[Gb-ccb] phase switch rates / samp_per_state

[Brian Mason]

hi Martin, Tim- I'm reviewing documentation in preparation to get Michael
Lacasse working on the CCB manager (heads up: we might have a few
questions about the simulator later on).  I believe the two most
significant changes to the CCB software interface resulting from the
faster ADC sampling, as Tim & I corresponded about around 13aug03, are a)
samp_per_state now must support larger values; & b) there is no analog
blanking dt.

I thought it worth reminding ourselves again of 3mm vs 1cm as regards the
values of samp_per_state which need to be accomadated.  In particular, 1cm
will switch at "10 kHz" with 2 switches which means one complete phase
switch cycle every 100 usec (equals a relative phase change every 25 usec;  
equals an individual switch toggling every 50 usec).  The 3mm switches are
not guaranteed to toggle faster than every 100 usec; since there is only
one switch, this implies a maximum switch rate of "5 kHz" (equals a
relative phase change every 100 usec; equals the switch toggling every 100
usec).

Assuming 100 nsec samples I then derive the following constraints

minimum allowed value of samples_per_state <= 250
   (because we must be able to switch at least as fast as "10 kHz" w/Ka)
maximum allowed value of samples_per_state >= 1000
   (because we must be able to switch at least as slowly as "5 kHz" w/W)

As previously discussed the slowness criterion is not absolutely optimal
from the 1/f point of view but is imposed by available hardware at W band.

Do you agree with this, and if so, is 250 -> 1000 a good baseline to
assume for the legal range of values? Previously the maximum allowed value
for samples_per_state was tied to the number of switching phase switches
Nsw, and do we expect that to be the case now also? Also will the number
of measurements per state still be automatically set at 2^Nsw?

 thanks,
  Brian
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