提出一种多级高精度可调谐的瞬时频率测量(IFM)方法，采用单光源无滤波的IFM 系统结构，结合光偏振调制和偏振分束原理，利用偏振调制器和偏振控制器等器件来实现对同一波长下不同光偏振维度上微波信号的加载和分离。通过控制单模光纤的色散参数，可以获得较大的测量范围，利用色散所致的射频功率衰落效应，能获得单调变化的频率—幅度映射关系，进一步通过光电探测的射频信号输出功率比来得到幅度比较函数fACF。由于fACF 可以通过改变偏振角或直流偏置电压进行调节，因此该测量方法可用于多级频率测量实现对特定频率的高精度检测。结果表明，可以获得2~17.3 GHz的测量范围和±0.15 GHz的测量精度。

A multi-step approach for instantaneous frequency measurement (IFM) with high resolution and tunable range is proposed. A single laser source and filter-less architecture are employed too. The principle of optical polarization modulation and polarization beam splitter are combined long with a polarization modulator and polarization controllers to implement the process of loading and separating the microwave signal with identical wavelength but different polarization dimensions. By controlling the dispersion parameter of single mode fiber, a wide measurement range is achieved. Taking advantage of the dispersion- induced power fading effect, a monotonically decreasing fACF can be obtained by calculating the ratio of the microwave power via the photodiodes. Besides, by adjusting polarization angle or bias voltage, this approach can be applied to multi- step frequency measurement, thus it will lead to high measurement resolution for specific frequency. A frequency measurement range of 2~17.3 GHz with a measurement resolution of ±0.15 GHz is obtained.