I have implemented a new microcontroller that has simultaneous sampling and a slightly higher sampling rate. I could then interpolate the data with pretty good results using a simple padding + band pass filtering technique. The higher the SNR the better it worked.
However, I have hit a great big wall. It all boils down to the fact that I have used 2 rows of transducers to make the spacing 1 wavelength.
For the following results, Consider the situation where x is the horizontal plane, y is the vertical plane and z is the distance between the source and the target. If the target is slightly elevated in the y plane, the top and bottommost transducers would receive an echo at different times. Furthermore, due to multipath dispersion I am also receiving further echoes from different y directions. So to counteract this, I would have to scan not only in the x plane, but in the y plane too, and this was accomplished by summing all of the results in the y direction to produce a plot of the targets in the x plane. However, by delaying the signals in the y plane, the x plane in some situations became erroneous. It looks like I am getting some sort of aliasing in the x plane. I think that this is because of instead of having a beam pattern from 4 transducers, I am getting 2 x 2 transducer patterns, so not only do I now have a very very wide beam width, I will have some nasty sidelobes too (since if you just consider the 2 transducers, the spacing is 2 x wavelength.)
On the up side, the hardware works great!
So all around, this was pretty much a disaster, and I am not looking forward to remaking all of the hardware. So for beta 2 I will need:
The hardest thing I see is sourcing the peizoceramics from somewhere. Does anyone know of where I can get any cheaply online? Self enclosed transducers would be ideal, but I would be willing to mess with the naked ceramics myself if I had too…
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