Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!rice!snowy.rice.edu!frank
From: frank@snowy.rice.edu (Franklin Tae-Sung Kang)
Newsgroups: sci.electronics
Subject: Re: RCS and How RAM Works, with applications information
Keywords: radar, dielectric discontinuity, stealth
Message-ID: <1991Jun25.212213.21508@rice.edu>
Date: 25 Jun 91 21:22:13 GMT
References: <1991Jun24.055534.24442@cs.mcgill.ca> <1991Jun24.231722.12091@kodak.kodak.com> <1991Jun25.174433.25693@eng.umd.edu>
Sender: frank@owlnet.rice.edu
Organization: Rice University
Lines: 46

In article <1991Jun25.174433.25693@eng.umd.edu> sdorsey@eng.umd.edu (Bill Dorsey) writes:
>In article <1991Jun24.231722.12091@kodak.kodak.com> ornitz@kodak.kodak.com (Barry Ornitz) writes:
>>>[Question about radar reflecting off glass]
>>Of course it does.  Glass has a dielectric constant higher than air.  It is
>>not as good a reflector as metal, of course, but radar waves do reflect off
>>glass.  The same can be said for any material, of course.  It is merely a
> [stuff about radar be reflected due to angle of windshield]

In the Stealth Aircraft Handbook, it states that the cockpit was a 
great source of reflected radar waves.  The radar would penetrate 
through the cockpit glass and  reflect back through all the 
90 degree angles(which are the best shape to return radar energy).
To fix this, they sprayed the glass with some type of metal such that
the gaps bewteen the metal droplets were too small to allow the 
radar waves to penetrate.  I suspect the penetration of glass is also
dependent on the wavelength used, but it seems like the greatest
advantage would be to make the windshield as reflective as possible
so the reflections would go away from the source.

>Placing RAM in front of the major contributors to the RCS of a car will
>reduce the effective range of the policeman's radar gun.  According to
>The International Countermeasures Handbook, a reduction in RCS of 20 dB
>will result in a reduction in effective range of the radar of 68%.  Given
> [misc stuff deleted]
>of the reflectors in one's car with RAM, significant reductions in the
>range of police radar can be achieved.

I had thought police radar could get readings from a mile or two 
away.  If that range was reduced to a 1/2 mile, that is still 
well within the range most police use to clock cars.  As much as
I would like it, I really don't think RCS could be reduced such
that it would be usefull against getting clocked by radar.

Perhaps a more feasible method would be to get fake returns as 
someone suggested.  I could swear that some mentioned in rec.autos
that the cooling fan returned something in the 40mph range.
One could make the fan very reflective while minimizing the 
RCS of the car...

Why don't we forget this idea and work on turning the car into
a black body.  Then we'll lick the laser speed detecting devices
at the same time.  The down side is that it could get pretty hot
during the summer.  Hmmm, in fact your car would look like a 
featureless black blob.  There goes getting a candy apple red car.  :-)

Frank