Abstract: The radiofrequency circuit of traditional miniature rubidium atomic frequency standard (RAFS) uses saturated output, which can stabilize the amplitude, but not the waveform, of the radiofrequency signal. This would lead to insufficient microwave power stability. In this study, an improved circuit for stabilizing power amplitude in miniature rubidium atomic frequency standard was described. The circuit took the bias voltage of step recovery diode (SRD) as a reference to achieve automatic gain control (AGC) through controlling the gain of the variable gain amplifier (VGA). This scheme controlled both the amplitude and the waveform of the radiofrequency signal. The results showed that this scheme can effectively improve power stability of the microwave signal in miniature rubidium atomic frequency standard.

Key words: rubidium atomic frequency standard (RAFS), power amplitude stability, variable gain amplifier (VGA), step recovery diode (SRD), automatic gain control (AGC)