Items of № 11, 2011

The Electrosvyaz Magazine is one of the leading science & technical magazines in Russia.


Research development of vertical cable antennas for LF and VLF bands

New approach is presented in advanced construction of a highly effective carrier for captive vertical cable antenna based on spherical balloon envelope (with flexible diaphragm inside) and umbrella-type stabilizing system placed above the balloon. Captive balloon is hold by means of ground cables, one of which has a conductive coating and operates as antenna, the others are gas-containing hoses connected to gas-holders for gas-filling of a balloon envelope in height position. The proposed highly reliable design avoids the drawbacks of the previous construction of captive drop-shaped balloons which were not properly protected against severe meteorological conditions such as strong gusty winds exceeding 20 m/sec, thunderstorm lighting and wet snow and ice sticking. The possibility to combine several mobile radio stations in a network provides summation of their powers increasing the distance of signal transmission. In case of urgent transmission of highly important information vertical cable antennas are recommended to be deployed by means of air-gun. For cables and balloon envelope innovative high-modulus materials are used.
Key words: cable antenna carrier, captive balloon, aerodynamic wing, reliability, VLF band.



Advanced research into HF harmonic filter systems

The problem of harmonics filtering at the output of powerful broadband HF transmitters in recent two-three decades has not lost its relevance. Design of new transmitters requires a number of challenges to be solved, such as summation of signals from module of power transistors, heat loss decrease and etc.
On the other hand, computer technology and special mathematical programming continues its rapid development in recent years that makes possible to provide a significant turn away from conventional classical methods in synthesis of wideband circuits used for harmonic filters and succeed in optimization of the calculated circuits for much more number of required operative parameters. As an example, one of the many possible tasks is considered, namely, new approach to decrease the total heat loss at all elements of the filter.
Key words: synthesis of harmonic filters, HF transmitters.



Noise clipping when filtering images by way of optimal window

By transfer of analog images on a radio channel they are exposed to a number of distortions, most widespread of which – occurrence noise signal components. The given distortion leads to deterioration of visual appeal of the image, the most widespread methods of struggle against it lead to image degradation. The offered method, being focused on visual perception of the person, allows to weaken essentially noise, without loss of sharpness of contrast sites.
Key words: image processing, noise suppression, filtration an optimum window.



HF radio channel message transmissions in random mode of data arrival times

The way of using HF data transmission system to deliver messages in real time from remote location of gathering information center to the processing information center without a feedback channel is observed in the article. In spite of the changing intensity of the formation of packets of data source reports data transmission rate over the radiochannel is fixed. To solve the problem of data transmission system it is using noise-coding with variable code rate. Formed due to technical differences in the channel bit rate and speed of data flow from the source of information redundancy message almost entirely spent on improving the reliability of message reception.
Key words: data transmission system, HF radiochannel, FEC, data transfer rate.



Non-test adaptive correction of signals in HF serial data transmission systems

The authors propose a method of using segments of the information blocks, closed correcting code as the test for the adaptive correction signals. Segment used to identify impulse response channel must cover the entire signal bandwidth and have no zeros in this strip. Search this segment is taken in each correctly information block, for which the structure of the code construction is proposed to introduce a checksum (CRC).
Such a system doesn’t require frequent transmission of special test signals, thereby freeing up about 1/3 of temporary resource.
The comparative analysis of the systems using the test and the use of code blocks to for communication channel identification. Results of computer modeling are resulted.
Key words: channel identification, correction, serial transmission of information, FEC, correctable byte errors, CRC.



Nakagami distribution parameters rating by information signals

Nakagami distribution parameter estimation method, that is often using for statistical model of signal envelope from radio channel description is reviewed in the article. Information signals are using to get estimation, so it is unnecessary to use superfluity or test signals. At the same time it is necessary to keep some sub-channels unused for transmitting. Maximum-likelihood estimation method is used for estimating unknown distributions parameters. In this method it is using calculated at the same moments sample of signal envelopes from occupied and free sub-channels ratio value and found analytic expression of this value distribution.
So it became possible to make fast estimate of radio channel parameters while automatic gain control is working and it is using multifrequency signal.
Computer modeling showed, that real values and its estimation are similar.
Key words: communication channel, bit error probability, fading, noise, channel estimation, statistical model.



Contemporary trends of time-frequency network support’s development and standardization

The problems of the frequency and time support of telecommunications at the stage of transition to next generation networks (NGN) are analyzed. The means and techniques proposed for the transmission of clock frequency and time stamps in packet networks are considered. The international standardization aspects were emphasized. Key words: NGN, standardization, frequency.



Radio-frequency control based on comparison of electromagnetic oscillation spectrum’s mode shape



Telecommunication network time-frequency support and its time synchronization aspect



Uniform precise time is necessary factor for «System-112» functioning



Measuring low-set antennas’ parameters under high noise level



Telecommunication units’ development planning in competition environment

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