Hi, Trying to track things in 3D by radio seems like a fairly simple idea but in reality gets complicated pretty fast. To be honest I wouldn`t even think about trying to design a system yourself unless you have extensive RF engineering knowledge. Fortunately however tracking things in 3D is a pretty common problem and there are some off the shelf systems available. However to meet your spec`s exactly it`s gonna cost ya! 1.) An 802.11 signal strength location system get`s accuracy of about 2m indoors and say 100m range with update rates of maybe 10-20 times a second. There are various company`s marketing these solutions, can`t remember names tho. (V V cheap) 2.) Custom conventional radio location systems ala http://www.wherenet.com/ (V V expensive) tho this won`t give you the accuracy or update rate you require. 3.) GPS, won`t give you update rates or accuracy you require + only works outdoors. 4.) Ultra Wideband RTLS, there are a few companys working on this at the minute, there are some systems in various development stages. Expect to see the first realistic commercial stuff in the next couple of years. When available will do pretty much everything you want. Take a look at http://www.aetherwire.com/ and http://www.ubisense.net/ for further info. However what exactly is the application? If you have line of sight I would be very tempted to go with a vision based system. This would also be primarily a software project + lots of freeley available information. Also you could probably get an active beacon ultrasonic system working over 50m without too much trouble. With temp/pressure compensation it shouldn`t be too difficult to get 1cm accuracy. Hope this helps, Best regards, Andrew Seddon Marcel van Lieshout wrote: > > I believed my question was detailed enough, but I now do agree with > you. > > I am trying to figure out if it is feasible to design a local > positioning system (3D). > Because I cannot set/measure the clock on the transmitter, I thought I best use the TDOA principle. > I would therefore like to measure time of flight differences with an accuracy of as little mm as possible > (max 10 mm). > The RF frequency is 2.4 Ghz > The maximum distance is 50 mtrs. > A single transmitter at a time is active > At least four receivers are present > RealTime results are needed > Several thousand (2500) measurements per second are needed. The acual > location calculations are no problem, just a metter of enough cpu-cycles ;-) > > As I am basically a software-guy, I am not sure what information is relevant. Please, keep asking. > > Thank you for thinking with me! > > Marcel > > Robert Rolf wrote: > > Over what distance range? At what carrier frequency? > > Phase difference measurement can get you there as can various forms > > of interferometry if the signal is CW. > > > > Look at how geodetic GPS can get down to mm with relatively cheap silicon. > > > > Does the result have to be supplied in real time? > > > > The CORRECT way to access the list's knowledge is to pose the full > > problem so that our replies fit your constraints. > > > > Robert > > > > Marcel van Lieshout wrote: > >> I'm trying to measures RF time-of-flight up to a few mm accuracy ( > >> 10mm would be fine, 1 mm > >> would be fantastic). Well, because I have no influence on the transmitter, I actually want to > >> measure Time-Differences-Of-Arrival at several receivers. > >> > >> What do you (or anybody else) think? > >> > >> Marcel > >> > >> Jinx wrote: > >>>> Hmm, not fast enough. Looking for something in the low > >>>> picoseconds switching times :-0 > >>> > >>> ECL 100K is probably the fastest readily-available family, and > >>> 25GHz > >>> (40ps) operation is the exception rather than the norm > >>> > >>> Googling around, it appears anything over that is very > >>> specialised, not > >>> what you'd call a "family". Logic at up to 350GHz (2.8ps) appears > >>> to be > >>> possible but in the experimental domain > >>> > >>> ;-) > >>> > >>> Do you actually need ps speed, or is there a way that what you're trying > >>> do can be done by inference ? For example, in the way that high > >>> speed oscilloscopes sample to build a waveform ? Can you improve > >>> what you have or can get with liquid nitrogen for example ? > >>> > >>> > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! email > listserv@mitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu