Loss of radio waves energy on radio lines satellite-earth station

The main contribution of this paper is to study the influence of various natural factors on the conditions for the radio signals propagation on the satellite - Earth links. It is shown that the ionosphere practically does not interfere with satellite radio communications at frequencies above 5 GHz. The mathematical model is proposed for the numerical determination of the attenuation of the radio signal depending on the optical visibility during dust storms along the communication path.

Radio line properties of axion dark matter conversion in neutron stars

Axions are well-motivated candidates for dark matter. Recently, much interest has focused on the detection of photons produced by the resonant conversion of axion dark matter in neutron star magnetospheres. Various groups have begun to obtain radio data to search for the signal, however, more work is needed to obtain a robust theory prediction for the corresponding radio lines. In this work we derive detailed properties for the signal, obtaining both the line shape and time-dependence. The principal physical effects are from refraction in the plasma as well as from gravitation which together lead to substantial lensing which varies over the pulse period. The time-dependence from the co-rotation of the plasma with the pulsar distorts the frequencies leading to a Doppler broadened signal whose width varies in time. For our predictions, we trace curvilinear rays to the line of sight using the full set of equations from Hamiltonian optics for a dispersive medium in curved spacetime. Thus, for the first time, we describe the detailed shape of the line signal as well as its time dependence, which is more pronounced compared to earlier results. Our prediction of the features of the signal will be essential for this kind of dark matter search.

INCREASED NOISE IMMUNITY COMMAND RADIO LINK SIGNALS WITH OFDM

Reviewed the work of the command radio link with OFDM signals, which implements a quasicorrelative reception phaseshift keyed signals without a timing that provides improved immunity system and the ability to work in low relations signal/noise at low requirements to stabilize the frequencies of the reference oscillators of transmitter and receiver. The noise immunity estimation of the proposed system in comparison with radio lines operating with signals of frequency telegraphy and relative phase telegraphy is given. The main problematic issues of building a command radio control line caused by the use of OFDM signals are revealed.

Energy budget and methods for determining coordinates for a radiomonitoring system based on a small spacecraft

The existing ground-based radio monitoring systems do not allow performing the functions and tasks of radio spectrum monitoring in a quality manner. Therefore, to improve the efficiency of the radio spectrum monitoring systems for countries with a large territory, such as the Republic of Kazakhstan, it is proposed to use low-orbit small spacecrafts as radio monitoring stations. The analysis of the energy budget of radio lines on the basis of existing radio electronic means on the territory of the Republic of Kazakhstan, carried out in this work, showed the possibility of using low-orbit small spacecrafts for performing the functions and tasks of radio monitoring. The paper proposes and develops a method for determining the coordinates of radio emission sources based on the goniometric method using scanning antennas on board of one spacecraft. The ranges of the antenna scanning angles are substantiated, and the estimates of the coordinates determination errors are made. Algorithms have been developed and computer programs have been compiled to determine the coordinates of the radio emission sources, which will make it possible to use this method at the initial stages of developing a radio spectrum monitoring system based on one small spacecraft.

Technical aspects of creating radiotechnical systems of information and command interface to ensure the functioning of complexes with unmanned aerial vehicles

One of the key components of the complexes with unmanned aerial vehicles (CUAV), which significantly affects the safety and reliability of operation, is the radio link for transmitting command-telemetric and target information of direct radio visibility (radio engineering system of information and command interface) between unmanned aerial vehicles (UAV) and the ground control and information processing point (GCSP). Heavy-class unmanned aerial vehicles can have several target loads simultaneously – a multispectral optical-electronic system, a digital aerial photo system, a radar system, a radio monitoring system, etc. Due to the fact that the flow of information with the payloads to the input of the radio link during peak time moments can be quite large, severe requirements are imposed as to the equipment of primary processing of the target information aboard the UAV and it’s compression in the recording information, and the bandwidth of the radio link in terms of transmission target information on GCSP for subsequent analysis and processing by the operator of the complex. Technical articles are the justification of modern approaches to the development of radio systems of information and team mates in the functioning of complexes with unmanned aerial vehicles, modeling and analysis of directional properties of the antenna system on the basis of the active phased array antenna (APAA) to ensure that decisions adopted targets CUAV, calculation and modeling of the use of various signal-code structures in the information and command-telemetry channels of the CUAV in order to assess the achievable data transfer rates and the energy budget of radio lines. The main tasks of the article are consideration of the nomenclature of possible target tasks of complexes with UAV, proposals for the technical implementation of radio systems of information and team mates, analysis of the advantages of using APAA as part of an unmanned aerial vehicle and a ground control and information processing point in order to improve the efficiency of UAV complexes in the end, modeling of directional diagrams in the azimuth and angular planes for receiving and transmitting modules and receiving and transmitting panels from the APAA, calculation of the energy budget of information and command radio lines, plotting the dependences of the error probability on the signal-to-noise ratio for various combinations of signal modulations and noise-tolerant encoding for various models of communication channels (additive white Gaussian noise – AWGN and binary-symmetric channel – BSC). The main results of the article include specific practical suggestions and recommendations on hardware and software approaches to the creation of antenna systems based on APAA as part of the CUAV, the effect of using modern approaches (reliability, reduced labor intensity and cost, improved performance characteristics), calculated signal-to-noise ratios for various methods of modulation and encoding, obtained as a result of calculations and mathematical modeling, as well as suggestions and recommendations for the rational use of specific types of signals and codes in the command-telemetry and information channels.

Estimation of physical conditions in star formation region S255IR-SMA1

The physical conditions were estimated from the methanol radio lines observed at 0.8 mm with IRAM30m in the star-forming region S255IR-SMA1. In the approximation of a large velocity gradient (LVG), the values of the gas kinetic temperature (170 K), the number density of molecular hydrogen (3×106 cm−3), the specific column density of methanol (2×1012 cm−3s), the relative abundance of methanol (10−7) and the filling factor (10 %). The parameter values are typical for hot dense cores. It is shown that the S255IR-SMA1 object is significantly inhomogeneous within the diagram (7.5 ).

Method of measuring antenna axis ratio close to unit

On purpose to increase efficiency of an orbital-frequency resource the usage of polarization-division multiplexing (PDM) is extended in satellite communication systems. For this aim the axis ratio (AR) of polarization ellipses on satellite radio lines with circular (rotating) polarization must be not less 0,94. Nowadays widespread techniques of experimental defining AR, are based on measurements of orthogonal components intensity of electromagnetic fields created by aerials. But, at high, more than 0,85 axis ratios, the information about a difference in components intensity loses on errors of the measurements realizing these techniques. The method of defining AR, close to extremely achievable value (nearly equal to unit) is presented in the article. The basic idea of this method consists in inclusion to the measurement scheme of two identical devices (DUT), working one towards to another. Also the scheme of counter inclusion of two identical DUT, similar used for measurements, may be applied for designing antenna elements with high AR. Good coincidence of results of modeling, laboratory measurements and field tests have confirmed suitability of the offered method for the designing and testing of aerials with high axis ratio.