On a sunny day (11 Feb 2007 10:40:29 -0800) it happened "linnix"
me@linnix.info-for.us> wrote in
1171219229.497140.227210@m58g2000cwm.googlegroups.com>:

Why not? In response to a request, the car transmits the position
every second and the receiver cop can calculate it's speed. The key
to this is a low cost precision gps receiver (accurate to cm). The
heart of this precision receiver is a stable Cesium clock. Sponser my
project and I will show that it can work.

Yes that would work, using GPS,
but in my system the receivers are placed at every road, connected to a
central computer.
If you speed, you will be charged automatically every time.
No cops needed, other then coming to pick you up when your account reaches zero.
I am a bit reluctant to sponsor any of those systems.... freedom and ideas
like that.
Gov is starting to invade in a bad way all over the world.
In Germany now they want to give police the ability to search your PC online
(without your consent, so hacking it)...
Do you trust the police down the road with your banking password?
Where does it end? Brain implant at birth?
Oops, should not have mentioned that.

Paul Hovnanian P.E. wrote:
Fred Bloggs wrote:

[snip]

Your questions were way to open-ended and no one feels like giving you a
treatise on the subject. Go look here:
http://www.copradar.com/preview/content.html


That's a non-technical summary of the subject as far as it goes. Most of
the interesting subjects are greyed out (no links to actual data).


It's good enough for your purposes. There are tens of thousands of
architectures for Doppler radar, but you are interested only in traffic
radar, and within that category, you are only interested in speed radar.
There is no requirement for coherence or even range determination there.
I would expect the simplest radar has no LO

and does simple digital
oversampling of the audio difference frequency, allowing full digital
adjustment of the cutoff frequency high pass filter, set by the operator
in accordance with the speed limit excess to be ticketed.

I would expect
that the FFT is amplitude qualified for maximum range and reports the
maximum speed within that window. It is up to the operator to eyeball
the scene and make the determination of the violator in the event of
multiple targets. Those crummy little roadside signs are turned way down
with a range of only about 50m on an average sedan and report the
maximum measured speed within their window, look to have an update rate
of about 2Hz.

I doubt any of these systems "count" anything

and there
can't be much dynamic range required for head-on RCS variation, I would
expect less than 6dB.

If you need everything explained to you, maybe it's over your head.

Fred Bloggs wrote:
Paul Hovnanian P.E. wrote:
Fred Bloggs wrote:

Your questions were way to open-ended and no one feels like giving you a
treatise on the subject. Go look here:
http://www.copradar.com/preview/content.html

That's a non-technical summary of the subject as far as it goes. Most of
the interesting subjects are greyed out (no links to actual data).

It's good enough for your purposes. There are tens of thousands of
architectures for Doppler radar, but you are interested only in traffic
radar, and within that category, you are only interested in speed radar.
There is no requirement for coherence or even range determination there.
I would expect the simplest radar has no LO

The local oscillator is the transmitted carrier. The I.F. is equal to
the Doppler shift of the reflected signal.

[snip]

When I was in the USAF, I had friends in the "Doppler Radar" department;
one of their components was "the audio amplifier".

Ever since I saw that, I've been wondering what it could possibly
sound like!