N.M. Ivanov1,  V.N. Shevchenko2

1–2 JSC «All-Russian Scientific Research Institute «Gradient» (Rostov-on-Don, Russia)

The issue of detecting and direction finding a set of signals that differ significantly in intensity occurs in a number of applications. This difference can reach tens of decibels, this makes it impossible to detect and spatially localize weak signals of principal interest. This paper proposes the method to solve this issue.

The standard model of complex envelopes of signals received by the antenna array, as well as Capon direction finding method are used as a basis in the abstracted paper. In the first step, the Capon diagram is generated, which maxima estimate the signal directions of arrival. The signal levels do not go beyond the lower limit of the Capon diagram dynamic range. In the second step, the detected signals are removed from the summary signal received by the array elements. For this purpose, a projection operator is introduced into the subspace, which is an orthogonal complement of the subspace spanned by the phasing vectors of the signals detected. The singular value decomposition of the projection operator allows reducing the issue to generating a modified Capon diagram in the subspace of the orthogonal complement accompanied by the corresponding modification of the received signal and the phasing function. As a result, it becomes possible to detect and spatially localize those signals that are outside the Capon diagram dynamic range.

This paper contains the simulation results demonstrating the effectiveness of the approach proposed. In case of the antenna array containing 16 antenna elements arranged in a circle, the dynamic range of the modified Capon diagram allows detection and direction finding of signals with the signal-to-noise ratio of up to -16 dB.

The proposed method can increase the efficiency of solving the issues of detection and direction finding of signals both in standard and surging covert systems for single-position detection and tracking of mobile objects based on new principles. Such systems include systems of coherent passive location or systems for positioning air objects by comparing the signal of the airborne transmitter with echo signals from natural external reflectors within the control zone.

Ivanov N.M., Shevchenko  V.N. Detection and direction finding of weak signals affected by powerful interference. Radioengineering. 2022. V. 86. № 11. P. 28−33. DOI: https://doi.org/10.18127/j00338486-202211-05 (in Russian)

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