基于调制转移光谱、吸收鉴频和色散鉴频技术的应用，根据被动型氢原子钟的工作原理，对单频调制的微波探测信号的氢原子跃迁鉴频和微波腔谐振鉴频过程进行了详细的理论分析和数学推导。在此基础上仿真得到了鉴频曲线与不同调制深度对应的误差信号幅值的关系，并与实验测试结果进行对比分析，验证了被动型氢原子钟单频调制的调制解调原理的推导过程，得到了使被动型氢原子钟短期稳定度最好的调制深度；上述分析过程为被动型氢原子钟单频调制技术提供了性能优化的理论基础和依据，为电路方案改进提供了设计原理。

We present the mechanism of coherent population trapping (CPT) atom clock. The optical system is designed for a portable CPT atom clock. In this system, single transverse mode vertical-cavity surface-emitting laser is used as a miniature pump laser. The driven circuit is designed based on a field-programmable gate array full digital control system and special-purpose chip MAX1968. The experimental results show that the optical system can provide circularly polarized light, and has small volume and low power consumption. These indi-cate that the optical system is a promising candidate for a portable CPT atom clock engineering prototype.