A microwave exciter for Cs frequency standards based on a sapphire-loaded cavity oscillator

A low noise and highly stable microwave exciter system has been built for Cs atomic frequency standards using a tunable sapphire-loaded cavity oscillator (SLCO), which works at room temperature. This paper discusses the successful implementation of a control system for locking the SLCO to a long-term reference signal and reports an upper limit of the achieved frequency tracking error 6/spl times/10/sup -15/ at /spl tau/=1 s.