This is the actual PCB we designed for the circular phased array prototype:

The shop ran out of single sockets, so we weren't able to finish the fourth ring, but in the meantime, we can still test the board with 3 phase shifted rings.

This is the board with 3 rings filled in and with inductors selected to match the capacitance of each ring to get a 40 kHz resonance for the whole board.

Fun little test video