If you have a super directional antenna on the handheld, you wouldn't have to worry that much about power output on the sensors. If the handheld performs the beaconing as well, then the scattered sensors could be kept in a sleep mode just periodically waking up and looking for a beacon, then transmitting a dotting sequence once the handheld beacon is discovered.
Three dimensional correlation from a single handheld with a stinger-style antenna would still be complex stuff, in an ideal world you would have fixed perimeter sensors, each with a known location to correlate against and determine a fix. You will also need a super high resolution clock on at least each perimeter device, if not each individual sensor. Maybe a GPS chipset on the perimeter, that would get around having to use and keep in sync an RTC on the perimeter. You could probably do some direction finding by examining multipath and other reflected harmonics as well, provided you can disperse the sensors across a wide enough frequency range.
Better yet, don't build evil tracking systems ;)
-----Original Message-----
From: "Times Enemy" <ti..._at_krr.org>
Date: Tuesday, Jan 24, 2006 2:18 pm
Subject: [TSCM-L] Re: RF
Greetings.
Hrm, power may be an issue. 300 meters distance should suffice as a starting point for the first generation.
The product will start in the United States. If the commercial
implementation works well, then it may go beyond the U.S. borders.
The device should be active for no more than 6-8 hours. If the device is not passive, then it's power source needs to either be rechargable,
replaceable, or the entire unit should be so cheap that the whole TX unit can be replaced.
It seems that if it only transmits when asked, then it is most likely a passive unit. The advantages of passive units are smaller size, however, distance is lost with lower powered transmitters. I have yet to determine if it needs to only TX when asked, or not. I read that some passive RFID units can both RX/TX on the same aerial, which requires extra engineering.
I shall answer the other questions, which may help find an answer to this one.
Pulse would save power, which would also allow for a smaller unit.
Maximum size ... well, ideally paper thin and the entire TX unit to weigh under 1 gram. The unit will also have to have other properties which may add to the weight.
The tracking device will be placed on moving objects which will require special properties (probably some type of glue (glue is not heavy also)) in order to stay affixed. It is not initially important that the units be concealed, but because they are small, they may be difficult to visually locate. Also, the operating environment will vary, extremely. This
variance is also a cause for concern, especially when considering the power source.
There are a couple different concepts i have been pondering, regarding DF
(direction finding). What will probably happen is that the basic system will include one handheld unit which will use, yes, signal strength for DF. Later, if the product works, i would like to see a more involved system of three or so units strategically located to allow for a type of triangulation. Then, there is another concept i have which will have the units network with one another and pass various information to each other, which will allow for a mesh-like DF.
Thank you very much for your response(s).
times enemy
> Hi,
> Half a mile will need 80~100 milliWatts
A passive/reflective RFID-style device will not work at that distance
> Tell me where you are...to determine a legal frequency-band (if wanted)
> More details needed:
> How long should the device be active (TX)
Should it only TX when asked (by other TX) that will need a receiver on each as well
Continious or pulses (TX every few sec's ?)
Maximal size
Where is the tag/tracker put (hidden ?)
How will you DF just with signal-strength ?
> Tetrascanner
http://www.tetrascanner.com
http://groups.yahoo.com/group/gsm-scanner
http://groups.yahoo.com/group/traffic-cams
http://groups.yahoo.com/group/iPod-video
http://groups.yahoo.com/group/ICOM-IC-R1500
Received on Sat Mar 02 2024 - 00:57:22 CST