Microwave-photonic dynamic frequency-swept interferometry for fast ranging

Frequency-swept interferometry (FSI) is intrinsically suitable for static ranging. For dynamic targets, its ranging accuracy is deteriorated by the Doppler phenomenon, and its measurement rate is restricted by the frequency sweep rate (usually kHz level), which prevents the acquisition of accurate time-varying distance details. To solve the problems, a novel microwave-photonic dynamic FSI (MP-DFSI) for fast ranging is proposed in this paper, which uses a single-frequency laser and an electro-optic modulator (EOM) to constitute a dual-sweep laser to provide two ideal mirrored laser sweeps. The instantaneous phases of the MP-DFSI signals are modulated by both the target distance and velocity in measurement, we investigate and model the modulation relationship, present a new data fusion demodulation method for high-accuracy fast ranging, which can effectively eliminate the Doppler error and recover the continuously-varying distance at each sampling point during a whole frequency-sweep cycle. Numerical verifications demonstrate that the measurement rate of the proposed MP-DFSI can reach 10 MHz with 1 μm ranging accuracy, showing the MP-DFSI has the ability of high-accuracy fast-ranging for dynamic targets.