P.N. Zakharov - Ph.D. (Phys.-Math.), Senior Research Scientist, Faculty of Physics M.V. Lomonosov. E-mail: zakharov@phys.msu.ru
A.F. Korolev - Ph.D. (Phys.-Math.), Associate Professor, Faculty of Physics M.V. Lomonosov. E-mail: korolev@phys.msu.ru
E.V. Mitrofanov - Post-graduate Student, Kotel'nikov Institute of Radioengineering and Electronics of RAS. E-mail: mitrjohn@inbox.ru
A.P. Sukhorukov - Dr.Sc. (Phys.-Math.), Professor, Faculty of Physics M.V. Lomonosov. E-mail: apsmsu@gmail.com
V. A. Cherepenin - Dr.Sc. (Phys.-Math.), Professor, Corresponding Member RAS, Kotel'nikov Institute of Radioengineering and Electronics of RAS. E-mail: cher@cplire.ru

Nowadays the efficiency of a radio location system is determined by its information capabilities. Rapid development of technologies based on ultra-wideband signals allowing to increase information capabilities of radio location systems. The present paper considers the construction of an ultra-wideband radar on the base of an OFDM (multiplexing with orthogonal frequency division) probing signal with the restructuring of the central frequency and interpolation of the values of the phase in sub-bands. The principle of operation of radio locators based on frequency scanning is the following. Each rotation angle of the radar antenna, as in the classical scheme, is followed by the measurement of the pulse response. However, instead of direct measurement (measurement of a temporal form of the reflected signal) indirect measurement is conducted. Complex frequency response (FR) of radio channel transmission between the transmitter and the receiver is measured, multiplied by the spectrum of the selected probing radio pulse, inverse Fourier transform the probe to the time domain. The received response is mathematically equivalent to the response to the selected radio pulse in direct measurement (equivalence of measurements in the frequency and time domain). Measurement of complex FR of a radio channel in the simplest case is carried out by consecutive tuning of the sinusoidal signal frequency with a determined step; for each frequency settings the ratio of the amplitudes of received and transmitted signals and the phase difference between them are measured. To increase the speed of the pulse response measurement a complex channel transmission coefficient can be measured simultaneously at several frequencies, therefore it is proposed to use OFDM signal, which contains multiple carrier frequencies. Signals on these sub-carriers are orthogonal in time, what enables to conduct an independent measurement of the complex channel transmission coefficient on sub-carriers. The described system has a number of advantages over systems using the sounding signal in the form of short pulses, including spatial resolution and dynamic range. The results of experimental measurements are presented to demonstrate spatial resolution better than 3 cm.