Re: Radar - Stronger vs. Faster <long>

[Mike Klein <klein@xxxxxxxxxxxxx>]

> Date: 22 Oct 98 10:07:08 PDT
> From: SMILLER@domain.elided
> Subject: Radar - Stronger vs. Faster <long>
>
...
> Of all the received signals, the
> radar unit locks onto the STRONGEST signal.  The strength of the signal
> is determined by the frontal area and material composition of the object,
> and  proximity to the radar unit. 

It is interesting to note that the strength of the radar signal coming back to
the radar operator is inversely proportional to the *4th power* of the distance
to the target.  This is fundamental to reflective distance measurement methods
where source is a point source, and target is small enough to be considered
also a point sources.  The received strength at the target is inversely
proportional to the square of the distance from the radar gun.  The signal is
reflected with some constant loss (reflection coefficient) and essentially
"retransmitted" from a point source.  The radar gun's received signal from the
target is then also inversely proportional to the square of the distance from
the target.  So the total received signal is proportional (to first order) to:

	Kr/d^4

where Kr is reflection coeff (determined by frontal area, material, angle,
etc.), and d is distance between radar gun and target.

		-Mike

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