Breaking the Resolution Limitation in Fastsweeping Photonic-Assisted Microwave Frequency Identification

Photonic-assisted microwave frequency identification has been extensively studied for civil and defense applications due to its distinct features, including wide frequency coverage, large instantaneous bandwidth, and immunity to electromagnetic interference. In this paper, we propose and experimentally demonstrate a novel approach for high-resolution and fast-sweeping photonic-assisted microwave frequency identification. In the proposed system, high resolution is realized by using a hybrid optical resonator with an ultrahigh Q-factor. Fast sweep is achieved by continuously repeating the ultrafast chirped signal in a short duration. When the ultrahigh-Q optical resonator is excited by the continuously repeating ultrafast chirped signal, whose frequency is linearly swept across the resonance with a duration shorter than the cavity lifetime, the ringing effect with an oscillating transmission spectrum can be observed. By employing the pulse compression technique, the pulse width of the ringing signal can be compressed, thereby breaking the resolution limitation of the fast-sweeping frequency identification system. An experiment is performed and different types of microwave signals are identified. A microwave frequency identification with a temporal resolution of 4 s and a frequency resolution of 20 MHz is experimentally demonstrated within a measurement range from 2 to 18 GHz.