August 8, 2015: I have completed the first draft of a board layout. The tag is 34 mm in diameter, and includes the pressure sensor, single stage op amp, and RF microcontroller. I've already built analog sensor tags with this antenna design, so I know it works. I will likely need to fine-tune the frequency to maximize the power transfer when it is built though. I will spend a couple more days refining the design and checking all my error calculations to make sure I am not missing anything. Then I'll probably order one of these in FR4 to prove the concept.