(Goal of R&D is to move technologies toward the upper left)
7-3
* Accuracy vs, size, and accuracy vs. cost have similar relationships
10-12
10-10
10-8
10-6
10-4
Text Box: Accuracy
Accuracy
Text Box: Power (W)
Power (W)
= in production
= developmental
0.01
0.1
1
10
100
0.001
XO
TCXO
OCXO
Rb
Cs
MCXO
TMXO
RbXO
Mini-Rb/Cs
1ms/day
1ms/year
1ms/day
1s/year
1s/day
Clock Accuracy vs. Power Requirement*
   Shown above is the relationship between accuracy and power requirement for the major classes of frequency standards, and for some developmental standards. The accuracies shown are for wide temperature range devices, and include environmental effects and one year of aging.  Laboratory standards, (e.g., the best available cesium standard) have higher accuracies.
   Power availability often limits the available options.  For example, small, handheld devices are limited to XO, TCXO or MCXO.
   The MCXO and RbXO were discussed earlier.  One version of a miniature Cs standard is discussed at “Optically Pumped Cs Standard,” in chapter 6.  Other versions of miniature Rb and Cs standards, e.g., using coherent population trapping (CPT), promise to allow small, low power atomic standards in the future.  The TMXO was the Tactical Miniature Crystal Oscillator, was an experimental <20 cm3, low-power (300 mW @-40oC, vacuum insulated) OCXO.  Similar size OCXOs are now available commercially.


J. Messina, D. Bowman, R. Filler, R. Lindenmuth, V. Rosati, S. Schodowski, “Results Of Long Term Testing Of Tactical Miniature Crystal Oscillators,” Proc. 43rd Annual Symposium on Frequency Control, pp. 47-50, 1989.