There are abnormal azimuth estimates caused by multipath propagation and adjacent signal spectra overlapping in azimuth  estimates of radio source created by radio monitoring complexes in  broad band. In case of multipath propagation, the radio signal phase formed by addition of multipath components in antenna  depends on their amplitudes and phases. If amplitudes of multipath components are approximately identical, and the initial phase difference is from
160 to 200° then the radio signal phase in each antenna may have abnormal value which does not correspond to the direction of  multipath component arrival and results in abnormal azimuth  estimates. When adjacent signal spectra are overlapping there  appear the abnormal estimates depending on the amplitude and  azimuth of spectral component signals from different radio sources. Determination and censoring methods are offered for the both types of abnormal estimates. Censoring of the abnormal estimates caused  by a multipath propagation involves determination of estimation  histogram areas where estimates are grouped or deleted in case they do not belong to this area. Censoring of abnormal estimates caused by adjacent signals spectra overlapping is based on  correlative approach, and consists in determination of the range  formed by adjacent frequency samples, for which azimuth estimates  are strongly correlated between themselves. Application of proposed methods is shown by statistical simulation modeling results and radio monitoring complex data processing results.

The subject of investigation is a space-based altimeter. The goal of investigation is development of MATLAB software model of echo-signal  in a satellite radar altimeter. The phenomenological treatment of a  scattering surface is used as a set of independent reflectors (specular  points) subject to a number of restrictions. The model produced is  applicable to simulating the effect of ranging signal parameters, antenna directivity, sea surface condition and other factors on the received  power profile as well as verification of theory inferences. The software  developed is of a great adequacy to physically predicted echo-signal  characteristics and quite suitable for computer experiments aimed at studying altimeter basic operation modes.

The digital down converters can be used on the radio telescopes with small antennas which are equipped with digital data acquisition  systems with bands Bs = 512 MHz. The down converters provide  extracts a number of signals with bands AF = 16 or 8 MHz at  specified frequencies from the digital sequence of samples of a  wideband signal with the frequency fd = 1024 MHz, 4-level  quantization and formatting of the extracted signals according to the international standard VDIF that used in radiointerferometry. This is  necessary to connect a radio telescope with broadband data  acquisition systems (for example, RT-13) to international radio  interferometry networks (VLBI), which use systems with narrowband (up to 16 MHz) signals. The developed module is made on the basis  of the programmable logic integrated circuit (FPGA) XC7K325T and  provide extracts and formats up to 16 narrowband (16 or 8 MHz) signals from three digital broadband signals that received from the  broadband channels of the radio telescope via fiber optic lines by the 10 gigabit ethernet. The resulting data stream is sent to the buffering device for subsequent transmission to the VLBI correlator. The digital down converters operating at a clock frequency fm = 128  MHz, allow to extract signals in band Bc = 64 MHz and are tuned  with 10 kHz steps by digital oscillator synthesizers. The Bs band of input signal are splitted by 8 channels using 8-channel polyphase filters, which reduce the clock frequencies by eight times. The  module provides the same mode of signal extraction and formatting,  which is widely used in VLBI networks with astrometric and geodetic observations in two wave bands.

The article deals with a low pass op-amp model with high gain at DC and a single-pole frequency response and presents a technique for  simple analysis of negative inductance compensator (NIC) circuits.  Analytical expressions are derived fo r NIC frequency response analysis in case of operational amplifier finite bandwidth. Besides, the ideal NIC circuit comparison results are provided. Calculations show that op-amp  finite bandwidth has impact on NIC impedance at fre quencies 10 times  lower than gain-bandwidth product. The obtained analytical results are  in good agreement with experimental setup measurements of NIC implementation to electrically small antenna impedance matching.

Traditional microstrip coupler devices have found various applications in radio engineering. They can be used in radiolocation, radio  navigation, communications, antenna systems, radio measurements  and other fields of technology. They are also used as a functional  node fo r building power dividers, mixers, modulators, power  summators, and beamforming elements. The design of the branch- line coupler consists of segments of microstrip lines with phase shifts of 90 degrees. However, the dimensions of such devices can be  impractical, especially at low frequencies. Therefore, it is necessary  to use various design solutions aimed at reducing the size of the  device, while maintaining its characteristics at the level of a standard device. In order to eliminate parasitic transmission bands, reduce  overall dimensions and economical manufacture, electrodynamic  structures (ESs) that function as quarter-wave segments will be introduced into the design topology, and their dimensions are much shorter in length, and they can be manufactured by standard etching technology of printed circuit boards. The shape of the ES is chosen  to maximize the use of free space within the coupler, without  crossing adjacent conductor lines. The thickness of the microstrip  lines and the gaps between them are selected in terms of  technological feasibility. To take into account the influence of  neighboring conductive lines on each other and other factors, the AWR DE 13 program was used. The compact design has the following dimensions 15.4 * 16.4 = 252.6 mm2, which is 75.7 %  less than the conventional design. Based on the simulation results, a prototype of a compact coupler was manufactured. Measurements of its parameters were carried out using the vector network analyzer Rohde & Schwarz ZVA 24 and the calibration kit K52. As a result, a  compact design was obtained, easy to manufacture, which can find a variety o f applications in microwave technology. Further reduction in size is possible due to the use of higher resistance lines and a reduction in the gap between them. However, further reduction will lead to a greater decrease in the bandwidth of operating frequencies, and the characteristics obtained will increasingly differ from those of the original design.

Heteroepitaxial silicon-on-sapphire (SOS) wafers with a layer thickness of 200 and 600 nm were fabricated by the vapor phase  epitaxy with monosilane as a precursor. The assessment of structural quality of silicon-sapphire interface was carried out by the surface photovoltage method (SPV) and X-ray reflectometry. Technological parameters of the manufacturing process that affecting to the  amount of SPV signal were determined via SOS quality monitoring.  We conclude that deposition temperature and the growth rate are  most important process parameters in this cause. It was found that  SPV method can be used as monitoring method of SOS fabrication  process, because SPV signals are correlated with Xray reflectometry  results. Probably, SPV method allowed to evaluate the structural and electrophysical parameters of silicon- sapphire interface. SOS device performances as function of SPV signal were determined. The leakage current of test pchannel MOS transistor in the closed state  was on 2-16 nA when SPV signal higher than 450 mV and the  leakage current was approximately 4 nA when SPV signal lower than 450 mV.

A superstatistical approach that takes into account the long-term correlation and the non-stationary dynamics is proposed fo r modelling  aggregated traffic with non-stationary dynamics. By means of queuing  system simulation, it is shown that traditional approximation based on  Kingman's formula underestimates the average sojourn time by up to two decades at high utilization. On the contrary, the use of  alternative superstatistical model taking into account the longterm correlation, this underestimation can be reduced by more than one decade.

The article considers possibilities of using modeling fo r the development of two promising areas of modern nanomaterials, i. e.  materials with a hierarchy of pores organized hierarchical self- assembly and hierarchical structures with nanoporous elements. The  pore size of hierarchical structures was estimated by means of quasi- two-dimensional projection of three-dimensional deterministic fractal Julien aggregate. Three-dimensional modeling of hierarchical  structures organized by means of nanosphere self-assembly was conducted in the Autodesk 3ds Max environment. The article provides analysis of dependences of porosity, density, specific  surface area of fractal structures on the size of aggregates (with the  appearance of new pore levels of hierarchical materials),  dependences of the porosity change in the case of replacement of primary identical spherical particles on porous spheres.