Temperature Control for Hydrogen Maser Frequency Standards

摘要

Hydrogen masers with excellent long-term frequency stability are now used for frequency standards. In recent years, a lot of research and development of compact H-masers has been done at the Beijing Institute of Radio Metrology and Measurement. The long-term frequency stability and temperature coefficient of frequency are greatly affected by the temperature stability of the interior cavity. Therefore, one must pay attention to the interior cavity temperature control system in the development of compact H-masers. In this paper we will discuss and stress the following points: (1) There are two representative methods in cavity frequency control. The first method is a combination of cavity temperature control and cavity frequency servo. The second method is the above, combined with total temperature compensation. (2)The partial temperature compensation is used with cavity temperature control and cavity frequency servo in this method. The method of partial temperature compensation has a short time delay, and can reduce the effect of the temperature gradient. By using high-stability temperature sensors and multilayer, multipoint temperature controls, the temperature control accuracy can increase. In our H-masers, accurate decimal frequency synthesizers, high- velocity and high-isolation switches, low-noise up-frequency converters, and high-stability automatic frequency control systems have been developed. Hence, the achieved accuracy of the cavity frequency servo is better than 1 Hz. (3)Since the above method was adopted, the performance of compact H-masers has greatly improved in the laboratory.