Temperature compensation for a disciplined frequency standard

摘要

A disciplined frequency standard includes an adaptive control loop to correct for ambient temperature effects. The crystal resonator of the disciplined frequency standard is enclosed within an oven which is heated by current applied through a resistive heater. A small current sensing resistor is inserted in series between the oven current source and the oven heater to produce a voltage drop which is proportional to oven current. An analog temperature signal T is derived from the voltage drop and is multiplied with a frequency/temperature parameter dF/dT to produce a compound temperature correction factor UT. The frequency/temperature parameter U and an aging drift parameter B are measured in control loops which are weighted by averaging time parameters K, L, respectively. The measured values of B, U are stored and the weighting factors K, L are adjusted according to the variance of the most recent measurement from the stored average. The adjusted values of the correction parameters follow closely and converge to the actual parameters values over a period of time.