A.V. Timchenko – Post-graduate Student, imchenkoa11@gmail.com
Yu.I. Savinov – Dr.Sc.(Eng.), Professor, Senior Research Scientist
E.A. Aleshanof – Ph.D.(Eng.), Lecturer, aleshanoff@mail.ru

When using the same frequency band simultaneously by several radio-electronic means (RES), including those that are not participants in the same information exchange, various kinds of unintended interference are created, the need for selection of which reduces the overall signal throughput in the specified frequency band. One of the ways to expand the capabilities of communication channels is most often considered the transition to the use of ultra-wide-band (UWB) signals.
Spatial selection is a promising way to protect against interference among traditional methods and allows you to divide all signal sources into separate orthogonal spatial channels. However, the use of spatial selection is associated with complexity due to the unsteadiness of the directional characteristics of RES antenna systems when receiving and radiation of UWB signals. In this article, we propose an analytical justification for the possibility of selecting a useful UWB signal against the background of a UWB interference for the implementation of its spatial selection. The analytical justification of spatial filtering is based on the use of a ring digital antenna array (RDAA) with electronic control of the directional pattern. On the basis of the RDAA, the UWB signal and UWB interference are received from various directions. Receiving such signals has difficulties in spatial processing, since their correlation interval is comparable or even less than the time of propagation of an electromagnetic wave along the antenna array aperture, which leads to distortion of the shape of the UWB signals and the impossibility of further classical correlation processing.
A method for compensating the time delays of UWB signals is known, which allows for synchronous reception of signals at the input of the receiving device. It leads to the formation of a virtual linear aperture, the normal of which will coincide with the expected direction of arrival of the signal. This is achieved by processing signals in the spectral region by multiplying all elements of the spectrum by phase correction factors that depend on the difference in the signal arrival time to various antenna receiving elements of the RDAA.
However, at the exit of RDAA reception of the useful signal after compensation of the time delays becomes synchronous for all ages of RDAA and signal interference remains asynchronous and provides copies of noise on the number N of antenna receiving elements of RDAA. Although the amplitude of the useful signal increases, the presence of N copies of a powerful interference signal complicates the process of selecting a useful signal masked against their background. For spatial filtering of interference, it is necessary to ensure that the output signal of the channel agreed to receive the useful signal is subtracted from the interference signal.

To obtain a reference copy of the interference, an additional virtual linear aperture is formed in the DIRECTION of the source of the interference, which synchronizes the time of its reception in the same way as the reception of a useful signal. Auto-generated reference copy of the interference is subjected to frequency filtering in filter characteristics taking into account the distortion of the spectrum interference to an angular direction of its reception in the frequency band of the UWB signal, the output of which is formed in advance of the interference distribution recorded in the receiving channel of the useful signal, the result is subtracted from its output signal.
Thus, in the course of the analytical description of the spatial filtering process, the relationship between the function describing the directivity characteristic of the RDAA and the obtained characteristic of the filter that processes the reference interference signal was established. The described processes of receiving and processing UWB signals form the analytical basis for a new method of spatial filtering of a useful UWB signal against the background of UWB interference, and the results of mathematical modeling allow us to count on the possibility of its implementation in the RDAA.

Timchenko A.V., Savinov Yu.I., Aleshanof E.A. Spatial filtering of a UWB signal in a digital ring antenna array against a background of UWB interference. Electromagnetic waves and electronic systems. 2020. V. 25. № 5. P. 92−102. DOI: 10.18127/j15604128-202005-09. (in Russian)

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