Research progress on precision self-sensing of frequency standards

The phenomenon of self - sensing is a physical phenomenon shared by various frequency standards. It is a change in the internal phase of a device that occurs without external reference standards due to its own factors or external influences. This type of sensing signal has a direct or indirect similar or identical variation pattern compared to the output frequency of the device itself. For a crystal oscillator, the output frequency is its result, while the phase change at both ends of the resonator represented by the resonant parameters represents the essence of the oscillator frequency variation. The phase shift at both ends of the crystal resonator reflects the sensing characteristics of the oscillation frequency, which can remember and maintain the nominal accurate frequency of the oscillator, and indicate its frequency error, such as temperature, aging, acceleration, shock, vibration, and electromagnetic radiation and so on. The temperature compensation and aging drift compensation based on self-sensing of resonance parameters will greatly exceed the accuracy of traditional frequency stabilization methods. By using an atomic clock as a standard in preliminary experiments, the phase difference of the resonator when the oscillator is calibrated - the "reference phase difference" - can be used to remember the accurate frequency. For the endpoints of a wide range of frequency standards, the phase differences to be collected include the resonant parameters of the crystal resonator, load capacitance, circuit influence, and the control effect of atomic level transitions.