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Vol 61, No 9 (2018)

Article

Performance Predominance of a New Strategy for CFAR Processors over the N-P Model in Detecting Four Degrees of Freedom χ2 Fluctuating Targets

El Mashade M.B.

Abstract

Modern radars have adopted adaptive processing techniques to mitigate the deleterious effects of unwanted clutter and jammer. In this situation, the CFAR algorithms play a vital role in achieving the heterogeneous detection of fluctuating targets. In this regard, while the CA-CFAR processor has the top homogeneous performance, the OS and TM techniques have been suggested to provide robust estimates of the threshold in heterogeneous situations. In order to simultaneously exploit the merits of CA and OS or TM processors, some their hybrid versions have been recently introduced. They are termed as CAOS and CATM models. Practically, the frequency diversity between noncoherent sweeps is widespread in actual radar systems. Additionally, the pulse integration strategy is often used in radar systems to improve the target signal-to-noise ratio and correspondingly the system detection performance. For this reason, this paper is focusing on analyzing these new models in the case where the radar receiver noncoherently integrates M-pulses to handle its detection. Closed-form expression is derived for their nonhomogeneous performance. The tested as well as the spurious targets are assumed to follow χ2-distribution with four degrees of freedom in their fluctuations. Our simulation results reveal that the new version CATM exhibits a homogeneous performance that outweighs that of the classical Neyman-Pearson (N-P) procedure, which is employed as a baseline comparison for other strategies in the field of adaptive detectors.

Radioelectronics and Communications Systems. 2018;61(9):377-393
pages 377-393 views

S-Shaped Metamaterial Ultra-Wideband Directive Patch Antenna

Dawar P., De A., Raghava N.S.

Abstract

Antenna parameter optimization using S-shaped metamaterial embedded in antenna substrate is elucidated in this paper. Upon incorporation of proposed metamaterial array inside the antenna substrate, the bandwidth of antenna increases by 74% and directivity by about 11%. Results obtained are in good coherence when using the FEM based Ansoft HFSS simulation and MATLAB programming based on CAD formulas using the equivalent circuit analysis of patch antenna. The evolution of ‘S-shape’ has been explained beginning from the primitive Single Split Ring Resonator’s shape. The proposed structure was fabricated and nearly 6% deviation was obtained in comparison with the simulation results. This metamaterial antenna overcomes the low bandwidth limitation of patch antenna and helps in maintaining a low profile by obtaining 81% miniaturization.

Radioelectronics and Communications Systems. 2018;61(9):394-405
pages 394-405 views

Estimation of Optimal Parameter of Regularization of Signal Recovery

Prilepsky J.E., Prilepsky E.D.

Abstract

In this paper there are researched regularizing properties of discretization in a space of output signals for some linear operator equation with noisy data. The essence of proposed method is selection of discretization level which is a parameter of the regularization in this context by the principle of equality of random and deterministic components of the input signal recovering error. It is shown the method, i.e. the solution which is discrete by input signal is stable to small inaccuracies in input signal. At that in case of definite level of output signal measurements inaccuracy the recovering error of input signal is unambiguously defined by input signal sampling increment that allows to select reasonably the regularization parameter for specific criterion, for example, for definite measurements inaccuracy. Specific calculations and examples are represented in explicit form for single-dimension case but this does not restricts generality of proposed method.

Radioelectronics and Communications Systems. 2018;61(9):406-418
pages 406-418 views

Criterion for Minimum of Mean Information Deviation for Distinguishing Random Signals with Similar Characteristics

Savchenko V.V.

Abstract

The problem of distinguishing random signals with similar spectral and correlational characteristics is considered. To solve this problem, a criterion for a minimum of the mean divergence of the hypotheses taken with respect to the true distribution in the Kullback–Liebler information metric is proposed. Using this criterion, an optimal algorithm is synthesized, which allows achieving a guaranteed efficiency gain in discriminating random signals of similar structure. An example of its implementation in the problem of automatic speech recognition at the basic, phonetic level of signal processing is considered. Estimates of its effectiveness are obtained. Theoretical estimates of the effectiveness are confirmed by the results of the experiment. The author’s special-purpose information system was used for this. On the basis of the obtained results, recommendations are given for the practical application of the proposed criterion in problems of statistical signal processing, where a problem of verifying close statistical hypotheses arises.

Radioelectronics and Communications Systems. 2018;61(9):419-430
pages 419-430 views

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