The document discusses different types of Constant False Alarm Rate (CFAR) detection techniques used in radar systems. It describes CAGO-CFAR, OS-CFAR, CASH-CFAR, and MAMIS-CFAR. CFAR aims to maintain a constant false alarm rate despite changing noise, clutter, and interference levels. It does this by setting a threshold based on surrounding clutter levels to detect targets above the threshold. The different CFAR techniques vary in how they calculate the threshold from surrounding clutter.

1. Constant False Alarm Rate
(CFAR)
Presented By:
Umair Saeed

2. Agenda
CAGO-CFAR
OS-CFAR
CASH-CFAR
MAMIS-CFAR

3. 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.

4. What is CFAR?
• Constant false alarm 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.

5. Why Do We Use CFAR?
• CFAR techniques are used in reception and
signal processing to avoid increased false
alarm rates in the presence of jamming,
clutter residue, or other interference sources.

6. CFAR
• The basic feature of CFAR is that the false
alarm probability remains approximately
constant in clutter by a threshold, riding a
definite value above clutter. Targets with an
echo power exceeding the threshold level can
still be detected.

7. Efficient CFAR Requirements
• Efficient 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.

8. CAGO-CFAR

9. CAGO-CFAR
• The 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.

10. CAGO-CFAR continue…
• Using a multiplicative factor α for linear
processing or an additive factor β 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.

11. Advantages of CAGO-CFAR
• Require little processing power.
• Having low CFAR loss.

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

13. OS-CFAR

14. OS-CFAR
• The 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 α or
additive factor β as described for the CAGO-CFAR
above. Target detection is accomplished by
comparing the SUT with the TV.

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

16. CASH-CFAR

17. CASH-CFAR
• The CASH-CFAR (Cell Averaging Statistic Hofele)
comprises essentially a shift register configured
by “A” sub-registers, each having its own adder
and containing L storage cells.
• By means of a special maximum-minimum
process a clutter-representative sum-value Sr, will
be selected from the “A” sum-values S1 to SA.
• The threshold value is then calculated using a
multiplicative (α/L) and/or additive (β/L) factor.
• Special maximum-minimum circuit block
interference.

18. Advantages of CASH-CFAR
• CASH-CFAR avoids mutual masking of targets.
• In clutter level with almost no time
displacement.
• CASHCFAR requires much less processing
power than the OS-CFAR with its rank-
selection method.

19. MAMIS-CFAR

20. MAMIS-CFAR
• The MAMIS-CFAR (Maximum Minimum Statistic)
is essentially the same as the CASHCFAR,
• except that the special maximum-minimum
circuit M replaces the adders of the
• CASH-CFAR. The characteristics of the MAMIS-
CFAR are quite similar to those of the
• CASH-CFAR. For the CFAR-handling of block
interference and of point- and extended targets.

21. THANKS