Microwave frequency measurement device is the front-end of electric warfare system. Photo-assisted microwave frequency measurement was extensively studied due to its advantages of large range, strong EMI resistance and low loss. The defect with this method lies in that the half-wave voltage drift of electro-optic modulators would affect the performance of microwave frequency measurement. This paper presents a detailed analysis of measurement performance influence with half-wave voltage drift of all kinds of electro-optic modulators. Theoretical analysis and simulation results show that: half-wave voltage drift of polarization modulator has slight influence of frequency measurement thus is negligible; half-wave voltage drift of intensity modulator produces a reduction in the dynamic range of measurement; for a dual parallel modulator, half-wave voltage drift of the lower arm influences the dynamic range of measurement, and drift of the upper arm causes large measurement error; for a phase shifter, slight drift of half-wave voltage generates obvious errors. Conclusion above has guiding significance for engineering applications of microwave photon frequency measurements.%电子战系统的前端是微波频率测量装置，光辅助法微波频率测量因带宽大、抗电磁干扰能力强、损耗低而被广泛研究。然而该方法使用的电光调制器存在半波电压易漂移的问题，对微波频率测量存在影响。该文详细分析了各种电光调制器半波电压漂移对微波频率测量的性能影响。理论分析和仿真计算结果表明：偏振调制器半波电压漂移对频率测量存在微小的误差，可忽略不计；强度调制器半波电压漂移缩小微波频率测量的动态范围；双平行调制器的下臂半波电压漂移影响微波频率测量的动态范围、上臂半波电压漂移引起较大的微波频率测量误差、移相器半波电压微小的漂移即引起较大测量误差。该结论对微波光子频率测量的工程化应用具有指导意义。
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