[time-nuts] sand9 TCMO

[Jim Lux]

On 1/6/14 6:05 AM, Magnus Danielson wrote:

> MEMS might be good for certain tasks, but for closer in noise I've only
> seen some progress recently, but not measured it myself. Close-in noise
> seems to have been pretty bad for all MEMS so far.
>

I think that's probably related to the physically small size. It's hard 
to get a high Q in something that's smaller than a gnat's eyelash.

I wonder if someone has done some sort of fundamental analysis, like 
there is for antennas that establishes a "laws of physics" limit on how 
good it can possibly be for a given size or mass.  For antennas, there's 
the Chu or Chu-Harrington limit that says there's a tradeoff between 
directivity, stored energy and physical size.  A high directivity, small 
antenna will have a lot of stored energy, which in practice means low 
efficiency.

For instance, at some point, the resonator is so small that the amount 
of energy in it is comparable to the thermal noise, so if it's uncooled, 
that sets a floor on best performance.


  It's a quick way to stop those entrepreneurs who know just enough to 
be dangerous when they say that they're going to make 1 degree wide 
beams with something the size of a cellphone.  You know, the companies 
that have one or two folks in engineering and 35 in investor relations. 
  They often combine their "not realizable in real world" antenna with a 
"new form of modulation and coding that provides 10x performance over 
best methods today".