The Radar Equation
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Introduction


Before target information can be extracted from an echo signal, that signal must be of sufficient magnitude to overcome the effects of interference.
The radar equation is used to predict echo power and interfering power to assist in making the determination of whether or not this condition is met. Use of the radar equation accomplishes the following:

Assists in the design of radar systems to meet the detection specifications set by the users.

Establishes the relationship between the signal power received and the radar and target parameters

Describes the power received from interfering sources, including thermal noise, clutter, jamming, and EMI.


RCS of the Target :
has units of area.
indicates how large the target appears to be viewed by the radar
is defined as the power radiated towards the radar per unit solid angle divided by incident flux/4π steradians.

.depends on
(1) the angle of incidence at which it is viewed,
(2) the radar frequency and,
(3) the polarization used.


Minimum Detectable Signal


The ability of a radar receiver to detect a weak echo signal is limited:
-by the noise energy that occupies the same portion of the frequency spectrum as does the signal energy. The weakest signal the receiver can detect is called the minimum detectable signal.
-The specification of the minimum detectable signal is sometimes difficult because of its statistical nature and because the criterion for deciding whether a target is present or not may not be too well defined