Volume 70, Nº 6 (2025)

Under the assumption of the cascade power law model of turbulence, the mutual influence of the Earth’s ionosphere and troposphere on the azimuth and range resolution is analyzed when the effect of the Earth’s magnetic field can be neglected. Results of the calculation for the typical troposphere and ionosphere turbulence parameters and their combined effect are presented. Simple approximate formulas for the range resolution and systematic shift error are derived for a linear frequency modulated impulse traversing the ionosphere regular layer.

For controlled multichannel multiband microwave filtering and effective decoupling between signal and control channels and between control channels, a proposed and experimentally investigated meta-interferometer with spatially spaced M1 metastructures (as a beam splitter) and M2 (in a shorted h-arm as a Fabry-Perot resonator reflector) controlled by independently by different methods: M1 – fiber-optically and M2 – electrically. The functional capabilities of a meta-interferometer with M1, containing a grating of parallel resonant dipoles with an orthogonally asymmetrically arranged copper strip (a CdS semiconductor plate in a gap), and with different M2 are shown: a butterfly dipole loaded with varactors and a dipole ring, as well as a grating with copper strip (varactor in a gap). The possibility of independent control of individual interferogram exclusion bands in accordance with the effects of resonant M1 responses (amplitude band transformation) and M2 (frequency transformation).

A simulation model has been developed for generating radar signatures of complex targets, taking into account their spatial configuration, radar-absorbing materials and coatings, diffuse scattering and jet engine modulation of the reflected signal. The model enables investigation of capabilities and robust features for detection and recognition of such complex targets, including those with fractal structures. Estimates of radar cross-section, frequency components of jet engine modulation spectrum, and radar signatures of both elementary and complex targets – including employing Stealth technology – have been obtained. Additionally, radar data necessary for implementing signal processing algorithms based on inverse synthetic aperture synthesis have been generated.

A comparative analysis of sparse image reconstruction methods in remote sensing problems is presented. The efficiency of the methods is estimated by objective criteria of the quality of the reconstructed digital images. The following methods are used as tested: the interpolation method of the sequentially calculated Fourier spectrum, the projection method onto convex sets, the amplitude iteration method, and spline interpolation. The problem is the reconstruction of sparseness modeled according to a randomly uniform law (at least 90 percent of information is missing). The conducted study allows us to draw a conclusion about the fundamental possibility of using the proposed methods for reconstructing sparse images obtained during remote sensing.

It has been found that those interference of stimulated picosecond emission of the Al_xGa_1–xAs–GaAs–Al_xGa_1–xAs heterostructure, created by a dynamic photonic crystal induced by this emis-sion in a GaAs layer, significantly modifies the pulse envelopes of the spectral components of the emission. It has been established that discrete changes in the photonic crystal that change the interference occur under the influence of those part of the emission reflected from the end of the heterostructure.

The necessity of developing a simulator for testing the operation of control command code sequence generation units, monitoring in various switching systems and transmission of measured environmental parameters and their processing after transmission via an optical channel is substantiated. The simulator design is presented using an air-optical communication channel for transmitting information in the form of a command code sequence. The features of using a command code sequence when transmitting analog signals in an optical communication channel are established. The validity of using the proposed method for generating analog optical signals for transmitting them over long distances is confirmed.