А.N. Semenov – Senior Lecturer,

Bauman Moscow State Technical University

E-mail: semenov.an@bmstu.ru

V.I. Krainy – Ph.D. (Eng.), Senior Research Scientist,

Bauman Moscow State Technical University

E-mail: vladk@bmstu.ru

I.А. Rodichev – Student,

Bauman Moscow State Technical University

E-mail: ivan-rodichev@yandex.ru 

The monopulse methods for determining the direction to the target are widely used. The reflected pulse contains complete information about the angular position of the target. The reflected signals are simultaneously received by two or more independent receiving channels and used to determine the direction to the target. This approach can significantly reduce the effect of amplitude fluctuations of the reflected signal, affecting the accuracy of measuring angular coordinates.

In monopulse systems with amplitude ratio estimator, two intersecting antenna patterns are formed to determine the coordinates in one plane. Each radiation pattern is shifted by angles ±θ0 from the line of sight. The difference in the amplitudes of the received signals determines the angle error of the target from the line of sight.

The combining multiple input and multiple output radar and monopulse systems has been studied in the literature. MIMO radar produce a virtual antenna array and can form sum and differential patterns by digital beam forming technic.

In this article a new algorithm for monopulse angle estimation in MIMO radar is considered. The MIMO system with switchable transceivers allow to reduce the total number of elements of the antenna system with equivalent accuracy of angle estimation. 

To calculate the amplitude ratio in monopulse system the partial radiation patterns are formed either by two phase shift vectors of the virtual antenna array or by the Chebyshev weight functions forming sum and difference radiation pattern.

In this case, to increase the accuracy of angle estimation, it is necessary to increase the number of receiving and transmitting elements. This will lead to more complicated system due to the narrowing of the radiation patterns antenna arrays and need beam control system.

Alternative approach is the signal processing based on the calculation of the complex correlation integral Q(r,r0) that can be simplified to the form of calculating the radiation pattern of a virtual antenna array. The maximum value of complex correlation integral is achieved when the intended direction is the same as direction to an observable target.

The calculation of the complex correlation integral does not impose restrictions on the maximum step between the transceivers. It is possible to increase the accuracy of angle estimation using sparse antenna arrays with the same number of elements as in a uniform antenna array. In this case, the suppression of the secondary main maxima will be provided by an non-equidistant step between the elements of the virtual antenna array.

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