[time-nuts] question for expert time guys

[Azelio Boriani]

Also the fixed stations can not have OCXO?

On Fri, Feb 1, 2013 at 5:37 AM, Rick Harold <rickharold at gmail.com> wrote:

> To time experts/EE's.
>
> I would like to triangulate a position of a device which moves using 3
> fixed positions devices of known location.
> The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or
> appropriate frequency.
> These two type of devices (fixed and mobile) are all under my control and
> thus customized as needed.
>
> The mobile device (not a phone, custom device) would be the least expensive
> item.  I'd like a range of 150 feet or better and accuracy of 3 feet or
> better.
> When manufactured these items they can be calibrated in order to adjust for
> any variation in IC's, discrete components etc...
> We can assume for now the temperature is constant 70 degree temperature.
> Cost is the key design factor.
>
> The general flow is:
>
>    1. base station 1 indicates we are determining position of device A.
>    2. Each base station 1, 2, 3 take turns pinging the device to determine
> distance.
>    3. A ping consists of (something like, e.g. frequencies as examples)
>         -send 915mhz signal from base station to device
>         -device response ASAP on different frequency
>         -station waits and counts 'time' for return
>         -this is repeated N? times to get best avg/accuracy.
>         -The mobile device does not move very fast
>    4. Since delays of the process on each unit is calibrated the device and
> base station would subtrack that time out from the results.
>    5. obviously with 3 distances we can determine the 2D position of the
> mobile device
>
> I know the time accuracy is the key to count time =  feet, 1ns.  This
> overall project is not new concept.   How to make it "inexpensive" is key.
> how inexpensive, very ;-)   no OCXO or expensive components like that.
>
> That's my goal, and I'm looking for help on the design/thought process of
> getting there.
> I am open to a consulting arrangement for a fee, please email if you like.
>  I've worked with 'regular' EE's (I'm a software guy) but this time
> accuracy is too much for them.
> Esp. finding a way to do it inexpensively.
>
> Thanks for any thoughts.
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