On Feb 14, 2008, at 12:12 PM, Al Shinn wrote:
>
> MIR =?  mid IR  ??  as in PIR?

Micropower Impulse Radar.  Something developed at LLNR:
  https://ipo.llnl.gov/technology/profile/sensor/ 
MicropowerImpulseRadar/index.php

"MIR uses $10 of off-the-shelf components to outperform conventional  
radar and sensor equipment costing as much as $40,000. Both the radar  
transmitter and receiver are contained in a package measuring just  
two square inches"

You have to license the technology from LLNL; they've apparently been  
real successful at keeping the wraps on just how it works; I've never  
seen anyone post a hobbyist version that works with sounds or  
anything.  I gather that you transmit a pulse of radio waves, wait  
DELAY microseconds and see if the pulse shows up on your receiver.   
Then you sweep the value of DELAY until you do get a result.  The  
idea being that it's easier to create very short delays and  
measurement windows (of known value) than it is to MEASURE very short  
delays.  Or something like that.  (They have an "overview" document  
now that pretty much matches this description.  I feel good!)

BillW

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