Microwave photonic mixer owns the advantages of wide frequency coverage range and large processing bandwidth. However, the LO spurious of the mixer is still high, which severely limits its application where the LO spurious locate at the band of interest. In this paper, a novel microwave photonic mixer with complete suppression of LO spurious is proposed. A dual-drive mach-zehnder modulator (DD-MZM) is adopted. The LO signal and RF signal are applied to the DD-MZM through the two driven ports. The optical signal is controlled to make the LO signal to be the phase modulation and the IF signal to be the intensity modulated. Finally, after the intensity detection completed by the photodetector, only the IF signal will be preserved and the LO spurious can be all suppressed. A proof-of-concept experiment is performed. Experimental result shows that 50-dB suppression of LO spurious can be realized.
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.
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