Joint application of radar visibility reduction and anti-radar masking technologies to protect aircraft from remote monitoring systems

Using spectral energy equations of transmission-reception of wave processes in radio channel with scattering on object and direct radio channel, analysis of energy ratios of information signals and active masking interference at inputs of receivers of remote monitoring systems is carried out. Measures to reduce visibility are aimed at changing the reflective signatures of objects in the interests of reducing the de-masking features contained in secondary electromagnetic radiation to limits that exclude the performance of radar monitoring tasks at established distances and time intervals. Active interference is designed to mask information signals in receiving channels of radar at power that does not allow detecting their designers by passive radar. In case of joint application of not iceability reducing devices and active jammers, radar range reducing coefficient is determined by product of coefficient characterizing possibility of autonomous masking of information signals and coefficient achievable due to reduction of secondary electromagnetic radiation power in the second degree. The laws of increase of aircraft stealth from radar observation with joint application of technologies of reduction of radar visibility and masking by intentional interference created from sides of protected objects and from assigned points have been investigated. In order to maintain the desired signal-to-noise ratio at the output of the receiver with a decrease in the duration of the probing signal, it is necessary to proportionally increase the density of the emitted energy. With given antenna sizes, the maximum signal transmission range is proportional to the root square of their cyclic carrier frequency; increase of this parameter leads to increase of partial coefficient of directional action and effective area of antenna. With a decrease in the cyclic frequency of the carrier of the probing signal, inorder to maintain the required directional properties of the antennas, it is necessary to increase their dimensions.

A method of measuring transmittance of radiation from the film of ice 0 in the IR wave band deposited on a dielectric plate

A method of measuring transmittance of radiation from the film of ice 0 in the infrared wave band is described. Ice 0 is formed from supercooled water at the temperature below –23°C. This ice is ferroelectric and forms a highly conductive layer of the nanometric order of thickness at the boundary with dielectric. The complexity of the experiment consisted in the necessity of using low intensities of the probing signal and considering radiation of the cooled parts of the installation. In order to obtain a thin film of ice, the method of depositing water vapor on a substrate cooled in nitrogen was used. The method rules out formation of condensate in cooling. Deposition of water vapor is possible only in heating, when delivery of cold nitrogen vapor into the chamber with the sample is excluded. To ensure exposure of the film to IR radiation, two sources of infrared radiation were considered: a halogen lamp with a broad radiation spectrum (on the surface of heated glass) and a CO2 laser with the radiation wavelength of 10.6 µm. In the first case, spectral measurements are possible when filters are used. In the installation based on a CO2 laser, an intense signal is emitted, requiring consideration of sample heating. Components of the installation have been elaborated and investigated, on which transmittance of radiation from the film of ice 0 is planned to be measured.

Discovering formation of ice 0 by low-frequency measurement data

In this work, low-frequency characteristics of wetted nanoporous silicate materials were measured, as well as the specimen’s own low-frequency electric fluctuations at the frequencies of 1…100 Hz. The measurements at low frequencies were conducted at different voltages of the probing signal. A capacity cell was used in making the measurements. In the experiments, at the temperatures below –25…–30 °C, non-linearity of the medium was discovered. The experiments on the study of the specimen’s own electric fluctuations at these temperatures revealed their essential increase. These temperatures are below the point of phase transition of supercooled water to recently discovered ferroelectric ice 0. Based on the measurements made, a conclusion was made regarding formation of this modification of ice in the nanosize pores of the wetted materials under study. Ice 0 is a ferroelectric; therefore, its formation from deeply supercooled water may have a significant impact on the electric parameters of wetted bodies at the temperatures below –23 °C. At the interface of such ice with another dielectric, a thin layer with practically metallic conductivity emerges. Such a layer influences not only the non-linear dependence of dielectric permittivity on the electric field but also increases attenuation of electromagnetic radiation in a medium.

Improving the Accuracy of the Output Voltage of the Converter by Changing the Load Parameters

In the article on the basis of the theory of invariance the increase of accuracy of work of system with the converter for nuclear magnetic logging under condition of change of parameters of loading is considered. Based on the proposed functional scheme of two-channel control, formulas are given to determine the structural relationships and internal influences on the parameters of the control system components to reduce the impact of disturbances that occur both by changing load parameters and by changing the supply voltage. To maintain the required value of the carrier voltage amplitude, it is necessary to increase the reference voltage or decrease the amplitude of the sawtooth voltage, which is equivalent to increasing the gain of the feedback circuit. In this case, if you increase the gain of the feedback circuit, you must ensure that the stability of the system is maintained. The implementation of these proposals gives a more accurate formation of the bypass probing signal. The given functional scheme provides realization of regulation and stabilization of amplitude. The paper considers various options for reducing the effect of power supply perturbation on the output parameters of the converter. By changing the period of operation of the sawtooth voltage generator, which is determined by the frequency of the voltage-controlled generator and depends on the output frequency of the inverter, which varies depending on the parameters and properties of the rock during logging, the accuracy of stabilizing the amplitude of the probe signal increases. In the proposed two-channel control system, the first channel provides regulation and stabilization of the amplitude of the output voltage in accordance with the reference voltage. The second channel provides a change in the frequency of the sawtooth voltage generator by determining the period of the voltage-controlled generator from the phase detector, which determines the deviation of the real frequency from the frequency of the reference generator. The application of the above techniques allows to build circuit implementations of the system with transducers for nuclear magnetic logging, which meet the requirements for the accuracy of the formation of the bypass probing signal.

