Hello!
I'd like to have some hints about what are the rings that can be seen in the example "Steering A Linear Array Example".
What I mean by rings is the fact that the all the circular-propagating waves from each transducer correctly sum up to create a plane-wave, but the ones coming from the extremities of the source line seem to not cancel out.
They are indicated by a red "arrow" in this image: http://i.imgur.com/bvrMLun.png
I've noted that they are independent of transmission angle or aperture size (i.e. always happen at the extremities).
Using a smooth apodization, like the Hanning window, removes this phenomena; but a non-smooth window, like the Tukey window for example, just shifts the rings position to the location of the window discontinuity.
Why is that happening? Is it because kWave is based the Fourier transform and therefore badly handles situations which are non-smooth in space?
Thanks a lot :)