Optical Filter-Less Photonic FMCW Radar for Multi-Target Detection

Frequency modulated continuous wave (FMCW) radar monitors the instantaneous frequency difference between the transmitted and the received signal to determine the time of flight which is proportional to the range. Modern radar system necessitates multispectral sensing to enhance detection capability and anti-jamming efficacy that encourages the evolution from conventional electrical solutions to photonics-enhanced solutions. Photonics offers wide-bandwidth signal generation, parallel processing, and low propagation distortion. Most photonic-assisted radar models are based on optical filters to select the reference and reflected waveform to mix at the photodiode, which limits the system functionality due to the inability to operate in different frequency bands. We propose an optical filter-less photonics-based de-chirp processing of frequency-modulated continuous-wave radar waveforms that overcomes the issue of carrier frequency tunability and agility. A theoretical analysis is performed, followed by simulation, and validated by experiment. The proposed model is experimentally tested for detecting targets at different distances ranging from 150 cm to 210 cm. The system is emulated to detect multiple targets (up to four), showing a range resolution of < 15 cm, and signal processing enables the estimation of the widths of different sizes of the targets.