1998, volume 3, № 2

MICROWAVE SEA BACKSCATTERING AT EXTREME GRAZING ANGLES

G. P. Kulemin

7-32

In the present review the microwave sea backscattering features for extreme grazing angles are analyzed when sea surface shadowing is essential and scattered signal acquires the discrete form. The review consists of two parts. In the first part the heavy sea main characteristics are discussed, which are essential for radar observation at grazing angles; the sea surface spike characteristics have been analyzed in the frameworks of the statistical theory of random process surges above a certain boundary; the sea surface shadowing function has been considered. In the second part the spike characteristics of sea backscattering, the polarization and spectral features of the scattered signals are analyzed.

FREQUENCY DEPENDENCE OF OBJECTS IN DM WAVEBAND

V. I. Lutsenko, S. I. Khomenko

33-37

The results of experimental investigations into the frequency RCS dependences of wire, plate-like and volumetric models of small-size-objects for HF- ground wave radar are presented. It is shown that in selecting the wavelength of an irradiating field, which is approximately four times greater than the vertical dimensions of an object, a significant increase in its RCS up to a magnitude commensurable to the RCS resonance dipole may be expected.

A MATHEMATICAL MODEL OF SCATTERING OF SCALAR WAVES ON A SYSTEM OF SPHERICAL SCREENS

V. G. Dudka, Yu. V. Svischov, Yu. A. Tuchkin

38-42

The problem of the scalar wave diffraction on a system of open-ended spherical screens has been rigorously solved. The solution has been found with the iterative method of successive reverberations combined with the mathematically rigorous approach used for the problem of the scalar wave diffraction by a single screen. The numerical experiments show the high efficiency of the suggested method in the analysis of the wave scattering on a system of spherical screens of large wave dimensions.

MODES OF COMPOSITE TWO-LEVEL OPEN RESONATOR

I. K. Kuz’michov, B. K. Skrynnik

43-46

Variations in the field intensity distribution of the composite open resonator (OR) with an elevation height above the flat mirror partially covered by a diffraction grating are examined. Any field distribution of the composite OR is shown to be represented as a sum of several oscillations of an ordinary OR (without grating) by selecting oscillations amplitude coefficients. Each of the “bush” oscillation of this kind behaves as a whole and, as the two “bush” oscillations get closer to each other at a resonance distance, an interaction of the above ostillations occurts.

INVESTIGATION OF PARTIALLY FILLED RECTANGULAR WAVEGUIDES WITH REGARD TO DIELECTRIC LOSSES

L. B. Minakova

47-51

A spectrum of eigen H_m0 modes of partially filled rectangular waveguides is analyzed with regard to dielectric losses. A plate is arbitrarily placed in the E-plane of a waveguide and completely covers its cross-section from top to bottom. Dielectric losses are taken into account through the rigorous solution of a corresponding spectral boundary problem. An influence of placement, thickness, and a degree of filling upon the dispersion characteristics of the basic and higher modes has been studied. A comparison is made between the rigorous, and known approximate results from calculating the mode attenuation constants in non-ideal partially filled rectangular waveguides.

RADIATION OF LASERS WITH RING GEOMETRY OF AN ACTIVE ELEMENT

M. I. Dzyubenko

52-56

In the geometrical optics assumption the spatial - angular characteristics of radiation of dye lasers with a ring cell and lamp excitation have been analyzed. It is shown that in external pumping the divergence of laser radiation is basically determined by spiral refractive trajectories which form a non-stationary orientation diagram (pattern) limited by two conic surfaces. In pumping the cell ring from inside, the spatial – angular parameters of the laser are determined by the modes of an unstable resonator whose parameters are transient and depend upon the cross distribution of the energy pumping absorbed in an active element.

ACCOUNT OF THE SPECTRAL-TEMPORARY CHARACTERISTICS OF RADIATION OF XENON FLASHLAMPS

V. V. Shevchenko

57-63

The spectral-temporal characteristics of pulse xenon lamp emission are theoretically investigated with non-stationary microsecond-duration discharges. It is shown that under these conditions two factors have a simultaneous effect, namely, thermal inertia of a gas-discharge gap and a limited strip of the lamp envelope transparency.

SUBMILLIMETRE DISCHARGE HCN LASER WITH THE INTERNAL FILM ELECTRODES

N. F. Dachov, Yu. E. Kamenev, V. K. Kiseliov, E. M. Kuleshov, V. P. Radionov

64-65

A submillimeter HCN discharge laser intended for biomedical investigations under clinical conditions is described. The laser is simple in design, easy in manufacture and safe in use. The gas discharge excitation is performed with the film electrodes of unique design, which are placed inside the quasi-optical waveguide resonator. The laser radiation parameters for a wavelength of 337 mcm are presented.

THE ANALYSIS OF THE TWO-COMPONENT IONIC CLOUD IN THE NONEQUIPOTENTIAL CHANNEL

G. A. Alexeev

66-68

An analysis of the influence of a two-component ionized gaseous medium on the static potential distribution in the nonequipotential channel is performed on the basis of the numerical computation of the self-consistent system of the ambipolar current continuity and Poisson equations. The analysis shows that the space nonequipotentiality may be an additional cause of the resorption of the natural ionic trap in microwave electron O-type devices.

