4-45
A comparative table for AT and other non-thermal-transient compensated cuts of oscillators would not be meaningful because the dynamic f vs. T effects would generally dominate the static f vs. T effects.
Oven Parameters vs. Stability for SC-cut Oscillator
Assuming Ti - TLTP = 100C
Ti - TLTP =
100C
Oven Offset
(millidegrees)
Oven Cycling Range
(millidegrees)
    10
4 x 10-12
6 x 10-13
2 x 10-13
2 x 10-13
2 x 10-13
    1
4 x 10-13
4 x 10-14
6 x 10-15
2 x 10-15
2 x 10-15
    0.1
4 x 10-14
4 x 10-15
4 x 10-16
6 x 10-17
2 x 10-17
    0.01
4 x 10-15
4 x 10-16
4 x 10-17
4 x 10-18
2 x 10-19
100
10
1
0.1
0
TURNOVER
POINT
OVEN SET POINT
TURNOVER
POINT
OVEN
OFFSET
2D To
OVEN CYCLING RANGE
Typical f vs. T characteristic
for AT and SC-cut resonators
Text Box: Frequency
Frequency
Temperature
OCXO Oven’s Effect on Stability
   The f vs. T stability of an OCXO depends on the static and dynamic f vs. T characteristics of the resonator, the design temperature range of the OCXO, the stability of the oven and of the components in the sustaining circuitry, and the accuracy with which the oven is set to the turnover temperature of the resonator.  The table shows the theoretically achievable f vs. T of an OCXO as functions of oven offset from turnover temperature, and oven stability.  The temperature coefficients of components in the oven and sustaining circuitry make the theoretical values in the table difficult to approach.
   The oven stability depends on the temperature range outside the OCXO and the thermal gain of the oven.  The thermal gain is defined as the external to internal temperature excursion ratio.  For example, if during an external temperature excursion from -40oC to +60oC the temperature inside the oven changes by 0.1oC, the thermal gain is 103.  For precise temperature control, the oven temperature is typically ~15oC above the maximum operating temperature, e.g., in an OCXO designed for -40oC to +60oC operation, the oven temperature is maintained at +75oC.
   The thermal transient effect makes small oven offsets more difficult and time consuming to achieve with AT-cut resonators than with SC-cuts (see “Warmup of AT- and SC-cut Resonators” two pages forward in this chapter for a discussion and illustration of the thermal transient effect).
   Using SC-cut resonators and high thermal gain ovens, OCXO stabilities of ~10-10 over a  -40oC to +75oC temperature range have been achieved.  High thermal gains can be achieved with a single oven, as described in the Walls reference, or, with double ovens (i.e., an oven in an oven).

A. Ballato, and J. R. Vig, "Static and Dynamic Frequency-Temperature Behavior of Singly and Doubly Rotated, Oven-Controlled Quartz Resonators," Proc. 32nd Annual Symposium on Frequency Control, pp. 180-188, 1978, AD-A955718.

F. L. Walls, "Analysis of High Performance Compensated Thermal Enclosures," Proc. 41st Ann. Symp. on Frequency Control, pp. 439-443, 1987.

Warren L. Smith & T. E. Parker, “Precision Oscillators," in E. A. Gerber and A. Ballato, Precision Frequency Control, Vol. 2, pp. 86-88, Academic Press, 1985.

Marvin E. Frerking, “Temperature Conrol and Compensation,” in E. A. Gerber and A. Ballato, Precision Frequency Control, Vol. 2, pp. 99-111, Academic Press, 1985.