Electro-thermal simulation of an ultra stable quartz oscillator

Ultra Stable quartz Oscillators (USO) which can exhibit relative frequency fluctuations of a few 10(-10) when the ambient temperature ranges from 243 K (-30degreesC) to 343 K (+70degreesC) should all be ovenized to achieve ultimate performance. Such a result needs a very large static thermal gain close to 1000 in the vicinity of the quartz resonator case. Basically, the problem consists in regulating a volume with distributed thermal losses at its edge and internal heat sources whereas just the temperature at one point, the sensor temperature, is known. So, the feedback control system simulation involves a mixture of thermal and electronic functions. To solve this problem we use the electrical analogy for the thermal part. The thermal mesh is still manually done but a unique computer aided software dedicated to electronic circuit simulation will efficiently provide a solution. This choice is discussed and the example of an USO thermal regulator is described as an illustration of this methodology. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.