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Orthogonal frequency division multiplexing signals with regard to radar systems

Keywords:

A.A. Ivanov – Ph. D. (Eng.), Senior Research Scientist, FSUE "SPE "Delta". E–mail: Ivanov.MGTU@mail.ru
A.B. Levin – Post-graduate Student, Department of Autonomous Information and Control Systems" (AICS), Bauman Moscow State Technical University Leading Engineer-Radio Operator FSUE "SPE "Delta". E–mail: al_bor@mail.ru


Advances in jamming require using in the radar system of complex noise-like signals, the correlation function of which tends to the delta function. These signals provide excellent resolution in range and the necessary noise immunity. One of the new trends in location is the use of OFDM-signals, which are widely used in broadband data transmission systems due to their noise immunity and spectral efficiency. When using the OFDM-signals in the location systems the spectrum form of the emitted signal is close to rectangular. Mandatory elements of such receiver are the synchronizing circuit and the propagation channel impulse response determining unit. In the article the structure of the location system based on the OFDM-signals was offered, and shown how the signal delay (target range) with help of synchronization circuit is determined, using the correlation in time domain of the guard interval and the useful part of the symbol. At the moment of synchronization (correlation maximum) the frequency shift of the receiver and transmitter by the argument of the correlation function is determined, which when combined receiver and transmitter is a Doppler shift (radial velocity of the target). After the synchronization is the definition of the impulse response of the channel. Since for the combined receiver and transmitter the transmitting information (complex amplitudes of harmonics) is known, so when we get the information at the receiving end, it is easy to determine the frequency response of the channel by the definition of a frequency response of a linear system. Also investigated the effect on the signal reflected from the target of various kinds of interference, and proposed implementation of the "your own - someone else" based on a comparison with the standard (using databases) of informative features, selected after determining the impulse response of the target.
References:

  1. Moose P.H. A technique for orthogonal frequency division multiplexing frequency offset correction. // IEEE Trans. Commun. 1994. Oct. V. 42. P. 2908–2914.
  2. Schmidl T.M., Cox D.C. Robust frequency and timing synchronization for OFDM // IEEE Trans. Commun. 1997. Dec. V. 45. № 12. P. 1613–1621.
  3. Evsikov Ju.A., Chapurskij V.V. Preobrazovanie sluchajnyh processov v radiotehnicheskih ustrojstvah. M.: Vysshaja shkola. 1977.
  4. Sergienko A.B. Cifrovaja obrabotka signalov. SPb.: Piter. 2003.

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