The article considers the design of optimum time discriminator for onboard delay-lock loop of a spacebased radar altimeter. The basic signal model is simplified remaining however adequate enough to the task of keeping echo-signal within the tracking receiver window. Along with the optimal one the quasi-optimal maximum-point and maximal-steepness-point discriminators are proposed. The discriminator curves of all considered structures are calculated. It is shown that the quasi-optimal discrimination yield about 2.5 times to the optimal one in the equivalent time fluctuations. Such a loss can be considered a tolerable cost of achieved hardware simplicity.

Narrowband approximation of Doppler effect by a frequency shift is inappropriate for some problems of radiolocation, hydro acoustics or passive location. In this case it is necessary to use Doppler stretch (time-scaling) as a signal parameter. Statistical performance of joint Doppler stretch and delay for arbitrary spectral width signal without narrowband approximations is derived in this paper.

Narrowband and wideband parameters relations are investigated for triangle impulse with linear spectral modulation. Besides, Fisher Information Matrices (FIM) differences are analyzed. In the narrowband limit consideration of results in well-known FIM of Doppler shift and delay estimation are proposed. Another feature of wideband FIM is reference time dependence on time delay variance. Transition from Doppler stretch to Doppler frequency shift considering narrowband limitations results in translation invariant FIM.

The article shows that reference time variance of delay estimation is related to estimated parameter modification and velocity influence on delay. Also, estimation variances in narrowband signal model differ from wideband parameter variances by magnitude of spectrum width to central frequency ratio. 

The article is aimed at specifying criteria of synchronization signal inaccuracy when DVB-T2 system local content re-placement cannot be carried out. Some settings of digital information stream are set as the initial data. The first part of the article specifies network delay calculation method. The second part of the article considers the signal cycle instability impact on estimation of local content device delay during its insertion in global information flow. Network delay saw-toothlike dependence on time is revealed, statistical parameters of synchronization signal instability are specified.  The third part of the article deals with analysis of method of substitution of two independent information flows by regionali-zation device. A model of T2 superframes comprising baseband frames (BB frames) which belong to different physical layer pipes (PLP) is described. The conditions under which the local information insertion becomes impossible are de-fined. Besides, the article considers other reasons of failure during single frequency networks (SFN) processing of local content insertion dealing with synchronization error at different stages of information flow digital content generation and delivery to DVB-T2.

Creation of seismic antennas involves production of a system capable to provide synchronous analog-to- digital data signal conversion of all channels and to broadcast digitized signals to the central computing complex (CCC). The article considers a structure of data transmission system from a big number of sources for application in seismic antennas. Moreover, it provides possible ways of preprocessing equipment (PE) unit arrangement in separate hermetic blocks to facilitate their replacement. Besides, the options for PE unit structural and functional schemes are offered. Application of specific chips is explained. The review of the most widespread types of digital convertors is given and the optimal one is chosen for application in hydro acoustic complexes. The option of synchronization with the use of phase-locked loop PLL units is offered. Configuration of data transmission system with the use of Ethernet switchboard setting optimal data transmission protocol is considered.

The limiting characteristics of electrically small-sized loop antenna matching by means of non-Foster's negative inductance are studied. Various options for including negative inductance in frame antenna structure are considered. The analytical limit expression for the operating frequency band of the small-sized loop antenna with the inclusion of negative inductance in the gap of the conductor frame is obtained. It is shown that for practical implementation the most convenient is the scheme with the inclusion of negative inductance between the conducting plane and the free output of the frame. Such inclusion of negative inductance causes small loss in width of the working frequency band compared with the inclusion of this inductance in the gap of the frame conductive plane, but EMF induced in the frame is twice as large.  An integral expression is obtained for the maximum band matching of the small-sized loop antenna with the inclusion of negative inductance in grounded output, the integral in which is calculated numerically for various small-sized loop antenna quality factor and ratios between resonant frequency of the frame and operating frequency range. The results obtained are similar to Fano-Yula restriction for passive matching chains.

The problem of linear antenna construction synthesize is first formulated and solved. Linear antenna consists of antenna array (AR) and power divider (PD). Linear omnidirectional AR with cosecant pattern is synthesized using partial-beam method. Beam-forming scheme for this antenna is based on two directional unequal splitters. The article proposes itera-tive method considering AR and beam-forming scheme mutual effect in terms of scattering matrix. Synthesis results demonstrate rapid convergence of the process and provide optimal pattern.

The article is devoted to the pattern propagation factor of the Earth enabling for more precise determination of the radar station visibility range in case there are reflections from underlying surface. The article provides analytical solution in general form taking into account the Earth sphericity. It enables to obtain the results in the wide-band and altitude range of the observed objects by means of computer simulation. The article gives analytical expression for the Earth multiplier under the flat approximation assumption, free of restrictions common for research literature. Besides, the article defines boundaries in which it is permissible to view the Earth as a flat surface. In addition, the article provides examples to illustrate graphical estimate of the error of all approximations both with respect to the general case of the Earth sphericity and relative to each other.

In multilateration systems, Bancroft algorithm is often used to estimate the location of objects. This algorithm is synthesized for satellite navigation systems. The algorithm allows to obtain the location estimation by means of direct method and does not require significant computing costs. These properties set it apart from algorithms using optimization approaches. However, according to the results of computer simulation, the accuracy of estimation yielded by the algorithm can be several times worse than potentially enable one. The article proposes a method for modifying the Ban-croft algorithm. Modification involves refining the Bancroft estimates by applying the method of small perturbations. The article shows that the use of the proposed modification allows to increase the accuracy of estimates by 2.5–3 times and to make it equal to the Cramer-Rao boundary. At the same time, the complexity of the modified algorithm grows in-significantly.

The object of the study is acoustic metamaterial, which is a steel matrix with a periodic two-dimensional system of cylindrical cavities filled with hydrocarbon mixture. The induced resonances of fluid in cylindrical cavities of the periodic structure are studied for application in liquid fuel sensors. Theoretical studies of the structure show the possibility of exciting axisymmetric and spinning resonance modes in it in the frequency range with a high reflection coefficient of the structure, which manifest themselves as windows with a narrow bandwidth. Experimental studies confirm the existence of such resonances, and the asymmetric resonance mode is more evident. Measurements of various mixtures of gasoline and ethanol show that the sensor has significant sensitivity for distinguishing between conventional fuels, gasoline-based mixtures and the presence of additives in standard fuels.