the study of the coherence properties of light.     

A method of determining the spatial position of the phase center of log-periodic antennas

A method of estimating the position of the phase center of log-periodic antennas from the phase radiation pattern in the intermediate zone is proposed. __________ Translated from Metrologiya, No. 4, pp. 39–43, April, 2008.     

Investigation of cross talk in Kerfless annular arrays for high-frequency imaging

The effect of electromechanical cross talk in high-frequency (> 30 MHz) kerfless annular arrays is investigated. Finite-element model predictions of the radiation patterns from arrays are compared to predictions from an ideal model without cross talk and with experimental measurements. High cross talk in the array causes element broadening and an increase in the amplitude of secondary lobes in the radiation pattern. However, an increase in the pulse ring-down time was not found. This can be attributed to the absence of lateral modes in the kerfless substrate. The level of the pedestal secondary lobes in the two-way radiation pattern increases linearly with the element path difference. The element broadening increases the effective element path difference, which increases the pedestal level for a kerfless annular array above the level for an ideal array. The broadening limits how close to an array one can image compared to the ideal case by reducing the contrast available in the image at small f-numbers. When the element broadening is taken into account by widening the electrode dimensions, the ideal radiation pattern agrees well with the finite-element model and experimental radiation patterns.     

Computer synthesis of antennas

This paper proposes that computer synthesis of antennas considers field and current distributions over a given radiation pattern with a numerical method. We introduce necessary constraints associated with visible angles and finiteness of antenna dimensions; these constraints assure practical realization of the amplitude-phase distributions found and assure high-precision reproduction of the radiation pattern. Computational results are presented graphically. Translated from Izmeritel'naya Tekhnika, No. 6, pp. 27–28, June, 1996.     

Evolution of the diffraction pattern of probing radiation reflected by a silver surface upon melting

Evolution of the diffraction pattern was studied experimentally using a sample of silver with a moderately rough surface formed by the composition of predominantly unidirectional grooves. The sample was heated in a tubular electric furnace; its temperature was determined by a thermocouple measurement. At a temperature close to the liquidus temperature, the appearance of isotropically scattered radiation, concentrated near the specular beam, is detected. We analyzed the evolution of these radiation components upon melting and showed that the nucleation is the source of isotropic scattering. It is found that the evolution of the diffraction pattern enables one to observe the melting of the surface layer, accompanied by the simultaneous existence of the disappearing solid phase and the growing liquid phase. Spreading of the sample melt over a substrate can be also observed with the diffraction pattern.     

Two-element superdirective array antenna composed of high-Tc superconducting small helical radiators

Superconductors offer the potential for achieving highly efficient small and/or superdirective array antennas. This paper describes the design and reports experimental results for a two-element superdirective array antenna fabricated with YBaCuO superconducting material. 0.05 helical radiators and quarter-wave matching and branch circuits were designed for an array antenna with a 0.09 radiator spacing, to obtain a superdirective radiation pattern at 900 MHz. The array antenna thus fabricated realized good impedance matching and higher radiation efficiency than a Cu antenna, and a unidirectional radiation pattern at 80 K and around 900 MHz.     

Anomalous backscattering of high-power laser radiation by the flat surface of a solid

Results of measurements of the backscattering characteristics of high-power laser radiation at flat randomly rough surfaces of various materials are described for a wide range of radiation and surface parameters. It is observed that for probe radiation intensities in the range ∼10³–10⁷ W/cm² and a pulse duration of ∼10⁻⁸ s the scattering pattern becomes anomalous under various additional conditions. The results are analyzed in accordance with the laws of structural conditionality, the qualitative boundary, abnormality, and alternation of nonequilibrium. Possible practical applications of the observed effect are discussed. Pis’ma Zh. Tekh. Fiz. 25, 29–38 (August 26, 1999)     

Algorithm for the solution of the problems of body heating during radiation heat transfer

An algorithm is obtained that permits computation of the optimal metal heating mode in a furnace with minimum fuel consumption during radiation heat transfer.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 59, No. 5, pp. 849–853, November, 1990.     

Transmission and radiation in a slab waveguide coupled to a whispering-gallery resonator: volume-integral-equation analysis

The excitation of a whispering gallery resonator by a surface wave guided in a dielectric slab is analyzed with a rigorous volume-integral-equation approach. The analysis is based on the Green's function concept and the application of the entire-domain Galerkin technique through expansion of the electric field in the resonator in terms of cylindrical wave functions. The algorithm developed yields highly accurate results for the transmission and reflection coefficients in the waveguide. The radiated far field is computed, and the effect of the excitation of a whispering gallery mode on the radiation pattern is studied.