I'm looking for a new project and phased array antennas have always intriqued
me. RF is a bit of a black art for me so I'm thinking about playing with sound
instead. I have no idea what I'm going to make, this is still in the thinking
stage. Maybe a locater beacon/tracker for model rockets.

I understand the basics of phased arrays, but I'm not too clear on the details.
Both google and amazon have lots of info on RF arrays, how much of that is
applicable for sound? Since both sound and EM radiation are waves I would expect
to find a lot of similarities. Some of the RF books on amazon are a bit
expensive, and I'd hate to spend a lot of money on a book shelf ornament. Any
recommendations?

I did a quick Digikey search for microphones and everything that came up was
limited to audible frequencies (<20kHz). Where do I find a good source of high
frequency microphones/speakers?

What frequency range should I be looking at? I have pets so I'd like to go high
enough to avoid annoying them if possible. Any idea what range medical
ultrasound devices use?

I imagine I'm going to need some high speed ADC's. I've looked over the
corresponding parts from TI and Maxim (any other manufacturers I should look
at?) and there's a wide variety to choose from. What are ECL interface levels?
I've never designed a digital circuit over 20MHz, any gotchas that I need to
know about?

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