Accuracy Characteristics of the Parametric Burg Method for Spatial Signal Processing in a Nonuniform Array Antenna

Introduction. In the case of a nonuniform (NU) design of the antenna elements (AEs) of the receiving antenna array (AA), the antenna pattern (AP) features sidelobes (SL) with a significantly higher noise level than acceptable values. Under low signal-to-noise ratios (SNR), this noise leads to angular coordinate measuring errors thus worsening the statistical accuracy characteristics (ACs) of the signal. It is of relevance to construct the ACs of angular coordinates when a modified parametric Burg method (BM) is applied to spatial reflected signal processing in a transportable decametre range radar (DRR) with a nonuniform array (NUA) and linear accuracy characteristics. Aim. To analyse the statistical ACs of angular coordinate objects when using a modified BM for spatial reflected signal processing in a DRR with a linear NUA, in which AEs are located with a random step in the range from λ/2 to several λ, where λ is the operating carrier wavelength.Materials and methods. Statistical ACs were constructed by computer modelling in the MatLab software, the reliability of which was confirmed by conventional discrete Fourier transform methods, as well as by comparing the obtained ACs with asymptotic bounds, including Cramer-Rao bounds.Results. The possibility and conditions of using a modified parametric BM for estimating the azimuthal coordinates of reflected radar signals were determined for the case of a nonuniform design of the over-the-horizon DRR receiving AA AEs. Statistical ACs were obtained and compared with the asymptotically optimal ACs of the maximum likelihood estimations corresponding to the uniform AE design.Conclusion. The obtained results confirm the suboptimality of the BM modified for signal processing in the NUA at a random AE spacing step in the range from λ/2 to 2λ, making it applicable for use in transportable DRRs.

Controllable A-T Splitting and Spatial Splitting Inside a Cascade Three-Level Atomic System

We illustrate the experimental observations of Autler-Townes splitting and the spatial splitting in an electromagnetically induced transparency window in a atomic vapor system of D1 line. As the power of the dressing laser beam changes, we study first-order and secondary Autler-Townes splitting. The influences of these dressing beams, which lead to the larger spatial splitting of four-wave mixing and the shift of probe transmission signal with by changing frequency detuning. Studies on such controllable Autler-Townes splitting and spatial splitting effect can be very useful in applications of spatial signal processing and optical communication.

Detection Characteristics of the Parametric Method of Signal Processing in a Sparse Antenna Array of a Transportable Decameter Range Radar

Introduction. The possibility of application of modified parametric methods of spatial signal processing in a sparse antenna array (SEAA) of the receiving position of transportable over-the-horizon decameter range radar (DRR) intended for all-weather remote monitoring of the shelf zone is considered in this paper. With an operational deployment of DRR on unprepared coast, problems of the equidistant location of antenna elements (AEs) often arise. In the case of nonequidistant AEs location and matched spatial processing, antenna pattern has interference sidelobes, which level can significantly exceed the allowable or calculated one for an equidistant AA. A well-known alternative to matched processing are parametric methods of spectral analysis based on the using of models with a finite number of parameters, but their direct application requires an equidistant sampling of the spatial signal.Aim. The aim of the research is to develop and analyze the method of parametric processing of spatial signals of the SEAA which AEs are located on the line with a random step in the range from λ/2 to several λ, where λ is the DRR wavelength.Materials and methods. To construct the detection characteristics (DC) computer modeling in the MatLab environment, the reliability of which was confirmed by the construction of known and theoretically calculated DC, was used.Results. The developed method includes a procedure of restoring (synthesizing) of artificial signal of equidistant AA with subsequent application of Burg parametric algorithm to obtain an estimate of the angular spatial frequency spectrum. To prove the applicability of the parametric method of SEAA signals processing in the case of location signals detecting, DC were obtained and compared with optimal ones.Conclusions. The obtained results have proved the suboptimality of the parametric method of SEAA signal processing at the random AEs spacing step lying in the range from λ/2 to 3λ, what makes it possible to recommend it for using in transportable DRRs.

Помехоустойчивость трехэлементной адаптивнойантенной решетки в многолучевых каналахрадиосвязи ДКМВ-диапазона

Using the modified Watterson model of the radio channel the spatial signal processing (SSP) features of two- and three-element adaptive antenna arrays in thenonstationary multi-path HF channels are investigated. It is shown that the addition of a third antenna element significantly enhances the SSP efficiency of the multipathHF signals in comparison with two-element SSP. Исследованы особенности пространственной обработки сигналов (ПОС) в двух- и трехэлементных антенных решетках в нестационарных многолучевых ДКМВ каналах радиосвязи. Показано, что добавление третьего антенного элемента существенно повышает эффективность ПОС по сравнению с минимально необходимыми двумя ветвями разнесения пространственной обработки.