Instantaneous frequency measurement technology based on optical sampling

Traditional instantaneous frequency measurement(IFM) technique of high frequency microwave signals is greatly influenced by the analog to digital converter(ADC). A novel method based on optical sampling is proposed. Abandoning the traditional ADC, the high frequency microwave signal is modulated onto the low repetition frequency optical pulse trains using an optical intensity modulator, and thus an optical sampling functionality can be achieved. To improve the frequency resolution of measurement, fast Fourier transform(FFT) and chirp-ztransform(CZT) are used. Then the frequency of the input signal are calculated through the Chinese remainder theorem. Experimental results show that this method can accurately measure the frequency of 39 GHz signal bandwidth.