As far as I know I've just drawn it! :lol:

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ok thanks for all inputs,

yes Nigel it works and i think the best postion is when i get a sine wave with highest amplitude(i have triangle waves mostly and it becomes a sine wave with highest amplitude at a specific freq)
my small piezo has a resonance freq at 29kHz(i wish i could get a FLAT resonance for it to 40kHz!?

Nigel, what did you mean with parallel and serial resonance in transmitter and receiver?

 

The transmitter becomes a low impedance and ABSORBS power at it's resonant frequency, as required for maximum output, the receiver becomes a high impedance at it's resonant frequency, so lets the signal through, rejecting higher or lower ones.

So for the transmitter you adjust for MINIMUM signal at resonance, and for MAXIMUM signal on the receiver.

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Nigel,
you have showed a pic to measure the resonance freq,
i want to know if it is possible using it to find out the bandwith of a transducer?
i saw a data sheet about an ultrasonic transducer that is able to work with 10kHz of bandwith,
is it possible to measure its bandwith with that circuit?

i think the conical of an ultrasonic sensor is "the most important" part that makes the piezo to has a resonance at a specific freq(i mean if you cut part of conical the the freq range will be changed) am i right?
if so then how that ultrasonic sensor is able to work at a flat freq of 10kHz??

here is the link:
http://www.prowave.com.tw/english/pr...e/400wb160.htm

 

Yes, I don't see why not, just plot the amplitude for a range of frequencies and draw a graph from them. Bear in mind, the Q will be a LOT lower for 10KHz bandwidth, so the tuning won't be anywhere near as pronounced, and you will probably need a LOT more gain to make up the difference!.

Presumably this is still about your audio over ultrasonic project?, 10KHz bandwidth from the transducer should just about give you a low quality voice channel!.

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PIC programmer software, and PIC Tutorials at:
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can you explain more about Q factor part for these ultrasonic transducers?

yes this is about my experiment with ultrasonic and modulation,
anyway i have no access to that kind of wideband ultrasonics
but if there was a way to solve the problem with the receiver part and use SSB then 10kHz is ok.

i have alot of peizo ceramics(resonance freq is near 28kHz) do you think it is possible changing their resonance freq usinf a conical?

 

'Q' is the magnification factor - a bit like hitting a bell, you hit the bell and it rings at a specific frequency - and because of that it's very loud. If the bell was somehow modified to ring at a range of frequencies it wouldn't be anywhere near as loud, because the magnification factor (Q) would be a great deal lower.

Do you have the electronics working yet?.

No idea, but I wouldn't have thought so?.

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PIC programmer software, and PIC Tutorials at:
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yes i want to start and work on it again,
it is amusing.(i am a stubborn person lol)

 

You're not very clear?, does your project work connecting (via wires) the transmitter section to the receiver section?. This removes any problems about bandwidth over the wireless link - if this doesn't work?, you're totally wasting your time before you start.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

The piezo vibrates at its cut freq. like any crystal.

 

You can tune the output to one of the crystals harmonics but of course the amplitude will be lower. Build a Pi filter tuned to the harmonic you require.