Broadband photonic instantaneous frequency measurement using a low-power hybrid plasmonic Bragg grating

A novel approach, to the best of our knowledge, for instantaneous microwave frequency measurement is proposed. This method utilizes an integrated hybrid plasmonic waveguide Bragg grating (HP-WBG) in a microwave photonic (MWP) system. The HP-WBG, only 34 µm in length, operates in both transmission and reflection modes, producing two distinct optical outputs that form the amplitude comparison function (ACF). The foundational concept of the proposed instantaneous frequency measurement (IFM) relies on a linear-optics frequency discriminator. Launching a single sideband with carrier (SSB+C)-modulated optical signal into the HP-WBG results in a monotonic ACF, which is independent of the amplitudes of both the optical and microwave signals, and enables the translation of the microwave frequency into an optical power ratio. In this technique, the frequency of an unknown microwave signal is estimated according to a specific relationship between the ratio of two optical power functions and the unknown microwave frequency.