UltraSonic waves, Phase difference

[Husein06]

Hello,

I'm using a transmitter to transmit 40k square sound waves to 2 receivers on a robot. I want the robot to know which direction the transmitter is and adjust to it (to later drive to it) .

So I'm in the first stages of figuring this out but confused and need help.(correct me if I'm wrong on anything)

To calculate the direction of the transmitter, I will have to know the phase difference between the waves of receiver 1 and 2. But how do I calculate this phase difference? through hardware or software and how?

Moreover, how do I output the calculations of the phase difference (through hardware or software)?

Please advise me if I'm in the right direction.

Thank you

I'm using this kit for transmiter and receiver.
http://www.engineeringshock.com/40khz-ultrasonic-transducer-receiver-kit.html

 

[G4BCH]

To measure the pahse you will need a reference. You could use the output of one of the transducers for this. Add a 90 degrees delay to the output so that you have two outputs in quadrature then mix those with the output of the other transducer. The mixer outputs after filtering will give you two DC outputs. The arctangnet of those voltages gives you the phase difference. Look up IQ phase detector for detailed descrptions on how it works.
This can be implimented in hardware or software, the choice is yours.
Using phase alone may cause problems if the transducers are spaced more than a half wavelength appart. There will be a phase ambiguity to solve anyway and teh further appart the transducers the more rapid the phase changes will be.