Switching CFAR Research Articles

Formulation of a generalised switching CFAR with application to X-band maritime surveillance radar.

A generalisation of a switching based detector is examined, allowing the construction of such detectors for target detection in any clutter model of interest. Such detectors are important in radar signal processing because they are robust solutions to the management of interference. Although formulated in general terms, the theory is applied to the design of a switching constant false alarm rate detector for X-band maritime surveillance radar. It is shown that such a detector manages the problem of interference better than standard detection processes.

Constant false alarm rate detector based on the maximal reference cell

In order to improve the detection performance of constant false alarm rate (CFAR) detectors in multiple targets situations, a CFAR detector based on the maximal reference cell (MRC) named MRC-CFAR is proposed. In MRC-CFAR, a comparison threshold is generated by multiplying the amplitude of MRC by a scaling factor. The number of the reference cells left, whose amplitudes are smaller than the comparison threshold, is counted and compared with a threshold integer. Based on the comparison result, proper reference cells are selected for detection threshold computation. A closed-form analysis for MRC-CFAR in both homogeneous and non-homogeneous environments is presented. The performance of MRC-CFAR is evaluated and compared with other CFAR detectors. MRC-CFAR exhibits a very low CFAR loss in a homogeneous environment and performs robustly during clutter power transitions. In multiple targets situations, MRC-CFAR achieves a much better detection performance than switching CFAR (S-CFAR) and order-statistic CFAR (OS-CFAR). Experiment results from an X-band linear frequency modulated continuous wave radar system are given to demonstrate the efficiency of MRC-CFAR. Because ranking reference cells is not required for MRC-CFAR, the computation load of MRC-CFAR is low; it is easy to implement the detector in radar system in practice.

Improved switching CFAR detector for non-homogeneous environments

In order to mitigate the excessive false alarm rate of the switching constant false alarm rate (S-CFAR) detector at the clutter edge, an improved switching CFAR (IS-CFAR) detector is proposed in this paper. In IS-CFAR, a comparison threshold is generated by multiplying the amplitude of the test cell by a scaling factor. Then in the leading and lagging reference windows, the numbers of reference cells whose amplitudes are smaller than the comparison threshold are countered and compared with a threshold integer. Based on the comparison result, the detection threshold is generated by selecting appropriate reference cells for background noise/clutter power estimation. The detection probability of IS-CFAR in various environments is derived in a closed-form expression. The performance is evaluated and compared with other CFAR detectors. It is shown that IS-CFAR exhibits a low CFAR loss in a homogeneous environment and almost the same detection performance as S-CFAR in a multiple targets situation; at a clutter edge, the false alarm rate of IS-CFAR is much lower than that of S-CFAR and approximates to the greatest-of CFAR (GO-CFAR). Experimental results from a linear frequency modulated continuous wave (LFMCW) radar system are given to demonstrate the efficiency of IS-CFAR.

Comments on ‘Constant false-alarm rate algorithm based on test cell information’

In a recent paper, Cao proposed and analysed a new switching constant false-alarm rate (CFAR) detection algorithm (S-CFAR), which exploits the magnitude of the test cell for the selection of the reference samples. Here we use the order statistic theory to obtain alternative expressions for the detection probability and the false-alarm rate of the S-CFAR in homogeneous background. They are not bulky and thus are easy to calculate for the thresholding parameters.

Introducing excision switching-CFAR in K distributed sea clutter

In this paper a new Constant False Alarm Rate detector which is composed of an excision processor and a switching-CFAR detector, in sea environment with K distribution, has been introduced. The new detector is named excision switching CFAR. Performance of EXS-CFAR is derived and compared with a few other detectors such as CA-CFAR, GO-CFAR and SO-CFAR for the Swerling I target model in homogeneous and non-homogenous noise environments such as those with multiple interferences and clutter edges. The results show that EXS-CFAR 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 gaining an optimum detection threshold in homogenous and non-homogenous radar environments by the mentioned processor.

A generalized switching CFAR processor based on test cell statistics

In this paper, a new constant false alarm rate (CFAR) thresholding algorithm which is a generalisation of the switching CFAR (S-CFAR) that takes into account the statistics of the sample in the test cell for reference sample selection is proposed. It employs a composite approach based on the switching CFAR and the order statistic CFAR (OS-CFAR). A mathematical analysis in a homogeneous environment is provided for this detector. The results obtained show that the detection performance of the generalised S-CFAR (GS-CFAR) is improved both in homogenous background and non-homogenous environment caused by interfering targets and clutter edge.

Constant false-alarm rate algorithm based on test cell information

A new constant false-alarm rate (CFAR) detection algorithm, designated as switching CFAR (S-CFAR), is proposed and analysed. The S-CFAR algorithm selects CFAR reference samples using the magnitude of the sample in the cell under test, which is an information that has not been exploited in any other existing CFAR detectors. S-CFAR closed-form analysis is presented, and comparisons with other representative CFAR algorithms are given. An S-CFAR detector can be tuned such that it has a small CFAR loss when operating on a homogeneous background while achieving improved robustness in the presence of interfering targets and clutter power transition. The S-CFAR detector is also simple to design and implement since no sample ordering is required.