Atomic Frequency Technology Research The Subject Of Circuit Design And Low Phase Noise

Atomic frequency standard is a frequency source that with excellent frequency stability and accuracy, which has been widely used in satellite positioning & navigation, time keeping & dissemination, communication, instrumentation, astronomy and other area. Rubidium atomic frequency standard (RAFS) is in most wildly used at present, for its advantages such as smaller size, lighter weight, lower power consumption and lower cost.Basic theory of RAFS was studied base on the rubidium physics package we have. The circuits of RAFS were designed, which locked the voltage control crystal quartz oscillator (VCXO) according to frequency of rubidium atomic energy level transition, thus the accuracy and stability of output was in accordance with atomic energy level transition. The noise of each part contributes to the output was researched; hence methods of improving phase noise were presented. The main contents are as follows:1. Basic quantum principle, optical pumping and optical detection principle of RAFS were investigated, and control process of servo loop has also been described.2. After the functions of components in servo loop were analyzed, the main circuits of RAFS were designed. The design of main circuits included simulation and practical circuits designing. The main circuits included servo circuit,VCXO,frequncy multiplier, synthesizer and frequency modulation circuit. Servo circuit was used to process weak error signal. VCXO was used to correct error frequency and supplied output. Frequncy multiplier and synthesizer were used to multiply and synthesize the frequency.3. Impact of components'noise on output was researched, result shown that the phase noise of RAFS was dependent on VCXO's. Methods of optimizing phase noise of VCXO were presented so as to improve phase noise of standard output of RAFS.Standard output of RAFS was 10MHz, and the measurement of phase noise was -125dBc/Hz@100Hz.