Abstract: In the generation of frequency-modulated interrogation frequencies for atomic frequency standards, the modulation characteristics can be tailored to the frequency discrimination characteristics of a physics package. The rate of phase change of a digital pulse train providing a frequency-modulated component of interrogation frequency for an atomic frequency standard can be varied, for example, by multiplexing a plurality of differently phased (delayed) pulse trains to vary the rate of phase change in a digital interrogation frequency component, or by effecting phase delays and phase advances through the addition and subtraction of pulses of a digital interrogation frequency component.

Abstract: A physics package interrogation signal can be digitally synthesized for use in an atomic frequency standard with one or more sets of integrally-related sub-multiples of a clock frequency in which one of the integrally-related sub-multiple frequencies is varied to provide frequency modulation between integrally-adjacent sub-multiple frequencies through the use of preloadable counters, the controlled delay and the synchronization of digital pulse trains and operation in plural modes. The method and apparatus can reduce false lock possibilities, optimize the ability of the physics package to remain locked, and reduce phase noise in the output of an atomic frequency standard.

Abstract: A heater controller for an atomic frequency standard provides accurate and stable temperature control for an assembly, such as a lamp assembly, by regulating a current flow through a heating device so as to maintain a substantially constant heating power output during start-up and by reducing the DC temperature errors of the system during normal operation. The heater controller includes an integrating amplifier which generates an amplified temperature signal based on the temperature of the lamp assembly. The heater controller further includes a device for receiving the amplified signal from the integrating amplifier and establishing a control voltage having an upper limit based on a voltage of the heater power supply.

Abstract: A resonator package can comprise a microwave container which does not have to be tuned, such as an untuned waveguide, carrying an absorption cell and forming an optical path through its open end and the absorption cell and leading to a light detection means, and a microwave loop adjustably carried by the microwave container between the absorption cell and the light detection means. The microwave loop can be carried by a carrier slidably engaging a slot formed in the waveguide, and can be tuned by adjusting its position with respect to the adjacent face of the absorption cell. The resonator package can thus eliminate a microwave cavity and the need for the precise dimensions of a microwave cavity and the problems of separately tuning a microwave cavity and loop, and can permit smaller resonator assemblies without the use of dielectric loading and the use of a loop that also functions as a very simple and inexpensive microwave multiplier/mixer.