Just looking into some full wave rectification without diodes and I have so far found 2 ways. One with 2 op amps, quite costly, or one promising one with just a transistor:

I do like the look of this, might be right up my street. It does look slightly jubious, but its worth a try. If not, I might have to settle for the opamp rectifier.
Also found this, another opamp full wave rectifier but with the possibility of only 1 op amp. Even if it doesnt, it still uses less parts than the first.
Found one last one, much like the prebvious, but has some programmable gain on it.

I found this that is essentially what I thought of the other day, bastards, always knick my ideas (One must admit that they had the idea months ago :D). I personally think that mine would be better though, because it looks like they are using modulated IR face up to detect when someone goes near it. Also, the pulse effect is shit. This means that 1, it looks shit, and 2 it only works with glass tables. How much more cool would it look with mine on a slightly opaque white/black/something table. And being controlled either by a small PIC (of course!) or directly with a few op amp tricks, would look loads better. More natural.

Would be a lot of work though. Would have to get the EFPD smaller/cheaper.  Will definatly have to continue development, (even if my project guy does something), and maybe get a few built externally.  Depends how complicated the circuit is.

Ive recently been playing with a new analytical solution to the multilateration problem, but its complicated and I dont fully understand the maths behind it yet because it was Kevin’s work, not mine.  Ive been implementing it into the disdrometer simulation software but results are poor so far.  The largest problem is that the principle error checking and selecting technique is to see if the proposed drop occured inside the tank area.  When many pulses exist in time, the chances are very high that some combination(s) would be inside that area.  So because of this lack of resolution, I cannot include that result in the hit statistics, hence the resulting accuracy is low (typically < 50% at 10mm/h).

I have added some more tests, like quadrant analysis to make sure that the results are in the correct quadrant, not only in the tank and I have also another idea to ultimatly produce an error variable.  [Like the fminsearch routines before that picked the combination with the lowest error even if there were more than 1 possible combination].  This would perform a reverse multilateration algorithm to recalculate what the pulse positions really should be if that position is correct.  The only problem is that this is using the inaccuracy of the analytical method.  Strictly speaking it should use the error of the true vs. suspected data.

Finally, as always (and typically the case), it could be because of a bug in the code.  I’m struggling for focus/motivation at the moment and I’m busy this weekend.  I dont think I will have my car on monday so I will have to get emma to take me into uni in the morning.  A whole day (minus labs) in my office with no distractions should do the trick.  Off for a break now..

Just been doing some bored research again, and I came accross this image:

This would be a good route to investigate when I do get it up and running. I Could initially scan for objects, then focus in using this technique. First seen here but there must be other sources out there. Hence, once some beam steering has been accomplished, it would be good to upgrade it to focused beam steering. Cool!