Electronic Countermeasures (ECM) - MATLAB Simulations for Radar Systems Design - page 481

and for an average aspect angle, it drops to

0.18λ 2 σ chaff 1 ≈ (10.25)

where the subscript is used to indicate a single dipole, and is the
radar wavelength. The total chaff RCS within a radar resolution volume is

chaff 1 λ

0.18λ 2 N D V CS
L beam V R

---------------------------------

σ c ≈

(10.26)

where N D is the total number of dipoles, V R is the radar resolution cell vol-

ume, V CS is the chaff scattering volume, and L beam is the radar antenna beam

shape loss for the chaff cloud.

Echoes from a chaff cloud are typically random and have thermal noise-like
characteristics because the individual clutter components (scatterers) have ran-
dom phases and amplitudes. Due to these characteristics, chaff is often statisti-
cally described by a probability distribution function. The type of distribution
depends on the nature of the chaff cloud itself, radar operating parameters, and
the viewing angle of the radar. Thus, the signal-to-chaff ratio is given by

σ
σ c

S
C chaff

----- CCR

------------- =

(10.27)

where is the target RCS and is the chaff-cancellation-ratio. The value
of CCR depends on the type of chaff mitigation techniques adopted by the
radar signal and data processors. Since chaff is a form of volumetric clutter,
signal processing and MTI techniques developed for rain and other forms of
volumetric clutter can be applied to mitigate many of the effects of chaff. The
next section provides an example of one such chaff mitigation technique.

σ CCR

10.4.1. Multiple MTI Chaff Mitigation Technique 1

In this section, an algorithmic (schema) approach for detecting and tracking
targets in highly cluttered environments is presented. The approach is to accu-
rately track the centroid of the chaff cloud using a combination of medium
band (MB) and wide-band (WB) range resolution radar waveforms.

At moderate Pulse Repetition Frequencies (PRFs), differential target veloci-
ties (about the centroid of the chaff cloud) are detected and tracked via Doppler
banks of transversal filters that are tuned to detect the target velocity differ-

1. This section is extracted from the paper: J. Michael Madewell, Mitigating the Effects
of Chaff in Ballistic Missile Defense, 2003 IEEE Radar Conference, Huntsville, AL,
May 2003.