I don't understand. Having more points by using smaller phase-shifting steps won't make my beam narrower?
Synthetic apertures start with phased arrays, such as yours, but take data from multiple positions, which are then correlated into virtual focus. If you were to attach your array to a board, butted up against a yardstick fixed to the desk, to keep the direction stable, you could move it sideways in 1cm intervals and collect enough data to do synthetic aperture, without spending a ton of money. 8)
Scanner is 100mm large, so that would do 2/100 radians. Will check up if that matches my simulations.
Thanks for the infos on SAR! Will try doing that!
Guesswork... 40khz ultrasound has a wavelength of about 8mm. If your phase from end to end isn't at least 90 degrees, you don't have enough shift to form a beam with. I would imagine if you're clever, and your transducers don't drop off to fast on the sides, and you've got them fairly tightly constrained in X,Y,Z to a regular grid, you might be able to tweak out more resolution slightly off center, because the return phases will more quickly diverge as this angle increases.