Photonic-Assisted Microwave Frequency Measurement Based on Frequency-to-Time and Frequency-to-Power Mapping

A photonic-assisted microwave frequency measurement (MFM) method based on frequency-to-time mapping (FTTM) and frequency-to-power mapping (FTPM) is proposed and experimentally demonstrated. The FTTM is used to perform the MFM in a broadband. Utilizing the results of the coarse measurements with FTTM as a guide, the microwave signal is downconverted into an intermediate frequency (IF) signal to further achieve the fine measurement using the FTPM based on an integrated Fano resonator and feedforward neural network (FNN). In the FTPM, the IF signal is injected into the Fano resonator-based microwave photonic link, where the carrier suppressed-single sideband modulation (CS-SSB) is achieved with the assistance of a dual-parallel Mach-Zehnder modulator (DPMZM), to map the frequency information on the constructed amplitude comparison function (ACF), denoted by the relation between the IF signal and the output splitting ratio (OSR) of the two output ports of the Fano resonator. Thanks to the high slope of the ACF, a high-sensitivity MFM is implemented in the FTPM. The measured frequency is the difference between the local oscillator (LO) frequency and the result of the FTPM. Further, the FNN is used to enhance the MFM accuracy based on the results of the FTPM. In the experiment, ±5.8 MHz and ±0.59 MHz measurement errors are demonstrated before and after the FNN operation within a range from 2 to 20 GHz, corresponding to relative errors of ±0.032% and ±0.003%, respectively.