From: Jim Richardson
Subject: Re: Radar basics?
Date: Sat, 19 Oct 2002 20:01:46 -0700
Organization: Erisian claw
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On Sat, 19 Oct 2002 03:44:25 -0500,
Dave VanHorn wrote:
>> Hi, it is possible to use radar to do this, they were popular in the
>> 70's before PIR detectors were available, they work by detecting the
>> doppler shift of the microwave return signal.
> That's not "radar" either. It's a homodyne doppler unit.
> This is the directional version of the field disturbance sensor.
> Radar uses a very high power pulsed transmitter, and a directional antenna,
> to detect reflections.
> It gets direction and distance information by measuring antenna angle and
> time of flight.
> Homodyne dopplers don't know distance, and if you rotate the antenna, they
> will tell you they are seeing motion, because effectively, you're moving the
> world. :)
Sounds like a limited RADAR system...
It tells you that a target is in range, and in the target zone. By
sensing the reflections of the Tx pulse, off of the target. There is no
power requirement in the definitions I have ever seen of RADAR. Nor are
all powerfull radar systems pulsed. CW doppler RADAR exists also.)
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