40kHz positioning system

[raducrv]

Hello,

I need help regarding the system for positioning I have attached .

I want to use 40kH trcv and receivers and I have some unclarities :

How to distinguish between the 2 transmitters I have inside the triangle (the 3 receivers )

How to calculate the distance from each transmitter to the receivers , time of flight or power level of the signal ?

Thank you in advance!

https://obrazki.elektroda.pl/9348074100_1416060752.jpg

 

[FvM]

You didn't mention it, but the question makes only sense if you are talking about ultrasonic time-of-flight measurement.

For an unequivocal tof-measurement, the transmitters must be pulsed, to allow an identification, they must use unique signal characteristics, e.g. different pulse patterns. You need also to take care that both transmitters are not sending at the same time, either by using a respective low duty cycle or some kind of synchronisation.

 

[D.A.(Tony)Stewart]

Review basic theory first on Ultrasonic Interferometry

**broken link removed**

**broken link removed** Ultrasonic Transceiver chip

However for accuracy both transmitters may need to be GPS clock synchronized or very stable << 1ppm Clock.

 

[raducrv]

The ideea is that the transmitters are not synchronized because they can start sending messages independent from each other .

what do you mean by unique signal characteristics ? How can this signal be coded ?

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The ideea is that the transmitters are not synchronized because they can start sending messages independent from each other .

what do you mean by unique signal characteristics ? How can this signal be coded ?

 

[FvM]

what do you mean by unique signal characteristics ? How can this signal be coded ?

Any distinguishable characteristic, e.g. different burst length.

 

[D.A.(Tony)Stewart]

Position is the medium velocity ( air pressure in this case) times time interval difference comparing each Rx to a common source, such as GPS time in microseconds. Channel variation in speed due to temperature , %RH and the transmitter filter group delay variation all contribute to error. All Rx must use a common time ref and the Tx must use a sync pattern that is compared with each Rx to determine a vector position from the centroid of the Rx array. Ricean and Rayleigh fading interference will be the biggest problem.