Interperiod coherent integration of the received signal with a variable repetition period of the probing signal

Interperiod coherent integration of the received signal provides an increase in the signal-to-noise ratio and is simply implemented with a fixed repetition period of the probing signals. In practice, pulsed radars use a variable repetition period to protect against blind speeds. The algorithms of the interperiod coherent integration with a variable repetition period have been developed and their features have been revealed, which are advisable to take into account in the practical implementation in the radars. These features determine the complexity of the interperiod coherent integration algorithm, the radial velocity (Doppler frequency) survey interval and the spectrum features. An algorithm is developed with simultaneous interperiod coherent integration of the received signal and a single-delay clutter cancelation in the spectral domain in the case of variable repetition period of the probing signals. The quantitative indicators obtained by modeling are presented and a comparative analysis is carried out.

Possibilities of Estimating F2 Layer Peak Plasma Frequency Using HF Radiation from High Apogee Satellites over Arctic Region

Based on the results of mathematical modeling, we consider the possibility to estimate the plasma frequency F2 layer maximum of the polar ionosphere (critical frequency, foF2) using frequency-sweeping radiation from a highly elliptical spacecraft orbit in the Arctic zone. Our modeling concerning the energy problem of radio sensing consisted of analyzing wave field parameters, received field strength, and SNR on two radio paths with the distances 1900 and 2500 km along the earth’s surface, with the satellite height varying from 10,000 to 30,000 km. Radio path orientations were selected to be close to the classical limit cases of radio wave propagation in the anisotropic ionospheric plasma: quasi-longitudinal approximation and, to a large extent, the quasi-transversal one for the quiet midday and midnight conditions. As a result of these simulations and following specific spacecraft conditions, working with an optimal probing signal was proposed for the appropriate emission power for the onboard transmitter. In the inverse problem of radio sounding of an ionized media, common mathematical inaccuracy in foF2 calculated from the transionogram, frequency dependence of the probing signals magneto-ionic group delay, was estimated. Considering and founding a possible realization of the method, physical prerequisites are discussed based on the experimental data of radio waves passing the 16,000 km long radio path for Moscow–Antarctica (UAS Vernadsky).

Effect of probing signal on the output signals spectrum of nonlinear spin waves in a cross based on waveguides of iron-yttrium garnet film

Subject. A change in the spectrum of spin waves (SW) in a magnetic cross is investigated when two signals pass through it: a pump signal and a probe signal. Objective. Detection of specific features in formation of the spectra of the output signals of SW in the multiport structure based on a yttrium iron garnet (YIG) film in the case of excitation of two magnetostatic surface waves (MSSW) simultaneously by the input antenna, where the first, with power higher than the first-order parametric instability threshold is the pump, and the second one is a probe. Methods. The experiments were performed for a cross structure from YIG film in the form of two orthogonal waveguides with the SW wire antennas placed at the ends of the waveguides, where one of the antennas on the transversely magnetized waveguide was considered as the input. Result. It was found that by choosing the probing signal frequency, one can significantly (by 10 dB) change the relative signal levels for the satellite waves at the output antennas, which are secondary MSSWs with some new frequencies and appear in the output signals spectrum as a result of the thresholdless processes of merging of parametric spin waves generated by MSSW pumping. In this case the secondary MSSWs frequencies can differ at the output antennas located on orthogonal waveguides. Discussion. The discovered effect is associated with the nonreciprocal nature of propagation of both the pumping wave and the waves generated at parametric instability condition in the structure.

Improving of the Probing Signal’s Spectral Content for Devices Nuclear Magnetic Logging

The method of nuclear magnetic logging (NML) allows to distinguish easily enough the intervals in which there are hydrocarbons and to forecast their extraction. Moreover, the principles of measuring using this method are simple enough, despite the difficulties of processes. There were described method of improving spectral composition of probing voltage NML device in this article. The disadvantage of the method is that the resonance area covers all reservoir fluids. Therefore, search for a way to reduce the frequency spectrum and extend the range of the device of nuclear magnetic resonance is a rather urgent task. In the article is stated that within conducting researches is necessary probing signals of large capacity. In this case, it is more appropriate to use switch mode of the power converters. The system of multilevel inverter is created on the base of these converters that allows to get probing signal simply enough. A three-level inverter that generates high-frequency pulses is considered. A virtual model of the converter is constructed together with smoothing and resonant filters, which generate the probing voltage in nuclear magnetic resonance (NMR) devices, using a modified Carr-Purcell-Meiboom-Gill sequence. The result is a wide range of voltages with side harmonics, which have the significant influence on the output signal relative to the base frequency which the NMR device is tuned. The analysis of the harmonic composition of this voltage is conducted. Calculations of intermodulation distortion coefficients for the first and two side harmonics are given. To reduce the influence of side harmonics in the output signal on the quality of measurement by NMR devices, it is proposed to implement additional generators with the phase difference between the side harmonic and the initial phase will be a half of period. The inductors used are transformers that have a ratio of primary and secondary windings of 1: 1 and the secondary winding has the same value of inductance as the replaced coil that was in the model without modifications. Anti-phase side harmonic generators are connected to the primary windings. In this way additionally implemented a galvanic isolation between the generator and the main signal. As a result of simulation of such a converter is obtained an alternative spectral composition of the output signal. After calculations and comparison of the obtained coefficients, it is shown that the proposed method really improves the spectral composition of the output signal. The disadvantages of using this method of spectrum improvement are considered as well. The relative voltage improvement in the case of a 30 ohms load is calculated. The simulation results of the proposed method show an improvement in the spectral composition of the probing voltage by ~ 2.68 times. With this method, it is possible to dampen unwanted side harmonics by adjusting the appropriate frequencies and initial phases so that the generator is always running in antiphase.