Introducing Switching Ordered Statistic CFAR Type I in Different Radar Environments
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Research Article Introducing Switching Ordered Statistic CFAR Type I in Different Radar Environments Saeed Erfanian and Vahid Tabataba Vakili Electrical Engineering Department, Iran University of Science & Technology (IUST), Narmak, Tehran 16846, Iran Correspondence should be addressed to Saeed Erfanian, s [email protected] Received 22 September 2008; Revised 3 December 2008; Accepted 17 February 2009 Recommended by M. Greco In this paper, a new CFAR detector based on a switching algorithm and OS-CFAR for nonhomogeneous background environments is introduced. The new detector is named Switching Ordered Statistic CFAR type I (SOS CFAR I ). The SOS CFAR I selects a set of suitable cells and then with the help of the ordering method, estimates the unknown background noise level. The proposed detector does not require any prior information about the background environment and uses cells with similar statistical specifications to estimate the background noise. The performance of SOS CFAR I is evaluated and compared with other detectors such as CA-CFAR, GO-CFAR, SO-CFAR, and OS-CFAR for the Swerling I target model in homogeneous and nonhomogeneous noise environments such as those with multiple interference and clutter edges. The results show that SOS CFAR I detectors considerably reduce the problem of excessive false alarm probability near clutter edges while maintaining good performance in other environments. Also, simulation results confirm the achievement of an optimum detection threshold in homogenous and nonhomogeneous radar environments by the mentioned processor. Copyright © 2009 S. Erfanian and V. Tabataba Vakili. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
1. Introduction A common routine test in any detection system is to compare the received signal level with a predefined threshold value. If the threshold is crossed, the presence of the signal of interest is declared. In modern radar detection, the decision on target presence or absence is often performed automatically, that is, without the visual intervention of the radar operator. When the threshold is a fixed value, the false alarm rate will increase intolerably (i.e., beyond a level that the computer of an automatic detector can handle) as the interference power varies. In this situation, a constant false alarm rate (CFAR) algorithm with an adaptive threshold is required to keep the false alarm rate constant. In a radar receiver, after amplitude detection, the backscattered signal is sampled in range and/or Doppler and a one- or two-dimensional reference window is formed. The detection in radar means existence or nonexistence of a target in the middle cell of a reference window or a cell under test (CUT). The noise and clutter background is estimated by processing the output from neighbouring cells. A well-
known group for noise estimation is mean-level detectors such as cell averaging
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