🚀 go-pugleaf

   >> As a hobbyist electronician I have come across a real problem.
   >> For a certain project, I would need an oscillator with digital,
   >> LOGARITHMIC adjusting (32-bit, 1000 x log) and a HUGE range,
   >> 1 kHz to 100 MHz. Is this at all possible?

In <6560003@hpfcbig.SDE.HP.COM> bame@hpfcbig.SDE.HP.COM (Paul Bame) writes:
  >The incredibly precise logarithmic control may be a real pain - just
  >consider the problem of accurately measuring 1 (log) bit in 32 bits with a
  >frequency counter - you might need an expensive counter with a very long
  >capture time to resolve 1KHz from 1KHz + 1 bit.  You didn't mention how fast
  >this thing is required to change frequency.



Just to consider it from another angle .... 32-bit frequency control requires
what kind of resolution in _TIME_??  There are 2^32 = 4294967296 different
frequencies.  If let "R" stand for the ratio between frequencies, then

   1kHz * (R ^ 4294967296) = 100 MHz,  hence R = 1.00000000321667422079114998.

The uppermost frequency is 100.0000000MHz ; the next lower frequency
is (100MHz / R) = 99.999999678332578955584303 MHz.  The _periods_ of the
waveforms are:

 100.000000000000000000000000 MHz:  period = 10000000.00000000000 femtoseconds
  99.999999678332578955584303 MHz:  period = 10000000.03216674221 femtoseconds

This would be exceedingly difficult to do, and even more difficult to
verify / validate / certify.  For example the timebase must have an
accuracy of better than one part in 4294967296, while quartz crystals
are typically 10 ppm (43000 parts in 4294967296).
-- 
 -- Mark Johnson	
 	MIPS Computer Systems, 930 E. Arques M/S 2-02, Sunnyvale, CA 94086
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