Research on the Automatic Frequency Modulation of Rubidium Frequency Standard

The present status of rubidium atom frequency standard is introduced. The temperature coefficient of traditional Rb clock was mainly made from pump system and variode phase modulation circuit. After filling absorb cell with buffer gas of positive temperature coefficient and adjusting pumping light intensity properly, the temperature coefficient from pump system may be extremely less than that of rubidium frequency standard. Hence, the present temperature coefficient of Rb clock was mainly caused by variode phase modulation circuit. The scheme was pointed out that adopting the automatic frequency modulation to replace origin phase modulation circuit. In the experiment, it was mainly composed of singlechip, programmable time counter and phase lock loop. By properly adjusting the extent of square wave frequency modulation online, the temperature coefficient was not caused by modulation circuit. The performance of rubidium atom frequency standard is greatly improved.