PERIODICAL STRUCTURE OF FEL, CONSISTING OF COUPLED GROOVED WAVEGUIDES

V. S. Miroshnichenko

69-72

The periodic structure of a free electron laser (FEL) consisting of coupled grooved waveguides, located in parallel to each other with a period L < , is considered. The common gap between parallel planes of waveguides is the transit channel for an electron beam. In such an electrodynamic system, the directions of propagation of waves in grooved waveguides and an electron beam are orthogonal, and the electron beam interacts with space harmonics of the fast waves field an. The experimental method of analysing the critical regimes for fast waves in a periodical structure consisting of coupled grooved waveguides with any cross-section of grooves is implemented. The critical lengths of waves in coupled grooved waveguides with rectangular, H-waveguide and Helmholtz-form of grooves for several values of a width of the channel are obtained. A comparison to theoretical data for one-grooved and two-grooved waveguides of the rectangular profile is made.

OPTIMIZATION OF HETERODYNE AMPLIFICATION CIRCUITS OF THE MILLIMETER WAVE RANGE

P. I. Mos'pan, L. P. Mos'pan

73-76

Results of experimental studies of mm-wave varactor amplification circuits intended as high coherent courses of electromagnetic oscillations in heterodynes of special receiving and measuring devices are presented. A possibility of designing the amplification circuits having improved characteristics and a fewer number of amplification units is experimentally found. Some recommendations for design of the mm-wave varactor amplification are presented.

PECULIARITIES OF MOVING TARGETS SELECTION IN THE CASE OF SMALL DOPPLER FREQUENCY DIFFERENCES OF LEGITIMATE SIGNAL AND PASSIVE INTERFERENCE

A. A. Belov, V. M. Pischuhin, V. A. Tarshin

77-79

In practice the situation, when the received signal measurement have an energy character (when the difference between the informative parameters of targets and interference source are less than matching interval of separation appears rather often). In this paper the Doppler frequency shifting was considered as such parameter. The co-operative filtration algorithms of Doppler frequency and amplitude (average energy) of radar signal in the case of passive interference action are proposed. These algorithms make available reduction of Doppler frequency measurement fluctuation errors.

ANALYSIS OF LOCAL ACTIVITY INDICATOR BEHAVIOR FOR NONLINEAR ADAPTIVE FILTERS

V. V. Lukin

80-89

The local activity indicators (adaptation parameters) to be used in hard-switching nonlinear adaptive filters are considered The peculiarities of Z-parameter behavior are analysed and it is shown that they permit to recognize various situations with high enough reliability. It provides high quality of information data processing when the signal is corrupted by noise with a priori unknown characteristics.

GEOMETRICAL PROPERTIES OF NON-REDUNDANT APERTURE OF RECONSTRUCTIVE INTERFEROMETRICAL SYSTEM

V. N. Uvarov

90-95

In designing the apertures of astronomical systems of image reception, which have high space resolution under the conditions of phase registration instability the non-redundant apertures are employed. For the analytical description of the above structures, their studies and utilization a group of abstract sets generated by a set of elements of non-redundant clusters has been introduced. The algorithms of synthesis and filtration of non-redundant clusters are developed. These algorithms exhibit high adaptivity. A fractal approach has been used to study the geometrical properties of non-redundant apertures. A dependence of fractal dimensions of aperture clusters upon the configuration of an enveloping aperture has been studied. The results obtained may be employed to design astronomical systems of acquiring high-spatial resolution images under the conditions of phase registration instability.

INVESTIGATION OF QUASI-OPTICAL WAVEGUIDE MODELING METHOD FOR THE STUDY OF BACKWARD AND FORWARD SCATTERING IN MILLIMETER AND SUBMILLIMETER WAVE BANDS

V. K. Kiseliov, T. M. Kushta, P. K. Nesterov

96-102

A possibility of using the method for quasi-optical waveguide modelling (QWM) to study the forward and backward amplitude-phase responses of physical objects and their scale models in the near millimeter and submillimeter bands of an electromagnetic spectrum has been theoretically and experimentally substantiated. In order to implement this method a quasi-optical laboratory measuring homodyne-type installation based on a round, hollow dielectric waveguide (HDW), waveguide and quasi-optical devices and transmission-line elements. As well as on a set of IBM PC/AT hardware and software packages and on standard modules made in a 4-mm wave band has been developed.

SPECTRAL STRUCTURE OF THE “ITALIAN” TIMBRE OF THE VIOLIN SOUNDING

V. K. Lapty

103-106

Since it is possible to make an objective estimate of the timbre quality [2] based on using the dynamic spectra of harmonics and original digital signal processing, physical investigations into the phenomenon of the “Italian” timbre of violin sounding have been carried out. These violins were hand-made by medieval craftsman of the town of Cremona. The representative samples of collection (7 specimens) and ordinary (more than 100 specimens) were selected for comparative studies of their spectral-frequency characteristics (SFC) of the sounding timbre (ST), and the essential peculiarities of the SFC ST in Cremona violins have been revealed. By averaging SFC ST of collection violins marked with the highest expert estimate of the timbre sounding quality a reference SFC ST of a violin has been synthesized. This violin can serve as the basic item for diagnosing the violin timbre sounding and developing the scientifically grounded technology that may be applied to manufacture the instruments having top-quality timbre sounding.