Optoelectronics, Instrumentation and Data Processing (v.46, #6)

As a result of solution of the optimization problem, a new method for estimating the amplitude-phase distribution in multielement antenna arrays is proposed and studied by numerical simulation. The method is based on calculating the principal eigenvector of the spatial correlation matrix and increases the efficiency of classical and super-resolution methods for the spatial localization of a priori unknown broadband signals
Keywords: broadband signal processing; multielement antenna arrays; amplitude-phase distribution; coherent averaging; eigenvectors

A problem of searching for man-made objects on the basis of remote sensing of the Earth is considered. It is proposed to perform this search at the pixel level by combined processing of initial images without their preliminary segmentation; each pixel should be characterized by both spectral and spatial (with allowance for the local neighborhood) features. The efficiency of the proposed searching method is quantitatively estimated by means of processing real images.
Keywords: remote sensing of the Earth; multispectral processing of images; search for objects

Sampling functions in nonuniform sampling of a periodic signal by V. M. Efimov; A. L. Reznik; A. V. Torgov (521-532).
Relations for sampling functions in nonuniform sampling of a trigonometric polynomial and its derivatives are obtained.
Keywords: sampling function; nonuniform sampling; periodic signal; sampling theorem; Fourier series

A method for output-uniform coding of memoryless sources with unknown message statistics is proposed. The efficiency of this method is estimated. It is found that this coding is more efficient than coding uniform in input.
Keywords: entropy; coding; redundancy; coding cost; message source

Algorithm of nonlinear quasioptimal digital processing of angle-modulated signals by A. A. Loginov; O. A. Morozov; S. L. Khmelev (539-544).
The paper considers an algorithm for nonlinear quasioptimal digital processing of signals with various types of angle modulation based on a generalization of the Capon minimum variance approach. The algorithm makes it unnecessary to compensate for the unknown frequency shift in the problem of determining the relative time delay of signals during multichannel propagation. Efficiency of the proposed method is demonstrated on phase- and frequency-shifted keyed signals which represent short information sequences.
Keywords: frequency shift keying; phase shift keying; ambiguity function; minimum variance

The possibility of using nonparametric algorithms of pattern recognition for testing hypotheses on distributions of random variables is discussed. Results of computational experiments are compared with the Kolmogorov-Smirnov criterion.
Keywords: nonparametric statistics; pattern recognition; testing of statistical hypotheses; distribution of random variables

Parallel schemes of certain discrete orthogonal transformations by Ya. E. Romm; V. V. Zabeglov (551-564).
The paper describes parallel transformations of the Walsh and Haar transforms with a time complexity O(log2 N), as well as the fast wavelet and saw-tooth transforms. The parallel calculation of the basis of the discrete Fourier transform is performed with a time complexity O(1); the parallel algorithm of the fast wavelet transform is estimated as having a time complexity O(log2 log2 N × log2 N).
Keywords: discrete orthogonal transformations; Walsh transform; Haar transform; wavelet transform; parallel schemes; time complexity

Based on the well-known algorithm of the most likely estimates of the center frequencies of a normal narrow-band random process with a fractional rational spectrum, a similar algorithm for a process with a Gaussian spectrum is proposed and investigated by computer simulation. The practical importance of the development of algorithms for efficiently estimating the parameters of such processes is that they are a sufficiently close model of the output signal of laser Doppler systems used to study hydrodynamic and aerodynamic flows, measure the velocity of diffusely reflecting solid objects, and perform laser sensing of the atmosphere. The results of the studies show that the proposed algorithm does not shift estimates of the Doppler frequency (velocity), gives fairly accurate estimates (for a Doppler system with 25 interference fringes in the measuring volume at a measurement time equal to 100 Doppler periods, the error is only 0.12%), has high noise immunity, and evaluates the resulting errors.
Keywords: random processes; center frequency of the narrow-band spectrum of a normal random process; most plausible estimates; Doppler measuring systems; model experiment

This paper considers a method of using a posteriori information to correct control actions on a poorly formalizable dynamic object and a new design of an observer of unmeasurable variables based on the method of analytical design of aggregated regulators and the concept of recognition of the states of a complex object from the time series accompanying its operation. Numerical simulation results are given.
Keywords: state of a poorly formalizable dynamic object; nonlinear adaptation on manifolds; identification of patterns in the state space; time series

Electrostatic microgenerators of energy with a high specific power by I. L. Baginsky; E. G. Kostsov; A. A. Sokolov (580-592).
Operation regimes of an electrical energy microgenerator based on a multilayered structure consisting of a metal, a dielectric with a built-in charge, a microgap, and a moving electrode, whose operation principle is based on electrode vibrations in the force field of the space charge of the dielectric, are analyzed. Specific features of electromechanical conversion of energy due to vibrations of the electrode surface in submicron gaps are found. It is demonstrated that such microgenerators in the low-frequency regime (10–100 Hz) can produce power sufficient for providing energy for modern microcircuits (up to 1–10 mW/cm2) without using any other power sources.
Keywords: electrostatics; energy microgenerator; dielectric; air gap; microvibrations; space charge

This paper substantiates laser scribing conditions for fabricating mosaic photodetectors based on molecular beam epitaxial (MBE) p-type HgCdTe films on GaAs substrates without loss of image information at a spacing of photosensitive elements (10 µm in diameter) of not less than 46 µm. A scribing technique for linear array photosensitive elements of dimension 4×288 p-n junctions spaced at 56 µm intervals is described in which a two-level depth groove is formed in several passes. In the region of p-n junctions, the groove is formed by radiation with an average power of 1.4 mW, and outside this region, it is formed by radiation with an average power of 2 mW. The groove has varying depth: outside the p-n junction region, the grove is 120 µm deep and 22 µm wide, and in the junction region, it is 26 µm deep and 18 µm wide. It is shown that the laser radiation effect does not lead to accelerated degradation of the electrical parameters of the p-n junctions
Keywords: mosaic photodetectors; laser scribing; photosensitive elements; p-type HgCdTe film molecular beam epitaxy; GaAs substrates

Measuring the thickness of the fluid film moving on a spherical surface by A. P. Belousov; P. Ya. Belousov (601-605).
The dependence of the thickness of the fluid film flowing down the sphere surface in the gravity field on the fluid flow rate and the polar coordinate is measured by an optical method. Comparisons of experimental data with theoretical estimates are demonstrated.
Keywords: film flow; spherical surface; optical methods of measuring the film thickness