I conducted a patent search on Applied Materials Inc (patent assignee of Steve's device) and came across thousands of patents. After filtering with keywords there was one that stuck out of all the results.

Use of variable RF generator to control coil voltage distribution #6,345,588

"an RF generator coupled to said impedance matching circuit, said generator generating an RF signal having a cyclically variable frequency which shifts between at least three frequencies in each cycle for time-averaging voltage distributions along said coil. "
Source: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.htm&r=32&f=G&l=50&d=PTXT&p=1&p=1&S1=((%22Applied+Materials,+Inc%22.ASNM.)+AND+RF.TI.)&OS=AN/%22Applied+Materials,+Inc%22+AND+TTL/RF&RS=(AN/%22Applied+Materials,+Inc%22+AND+TTL/RF)

Full patent is attached.

Hi Simon
   This is another piece to the patent that has been brought up before. It is for growing or etching semiconductors. Really has nothing to do with the TPU. On the other hand, the "idea" here may well be of credence and well worth a look at. Three seperate frequency setups and a way to tune it. Hmmmmm........

sugra

According to the patent experts it is common practice to break your device up into parts, hiding the pertinant information across multiple patents that seemingly have nothing to do with the end product.

There is that other plasma focused patent that seems to have a coil configuration that matches some of the tpu's in the videos.

This quote that you have brought up simonmagus, sounds exactly like the TPU controller. I wonder how many pieces of the puzzle there is to find?