CFAR CAGO-CFAR OS-CFAR CASH-CFAR MAMIS-CFAR

Constant False Alarm Rate Receiver(CFAR)

What is CFAR?Constant false alarm rate (CFAR) detection refers to a common form of adaptive algorithm used in radar systems to detect target returns against a background of noise, clutter and interference.Constantfalsealarm rate(CFAR) is a property of threshold or gain control devices that maintain an approximately constant rate of false target detections when the noise, and/or clutter levels, and/or ECM (electronic countermeasures) into the detector are variable.

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Why Do We Use CFAR?CFAR techniques areusedinreceptionand signal processing to avoid increased false alarm rates in the presence of jamming, clutter residue, or other interference sources.The basic feature of CFAR is that the false alarm probability remains approximatelyconstant in clutter by a threshold, riding a definite value above clutter. Targets with an echo power exceeding the threshold level can still be detected.

Efficient CFAR RequirementsEfficient implementation regarding required processing power and production costs.Low CFAR-loss.Accurate fitting of the CFAR threshold to the clutter scenario.The CFAR threshold must pass point targets and extended targets.Closely spaced targets must not mask each other.

CAGO-CFAR

CAGO-CFARThe CAGO-CFAR (Cell Averaging Greatest Of-) comprises essentially a shift register consisting of two sub-registers, each containing L storage cells. Between the sub-registers, the so-called cell under test (CUT) is located. Each sub-register has its own adding circuit.(MAX) is use for adding purpose. Using a multiplicative factor for linear processing or an additive factor for processing with a LOG-amplifier, the threshold value (TV) is calculated. Finally, the amplitude of the signal under test (SUT) is compared with the threshold value to decide whether the SUT belongs to a target or not.

Advantages of CAGO-CFARRequire little processing power.Having low CFAR loss.

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Disadvantages of CAGO-CFARIneffective thresholding.Closely spaced targets can mask each other.MAX-process, the CAGO threshold cannot immediately follow an abrupt rise or fall in clutter level.

OS-CFAR

OS-CFARThe OS-CFAR (Ordered Statistic) comprises a shift register containing A storage cells, plus the CUT. A sorting algorithm arranges the amplitudes of the storage cells in order of decreasing magnitude. In a rank-selection process, the r-th largest amplitude is chosen as a representative of the clutter. The TV is calculated using a multiplicative or additive factor as described for the CAGO-CFAR above. Target detection is accomplished by comparing the SUT with the TV.

Advantage of OS-CFARIn contrast to the CAGO-CFAR, the OS-CFAR has the advantage of effective threshold formation.Disadvantage of OS-CFARThe major disadvantage of the OS-CFAR is the high processing power required for performing the sorting algorithm.